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Topic: Developing Leap Engine Technology for 737MAX
Username: frmrcapcadet
Posted 2012-12-09 10:36:33 and read 14402 times.

http://seattletimes.com/html/busines...gy/2019849748_sundaybuzz09xml.html

The story features a bit of commentary on the A versus B dustup with two new narrow body updates. But the interesting part is a brief discussion of the very advanced technology and some of the problems which had to be solved to get ever more efficient engines. To a 'non-techie' is all sounds pretty amazing, and a response is almost, 'you mean you can make all of that work?!'

Topic: Developing Leap Engine Technology for 737MAX
Username: goosebayguy
Posted 2012-12-09 11:56:39 and read 14225 times.

From what I know Rolls Royce is also working on very similar technology for its large engines. Technology is changing and quickly here.

Topic: Developing Leap Engine Technology for 737MAX
Username: tdscanuck
Posted 2012-12-09 12:16:52 and read 14152 times.

Quoting frmrcapcadet (Thread starter):
To a 'non-techie' is all sounds pretty amazing, and a response is almost, 'you mean you can make all of that work?!'

That's the appropriate response, even for techies. A modern commercial jet engine is the most advanced product ever produced by the human race. With the possible exception of the semiconductor guys at Intel, it's probably also the world forefront of materials research.

Tom.

Topic: Developing Leap Engine Technology for 737MAX
Username: AA737-823
Posted 2012-12-09 13:27:31 and read 13953 times.

Quoting tdscanuck (Reply 2):
A modern commercial jet engine is the most advanced product ever produced by the human race. With the possible exception of the semiconductor guys at Intel, it's probably also the world forefront of materials research.

It really and truly is; it's amazing how we can take such a simple concept as the jet engine (one main moving part, all cycles happening at the same time, in different places), and complicate things further and further (variable bleed valves, variable stator vanes... and that's just twenty years ago!!) in the name of efficiency. I HOPE that reliability doesn't suffer, but with increased complexity, a corresponding decrease in dependability is to be expected, particularly once you bring software into the equation.

Topic: Developing Leap Engine Technology for 737MAX
Username: DocLightning
Posted 2012-12-09 14:22:37 and read 13786 times.

Quoting AA737-823 (Reply 3):
It really and truly is; it's amazing how we can take such a simple concept as the jet engine (one main moving part, all cycles happening at the same time, in different places), and complicate things further and further (variable bleed valves, variable stator vanes... and that's just twenty years ago!!) in the name of efficiency. I HOPE that reliability doesn't suffer, but with increased complexity, a corresponding decrease in dependability is to be expected, particularly once you bring software into the equation.

If that's the case, then why have engines become more and more reliable over time? FADEC isn't exactly new technology. It's been around at least since the A300. Engines have continually gotten more and more reliable...and they have gotten simpler. Many of the new designs manage to be so efficient by using fewer stages to accomplish the same job.

Early jet engines were horribly finicky. Modern jet engines are among some of the most reliable machines made. They have to be.

Topic: Developing Leap Engine Technology for 737MAX
Username: Revelation
Posted 2012-12-09 15:02:47 and read 13643 times.

Quoting tdscanuck (Reply 2):
A modern commercial jet engine is the most advanced product ever produced by the human race. With the possible exception of the semiconductor guys at Intel, it's probably also the world forefront of materials research.

FWIW, the world's fastest production microprocessor, by a fair margin, comes from IBM... Granted to get there they've had to master water cooling as opposed to air cooling, but as you imply, the power density of a high end microprocessor is greater than that of a rocket nozzle, and all this heat can't impact the nanometer features or else it's all over...

Topic: Developing Leap Engine Technology for 737MAX
Username: lightsaber
Posted 2012-12-09 16:17:21 and read 13465 times.

Even I found the article interesting as it helped me understand why the LEAP is as light as it is. (I'm an aero guy, so I focus on those aspects first.) In particular the extra stages of the LPT have had their extra weight compensated by the improvements in the fan region.

But the article didn't go into the aspects of the LEAP that let it compete with the GTF. In particular the scaloped low compressor and the 7 stage low compressor.    It also didn't go into how GE is having to push the aerodynamics of the fan to attain efficiency at tip speeds not previously attempted while reducing noise. For the low turbine efficiency is compromised by the low mach number of the blade tips (that is the main advantage of the GTF, improving the LPT efficiency).

But what I find startling in this article is that it skips over that GE is pushing high turbine inlet temperatures to new records for commercial narrow-bodies. While each generation must increase that temperature, GE is going to be the leader in the next generation as the PW2000 was in a past life. That is how 2 stages are powering 10 modern high pressure compressor stages.

I'm personally excited on how two very different approaches to engine technology are competing. Pratt has their risk in the gears. GE in the high turbine with a little more risk in the fan and LPC.

I do wonder with GE noting both are improving the same (I disagree). But then again, they have a financial incentive to downplay competition. Am I being cynical? I think we'll know within 7 years.   But not much sooner.  
Quoting goosebayguy (Reply 1):

From what I know Rolls Royce is also working on very similar technology for its large engines. Technology is changing and quickly here.

And so is Pratt. It is about who is ready for the right risk level at EIS at a given time. No one should dismiss any of the big 3 engine makers. Pratt right now has the most to prove (due to its very low market share).

Quoting Revelation (Reply 5):
the power density of a high end microprocessor is greater than that of a rocket nozzle

   microprocessors do not require cryogenic evaporative cooling to survive.

Quoting DocLightning (Reply 4):
FADEC isn't exactly new technology.

Understatement. FADECs are now a given. Sensor reliability has improved dramatically.

This is a battle where Pratt only pushed the gearbox technology and not much else. This put them at risk of being matched or even beaten by a non-GTF. GE has taken on the risk of implimenting some leading edge technology. Most of which is little more risk than just designing a new engine. The one I think will be an issue is the high turbine temperature. Then again, I'm biased. I used to design combustor airflow into the turbine and the flow was critical for turbine life. If GE's materials are as good as promise, then they will have pulled off as big a feat as the GTF.

So we could then speculate on combining the technologies for the next engine.   

Lightsaber

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: JAAlbert
Posted 2012-12-09 18:30:07 and read 12906 times.

Quoting DocLightning (Reply 4):
Modern jet engines are among some of the most reliable machines made.

Each time I fly I marvel at how reliable the engines are. They fly literally thousands of miles in a day - some aircraft fly half way around the world and then fly right back a few hours later, day in day out. That airlines have so few engine problems given the amount of use is astonishing (and of course very reassuring!)

It's part of the magic of flight that draws me to flight again and again.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: nomadd22
Posted 2012-12-09 19:44:30 and read 12258 times.

Quoting lightsaber (Reply 6):
Quoting Revelation (Reply 5):
the power density of a high end microprocessor is greater than that of a rocket nozzle

microprocessors do not require cryogenic evaporative cooling to survive.

Those two statements aren't exactly contradictory. Processors can be cooled through conduction to a much larger radiative area. Some rocket nozzles are only cooled by radiation, some by ablation and some by circulating cryogenic fluid. I know of processors that generate about 60 watts per cm2, which might be close to what a large purely radiative nozzle like the Merlin vacuum one does.

The point being, liquid cooling for processors isn't because a heat sink couldn't handle the job, It's generally because you can't just put a big heat sink at the chip location, but need to move the heat somewhere else to be disposed of.

[Edited 2012-12-09 19:48:25]

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: prebennorholm
Posted 2012-12-09 19:50:46 and read 12207 times.

Quoting AA737-823 (Reply 3):
and complicate things further and further (variable bleed valves, variable stator vanes... and that's just twenty years ago!!)

For airliners variable stator vanes were first time used on the GE CJ805 engine on the Convair CV-880.

The CJ805 was the civil version of the GE J79 engine (sans aft flame thrower) which first ran on a test bench on June 8, 1954. That's not 20 years ago, but 58 and a half years ago.

The first US produced engine with variable stator vanes was the slightly earlier GE J73 used on F-86H Sabre fighters.

There could be earlier applications of variable stator vanes in other countries, France, Britain, Russia, I haven't investigated that. I would gladly take a bet on that not being the case, but not more than I can afford to lose.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: RickNRoll
Posted 2012-12-09 20:19:52 and read 12004 times.

Quoting tdscanuck (Reply 2):
That's the appropriate response, even for techies. A modern commercial jet engine is the most advanced product ever produced by the human race. With the possible exception of the semiconductor guys at Intel, it's probably also the world forefront of materials research.

That's a big statement to make. The modern microprocessor is quite an achievement. They have the circuit lines on commercially available processors down to 22 nanometers, using 1.4Billion transistors on a die that is only 160mm2. The CPU is fetching, and executing, instructions in parallel. It will execute instructions speculatively in parallel, ahead of knowing which path is the correct one. They have been following "Moore's Law" for 50 years now, doubling the number of transistors on a chip every two years. (It's not really a law, it was just a guess that most would have assumed could only hold for perhaps ten years or so).

I'm not putting down the amazing achievements of the modern jet engine, they are mind boggling, just saying there are very smart people out there in more fields who are also doing work that is just as impressive, IMHO.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: ContnlEliteCMH
Posted 2012-12-09 21:09:50 and read 11664 times.

Quoting AA737-823 (Reply 3):
I HOPE that reliability doesn't suffer, but with increased complexity, a corresponding decrease in dependability is to be expected, particularly once you bring software into the equation.

(1) Since software is already heavily used on today's modern turbofan, how is it now being brought into the equation?

(2) Since the engines equipped with this software are the most efficient and reliable to-date, upon what experience do you single out software as a critical element contributing to a lack of reliability? Are you suggesting that today's engines would be even more reliable without software?

Quoting DocLightning (Reply 4):
If that's the case, then why have engines become more and more reliable over time?

They get more reliable *because* of software, not despite it. Software yields (at least) two benefits for commercial jet engines:

(1) During design, software enables designs to be refined much more than was ever possible with paper designs. During testing, software permits data to be collected on a larger scale, and analyzed much more quickly (and with far more detail) than was previously possible.

(2) In operation, software permits more precise, more repeatable, and more complex control of engine components and their interaction than any flight engineer could provide. It also provides for substantial data collection and ever-increasing real-time and post-failure analysis, which permits OEM's and airlines to zoom in on problems quickly and identify their root causes. Software can even be used to detect problems before they become serious incidents. It seems counterintuive, but there are scenarios in which an IFSD is vastly preferable to the failure that could occur if a problem went undetected.

If engines get more reliable (or maintain their current stellar track record), I expect it will be "particularly" once *more* sotware is introduced.

[Edited 2012-12-09 21:12:30]

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: autothrust
Posted 2012-12-10 02:25:31 and read 10212 times.

Quoting tdscanuck (Reply 2):
A modern commercial jet engine is the most advanced product ever produced by the human race.

Offtopic but i would dare to say the SSME are the most advanced product ever produced.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: AA737-823
Posted 2012-12-10 03:51:22 and read 9796 times.

Well, in a way that only a.net can do, we've turned this into an argument.
 
Quoting ContnlEliteCMH (Reply 11):
(1) Since software is already heavily used on today's modern turbofan, how is it now being brought into the equation?

I didn't say that the Leap will be the "first ever engine to use software," did I? I'm simply saying that engines are becoming more and more reliant on electronic controls. And the earliest versions of FADEC most assuredly pale in comparison to what's being done today; it's amazing.

Quoting ContnlEliteCMH (Reply 11):
(2) Since the engines equipped with this software are the most efficient and reliable to-date, upon what experience do you single out software as a critical element contributing to a lack of reliability? Are you suggesting that today's engines would be even more reliable without software?

Reliability can be defined in a couple of different ways. One way (which you seem to refer to) might be explosions inflight, failures inflight, catastrophic uncontained fireballs of parts, etc. ANOTHER way to measure reliability is in the number of times that I myself am at the gate changing stupid electronic components, compared to the number of times I've performed similar tasks on, say, the venerable (if noisy) JT-8D. Which is, for the record, zero.
Now- does a CFM56 stay on wing for a lot longer than a JT-8? Absolutely. But rest assured, they have their quirks, and many of them are related to the onboard monitoring hardware and software, which in the end, causes a lot of gate delays that the JT-8D simply doesn't produce.

Quoting DocLightning (Reply 4):
If that's the case, then why have engines become more and more reliable over time? FADEC isn't exactly new technology. It's been around at least since the A300. Engines have continually gotten more and more reliable...and they have gotten simpler. Many of the new designs manage to be so efficient by using fewer stages to accomplish the same job.

To say that engines have gotten simpler is mostly eroneous; sure, stages are eliminated as possible, but that's about the end of it. We've gone from can combustors to TAPS (Twin-annular, pre swirlers!! Whoa baby!). We've gone from relatively low pressure ratios to insanely high ones. Active Turbine Clearance Controls.
Heck, the engines now have their own built-in alternators to power the EEC in the event that the generators fail; ya won't see/need that on a JT-8.
And sure, the reliability of FADEC.... it's dual channel on the CFM56 (and I assume everything else, but my area of expertise is limited to the topic at hand), but go ahead and ask me if we're able to dispatch on a single-channel failed EEC. The answer is no.

Lest you think I'm singing the praises of a JT-8, I'm not; it was a fantastic engine in its day. I'd rather have CFM56's on the wings of the airplane as I look out the window at 41,000 feet. But- to say that the CFM56 is a simple engine is a slap in the face to countless engineers and assembly workers. It's not simple, it's a remarkably complex feat of engineering.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: spink
Posted 2012-12-10 04:10:03 and read 9658 times.

Quoting Revelation (Reply 5):
FWIW, the world's fastest production microprocessor, by a fair margin, comes from IBM... Granted to get there they've had to master water cooling as opposed to air cooling, but as you imply, the power density of a high end microprocessor is greater than that of a rocket nozzle, and all this heat can't impact the nanometer features or else it's all over...

FWIW, Intel could release much faster production microprocessors than they currently do, but it doesn't make economic sense to do so.

The IBM Power series gets a large portion of its performance from a greatly expanded power budget and the ability of a quite different economic model to allow them to increase the average cost per chip over an order of magnitude more than intel (IBM doesn't sell microprocessors, they sell systems, and sell in much much less volume, volume has some interesting impacts).

For process technology, Intel is well over a year ahead of anyone else in the industry currently and the gap has been increasing. Unless others step up they rate of new process introduction, Intel will likely get beyond a 2 year lead in process technology.

Regardless, I would say that the modern microprocessor is probably the most advanced manufactured good in the world at the moment. While the new Jet engines will be pushing HPT inlet temperatures beyond what most people considered economically viable, modern semi-conductor fabs are pushing feature sized below what many people considered physically possible given the light sources they are using. Modern feature geometry is roughly 1/18th of the width of the light sources being used which is pretty incredible.

As far as heat flux, there are modern semiconductors that are well over 100W/cm2.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: tdscanuck
Posted 2012-12-10 07:06:55 and read 8408 times.

Quoting RickNRoll (Reply 10):
That's a big statement to make. The modern microprocessor is quite an achievement.

No disagreement, but a modern microprocessor is just one of the parts of a modern jet engine...one kinds of subsumes the other, in my mind.

Quoting autothrust (Reply 12):
Offtopic but i would dare to say the SSME are the most advanced product ever produced.

At their time, I'd agree. But a lot has happened to jet engines since then and the SSME has remained pretty static.

Tom.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: NeutronStar73
Posted 2012-12-10 07:19:36 and read 8293 times.

I'm gonna say, as much as I adore jet engine technology, it is NOT the most advanced technology produced by man. I think modern rocket technology / space technology takes that cake.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: tdscanuck
Posted 2012-12-10 08:48:41 and read 7638 times.

Quoting NeutronStar73 (Reply 16):
I think modern rocket technology / space technology takes that cake.

Who's doing what in space that compares to what the commercial jet engine makers are doing? You show me a rocket engine that goes 50,000 hours without major overhaul.

Tom.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: yowviewer
Posted 2012-12-10 09:58:23 and read 7139 times.

Quoting NeutronStar73 (Reply 16):

If we're talking 1960's then I agree with the rocket/space technology and the race for space. Voyager 1 and 2 are also great examples. But with research cutbacks, etc. I think advances have slowed in the last 30 years or so.
Because of the continued demand for improvements in commercial jet engines due to both competition and oil prices, I have to agree with the jet engine. The reliability factor just absolutely amazes me !

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: ferpe
Posted 2012-12-10 10:09:37 and read 7051 times.

Quoting lightsaber (Reply 6):
But what I find startling in this article is that it skips over that GE is pushing high turbine inlet temperatures to new records for commercial narrow-bodies. While each generation must increase that temperature, GE is going to be the leader in the next generation as the PW2000 was in a past life. That is how 2 stages are powering 10 modern high pressure compressor stages.

Where is the component efficiency on an engine like the Leap? I understand they should be above 90% on the compressor and perhaps 92-93% on the turbine, any info? I understand the pressure ratio is 40, with about 22 in the high compressor.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: nomadd22
Posted 2012-12-10 10:10:36 and read 7037 times.

Quoting tdscanuck (Reply 17):
Quoting NeutronStar73 (Reply 16):
I think modern rocket technology / space technology takes that cake.

Who's doing what in space that compares to what the commercial jet engine makers are doing? You show me a rocket engine that goes 50,000 hours without major overhaul.

Tom.

And, rocket engines are mainly one stage turbines sending fuel and oxidizer into a combustion chamber. maybe with some diversion for regen cooling of the nozzle. Much less complicated than the modern jet engine.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: SEPilot
Posted 2012-12-10 10:40:49 and read 6801 times.

Quoting AA737-823 (Reply 3):
I HOPE that reliability doesn't suffer, but with increased complexity, a corresponding decrease in dependability is to be expected, particularly once you bring software into the equation.

In fact a lot of the increase in reliability is due to more and more functions being electronically controlled instead of mechanically (this is true for automobiles and trucks as well.) I encountered this in my own career designing grinding machines; when we transitioned to full computer control from mechanical and electro-mechanical control reliability took a quantam leap forward. The electronics and software are probably the most reliable parts of the whole engine.

Quoting lightsaber (Reply 6):
But the article didn't go into the aspects of the LEAP that let it compete with the GTF. In particular the scaloped low compressor and the 7 stage low compressor. It also didn't go into how GE is having to push the aerodynamics of the fan to attain efficiency at tip speeds not previously attempted while reducing noise. For the low turbine efficiency is compromised by the low mach number of the blade tips (that is the main advantage of the GTF, improving the LPT efficiency).
Quoting lightsaber (Reply 6):
So we could then speculate on combining the technologies for the next engine.

The problem for GE is that if Pratt takes the technology that GE is applying to the LEAP and applies it to the GTF then they will leave the LEAP in the dust. For this reason I was surprised and disappointed that Boeing did not include the GTF as an option on the MAX. I do believe that the gamble on the gears is a good one (my grandfather developed the basis of modern gear design-he popularized the involute form, and his manuals printed in the 30's are still in use today, so I am biased toward gears). Also, since the gear ratio can be changed to match the fan diameter the smaller fan diameter of the MAX should have a smaller efficiency penalty for the GTF than for the LEAP.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: Arrow
Posted 2012-12-10 10:50:36 and read 6766 times.

Quoting prebennorholm (Reply 9):
There could be earlier applications of variable stator vanes in other countries, France, Britain, Russia, I haven't investigated that. I would gladly take a bet on that not being the case, but not more than I can afford to lose.

I may be way off base on this -- but take a look at the Orenda Iroquois engine developed in Canada in the 50s for the ill-fated Avro Arrow. It was a world-beater at the time (until the government got its mitts on it). Apparently NASA's Propulsions Systems Laboratory had a look at it:


"In 1957 PSL also had a chance to test a rare Canadian jet engine, the Iroquois PS.13. The Avro Canada Company began designing its CF-105 Arrow jet fighter in the mid-1950s. Although not originally in the design, the decision was made to use two PS.13 engines developed by another branch of the company. These engines were more powerful than any contemporary U.S. jet engine, lightweight, and fuel efficient. The engines were tested in PSL during the extensive ground testing phase. The Arrow made its flight debut in March 1958, but was cancelled the following year when its perceived mission disappeared."

I have no idea if this engine incorporated variable stator vanes -- but I guess it's possible. (my father worked as an engineer on the Arrow).

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: JoeCanuck
Posted 2012-12-10 11:45:09 and read 6637 times.

Quoting SEPilot (Reply 21):

The problem for GE is that if Pratt takes the technology that GE is applying to the LEAP and applies it to the GTF then they will leave the LEAP in the dust.

On the flip side, there is no reason GE can't make a GTF of their own, (and I'd be shocked if they weren't working on it already). As far as I understand it, the advantage of the GTF is that the low pressure turbine can have fewer stages, (making the engine as a whole lighter and shorter), since it will be turning at its optimal speeds. GE is using more stages and cutting edge materials and shapes, to achieve similar levels of efficiency with a slower turning LPT. The fans are probably turning at similar speeds, the Leap probably a bit faster.

I'm guessing Pratt won't copy the GE LPT design since they don't have to. More stages probably means more losses as well as more weight...certainly more complexity.

The GTF seems the simpler way to go, (not to take away from Pratt's decades of research into the gearbox), but that doesn't mean the LEAP method doesn't have merit. GE, Boeing and Airbus are all betting on it.

I realise I'm leaving out huge swaths of technicality and accuracy, but it's probably a decent thumb nail sketch of thing.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: tdscanuck
Posted 2012-12-10 11:56:59 and read 6585 times.

Quoting JoeCanuck (Reply 23):
On the flip side, there is no reason GE can't make a GTF of their own, (and I'd be shocked if they weren't working on it already).

If GTF is as good as promised, they will. But, like Pratt, it will take them decades to figure it out and they're starting from waaaayyyy behind.

Tom.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: DocLightning
Posted 2012-12-10 11:58:07 and read 6729 times.

Quoting tdscanuck (Reply 24):
If GTF is as good as promised, they will. But, like Pratt, it will take them decades to figure it out and they're starting from waaaayyyy behind.

Not only that, but they have to duck and dodge patent infringements.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: SEPilot
Posted 2012-12-10 12:24:13 and read 6693 times.

Quoting DocLightning (Reply 25):
Not only that, but they have to duck and dodge patent infringements.

Most of the real technology has long passed the patentable stage. Planetary gears are so ubiquitous that it would be very difficult coming up with a patentable configuration. The problem is shoehorning a gearbox capable of handling the power required to drive the fan into a small and light enough package to work in a jet engine, and having the necessary reliability and durability to satisfy all concerned. The problems are primarily materials and lubrication; while these may be patentable they are unlikely to be unavailable to GE, as they will most likely be developed by third parties, as these are not really PW's area of expertise. Depending on who develops them under what arrangement with PW there may be patent issues, but I doubt that they will bar GE for long, as there are always other ways of doing things.

Quoting tdscanuck (Reply 24):
If GTF is as good as promised, they will. But, like Pratt, it will take them decades to figure it out and they're starting from waaaayyyy behind.

But it will not take decades for GE to catch up. Just as it did not take Douglas a decade to catch up to Boeing in jet transport design. It was mainly financial mismanagement that caused Douglas to lose the race, not technical inferiority. Once one company shows the way, it is much faster for others to do the same thing.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: lightsaber
Posted 2012-12-10 12:32:20 and read 6794 times.

Quoting JoeCanuck (Reply 23):
On the flip side, there is no reason GE can't make a GTF of their own,

It will cost GE less than the Billion Pratt put into researching the concept. Cooling and failure mode prediction are key.

Quoting JoeCanuck (Reply 23):
As far as I understand it, the advantage of the GTF is that the low pressure turbine can have fewer stages

The low compressor and low turbine are also more efficient for the same number of stages. The GTF also slows the fan which improves the fan's efficiency and allows equal fan efficiency with a lower tech fan.

Quoting JoeCanuck (Reply 23):
but that doesn't mean the LEAP method doesn't have merit. GE, Boeing and Airbus are all betting on it.

COMEC's C919 too. The LEAP has merit, but it does have some risks (notably the high turbine's inlet temperature).

Quoting SEPilot (Reply 26):
The problems are primarily materials and lubrication;

cooling too. But what Pratt has is failure mode prediction that they aren't sharing with anyone. Unless one can predict a gearbox is starting to fail 500+ cycles before the failure, no one will buy a GTF. Maintenance prediction is key in the new engines. The difficult part isn't making the gearbox as many have noted. Most of the technology inside the GTF has been bought from others. What is Pratt proprietary is the understand of the various failures of a gearbox to very accurately predict a failure. Pratt also went into several failure modes that apply in an aviation gearbox but not a ground based one and figured out how to mitigate a bunch of the risks (mostly via better cooling distribution).

Quoting SEPilot (Reply 26):
But it will not take decades for GE to catch up.

Agreed. Many of the 'false paths' won't be taken as Pratt has shown a working way. But GE couldn't have launched a GTF LEAP-X. Not to meet the C919 EIS date (as that was the launch platform).

Lightsaber

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: JoeCanuck
Posted 2012-12-10 13:57:12 and read 6577 times.

Quoting SEPilot (Reply 26):
The problem is shoehorning a gearbox capable of handling the power required to drive the fan into a small and light enough package to work in a jet engine, and having the necessary reliability and durability to satisfy all concerned.

GE won't be starting completely from scratch. They do have extensive experience with gearboxes on their turboprop and helicopter engines. While not in the same league as Pratt's GTF, they do have a bit of a springboard.

Quoting lightsaber (Reply 27):
The LEAP has merit, but it does have some risks (notably the high turbine's inlet temperature).

They are betting the farm on their exotic materials to keep the heat from frying the turbine...and exotic new tech can be scary. To make the Leap work as advertised, they don't have a lot of wiggle room...especially since their benchmark in reliability is the CFM-56...not an easy target to hit.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: mffoda
Posted 2012-12-10 13:58:53 and read 6573 times.

Quoting lightsaber (Reply 27):
COMEC's C919 too. The LEAP has merit, but it does have some risks (notably the high turbine's inlet temperature).

Hey lightsaber, I have question regarding turbine temperature. Do higher turbine temperatures assist in fuel burn efficiency or is this mostly a penalty? Thx.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: RickNRoll
Posted 2012-12-10 17:07:43 and read 6397 times.

Quoting tdscanuck (Reply 17):
Who's doing what in space that compares to what the commercial jet engine makers are doing? You show me a rocket engine that goes 50,000 hours without major overhaul.

Those Mars rovers are pretty impressive, especially the new one, with 70,000 hours by my calculation for Opportunity. No chance of any overhaul up there on Mars, or any maintenance whatsoever.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: tdscanuck
Posted 2012-12-10 18:56:04 and read 6294 times.

Quoting RickNRoll (Reply 30):
Those Mars rovers are pretty impressive, especially the new one, with 70,000 hours by my calculation for Opportunity. No chance of any overhaul up there on Mars, or any maintenance whatsoever.

Good point. On the reliability score, I have to hand it to the Spirit/Opportunityh team. However, I'd argue that those rovers are working in a far more benign environment (the rovers aren't trying to contain huge pressure at high temperature or working with anywhere close to the power density of a jet engine).

Credit xkcd.com:


Tom.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: lightsaber
Posted 2012-12-11 00:53:07 and read 6053 times.

Quoting mffoda (Reply 29):
Do higher turbine temperatures assist in fuel burn efficiency or is this mostly a penalty?

Higher turbine inlet temperatures help fuel burn efficiency as there is more energy to extract for the turbine. However, every 50 degrees F higher the metal temperature it cuts the turbine life in half. For example, 100 degrees hotter metal temperature has a quarter of the life.

GE's material change is exciting. The last material change of that magnitude was the use of single crystal on the PW2000. Which didn't go so well from a durability perspective.  

Lightsaber

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: packsonflight
Posted 2012-12-11 04:01:01 and read 5943 times.

Quoting mffoda (Reply 29):
Hey lightsaber, I have question regarding turbine temperature. Do higher turbine temperatures assist in fuel burn efficiency or is this mostly a penalty? Thx.

to attain 100% thermal efficiency of the engine you need two things:

Engine inlet temprature at 0 deg Kelvin (-273 Celcius) and turbine inlet temprature equal to core combustion temperature around 1500 deg Celcius

In the real world we do not come close to both thease numbers because at the lower end we are limited by the environment. on ground the temperature is commonly -10 to +35 deg Celcius so there we loose 263-308 degrees, and in cruise the ambient temperature is commonly -50 deg and -65 deg so there we "only" loose 223-208 degrees. So we can say that thermal efficiency of jet engines increases with lower ambient temperature,

In the top end we are limited by how high temperature the material in the turbine can withstand, possibly around 800 deg C, so in order not to fry the turbine the combustion camber exhaust gas is mixed with compressed air in order to lower the temprature from 1500 deg C to 800 deg C before it enters the turbine, and that is a whooping 700 deg loss! Add that to the losses at the lower end and we are well below 50% thermal efficiency.

It is important to develop new turbine materials that can withstand higher temprature because it directly increases thermal efficiency of the engine.
( I am estimating the core temp of 1500 deg C and turbine inlet temp of 800)

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: nomadd22
Posted 2012-12-11 04:40:27 and read 5883 times.

Quoting lightsaber (Reply 27):
Quoting SEPilot (Reply 26):
The problems are primarily materials and lubrication;

cooling too.

I take it cooling isn't too big an issue on the finished gearbox. Pratt indicated they designed a 98% efficient gearbox and it came in at 99%, so it's only putting out half the heat it was designed to handle, right? Not that even 1% of that much power is inconsiderable. I'd think that rising heat output must be a major factor in predicting failure.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: lightsaber
Posted 2012-12-11 06:25:58 and read 5773 times.

Quoting nomadd22 (Reply 34):
I take it cooling isn't too big an issue on the finished gearbox.

How its done is a big deal. The total heat isn't. Part of what keeps a gearbox efficient over the hours is cooling where the heat is.

Quoting nomadd22 (Reply 34):
I'd think that rising heat output must be a major factor in predicting failure.

And where tells you what type of failure. You have the right idea in the 'big picture,' but details are critical. Only by early identification and low cost rebuild will Pratt be able to exceed their maintenance promises (and they aim to exceed). That means being able to identify the repair needed to return the gearbox (which will be pulled from the A/C) to service quickly.

Lightsaber

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: brindabella
Posted 2012-12-11 06:32:13 and read 5762 times.

Quoting tdscanuck (Reply 24):
If GTF is as good as promised, they will. But, like Pratt, it will take them decades to figure it out and they're starting from waaaayyyy behind.
Quoting SEPilot (Reply 26):
But it will not take decades for GE to catch up. Just as it did not take Douglas a decade to catch up to Boeing in jet transport design. It was mainly financial mismanagement that caused Douglas to lose the race, not technical inferiority. Once one company shows the way, it is much faster for others to do the same thing.
Quoting lightsaber (Reply 27):
cooling too. But what Pratt has is failure mode prediction that they aren't sharing with anyone. Unless one can predict a gearbox is starting to fail 500+ cycles before the failure, no one will buy a GTF. Maintenance prediction is key in the new engines. The difficult part isn't making the gearbox as many have noted. Most of the technology inside the GTF has been bought from others. What is Pratt proprietary is the understand of the various failures of a gearbox to very accurately predict a failure. Pratt also went into several failure modes that apply in an aviation gearbox but not a ground based one and figured out how to mitigate a bunch of the risks (mostly via better cooling distribution).

Thanks guys. There is an elephant in the room, of course,
Let's say it is the morning of Nov. 1, 2016, and the boys in Chicago get a definitve report that the first 12-18 months of GTF operation have been superbly successful, and the LEAP is going to have problems keeping-up, Sure, B can then go to P&W and talk GTF, while GE starts-out on a GTF-clone(or whatever). But the horse will be long gone. Ooh-la-la!

cheers Bill

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: SEPilot
Posted 2012-12-11 08:29:38 and read 5643 times.

Quoting brindabella (Reply 36):
There is an elephant in the room, of course,
Let's say it is the morning of Nov. 1, 2016, and the boys in Chicago get a definitve report that the first 12-18 months of GTF operation have been superbly successful, and the LEAP is going to have problems keeping-up, Sure, B can then go to P&W and talk GTF, while GE starts-out on a GTF-clone(or whatever). But the horse will be long gone. Ooh-la-la!

This is the exact point I was alluding to earlier. If PW can get the GTF reliable enough it is a game changer. They can more easily incorporate the technology that the others are using than the others can add gearboxes. I think the big loser in this scenario will be Boeing, as the MAX will not have the option of using the GTF while the NEO will have it. Unless, of course, the contract with GE has an escape clause that allows them to add another engine if the LEAP is significantly outclassed. I suspect it will not take Boeing a long time to add the GTF to the MAX, as the actual engine mounting is a fraction of the changes required. I think the real problems will come in the contract with GE. But in any case it will be a huge setback for them.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: frmrcapcadet
Posted 2012-12-11 09:29:45 and read 5529 times.

Suppose Boeing (actually the airlines - airlines ordering the neo will have the same concern) have an escape clause allowing an engine switch. Does anyone have any idea if Boeing has contingency plans, and how complicated would it all be. I suppose that if anyone has details on how airbus will enable either engine that would give us some clues. The magnitude of failure to meet performance will be a mighty incentive for the Leap engine.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: autothrust
Posted 2012-12-11 09:47:32 and read 5488 times.

Quoting tdscanuck (Reply 15):
But a lot has happened to jet engines since then and the SSME has remained pretty static.

True but the SSME have got upgrades as well and the reliability were enhanced too.

Quoting nomadd22 (Reply 20):
Much less complicated than the modern jet engine.

Disagree, the SSME was almost ridiculously complicated compare to any jet engine out there.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: dynkrisolo
Posted 2012-12-11 10:03:30 and read 5450 times.

Quoting lightsaber (Reply 6):
In particular the scaloped low compressor and the 7 stage low compressor

7 stage low compressor? I don't think I have ever heard any engines with 7 stages of low compressor. Do you mean low turbine?

Based on this picture:

http://leehamnews.files.wordpress.com/2012/02/leap_3.jpg

I can count 3 stages of low comrpessor, and 6 stages of low turbine.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: tdscanuck
Posted 2012-12-11 10:56:07 and read 5361 times.

Quoting dynkrisolo (Reply 40):
http://leehamnews.files.wordpress.com/2012/02/leap_3.jpg

I think it's absolutely hilarious that they're including "Direct Drive" as a "technology for performance and durability". Sure, it's technically true, but it's hardly a technology. They might as well just scream "We have shafts!" in bold letters.

Tom.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: RickNRoll
Posted 2012-12-11 12:02:36 and read 5223 times.

Quoting tdscanuck (Reply 41):
I think it's absolutely hilarious that they're including "Direct Drive" as a "technology for performance and durability". Sure, it's technically true, but it's hardly a technology. They might as well just scream "We have shafts!" in bold letters.

They all do it. To quote Madmen "It's toasted".

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: ContnlEliteCMH
Posted 2012-12-11 13:43:05 and read 5107 times.

Quoting SEPilot (Reply 37):
This is the exact point I was alluding to earlier. If PW can get the GTF reliable enough it is a game changer. They can more easily incorporate the technology that the others are using than the others can add gearboxes.

Why can P&W more easily incorporate GE's technology for higher temps than GE can add a gearbox? One of the major changes GE is working on involves new materials, including the industrial processes to manufacture and assemble them. That's big-time work and shouldn't be trivialized.

What details make this statement true? What is it about adding a gearbox that is so much more difficult (and time consuming) than the technology changes GE is adding to the LEAP?

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: ferpe
Posted 2012-12-11 14:58:59 and read 4995 times.

Quoting ContnlEliteCMH (Reply 43):
What details make this statement true? What is it about adding a gearbox that is so much more difficult (and time consuming) than the technology changes GE is adding to the LEAP?

I don't think it is what technology is the more difficult to develop, it is about what technology has more long-term potential.

There are several signs the geared technology has the longer legs, one being RR going in bed with PW on the geared technology despite having invested heavily in their alternative 3 shaft technology and developing high turbine technology almost to the pace of GE.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: mffoda
Posted 2012-12-11 15:55:48 and read 4942 times.

Quoting ferpe (Reply 44):
There are several signs the geared technology has the longer legs, one being RR going in bed with PW on the geared technology despite having invested heavily in their alternative 3 shaft technology and developing high turbine technology almost to the pace of GE.

That, and the fact RR would be out of the NB business anyway...   

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: JoeCanuck
Posted 2012-12-11 16:01:33 and read 4918 times.

Quoting ferpe (Reply 44):

I don't think it is what technology is the more difficult to develop, it is about what technology has more long-term potential.

I think both will be end up being developed concurrently in both camps. As the quest for even more efficiency goes on, the GTF's will go with higher pressures and the direct drive engines would be nuts to ignore the advantages of a gearbox on the fan.

Neither camp has the resources to do both at once, and of the two, I think that GE has taken the more technologically difficult road. That gearbox allows Pratt to get similar efficiencies as the Leap but without having to push the internals to their absolute limits requiring very exotic, (and currently unproven), materials.

Few people have doubts the GTF will work as advertised and the engines themselves will be stressed less than the GE offering so the longevity shouldn't be an issue either. Just putting the gearbox on an existing engine has been proven the concept.

GE has to get everything exactly perfect to compete and I bet that's causing some sleepless nights...but anybody would be nuts to count them out.

Here's a good comparison between the two. It's a year old but I think still basically accurate;

http://airinsight.com/2011/11/09/com...nes-gtf-vs-leap-maintenance-costs/

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: astuteman
Posted 2012-12-11 22:10:54 and read 4711 times.

Quoting ContnlEliteCMH (Reply 43):
major changes GE is working on involves new materials, including the industrial processes to manufacture and assemble them. That's big-time work and shouldn't be trivialized.

What details make this statement true?

Intuitively? Because aero engine makers are ALWAYS pushing the limits of materials and core temperatures across the range of their engines.
The GTF is no different. It too will run hotter than the CFM56 or V2500

The impression I get is that because the GTF is 3 years earlier to market, its materials and temperature technology will be slightly less mature for an acceptable level of risk.

It's very clear that once the engine architecture is fixed, then the art of what can be changed is limited.

GE can CREATE a GTF, but they can't stick a gearbox on the Leap-X

P+W might equally have limits on what they can incorporate into the GTF.
However I suspect they would be capable of making at least some technology insertions in terms of materials or temperatures without creating a new engine

Rgds

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: SEPilot
Posted 2012-12-12 06:38:50 and read 4492 times.

Quoting ContnlEliteCMH (Reply 43):
Why can P&W more easily incorporate GE's technology for higher temps than GE can add a gearbox? One of the major changes GE is working on involves new materials, including the industrial processes to manufacture and assemble them. That's big-time work and shouldn't be trivialized.

What details make this statement true? What is it about adding a gearbox that is so much more difficult (and time consuming) than the technology changes GE is adding to the LEAP?

Just look at how long PW has been working on the gearbox. If it were easy it would have been flying on the A340 25 years ago. Materials, once developed, are much easier for others to copy (or purchase.)

Quoting astuteman (Reply 47):
GE can CREATE a GTF, but they can't stick a gearbox on the Leap-X

P+W might equally have limits on what they can incorporate into the GTF.
However I suspect they would be capable of making at least some technology insertions in terms of materials or temperatures without creating a new engine

Excellent point.   

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: JoeCanuck
Posted 2012-12-12 09:49:08 and read 4364 times.

Quoting astuteman (Reply 47):
GE can CREATE a GTF, but they can't stick a gearbox on the Leap-X

Still, the Leap can make a good starting point. Other than the gearbox, the biggest difference between the two is the LPT stages. I imagine most, if not all, of the low pressure sections, (including the fan), would have to be changed due to the higher rotational speeds but the core might be able to transfer over relatively intact.

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: planemaker
Posted 2012-12-12 10:10:54 and read 4338 times.

For those interested, here is a link to a 6 page Boeing article about the NG's PIP outlining engine and aero tweaks. While not directly related to the MAX, obviously there will be a carry over. The propulsion efficiency improvements are detailed on pages 5 & 6.

http://www.boeing.com/commercial/aer...2_q4/pdfs/AERO_2012q4_article3.pdf

Topic: RE: Developing Leap Engine Technology For 737MAX
Username: lightsaber
Posted 2012-12-12 12:16:36 and read 4199 times.

Quoting brindabella (Reply 36):
Sure, B can then go to P&W and talk GTF, while GE starts-out on a GTF-clone(or whatever). But the horse will be long gone.

Or GE could pull it off with the turbine materials and Pratt makes a mistake.

Quoting dynkrisolo (Reply 40):
Do you mean low turbine?

Yes. Thank you for catching my typo.

Quoting astuteman (Reply 47):
P+W might equally have limits on what they can incorporate into the GTF.

GE is ahead on turbine materials and the scaloped compressor (we'll, SNECMA is ahead on that), but Pratt has been working on the turbine materials. Pratt is ahead with the variable fan nozzle (I can recall distinctly in 1999 when discussion on that topic along the lines of 'why aren't we doing this?!?)

The thing with a GTF is much of that advanced fan aerodynamics goes away with the GTF (as the fan is at a much more optimal mach #). Much of the technology in the LEAP-X that isn't in the GTF is to compensate for the high fan mach # and low compressor and turbine mach #'s. It is technology that has little (if any) benefit in a GTF.

Pratt made a very simple GTF to reduce risk. The first widebody GTF will have much more technology in it.

Quoting planemaker (Reply 50):
For those interested

Thank you. A 2% fuel burn reduction is not trivial.

Quoting JoeCanuck (Reply 49):
I imagine most, if not all, of the low pressure sections, (including the fan), would have to be changed due to the higher rotational speeds but the core might be able to transfer over relatively intact.

Pratt looked at recyling a 2 spool core for the GTF and the inlet air profile to the high compressor is enough different to justify a new core. It is possible to recycle the LEAP's core, but a bit of efficiency and durability would be sacrificed (in trade for a known entity). As you noted, the low spool would have to be basically a complete redo.


Lightsaber


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