patrickjp93
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Why isn't the Trent XWB Having Issues?

Wed Nov 27, 2019 11:18 pm

Given the Trent 1000 TEN is still having compressor blade corrosion problems, when it's supposedly so much of a new engine compared to the package B and C versions, why is the Trent XWB somehow immune given they should now share so much of their architecture/materials?

The 787 and A350 took to the skies only 3 years apart and have had over half a decade of service overlap, so why can't RR sort out their T1000 problems even now and yet have the industry's single most reliable engine built out of so many components in common?
 
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zeke
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 4:16 am

The 787 wanted to extract so much power from the engine for electrical loads it s unconventional, the generators extract 1 megawatt of electricity, enough to power 1000 homes.

Gas turbines are efficient gas generators, when you want to extract so much load off the shaft it requires things to be redesigned.
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 5:58 am

zeke wrote:
The 787 wanted to extract so much power from the engine for electrical loads it s unconventional, the generators extract 1 megawatt of electricity, enough to power 1000 homes.

Gas turbines are efficient gas generators, when you want to extract so much load off the shaft it requires things to be redesigned.


I don't see what that has to do with turbine blade coatings. And for that matter, if the design has to be so radically different, why is a simple modification to the GEnX-2b all that's needed to mount it on a 748?
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zeke
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 6:24 am

RR have stated the reason the XWB engine does not have the same issues is the specific design requirements.

"I know that's easy to say, but it does come down to the detailed geometry, the detailed design of this particular engine." From https://www.flightglobal.com/news/artic ... yc-458567/

The 747-8 engine is not an optimum design, it is a “cheap” modification of the 787 engine, and as I understand not as efficient as the Trent 7000.
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 7:09 am

DocLightning wrote:
zeke wrote:
The 787 wanted to extract so much power from the engine for electrical loads it s unconventional, the generators extract 1 megawatt of electricity, enough to power 1000 homes.

Gas turbines are efficient gas generators, when you want to extract so much load off the shaft it requires things to be redesigned.


I don't see what that has to do with turbine blade coatings. And for that matter, if the design has to be so radically different, why is a simple modification to the GEnX-2b all that's needed to mount it on a 748?



Agreed. The identified problem with the Trent T1000 is premature fan blade erosion. Why is this different with the T1000 versus Trent engines on the A350?

Are the fan blades materially different? It would seem so. Although internal engine temps of as few as 20 F can allegedly drastically shorten the life of fan blades. Whatever the true cause it would be nice for RR to be transparent about the exact factors involved.
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zeke
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 7:42 am

They are not the same design, just because it is called a Trent does not mean they are the same. The RB211 is also a Trent.

The Trent 1000 has a single stage IP turbine, the XWB duel stage IP turbine, different engines designed for different applications.

About as dumb as saying all 4 door sedans are the same because they are 4 door sedans. The difference is in the detail, which is what RR has clearly stated.
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kitplane01
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 9:12 am

zeke wrote:
The 787 wanted to extract so much power from the engine for electrical loads it s unconventional, the generators extract 1 megawatt of electricity, enough to power 1000 homes.

Gas turbines are efficient gas generators, when you want to extract so much load off the shaft it requires things to be redesigned.


I don't think that makes sense. The power turbines are always putting power onto the shaft. If the power is consumed by the fan, the compressor, or the generator should make no difference to the turbine.
 
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zeke
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 10:13 am

kitplane01 wrote:
[f the power is consumed by the fan, the compressor, or the generator should make no difference to the turbine.


The primary role of an engine is to produce thrust, in cruise that is a fairly constant level, the engine cycle from intake, compression, combustion to exhaust is fairly constant.

Using the constant nature of this can be thought of like the normal running of a portable generator. However if you were to connect a large electrical load to that generator you get an immediate increased load on the engine, which for a portable generator you will see an initially a drop in RPM and then the RPM increase.

You cannot have sudden changes in RPM on a jet engine as it impacts the airflow through the engine.

The extraction of this variable power needs to be carefully designed not to detract from the engines primary role of producing thrust. Hence the comment from RR that it required specific geometry to meet the design goals.

Traditionally RR has always used the HP spool to extract power for the accessories, due to the larger power requirements this was moved to the IP spool.
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patrickjp93
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Re: Why isn't the Trent XWB Having Issues?

Thu Nov 28, 2019 3:42 pm

zeke wrote:
kitplane01 wrote:
[f the power is consumed by the fan, the compressor, or the generator should make no difference to the turbine.


The primary role of an engine is to produce thrust, in cruise that is a fairly constant level, the engine cycle from intake, compression, combustion to exhaust is fairly constant.

Using the constant nature of this can be thought of like the normal running of a portable generator. However if you were to connect a large electrical load to that generator you get an immediate increased load on the engine, which for a portable generator you will see an initially a drop in RPM and then the RPM increase.

You cannot have sudden changes in RPM on a jet engine as it impacts the airflow through the engine.

The extraction of this variable power needs to be carefully designed not to detract from the engines primary role of producing thrust. Hence the comment from RR that it required specific geometry to meet the design goals.

Traditionally RR has always used the HP spool to extract power for the accessories, due to the larger power requirements this was moved to the IP spool.


Frankly I don't believe that explanation at all. The corrosion will be occurring because of chemistry, not blade shape, and it's been proven that this premature wearing is mostly happening in sulphur-heavy environments. So it will be a problem of core blade materials and/or coatings, which means by now RR has zero excuse to still be having the issue when the XWB and 7000 seem to be performing flawlessly in the same environments.

As for the GEnx 2Bs not being as efficient as the T7000, that mostly is because the 2B is smaller than the 1B and has lower thrust. The T7000 has higher thrust than the 1000 on a similar architecture, so it would be operating closer to the architecture's red lines and limits, which is always more efficient, whereas the GEnx 2B would not. Frankly where the 2Bs would have shined would have been an A380 NEO. But oh well.
 
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kitplane01
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Re: Why isn't the Trent XWB Having Issues?

Sat Nov 30, 2019 10:26 pm

zeke wrote:
kitplane01 wrote:
[f the power is consumed by the fan, the compressor, or the generator should make no difference to the turbine.


The primary role of an engine is to produce thrust, in cruise that is a fairly constant level, the engine cycle from intake, compression, combustion to exhaust is fairly constant.

Using the constant nature of this can be thought of like the normal running of a portable generator. However if you were to connect a large electrical load to that generator you get an immediate increased load on the engine, which for a portable generator you will see an initially a drop in RPM and then the RPM increase.

You cannot have sudden changes in RPM on a jet engine as it impacts the airflow through the engine.

The extraction of this variable power needs to be carefully designed not to detract from the engines primary role of producing thrust. Hence the comment from RR that it required specific geometry to meet the design goals.

Traditionally RR has always used the HP spool to extract power for the accessories, due to the larger power requirements this was moved to the IP spool.


The turbine has to make power to
1) Propel the airplane
2) Power the systems

In a bleed air engine, the turbine does this by providing force into the shaft that spins the compressor and generator. The generator uses little power, and the compressor uses almost all the power. Some of the air is bled off, and used to power the system.

In an electric aircraft, the turbine does this by providing force into the shaft that spins the compressor and generator. The generator uses more power, and the compressor uses less power than before. But the total power required is just about the same. The turbine's job is the same.

The problems with the turbine are chemistry and mechanics and such. It doesn't know or care where the shaft-turning power goes.
 
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Re: Why isn't the Trent XWB Having Issues?

Sat Nov 30, 2019 10:30 pm

zeke wrote:
kitplane01 wrote:
[f the power is consumed by the fan, the compressor, or the generator should make no difference to the turbine.


The primary role of an engine is to produce thrust, in cruise that is a fairly constant level, the engine cycle from intake, compression, combustion to exhaust is fairly constant.

Using the constant nature of this can be thought of like the normal running of a portable generator. However if you were to connect a large electrical load to that generator you get an immediate increased load on the engine, which for a portable generator you will see an initially a drop in RPM and then the RPM increase.

You cannot have sudden changes in RPM on a jet engine as it impacts the airflow through the engine.



I really really doubt that the variations in power requirements are leading to mechanically significant variations in RPM. Has anyone (some pilot/engineer somewhere) actually seen this on a real plane? Does the manufacturer say somewhere quotable that this is the case? I really doubt this.
 
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zeke
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Re: Why isn't the Trent XWB Having Issues?

Sun Dec 01, 2019 12:01 am

kitplane01 wrote:

I really really doubt that the variations in power requirements are leading to mechanically significant variations in RPM. Has anyone (some pilot/engineer somewhere) actually seen this on a real plane? Does the manufacturer say somewhere quotable that this is the case? I really doubt this.


The gas turbines convert chemical energy into mechanical energy, if you need more mechanical energy to drive a higher electrical loads, more fuel is required. You simply will not notice this as it’s all transparent to the crew handled by the FADEC.

APUs which are just gas turbines with a generator and bleed vary RPM by about 10% depending of the load required., again these variations are all automatic handled by the FADEC. For example the Honeywell 331-350 APU (A330) under zero load will burn around 120 kg/hr, at maximum electrical load that will increase to 140 kg/hr.
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Re: Why isn't the Trent XWB Having Issues?

Sun Dec 01, 2019 10:59 pm

kitplane01 wrote:
I really really doubt that the variations in power requirements are leading to mechanically significant variations in RPM. Has anyone (some pilot/engineer somewhere) actually seen this on a real plane? Does the manufacturer say somewhere quotable that this is the case? I really doubt this.

And you're rightfully doubting !! ;)

zeke wrote:
The gas turbines convert chemical energy into mechanical energy, if you need more mechanical energy to drive a higher electrical loads, more fuel is required. You simply will not notice this as it’s all transparent to the crew handled by the FADEC.

Well, aircraft manufacturers still consider us useful enough to provide us with EGT and fuel flow gauges in the flight deck. And, thankfully for my heart, these indications are usually fairly stable.

kitplane01 wrote:
The problems with the turbine are chemistry and mechanics and such. It doesn't know or care where the shaft-turning power goes.
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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 3:46 am

zeke wrote:
kitplane01 wrote:

I really really doubt that the variations in power requirements are leading to mechanically significant variations in RPM. Has anyone (some pilot/engineer somewhere) actually seen this on a real plane? Does the manufacturer say somewhere quotable that this is the case? I really doubt this.


The gas turbines convert chemical energy into mechanical energy, if you need more mechanical energy to drive a higher electrical loads, more fuel is required. You simply will not notice this as it’s all transparent to the crew handled by the FADEC.

APUs which are just gas turbines with a generator and bleed vary RPM by about 10% depending of the load required., again these variations are all automatic handled by the FADEC. For example the Honeywell 331-350 APU (A330) under zero load will burn around 120 kg/hr, at maximum electrical load that will increase to 140 kg/hr.


It's NOT more load. Boeing says it's LESS load.

Please stop thinking bleed air is free. It required extra power from the turbine to make bleed air.

For some engines systems get powered by the compressor which is turned by the turbines. For other engines systems get powered by the generators which get powered by the turbine. Boeing says the second option is more efficient, and no one says it's less efficient.

It's NOT more load on the turbine!!!!
 
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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 4:44 am

kitplane01 wrote:

It's NOT more load. Boeing says it's LESS load.


Please provide a reference, the 787 engines are not bleed less.

The gas turbine engine is a far more efficient compressor than an electric pack.

Then there is the small matter of them not using the technology on the 747-8, and 737Max. Why not use the technology if it does provide a measurable improvement.
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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 6:09 am

zeke wrote:
kitplane01 wrote:

It's NOT more load. Boeing says it's LESS load.


Please provide a reference, the 787 engines are not bleed less.

The gas turbine engine is a far more efficient compressor than an electric pack.

Then there is the small matter of them not using the technology on the 747-8, and 737Max. Why not use the technology if it does provide a measurable improvement.


Boeing says the 787 is bleedless. See http://www.boeing.com/commercial/aeroma ... 2012_q1/4/

Boeing says the bleedless system is more effecient than a bleed system. "Boeing believes that using electrical power is more efficient than engine-generated pneumatic power, and expects the new architecture to extract as much as 35 percent less power from the engines. Conventional pneumatic systems generally develop more power than is needed in most conditions, causing excess energy to be dumped overboard." Same reference.
 
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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 7:50 am

zeke wrote:
The 787 wanted to extract so much power from the engine for electrical loads it s unconventional, the generators extract 1 megawatt of electricity, enough to power 1000 homes.

Gas turbines are efficient gas generators, when you want to extract so much load off the shaft it requires things to be redesigned.

so you're saying the gearbox is at fault? the accessory gear would be there anyway were there bleeds or not. the lack of bleeds should account for the mechanical power takeoff for the accessory Gearbox. so is the accessory gear drive what's been failing? I thought it was erosion of the Inlet stators or am I mistaken? And if so? PLEASE enlighten me because Aviation Week might have misunderstood..
 
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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 8:21 am

kitplane01 wrote:
zeke wrote:
kitplane01 wrote:

It's NOT more load. Boeing says it's LESS load.


Please provide a reference, the 787 engines are not bleed less.

The gas turbine engine is a far more efficient compressor than an electric pack.

Then there is the small matter of them not using the technology on the 747-8, and 737Max. Why not use the technology if it does provide a measurable improvement.


Boeing says the 787 is bleedless. See http://www.boeing.com/commercial/aeroma ... 2012_q1/4/


The aircraft is bleedless, that doesn´t mean the engine is. It just doesn´t have provide bleed air to the aircraft, it still uses bleed air internally.

Boeing says the bleedless system is more effecient than a bleed system. .


And they are so convinced of that statement that the 777x is back to bleed, despite major rework, and i am not sure i have seen a definitive statement that the NMA would be "more electric" as well...

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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 10:19 am

zeke wrote:
kitplane01 wrote:

It's NOT more load. Boeing says it's LESS load.


Please provide a reference, the 787 engines are not bleed less.

The gas turbine engine is a far more efficient compressor than an electric pack.

Then there is the small matter of them not using the technology on the 747-8, and 737Max. Why not use the technology if it does provide a measurable improvement.

the engine does use bleed for nose cowl anti-icing off the engines but NO engine bleed services the cabin for pressurization. It's all electrically generated which gived the engines more power to climb to altitude and faster. It appears that it extends the range as well. I'm not sure that the engine life is better with ni bleeds yet as I no longer actively work. though I suspect that it has to extend the life and improve the health of the Gas generator as the bleed is the first indication of trouble during trend monitoring, I'm almost sure they'd still be monitoring the Compressor outlet temp/pressure,Vs the Compressor inlet pressure and the turbine inlet temp or EGT to determine and internal shift in performance. United's 787's download takeoff performance data every leg so the Engine Maintenance controller can check it most every takeoff.
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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 10:47 am

strfyr51 wrote:
It's all electrically generated which gived the engines more power to climb to altitude and faster.


Not really.

Aircraft manufacturer based on preliminary design specifies required thrust. So, bleedless or bleed, it would require same amount of thrust.

However, due to this architecture, there are some considerations taking place. You have no inlets for bleed air, and no pipes (except for antiice, which are probably what Zeke said). Instead, a larger and stronger AC generator is taking energy from engine. Boeing claims energy taken from shaft to convert to electric, transfer electric power and generate pressure on board comes cheaper to generate and maintain, than standard bleed air architecture. Whether it is so - hard to say. I see too many energy converters there (each bringing its own losses) to simply agree. But until calculations and assumptions are published, everything is pure speculation. Also on MX side, comparing electric equipment (which is known to have problems occasionally) to simple, mostly mechanic piping of bleed air. SImple usually is less prone to faults.

So, it will not allow to climb higher, since it does not have more thrust. It could be smaller to achieve same thrust, or maybe more effective (again: smaller/lighter that bleed air architecture) - if Boeing numbers are correct. It still remains to see, though, as no other plane has bleedless architecture, and AFAIK no tests were conducted to confirm performance of bleedless vs bleed air head to head.

Cheers,
Adam

PS. Time to get back on topic, which is TrentXWB, not 787 bleedair architecture.
 
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Re: Why isn't the Trent XWB Having Issues?

Wed Dec 04, 2019 7:42 pm

gloom wrote:
strfyr51 wrote:
It's all electrically generated which gived the engines more power to climb to altitude and faster.


Not really.

Aircraft manufacturer based on preliminary design specifies required thrust. So, bleedless or bleed, it would require same amount of thrust.

However, due to this architecture, there are some considerations taking place. You have no inlets for bleed air, and no pipes (except for antiice, which are probably what Zeke said). Instead, a larger and stronger AC generator is taking energy from engine. Boeing claims energy taken from shaft to convert to electric, transfer electric power and generate pressure on board comes cheaper to generate and maintain, than standard bleed air architecture. Whether it is so - hard to say. I see too many energy converters there (each bringing its own losses) to simply agree. But until calculations and assumptions are published, everything is pure speculation. Also on MX side, comparing electric equipment (which is known to have problems occasionally) to simple, mostly mechanic piping of bleed air. SImple usually is less prone to faults.

So, it will not allow to climb higher, since it does not have more thrust. It could be smaller to achieve same thrust, or maybe more effective (again: smaller/lighter that bleed air architecture) - if Boeing numbers are correct. It still remains to see, though, as no other plane has bleedless architecture, and AFAIK no tests were conducted to confirm performance of
bleedlesss vs bleed air head to head.

Cheers,
Adam

PS. Time to get back on topic, which is TrentXWB, not 787 bleedair architecture.

One nitpick, T1000 also uses compressor air for turbine clearance control.

Also, electrical systems are far easier to diagnose and repair.

Cost to develop:
Pneumatic (chespest)
Hydraulic
Electrical (all the software testing makes it the most expensive).

Cost to maintain:
Electrical (cheapest)
Hydraulic (leaks)
Pneumatic (Valves wear under heating, leaks, makes these the most maintenance intensive).


I agree a turbine knows load, the GEnX has no similar issue. This is chemistry. Some material change that was important.

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kitplane01
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Re: Why isn't the Trent XWB Having Issues?

Thu Dec 05, 2019 5:58 am

tommy1808 wrote:
kitplane01 wrote:
zeke wrote:

Please provide a reference, the 787 engines are not bleed less.

The gas turbine engine is a far more efficient compressor than an electric pack.

Then there is the small matter of them not using the technology on the 747-8, and 737Max. Why not use the technology if it does provide a measurable improvement.


Boeing says the 787 is bleedless. See http://www.boeing.com/commercial/aeroma ... 2012_q1/4/


The aircraft is bleedless, that doesn´t mean the engine is. It just doesn´t have provide bleed air to the aircraft, it still uses bleed air internally.

Boeing says the bleedless system is more effecient than a bleed system. .


And they are so convinced of that statement that the 777x is back to bleed, despite major rework, and i am not sure i have seen a definitive statement that the NMA would be "more electric" as well...

best regards
Thomas


They did not move the 777X or 747-8x or the 737neo to bleedless because they didn't want to redesign those systems for a number of reasons including cost and backward compatibility and certification risk. There only brand new plane in the last 20 years is bleedless.

This seems simple to me. Boeing says it's better and gives numbers. You can either think they're wrong, or they're lying. But they do say it, more than once, several times. And on their only brand new design, used it. I chose to believe them. You make your choice.

P.S. to strong-man the counter argument, Airbus did not go bleedless on the A350. Which is interesting. There has already been a thread about this, and a fair summary might be "For whatever reason, Airbus believes that a bleedless, all-electric architecture does not provide enough of an advantage to take the risks that Boeing had to take in the fundamental change of design.". viewtopic.php?t=766083
 
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Re: Why isn't the Trent XWB Having Issues?

Thu Dec 05, 2019 6:12 am

kitplane01 wrote:
There only brand new plane in the last 20 years is bleedless.


only one brand new plane in the last 20 years is bleedless. Fixed it for you.

MC21, MRJ, A220, A350, A380, SSJ .... all brand new, all younger than 20 years. All with bleed. And again, no mention of bleedless or more electric plane for the New Midsize Airplane either that i can find.

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zeke
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Re: Why isn't the Trent XWB Having Issues?

Thu Dec 05, 2019 5:44 pm

kitplane01 wrote:

Please stop thinking bleed air is free. It required extra power from the turbine to make bleed air.

For some engines systems get powered by the compressor which is turned by the turbines. For other engines systems get powered by the generators which get powered by the turbine. Boeing says the second option is more efficient, and no one says it's less efficient.

It's NOT more load on the turbine!!!!


I have never suggested bleed air is free, however like the pressure and temperature drop over the power turbine to drive the compressor, to generate the torque required to drive a generator and hydraulic pumps it is also done by a pressure and temperature drop across the power turbine.

The Trent XWB engine and the Trent 1000/Genx all have 3 things in common
1) they all have hydraulic pumps driven off the engine
2) they all have bleed air extracted from the engine
3) they all have generators driven off the engine

The difference is in the proportions.

1) both the 787/A350 have two hydraulic circuits running at 5000 psi driven directly from the engines, the torque to drive the pumps comes from the power turbine (via a pressure and temperature drop). The 787 has a 3rd circuit which is electrically driven very similar to an A320 architecture, the electricity used to power the electric pump comes from the generator which is driven by torque extracted from the power turbine . The Trent XWB system here is more efficient as it only has two circuits.

2) Bleed air is used within the engines for nacelle heating as well as internally to control the position of vanes etc. The bleed air is extracted from different parts of the engine depending on its end use as well as the stage of flight, eg ground or in air.

While the XWB engine has bleed air extracted to drive the ECS, the Trent 1000/Genx extract power from the power turbine drive higher electrical loads that are used for the ECS. The generator does extract power from the engine, this does increase fuel burn compared to no generator load. To generate electricity is not a 100% efficient process, there is losses extracting power via a power turbine, there is mechanical losses between the engine and generator, the generator is not 100% efficient converting mechanical energy into electrical energy, the electricity needs to be conditioned, and the electrical switch gear and distribution has to be supersized to handle the much higher electrical loads.

What is common between the two architecture types is the energy to drive the ECS has to be transmitted from the engine to the ECS. This is where the Trent 1000/Genx is more efficient as it does not need an additional reticulation of bleed air from the engine to the ECS. However the Trent 1000/Genx requires more complex electrical power conditioning and distribution, it then requires the electrical energy then to convert the electrical power back into a thermodynamic process to compress and heat the air. The power to drive the ECS regardless of the architecture has to be transported from the engine to the ECS, one system uses air at a very similar pressure to a car tyre, the other uses electrical cables.

As I have demonstrated the driving the ECS electrically has a number of additional losses to convert high pressure air into torque, mechanical losses, generating losses, transmission losses, electrical power conditioning losses,electric power distribution losses, and thermodynamic losses in the electric compressor. Downstream of the packs the distribution of cabin air is near identical.

3) Both the Trent XWB and Trent 1000/Genx use two generators per engine, to drive those generators power is extracted from the power turbine to drive the electrical generators. The Trent XWB is more efficient here as it does not require as much power to be extracted from power turbine to drive the generators, the conditioning, distribution, and control of the electrical system is simpler with the XWB as the power levels are much lower. The Trent 1000/Genx also has to extract more power to run the third hydraulic circuit on the 787. As the electrical loads being extracted on the Trent 1000 are much higher than other engines, they had to change the spool this was done from.

strfyr51 wrote:
the accessory gear would be there anyway were there bleeds or not. the lack of bleeds should account for the mechanical power takeoff for the accessory Gearbox.


To account foe the much higher loads being taken from the turbine to drive the additional electrical loads, RR had to move the power extraction to a different spool. Please refer to my reply #4 above where RR have stated the reason why the XWB engine will not see the same problems as the Trent 1000 are due to the specific geometry required on the Trent 1000 to meet the engine design requirements.

The article I linked in reply #4 basically sums up the thread "Why isn't the Trent XWB Having Issues?"

strfyr51 wrote:
It's all electrically generated which gived the engines more power to climb to altitude and faster.


Regardless of how energy is transmitted from the engine to drive the ECS (bleed air or electricity), it requires power to be extracted from the engine.

lightsaber wrote:
I agree a turbine knows load, the GEnX has no similar issue. This is chemistry. Some material change that was important


I disagree with what you are saying with bleed air systems, what is being used on new aircraft today is very different to 20-30 years ago, The systems are far ore reliable, have much better monitoring and control, and have significantly improved packs. What they have done is used big data and machine learning of in service data in ECS design to reduce maintenance and improve reliability of the new systems.

I haven't seen any evidence to suggest the GEnx is not having issues, how many performance improvement packages has the engine seen already ?

"The new durability upgrade—which includes modifications to the GEnx-1B’s high-pressure turbine (HPT) first-stage nozzles and blades, as well as its combustor lining and fuel nozzles— will offer operators of GEnx-1B-powered 787s approximately 30 percent more time on wing, according to Mackenzie. It follows an earlier, less major durability upgrade that GE introduced along with its PIPS II performance improvement package for the GEnx-1B and PIP package for the GEnx-2B powering the Boeing 747-8 four years ago. GE managed to incorporate the first, incremental durability upgrade into every engine in the in-service fleet within two years and similarly expects to complete retrofitting the new durability upgrade package in all in-service GEnx-1B-powered 787s—there were 414 such aircraft in service by early June—within a two-year period, she said."

from https://www.ainonline.com/aviation-news ... ty-upgrade

Please refer to my reply #4 where RR have stated the reason the XWB does not have the same issues as the Trent 1000 are specific geometry issues that were required to meet the design requirements.
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kitplane01
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 4:14 am

tommy1808 wrote:
kitplane01 wrote:
There only brand new plane in the last 20 years is bleedless.


only one brand new plane in the last 20 years is bleedless. Fixed it for you.

MC21, MRJ, A220, A350, A380, SSJ .... all brand new, all younger than 20 years. All with bleed. And again, no mention of bleedless or more electric plane for the New Midsize Airplane either that i can find.

best regards
Thomas


Funny, but missing the point. Also, I was wrong thanks for the correction.

No one said bleedless was better than sliced bread. Boeing said it makes the engine works less hard when bleedless. No one (Airbus, Mitsubishi, etc) is contradicting that. Boeing also said there is a cost and a risk, which these others are unwilling to pay.

So, either believe Boeing or not. But Airbus choosing to use the older technology does not change the truth of what Boeing has repeatedly said.
 
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kitplane01
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 4:21 am

zeke wrote:
kitplane01 wrote:

Please stop thinking bleed air is free. It required extra power from the turbine to make bleed air.

For some engines systems get powered by the compressor which is turned by the turbines. For other engines systems get powered by the generators which get powered by the turbine. Boeing says the second option is more efficient, and no one says it's less efficient.

It's NOT more load on the turbine!!!!


While the XWB engine has bleed air extracted to drive the ECS, the Trent 1000/Genx extract power from the power turbine drive higher electrical loads that are used for the ECS. The generator does extract power from the engine, this does increase fuel burn compared to no generator load. To generate electricity is not a 100% efficient process, there is losses extracting power via a power turbine, there is mechanical losses between the engine and generator, the generator is not 100% efficient converting mechanical energy into electrical energy, the electricity needs to be conditioned, and the electrical switch gear and distribution has to be supersized to handle the much higher electrical loads.

What is common between the two architecture types is the energy to drive the ECS has to be transmitted from the engine to the ECS. This is where the Trent 1000/Genx is more efficient as it does not need an additional reticulation of bleed air from the engine to the ECS. However the Trent 1000/Genx requires more complex electrical power conditioning and distribution, it then requires the electrical energy then to convert the electrical power back into a thermodynamic process to compress and heat the air. The power to drive the ECS regardless of the architecture has to be transported from the engine to the ECS, one system uses air at a very similar pressure to a car tyre, the other uses electrical cables.

As I have demonstrated the driving the ECS electrically has a number of additional losses to convert high pressure air into torque, mechanical losses, generating losses, transmission losses, electrical power conditioning losses,electric power distribution losses, and thermodynamic losses in the electric compressor. Downstream of the packs the distribution of cabin air is near identical.


Problem. Boeing says that converting the mechanical energy into electricity, and using that to run compressors is MORE efficient that piping compressed air all around. Repeatedly. And they have acted on that belief when designing the 787.

This fact surprises me. My analysis would have been like yours. But they're in a better position to know the actual efficiencies than us.
 
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 4:36 am

kitplane01 wrote:

Problem. Boeing says that converting the mechanical energy into electricity, and using that to run compressors is MORE efficient that piping compressed air all around. Repeatedly. And they have acted on that belief when designing the 787.

This fact surprises me. My analysis would have been like yours. But they're in a better position to know the actual efficiencies than us.


When you can actually produce data that states their comparisons are against today’s technology please present it. Everything you claim Boeing has stated, you have t actually shown the statements.

All the comparisons Boeing made regarding technology improvements I saw all related to the 767.

Show us all where Boeing has said the technology is better than the 737Max, 747-8, 77X, A350 etc. Should be very easy for you to show the hard data to support your view.
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 5:59 am

kitplane01 wrote:
No one said bleedless was better than sliced bread. Boeing said it makes the engine works less hard when bleedless. No one (Airbus, Mitsubishi, etc) is contradicting that. Boeing also said there is a cost and a risk, which these others are unwilling to pay.

So, either believe Boeing or not. But Airbus choosing to use the older technology does not change the truth of what Boeing has repeatedly said.


Boeing also repeatedly said that the 737Classic is better than the A320, that the A320neo is only catching up to the 737NG, said "look, 787 roll out" when it was held together by fasteners from Home Depot and that the MAX was flown into the ground by incompetent pilots and the plane is safe........aside of Marketing not being honest as par for the course, Boeing doesn´t exactly have a track record of not misleading the public. They had an idea that had sound principles underneath, they tried it, didn´t scale as they expected and doesn´t seem to be worth the hassle. Don´t hold your breath to wait for them to say that out loud......

This very thread is about the Trend XWB being reliable and the Trent 1000 not being reliable because going bleedless makes the engine work harder where it matters for reliability. I guess that means Rolls Royce is contradicting Boeing. They are an Engine Maker, Boeing is an Aircraft maker....mmmm .... might be that Boeing just has a major case of Dunning Kruger, but i think its just marketing with a bit of avoiding law suits.

best regards
Thomas
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gloom
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 7:52 am

kitplane01 wrote:
So, either believe Boeing or not. But Airbus choosing to use the older technology does not change the truth of what Boeing has repeatedly said.


Well, I'd rather have facts than beliefs. FAA chose to believe. You chose to believe. But don't state Boeing claims as facts, until they're proven. I have seen little evidence to prove the belief is a fact. And that's all I need. Otherwise, discussion is pointless.

Cheers,
Adam
 
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JerseyFlyer
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 12:15 pm

zeke wrote:
RR have stated the reason the XWB engine does not have the same issues is the specific design requirements.

"I know that's easy to say, but it does come down to the detailed geometry, the detailed design of this particular engine." From https://www.flightglobal.com/news/artic ... yc-458567/

The 747-8 engine is not an optimum design, it is a “cheap” modification of the 787 engine, and as I understand not as efficient as the Trent 7000.


Does the specific geometry of the T1000, being required for electric generation, extend by default to the T7000 which is a bleed version of the T1000?
 
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 5:28 pm

zeke wrote:
kitplane01 wrote:

Problem. Boeing says that converting the mechanical energy into electricity, and using that to run compressors is MORE efficient that piping compressed air all around. Repeatedly. And they have acted on that belief when designing the 787.

This fact surprises me. My analysis would have been like yours. But they're in a better position to know the actual efficiencies than us.


When you can actually produce data that states their comparisons are against today’s technology please present it. Everything you claim Boeing has stated, you have t actually shown the statements.

All the comparisons Boeing made regarding technology improvements I saw all related to the 767.

Show us all where Boeing has said the technology is better than the 737Max, 747-8, 77X, A350 etc. Should be very easy for you to show the hard data to support your view.


I already did upthread.

See http://www.boeing.com/commercial/aeroma ... 2012_q1/4/

Boeing says the bleedless system is more effecient than a bleed system. "Boeing believes that using electrical power is more efficient than engine-generated pneumatic power, and expects the new architecture to extract as much as 35 percent less power from the engines. Conventional pneumatic systems generally develop more power than is needed in most conditions, causing excess energy to be dumped overboard."
 
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 5:46 pm

kitplane01 wrote:
They did not move the 777X or 747-8x or the 737neo to bleedless because they didn't want to redesign those systems for a number of reasons including cost and backward compatibility and certification risk. There only brand new plane in the last 20 years is bleedless.

This seems simple to me. Boeing says it's better and gives numbers. You can either think they're wrong, or they're lying. But they do say it, more than once, several times. And on their only brand new design, used it. I chose to believe them. You make your choice.

P.S. to strong-man the counter argument, Airbus did not go bleedless on the A350. Which is interesting. There has already been a thread about this, and a fair summary might be "For whatever reason, Airbus believes that a bleedless, all-electric architecture does not provide enough of an advantage to take the risks that Boeing had to take in the fundamental change of design.". viewtopic.php?t=766083

Airbus did not go bleedless on the A350 because they had just developed the A380 systems and had a perceived "time to market" crunch for A350 so they largely adapted the A380 tech for A350.
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zeke
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Re: Why isn't the Trent XWB Having Issues?

Fri Dec 06, 2019 8:59 pm

kitplane01 wrote:
I already did upthread.


No you didnt.

kitplane01 wrote:
Boeing says the bleedless system is more effecient than a bleed system.


To be clear to anyone following this, Boeing didnt write that quote, you did.

kitplane01 wrote:
"Boeing believes that using electrical power is more efficient than engine-generated pneumatic power, and expects the new architecture to extract as much as 35 percent less power from the engines. Conventional pneumatic systems generally develop more power than is needed in most conditions, causing excess energy to be dumped overboard."


That is not data, and does not compare it to comparable technology. Their "belief" is nothing more than their opiinin. Boeing does not design or build ECS, that is done by 3rd parties.

UTC Aerospace which designed and built the ECS on the 787 had this to say "Notably, Airbus did not follow the 787’s lead with its later-built A350, which uses an electro-pneumatic bleed-air system that it describes as “more efficient at the aircraft level.”"

that is from this article https://www.mro-network.com/engineering ... e-electric

This is what they say regarding the comparison between an electric vs pneumatic ECS

"“Aircraft designers’ preferences are influenced by balancing overall energy optimization at the aircraft level,” says UTC’s Bill Dolan, adding: “Depending on the aircraft and ECS configuration, it could be more efficient to generate pressurized air using an electric compressor.”"

Liebherr say

“There will be some aircraft in the future for which it will make sense to fully replace pneumatic power by electrical power. However, we are convinced that for other aircraft pneumatic power will remain the best-suited technology,”

Note, neither say anything about electric being 35% more efficient, or using 35% less power from the engine.

“Aircraft designers’ preferences are influenced by balancing overall energy optimization at the aircraft level,” says UTC’s Bill Dolan, adding: “Depending on the aircraft and ECS configuration, it could be more efficient to generate pressurized air using an electric compressor.”

Electric systems are no magic bullet, however, and involve several tradeoffs with regard to cost, weight and reliability. More-electric aircraft require bigger and heavier generators, for example, and the 787 was beset by electrical quirks in its first few years of service. Notably, Airbus did not follow the 787’s lead with its later-built A350, which uses an electro-pneumatic bleed-air system that it describes as “more efficient at the aircraft level.”

“Aircraft OEMs have been striving, and still strive, for substantial progress in cost, weight, reliability and maintainability,” says Nicolas Bonleux, managing director and chief commercial officer of Liebherr-Aerospace & Transportation. “All those aspects have been driving them to rely more and more on pneumatic power, at least as long as electrical technologies have not reached the sufficient level of performance.”

Nonetheless, Liebherr is making significant investment in electric systems as well as in its traditional pneumatic specialties. Among its new products are hybrid electro-pneumatic bleed-air systems for the A330neo and Embraer E2, and trials of all-electric, bleedless systems on A320 and ATR test aircraft.

In the future, Bonleux says, the choice between electric and pneumatic will come down to specific aircraft configurations and the technology used by other onboard systems. “There will be some aircraft in the future for which it will make sense to fully replace pneumatic power by electrical power. However, we are convinced that for other aircraft pneumatic power will remain the best-suited technology,” he says.
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Re: Why isn't the Trent XWB Having Issues?

Sat Dec 07, 2019 5:31 am

zeke wrote:
kitplane01 wrote:
I already did upthread.


No you didnt.

kitplane01 wrote:
Boeing says the bleedless system is more effecient than a bleed system.


To be clear to anyone following this, Boeing didnt write that quote, you did.



Actually, that's not a quote. The quote was given both in the post you're quoting, and a upthread. To be clear, it was
"Boeing believes that using electrical power is more efficient than engine-generated pneumatic power, and expects the new architecture to extract as much as 35 percent less power from the engines. Conventional pneumatic systems generally develop more power than is needed in most conditions, causing excess energy to be dumped overboard."

Source: https://www.boeing.com/commercial/aerom ... _02_1.html
 
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kitplane01
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Re: Why isn't the Trent XWB Having Issues?

Sat Dec 07, 2019 5:37 am

zeke wrote:

kitplane01 wrote:
"Boeing believes that using electrical power is more efficient than engine-generated pneumatic power, and expects the new architecture to extract as much as 35 percent less power from the engines. Conventional pneumatic systems generally develop more power than is needed in most conditions, causing excess energy to be dumped overboard."


...

"“Aircraft designers’ preferences are influenced by balancing overall energy optimization at the aircraft level,” says UTC’s Bill Dolan, adding: “Depending on the aircraft and ECS configuration, it could be more efficient to generate pressurized air using an electric compressor.”"

...


That's interesting, but UTC is a supplier of pneumatic systems.

That Airbus went pneumatic with the A350 is a better argument that pneumatic systems are a good choice. That's been argued in a different thread. Many argued that Airbus didn't want to take the development/certification risk, and wanted to use A380 developed technology. We need not repeat it here.

Here's my question: As to the 787, do you think Boeing is lying, or wrong, or what?
 
1989worstyear
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Re: Why isn't the Trent XWB Having Issues?

Sat Dec 07, 2019 6:14 am

zeke wrote:
kitplane01 wrote:

Problem. Boeing says that converting the mechanical energy into electricity, and using that to run compressors is MORE efficient that piping compressed air all around. Repeatedly. And they have acted on that belief when designing the 787.

This fact surprises me. My analysis would have been like yours. But they're in a better position to know the actual efficiencies than us.


When you can actually produce data that states their comparisons are against today’s technology please present it. Everything you claim Boeing has stated, you have t actually shown the statements.

All the comparisons Boeing made regarding technology improvements I saw all related to the 767.

Show us all where Boeing has said the technology is better than the 737Max, 747-8, 77X, A350 etc. Should be very easy for you to show the hard data to support your view.


The 737 MAX, 748, 777X, A320 NEO are all grandfathered to 20th Century type certificates. I would think this would be one of the reasons they're not bleedless.
Stuck at age 15 thanks to the certification date of the A320-200 and my parents' decision to postpone having a kid by 3 years. At least there's Dignitas...

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