Hello everyone,
The efficiency of a gas turbine engine increases with:
A) an increase in ambient temperature
B) an increase in volumetric efficiency
C)a decrease in ambient air pressure
D) a decrease in ambient air temperature
While A &C are obviously wrong, having already gotten this question incorrect, could you please tell me why the answer more fitting is D and not B? I understand that a decrease in air temp increases air density, which has the effect of "naturally" increasing mass flow thorough the engine, without making the engine work more to artificially produce (faster compressor spin rate) the same amount of thrust for any give throttle position. Mass flow and acceleration imparted upon a given mass of air are after all the main factors which influence thrust production as I have been taught.
Now, isn't "an increase in volumetric efficiency" a better choice and an overall better answer in terms of terminology since it implies than an engine with better VE has better mass flow through the engine at all times, in any given ambient conditions compared with one of less VE? Thus, the answer can cover a broader range of all variables than just lower amb. temp, although this answer is technically correct as well.
Or is this term more generally reserved to performance discussion relating to piston engines and should not be used with gas turbines?
Thank you