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Next Gen NB Engines : Contra Rotating Turbofan Fan  
User currently offlineKeesje From , joined Dec 1969, posts, RR:
Posted (6 years 12 months 16 hours ago) and read 11048 times:

Snecma is looking at contrarotation fan as an option for next generarion Narrowbody aircraft.



Wonder how GE thinks about it.

RR (3 spool) and Pratt (GTF) are also testing the water. I wonder what they will say at the Paris Airshow.

http://www.flightglobal.com/articles...uture-engine-concept-revealed.html

[Edited 2007-04-27 13:26:46]

36 replies: All unread, showing first 25:
 
User currently offlineJAAlbert From United States of America, joined Jan 2006, 1492 posts, RR: 1
Reply 1, posted (6 years 12 months 16 hours ago) and read 11009 times:

Very interesting. (I think). Those fan blades rotating in opposite directions should have a very effective garbage disposal effect should any bird find its way into the engine!

User currently offlineSEPilot From United States of America, joined Dec 2006, 6682 posts, RR: 46
Reply 2, posted (6 years 12 months 15 hours ago) and read 10987 times:

I am not an expert in jet engines, but just from basic physics and engineering principles the idea is fascinating. The idea of eliminating the need for fixed blades by having contrarotating blades has enormous potential, as well as substantial difficulties in getting it right. If they can do it and get it right it will be a magnificent acheivement. The next step for ultimate efficiency would be a geared contrarotating fan. Anyone seen Rube Goldberg lately? Oh, that's right, he's dead. Summon his ghost, the industry needs him. Seriously, it would be enormously difficult to make a geared contrarotating engine reliable enough, but if it could be done it would be the holy grail of jet engines.


The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 3, posted (6 years 12 months 13 hours ago) and read 10743 times:

You're up early Keesje....a most interesting article on a very timely subject.

On the subject of ultra high bypass fan engines I worked on a few Garrett ATF3s back in the day. They were used on the USCG HU25A and the French Navy equivalent, mating the engine to a modified Falcon 20 airframe. There was an extensive teething process with numerous service bulletins which required some of the mechanics to go to the airplanes and modify the engines. One of our guys spent seven weeks in Tahiti on that show.

The original task was to produce a very efficient engine with very low IR signature for a high altitude pilotless drone that Teledyne Ryan was going to build-which sounds a lot like Global Hawk.

That project got shelved but the ATF3 eventually got built. There was some internal dissension within Garrett as the ATF3 was a Torrance design and all the other engines came out of Phoenix. Well, I could be wrong about that part of it because it has been about 25 years
.
The ATF3 turned the airflow a bunch of different ways and ejected its exhaust into the fan air path midway through stacks. It was said that the ATF3 produced 93-95 per cent of its thrust from the fan, and it was a three spool engine.

Ultimately the ATF3's efficiencies were attained using 70s technology and materials, which was a very expensive way to do it. New materials and processes allowed simpler and less expensive engines to reach the same high degree of fuel economy.

There is a very interesting ATF 3 site that is worth a trip, particularly the part about the Tacit Blue engines and how they disappeared and reappeared..

http://www.pocketprotectors.com/atf3/index.htm

http://www.area51zone.com/aircraft/tacitb.shtml


User currently offlineDAYflyer From United States of America, joined Sep 2004, 3807 posts, RR: 3
Reply 4, posted (6 years 12 months 12 hours ago) and read 10640 times:

A very intersting subject indeed, Keesje.

I work for a company that manufactures high speed turbine impellers for commercial applications. Couter-rotating is indeed possible, but tricky. But let me tell you, the ones we have done here for non-aircraft use move HUGE volumes of air at tremendous speeds. I wonder what engineering problems and success they are having with this at Snecma??



One Nation Under God
User currently offlineN328KF From United States of America, joined May 2004, 6482 posts, RR: 3
Reply 5, posted (6 years 12 months 11 hours ago) and read 10567 times:

Quoting SEPilot (Reply 2):
Seriously, it would be enormously difficult to make a geared contrarotating engine reliable enough, but if it could be done it would be the holy grail of jet engines.

Don't propfans contrarotate?



When they call the roll in the Senate, the Senators do not know whether to answer 'Present' or 'Not guilty.' T.Roosevelt
User currently offlineScbriml From United Kingdom, joined Jul 2003, 12041 posts, RR: 47
Reply 6, posted (6 years 12 months 11 hours ago) and read 10526 times:
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Call that contrarotatring?

These bad boys are contrarotating at its finest:

View Large View Medium
Click here for bigger photo!

Photo © Steve Brimley
View Large View Medium
Click here for bigger photo!

Photo © Steve Brimley


 wink 



Hey AA, the 1960s called. They want their planes back!
User currently offlineSEPilot From United States of America, joined Dec 2006, 6682 posts, RR: 46
Reply 7, posted (6 years 12 months 11 hours ago) and read 10487 times:

Quoting N328KF (Reply 5):
Don't propfans contrarotate?

Contrarotating is not that difficult as far as shafts/bearings are concerned; what is difficult is the blade contours. Contrarotating between a prop and a turbine is easy; it is geared anyway. The difficulty starts when you gear between the fan and turbine within the engine; first, where do the gears go and second, how do you make them reliable enough? That is what P & W is working on, and as I understand it it is not easy. Then add a contrarotating shaft in there that also needs to be gearded and you have just squared or cubed your problems. I'm not at all sure that it can be done.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently onlineTristarSteve From Sweden, joined Nov 2005, 3930 posts, RR: 34
Reply 8, posted (6 years 12 months 11 hours ago) and read 10468 times:

[quote=SEPilot,reply=7]Contrarotating is not that difficult as far as shafts/bearings are concerned; what is difficult is the blade contours. Contrarotating between a prop and a turbine is easy; it is geared anyway. The difficulty starts when you gear between the fan and turbine within the engine; first, where do the gears go and second, how do you make them reliable enough? That is what P & W is working on, and as I understand it it is not easy. Then add a contrarotating shaft in there that also needs to be gearded and you have just squared or cubed your problems. I'm not at all sure that it can be done.[/quote

Why not have two HP turbines, with two stages on each, each driving one fan. Then you don't need any gears.?


User currently offlineJustloveplanes From United States of America, joined Jul 2004, 1002 posts, RR: 1
Reply 9, posted (6 years 12 months 11 hours ago) and read 10445 times:

why are so few prop applications counter-rotating?

User currently offlineSEPilot From United States of America, joined Dec 2006, 6682 posts, RR: 46
Reply 10, posted (6 years 12 months 10 hours ago) and read 10412 times:

Quoting Justloveplanes (Reply 9):
why are so few prop applications counter-rotating?

In a nutshell, cost and complexity. Howard Hughes's plane that crashed (I forget what the model was) had counter-rotating props, and the failure of one of them is what caused the crash.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineDfwRevolution From United States of America, joined Jan 2010, 915 posts, RR: 51
Reply 11, posted (6 years 12 months 10 hours ago) and read 10394 times:

Quoting Keesje (Thread starter):
Snecma is looking at contrarotation fan as an option for next generarion Narrowbody aircraft. Wonder how GE thinks about it.

What must really be on their mind is the future of the CFMI partnership...


User currently offlineLightsaber From United States of America, joined Jan 2005, 12430 posts, RR: 100
Reply 12, posted (6 years 12 months 10 hours ago) and read 10309 times:
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Quoting Keesje (Thread starter):
RR (3 spool) and Pratt (GTF) are also testing the water.

Pratt proposed one for the Sonic Cruiser.  bigthumbsup 

Quoting SEPilot (Reply 2):
Seriously, it would be enormously difficult to make a geared contrarotating engine reliable enough, but if it could be done it would be the holy grail of jet engines.

 checkmark 

Hence why Pratt is focused on the simple GTF. But is this a concept of high merit? Yes!

Quoting TristarSteve (Reply 8):
Why not have two HP turbines, with two stages on each, each driving one fan. Then you don't need any gears.?

But that is effectively a triple spool without the benefit of getting the turbine's mach number into its optimal range. The current triple spool has higher efficiency than your proposal. Why? By having the intermediate spool turbine and compressor spinning at their optimal mach number (which must be at a higher RPM than the fan based on diameters and temperature increases to compression heating) the engine gains in efficiency.

Should this be done long term? Yes! But we're talking engines in the 2020 timeframe.  Sad This is pretty far out technology.

Short term I'm still a fan of the GTF. This concept is far more complicated than a two shaft GTF.

Lightsaber



I've posted how many times?!?
User currently offlineSEPilot From United States of America, joined Dec 2006, 6682 posts, RR: 46
Reply 13, posted (6 years 12 months 10 hours ago) and read 10287 times:

Quoting TristarSteve (Reply 8):
Then you don't need any gears.?

You miss the point. The idea is to have a gear reduction between the fan and the turbine, and then have contrarotating fans/turbines as well. That is what I was getting at.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 14, posted (6 years 12 months 7 hours ago) and read 10117 times:

Quoting Scbriml (Reply 6):
Call that contrarotatring?

These bad boys are contrarotating at its finest:

Damn, now you've gone and done it....talk about yer heavy metal thunder......I love it.


User currently offlineA342 From Germany, joined Jul 2005, 4675 posts, RR: 3
Reply 15, posted (6 years 12 months 7 hours ago) and read 10069 times:

Well, the Russians are some steps ahead in this aspect:

http://motor-s.ru/NK93_en.htm

http://www.kmpo.ru/indexe.htm

IIRC the engine has already run, but Tu204 can probably tell you more about that.



Exceptions confirm the rule.
User currently offlineLemurs From United States of America, joined Mar 2005, 1439 posts, RR: 4
Reply 16, posted (6 years 12 months 6 hours ago) and read 9975 times:

Lightsaber, why couldn't this just be a 3 spool design? I saw your response to TristarSteve, but I didn't quite follow what the problem would be...if you were hooking up the two fans to their own spools and making the core the a single spool, it could work and still be fairly conventional and simple, no?

The FlightGlobal article points out that the front fan has noticably fewer fan blades than the rear one. That hints at a simple 3 spool, but different than what RR is doing. Standard HP core, fairly standard LP driving the rear fan and lead stage(s) and another LP (VLP?) beyond that driving the lighter front fan only. It would certainly reduce the complexity of the problem down dramatically from any kind of geared solution, no?



There are 10 kinds of people in the world; those who understand binary, and those that don't.
User currently offlineLightsaber From United States of America, joined Jan 2005, 12430 posts, RR: 100
Reply 17, posted (6 years 12 months 4 hours ago) and read 9860 times:
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Quoting Lemurs (Reply 16):
Lightsaber, why couldn't this just be a 3 spool design? I saw your response to TristarSteve, but I didn't quite follow what the problem would be...if you were hooking up the two fans to their own spools and making the core the a single spool, it could work and still be fairly conventional and simple, no?

It could be a 3-spool.

But by using two of the spools to turn the fans, you limit each spools Mach number at the fan (Feel free to think RPM). Thus, you lose the benefit of RR's triple spool of having the low compressor and low turbine spinning fast enough to be efficient.  Smile

I've read a bit more about this offline, and am now convinced that the added complexity of the 2nd part of the gearbox wasn't as bad as I feared. So move the EIS up by 5 or so years.  spin 

I still think a geared solution is simpler. But that's me. I've been exposed to the ugly sides of GTF's and haven't been scared off.  bigthumbsup 

Lemurs, love the quote in your signature.  Smile

So now I'm in favor of this as a 2nd generation turbofan. You really need to get the low turbine Mach number (again, feel free to think RPM) up. Dramatically! There is too much efficiency being thrown away in a low Mach number turbine.


Lightsaber



I've posted how many times?!?
User currently offlineLemurs From United States of America, joined Mar 2005, 1439 posts, RR: 4
Reply 18, posted (6 years 12 months 4 hours ago) and read 9807 times:

Quoting Lightsaber (Reply 17):
But by using two of the spools to turn the fans, you limit each spools Mach number at the fan (Feel free to think RPM). Thus, you lose the benefit of RR's triple spool of having the low compressor and low turbine spinning fast enough to be efficient.

Ah right, I always lose sight of that. Low pressure systems in current turbofans are inherently about picking the least ugly tradeoff, aren't they? I don't suppose the configuration of the fan would dramatically change the optimal rotational speed for a given diameter, would it? There's only so fast the outer edges can go before they stop doing their job well, right? (i.e. would that front fan with fewer blades have a higher optimal RPM than a conventional fan, allowing for a less painful tradeoff?) Still obviously not as good as letting everyone spin at their most efficent speed, like a gearset would allow, I realize.

Quoting Lightsaber (Reply 17):
Lemurs, love the quote in your signature.

Thanks! It's both fun and practical. It sort of acts as a self-selection mechanism. I know almost without fail that I will enjoy talking to anyone who "gets" it without me having to explain. I have a large body of experience using it, so I know it works. Let's just say I am not shocked you got it.  Wink



There are 10 kinds of people in the world; those who understand binary, and those that don't.
User currently offlineRayChuang From United States of America, joined Jun 2000, 7929 posts, RR: 5
Reply 19, posted (6 years 12 months 2 hours ago) and read 9509 times:

Combine this with the upgraded CFM56 engine core and we could see 8-14% fuel efficiency improvements without having to go to a new airframe for a 737 or A320 Family replacement. That could make the A320 Family viable for the next 25 years.

User currently offlineXT6Wagon From United States of America, joined Feb 2007, 3322 posts, RR: 4
Reply 20, posted (6 years 12 months 2 hours ago) and read 9399 times:

Quoting RayChuang (Reply 19):
That could make the A320 Family viable for the next 25 years.

NO

The MX benefits of the construction methods used for the 787 make the 737RS unbeatable given that any existing engine could very well be used on the 737RS if it works on a A320. Not to mention the 737RS will be cheaper to make than the 737NG despite having more toys stuffed in it.

The A320 dies the day the 737RS enters service, the only question is how long does the body keep twitching.


User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 21, posted (6 years 11 months 4 weeks 1 day 10 hours ago) and read 9242 times:

Quoting XT6Wagon (Reply 20):
Quoting RayChuang (Reply 19):
That could make the A320 Family viable for the next 25 years.

NO

The MX benefits of the construction methods used for the 787 make the 737RS unbeatable given that any existing engine could very well be used on the 737RS if it works on a A320. Not to mention the 737RS will be cheaper to make than the 737NG despite having more toys stuffed in it.

The A320 dies the day the 737RS enters service, the only question is how long does the body keep twitching.

XT6Wagon it seems a bit premature to present a non existing aircraft (not event sketches available) as a winner over another aircraft because of an unproven technology.


User currently offlineLMP737 From , joined Dec 1969, posts, RR:
Reply 22, posted (6 years 11 months 4 weeks 1 day 4 hours ago) and read 9180 times:

Quoting Dougloid (Reply 3):
One of our guys spent seven weeks in Tahiti on that show.

The horror.


User currently offlineKeesje From , joined Dec 1969, posts, RR:
Reply 23, posted (6 years 11 months 3 weeks 4 days 6 hours ago) and read 8978 times:

Bombardier recently with regards to their C-series:

“Now we’ve got until 2013, this fits in well with geared-turbofan technology. It also fits with Rolls-Royce which is thinking of a new engine and it fits with CFM as well.”

Scott says that Bombardier has been impressed by Pratt & Whitney’s geared turbofan, which has not been mirrored to date by its rivals.

“They’ve been working on this technology for a long time and it’s now matured to a point where we can put it on a new aircraft. It’s a very good option, but it’s not going unnoticed by Rolls-Royce and CFM.”


the pressure on the industry to come up with new smaller turbofan is increasing it seems..

[Edited 2007-05-02 23:36:41]

User currently offlineSanjet From Canada, joined Mar 2005, 180 posts, RR: 0
Reply 24, posted (6 years 11 months 3 weeks 3 days 10 hours ago) and read 8858 times:

Quoting XT6Wagon (Reply 20):
NO

The MX benefits of the construction methods used for the 787 make the 737RS unbeatable given that any existing engine could very well be used on the 737RS if it works on a A320. Not to mention the 737RS will be cheaper to make than the 737NG despite having more toys stuffed in it.

The A320 dies the day the 737RS enters service, the only question is how long does the body keep twitching.

LOL thanks for the outlook XT6...  Embarrassment



Will Fly For Food!
25 Boeing7E7 : Going out on a limb here.... ie... Beta vs. VHS... They all get together and develop an engine that combines all of their technologies in one way or a
26 Post contains links Keesje : CFM studies 'open rotor' concept for next generation airliner engine CFM International is conducting preliminary studies of open rotor and other pote
27 Post contains images Starlionblue : No pun intended?
28 Post contains links and images Keesje : CFM is also studying different fan options. One off the problems with UDF es if I remember well the charaterictics of the noise it makes (irritating f
29 Stitch : Both the GTF and LEAP56 programs appear to have the fuel savings needed to justify the launch of the 737RS and A320RS programs... And if the GTF can d
30 Post contains links Strathpeffer : I was really intersted to read the full article that includes this info in this week's printed FI. http://www.flightglobal.com/articles...-for-next-ge
31 MarkC : The airframers are not ready for new tech engines now. They would rather keep selling their narrow body cash makers for the forseable future. An engin
32 JetMech : True, but I think a more realistic scenario would be Airbus or Boeing scrambling to get some sort of exclusivity deal with an engine maker that produ
33 XT6Wagon : Wrong, Boeing wants to do the 737RS ASAP. They will produce the two side by side for a few years like they did with the 737 and 737NG so the "we woul
34 Stitch : I depends on how that tech can be integrated into existing designs. P&W believe their GTF will fit under the wing of the current A320 family (but not
35 Thegeek : At the risk of reviving an old thread, wouldn't this result in effectively a two stage fan and a low bypass ratio? Wouldn't that be counter productive
36 Tdscanuck : Having a two-stage fan doesn't automatically lower the bypass ratio...provided they lower the disk loading accordingly, they could hold the same bypa
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