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Jet engine losing power

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Re: Jet engine losing power

Postby jam007 » Fri Mar 31, 2017 5:15 pm

Interesting.
Just found your data on Viggen and at Mach 0.6 Aeromatic seems to agree very well from 0- 40 000 ft. So it does not seem to be the case that they are underpowered.
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Re: Jet engine losing power

Postby Necolatis » Fri Mar 31, 2017 5:35 pm

Just keep in mind that document is not official values. Its an estimate that those Australian guys did, if you look at their references there is no official ones used, its just stuff from public domain. And just to take an example, the flight envelope is off, certainly alot for an ISA atmosphere with 4 AA missiles, its too fast and its too high. I used to use those values for the engine some years ago, but I switched to AeromatiC++.
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Re: Jet engine losing power

Postby jam007 » Fri Mar 31, 2017 5:57 pm

Ok, thanks
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Re: Jet engine losing power

Postby jam007 » Fri Apr 14, 2017 9:08 am

Necolatis wrote in Fri Mar 31, 2017 5:35 pm:but I switched to AeromatiC++.

Just checked the source code for AeromatiC++ and the engine thrust is a pregenerated table applied to all turbines regardless of bypass ratio...
So there seems to be room for improvement.
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Re: Jet engine losing power

Postby erik » Fri Apr 14, 2017 9:34 am

Not really. See line 652 and further.

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Re: Jet engine losing power

Postby jam007 » Fri Apr 14, 2017 10:12 am

erik wrote in Fri Apr 14, 2017 9:34 am:Not really. See line 652 and further.

Erik

Ah :!: thanks.

Just did a comparison between the F100 data and the Aero data and they agrees well in numbers and general trend except for 0 ft altitude where the trend differs:
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Re: Jet engine losing power

Postby erik » Fri Apr 14, 2017 10:55 am

The AeromatiC++ table takes into account that an idling engine at high speed actually generates drag instead of thrust. That's probably the difference.

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Re: Jet engine losing power

Postby jam007 » Fri Apr 14, 2017 10:59 am

erik wrote in Fri Apr 14, 2017 10:55 am:The AeromatiC++ table takes into account that an idling engine at high speed actually generates drag instead of thrust. That's probably the difference.

Erik

:?
The F100 and AE data is from mil-thrust table.
Last edited by jam007 on Fri Apr 14, 2017 11:02 am, edited 1 time in total.
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Re: Jet engine losing power

Postby erik » Fri Apr 14, 2017 11:01 am

Yes I just realized that, the drag is for an idling engine and hence is a different table.

By the way, if you can come up with a better formula then I'll be glad to update AeromatiC++.

Update: but keep in mind it has to match for the low bypass ratio jets all the way up to the high bypass ratio geared turbofans.

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Re: Jet engine losing power

Postby jam007 » Fri Apr 14, 2017 11:09 am

One of the best things with FG is all the new knowledge you acquire as you explore the different aspects of flight. Creating a better formula than the already existing seems beyond my current understanding of these engines.
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Re: Jet engine losing power

Postby jam007 » Fri Apr 14, 2017 11:58 am

erik wrote in Fri Apr 14, 2017 11:01 am:Update: but keep in mind it has to match for the low bypass ratio jets all the way up to the high bypass ratio geared turbofans.

By the way what do you think of the accuracy of EngineSim?
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