Turbine quits at idle
11-20-2012, 04:24 PM
#26
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RE: Turbine quits at idle
Just for giggles... after it ignites... turn the propane up one more "Click". I know my AMT likes a small amount of gas to light-off... but then needs a bunch of pressure to come up to speed.
Also... if your temp is higher than normal... you could have an air leak around the diffuser and the engine can.
But... I'm guessing there can be a pump issue too.
Also... if your temp is higher than normal... you could have an air leak around the diffuser and the engine can.
But... I'm guessing there can be a pump issue too.
11-20-2012, 04:46 PM
#27
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RE: Turbine quits at idle
First off, I want to qualify my comments. I do not have a turbine powered RC aircraft, and have only rudimentary experience with small turbines. However, I've been commissioning gas turbines for over 10 years now for large power plants and aircraft (the kind you ride in), and for the most part, a gas turbine is a gas turbine no matter what size it is.
If I were troubleshooting this engine the first thing I would do is confirm your instrumentation is correct. IF it is hunting, you can hear it (I tune mostly by ear these days anyway- you kind of get a knack for it after a while). As I understand it, you only have an RPM sensor and a T6 sensor (EGT), so confirming they are in good shape should be fairly easy. Check cables for freyed wiring and/or loose connections. As I understand it, these engines do not have a fuel return loop in them, which is fine, but makes tuning much more tricky if your intrumentation isn't accurate than a closed loop system.
Assuming the instrumentation is correct, next is the fuel. I saw an interesting video recently of a guy rebuilding his small RC turbine after 25 hours. He found that about 30% of his fuel system was clogged and he never knew it. After cleaning, the engine ran at higher RPM and at better temperatures (these engines run incredibly cool compared to industrial and avaiation engines, but that's understandable since internal cooling is minimal at best). Anyway, since you can't just pull an injector and check it, I would take the enine out and remove the fuel tubes for inspection. Put some butane or propane on the input side and lite the tubes. If they don't all burn evenly and robustly, you've got to clean them. Uneven combustion causes all sorts of problems, even in giant 500MW frame engines- idle hunting being very common in this case.
Anyway, I hope you get it sorted out. Remember that fuel maps inside these FADEC systems work on steps and ramp curves, and when you see hunting, that means the ECU has commanded a ramp and expects to see a certain RPM at the end of the cycle. If the RPM isn't there, it will loop the ramp cycle again from the step below. If it doesn't make the ramp smoothly, I normally decrease fuel (believe it or not) so that the computer expects the next step to come in at a lower RPM. It sort of tricks it into a correct ramp. I don't know how much control you have over the fuel mapping, but if you do have control, try lowering the fuel value for the Idle setpoint and see if it smooths it out. It might run a little hotter at first, but the computer should be able to sort that out on its own. Anyway, my 2 cents. Good luck!!
If I were troubleshooting this engine the first thing I would do is confirm your instrumentation is correct. IF it is hunting, you can hear it (I tune mostly by ear these days anyway- you kind of get a knack for it after a while). As I understand it, you only have an RPM sensor and a T6 sensor (EGT), so confirming they are in good shape should be fairly easy. Check cables for freyed wiring and/or loose connections. As I understand it, these engines do not have a fuel return loop in them, which is fine, but makes tuning much more tricky if your intrumentation isn't accurate than a closed loop system.
Assuming the instrumentation is correct, next is the fuel. I saw an interesting video recently of a guy rebuilding his small RC turbine after 25 hours. He found that about 30% of his fuel system was clogged and he never knew it. After cleaning, the engine ran at higher RPM and at better temperatures (these engines run incredibly cool compared to industrial and avaiation engines, but that's understandable since internal cooling is minimal at best). Anyway, since you can't just pull an injector and check it, I would take the enine out and remove the fuel tubes for inspection. Put some butane or propane on the input side and lite the tubes. If they don't all burn evenly and robustly, you've got to clean them. Uneven combustion causes all sorts of problems, even in giant 500MW frame engines- idle hunting being very common in this case.
Anyway, I hope you get it sorted out. Remember that fuel maps inside these FADEC systems work on steps and ramp curves, and when you see hunting, that means the ECU has commanded a ramp and expects to see a certain RPM at the end of the cycle. If the RPM isn't there, it will loop the ramp cycle again from the step below. If it doesn't make the ramp smoothly, I normally decrease fuel (believe it or not) so that the computer expects the next step to come in at a lower RPM. It sort of tricks it into a correct ramp. I don't know how much control you have over the fuel mapping, but if you do have control, try lowering the fuel value for the Idle setpoint and see if it smooths it out. It might run a little hotter at first, but the computer should be able to sort that out on its own. Anyway, my 2 cents. Good luck!!
11-21-2012, 03:33 AM
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RE: Turbine quits at idle
C131: Those are all good points... but most guys don't like to get into these engines. (They may let the magic out. LOL) Also... if they are under warranty... that will void it. But... it's a good point about the fuel needles being clogged. Reflecting on that... when they start to clog... you will see a rise in the fuel pump voltage. Also... when it lights off... if you look into the tail cone... you shoudl see an even flame "Glow". When they start to plug up... it will be hotter in one spot.
Also... these ECU's are smart but simple. They don't really have a "Table" for fuel vs Temp vs RPM to make them run. They basically have a few settings to know how fast to ramp the fuel, to start, accell, and decel, and they just watch the RPM and temp to make sure they aren't going over, or under the settings. So... if it takes 100% pump pressure to get to full RPM, and it's not over temping... that's what it will try to do. (unless you set a max fuel pump voltage) Basically, they learn the needed voltages, each time you start it.
CarsII: Something else to check, is the temp probe. Make sure it hasn't moved in the tail cone. (should be in about 3mm)
I know hindsight is 20/20... but this is the reason to log the fuel PW at full and idle when it's running properly. (Then you have a positive baseline when there are problems) The nice thing about my old AMT is that it locks in the high and low pump voltages, so I can see it after or before the flight. All my Xicoy ECU's just give me the current pump PW. (like yours)
Anyway... let us know what happens.
Oh... just to keep things clear... Are you having an actual "Flame-out" at idle... or is it just not starting properly?
Also... these ECU's are smart but simple. They don't really have a "Table" for fuel vs Temp vs RPM to make them run. They basically have a few settings to know how fast to ramp the fuel, to start, accell, and decel, and they just watch the RPM and temp to make sure they aren't going over, or under the settings. So... if it takes 100% pump pressure to get to full RPM, and it's not over temping... that's what it will try to do. (unless you set a max fuel pump voltage) Basically, they learn the needed voltages, each time you start it.
CarsII: Something else to check, is the temp probe. Make sure it hasn't moved in the tail cone. (should be in about 3mm)
I know hindsight is 20/20... but this is the reason to log the fuel PW at full and idle when it's running properly. (Then you have a positive baseline when there are problems) The nice thing about my old AMT is that it locks in the high and low pump voltages, so I can see it after or before the flight. All my Xicoy ECU's just give me the current pump PW. (like yours)
Anyway... let us know what happens.
Oh... just to keep things clear... Are you having an actual "Flame-out" at idle... or is it just not starting properly?
11-21-2012, 09:04 AM
#33
RE: Turbine quits at idle
At this point it looks like the pump just stops flat out, when it quits I see no white smoke ( unburned Kero ) as when it quits when it get air bubbles, I know that when it gets air and quits the pump keeps running for a second or two till the FEDEC sences the decrease in RPMs, it pumps fuel into the engine and then the Kero gets burned like smoke, hence the white smoke.
To answer your question, it flames out at idel only, everything after is normal.
I will post a video of a complete run today and will keep a very close eye on the pump.
To answer your question, it flames out at idel only, everything after is normal.
I will post a video of a complete run today and will keep a very close eye on the pump.
11-21-2012, 12:28 PM
#34
RE: Turbine quits at idle
Here is my last run, this will help with any questions, you will hear changes on the rpms I did not touch the throttle stick at all it did it all by itself, and I'm adding a picture of after it stopped.
As it was running I had my fingers touching the pump, it was running fine, it stopped right away matching the HDT info.
Sorry, up loaded the wrong one, it will be another 20 min before it is ready.
As it was running I had my fingers touching the pump, it was running fine, it stopped right away matching the HDT info.
Sorry, up loaded the wrong one, it will be another 20 min before it is ready.
11-21-2012, 12:46 PM
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RE: Turbine quits at idle
CARLOS!!! What's up brother!! Sold the Harley and getting back into turbines!! NIIIIIICE!. Yes still into flying!. Getting the boy started flying. Im in West Sac. About 10 minutes from WDA. Hope all is well. And get that Boomer in the air.
11-21-2012, 12:49 PM
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RE: Turbine quits at idle
Lol, I just used a fridge magnet (it had a Cow attached it with dangley legs but the rpm sensor didnt seem to object, I waved it in a circular motion ) .... Are you using a fadec with a magnetic pick up like the wrens?
I thought it was a long shot when the wren engineer told me to try it, but it worked! You have nothing to loose eh? It is probably the pump sticking to be honest but if it works happy days !
Scott.
I thought it was a long shot when the wren engineer told me to try it, but it worked! You have nothing to loose eh? It is probably the pump sticking to be honest but if it works happy days !
Scott.
11-21-2012, 01:11 PM
#39
RE: Turbine quits at idle
Last video, forth.
On this run I increase the propane by one clik right after the propane kicked on, it is spending less time at 23-24k trying to ramp up.
http://www.youtube.com/watch?v=UUZurvGRZdQ
On this run I increase the propane by one clik right after the propane kicked on, it is spending less time at 23-24k trying to ramp up.
http://www.youtube.com/watch?v=UUZurvGRZdQ
11-21-2012, 01:20 PM
#41
RE: Turbine quits at idle
Mario
Mama is going to get upset if you get back to your old tricks ( we do know how to desappear money quickly ) but that's ok, I would like to see you fly the jets at the field again.
See you soon, I may be in Sac on Saturday.
Mama is going to get upset if you get back to your old tricks ( we do know how to desappear money quickly
) but that's ok, I would like to see you fly the jets at the field again.See you soon, I may be in Sac on Saturday.
,......... I only have one ( from the fridege also ) that is attached to a SF street car, I guest it will have to do
11-21-2012, 03:26 PM
#44
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RE: Turbine quits at idle
Listening to the vid... it sounds faster than it's reporting. I'd go after the pick up with a magnet. Also... just make sure it's in the right place. My buddy got a PST600 cheap, and we found the pickup out of place. Ran fine once we moved it back.
11-21-2012, 06:57 PM
#48
RE: Turbine quits at idle
Just thought I would mention this. I know it's not a Jet Cat, but my Jet Cats have the temp set at 21ºC and not 16ºC. I noticed this in one of your videos, your temp was set at 16ºC before you started it. Maybe it's not reading the temp as soon as it should and the ECU is shutting it down.....Larry