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Problem throttling up

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Problem throttling up

Old 09-02-2007, 11:43 AM
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Default Problem throttling up

Hi Kelly and Kraivuth,
I emailed this to Kelly as well but not sure if it went through so I'll ask here as well.
Went out again tonight to fly the reaction, still having some issues with the 600.
The EGT probe was the cause of my starting problem, thank you Kelly for getting
me a new one.

Tonight I started up the engine, temps were a little on the low side, checked the
probe and it was not in the tail cone far enough, no big deal, probably got bumped
during loading, as you know the reaction offers no protection to the engine.
Started it again and all was good, 55,000 idle, about 425 degrees, 160,000 top at
about 575 degrees. Taxi'd the plane out (grass runway and fairly rough) and went to
throttle up to take off, engine quit and flame shot out the back. Shut everything
down, no big deal, I figured with the bouncing on the ground it probably got a
bubble in the fuel line. Took it back to the pits, refueled just to be sure,
started it up, waited for idle set, then throttled up slowly as I always do after
start, everything was fine, go to taxi out, advance the throttle, same thing, quits
and shoots flame out the back. So, this time I start it up again, everything is
fine, throttle up slowly, no problems. Go back to idle, then throttle up again, I
didn't slam the stick forward, but I pushed it forward as I would on takeoff or
during flight, the engine got to about 88,000rpm and quit the same way. So I
started it again, and have been able to replicate the problem everytime. If I
advance the throttle slowly it's no problem, if I push it up more aggressively it
quits and shoots flame out. I figured it must be an air leak so I checked all of my
connections and there's no leaks anywhere, but since I had unhooked most stuff and
put it all back together I tried one more time, same problem.

I'm at a loss here, any wisdom, words of advice? I probably won't have a chance to
run it again before princeton, (september 13 - 16) but if there's something I should check that will be
easier to check at the shop I'd rather do it here than there.
Thanks
Jeremy
Old 09-04-2007, 12:22 AM
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Default RE: Problem throttling up

Hey Jeremy,

I replied by email shortly after you sent it, but for the benefit of everyone else here's my leading suspicion(s).

This sounds like some sort of fuel atomisation problem. Its really tough to say, but I'd bet its not related to the ECU or any sort of hose routing, fuel pumps etc... If one or more of the injectors is clogged with debris not functioning properly and fuel is somehow pooling in the engine at low throttle, the increased mass flow could pick the fuel up and inject it late in the combustion chamber. That's a pretty wild guess though.... The flame may also be quite irregular is an injector or atomiser tube is not healthy...

If the flame moves external, the differential pressure over the exhaust turbine will be reduced, which then causes the compressor to slow down while the fuel rate is increasing. Before you know it, you've got a chicken and the egg scenario where EGT is rising, RPM is falling, and its going to shut down from one or the other. If fuel isn't pooling, it may just be a really imbalanced flame... If anything its to blame, its likely something inside the turbine core. 1st thing to do is check all your filters to see if you can find any signs debris entering the fuel system.

I have an email off to Thailand looking for their input. I'll let you know when I hear back, or perhaps Kraivuth may weigh in with his comments directly.

Kelly
Old 09-04-2007, 05:28 AM
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Default RE: Problem throttling up

Before we go into the engine core, let's try increasing up the Ramp Up Mid and Ramp Up Hi values by 1 to 3 units. Please let us know if the engine still behave the same way.

Regards,
Kraivuth S.
Old 09-04-2007, 10:40 AM
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Default RE: Problem throttling up

Ok, I'll try that Kraivuth,
Thanks Kelly, I got your email about 10 minutes after I posted here on RCU. The first time this happened (the maiden flight of the Reaction) I figured it was because I had run out of fuel, or at least the UAT was only about half full so I figured I picked up air and that put the turbine out but the pump was still running and when it had a chance to pick up more fuel it put it into a hot engine causing the flame.
When the engine does this, just before the flame shoots out, it makes a gurgling noise, shuts down, and then the flame shoots out and sounds like a blow torch, not like a turbine really anymore. Kelly, if you may remember, the fellow out at Princeton last year with the blue and yellow Reaction had the same problem a couple of times.
As for clean, I suppose there could be something in there, though I did check all filters and all are spotless, the engine, although my shop is dirty (body shop) is wrapped up between flying sessions on the airplane. The very first full run I had with this engine was the maiden flight and although I suspect the flame out was due to running out of fuel, it may have been whatever is causing it right now, I simply don't know. Thinking back though, I've run it 3 times outside of my shop and it's run 100% fine. Maybe while I was taxiing out to fly last time the engine ingested something? It's a grass strip that I was flying off of so I suppose that's a possibility.

Anyway, when I get a chance I'll try changing those ramp values and run it again, see what happens.

Thanks guys.
Jeremy
Old 09-05-2007, 12:55 AM
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Default RE: Problem throttling up

Adding to Kraivuth's advise...

The low 'up' setting applies mainly to the lower 15-20% of the RPM spectrum, depending on where the ramp switch is positioned (usually a hidden variable unless you've got a really old software version). The mid level ramp switch is loosely bounded by the 20-80% portion of the curve, based on where the 2nd ramp switch point is. If you judge your motor to be having trouble at a specific RPM, this info should help you to know what ramping value to adjust in troubleshooting the disgruntled turbine...

The larger the number of an up / down ramp setting, the longer the turbine will take to spool up / down through that RPM spectrum.

Kelly
Old 09-05-2007, 03:20 PM
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Default RE: Problem throttling up

Jeremy,

I'll probably be up in Princeton on Friday and early Saturday. I'll have a look while I'm there if you like. Don’t think I'll be there for Thursday this year due to the work schedule... If could also grab your old faulty thermocouple while I’m there, I’d appreciate it.

Kelly
Old 05-25-2008, 12:14 AM
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Default RE: Problem throttling up

What ever happend with your problem and how did you solve it. I have a friend that has a 600 and he is haveing the exact same problem with the throttle up and it flaming out. If you go slow its fine if you go more than slow it gargles and flames out. Some times it shoots a little flame out sometimes it doesnt. Can you let us know what was your problem and how you solved it... I have artes turbines and he told me one time to shoot air through the fuel tube at about 80 psi to clear possible blockage in the burner tubes....

Thanks

David
Old 07-24-2008, 07:34 PM
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Default RE: Problem throttling up

Hi David, I'm sorry I didn't see this sooner, I don't generally come in here unless I'm having a problem.

Although I'm not totally happy with how we fixed the problem, we did get it fixed. We simply slowed down the throttle ramping a little bit in the ECU. It works 100% fine now though I am a bit bummed that the throttle transition is even slower now than before. To me it was just putting a band-aid on the problem. But, it works reliably and that's more important to me at this point.

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