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engine derivatives

Posted: Fri May 15, 2020 2:50 am
by Sokes
"The GEnx engine, that has been developed for the Boeing 787 Dreamliner and 747-8, is derived from a smaller core variant of the GE90, also featuring a fan with swept rotor blades."
https://en.wikipedia.org/wiki/General_Electric_GE90

I struggle to visualize this.
I can imagine one can put a bigger fan and abuse the engine or put a smaller fan and enjoy reduced maintenance cost.
But I can't imagine that one can just make a core smaller. That sounds like a total new engine development to me.
Does it mean same production technologies and same materials are used, but otherwise it's a new engine?

Re: engine derivatives

Posted: Fri May 15, 2020 7:47 am
by unimproved
No, it means they scaled down the GE90 core and tweaked it. That's it.

Re: engine derivatives

Posted: Sat May 16, 2020 5:36 am
by Sokes
unimproved wrote:
No, it means they scaled down the GE90 core and tweaked it. That's it.

You mean like in one dimension 10% shorter , in three dimensions 27,1 % smaller?
I don't think that works with flow of gases. Water flow through a pipe is not linear with pipe cross section.

Re: engine derivatives

Posted: Sat May 16, 2020 2:07 pm
by Dalmd88
I would bet the core is pretty much the same size, I work the Trent 1000 and we are preparing for Trent xwb work. I have not seen a XWB torn down yet, but I have seen the completed engine up close.

These two are pretty much the same as the two GE's in use. The core between the two Rolls products are very similar. The XWB does have an extra IPT stage And I think the LPT is a little larger. I think the diameter of the IPC and the HPC are the same in both engines. The biggest differences is the fan size.

Re: engine derivatives

Posted: Sun May 17, 2020 6:26 pm
by Sokes
Dalmd88 wrote:
The core between the two Rolls products are very similar. The XWB does have an extra IPT stage And I think the LPT is a little larger. I think the diameter of the IPC and the HPC are the same in both engines. The biggest differences is the fan size.


If one raises the embankment on major rivers for 1 m, all small streams that flow in that river also need to raise their embankment for 1 m. Alternatively one can put a pumping station. It's very high capacity, but also very low head. A new pumping station made a trial run. It had terrible vibration. They had to rebuild the inlet, then it was o.k.

Your story is amazing. The fun part is that it's the smaller engine that is having trouble. But I have no problem to believe it.
With flow of gases/ liquids there is very little I wouldn't believe.
I have to double post this video:
https://www.youtube.com/watch?v=15XJDmawbYU&t=315s

Re: engine derivatives

Posted: Mon May 18, 2020 4:46 pm
by jetlife2
The engines share the same architecture, but they are not scaled in the sense of starting with dimensions and factoring them. When you design an engine you start from scratch for the thrust requirement needed. The cycle falls out of the pressure ratio obtainable and the imposed temperature limit. Example, you are an OEM who has a compressor capable of 22:1 with a certain number of stages. Maintaining the number of stages, you size a new compressor for the flow needed at this pressure ratio, according to your objective for thrust, and the chosen temperature (T3) limit (function of your available materials stack). At the end you have a new machine that looks like a cousin of the one you had before. It was derived from the same architecture and level of technology. But not scaled.

Re: engine derivatives

Posted: Tue May 19, 2020 3:40 pm
by Sokes
Dalmd88 wrote:
The core between the two Rolls products are very similar. The XWB does have an extra IPT stage And I think the LPT is a little larger. I think the diameter of the IPC and the HPC are the same in both engines. The biggest differences is the fan size.


jetlife2 wrote:
Example, you are an OEM who has a compressor capable of 22:1 with a certain number of stages. Maintaining the number of stages, you size a new compressor for the flow needed at this pressure ratio, according to your objective for thrust, and the chosen temperature (T3) limit (function of your available materials stack).


It sounds as if you contradict each other. You may still be both right.

https://en.wikipedia.org/wiki/Rolls-Roy ... ifications
The Trent 500 and Trent 800 have very different thrust, but identical number of stages. I assume what you say applies.

The Tent XWB has two IP turbine stages as compared to one stage with Trent 1000. I would assume that the IP compressor of the Trent XWB does a greater proportion of required compression as compared to Trent 1000, even if stages of IP compressor and HP compressor are same in Trent XWB and Trent 1000.

Of course I just assume this.

Re: engine derivatives

Posted: Tue May 19, 2020 5:23 pm
by AECM
It's a balancing act at the end taking into account thrust requirements, maximum dimensions of the engine, weight, etc

All of the current Trent engines are based on a 3 shaft architecture

Trent 7000
Bypass ratio 10:1
Overall Pressure 50:1
Fan 112 in (284 cm) and 20 blades
8 IPC, 6 HPC, 1 HPT, 1 IPT, 6 LPT
Combustors annular, 18-off fuel spray nozzles
Air mass flow takeoff 1,300 kg/s / 2,900 lb/s
Maximum thrust: 324.0 kN

Trent XWB 84
Bypass ratio 9.6:1
Overall Pressure 50:1
Fan 118 in (300 cm) and 22 blades
8 IPC, 6 HPC, 1 HPT, 2 IPT, 6 LPT
Combustors annular, 20-off fuel spray nozzles
Air mass flow takeoff 1,436 kg/s / 3,166 lb/s
Maximum thrust: 375 kN

Re: engine derivatives

Posted: Wed May 20, 2020 8:23 am
by jetlife2
Sokes wrote:

It sounds as if you contradict each other. You may still be both right.



I was responding to the original comment about the relationship of the GEnx to the GE90 and whether the design was "scaled". Simply put dimensional scaling doesn't work, you are starting from scratch even if you are using the same layout. And as soon as you add or subtract stages you have an entirely different machine.