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SWS-AlexVletsas avatar image
SWS-AlexVletsas asked SWS-AlexVletsas answered

ITT simulation

Can we have the formula that is used to calculate a turbine's ITT?

The five parametres provided currently are:

  • itt_peak_temperature
  • itt_tc
  • itt_tuning_constant
  • fuel_flow_max_itt_factor
  • fuel_flow_min_itt_factor

The only ones that seem to have a somewhat clear function are itt_tc and itt_tuning constant. However, after running tests with t least 60 different combinations, I was unable to get the ITT tuned to their RL parametres. When plotting the charts for my results, it looks as if the ITT follows specific ratios for low idle, high idle and max power, with itt_peak_temperature just scaling those higher or lower.

fuel_flow_max/min_itt_factor seemed to be what I need to fine- tune my ITT readouts, but they don't seem to have an effect.

aircraftflightmodel
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SonantAlpaca avatar image
SonantAlpaca answered

Hello,

We're currently upgrading the documentation on ITT so here's some details that I can give, even though it's not live yet:

screenshotitt.png

Hope the screenshot is clear enough for you to read, the formulas are a bit small...

And I also hope it helps!


screenshotitt.png (219.5 KiB)
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FlyingsCool avatar image
FlyingsCool answered

I don't know anything about Turboprops, but, is fuel flow max and min really the same for all Turboprops? Are those variables eventually going to get exposed and be modifiable? Can authors work around that?

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Krazycolin avatar image
Krazycolin answered

No... they aren't the same for each type of engine...

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SWS-AlexVletsas avatar image
SWS-AlexVletsas answered

SonantAlpaca I would like to add a suggestion: expose the FuelFlowITTMax and FuelFlowITTMin parameters for turboprops. The current range of temperatures is fixed and leads to unrealistic ITT temperatures, unless the engine's max fuel flow is artificially lowered to an unrealistic level.

For example, some reference values from the Kodiak (Sea level, ICAO standard day):

State
ITT real
ITT sim (settings #1)
ITT sim (settings #2)
Minimum operational ITT
400
Below limit
OK
Low idle, feathered prop
470
465
585
Low idle, unfeathered prop
420
332
410
High idle
470
442
530
Climb max
790
794
912

You can also watch an engine startup of this aircraft (PT6 engine) in this video at 21 seconds: Kodiak startup video

Below you can see a chart that shows the distribution of ITT for different settings in the engines.cfg file. As you can observe, the spread between minimum and maximum values is specific and we cannot raise the bottom of the threshold without increasing the top temperatures.

1634205526858.png

I could also suggest a StarterPeakITTFactor parameter that will set the Peak ITT the engine can achieve during startup. You will notice in videos (Kodiak) that the PT6-34 will be at 420oC low idle, but during startup it can reach 600-700 before settling. It won't get us into hot starts,


1634205526858.png (11.8 KiB)
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