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[1.0.5] Advanced Jet Engine v2.6.1 - Feb 1


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9 hours ago, AK von Bismarck said:

Most of my KAX propellers are slightly too big for the Mk.1 fuselage with AJE, is there any way to fix this?

Thanks

You could remove the scaling in AJE's patches, that's about it.  As per the previous page, stockalike vs realistic AJE isn't really a clean division at the moment.  I've made a bit of progress toward resolving it for jets, but propellers are not really my domain so I haven't touched them.

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1 minute ago, AK von Bismarck said:

would the scaling affect the thrust? would it make it less realistic?

It would not affect thrust (or mass, or anything else except drag, which would be reduced somewhat due to the smaller cross section).  It would be less realistic in the sense that the engines would be smaller than they are in real life.

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8 minutes ago, AK von Bismarck said:

if that is the case how can I use the upscaled engine properly without properly scaled fuselage parts? (i.e. what does everyone else do?)

Thanks

I think most people use Procedural Parts.  I usually don't use propellers at all, but when I do I'll just pick one that isn't scaled (the KAX turboprop isn't, for instance).

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On 1/8/2016 at 3:11 PM, blowfish said:

Sure.  I meant to write up a wiki page, but that'll have to wait.  In the mean time, here's a brief overview of the parameters

  • Area: area of the compressor/fan intake, in m2.  Note that this doesn't include the bypass.  Thrust basically scales by this.  Will be set automatically if dryThrust is set.
  • BPR: Ratio of bypass (fan) area to core area.  Zero for turbojets, generally 0.3-0.6 for low bypass turbofans, and about 3-12 for high bypass fans.  When this is specified it's really a ratio of mass flows, but AJE equates the two for now.
  • CPR: Pressure ratio of compressor (including fan) at design conditions
  • FPR: Pressure ratio of fan at design conditions.  Irrelevant for turbojets.
  • Mdes: Design mach number (i.e. where CPR and FPR are measured)
  • Tdes: Design temperature (kelvins) (i.e. where CPR and FPR are measured)
  • eta_c: Adiabatic efficiency of compressor.  Generally left at default.
  • eta_t: Adiabatic efficiency of turbine.  Generally left at default.
  • eta_n: Adiabatic efficiency of nozzle
  • FHV: How much energy is extracted when fuel is burnt, in joules/kg.  Set automatically if drySFC is set.
  • TIT: Turbine inlet temperature, the maximum temperature that the turbine can take (kelvins).
  • TAB: Max temperature that the afterburner can take.  Set to 0 for no afterburner.  Automatically set if wetThrust is set.
  • exhaustMixer: whether the cure and bypass flows are mixed before the afterburner/nozzle.
  • adjustableNozzle: Whether the nozzle is adjustable and can therefore produce supersonic exhaust.  Note - even if this is false, the nozzle is still sort of counted as adjustable, just that the exit mach is capped at 1.
  • defaultTPR: Default intake TPR to use for static thrust calculations.  Generally 0.95 for subsonic intakes, 0.9 for DSI, and 0.85 for supersonic intakes.
  • maxT3: Maximum temperature that the compressor can take at its outlet.  The engine overheats and explodes when it exceeds this.
  • drySFC: Specific fuel consumption at static conditions with full throttle and no afterburner (kg/kgf-h I think).  This is used to set FHV.
  • dryThrust: Thrust at static conditions with full throttle and no afterburner (kN).  This is used to set Area.
  • wetThrust: Thrust at static conditions with full throttle and afterburner (kN).  This is used to set TAB.

Hope that helps, let me know if you have any questions.

So when you say "will be set automatically if..." and "This is used to set..." what do you mean? Is there a process for testing other than plug in the numbers and check performance in game? Any tips/advice you can offer? Thanks!

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1 minute ago, Svm420 said:

So when you say "will be set automatically if..." and "This is used to set..." what do you mean? Is there a process for testing other than plug in the numbers and check performance in game? Any tips/advice you can offer? Thanks!

If you provide that data, AJE will use it to fit those parameters on the engine.  So if you provide drySFC, then FHV will be set so that it reproduces that SFC at static conditions, if you provide dryThrust then Area will be set to reproduce it, and wetThrust will be used to fit TAB (whatever values are in there already will be overwritten).  Does that make sense?

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Well maybe you can give me some advice. I am trying raise the thrust of an engine. I made a config for the Tumansky R-13-300 with all the numbers needed, but I am getting less thrust than RL and less thrust than I have in the config. To be precise I am getting 33kn dry static max and 53.1kn wet static I am not sure what to do as my numbers seem to be as accurate as any other jet. Would you be able to advise what variable(s) will increase thrust. I just wanted to know what "levers" I could manipulate to try to adjust performance . I am using the unrealeaed dev version of AJE and the corresponding SolverEngine. Thanks!

Spoiler

 

	@MODULE[ModuleEngines*]
	{
		@name = ModuleEnginesAJEJet
		@maxThrust = 63.7
		
		Area = 0.335
		BPR = 0
		CPR = 8.9
		FPR = 0
		Mdes = 0.9
		Tdes = 260
		eta_c = 0.95
		eta_t = 0.98
		eta_n = 0.8
		FHV = 29000000
		TIT = 1278.15
		//TIT = 1150
		TAB = 1750
		exhaustMixer = True
		thrustUpperLimit = 120
		maxT3 = 750
		
		defaultTPR = 0.85
		drySFC = .93
		dryThrust = 39.9
		wetThrust = 63.7
	}

 

 

 

 

 

Edited by Svm420
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@Svm420 I bet it's intake area. I know I had to configure a new intake and eventually used a rescaled goliath instead of a wheesley for the model when making a config for a PW6000 series engine.

Also remove the area line, you've set the dry thrust already.

 

 

 

Edited by m4ti140
articles, or lack thereof
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28 minutes ago, blowfish said:

@Svm420 Does the part info show the correct thrust numbers?  If so, it's probably this: all the calculations are done at a reference temperature of 288.15 K, but the ambient temperature at the KSC is usually a lot hotter.

It does show the correct info in the menu, but does 30 degrees hotter really mean ~20%+ less thrust? If so then I spent way too much time trying to fix and understand something that wasn't broken. :blush: :lol: Thanks again! Also is there anyway to have the TAB displayed in game. I started trying to use the AJEtester.exe, but realized since TAB is set at runtime I have no way of knowing what to set it at.

Edited by Svm420
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7 hours ago, Svm420 said:

It does show the correct info in the menu, but does 30 degrees hotter really mean ~20%+ less thrust? If so then I spent way too much time trying to fix and understand something that wasn't broken. :blush: :lol: Thanks again! Also is there anyway to have the TAB displayed in game. I started trying to use the AJEtester.exe, but realized since TAB is set at runtime I have no way of knowing what to set it at.

The numbers you're getting aren't out of line with what I've seen - particularly during the day (though the KSC is still pretty warm at night too).  Right now there's no way to see the afterburner temperature in flight.  I might add some (optional) more detailed engine info in a future version, but currently it doesn't exist.  And yeah, AJEtester.exe hasn't been updated in ages.

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Hi guys,

I'm trying out the FS1PRE Customizable Electric Propeller Engine and I'm getting a bit confused.

1. The engine appears to be fixed RPM and variable pitch. I think this because in flight the 'Current RPM' value remains constant.

However, electricity consumption varies with throttle. RPM of 600 but 0 throttle = 0.01 ec/s. RPM of 600 but 100% throttle = 4ec/s. Is this correct? If so, can someone explain why?

 

2. In the hangar varying the max RPM, number of blades or blade length does not affect the max thrust. Only adjusting the engine size affects max thrust.

Increasing the number of blades increases surface area which, for a constant RPM, should be capable of producing more thrust than fewer blades. Is this not correct?

Maybe max RPM is engine RPM and not propeller RPM but in either case I'd expect the 'Current RPM' value to fluctuate in flight when I suddenly change the throttle and thus blade pitch.

 

What am I missing?

Thanks

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2 hours ago, OminousPenguin said:

Hi guys,

I'm trying out the FS1PRE Customizable Electric Propeller Engine and I'm getting a bit confused.

1. The engine appears to be fixed RPM and variable pitch. I think this because in flight the 'Current RPM' value remains constant.

However, electricity consumption varies with throttle. RPM of 600 but 0 throttle = 0.01 ec/s. RPM of 600 but 100% throttle = 4ec/s. Is this correct? If so, can someone explain why?

 

2. In the hangar varying the max RPM, number of blades or blade length does not affect the max thrust. Only adjusting the engine size affects max thrust.

Increasing the number of blades increases surface area which, for a constant RPM, should be capable of producing more thrust than fewer blades. Is this not correct?

Maybe max RPM is engine RPM and not propeller RPM but in either case I'd expect the 'Current RPM' value to fluctuate in flight when I suddenly change the throttle and thus blade pitch.

 

What am I missing?

Thanks

I think that you have missed whole thread. That should be asked in Firespitter thread IIRC.

As for No.1) - it should be correct. IIRC earlier version of firespitter mod have work properly regarding RPM and throttle/thrust, not only for electric engines, but for piston engines too. There is two ways how you can control thrust on electric engines. You can have fixed AoA on propeller blades any you vary a thrust trough different RPM. That kind of solution could be good for electric engines that are capable to respond quickly on throttle input, but even that is not so easy on powerful engines where current trough coils is significant, plenty of things to worry about when you want to quickly change current flow. I will quickly go offtopic and end up with wall of text if I need to explain everything in detail why.

Other solution is to have fixed RPM on engine and you change AoA (angle of attack) on blades to achieve different thrust. Let's say you have constant RPM and with zero throttle AoA on blades are near zero - meaning they don't provide thrust and have minimal drag, therefore, minimum amount of EC consumed to maintain engine rotation. On the other hand, when you increase throttle, you increase AoA on blades that now have more drag in lateral motion but provide longitudinal thrust.
More energy is consumed due to lateral drag on blades than it is with zero AoA.

If I still didn't explained that well enough, watch your vacuum cleaner. When you turn it on, and tube hole is in middle of room vacuum cleaner consumes minimal amount of electricity. If you are close to power counter you will notice how much. Now, when you put tube hole close to ground in a way that hole is closed, vacuum cleaner consumes more electricity. Both times RPM is the same on vacuum cleaner engine.

 

As for No.2) Yep, you are correct, more blades should provide more thrust. If they don't it is probably because firespitter parts were become broken trough various KSP releases and Snjo didn't have much time to properly fix that, only plugin is maintained properly for latest releases. RPM on engines should be constant all times on all altitudes, engines were designed for it until critical altitude is reached where simply is not enough oxygen in air for proper combustion. When critical altitude is not reach, lack of oxygen is compensated with more fuel flow to maintain constant RPM.

 

Some of moderators should move both of our posts in proper thread where someone else can provide better answer.

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Propellers are not really my area of expertise, but I'll try to answer these questions

3 hours ago, OminousPenguin said:

Hi guys,

I'm trying out the FS1PRE Customizable Electric Propeller Engine and I'm getting a bit confused.

1. The engine appears to be fixed RPM and variable pitch. I think this because in flight the 'Current RPM' value remains constant.

However, electricity consumption varies with throttle. RPM of 600 but 0 throttle = 0.01 ec/s. RPM of 600 but 100% throttle = 4ec/s. Is this correct? If so, can someone explain why?

At higher blade pitch the power required is higher for the same RPM.  

3 hours ago, OminousPenguin said:

2. In the hangar varying the max RPM, number of blades or blade length does not affect the max thrust. Only adjusting the engine size affects max thrust.

Increasing the number of blades increases surface area which, for a constant RPM, should be capable of producing more thrust than fewer blades. Is this not correct?

Those firespitter parameters have no effect on AJE.  Does engine size actually change max thrust in flight?

3 hours ago, OminousPenguin said:

Maybe max RPM is engine RPM and not propeller RPM but in either case I'd expect the 'Current RPM' value to fluctuate in flight when I suddenly change the throttle and thus blade pitch.

There's no response time currently modeled in for the electric motor, so it will compensate immediately to pitch changes.

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Thanks for your answers guys.

On 20/01/2016 at 4:21 PM, kcs123 said:

That should be asked in Firespitter thread IIRC.

You're absolutely right. Sorry. I'll do that now.

 

On 20/01/2016 at 5:00 PM, blowfish said:

Does engine size actually change max thrust in flight?

Yes.

 

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7 minutes ago, OminousPenguin said:

Thanks for your answers guys.

You're absolutely right. Sorry. I'll do that now.

Yopu are welcome and no need to apology, I'm not exactly sure if engine in question belongs to firespitter or AJE, but it certainly use firespitter features, so you might find better answer in that thread.

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11 hours ago, kcs123 said:

Yopu are welcome and no need to apology, I'm not exactly sure if engine in question belongs to firespitter or AJE, but it certainly use firespitter features, so you might find better answer in that thread.

It's definitely a Firespitter engine.

I posted here in case anyone is curious:

http://forum.kerbalspaceprogram.com/index.php?/topic/22583-firespitter-propeller-plane-and-helicopter-parts-v71-may-5th-for-ksp-10/&do=findComment&comment=2373239

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  • 2 weeks later...

Version 2.6 is now available

  • SolverEngines 1.15
  • Fix node orientation on Merlins
  • Fix CF34 mass
  • Fix negative thrust bug finally: idle throttle set to give tailpipe pressure greater than ambient
    • Fan/compressor work now determined by proportional work rather than proportional pressure ratio
  • Fix duplicate solar panel issue with VSR
  • Remove RF fuel patches for multimode engines - those belong in other mods
  • Mass flow through jets now calculated based on choked turbine (reference: this book)
    • Reduces supersonic thrust growth a lot
  • Overhaul jet animations - should be much more consistent now
  • Minor adjustments to B9 config
Edited by blowfish
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21 minutes ago, blowfish said:

Version 2.6.1 is now available

This fixes an issue that was causing the black screen bug on rotors when they throttled down to zero, as the reaction wheel tried to apply NaN torque.

I tried the fix and yes it did fixed the problem, but when the rotor running the debug is still spamming NullReferenceError. Would you please look into it more? Thank you.

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1 hour ago, damowang2 said:

I tried the fix and yes it did fixed the problem, but when the rotor running the debug is still spamming NullReferenceError. Would you please look into it more? Thank you.

It's a Firespitter issue I can't fix, basically that it doesn't know how to interact with AJE modules (if you look at the logs outside of KSP you will see that it is in fact firespitter that's giving the error).  It's unrelated to the issue fixed in 2.6.1.  I eventually plan to fork the firespitter modules into something more AJE-compatible, but until then, you'll just have to live with it, sorry.

EDIT: I just tested without AJE, and still get the NRE.  You should probably report this in the KAX thread - it's caused by a FSplanePropellerSpinner without a propellerName.  Firespitter's stuff is still not 100% compatible with AJE by any means, but AJE does not cause this NRE.

Edited by blowfish
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blowfish, I've noticed that Isp of jet engines doesn't change anymore, neither with thrust, nor with altitude. Is that intended or have I messed something up by other mods?

And one more thing: isn't thrust control too viscous? I mean engine response to thrust change. It is way much slower than in other flight simulators, so it's hard to control descend rate on final with thrust, but it shouldn't be. Is that right?

Edited by Ser
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36 minutes ago, Ser said:

blowfish, I've noticed that Isp of jet engines doesn't change anymore, neither with thrust, nor with altitude. Is that intended or have I messed something up by other mods?

And one more thing: isn't thrust control too viscous? I mean engine response to thrust change. It is way much slower than in other flight simulators, so it's hard to control descend rate on final with thrust, but it shouldn't be. Is that right?

Isp should change with throttle and speed (it'll change a little with altitude but that's only because of temperature variation).  If that's not happening, then something is probably installed wrong.  Try re-installing AJE and SolverEngines.

As for response rate, it's basically just set right now based on the size (intake area) of the engine.  I have no idea if it's correct ... if you have data on the response rates of real engines I would definitely be interested to see it.  One other thing is that the afterburner should respond nearly instantaneously, whereas now it responds at the same rate as the rest of the engine (there's an open issue for this).

But if AJE is installed incorrectly, then you might want to take a second look after re-installing and make sure that it's still the same.

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