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TF42, Our Engine Project For The Airliners-200  
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Posted (1 year 2 months 2 weeks 17 hours ago) and read 8588 times:

   Dear colleagues,   

this is a mail to let you know that our sister department, Airliners.net airframes have secured funding    (from a middle east consortium    ) for our Airliners-200 single aisle airliner    . While they had planned to use available engines (the GTF and Leap class) the market requirements have now forced the project into making a new engine in the 40 klbf class. As our airframe colleagues have not been able to convince    any of the established OEMs to produce a suitable engine they have now turned to us, Airlines.nets engine department, to conceptualize, design and certify a suitable engine    . The parts will later be contract produced by established tier one suppliers and we will final assembly the engine in our MRO facility in Key West Florida    .

The airframe specs are :



As can be seen they are already short on range, the interested airlines want a Transcon, TATL range with margins for unfavorable winds.

The engine requirements they ended up with are (before they ask us to fix their problem  Wow!   )




As our latest engine design goes back to the 1980:ies one must admit that we are in general a bit rusty    (even though we have discussed a lot  ). I have therefore secured some consultancy from industry experts that will come in and help us as we go. The idea is to start the design phase with a classical 2 spool turbofan employing established methods (and learn what is going on ) and see if we can fulfill the spec our airframe team put forward. We will then explore more advanced techniques (like ceramics, gearboxes, 3 spool) to see if this can gets us a better engine as the airframers will certainly run into weight problems (they already have) and ask for more thrust and lower TSFC (they already do) !   


To help with the process we will start with everyone putting forward books, articles etc that are useful for the department refresh  . I will also present our engine design tool that we purchased from the well known company GasTurb software from Dachau Germany.

So dear colleagues we have got a real challenge on our hands    ,

let's get out of those armchairs    and kick some    ,


I count on your participation in this very important project   

your engine department mgr "Ferpe"   

[Edited 2013-02-02 14:28:36]


Non French in France
84 replies: All unread, showing first 25:
 
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 1, posted (1 year 2 months 2 weeks 16 hours ago) and read 8573 times:

Dear collegues, could some cabin experts check the airframe departments ideas about number of seats? I have no ideas about seating etc but we don't want a late surprise that the frame will take even more pax+bags then they say so that payload-range problems we are already in will be even worse  Wow! . We need to know if we shall size the base engine larger then they say already from the beginning    .


Non French in France
User currently offlineLH707330 From United States of America, joined Jun 2012, 593 posts, RR: 0
Reply 2, posted (1 year 2 months 2 weeks 13 hours ago) and read 8496 times:

Ha ha love this! I've always been saying we need a medium-haul 200 seater with overpowered engines....

User currently offlineKC135Hydraulics From United States of America, joined Nov 2012, 270 posts, RR: 0
Reply 3, posted (1 year 2 months 2 weeks 12 hours ago) and read 8493 times:

Sounds suspiciously like a 757.

User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 4, posted (1 year 2 months 2 weeks 7 hours ago) and read 8422 times:

Quoting KC135Hydraulics (Reply 3):
Sounds suspiciously like a 757.

Sure, that is why there is a market and no engine  . More fun to invent an engine together that is not available, also less sensitive to discuss for the experts we have on the forum    . But everyone can contribute, no input is off the mark, this is the chance for us all to learn something about those elusive engines.

As Tom said said when I contacted him, "engines are a black art", time to put a torch into it or a    at least  . Re 757, what about the spec, good enough for this market niche? The airframes department says it will be Al-Li fuselage with CFRP wings.

Re the engine requirements, I have calculated these using my frame model, the values should be good enough to use for an engine design me thinks. The fuel consumption around 0.54 is todays state of the art ie 787 generation so should be doable but as we can see the frame guys already is screaming for more so those advanced discussions have to come. But first we all learn while doing a vanilla first try.


Here some hints where we all can dust of our engine knowledge:

- General and good write-up: Rolls Royce, The Jet engine, you can find it online. The chapter 21 performance is good reading, the formulas are ok but use old units (mm Hg for pressure for instance) therefore check Wikipedia for modern ones http://en.wikiversity.org/wiki/Jet_engine_performance. Don't worry about all those formulas, we will have a software that does all the calculations, see below, it is good to be able to look up a formula to understand en large what factors are involved however.

- A good summary http://en.wikipedia.org/wiki/Turbofans and this article goes into the details with calculations examples. Together with the proposed PC software below you are fine with Wikis different articles.

- I got hold of a copy of a recommended book Cumpsty "Jet engine propulsion". The good thing is it takes one through a design example of a A380 frame with T900, EA7200 size engine with modern values for turbine inlet temps, compressor and turbine efficiency etc and most important of all in what order does one design an engine? He says Top of climb is sizing the engine (design point), cruise is deciding it's fuel efficiency optimization (off design) and one engine out take-off is deciding the top 5 minute turbine temp (also off design work).

He also recommended an excellent PC software http://www.gasturb.de which has a free copy http://www.gasturb.de/software.html where you all can do your own design work. Read the excellent manual for how to run optimization loops, there are many ways to do it. Also the diagram functions explain what happens much better then any textbook, the Wiki + this free copy are good compatriots. I got a full copy after fiddling with the free for a week or so, it allows one to also specify cooling losses and run more then a turbojet or 2 spool turbofan in thermodynamic only mode (no looses etc). Mail the guy at kurzke@gasturb.de for a non commercial personal copy, the price is really good, even my weekly allowance could craft it  .

- There are many NASA reports and sites which helps as well, here is a reference to an ASME contest for a UAV engine that uses Gasturb as the design tool and that reveals a lot of practical numbers http://files.asme.org/IGTI/33208.pdf . It is a small engine however so you need to change some numbers (and some can't be specified in the free copy), put in a massflow of around 1400 lb/sec in the free Gasturb and you come close to the numbers asked for by our framers, with losses I am at 1600lb/s right now for a first cut. Then play with different efficiencies, temps (1700K continuous and 1800 TO (3060 and 3240 R). For RPMs 4000 low spool and 13000 high is a good start, put the compressors at around 0.87 isentropic efficiency and the turbines at 0.9 and have fun!!

For any numbers your don't have just ask in the thread, we will give you advice (if from me be careful, blind leading blind    )

[Edited 2013-02-03 00:31:15]


Non French in France
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 5, posted (1 year 2 months 2 weeks 7 hours ago) and read 8415 times:

Given the current market environment, shouldn't this be the "Airliners-800", "Airliners-8", or even better the "Airliners-888"? 


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 6, posted (1 year 2 months 2 weeks 7 hours ago) and read 8412 times:

Quoting Starlionblue (Reply 5):
Given the current market environment, shouldn't this be the "Airliners-800", "Airliners-8", or even better the "Airliners-888"?

Bulls eye Starionblue, as these numbers schemes does not allow simple triple triple stretches (in the short form) the framers decided to go back to the old fashion numbers, the time of the -8 is over comrades they said      

[Edited 2013-02-03 00:32:04]


Non French in France
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 7, posted (1 year 2 months 2 weeks 5 hours ago) and read 8364 times:

The first Wikiversity link is a bit funny, on the page you land search for "turbojet" and you get all the relevant entries, the one about "jet engine performance" is the one with all the formulas. As said don't worry about these, the software has them all and happily calculates everything 1000 times while you graaadly get the gist of things  .

Use the page as a reference for terms and principles, you can skip Husk plots, we don't use these.



Non French in France
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 8, posted (1 year 2 months 2 weeks 3 hours ago) and read 8333 times:

To help those who want to play with free Gasturb, here what you do once installed:

1. On start window, choose 2 SPOOL TURBOFAN and Basic thermodynamics/Cycle design.

2. You are now at design point entry screen, put in these numbers:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42freeSWdesignpointscreeninput_zpsa36cab48.jpg and then the Alt (33000), M (0,82), mass flow (1400), efficiencies (0.87 and 0.9) , RPMs (4000 and 13000) and you are good to press DESIGN POINT, voila:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42freeSWdesignpointscreens_zpscd1accf0.jpg

A lot of numbers, not all immediately useful and and understood (therefore just push along with the software and revisit the texts to understand what you see), I have circled the key stuff. Look at the stations tab to understand the station markings (the red arrow shows where most EGT numbers are taken, to far back for our purposes right now, we will use it later):

http://i298.photobucket.com/albums/mm262/ferpe_bucket/Turbofanstations_zpsbfcfd58c.jpg

3. Now play with the possibilities, press for instance Properties@stations, then select what you want to see along the engine stations, for instance these parameters:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42freeSWdesignpointstations_zpsd71ba17a.jpg


Then it might be time to check the other so called off design points (your engine geometry is now defined, now you throttle it for e.g. initial cruise at FL330 or you check the Take off case):

4. Go back to main screen and press "Off-design". At the off design point you can choose your alt and M (we leave it as we want to look at what happens when we throttle back the engine after reaching initial cruise alt, but you could for instance put in 0 ft and M 0 and then our max turbine temp 3260R as a Max limiter under "Controls" to check out the TO 5 min thrust ). Press "Operating line" twice and "No" for more lines (you can do more lines later with eg varying Alt) and then choose what you want to plot, here is one example:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42freeSWoffdesignworkinglinescreen_zpscbfcadbe.jpg

I have plotted how TSFC, Burner temp, OPR and BR change as you throttle the engine at our initial cruise level. Looks like we are pretty OK with TSFC? No, not really, in the sharp version we loose some 20% of our high compressor air for cooling, sets us back to around 0.58 and we now need work (and help from pros) to get to our target   .

As said, check the manual how you can iterate etc, not all functions are there for the free version but many, have fun while fiddling, it's free    .

[Edited 2013-02-03 05:11:24]


Non French in France
User currently offlineRussianJet From Kyrgyzstan, joined Jul 2007, 7623 posts, RR: 23
Reply 9, posted (1 year 2 months 2 weeks 2 hours ago) and read 8313 times:
Support Airliners.net - become a First Class Member!

Quoting ferpe (Thread starter):
this is a mail to let you know that our sister department, Airliners.net airframes have secured funding (from a middle east consortium ) for our Airliners-200 single aisle airliner

Please do excuse the naivety, but I have never heard of this. Could we have some basic background on this? Is this a genuine, tangible project, or some kind of paper exercise?



✈ Every strike of the hammer is a blow against the enemy. ✈
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 10, posted (1 year 2 months 2 weeks 2 hours ago) and read 8309 times:

Quoting RussianJet (Reply 9):
Please do excuse the naivety, but I have never heard of this. Could we have some basic background on this? Is this a genuine, tangible project, or some kind of paper exercise?

It is 100% a fake project to have some fun together and learn about turbofans while inventing one for a fake aircraft. By playing the game you will learn a lot, not only about the facts how a turbofan is made but also a glimse of the internal politics in an aircraft project. Welcome to join the virtual team!



Non French in France
User currently offlineRussianJet From Kyrgyzstan, joined Jul 2007, 7623 posts, RR: 23
Reply 11, posted (1 year 2 months 2 weeks 2 hours ago) and read 8305 times:
Support Airliners.net - become a First Class Member!

Quoting ferpe (Reply 10):
It is 100% a fake project to have some fun together and learn about turbofans while inventing one for a fake aircraft

I see. I thought as much, but didn't want to offend anyone if by some miracle there was actually some kind of crazy real plan here.



✈ Every strike of the hammer is a blow against the enemy. ✈
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 12, posted (1 year 2 months 2 weeks 2 hours ago) and read 8301 times:

Download the software and join the team, you will for certain learn a lot .   


Non French in France
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 13, posted (1 year 2 months 1 week 6 days 20 hours ago) and read 8210 times:

I have found a really interesting Master thesis, it checks whether Gasturb, the software we are using, is any good for Bombardiers internal use to model the engine OEMs engines. The results from GasTurb 11 was compared to the engine manufacturers data supplied to Bombardier, in general Gasturb predicting within 2% of the real data. Pretty d-mn good, so thought Bombardier as well, so it will do for us as well  :

http://www.google.fr/url?sa=t&rct=j&...1b0u6A&sig2=wDmMpWxJI0ORB7QO_RPBGw

This document has many practical sections but one of the best is the table 3.2, it gives the different efficiency levels of fan, booster, HPC, burner, HPT, LPT, turbine inlet temps etc. This is sensitive data that our experts would probably have had trouble to give us in clear, here we now have it to adopt. My data given above is conservative, it is on the level of engines conceived around 2000.

[Edited 2013-02-03 11:50:16]


Non French in France
User currently offlineAviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 14, posted (1 year 2 months 1 week 6 days 16 hours ago) and read 8133 times:

Fun...
Can i help for the cabin layout?
I was looking at an a310 neo... But it looks like a twin aisle narrowbody


User currently offlinefrancoflier From France, joined Oct 2001, 3613 posts, RR: 11
Reply 15, posted (1 year 2 months 1 week 6 days 16 hours ago) and read 8120 times:

Quoting Aviaponcho (Reply 14):

Hmmm. Cross section, parasite drag...

I think the 757-300 is the role model here. Single aisle, 6 abreast, classic but efficient.
It could be made a little wider. LD3 capability would be nice, but that would stretch it a bit. 'Low-profile' LD3, like the A320 family, will do.



Looks like I picked the wrong week to quit posting...
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 16, posted (1 year 2 months 1 week 6 days 10 hours ago) and read 8059 times:

Quoting Aviaponcho (Reply 14):
Fun...
Can i help for the cabin layout?
I was looking at an a310 neo... But it looks like a twin aisle narrowbody

Absolutely! Please help with the seating, seat and isle withes etc.

Quoting francoflier (Reply 15):
I think the 757-300 is the role model here. Single aisle, 6 abreast, classic but efficient.
It could be made a little wider. LD3 capability would be nice, but that would stretch it a bit. 'Low-profile' LD3, like the A320 family, will do.

You are right on the money    , it is also a little wider then the A320/737 crop, 3.90 instead of 3.70 (A320) or 3.54 (737). Arliners,net would not put a 1980/1950 cross section on their shiny new frame would they    We are asking the pax to sit still for up to 8-9 hours, better have some decent seat withs in there. I don't know if 3.90 cuts it, please check otherwise we have to ask the framers to widen the ship further  .

Re cargo, a LD3 would not fit 2 abrest in a SA unless you make it a bit pregnant IMO (and we don't want that do we  ), therefore the A320 LD3 low profile will have to do. How many would one get into such a belly?

[Edited 2013-02-03 21:44:11]


Non French in France
User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 17, posted (1 year 2 months 1 week 5 days 4 hours ago) and read 7879 times:

Ferpe,
What is the basic layout for Airliner200 ? 220 PAX seems 2 class configuration with a not so qualitative front section ?


A310-300
Juste remembering the A310-300 coming with a perfect 2 LD3 capable cross section is a
77-79 t OEW airplane (depending on TOW), > 5000 Nm with late 70's technologies

It's 46.66 m long and 43.9 m span.

It was a 243 PAX all tourist @34 in 8 abreast or 265 seats @34 9 abreast

Airtransat l'utilise encore : http://media.transattravel.com/airtr..._b2c/flotte/310_300_FR-europe.html

I'm sure it's worth looking at...
Sure you can shave as much as 4-5 t of weight going CFRP wing and new legs, optimised tail section
Sure you can have a 20% fuel burn gain easily
Sure you need something in the 45 klbfs+ range for 150-155 t MTOW maybe less ? for more payloard
What do you thinhk


Airliner 200
Otherwise with 3.9 m Internal (153.5") width you can go 1+4+1 (twinaisle) with 17.5" seat cushion and 17" aisle
See Frequent's Traveller concept here http://fr.slideshare.net/Frequent_Traveller, and 1+2+1 in biz with no excuse me seats
It will allow quick rotation time and cabin product differentiation

Nice to play btw


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 18, posted (1 year 2 months 1 week 5 days 2 hours ago) and read 7849 times:

Quoting aviaponcho (Reply 17):
What is the basic layout for Airliner200 ? 220 PAX seems 2 class configuration with a not so qualitative front section ?

You got all the dimensions in the first table, it is in the first brown section in the middle between the blue thin lines.


Quoting aviaponcho (Reply 17):
Airliner 200
Otherwise with 3.9 m Internal (153.5") width you can go 1+4+1 (twinaisle) with 17.5" seat cushion and 17" aisle
See Frequent's Traveller concept here http://fr.slideshare.net/Frequent_Traveller, and 1+2+1 in biz with no excuse me seats
It will allow quick rotation time and cabin product differentiation

Very interesting, what would it mean in a normal 3+3 in term of seat withs? I will look at what the A300 cross section means in drag etc, give me a day or so, it is an interesting alternative.

Quoting aviaponcho (Reply 17):
Nice to play btw

Absolutely, let's play with the aircraft and the engine, it is more fun that way. Perhaps we will find something REALLY interesting   Wow!

[Edited 2013-02-05 05:22:36]


Non French in France
User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 19, posted (1 year 2 months 1 week 5 days 1 hour ago) and read 7838 times:

As Frequent Traveller explained me, there's a max width for triplet seats that is due to the fact that hostess/stewards should be able to reach the third person near the windows without climbing on the first passenger.
So basically airbus 18" triplet (wide seat) for the A320 is near to the max... so staying single aisle the airliners2000 whicjh is 7-8 in wider than the A320 may end up with the same seats but with an aisle "champ elysée style" at >22 in width.

http://avia.superforum.fr/t908-irkut-ms-21#17407 (I don't know If I can link it)

It can be good for turn around time, but I think twin aisle narrowbody can be a good idea.


BTW i only we can be sure of the internal width of the C919 and the MS21 !

My assumptions for twin aisle above is 17.5 seat width (similar to 787 @9 abreast I think), 1.5" armrest, 17.5" aisle

Ok for cabin length and width.... is length between front of door 1 to aft of door 3 (or 4), what king of exit configuration shall we use ?


User currently offlineboacvc10 From United States of America, joined Jul 2006, 587 posts, RR: 0
Reply 20, posted (1 year 2 months 1 week 4 days 18 hours ago) and read 7763 times:

Quoting ferpe (Thread starter):
his is a mail to let you know that our sister department, Airliners.net airframes have secured funding    (from a middle east consortium    ) for our Airliners-200 single aisle airliner

I'd be interested to help out if the project has a better name! Is "N2XX" type satisfactory? AXXXX is airbus, BXXXX is boeing CRXX, ERXX are taken, and Airliners.net does not lend it self to good abbreviation as ANXXXX as that is taken as well.

Reason: If we are to get top billing as a commercial company at the next big air show (UK, Mid-East*** or Far-East), we need to have a catchy name, and fast, ad-space is limited !



Up, up and Away!
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 21, posted (1 year 2 months 1 week 4 days 4 hours ago) and read 7677 times:

Quoting boacvc10 (Reply 20):
N2XX" type satisfactory?

Absolutely, but I'm just the engine department mgr  cry  , well have to pass it to the framers (ie you all  ) to see if it passes    . If we don't have violent complains in this thread say in a couple of days it is done and dusted    .

[Edited 2013-02-06 02:55:02]


Non French in France
User currently offlineLH707330 From United States of America, joined Jun 2012, 593 posts, RR: 0
Reply 22, posted (1 year 2 months 1 week 3 days 22 hours ago) and read 7618 times:

Back in its day the A300 was the most efficient people mover, hence the term "continental shovel." I hear LH still misses their capacity on thick routes within Europe. If you gave the legacy carriers a good, light 250 seater with a nice premium option, I bet they'd bite.

If the plan is to go with two aisles, you're adding weight in the width, so I think you have to go 8-across WB or 6-across NB, but not 7.


User currently offlinePolot From United States of America, joined Jul 2011, 2047 posts, RR: 1
Reply 23, posted (1 year 2 months 1 week 3 days 18 hours ago) and read 7572 times:

You are forgetting the most important detail. Will it be controlled by a yoke or a sidestick?   

User currently offlinewingscrubber From UK - England, joined Sep 2001, 845 posts, RR: 0
Reply 24, posted (1 year 2 months 1 week 3 days 18 hours ago) and read 7564 times:

This might be a little risky in terms of R&D, but I would like to propose my unconventional twin-core contra-rotating ducted dual fan engine concept...  http://i32.photobucket.com/albums/d37/Peeto999/TwinPT6.jpg
I anticipate some resistance to this approach, but I'm fairly certain it could work! Kuznetsov NK-93 is the closest equivalent.



Resident TechOps Troll
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 25, posted (1 year 2 months 1 week 3 days 10 hours ago) and read 7649 times:

I'm not an engine guy but I like to try wrap my mind around wacky concepts...no matter how out to lunch they may be..so here goes.

How about an engine with contra rotating geared ducted fans? The planet gears are fixed, with one fan attached to the sun gear and one to the rig gear. The fans would spin in opposite directions at different speeds, (I think), which is ok since that might take some harmonics, (and hopefully noise), out of the system. Keeping the fans ducted prevents a lot of noise issues.

I see the thing as a longer, wider CSeries...Al-Li fuse, CFRP wings. It would have to be about the same size as the 757, with gear long enough for some big, fat fans, crazy long wings, maybe folding tips. Maybe even a high wing, so engine size or gear length would never be an issue, and you could keep the fuse height to a minimum to better serve more austere airports...a x2 An-158.



What the...?
User currently offlineLH707330 From United States of America, joined Jun 2012, 593 posts, RR: 0
Reply 26, posted (1 year 2 months 1 week 3 days 9 hours ago) and read 7613 times:

Quoting JoeCanuck (Reply 25):

How about an engine with contra rotating geared ducted fans?

I reckon that the weight and complexity of this will outweigh any TSFC gains, it's much easier just to have a de-swirl stage in the fan case with one more (or less?) blade than the fan itself.


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 27, posted (1 year 2 months 1 week 2 days 22 hours ago) and read 7612 times:

Quoting wingscrubber (Reply 24):
but I would like to propose my unconventional twin-core contra-rotating ducted dual fan engine concept...

Nice picture but how do you propose that we analyze it's efficiency? The Gasturb software has a number of configs, but not that one         



Non French in France
User currently offlinebhill From United States of America, joined Sep 2001, 925 posts, RR: 0
Reply 28, posted (1 year 2 months 1 week 2 days 19 hours ago) and read 7573 times:

Err...."vaned conveyor belts" pushing the air mass in.......

 

Birdstrikes would be a thing of the past......



Carpe Pices
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 29, posted (1 year 2 months 1 week 2 days 14 hours ago) and read 7542 times:

Quoting LH707330 (Reply 26):
I reckon that the weight and complexity of this will outweigh any TSFC gains, it's much easier just to have a de-swirl stage in the fan case with one more (or less?) blade than the fan itself.

How about a variable pitch GTF?



What the...?
User currently offlineLH707330 From United States of America, joined Jun 2012, 593 posts, RR: 0
Reply 30, posted (1 year 2 months 1 week 1 day 20 hours ago) and read 7458 times:

Quoting JoeCanuck (Reply 29):
How about a variable pitch GTF?

I bet it's too complex/unreliable/susceptible to bird strikes. Let's assume these hurdles can be overcome though, then it gets interesting: assuming a conventional engine is sized for max. takeoff thrust and is thus too large at cruise, you could design a fan that has an optimal alpha on the takeoff roll, which should let you get away with a narrower fan (with a possible noise penalty). When climbing you can have a slightly finer pitch to keep N1 up, and at cruise you can go back to a coarser pitch to reduce ram drag. What I'd like to know is how fixed-pitch fans are optimized in terms of blade alpha (cruise vs. takeoff), and how much efficiency you can gain from varying them. Ideally you get a smaller engine with a 5-minute temp-limited medium-coarse setting for takeoff that is then more efficient at cruise because it's working harder and has less nacelle drag.

Another avenue I'd be interested in exploring is water-cooled HPT blades. My dad used to ask me "if it's such a good idea, why hasn't someone done it?" Maybe someone can help here. Most engines take bleed air from the compressor and use it to cool the blades downstream by pumping the air through the blade. Although it keeps the blade from melting, you lose thrust and SFC by robbing compressed air from the combustion chamber. If you had a small water reservoir in the core that fed the blade cooling tubes and expended the water out the blade holes for 5 minutes during takeoff, you could regain thrust from the lack of bleed and from the pressure rise as you release the superheated water out the back of the blade as steam. The system runs out of water as you're throttling back to climb power and you revert to bleed for cooling. You get more thrust from these three factors:
1. No bleed->more combustion air
2. Higher TIT tolerance (thus more thrust) because the water carries away more heat
3. Increased mass flow and pressure from the steam

Combined, these let you make a smaller engine with its attendant benefits (less weight/nacelle drag, less wing reinforcement, shorter gear (more weight saving), and higher cruise thrust/TSFC). Most takeoffs are derated anyway, so you'd only need it rarely. As far as answering my dad's question, I imagine water pressure would be north of 1000 PSI, which might make it difficult to keep it liquid until expelled into the airstream. If you get steam bubbles, you lose cooling and the blade melts (bad news). I bet there are other problems with the idea, but if we're looking at variable pitch fans and back-to-back turboprops I figured I'd throw this idea in the ring too.


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 31, posted (1 year 2 months 1 week 1 day 8 hours ago) and read 7399 times:

Quoting wingscrubber (Reply 24):

That's definitely out of the box thinking but it is an interesting concept.

Quoting LH707330 (Reply 30):
What I'd like to know is how fixed-pitch fans are optimized in terms of blade alpha (cruise vs. takeoff), and how much efficiency you can gain from varying them

Some turbo props are getting so many blades that they are looking like fans to me;





What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 32, posted (1 year 2 months 1 week 1 day 7 hours ago) and read 7389 times:

Quoting JoeCanuck (Reply 29):
How about a variable pitch GTF?

We will start to look at and discuss more exotic ideas but before that lets see how far one can reach the spec with a classical Direct Drive 2 spool turbofan (DDTF) and a rusty (actually new beginner) chief designer fiddling with the excellent software Gasturb. First a table for those like me have problems with the mix of units in the engine world:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/Conversiontable_zpsfeed341a.jpg

This makes it easier for everyone to take the data into the units one is used to. Then the engine variant that comes closes to meeting the framers expectation after 2 weeks of fiddling. First the performance and key data:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF39data_zps15207907.jpg

As you can see the engine is slightly smaller (9600lbf at the design point, Top of Climb, ToC). I increased the Turbine Inlet Temp, TIT (or Stator Outlet Temp, SOT) T41 which sizes the core. This makes for a smaller, more efficient core and ultimately engine. I also put in the cooling flows and fan/compressor/turbine efficiencies according to the Bomardier study:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/Coolingflownumbers_zpsd900e47d.jpg
http://i298.photobucket.com/albums/mm262/ferpe_bucket/Efficiencytable_zps644b1b60.jpg

I kept the bypass ratio at 9 at ToC for now, we will explore what and increased BPR means in terms of TSFC and weight/dimensions in the next step. The nice thing with Gasturb is, it not only helps you with the thermodynamic design but also sketches the engine for you and even gives you the key physical data:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42GeometryV4_zps8e18a8a7.jpg

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42maindimensions_zpsd38b68ba.jpg

So what has changed inside the engine? Here the design point screen with the key data circled and then the working line or throttled engine at our initial cruise height of FL330:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF39designpoint_zps3e8d3b66.jpg

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42workinglineFL3500823240RV1_zps938aba7b.jpg

Look at the mass flow table at the left, mass does not vanish it just splits up in core (some 10%) and bypass, you can see the bypass again in the last station. Here the stations in the engine with also shows the cooling flows:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T39stations_zps58249340.jpg

So we have a bare engine (less gearbox and other accessories) that weighs 10klb/4500kg and gives us a cruise TSFC of 0.55, pretty close to what the framers asked for but not there. Look into the data at your pace, there is a lot, but it gradually dawns on one what if all should be good for. Especially the throttle diagram tells what happens with PR, BPR, RPM of the fan etc as one regulates the power of a turbofan at height. Also look in the first table for these values at Start and at 50ft V2 where one has to reach 2.4% climb One Engine Inoperative (OEI) to get certification for a twin.



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User currently offlinerwessel From United States of America, joined Jan 2007, 2238 posts, RR: 2
Reply 33, posted (1 year 2 months 1 week 1 day 6 hours ago) and read 7377 times:
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Quoting LH707330 (Reply 30):
Another avenue I'd be interested in exploring is water-cooled HPT blades. My dad used to ask me "if it's such a good idea, why hasn't someone done it?" Maybe someone can help here. Most engines take bleed air from the compressor and use it to cool the blades downstream by pumping the air through the blade. Although it keeps the blade from melting, you lose thrust and SFC by robbing compressed air from the combustion chamber. If you had a small water reservoir in the core that fed the blade cooling tubes and expended the water out the blade holes for 5 minutes during takeoff, you could regain thrust from the lack of bleed and from the pressure rise as you release the superheated water out the back of the blade as steam. The system runs out of water as you're throttling back to climb power and you revert to bleed for cooling. You get more thrust from these three factors:
1. No bleed->more combustion air
2. Higher TIT tolerance (thus more thrust) because the water carries away more heat
3. Increased mass flow and pressure from the steam

Although injected slightly further upstream, that's basically what "conventional" water injection does.


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 34, posted (1 year 2 months 1 week 1 day 1 hour ago) and read 7344 times:

Quoting ferpe (Reply 32):

We will start to look at and discuss more exotic ideas but before that lets see how far one can reach the spec with a classical Direct Drive 2 spool turbofan (DDTF) and a rusty (actually new beginner) chief designer fiddling with the excellent software Gasturb.

Have at it, Maestro. Great thread.

I wonder, even with more exotic materials research, if we're getting close to the point of diminishing returns for the two spool, (and probably 3 spool as well), designs. Since no engine can be 100% efficient, there is always room for improvement but my thumbnail sketch interpretation of your data so far, indicates to me that we may be running out of room for many more significant efficiency gains, at the very least without affecting reliability.



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 35, posted (1 year 2 months 1 week 18 hours ago) and read 7313 times:

In the post above I put in the wrong throttle diagram for Top of Climb and the beginning of cruise, here the correct one:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42FL330M082workingline_zps68320119.jpg

Here one can also see the N1 low spool RPM as LPT relative corrected speed. Note that at this FL the cruise point of the engine is close to the max continuous RPM (94%). GE and CFM engines use N1 as the primary parameter for setting the thrust level of the engine (ie the relative RPM in % of low spool with has the fan, booster and LPT), RR and PW uses the ratio of the total pressure over the engine. You have this ratio as P5/P2 in the mission table (the first engine table in my last post). This is the ratio of pressure after the turbine compared to the inlet just before the fan. Sometimes the rear sensor can sit further back is a so called P7 location (PW). The P5/P2 system takes account of the real engine situation, ie what happens including density changes, the N1 principle is a more indirect thrust indication but easier for many Pilots to understand.

One thing that I finally understood when trying to optimize the TF42 to a lower TSFC ie higher efficiency, was why engine OEMs say they need to adapt the engine to the aircraft, e.g. RR is not to keen on retrofitting an existing engine to another aircraft. To understand why we need to look at how the main components of an engine is matched to achieve what one want. The most important seems to be to match the compressors characteristics to the mission profile (the turbines are less critical in their characteristics). The area of engine design which shows these characteristics are the compressor maps. If we start with the high compressor map one can see the following:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42FL330M082HPCmapworkingline_zps06b527b6.jpg

The design point is at the N = 1 or 100% RPM line (the lines which start vertically and bend left), one can also see the cruise point in the compressor map, it is at N = 0,95 for the HPC (unfortunately I did hide this line "relative corrected N2" in the mission table). The map is made from CFD analysis of the compressor and then verified with bench trials of test compressors driven by an electrical motor. The map we see in the picture is a scaled and repositioned standard map in Gasturb designed to be typical of such maps but not an actual engine map for eg TF42. It does show the principals and we see a couple of interesting things;

- The engine only uses the working line part of a map, the map is an area map however so we can see how the line should be ideally placed. The map is done as a quasi 3D mountain so we can see where the compressor has it's max efficiency (the top of the mountain, you also see the height curves = efficiency curves). The axis are pressure ratio and relative corrected airflow. The latter means one map can represent all speeds and altitudes as all factual airflows are transposed to the static sea-level case.

- The working line placement and the placement of the different mission working points in the map is not a happening, the engine design is massaged until the line and the different points like ToC and Cruise are placed in areas for maximum mission efficiency. Therefore the ToC=max continuous is just past the compressor optimum but not to far down the other side. When you then throttle back to the cruise range (around N= 0,95) it will fall into the area where the compressor has it's highest efficiency (0.86), ie it consumes the least energy from the turbine for a given compression ratio. You spend very little time at TO, more at climb and longest at cruise. Therefore you prioritize cruise to get the sweet spot of the compressor and the others will have to do with more compromised positions.

- We can also see that the working line stays within the map, it does not cross the red surge line like the booster map does:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42FL330M082IPCmapworkingline_zps6ab4e857.jpg

Was this a real case I would have to put a bleed port behind the booster in the duct to the HPC to get the line to come down from the surge line at low throttle settings. As the line is not at all lined up with the compressor characteristics the bleed port and other actions would definitely be needed, I haven't yet figured out what to do however. Boosters are tricky as they sit on the same shaft as the Fan but at a fraction of the optimum radius. The Fans tips are placed at optimum speed of around M1.1, it then follows that the boosters blades are far of their optimum speed. A booster therefore does not produce much pressure ratio per stage and also has problems with efficiency. This is where GTFs or triple spools come in to fix that, more of later.

- Finally the fan map:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42FL330M082Fanmapworkingline_zps08b3867e.jpg

Here 2 things are important, the cruise efficiency (at N = 0,90 - 0,93 ) and low noise at TO power (N = 0,91). The latter means a fan pressure ratio not very much higher then 1.6 (for low speed on the bypass mass flow). For cruise and ToC efficiency I had to put ToC at 1.8 (speed line N = 1,0 in the map), when that resulted in TO PR of 1.69 it was acceptable. We see that ToC is down at the 0.88 efficiency curve and I don't quite hit the 0.92 island at cruise. Here there would be more work required to get the last % of TSFC.

With the above I have tried to show what I have found during my fiddling with Gasturb, the program has several well designed methods for findings these optimums, it has been mainly the designers capability that has been the problem here  Wow! . I am happy however as I now know what the engine guys are talking about when they say they have to tune the engine to the frame  .

[Edited 2013-02-09 13:29:57]


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User currently offlineLH707330 From United States of America, joined Jun 2012, 593 posts, RR: 0
Reply 36, posted (1 year 2 months 1 week 5 hours ago) and read 7253 times:

Quoting rwessel (Reply 33):
Although injected slightly further upstream, that's basically what "conventional" water injection does.

Problem with that water injection is it results in poor combustion and consequently smoke, which is bad news these days.


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 37, posted (1 year 2 months 6 days 7 hours ago) and read 7175 times:

Before we move to more advanced architectures I did try to reach our TSFC cruise goal by increasing the BPR from 9 to 10 and then 11 at the design point, Top of Climb. For 10 there was a small improvement down to 0.544 at mid cruise weight:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF38dataBPR10_zps3120b256.jpg

As can be seen a lot of data changes, eg the ToC BPR is locked at 10 which has as consequence that the static BPR goes to 10.84. This is close to the BPR for the LeapX for A320neo which is said to have BPR 11 (it is probably static as GE normally don't give ToC data). I also ran BPR 11 at ToC but then the TSFC backed up again. This is probably because you need to reoptimize the core to gain from BPR 11. BPR 11 raises the propulsive efficiency but might lower the thermal efficiency unless one reoptimizes the core for this higher load on the low pressure turbine. This improvement in efficiency is also on a pure engine basis. On frame level we need to trade that against the increase in OEW and an increase in drag from the larger nacelle as the fan dia increases (look in the dimensions tables for T42 BPR9 above and BPR10 below).

Here the table for our BPR10 engine variant, the weight goes up 1200lb and the engine dia goes from 94'' to 98'':

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42BPR10V4maindimensions_zpsc07fb24b.jpg

This makes for 2400lb/1100kg on a frame basis for our two holer before we start to count the nacelle effects. 1100kg is 1/3 of our average fuel flow per hour (TSFC*thrust*2 engines) of 3200kg/hour so we loose some 150nm because of this weight increase before we count the drag increase. A quick check shows that this is really marginal as we gain trip duration (11 hours) * the TSFC diff (0.556-0.544=0.012) * cruise thrust (2*6500lbf) = 1700kg. These 1700kg gain shall be weighted against the 1200kg heavier engines and heavier and larger nacelles. As the frame does not always flies for 11 hours but often shorter trips of perhaps half max duration the gain in fuel burn is halved but the weight and drag increase remains and we are better off with a BPR 9 engine.

The above shall show some of the principal trades around propulsive efficiency vs engine size and weight. For a given engine size the BPR can increase without these negative effects if we can make a higher performing core as the fan stays the same but less air goes through the core ie we have higher BPR and therefore higher propulsive efficiency without weight and drag increase. This is the reason the LeapX for A320 has an optimum BPR of 11, we can rest assured CFM knows how to calculate these kind of trades together with Airbus  .

This is also what CFM has been working on with Boeing for the 737MAX, they have increased the core efficiency to the max via component tuning and shrunk it's size in terms of mass flow as far as possible so that they get the maximum BPR and thus overall efficiency inside the 69'' fan dia restriction the MAX poses.

As we now have two tables with a lot of data we can compare let me comment on two rows, Gross thrust (just below our Net thrust) and Specific thrust (2 rows further down). An engines thrust is the net difference of generated momentum (air mass flow * air speed ) minus the momentum of the air we travel in (aircraft speed * intake massflow ). The Gross thrust is the momentum the engine generates and the Net thrust then what is left to drive the aircraft forward. This is easily seen in the static case where we gain all Gross thrust as Net. This loss in Net thrust with speed is also called Lapse or Lapse ratio. Look at the lapse at our V2 point just after takeoff, we are down at 31.9klbf for our BPR9 engine and 30.6 for our BPR10 engine, loss of thrust with speed increases with higher BPR.

The Specific thrust is the net difference in speed between incoming air and outgoing, thus it tells us how close we are to optimum propulsive efficiency as this is max when the outgoing air has the same speed as incoming (we don't have any thrust momentum then but the propulsive efficiency formula does not care about the absolute amount of thrust, just it's efficient creation  Wow!  ). This is why the specific thrust is the best measure of propulsive efficiency, better then BPR which is only an indirect indication of propulsive efficiency level. The specific thrust of those propfan ships we see up-threat is sure to be low  .

[Edited 2013-02-11 00:40:20]


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User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 38, posted (1 year 2 months 6 days 6 hours ago) and read 7144 times:

Quoting ferpe (Reply 37):
The Specific thrust is the net difference in speed between incoming air and outgoing, thus it tells us how close we are to optimum propulsive efficiency as this is max when the outgoing air has the same speed as incoming (we don't have any thrust momentum then but the propulsive efficiency formula does not care about the absolute amount of thrust, just it's efficient creation Wow! ). This is why the specific thrust is the best measure of propulsive efficiency, better then BPR which is only an indirect indication of propulsive efficiency level. The specific thrust of those propfan ships we see up-threat is sure to be low

I find this bit especially interesting...and somewhat counter intuitive. Does specific thrust include the bypass air and the core flow? I assume Specific Thrust can never be zero but it would seem to me that at some point, (I'm guessing cruise due to the thinner air and higher aircraft speeds), the core will provide a greater proportion of total thrust than the fan.



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 39, posted (1 year 2 months 6 days 4 hours ago) and read 7129 times:

Quoting JoeCanuck (Reply 38):
I find this bit especially interesting...and somewhat counter intuitive. Does specific thrust include the bypass air and the core flow?

The scientific definition of specific thrust is the total net thrust divided by the total mass flow, thus both core and bypass mass flows (and the minute added fuel mass flow) and thrusts are counted. This is exactly the same as the difference in the average bypass+core air speed and the aircraft speed (if we ignore the fuel mass). I find this definition easier to grasp as the more formal one, and one can think of it like:

- to get any thrust the air mass going into the engine has to be accelerated somehow (the air mass stays the same, no mass disappears, it just changes speed).

- The specific thrust describes how much we accelerate the air mass. If we accelerate little we need lost of air mass to drive an aircraft (low specific thrust), if we accelerate a lot (e.g. Concorde engines) we need less mass of air to achieve the net thrust to drive the frame and the lapse is less.

- Now the gain in accelerating the air a lot is that we have thrust left at high speed (Concorde accelerating to M2), the flip side is that it is less efficient if the frame is an airliner flying at M 0.82.


Thus the specific thrust tells us the excess speed of the air leaving the engine  Wow! , the less the more efficient (if we can rally the air mass needed to get to our necessary thrust level).

[Edited 2013-02-11 03:18:36]


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User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 40, posted (1 year 2 months 6 days 1 hour ago) and read 7094 times:

Quoting ferpe (Reply 39):

- The specific thrust describes how much we accelerate the air mass. If we accelerate little we need lost of air mass to drive an aircraft (low specific thrust), if we accelerate a lot (e.g. Concorde engines) we need less mass of air to achieve the net thrust to drive the frame and the lapse is less.

Just to keep things clear in my head, we're talking mass over time, right? Using your Concorde example, it's engine if afterburner is rated at about the same thrust as one 757 engine, so as I understand it, they both would be pushing about the same mass of air over time but the RB111 moves the air slowly and the Concorde engines move the air significantly more quickly.

I seem to recall someone mentioning that the efficiency differences partly exist because the force required increase air mass moved by moving twice the air at the same speed is doubled while moving twice the air by doubling the velocity of the air is the force squared.

Quoting ferpe (Reply 39):
Thus the specific thrust tells us the excess speed of the air leaving the engine Wow! , the less the more efficient (if we can rally the air mass needed to get to our necessary thrust level).

So sorts out what I've seen before about bypass flow, and why BPR isn't necessarily the most accurate way to calculate engine efficiency, since one can have a smaller fan spinning faster, or a larger fan spinning more slowly....both bypassing the same mass of air over time but the smaller one moving the air faster.

This is how Rolls says they are going to keep the same size fan and BPR on the -1000 XWB engine as the less powerful -900 engine, by spinning the -1000 fan faster.

So with the TF42, (and I presume the Leap as well), are we bumping up against materials, (or other), limits for size and temp of the core, and as a result, efficiency?



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 41, posted (1 year 2 months 5 days 21 hours ago) and read 7048 times:

Quoting JoeCanuck (Reply 40):
Just to keep things clear in my head, we're talking mass over time, right?

Instant time, ie lb/s or kg/s is the unit for mass flow.

Quoting JoeCanuck (Reply 40):
Using your Concorde example, it's engine if afterburner is rated at about the same thrust as one 757 engine, so as I understand it, they both would be pushing about the same mass of air over time but the RB111 moves the air slowly and the Concorde engines move the air significantly more quickly.

They have the same thrust therefore their product massflow in lb/s * speed in ft/s would be the same, the Olympus in the Concorde push a small mass fast and the 757 PW2000 push a large mass slowly. They both have the same thrust but they differ widely in specific thrust, the Olympus having high spec thrust and the PW2000 low.

Quoting JoeCanuck (Reply 40):
So with the TF42, (and I presume the Leap as well), are we bumping up against materials, (or other), limits for size and temp of the core, and as a result, efficiency?

Yes we are to some extent, there is still potential left but the low hanging fruit is gone. Kurzke, the ex MTU chief performance guy and the maker of the Gasturb program has made a paper about it: http://mtu-rzeszow.com/en/technologi..._maximum_thermal_efficiency_en.pdf

As can be seen beyond 40 and especially 1800K at cruise there is not much more to gain by higher temperatures. For pressure ratio you do gain a bit up to 60 but then no more. This is not the same as RR and GE does not know this when the say the 777X engines will have PR of 60, this is for the max performance part like ToC, this means the important cruise phase will land at around 40-50 and 1700-1800K where the max efficiency will reside with real world components and fuels, at least according to Kurzke.

[Edited 2013-02-11 10:54:02]


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User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 42, posted (1 year 2 months 5 days 13 hours ago) and read 6984 times:

Quoting ferpe (Reply 41):
As can be seen beyond 40 and especially 1800K at cruise there is not much more to gain by higher temperatures. For pressure ratio you do gain a bit up to 60 but then no more. This is not the same as RR and GE does not know this when the say the 777X engines will have PR of 60, this is for the max performance part like ToC, this means the important cruise phase will land at around 40-50 and 1700-1800K where the max efficiency will reside with real world components and fuels, at least according to Kurzke.

Very interesting paper...I'm fuzzy on the maths but the concepts and graphs are pretty clear. It does seem that the engine makers are running out of headroom. That being said, the new engines will be crazy efficient...which is quite a feat considering the current generation of engines already have amazing efficiencies, and to top it off, those efficiencies are coupled with anvil like reliability.

What happens if the TF42 engine fan is geared?



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 43, posted (1 year 2 months 5 days 12 hours ago) and read 6986 times:

Quoting ferpe (Reply 41):
As can be seen beyond 40 and especially 1800K at cruise there is not much more to gain by higher temperatures.

This should be modified to PR 45 and 1500K, here the conclusive diagram from the Kurzke paper. This is an aircraft turbofan cruising at FL360 with typical components, only the core (thermal) efficiency is evaluated. What is drawn is the thermal efficiency mountain with the thermal efficiency as TSFC in SI units as height rings and with PR and T4 ie burner temperature on the axis. As can be seen reaching the absolute optimum would need PR 60 and 1650K ( 2 ) but we would only loose 0,5% TSFC by staying at 45 and 1500K (TSFC in SI units means 13.6 represents 0.480 and 13.4 is 0.473 in lbm/hr/lbf ) :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/ThermalefficiencyatFL360_zpsff6f3139.jpg

So down to TSFC 0.5 is doable, then it gets hard with the classical core technology used today. Further if one asks an engine guy, does he prefer cruise values of PR 45 and T4 1500K over 55 and 1650K you know the answer , it is the law of diminishing return, better go and search in some other corner for those last drops of fuel.

Quoting JoeCanuck (Reply 42):
What happens if the TF42 engine fan is geared?

This corner we will explore now  Wow! .

[Edited 2013-02-11 19:11:49]


Non French in France
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 44, posted (1 year 2 months 5 days 12 hours ago) and read 6978 times:

Quoting ferpe (Reply 43):
it is the law of diminishing return, better go and search in some other corner for those last drops of fuel.

...and something sometimes forgotten in the quest for those last drops, reliability. Airlines have become pretty spoiled with those bullet proof CFM 56's and the like hanging from their wings. They are not likely to accept marginal gains in fuel efficiency at the expense of that reliability.

Quoting ferpe (Reply 43):
This corner we will explore now

My gut feeling is CFM will pretty much match the first gen GTF's with their Leap engine...but where the Leap seems to be pretty much maxing out the current technology, (pun intended), Pratt's GTF seems to have more room to grow. It looks like it can achieve at least the same efficiencies as the Leap but without having to be quite so bleeding edge with the materials.

Methinks everybody is going to have a GTF in the next generation or two. Since Pratt seems so reluctant to supply an engine for the TF42, our engine maker might be well served by hunting down a likely gearbox maker.

[Edited 2013-02-11 19:30:22]


What the...?
User currently offlinelightsaber From United States of America, joined Jan 2005, 12419 posts, RR: 100
Reply 45, posted (1 year 2 months 5 days 11 hours ago) and read 7001 times:
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First, Ferpe has been inviting me to this thread for a bit. I must apologize for not being proactive, but I had a reunion last weekend.   

Second, the numbers do come out very analogous to the LEAP-X optimization.

Quoting JoeCanuck (Reply 42):
What happens if the TF42 engine fan is geared?

Now as to how a GTF helps. The GTF decouples the fan from the low turbine. So both improve in efficiency as does the low compressor. Does the TF42 have a variable fan nozzle? This allows for there to be multiple 'fan lines.'

Quoting JoeCanuck (Reply 38):
I assume Specific Thrust can never be zero

There can be negative thrust. For example, during flight idle.

Quoting ferpe (Reply 43):
This is an aircraft turbofan cruising at FL360 with typical components, only the core (thermal) efficiency is evaluated.

Just to be clear, by GE raising their metal temperatures, they improve efficiency at higher temperature by requiring less cooling.

Quoting ferpe (Reply 35):
Boosters are tricky as they sit on the same shaft as the Fan but at a fraction of the optimum radius. The Fans tips are placed at optimum speed of around M1.1, it then follows that the boosters blades are far of their optimum speed.

Not in a GTF or triple spool.   

Quoting ferpe (Reply 35):
The Fans tips are placed at optimum speed of around M1.1

New blade profiles reduce the shock losses and thus move the optimum up to M1.2 or so. (LEAP-X), not applicable to the GTF.   (Its not worth putting in the high cost fan blades when there is a gearbox.)

Quoting ferpe (Reply 37):
BPR 11 raises the propulsive efficiency but might lower the thermal efficiency unless one reoptimizes the core for this higher load on the low pressure turbine.

Or go to a GTF with a tubrine at a far more optimal mach #. Most of the GTF's efficiency improvement is the low turbine.   

Quoting ferpe (Reply 37):
As the frame does not always flies for 11 hours but often shorter trips of perhaps half max duration the gain in fuel burn is halved but the weight and drag increase remains and we are better off with a BPR 9 engine.

There you sound like a RR engineer.   However, there are two ways out of this 'pickle.' #1, work on a lighter engine as GE did with the LEAP (how they brought down the weight of the low pressure turbine, I would love to know...). The other is the GTF where by having the low turbine spin at a more optimal Mach #, far fewer blades are required keeping the weight down allowing for the optimization at higher bypass ratios.

Quoting ferpe (Reply 41):
Kurzke, the ex MTU chief performance guy and the maker of the Gasturb program has made a paper about it:

That paper is interesting, but the author is a bit too fixated on a maximum pressure ratio of 40. That is a limit for a plane doing short hops, but not a limit if cycle life is cut for long haul. New generation coatings are becoming available to raise the temperatures and that will raise the practical pressure-ratio limit. While the progress has been slowed waiting for an effective ceramic.


Lightsaber



I've posted how many times?!?
User currently offlinelightsaber From United States of America, joined Jan 2005, 12419 posts, RR: 100
Reply 46, posted (1 year 2 months 5 days 10 hours ago) and read 6986 times:
Support Airliners.net - become a First Class Member!

A post that helps this thread on the GTF (warning, pdf):

See slide 16 as the GTF allows lower fan pressure ratios and thus less noise and higher fan efficiency.

Slide 18 represents engine efficiency a bit more simplified (not good enough for this engine design, but for those trying to wrap their mind around the concept).

http://events.aviationweek.com/html/...ngine%20Concept.SABNIS%20(P&W).pdf


Lightsaber



I've posted how many times?!?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 47, posted (1 year 2 months 5 days 9 hours ago) and read 6969 times:

Quoting lightsaber (Reply 45):
Does the TF42 have a variable fan nozzle? This allows for there to be multiple 'fan lines.'

Not up to now, but we could introduce it, we could have a tigther bypass nozzle for cruise that we open up for low RPM operation. What would it bring us?


Quoting lightsaber (Reply 45):
Just to be clear, by GE raising their metal temperatures, they improve efficiency at higher temperature by requiring less cooling.

And by raising T4 they improve the ability of a core to drive a bigger fan at the same core mass flow. The Kurzke diagram ONLY talked about the thermal efficiency, the engine efficiency is about thermal and propulsive efficiency. So by raising T4 even beyond the 1500-1600K discussed a DDTF would be able to run a higher BPR for the same size fan and fan case, ie same weight and drag. It would make for a more efficient engine.

The difference is that while raising PR and T4 used to deliver a double whammy (thermal and propulsive gains), now it is gradually going to a single whammy (smaller core gives a better BPR for same size engine).

But let's now see what a GTF brings.

[Edited 2013-02-11 21:52:32]


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User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 48, posted (1 year 2 months 5 days 9 hours ago) and read 6968 times:

Quoting lightsaber (Reply 46):

To me, the true beauty of the GTF is the simplicity...it's dead simple to visualise how the gearbox improves efficiency. If one has a grasp of multiple shaft jet engines, then the huge difference in diameter between the fan and the lpt shows a mismatch...in some way or another...without having to know much about engines at all.

Gears are easy...everybody whose ever driven a car or a multi speed bike knows about the effects of gearing. Add to that, knowing that turbines like to spin really fast, (the whistles coming from the turbo in my Dodge diesel attest to that), and fans would rather spin more slowly, then...bang...the pieces just fall into place.

Even the RR triple spools make sense, having another shaft and turbine powering an intermediate compressor, without having all low pressure compression tied to the fan.

I have no doubt the Leap will do what GE says it can, but by essentially decoupling the lpt and the low compressor from the fan, it just seems the GTF has not only taken the simpler, (relatively), route, but has more room to improve in the future...especially on the really big engines...and it has the advantages of a triple spool, without nearly the level of complexity a third shaft brings, compared to a gearbox.

The idea of a GTF on an engine the size of a GE-90, is really quite interesting to my inner geek.

I stick with my assertions that the GTF makes so much sense, that I have no doubts at all that the boffins at GE are throwing a lot of R&D at a gearbox. I bet Pratt is doing a lot of chatting with Boeing about the 77X...and if they can prove they have a reliable gearbox that can handle an engine putting out 100,000 lbs of thrust, GE will have a real run for its money.

[Edited 2013-02-11 21:41:47]


What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 49, posted (1 year 2 months 5 days 9 hours ago) and read 6967 times:

Quoting lightsaber (Reply 45):
However, there are two ways out of this 'pickle.' #1, work on a lighter engine as GE did with the LEAP (how they brought down the weight of the low pressure turbine, I would love to know...). The other is the GTF where by having the low turbine spin at a more optimal Mach #, far fewer blades are required keeping the weight down allowing for the optimization at higher bypass ratios.

Just as a reference, here the LPT tab from the engine dimensions of the BPR9 TF42, total weight was 10.000 lbm, thereof:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42LPturbineandshaft_zps9d6e0432.jpg

the LPT is 45% !!! and it is just the rotating part! And this is a 4 stage LPT, now take that to 6 or 7 stages of a high BPR DDTF of today (even if they use smarter design and lighter materials).



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User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 50, posted (1 year 2 months 4 days 18 hours ago) and read 6884 times:

Quoting lightsaber (Reply 46):
Slide 18 represents engine efficiency a bit more simplified (not good enough for this engine design, but for those trying to wrap their mind around the concept).

http://events.aviationweek.com/html/...).pdf

Slide 18 is about Thermal efficiency (not total engine) and it tells virtually the same story as the Kurzke diagram. I have put in the practical values from Kurzke, ie 1500K and PR 45, the gain of not only going to 55 and 1650K but all the way to 1784K (T4/T2 = 8) at PR 50 is marginal (the slide introduces the value T4/T2 which is the true figure of merit for core scaling as it also takes into account from where the compression begins, at FL330 from 223K inlet temp, click on the slides to see better ) :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/ThermalefficiencyaccPWandMTU_zps2cb1c0ac.jpg

The GE thermal efficiency slide on the next page is not in violent disagreement as well, I have put in the T41 temps in K as well. Looking at the yellow curve for 1650K and PR40 to 50 one gains 4%, you would have to increase T41 with another 480F/250K to a whopping 1900K continuous cruise temp to gain another 3% at a PR of 50. I think those 3% could be easier gained somewhere else:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/ThermalefficiencyaccGE_zps4364746a.jpg

[Edited 2013-02-12 13:30:04]


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User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 51, posted (1 year 2 months 3 days 20 hours ago) and read 6815 times:

To start the journey to look at a GTF I converted the TF42 in it's latest BPR9 version (the one with TSFC 0.54 at best) to a GTF with gear ratio 3. I only did the following changes which of course will not be enough to make a GTF justice but it was made so we can get a first comparison:

- inner fan pressure ratio reduced to 1.4 and the IPC (booster) raised to 2.3 to keep an overall ToC PR of 50 with the HPC kept at 16, the higher IPC PR is reflecting that it now spins at 12000 RPM instead of 4000.

- I reduced the LPT to 3 stages from 4 as it is now spinning 3 times faster (12000). Look in the table for the real RPMs at the different mission points (row 146 for the now faster low spool, the fan (LPC) is still at the old RPM, row 141).

I then got the following mission table:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42-GTFBPR9firstrefrunV4_zps20d24ff3.jpg

and here the principal drawing and dimensions:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42-GTFBPR9firstcut_zpsa0583c84.jpg
http://i298.photobucket.com/albums/mm262/ferpe_bucket/T42-GTPdimensions_zpse9ee3216.jpg

Note that the engine is 300lb heavier. The 3 stage booster/IPC has a PR of 2.3 as it spins faster and the 3 stage LPT gets 1500lb lighter but the gearbox eats that and 200lb more and the extra core/fan casing to include the gearbox does the rest. That it is not a 0.54 TSFC or better at average cruise should not be important before we have tuned the engine to the new architecture. The more interesting problem will be that once we start to increase the BPR and lower the fan PR, which the architecture allows and prefers, we need to ask the framers to increase the gear length or hang the engines further forward/higher like Boeing does it.

TIP: click on the tables and diagrams you want to compare, they then go to own tabs and you can compare them easier, you also get them in better scale.

[Edited 2013-02-13 11:45:21]


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User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 52, posted (1 year 2 months 18 hours ago) and read 6609 times:

I have now had the time to have a look at the double aisle 220 seater. What I have done is taken the fuselage dimensions from the A310 in AlLi with the modern CFRP wing from our N200. Below is the data, it is now up to others to tell how many pax these 2 frames would take, Ihave highligthed the areas where they differ the most with yellow. I have calculated range, trip fuel etc given that they use the same wing and engines and have the same fuel tanks. The bodies differ in length and width, the N310  have more m2 but a shorter cabin. Use the A310 floor plan to count on how much gets lost in ailes, galleys, entrance areas etc, I have not done it, simply put the pax count at 220 and calculated the thrust and range data with this payload:



A bit about the OEW, the fuselage has 30% more external area (= bigger skins due to larger diameter ), this creates additional skin friction drag (which is by far the dominant drag component) and the finesse ratio is worse, this augments the skin friction drag with the form drag factor which describes the additional speed the air must have to get around this stubbier fuselage. The additional fuselage and floor area also makes the skins, frames, floor beams, floor covers, interior fittings etc larger, therefore the weight of the fuselage goes up. A fuselage structure constitutes approx 20% of the OEW, with a surface increasing with 30% and floor area with 10% I have increased the fuselage structural weight with 15%. All other weights remain the same. This increases the OEW with 2.1t. Then the weight spiral match begins to regain the lost range due to the higher drag and OEW, the way to do that is to increase the MTOW until the range fits equal to N200 (which of course raises the OEW further with the spiral factor), then also the MZFW need to be raised to get the MSP to equal value. Observe that the frame now consumes more trip fuel and that we suddenly are fuel limited where we previously had a margin on 700nm. Finally the changed thrust requirements, our TF42s are still OK but the margins have narrowed, especially V2 is starting to be a bit high:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/N200andN310comparisonthrust_zpscf8f4cb6.jpg

Now for others to add the missing data for the two frames and decide which one we will promote, I have just calculated the bare diffs. I will pluck along with the engines in the meantime with hopefully some help from our experts. I have found quite some data which support Lightsabre's wisdoms above, it will be interesting to dissect.

Edit: there are 2 faults in the tables, V2 is 160kts for the N310, not 165 as the first table says and nacelle length is 6.5m (second table).

[Edited 2013-02-16 12:44:08]


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User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 53, posted (1 year 2 months 17 hours ago) and read 6564 times:

Judging from the lackluster response from airlines for a twin aisle NSA, my belief is the N200 is the way to go for a medium range 180-240 seater.

A few inches wider fuse than the A320 would give 18 inch seats and a wider aisle would aid loading and unloading almost as much as 2 aisles. A single aisle would also cut down on the OEW, bringing all costs down.

What keeps nudging my brain is the plane would basically be quite close to an A322NEO with a longer, (than the 321), Al-Li fuse, a CFRP wing and larger GTF's.



What the...?
User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 54, posted (1 year 2 months 16 hours ago) and read 6564 times:

Hello Ferpe
Before doing some homeworks, some questions :

Cabin length : what does it mesure ? front of door 1 to aft of door 3 (4) ?

5000 Nm is 10 h+ , so it can be an overnight flight, shall we look at 3 class config as follow

Full Bizz : lie flat @ 80 in pitch (2-2 in single aisle) or staggered @ 45 in (1+2 /2+1) : 10 seats
Regional Biz : Cathay regional style @ 47 in "recliner" 2+2, or maybe 2 + 3 in single aisle (http://www.cathaypacific.com/cpa/en_HK/aboutus/pressroomdetails?refID=0cc92f7f9c7f9310VgnVCM62000007d21c39____)
Eco : @32 in

Airliner 200 :
- 40 m cabine -> 1574 in
- 4 doors @ 1 m -> - 157 in
- 4 WC in main cabin (+1 front of door 1) -> - 64 in
- 1 galley front right door 1 + aft door 4

1353 in for seats

9 full biz : 3 * 45
30 regional biz (@ 5 abreast) : 6*47
180 eco (@ 6 abreast @32)

= 219 PAX (9/30/180)

Airliner N310
Cab length : 1315
3 doors : 118 in
1 WC front door 1
4 WC aft door 3 (behind galley) http://www.airbus.com/fileadmin/medi.../tech_data/AC/AC_A310_20091201.pdf (page 34)
1 small galley in front of door 3

12 full bizz (@1+2+1) = 4*45 in
28 regional (@2+3+2) = 4*47 in
208 eco @ 8 abreast @32 in (26*32 in)

= 248 PAX

It's a lot more... (maybe too much)

A few remarks :
Space aft of aft door in widebodies is huge, and can be uses for generous galleys and WC
Space front of front door is also huge.
You need only 3 doors for > 280 PAX ... the A320 needed 4 four doors for 220 PAX exit limit
A330 cross section can be optimised (thinner insulation) for 9 abreast eco with 17" seats (as in 737)
A330 cross section makes underbelly cargo appealin (20 full LD3) and pallets !

What do you think of that ?


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 55, posted (1 year 2 months 16 hours ago) and read 6561 times:

Quoting aviaponcho (Reply 54):
Cabin length : what does it mesure ? front of door 1 to aft of door 3 (4) ?

I have basically taken the A330-200 fuselage and cut it 22 frames a 21'' each, therefore it is bulkhead to bulkhead as far as I know. You can therefore take a -200 cabin and start to rearrange as you like, I am not good in cabin or cabin regulations, therefore number of doors, galleys, classes etc your are the expert. Please advice us all and other will help you who are in the know, I better keep to drag models and early days engines fiddling  .

I am very interested what is all involved in a cabin however so keep on think out loud please  Wow! .

Re cargo, absolutely, the big benefit from the A300, 310, 330, 340 cross section is the LD3 capability, we can thank Roger Beteille for that. AFAIK the 22 frames cut leaves 14 LD3 capacity which is of course is interesting.



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User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 56, posted (1 year 1 month 4 weeks 1 day 18 hours ago) and read 6478 times:

Quoting aviaponcho (Reply 54):
What do you think of that ?

Thanks for all the cabin analysis, I have had time to think of it now and also had a good look at the A310 ACAP (they were so much better then  ). IMO this is 2 different aircrafts, the A200 is a longer A320 just as Joecanuck writes with about a 220 pax capacity, the N310 more like a modern 240 pax true midranger like a 767, A310 (of course    ).

So the N310 is really another class of ship, a midrange ship between the 788 and the A321/739MAX. Guess from a comfort point of view it shall be compared to a missused 788 on midrange legs. If I run both on 5000nm ESAD legs the 788 fuel burn goes down to 44 kg/knm/m2 vs the N310s 43.5 kg/knm/m2. Guess the N310 has to be a lot cheaper to make a business case  Wow!   .

It could be possible however, the price of a frame is a strong function of it's weights, the N310 would be 40t lighter empty, a whopping 90t lower MTOW. The N310 MSP is to low however, 25t vs 43t, it would have to be increased when the frame can take 240 pax.to some 30t. Easily fixed, I just change in the Excel  and ask the structure guys to add a bit of gauge    .

[Edited 2013-02-17 12:35:54]


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User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 57, posted (1 year 1 month 4 weeks 1 day 17 hours ago) and read 6454 times:

I agree, they are not the same birds...

Airliner200 is 200-220 PAX, but I think 10-11 h in a single aisle will be hard.
Do you need a crew rest for 10-11 h flights ? It's easier to hide in a widebody
Galley's will also be eating a lot of space.
It can make a good people mover on short-hop
Twin aisle in the section you chose can make it easier pax wise ...

N310 is a 230-250 PAX (and 300 all eco) bird
N310 can be overkill and is , for short-hop, except if you can load pallets of electronics devices or flowers...
N310 cabin will be easier to taylor to customer's wish ... and with 2 aisle you are not stuck with 6 abreast, ou can go 8 or 9 if you want to squeeze pax.

By the way, can you model the A400M ? In a 2 deck layout it's a 200/240 Eco pax mover...  


User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 58, posted (1 year 1 month 4 weeks 1 day 17 hours ago) and read 6450 times:

I might have been to generous with the N310 LOPA !
Indeed A310 was 14/15 LD3 or 3 Pallets + 6/7LD3
I'll check this week for N200 and N310

[Edited 2013-02-17 14:24:48]

User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 59, posted (1 year 1 month 4 weeks 1 day 9 hours ago) and read 6408 times:

I think what we're looking at is the elusive son of 757. I think the problem with a twin aisle the size of the N310, is that the 788 already basically owns that space, and what it can't get, the 330, (which is still getting better all the time), will pick up.

It seems the only real gap left over 150 seats is what that darned 757 is occupying. The 321 is creeping that way but it would take at least a rewing job to improve it much more.

My gut has me steering the N200 into that space...maybe getting it up to an 8000nm people mover, maybe capable of hauling around some single LD3's...if that's even possible.

Lots of wing and the nifty new engine being created here. I still lean towards a high wing plane but that's just because I think the An-158 looks pretty darned cool. That being said, there are advantages to a high wing which could set this plane apart from any competition. It would be better on less improved runways and might just be the ticket for non first world nations looking for a trans continental people mover.



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 60, posted (1 year 1 month 4 weeks 8 hours ago) and read 6325 times:

Quoting aviaponcho (Reply 57):
By the way, can you model the A400M ? In a 2 deck layout it's a 200/240 Eco pax mover...

Not really, I don't have the aerodynamic constants for a high wing turboprop frame so it would be a lot of work. I got these from textbooks and the Stanford areo course http://adg.stanford.edu/aa241/AircraftDesign.html . That is the advantage with the present boring lineup, they are all almost identical, to the point where the constants are all very similar, here the table with constants for the frames in question, row 117-127. The higher fuselage pressure drag factor for the N310 has the cursor on it :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/Airliners200areodata_zpsc1e203ba.jpg

These are then put in the equations for the different flight levels (the excel has all odd FL from 310 to 410) and for e.g. cruise, the flight level with the best NAMS and an acceptable Cl (between 0.5 and 0.55 for most frames) is chosen for the cruise range calculation (our cruise level FL370 shown here at row 162-178) . The L/D, TSFC, TAS etc for this FL goes into the range calculation.



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User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 61, posted (1 year 1 month 4 weeks 4 hours ago) and read 6301 times:

Ferpe
Is the N200 fuse circular ? you show : width 4.2 m diameter 4.1 m height 4.01 m, but 4.01 m is the same as 757-200 height...

I've done some homework

Same layout as last time
Full business: staggered lie flat : @46 in
1-2 / 2-1 layout in A321 / N200 single aisle et 1+1+1 in twin aisle layout
1-2-1 layout in N310 /a310


Business : recliner (cathay business regional) @ 46 in
2+3 layout in A321 et N200 single aisle
1+3+1 in N200 twin aisle
2+3+2 in N310 / A310
Seat width 20/21"

Eco
3+3 @ 32 in A321 et N200 single aisle
1+4+1 @ 32 in N200 twin aisle
2+4+2 @32 in N310 /A310
Seat width 17-19"

Usable cabin length = length between axis of front and aft door - 2 * half door width - margin - intermediate door (25 in cross aisle for the moment)


You need at least 6 WC (1/15 in biz and 1/45 in eco) and 25-30 trolley galley for 5000 Nm mission

Let's go for 5 for the moment

A321/N200 : 1 front / 2 mid / 2 front of aft door : freezing 2*37 in of cab
N310 /A310 : 1 front and 4 WC in the aft galley

Std galley
A321 front 4 trolley aft : 7 trolley = 11 (missing 14 trolleys)
N200 front 5 trolley aft : 8 trolley = 13 (missing 16 trolleys)
A310 front 5.5 trolley aft : 8 trolley = 13 (missing 16 trolleys)

TOTAL with a lot of missing galley position

A321 : 9/30/126 = 165
N200 : 9/30/168 = 207
A310 : 12/28/176 = 216
N310 : 12/28/184 = 224

For A321/N200 : you get 4 trolley position in exchange of a triplet ... as you're missing 14/16 ...you need 2*34 for galley + increase cross aisle at door = 2*34+36 = 104 in

For A310/N310
Aft galley with = 2*8 Full size trolley = 16
Front rear door center galley is 4 trolleys + 2WC side WC
Mid Cab galley 5 trolleys + 2 WC
Front Galley = 5.5 + 1WC

= 30.5 trolleys + 5 WC, cabin length - 68 in + increase cross aisle = 104"
I know how to plan WC an galley's fort A330 and so for A310, but not for A320


A321 : 9/30/114 = 153
N200 : 9/30/156 = 195
A310 : 12/28/160 = 200
N310 : 12/28/168 = 208

All that without crew rest... (compartment or dedicated seats in main cabin)
And for N200/A321 with 3 pair of doors

With a similar layout, A330-200 is at 290 PAX (same front cabin) and A350-900 is at 370-390 PAX

So what now ?

For sure, in a comfortable layout and with 10-11 h mission possible N200 is sub 200 PAX
No growth version possible as it's the last stretch of the single aisle. If it'is acceptable you can make a family of two beginning at between A320 / A321 fuselage length

A310/N310 are above that mark, you can't go smaller than A310 (it looks weird, and there's a lot of waste space at the rear), but you can grow it to A300 fuselage length... but TF42 might now be short... (or not as payload as indeed shrunk).


User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 62, posted (1 year 1 month 4 weeks 3 hours ago) and read 6287 times:

I can't edit

So I add 787-8 PAx count estimate with the same layout : 290-300 PAX (12 full flat biz / 28 régional biz) and a N300 with the same A300 fuselage length is a 240-250 pax bird

So let's sum up
All layout with 9 / 12 full flat biz, 28/30 regional biz and the remainder in eco @32 in with mediu/long range galleys, low WC count and no crew rest.
It's not a detailled layout as well (staggered biz is tricky due to front row monument)
So seat count is +/- 10 at least

A321__ 153 PAX (09/30/114)
N200__ 195 PAX (09/30/156)
A310__ 200 PAX (12/28/160)
N310__ 208 PAX (12/28/168)
A300__ 248 PAX (12/28/208)
A330__ 296 PAX (12/28/256)
787-8__ 301 PAX (12/28/261)
A350-9 391 PAX (12/28/351)

There's room for a new gen A300/A310 familly with an optimised narrowed cross section (as long as 2*LD3 side by side can be put underbelly)


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 63, posted (1 year 1 month 3 weeks 6 days 6 hours ago) and read 6207 times:

Quoting aviaponcho (Reply 62):
There's room for a new gen A300/A310 familly with an optimised narrowed cross section (as long as 2*LD3 side by side can be put underbelly)

I've read it all with interest, we should have had someone like LAXDESI who could do a revenue-cost scenario of it all, don't know if you can make it (that is not my specialty for sure   ) .

Otherwise, in general terms which frame would be the better earner? We see that the DA would consume some 10% more fuel on a block basis but -10% on a m2 basis. You also reach the same conclusion, the N310 takes 7% more pax in a more comfortable cabin, there also seems to be a shade more of premium in the earnings mix.

The N310 is heavier, therefore cost more to produce (probably within 10%), now the big question is which frame would be preferred by the airlines. I tend towards N310.

Re engine thrust etc, it is a rubber engine right now  , we are still free to change it to suit our aircraft. Lets find the right aircraft config together, then I will calculate the thrust required according to the mission table and then we design and engine that fits    .

Re fuselage cross section, the A300 cross section was the minimum that would fit 2 LD3, that was the design brief from Beteille, therefore I don't think we find a better cross section easily. Re the N200, it is oval, very few fuselages are circular today except for the 777 and it flies a lot of air in it's crown.

[Edited 2013-02-20 00:47:57]


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User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 64, posted (1 year 1 month 3 weeks 6 days 6 hours ago) and read 6202 times:

Thanks

If you go developping a new airframe you must think "derivatives" / "family"

For N2XX :
N200 : 50 m fuse / 190-200 PAX 3 class / 250-260 PAX one class (@28-29 in) @ 5000 Nm
N210 : 42 m fuse / 140-150 PAX 3 class / 200-210 PAX one class (@28-29 in) @ ???? Nm @MTOW ?
Freighter ?

For N3XX
N310 : 47.1 fuse / 210-220 PAX 3 class / 270-290 PAX one class (@28-29 in) and 8 abreast (or idem with 9 abreast and 32 in pitch) @ 5000 Nm
N300 : 55 m fuse / 250-270 PAx 3 class / 340-350 PAX one class (@28-29 in) and 8 abreast @ ???? Nm
Maybe you can go further (N330-200 ?)
N300/N310 Freighter are probably a valuable derivative as well !

The next closer airplane is 787-8 is 300 Pax 3 class / 381 PAX high density (exit limit)


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 65, posted (1 year 1 month 3 weeks 5 days 23 hours ago) and read 6168 times:

Quoting aviaponcho (Reply 64):

Not only family, I think it's important to look at market positioning as well. The n 300 series really doesn't have much room in the marketplace.The 788 and the 330 pretty much do everything The N 300 would do on the top end and the767 hems it in from below

Of the two, I believe The N 200 hits a segment completely free from new build aircraft and so presents the best opportunity to create something that has the best chance to sell

Ultimately, we're talking about the choice between a 757ng or an a300ng.



What the...?
User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 66, posted (1 year 1 month 3 weeks 5 days 23 hours ago) and read 6173 times:

Quoting JoeCanuck (Reply 65):
Ultimately, we're talking about the choice between a 757ng or an a300ng.

Yes that's what's being discussed.
The 787 and the A330-200 a much bigger than A310/A300
There's a true gap, N200 addresses the low end and overlap with current single aisle if shrinked, but with a lot more range.
The N310/N300 addresses the upper end of the gap.

it's up to FERPE now and it's customers  

And versus the 767, we're talking of a 20-25% more fuel efficient airplane although it's smaller


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 67, posted (1 year 1 month 3 weeks 5 days 22 hours ago) and read 6163 times:

Quoting aviaponcho (Reply 66):
it's up to FERPE now and it's customers

   Hold your horses, WE are all in this together      .

We trash out what we think can be sold in the market (and with WE I mean everyone at Airliners.net, not just me, Poncho and Joe), I am just the guy with the engine design tool (having fun  ) .

We can make a suitable engine in a whim once we have decided what we think we can sell, lets dig deep with this discussion. I am progressing with the engine side (ie understanding what to change in GasTurb to get to 0.54 TSFC and 2% below because we loose that once installed in the nacelles ) in the meantime.



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User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 68, posted (1 year 1 month 3 weeks 5 days 18 hours ago) and read 6143 times:

You are also the chief aero designer Ferpe  
Going N310 implies building some margin in your (our ?) TF42 ... going all the way to 50 klbs ?
Going N200, TF42 is all right i think


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 69, posted (1 year 1 month 3 weeks 5 days 10 hours ago) and read 6100 times:

Quoting ferpe (Reply 67):
Hold your horses, WE are all in this together

Indeed...and it's been a very interesting thread so far...at least for me. It's bloody refreshing to be able to discuss different opinions freely without retribution or rancor.

I definitely rely on the technical expertise of others but it's fun to play along.



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 70, posted (1 year 1 month 3 weeks 4 days 20 hours ago) and read 6036 times:

Quoting aviaponcho (Reply 68):
You are also the chief aero designer Ferpe

Might be, but as for all products: what is important is what would sell   .

Now which one of the N200 and N310 would bring in the most revenue and margin to our Airliners.net aircraft and engine company? And to help the debate, lets put a price tag out there:

- Airliners-N200, 130m$

- Airliners-NJ310, 145m$

We will give some rebate on these prices for well known and solvent customers  Wow! 


I'm certainly divided to which we shall launch, others ?

[Edited 2013-02-21 11:14:54]


Non French in France
User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 71, posted (1 year 1 month 3 weeks 4 days 17 hours ago) and read 6024 times:

Hard to tell !

Maybe in the real life Boeing will do the N200 family (with LeapGenX) and Airbus the N310 Family with GTF
Hum why not replace Boeing by Bombardier :
Maybe in the real life Bombardier will do the N200 family (with LeapGenX) and Airbus the N310 Family with GTF

Boeing had 7J7 for 2020 and onwards (waiting for openrotor and capitalising on maddogs experience)

 


User currently offlineAircellist From Canada, joined Oct 2004, 1628 posts, RR: 8
Reply 72, posted (1 year 1 month 3 weeks 3 days 14 hours ago) and read 5930 times:

Not following everything in detail, but that's one pleasant thread!

User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 73, posted (1 year 1 month 2 weeks 5 days 17 hours ago) and read 5701 times:

Some might think things have gone quiet but I have been poking around   . After the initial design and the good comments from Lightsaber I thought I better go learn some things  , here goes:


   DDTF vs GTF
First a statement by Kurzke, he was head of the MTU performance side when the GTF was developed between PW and MTU and I find this synopsis from his presentation at the ASME conference June 2009 very interesting:

   Fundamental Differences Between Conventional and Geared Turbofans
"...........The result of the integrated aero-thermodynamic and mechanical study allows a comparison of the fundamental differences between conventional and geared turbofans. At the same bypass ratio there will be no significant difference in specific fuel consumption between the alternative designs. The main difference is in the parts count which is much lower for the geared turbofan than for the conventional engine. However, these parts will be mechanically much more challenging than those of a conventional turbofan. If the bypass ratio is increased significantly above 10, then the geared turbofan becomes more and more attractive..."   

This is exactly what happened when I just transfered the TF42 BPR9 DDTF design to a BPR9 GTF design, the TSFC remained the same, the part count in the booster, HPC and LPT reduced and the gearbox complexity was added. Then with higher spinning booster and LPT they went heavier per stage as they had more elaborate high stress designs.

Before now taking the next steps to higher BPR GTFs I wanted to understand how to load and spec the different parts of the turbomachinery correctly. It was clear I was not doing it right, CFM and PW/MTU used 2 HPT and I only 1 (guess who is wrong  Wow! ). So I started to study stage loading and other stuff. Here some findings going from front to back in the engine:



   FANS and COMPRESSORS
These have developed a lot over the last 30 years, see pictures from this paper by MTU (German): http://www.mtubrasil.com/de/technolo...ridchter_Schluesseltechnologie.pdf

This picture shows nicely what has happened with compressors over the years
http://i298.photobucket.com/albums/mm262/ferpe_bucket/Compressorsdevelopment_zps6b9d0d69.jpg

and this picture shows why you can now get about 2 times PR from a compressor stage, you can simply run it at higher speed, up into supersonic streams on the outer half:
http://i298.photobucket.com/albums/mm262/ferpe_bucket/Compressorsstageloading_zpse5333739.jpg
Note that the outer part of the fan / compressor blade then looks more like a Starfighter wing then a normal subsonic wing.

Also one has to understand why software like Gasturb ask you for outer and inner fan pressure ratio and efficiency:
http://i298.photobucket.com/albums/mm262/ferpe_bucket/Fanradialprofileswithannotations_zpsc8b2f4b9.jpg
This is because these values differ between the fan inner and outer part. It comes from the fan blade going with lower radial velocity on the inner part = lower pressure gain but little disturbance from a rotor wall which moves with the blade, thus good efficiency. On the blades outer part (where you have high speed = high pressure gain) the supersonic flow creates shocks which reduces the pressure gain and efficiency. Also because the outer end of the fan meets a wall that stands still and there is a gap between blade and wall you get local lower pressure and efficiency. So it all adds up to about 10% higher fan pressure ratio on the outer end (around 1.6 vs 1.45) and 5% lower efficiency (say 88-90% vs 92-93% at the inner end ).

In general the boosters have PR of 0,5-0,7 per stage and a true IPC like on a GTF or triple spool engine has around 1.5 as they are not chained to the low RPM of the fan. The new GE and PW HPC has a max PR of around 2 per stage but then they don't give you max efficiency. That top of the compressor efficiency hill at around 92-93% (see the maps in earlier posts) is reserved for cruise RPMs where you are at around 1.7 in pressure gain per stage today.



   TURBINES
The Gasturb manual shows this picture:


So to specify a 1 stage HPT which drives a HPC with 8 stages and PR 16 is doable (gives you PR 4 for the HPT) but you want get a 90% efficiency out of it, and this is what we need. So we need to go to a 2 stage HPT  Wow! .

Further this picture from a DDTF and GTF LPT is illustrative, the GTF is has less parts but boy are they harder stressed, look at the rims which are within the red circles (the rims are further central then the blade attachment rings ) :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/DDTFvsGTFLPTs_zpsb9d7ff97.jpg

   So much to think about, I am also looking into regulating the cooling flow (you don't need full cooling except for TO when T41 is max, why not reduce the flow in other flight modes), it seems only the TXWB does it in practice. Why, seems like an easy gain and should be easy to throttle this bleed   .



   MATERIALS
Finally a nice picture from the Leap and how it uses advanced materials to lower weight and reduce cooling flow:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/Leapmaterialadvances_zps43d6b949.jpg

So CFM uses CFRP and TiAl to reduce weight and CMC to reduce cooling requirements on the HPT stator rim, all helping the LEAP weight and efficiency.

[Edited 2013-02-27 15:21:11]


Non French in France
User currently offlineaviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 74, posted (1 year 1 month 2 weeks 1 day 4 hours ago) and read 5474 times:

So what ?
You need to rework the TF42 ?
Did you make you mind on N200 or N310 ?


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 75, posted (1 year 1 month 1 week 6 days 19 hours ago) and read 5386 times:

Quoting aviaponcho (Reply 74):
Did you make you mind on N200 or N310 ?

Well I tried to get others to chip and help us with the choice, perhaps we are to serious with all these numbers, it is just having a bit of fun speculating what could have been  . If no-one else want to give his    I would go for the N310 simply because it has more potential for the increasing traffic densities we will see in the next 40 years. When one design an airliners one is crystal-balling far out, really far out  Wow! .

So if we go for the N310 we can see it as a A330 body which is shortened and build of AlLi in the parts that can be changed to AlLi. It would keep the nose and tail, but the wing and engines would be new as would many systems which can be updated to latest component standards.

Quoting aviaponcho (Reply 74):
You need to rework the TF42 ?

Sure, but before that I want to explain why I am nagging so much on the efficiency's of the fan, compressors and turbines. The all sum up to the cycle efficiency (other parts contribute as well but they are all close to 98-99% like the burner and ducts) shown in this diagram:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/OverallcycleefficiencyforaTF_zps236a986f.jpg

This whole diagram is drawn for a Burner temp to inlet temp (T4/T2) of 5.5, increase T4 and the diagram changes slightly. As can be seen if you have an engine where the sum of the efficiency are below 90% then there is no point aiming for a pressure ratio over 25-30 in cruise (it is always the cruise conditions which are important, especially for a medium to long haul aircraft. For a short hauler the climb efficiency is starting to weigh in as well). Why this displacement of the optimum pressure ratio with component efficiencies?

It is not to hard to understand, we all know from our cars that a diesel which has a higher pressure ratio (PR around 18, called compression ratio for a car) is more efficient then a gasoline engine (PR around 10). So a high compression into the burner is good. But compressing air takes work and this work shall be delivered by our turbines. They suck the energy for this out of the burned air, then turn the engine shafts to turns the compressors. If the waste along this chain is to high it takes more energy out of the burned compressed air then a higher compression would gain us, i.e. we have reached a point when the whole thing goes downhill.

As can be seen the max efficiency is around PR 35-40 for a modern long range engine with advanced compressors and turbines all lying around 90% and above. It is a bit easier to get turbines over 90% then compressors so therefore the dotted line example where the turbines are 95% and the compressors 85%. The new engines proposed for the 777X has a PR of 60, does this mean their components all push 95%? No, as said the performance peak should be adapted to cruise, we can be pretty sure these 60 are Top of Climb and that cruise lies around PR 45. Thus we can expect their average efficiencies to lie around 93-94%, pretty darn good anyway  Wow! .



Non French in France
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 76, posted (1 year 1 month 1 week 6 days 18 hours ago) and read 5380 times:

Quoting ferpe (Reply 75):
I would go for the N310 simply because it has more potential for the increasing traffic densities we will see in the next 40 years.

I went the other way with the N200. My crystal ball, (cracked and cloudy as it is), sees a real potential for a 180-240 seat single aisle, low seat mile cost, good ranged, point to point people mover, for those long, thin, (much like the plane would be), routes. I put less emphasis on cargo.

I see it not so much as a hub buster, as a hub complimenter. The hubs make a lot of sense for the densest routes but there are a lot of large cities that may be able to support smaller direct flights. Basically, a super 757.

Same size, TF42 engines, long CFRP wing, Al-Li where ever possible and the weight savings could go into fuel load. That combined with the efficient engines, could give maybe 7000nm range, opening up currently uneconomical point to point routes.

I put cargo as a secondary consideration since it doesn't care how many stops it makes and there are huge spiderwebs of connections for cargo to go from anywhere to anywhere else, but it does matter to passengers, so that is the niche I'd fill.

In comparing the a310 to the 757, for about the same passenger load the 757 has about a 20,000kg lighter OEW. If we made the fuse wide enough for at least 18" seats with the widest part of the fuse at shoulder height, I think we'd end up with a very comfortable long(ish) range, very efficient, point to point people mover.



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 77, posted (1 year 1 month 1 week 6 days 6 hours ago) and read 5337 times:

Let me run home one more thing about this efficiency thing, not only does it affect how high it makes sense to run the compression in the engine, it also affects other things    .

As I described above the Top of Climb is the aerodynamic design point of the engine, this means the thin air makes this the condition that determines how we must size the things that creates the flow through the engine, i.e. fan, ducts, the compressors etc, in short the aerodynamic path. It therefore also determines the size of all the parts, it determines the physical size of the engine.

   It is not the mechanically most stressing point however, that is Take Off. The physical stresses on the parts and the temps are here the highest as the air is denser (and consequently the engine puts out some 40klbf instead of 9.6 at height so no wonder it is more stressing) and warmer (we hit the max T41 here and let it only churn on our hot parts for 5 minutes max, a whopping 3400R / 2000F or 1600C ). The parts making the compression possible has to work for the keep as well, the HPT takes 600 psi and produces 40,000 hp !!! down the shaft to drive the High compressor and the LPT is even cockier, he takes the pressure left from the HPT (150 psi) and produces 45,000 hp to drive the IPC/Booster and fan, on his downside he only leaves 20 psi (0.140 kpa) for the core exhaust.

The 90sih % efficiency of these parts mean we leave around 10% on the table, that is some 4000 hp that goes to heat. Improve that with 2% and you have gained 800 hp equivalent in heat that you can have in shaft power or alternatively (if you don't need more hp ) you can squirt less fuel into the burner and get lower temps all the way back    .


Lower temps for the back part of the core means we can go from Ni super alloys earlier to the TiAl parts described in the CFM slide, gaining cost and weight (Ti is easier to manufacture then Ni super alloy parts). The same applies to the compressor side, more efficiency means we generate less heat when we compress and we can keep TiAl based BLISK (machined from one piece) rotors longer once again gaining cost and weight. So no wonder the big guys all do a lot of research into more efficient fans, compressors and turbines, finding something creates a triple whammy   .


Note: One realizes making that small and light gearbox for the GTF is not trivial, it shall reliably transmit a big part of that 45,000 hp to the fan. 45,000 hp gearboxes we find on ships or trains but that is kind of other dimensions  Wow! 

[Edited 2013-03-06 00:50:01]


Non French in France
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 78, posted (1 year 1 month 6 days 5 hours ago) and read 5087 times:

I've been mulling over this topic for a while and I keep coming back to a plane that is still in production, (and one I like flying on), which could suit all purposes, (long and thin routes, cargo and passengers, point to point)...the 767-200.

It's a great people hauler and can handle those little containers. It's weight and passenger loads are just about perfectly placed between the 321 and the 788.

Instead of a 767NG, I can see a 767-2x. A GTF engine designed from the outset for 60,000lbs thrust, not just a detuned GEnx or T-1000. Maybe some wing work, (maybe a lighter duty 788 wing), and some Al-li skin on the fuse. From a practicality standpoint, it would be easier to get this into service than something all new.

Just the one size, not compromised by future stretches or shrinks.

7 abreast is much better than single aisle for comfort and the OEW should come in at least 60,000 lbs lighter than the 788, giving it some pretty serious economics.



What the...?
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 79, posted (1 year 1 month 2 days 16 hours ago) and read 4894 times:

Lets finish the TF42 GTF engine before we go to 3 spool variants (to learn about the principal differences between DDTF, GTF and Tri Spool ones) and then also attack the different aircraft proposals more deeply (SA, DA 310 copy and a 767 copy), here a GTF that would fit our requirements:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42-GTFBPR12optimized_zps505164a9.jpg

As can be seen it is a higher BPR engine (12 at ToC) and therefore consumes less fuel on a bare engine level, what it means on an aircraft level we will look into later. It is also stronger at TO but is down at 15klbf already at FL100 whereas our BPR9 GTF was still at 16klbf at FL160, all consistent with a higher lapse ratio for a higher BPR engine. Forget about the "minimal adaptations" in the first line of the table, this should have been changed to "optimized" as I have now changed e.g the high turbine to 2 stages and run all compressors and turbines in a global optimization vs the burner temp. I have done this within the limits of a modern core technology level but without going to bleeding edge technologies like GEs Leap (ceramics, CFRP fan and fan case), a bit like PWs GTF.

Here the working line at FL330 and normal cruise M :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42GTFBPR12workingline_zpseb26ab13.jpg

Observe how TSFC, PR and BPR changes with throttle position and therefore N1. That we don't gain TSFC by higher BPR for nothing shows this dimension extract from GasTurb, we are now at 105'' and 11700lbm instead of 94'' and 10000lbm for the DDTF:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/TF42GTFBPR12enginedimensions_zpse70c60a9.jpg

It is essentially an engine which is very close to a A320neo PW GTF, it is 30% larger, has a bit more pressure ratio (52 versus 45-50) and about the same turbine temps. It has a fuel consumption close to a T1000 and GEnx-1 as a bare engine, a tad lower then the PW neo engine.

[Edited 2013-03-16 16:01:05]


Non French in France
User currently offlineAviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 80, posted (1 year 1 month 1 day 18 hours ago) and read 4801 times:

Hello Ferpe
Wasn't the variable area nozzle a way to increase climb thrust ?
It's on the PW1500G and the PW1100G if i'm not mistaken

Regards


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 81, posted (1 year 1 month 10 hours ago) and read 4728 times:

Quoting Aviaponcho (Reply 80):
Wasn't the variable area nozzle a way to increase climb thrust ?

Here is how I understand the issue of variable Turbofan nozzels:

A turbofan nozzle is designed to give the engine fan optimal working conditions for the all important cruise phase, ie something like M 0.8 and 11 km. This gives the fan less the optimal conditions at lower speeds and lower throttle settings, the nozzle is to tight and gives to much backpressure forcing the fan close to the surge line, see fan map above.

Very high bypass ratio and low pressure ratio fans are more sensitive in this respect and can depending on working line optimization require a nozzle that reduces backpressure at low speeds and low throttle positions, the PW GTF has foreseen such a nozzle but seems to have been able to avoid the complexity on at least the C-series.

The normal climb speed is at or close to cruise speed thus the nozzle would be at it's cruise poistion, as I understand it the open position would be called for at start and landing rather.



Non French in France
User currently offlineAviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 82, posted (1 year 1 month 1 hour ago) and read 4673 times:

For the Cseries, You're right it has been dropped (-> it wa supposed to permet 2% fuel burn gain !)
http://www.goodrich.com/gr-ext-templ...t%20Aerostructures/SKY09262012.pdf
http://www.goodrich.com/gr-ext-templ...0at%20Aerostructures/SKY021313.pdf
PW1200G hasn't due to less By Pass ratio

http://www.flickr.com/photos/2544039...8362179129/sizes/o/in/photostream/



What I understand (I can't find the flightglobal link)

3 positions

Take Off : open
Climb : closed : position 1
Cruise : closed ;: position 2

I can't remember if position 1 is narrower than position 2 or the other way ?

Still it might help the PW1100G for top of the climb

Have a nice day


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 83, posted (1 year 4 weeks 1 day 18 hours ago) and read 4621 times:

Great stuff Poncho, thanks for the research    .

This variable nacelle stuff in really interesting. When you design a civil turbofan engine one critical area is the nozzles for the bypass and also the core part. The key is to get the speed and pressure profiles right for the different flight modes, to get the most efficient engine possible.

- One aspect is your speed profile out the back, you only have a 0.18 M overspeed possible off the flow at an aircraft speed of M0.82 as the airstream out of convergent nozzle can't pass M 1.0 (it chockes and then the Mach does not change, only pressure and temp change after the nozzles chockes). So you want to make the nozzle tight enough to get to this optimal speed profile for cruise.

- On the other hand the nozzle shall be large enough not to bring the fan to stall at low speed and RPMs ie not give the fan a hard time with high backpressure when the fan is struggling close to the stall point (the fan airfoiles at low speed meet the air with the fixed high angle of attack blades designed for cruise = they are close to stalling ).

The end result is a compromise that cost some efficiency at cruise as a stalling fan is a NO NO at part throttle when starting and landing. A variable nozzle can improve this situation but it cost complexity. As said this compromise gets tougher the higher BPR and the lower pressure ratio the fan has, that is why the higher BPR GTF for A320neo will keep the variable nozzle nacelle that UTC aka Goodrich have developed for the PW GTF.



Non French in France
User currently offlineAviaponcho From France, joined Aug 2011, 581 posts, RR: 8
Reply 84, posted (1 year 4 weeks 1 day 16 hours ago) and read 4603 times:

Ferpe, officially BPR for PW1500G and PW1100G is 12:1, no change in BPR (at which thrust setting ?)
What can be harder for the PW1100G is the thrust range that is wider ... (ah ah A321NEO !)
In anycase, on the PW1500G, PW didn't need the VAFN for improving the consumption, the noise and the stall margin ... in the same time, the CS300 became heavier... a lot of margin in these 2 programs

Have a nice day


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