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-   -   High start temperature (https://www.rcuniverse.com/forum/jetcat-turbine-direct-support-151/8504585-high-start-temperature.html)

mun_iz 02-22-2009 10:18 AM
High start temperature
 
Hi,

For the past 3 starts on my P80, I had been experiencing high starting temperatures between 920-933 deg Celcius. I read in the manual that this might be caused by low gas supply during start up, thereby causing the turbine to overheat. I use 35% propane 65%butane gas. I do not use a gas solenoid valve and during start, I connect my gas bottle directly to the gas inlet of the turbine via a manual gas regulator. When starting, I usually turn the knob of the gas regulator slowly until I hear the gas igniting inside the turbine. Then I would usually increase the gas flow by another 1/2-3/4 turn of the regulator knob while the start process progresses. It had always worked fine.

I was wondering if there are other possible reasons for high starting temperatures besides low gas supply. I do not suspect that the bottle of gas that I was using had depleted since I can still hear liquid sloshing around inside the bottle when I shake it.

Any advise would be appreciated.

Thanks.

KC36330 02-22-2009 11:12 AM
RE: High start temperature
 
are you holding the start gas can so you get liquid or gas??

mun_iz 02-22-2009 11:46 AM
RE: High start temperature
 
Hi,

Gas I suppose. I usually leave the gas can standing upright (gas regulator on top) on the ground while I turn the regulator knob with one hand and steady the can with the other.

KC36330 02-22-2009 11:52 AM
RE: High start temperature
 
with a butane/propane mix if it has the clunk in the can (like PowerMax) then you need to hold the can inverted so you get gas.

mun_iz 02-22-2009 12:08 PM
RE: High start temperature
 
I am using Rothenberger multigas 300... I am not sure if it has a clunk... I don't hear any knocking sound when I shake the can except for liquid sloshing...

Will liquified gas entering the turbine cause overheating problems?

Thanks for your replies.

KC36330 02-22-2009 12:15 PM
RE: High start temperature
 
I've never used that brand of start gas but on all the butane/propane mixes I've used you can hear the clunk when shaking the can. feeding liquid to the turbine can give higher start temps, not sure it would be 200 C though but with wind blowing slightly at the tail during starts I've got considerably higher start temps from that.

mun_iz 02-22-2009 08:23 PM
RE: High start temperature
 
Hi,

Thanks for the tip...

I am uncertain if the cause may be due to liquid propane/butane entering the turbine though. The reason I said this is because I had been using the same brand of propane/butane and the same starting up procedure for the last couple of months. I only started to notice increasing start temperatures in the past 2 weeks (last 3 flights)...

My initial suspision was drawn to the amount of propane/butane left in the can which may be causing a drop in gas flow/pressure... however, as I had mentioned when I shake the can, I can still hear a lot of sloshing sounds.

Any other opinions please?

KC36330 02-22-2009 09:04 PM
RE: High start temperature
 
i don't know what the temps are in Singapore but in cold weather you have to constantly shake the can to get proper gas flow from the butane/propane mix, it's one reason i went to 100% propane off board starting on all my turbines.

mun_iz 02-22-2009 09:41 PM
RE: High start temperature
 
Hi,

That's a good tip... thanks... weather in Singapore is always on the hot side.... 32-35 deg Celcius all year round. However, the past couple of weeks had been rainy and cold... maybe I should shake the can on the next outing and report the results.

mr_matt 02-23-2009 04:00 PM
RE: High start temperature
 

ORIGINAL: mun_iz

Hi,

For the past 3 starts on my P80, I had been experiencing high starting temperatures between 920-933 deg Celcius. I read in the manual that this might be caused by low gas supply during start up, thereby causing the turbine to overheat. I use 35% propane 65%butane gas. I do not use a gas solenoid valve and during start, I connect my gas bottle directly to the gas inlet of the turbine via a manual gas regulator. When starting, I usually turn the knob of the gas regulator slowly until I hear the gas igniting inside the turbine. Then I would usually increase the gas flow by another 1/2-3/4 turn of the regulator knob while the start process progresses. It had always worked fine.

I was wondering if there are other possible reasons for high starting temperatures besides low gas supply. I do not suspect that the bottle of gas that I was using had depleted since I can still hear liquid sloshing around inside the bottle when I shake it.

Any advise would be appreciated.

Thanks.

Yes, there are other reasons. how much total time does the turbine have on it?

Also, is there a reason you are not running in accordance with the manual (i.e. with a starting gas valve connected to the ECU)?

Regards,

mun_iz 02-25-2009 07:05 AM
RE: High start temperature
 
Hi,

The total run time on my P80 is 4 hrs 39 mins.

I ever tried using the gas valve for my first few runs. However, I noticed that with the gas valve attached, there is always a "pop" sound when the gas ignites. I found that the ignitions tend to be smoother without the gas valve and using the procedure I had described earlier.

Can you kindly share the other reasons for high starting temperatures?

I will be flying this coming Saturday and will try with another can of gas for starting.

mr_matt 02-25-2009 11:53 AM
RE: High start temperature
 
Hello,

First, let me say that 900 degrees on a P-80 is FINE, if I were you I would not worry about it.

My guess is that the pump might have broken in some since new and is pumping more fuel for a given voltage.

If you want to experiment, you can lower the Uaccel1 and Uaccel2 voltages a bit (maybe 1-2 units at a time) and I am sure your temps will drop.

To change these values, hold the "Limits" key down and then press "+". This will bring up a sub menu to change the 2 voltages. After you change the voltages with the "+/-" keys, press any blue button to save the values and exit.

Let me know how it goes.

Regards,

mun_iz 02-26-2009 06:08 AM
RE: High start temperature
 
Hi Mr Matt,

Thanks for your reply and suggestions. I will try out the suggestions this coming weekend and keep you posted on the outcomes.

mun_iz 03-01-2009 06:33 AM
RE: High start temperature
 
Hi,

Managed to test the P80 today. I reduced both the Uaccel1 and Uaccel2 voltages by 1 decrement step each (from the default factory settings) and used the same bottle of gas and start up procedures. The starting temperature was 860 deg C (as compared to 930deg C earlier). But have a couple of questions to ask:

1) What does the parameter Uaccel2 do to pump operation? I noticed that it is originally at a much higher setting than Uaccel1.

2) Does the decrement in Uaccel 1 and Uaccel2 voltages have any effect on turbine spooling time? Or are these 2 parameters affecting only the starting pump voltages?

Thanks.

mr_matt 03-01-2009 06:54 AM
RE: High start temperature
 
Hello,

These parameters are for open loop control of the turbine during start up. U1 just gets the kerosene lit, and U2 ramps it up to a steady running state.

Once the turbine is started they are not used hence no effect of performance.

Hope that helps,

ricardinho 03-03-2009 07:34 PM
RE: High start temperature
 
i use the green coleman bottles with dreamworks fitting outside the plane. starts right away and is safer then being in the plane.. i am new at turbines and the easier the better..

giumbo 05-02-2009 06:34 PM
RE: High start temperature
 
Hi ricardinho
Today I received two jet joe turbine very beautiful


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