Efficiency of Gasturbines (i.E. PW 4000 or similar)

[Christian Veit]

Can anyone tell me what the approximate efficiency of standard aircraft gasturbines would be? I always thought that the efficiency is way better than i.e. Dieselengines but i am not so sure anymore.

[jetfueldrinker]

It is true that gas turbine engines are more efficient than piston engines. This is due to many factors; each part of a jet engine is designed for a specific purpose, the combustion cycle is continuous as opposed to a piston engine whoes cycle is one power stroke for 4 cycles of movement, or 2 in the case of 2 stroke engines.

When I saw this posting I tried to find my BTEC notes (all be it 20 years old) as we covered this subject in some depth to give you some long forgotten facts and figures, but I think they got binned when we moved house. I hope that what I have written is at least a start, and hopefully some bright spark or smart arse will come to our aid!

JFD

[roo 2]

fuel consumtion is worked out with the Specific Fuel Comsumption formula,which is ibs of fuel consumed per hour over thrust(which is the difference between inlet air velocity and thrust nozzle velocity[out let velocity]).The efficency also depends on the compressors ability to compress the air without to much loss in pressure.It also depends on the outside air temp and altitude.The speed of the aircraft so in that it will increase it's RAM EFFECT.Turbine Inlet Temp is also a variable in the engines effiency.The hotter the gas stream the more efficent the engine will become. As a whole jet A1 has a higher calorific value(measured in BTU's,which is about 18,300)than diesel.So the fuel is more efficent in terms of weight and volume. So it's not a simple question of which is more efficent becuase there are many variables in the operation of a gas turbine,in fact there are many more workings that go into figureing out the efficency.But as a whole I would say a Gas Turbine is more efficent,depending on !!!!!!!!!!!!!.Good luck in your quest

[SchmiteGoBust]

Hi Christian,
I seem to remember an overall efficiency figure of around 70% for RB211 engine. Best efficiency for piston engines is around 20-30% area. Steam engines are lower around 10% but are much more fun!! Don't quote me on these figures by the way as they are based on memory of a long time ago. They are roughly right though.