"Ok, but when one is climbing on turboprop and DO NOT touch the power levers, ITT remains constant ?"
Basically the turbine wants to get a certain mixture of air and fuel, constant please. Just like a piston engine, but by other means. So, as you climb the density of the air goes down. Meaning: less fuel will be injected, so the ITT should rather go down. Now, a lot of cooling in the engine is done by the air going through it - which is now less dense. So it wouldn´t stay exactly the same, but for the task of understanding it, yes it would, but torque (basically the delivered power) goes down. A lot of things do influence the temperature, in the PT6 installations I flew (mostly KingAir, some Cheyenne) you could increase the ITT by 20-30-40° by using anti ice - that would not use bleed air as in most jets, but open doors in the duct to the engine air inlet, basically taking a bit of air off. It also can depend on prop rpm, although usually to a lesser degree and also airspeed and OAT. A turbine engine has a relatively narrow operating range rpm/temperature wise in which it really "feels" well, as a turbine pilot you basically try to keep the engine in that range whilst observing the limits (like ITT, torque or N1/N2). I understand (while not experienced in these, the single shaft engines have narrower bands in respect of operating ranges.
An nice example for the internal cooling is the air condition on the KingAirB 200 - its connected with an electric clutch to the right engine. The KA200 has 2 idle settings (depending on the mounted props the figures differ a bit), something like 63% for low idle and 70% high idle. One should use high Idle when the a/c is on...now one would think the engine runs hotter at a higher power setting, but no sir, it actually runs a lot cooler at high idle, since there is more cooling through the engine (and as well through the oil cooler). To deal with this excess air most engines do have bleed air valves that open and close during engine acceleration, bleeding off excess air when required.
Last edited by His dudeness; 28th Mar 2019 at 21:02.