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Post by racket on Apr 11, 2024 19:42:45 GMT -5
Hi Guys
This spoolup fueling issue has me baffled , but I want to throw this out to anyone that might know more about electrics than this dinosaur .
The test the other day produced a very fast spoolup , so I went back and looked at old videos of the spoolup when I first fitted this stronger starter and found it took a few seconds longer with the brand new starter .
Now to reduce spoolup speed there needs to be more power supplied by the starter which would mean sucking juice from the batteries at a greater rate .............perhaps to such a rate that the fuel pump was being starved of power .
Is it possible that the new brushes in the starter have worn in and are able to transfer more power ??
Cheers John
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Post by racket on Apr 11, 2024 19:28:06 GMT -5
Hi Stephan
Thanks for that , yep , its a bad matching of parts ................I certainly wouldn't be fitting a jetnozzle on it until I'd explored higher P2s with an open pipe , if its temps are reasonable then maybe a slight reduction at the nozzle , but I doubt it'll accept much backpressure before temp get excessive :-(
Cheers John
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Post by racket on Apr 11, 2024 16:17:28 GMT -5
Hi
Could you please provide your comp and turb wheel dimensions please ..............it could be contributing to your heat problems if I read your comments correctly about the "hole in" is bigger than the "hole out " of the turbo rotor
Cheers John
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Post by racket on Apr 10, 2024 17:53:03 GMT -5
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Post by racket on Apr 10, 2024 16:29:24 GMT -5
With your jetpipe and nozzle , the jetpipe needs to ideally have an ID the same size as the scroll casting bore for the turbine wheel exducer so that theres a smooth transition , a tad larger is OK if it means a ready made size tubing .
As for the jet nozzle size , this is where things get difficult to "calculate" , it needs to be small enough to fully expand the gases , but not so small as to increase jetpipe gas temps past ~1200deg F- 650 C , or a dull red on the wheel .
You could start with a nozzle dia similar to your compressor wheel's inducer diameter to be on the safe side , actual required size will depend on a number of engine component variables, efficiencies etc etc , trial and error is the only way unless you have both compressor and turbine Maps for your turbo , if you do then it is possible to calculate a ballpark size , but the final sizing needs to be done on the running engine performance numbers .
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Post by racket on Apr 10, 2024 16:15:01 GMT -5
With turbine engines its difficult to find simple explanations because the subject isn't simple unfortunately :-(
I'll have a look through my stuff to see if I can find another Paper worth reading
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Post by racket on Apr 10, 2024 4:42:08 GMT -5
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Post by racket on Apr 10, 2024 4:23:08 GMT -5
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Post by racket on Apr 10, 2024 4:08:11 GMT -5
Theres always the GTBA www.gtba.co.uk/ the original home of RC micro turbine evolution since the mid 1990's, the amount of info is staggering . If you need more specific info , please ask away :-) Cheers John
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Post by racket on Apr 10, 2024 4:04:57 GMT -5
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Post by racket on Apr 10, 2024 2:59:42 GMT -5
Hi Guys
Completed a test this afternoon .............nice 11 second spoolup , like old times :-)
On only 12V the fuel pump didn't supply enough to get to 4 Bar P2 , but thrust still ~220 lbs , the airflow was being restricted , lots of "chuffing" from the comp and more surge slot pressure .
I'll collect numbers off the videos tomorrow
Cheers John
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Post by racket on Apr 9, 2024 20:58:21 GMT -5
Is it going to be RC micro turbine engine or a turbocharger based engine .
Do a search for .....
Design and analysis of an annular combustion chamber for a micro turbojet engine PDF Zenodo
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Post by racket on Apr 9, 2024 19:19:00 GMT -5
Hi Stephan
4" flametube with propane , maybe ..............certainly not with liquid fuel .
Cheers John
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Post by racket on Apr 9, 2024 15:48:43 GMT -5
8 PSI is a healthy and safe idling speed , as long as the turbine wheel doesn't colour, its safe to take it up to higher rpm , try for 15 psi and then 20 psi , but don't go higher without more instrumentation
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Post by racket on Apr 9, 2024 1:24:12 GMT -5
Hi Andy
One of those days :-(
LOL.............got all the gremlins showing their faces .............next track day all will go smoothly :-)
Cheers John
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