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‘More Electric’ 787 Spurs Engine Evolution  
User currently offlineNoWorries From United States of America, joined Oct 2006, 539 posts, RR: 1
Posted (7 years 2 months 2 weeks 6 days 10 hours ago) and read 9087 times:

There's been some debate in various threads recently about whether bleedless is "the way to go". This article seems fairly balanced in that it reviews some of the pros and cons of the approach. Some believe in it, some don't. Nothing really new on the topic, but an interesting read:

http://www.designnews.com/article/CA6441575.html?industryid=43651

21 replies: All unread, jump to last
 
User currently offlineN328KF From United States of America, joined May 2004, 6483 posts, RR: 3
Reply 1, posted (7 years 2 months 2 weeks 6 days 9 hours ago) and read 8814 times:

Quote:
Hinderberger says Boeing is agnostic about the two approaches since both meet Boeing’s requirements for engine starts and power generation. During start-ups, both engine designs can start in under 40 seconds from the two generators and under 70 seconds from one. “From our point of view, even though one engine is two-spool and one engine is three-spool, we look at them as a gearbox to provide rotating energy to generate power,” Hinderberger says. How that horsepower extraction from the engine affects its duty cycle – during idle, take-off, climb and cruise – is something that Boeing left in the hands of the engine makers. “That’s held very close to the vest by them,” Hinderberger says.

If this was true, then why the buzz about them not having confidence in the Pratt & Whitney GTF offering?



When they call the roll in the Senate, the Senators do not know whether to answer 'Present' or 'Not guilty.' T.Roosevelt
User currently offlineClassicLover From Ireland, joined Mar 2004, 4627 posts, RR: 23
Reply 2, posted (7 years 2 months 2 weeks 6 days 7 hours ago) and read 8516 times:

I read this today - excellent article.

Also, the other articles on that site about the 787 are brilliant also!



I do quite enjoy a spot of flying - more so when it's not in Economy!
User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 3, posted (7 years 2 months 2 weeks 6 days 2 hours ago) and read 8168 times:

Quoting N328KF (Reply 1):
If this was true, then why the buzz about them not having confidence in the Pratt & Whitney GTF offering?

I think that Hinderberger is using the term "gearbox" in a somewhat loose fashion. As far as he is concerned, the engine is merely a powered "gearbox" to which he can attach some of his generators. It is a bit like saying that the A380 is merely a glorified flying engine stand for a brace of RR T900's. All current commercial turbofans have an external gearbox to drive the engine accessories. The P&W GTF will use a planetary gearbox to couple the LPT and fan, which will supposedly give significant fuel burn benefits.

Regards, JetMech

[Edited 2007-05-16 00:34:01]


JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 4, posted (7 years 2 months 2 weeks 5 days 22 hours ago) and read 7923 times:

That is a pretty good article. I enjoyed reading it. I have quite a bit of experience working on the starter generators for the 787 since I worked on the testing and production setup for them. I have probably met everyone on the design team at one point or another when I was working at Hamilton Sundstrand. Those are very impressive machines. They are smaller than the generators on the 777, but about 50% more powerful. The generators themselves are more evolutionary though since the increases in power and decreases in size have been steady ever since the early jets used integrated drive generators. The biggest difference is that these are being used as starters too.

I think they didn't do justice to the amount of power drawn on startup up though. They are being tested to 200% overspeed.

Quoting JetMech (Reply 3):
I think that Hinderberger is using the term "gearbox" in a somewhat loose fashion.

I agree with that, but he is mostly correct. From my experience working on the main and aux generators, they really just have a gearbox assembly attachment to the engine. The design work goes from the spline powering the stator to the power distribution system.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineBoomBoom From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 2 months 2 weeks 5 days 22 hours ago) and read 7875 times:

For me, the money quote is:

Fuel economy isn’t the only thing the bleedless architecture has going for it. The bleedless engine eliminates a long list of pneumatic components from the plane, which has both weight and maintenance implications. “What we've been able to do is eliminate large number of line replaceable units that that over time usually played a major part in recurring maintenance costs of any one airplane. Just being able to get that off airlines' books is a huge advantage,” Hinderberger says. Then consider elimination of the ducting and pipe work associated with bleed air. “What you get is an engine with an enormous amount of accessibility,” he says


User currently offlineNoWorries From United States of America, joined Oct 2006, 539 posts, RR: 1
Reply 6, posted (7 years 2 months 2 weeks 5 days 22 hours ago) and read 7857 times:

Quoting RoseFlyer (Reply 4):
I enjoyed reading it. I have quite a bit of experience working on the starter generators for the 787 since I worked on the testing and production setup for them. I have probably met everyone on the design team at one point or another when I was working at Hamilton Sundstrand. Those are very impressive machines.

Just curious -- based on your interactions, what's your own impression of what Boeing thinks is the advantage of going more electric -- is it lower manufacturing costs, lower maintenance costs, improved efficiency, improved reliability, or some other reason. Seems like there's a lot of debate about just what the benefits might be -- seems hard to believe Boeing would opt for a paradigm shift like this without some benefit in mind?

[Edited 2007-05-16 04:21:45]

User currently offlineJetMech From Australia, joined Mar 2006, 2684 posts, RR: 53
Reply 7, posted (7 years 2 months 2 weeks 5 days 21 hours ago) and read 7459 times:

Quoting RoseFlyer (Reply 4):
I agree with that, but he is mostly correct. From my experience working on the main and aux generators, they really just have a gearbox assembly attachment to the engine.

Yep, that's entirely correct. On pretty much every commercial turbofan, the IDG's or generators are driven by an external gearbox. My post was in response to N328KF's post where I took it that he was confusing this external gearbox with P&W's GTF, which is a different gearbox entirely ? . You can see the external gearboxes in these photos of various RR turbofans. The first photo shows the IDG attached to the gearbox of a Trent 700 (black object). The second photo shows the external gearbox of an RB211-524G2. Pratt's GTF is an internal gearbox between the LPT and the fan.

The external gearbox is sandwiched between the starter motor and the IDG. Above the starter motor is the kevlar fan blade containment band.


Engine component accessibility on Rolls-Royce RB211-524G2


Regards, JetMech

[Edited 2007-05-16 05:07:38]


JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 8, posted (7 years 2 months 2 weeks 5 days 12 hours ago) and read 4589 times:

Quoting NoWorries (Reply 6):
based on your interactions, what's your own impression of what Boeing thinks is the advantage of going more electric -- is it lower manufacturing costs, lower maintenance costs, improved efficiency, improved reliability, or some other reason

My experience as an engineer is that I had nothing to do with the claims of how much more efficient it was going to be. We did what we were suppose to do. Also, I wasn't involved with the project in the design phase. I was involved in setting up testing and working on production issues.

One major thing that we felt was that going electric is a much more efficient use of energy. Electric motors and generators can run at about 70-90% efficiency, which means of the theoretical energy input, you get most of it out. Mechanical systems like engines usually get 30-50% efficiency, which means you waste a lot more energy in the process. (I could be completely making those numbers up though as I have no idea what the efficiency for these systems are since I'm not a design engineer). Switching to electric lets you theoretically save energy. Also you do get to remove all of the weight from all the pneumatic systems. However you add a lot of weight with the big electric components. The cores to the generators are quite heavy. It's about the size of a small basketball, but weighs somewhere around 100 lbs (I can't easily lift it). The finished generators are something in the range of 300lbs, so that is a lot of additional weight. The end game is, I don't know how much weight is being saved by going to electric. I remember joking around and wondering how on earth this thing was supposed to be lighter, but of course I have no idea how those pneumatic systems worked.

And of course there will be lower maintenance costs. You don't tear apart a starter generator for maintenance. You do probably have to maintain pressurized systems. Going electric in my mind will definitely improve maintenance costs.

As far as reliability goes, from the standpoint of a starter generator, if the thing failed then it doesn't matter how big it is since it's a critical component. The plane can fly with all four out, but its not a pretty situation. The 787 does have a beast of a RAT, although it isn't as big as the 6ft diameter RAT on the A380.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineRb211TriStar From United States of America, joined May 2007, 185 posts, RR: 0
Reply 9, posted (7 years 2 months 2 weeks 5 days 11 hours ago) and read 4090 times:

Quote:
The end game is, I don't know how much weight is being saved by going to electric. I remember joking around and wondering how on earth this thing was supposed to be lighter

 checkmark 

My thoughts exactly. If you're removing a system, it obviously has to be replaced with another... unless you're removing functionality. There's a weight savings by removing the pneumatics, but a gain in adding the new electric systems (and their redundant systems). I'd be willing to bet the electric system is lighter, but by how much?

Either way, great article... and that 1.5MW power rating is awe-inspiring!


User currently offlineMlglaw From United States of America, joined Feb 2006, 53 posts, RR: 0
Reply 10, posted (7 years 2 months 2 weeks 5 days 10 hours ago) and read 3711 times:

Isn't the article incorrect when discussing emission reductions? The emission of concern , I believe, is carbon monoxide not carbon dioxide.  Confused


Sumus Primi BLS'60 - Oderint dum metuant!
User currently offlineNoWorries From United States of America, joined Oct 2006, 539 posts, RR: 1
Reply 11, posted (7 years 2 months 2 weeks 5 days 10 hours ago) and read 3609 times:

Quoting Mlglaw (Reply 10):
Isn't the article incorrect when discussing emission reductions? The emission of concern , I believe, is carbon monoxide not carbon dioxide

An interesting point -- normally you'll see CO and NOx mentioned together when talking about internal combustion engine emissions standards; CO is hazardous in relatively low concentrations. When talking about jet engines, I'm assuming the same concerns exist (especially for ground operations?). If they're talking about CO2 and greenhouse gases, that's a different story. Hard to tell which one they were talking about -- assuming the article is correctly written they're concerned about CO2 as a greenhouse gas.


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5410 posts, RR: 30
Reply 12, posted (7 years 2 months 2 weeks 5 days 10 hours ago) and read 3563 times:

CO isn't a big deal as far as greenhouse gasses are concerned. It's CO2 which has people and polar bears heading for high ground...


What the...?
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 13, posted (7 years 2 months 2 weeks 5 days 10 hours ago) and read 3513 times:

Quoting Mlglaw (Reply 10):
Isn't the article incorrect when discussing emission reductions? The emission of concern , I believe, is carbon monoxide not carbon dioxide

CO2 is an easy one to justify at this point. If you save 20% of the fuel, then you are going to be releasing less carbon dioxide simply because you are burning less of it. I think that using CO2 is a creative way to say that emissions are less just because the plane uses less fuel. CO emissions are harder to quantify when you use them as a percentage of fuel consumed.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineNoWorries From United States of America, joined Oct 2006, 539 posts, RR: 1
Reply 14, posted (7 years 2 months 2 weeks 5 days 10 hours ago) and read 3445 times:

With respect to going bleedless, AFAIK Airbus is not going bleedless with the A350, their position being that the benefits are not that clear (maybe they're right on that point, maybe they're wrong -- at this point I don't think anyone knows for certain) I'm wondering if Boeing can actually quantify the value of going bleedless in terms of operating and/or maintenance costs. I'm assuming they believe that they can -- it'd be interesting to know just how they present that to customers.

User currently offlineAirFrnt From United States of America, joined Jul 2004, 2825 posts, RR: 42
Reply 15, posted (7 years 2 months 2 weeks 5 days 9 hours ago) and read 3376 times:

Quoting RoseFlyer (Reply 4):
That is a pretty good article. I enjoyed reading it. I have quite a bit of experience working on the starter generators for the 787 since I worked on the testing and production setup for them. I have probably met everyone on the design team at one point or another when I was working at Hamilton Sundstrand. Those are very impressive machines. They are smaller than the generators on the 777, but about 50% more powerful. The generators themselves are more evolutionary though since the increases in power and decreases in size have been steady ever since the early jets used integrated drive generators. The biggest difference is that these are being used as starters too.

Great post, and welcome to my RR list.


User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 16, posted (7 years 2 months 2 weeks 5 days 2 hours ago) and read 3213 times:

Quoting NoWorries (Reply 14):
I'm wondering if Boeing can actually quantify the value of going bleedless in terms of operating and/or maintenance costs. I'm assuming they believe that they can -- it'd be interesting to know just how they present that to customers.

I have the full belief that theoretically they have. There's a difference between computer models and real life. In my opinion, bleedless and bleeded are two different ways to tackle a problem. Either could prove to be the best. It all depends on how well the systems are optimized. Boeing is betting that for the 787, there is the right amount of technology that can be used to make bleedless the least expensive method.

We'll know if it was a good idea when we find out if the 737-RS is going bleedless or not.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineStirling From Italy, joined Jun 2004, 3943 posts, RR: 21
Reply 17, posted (7 years 2 months 2 weeks 5 days 1 hour ago) and read 3195 times:

Quoting RoseFlyer (Reply 8):
The finished generators are something in the range of 300lbs, so that is a lot of additional weight.

Which equals 2 fare-paying passenger. (1 and half in the U.S.)

Quoting RoseFlyer (Reply 8):
The 787 does have a beast of a RAT, although it isn't as big as the 6ft diameter RAT on the A380.

You know I haven't seen any photos of this anywhere.....I assume it deploys from somewhere around the wingbox?
Six feet! That is enormous.

On a related note....
Who are the contractors that are casting the engine parts?
I was reading about this company in Portland I'd never heard of before, come to find out they are this International concern with facilities all over the world, and supposedly involved in the casting of the turbine cores in the latest generation jet engines...tho' it did not mention which ones.
If memory serves correctly, the company's name is Precision Castparts, or something to that effect.



Delete this User
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 18, posted (7 years 2 months 2 weeks 5 days 1 hour ago) and read 3140 times:

Quoting Stirling (Reply 17):
You know I haven't seen any photos of this anywhere.....I assume it deploys from somewhere around the wingbox?
Six feet! That is enormous.

It deploys directly from the lower fuselage. I can't remember where exactly it is for the A380, but it is usually just forward of the wing to either side.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineBrendows From Norway, joined Apr 2006, 1020 posts, RR: 4
Reply 19, posted (7 years 2 months 2 weeks 5 days ago) and read 3114 times:

Quoting RoseFlyer (Reply 18):
I can't remember where exactly it is for the A380, but it is usually just forward of the wing to either side.

I believe that the RAT on the A380 is located in the inner flap track on the port wing. Take a look at it here:

View Large View Medium
Click here for bigger photo!

Photo © Andrew Hunt - AirTeamImages
View Large View Medium
Click here for bigger photo!

Photo © Tchavdar Kostov - BGspotters



User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9511 posts, RR: 52
Reply 20, posted (7 years 2 months 2 weeks 3 days 11 hours ago) and read 2859 times:

Quoting Brendows (Reply 19):
I believe that the RAT on the A380 is located in the inner flap track on the port wing. Take a look at it here:

Hmm, I don't think I can see where it comes out in those photos. I've only seen them when they are not installed since my desk use to be about 300 ft away from where the RATs were assembled. And yes, those things are assembled piece by piece by hand.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineRheinbote From Germany, joined May 2006, 1968 posts, RR: 52
Reply 21, posted (7 years 2 months 2 weeks 3 days 11 hours ago) and read 2826 times:

Quoting RoseFlyer (Reply 20):
Quoting Brendows (Reply 19):
I believe that the RAT on the A380 is located in the inner flap track on the port wing. Take a look at it here:

Hmm, I don't think I can see where it comes out in those photos.

Brendows is correct.


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