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Post by racket on Apr 13, 2024 16:47:21 GMT -5
An "afterburner" is possible as long as theres no nozzle on the end of it , you could still end up with thermal choking of a straight tube if its not large enough , this would probably send your comp into surge and/or your turb temps to be excessive
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Post by racket on Apr 13, 2024 5:59:42 GMT -5
Yep , they're the thermocouples I use , very fast response :-)
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Post by racket on Apr 13, 2024 5:57:54 GMT -5
Hi Richard
Yep , shock waves are my current "unknown", just how much compression is there across a shockwave ??
I looked at some numbers for my comp today and with the high inducer tip angle , to reduce incidence to zero between blade and incoming air at the RPM I'm running , the air going in would need to be at ~900 ft/sec and the relative tip velocity is ~M-1.5 , so well into transonic conditions over a large portion of the inducer.
But the throat area of the inducer can't swallow the amount of air that the inducer is biting off at the density available .
So is there an increase in density across the shock that then allows the inducer to swallow what is being bitten off ................I don't know .
LOL.........to answer your question about 5:1 being too great a PR for a single stage comp , nope , some of the tractor pulling guys use 100psi of boost from a single turbo , 7.7:1 PR :-)
Cheers John
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Post by racket on Apr 12, 2024 18:37:48 GMT -5
LOL...........if I had an Amp meter :-(
Its drawing heaps , the starter gets hot to handle very quickly.
I'd sooner the spoolup is as quick as possible , less chance of doing damage from overheating the turb wheel .
I've gotta have a good think on things , theres been so many different tests with different bits added and removed that I'm getting lost.
Running a 5:1 PR should mean a choked NGV , but with a choked point , what happens downstream can't affect things upstream of it, unless what is done downstream removes the choke , I'm getting the feeling that its a fine line between one and the other at the moment .
A challenging scenario :-)
Cheers John
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Post by racket on Apr 12, 2024 15:53:58 GMT -5
Yep , spoolup time , theres ~3 seconds improvement
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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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