Simulation models for aero engines

[andyfromaero]

Hello all,


I'm a flight dynamicist / flight control designer, and I've got a propulsion question for you all.

We're trying to simulate a range of aircraft (both civil and military). However, we certainly don't need 6-degree-of-freedom simulation models of each aeroplane. We only need to model the aircraft as point masses performing simple manoeuvres, like climbs, descents and coordinated turns. (The aircraft only need to appear as echoes on an ATC radar screen).

However, we'd still like to compute the aircraft flight paths with adequate realism. Whilst there's a range of aircraft performance modelling methods available, using equations of motion, there seems to be very little for calculating engine thrust.

The descriptions I've seen so far assume a power-law thrust variation based on sea-level thrust and air density, but this seems too simplistic.

Of course, powerplant simulation is hugely complex, but it wouldn't make sense for us to have engine models that are more complicated than our aircraft ones. We'd ideally like a simple method to estimate installed thrust and fuel consumption based on Altitude, Mach number and/or airspeed and/or dynamic pressure for a couple of throttle settings, and for particular engine types (either turbojet, turboprop, piston).

Can anyone recommend any textbooks / websites that could help, and where we could get engine data ? Or is that power-law description the best there is?

Thanks,

andy

 

[IRstuff]

It seems odd to me that you're willing to model something that clearly has second effects as a point mass, but want a more complex model for the engine.

From a systems engineering perspective, the engine should not present more complexity, otherwise it would require an aircraft designer to know more about the engine than he really should have to.

TTFN

 

[andyfromaero]

Hi IRstuff,

Thanks for your reply. Sorry for not being clearer... you're right about the thrust only having a secondary effect on the point mass a/c. What I was trying to say was this: we're already working with a very simple aircraft model, so we'd like correspondingly simple engine model.

The aim is to have just enough engine data to calculate a 'sensible' thrust value, so that we can use it in our motion equations. Of course that motion will be influenced by the aircraft mass, hence we'd also like to estimate the fuel consumption rate.

That power-law representation that I mentioned may well be our only option (I can supply further details about this if it'd help). I'd read that the power-law expressions only held for turbofans at high altitude, hence my doubts about it. So I wondered if anyone knew of any alternative representations.

Thanks

andy