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Post by aquaticharpy on Apr 1, 2020 22:59:11 GMT -5
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Post by aquaticharpy on Apr 5, 2020 16:14:48 GMT -5
Tommorrow I'm getting all my sheet metal rolled. So, I decided I needed to cut out the exhaust. To do that I had a few questions.
I'm trying to get the most thrust from this design and I feel a good exhaust is a major part.
1: What should the diameter of the exhaust main section be in comparison to exducer outside diameter.
2: How big and how far away should the exhaust cone be from the core of the exducer blades?
3: How long should the exhaust be for maximum thrust?
4: At the end of the exhaust, how big should the nozzle exit be in comparison to the exducer/main exhaust body for as much thrust as I can get?
5:What else could be added to the exhaust to get more thrust.
Thanks
John
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Post by racket on Apr 5, 2020 17:01:43 GMT -5
1 the ID of jetpipe the same diameter as the shroud for the exducer so as to produce a stepless transition
2 diameter of jetnozzle depends on a lot of unkown variables , but start at comp inducer dia and slowly reduce size until design jetpipe temperature is reached , use a 10 degree angle for the nozzle
3 jetpipe can be 1 exducer diameter long , just long enough to fit pressure and temperature pickups, don't make it any more than a few exducer diameters long
4 see 3
5 an afterbrner
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Post by aquaticharpy on Apr 5, 2020 18:05:32 GMT -5
Would 3 exducer diameters long do well? What's the ideal length for the most thrust? A length where the gas can build up and create pressure to get more thrust but not too long so the thrust starts going down.
The diameter of the center of the exducer is around 1 inch. Should the gas directing cone probably be about an inch away from the blades and 2 inches in diameter with a 10 degree angle until it hits a point?
Thanks John
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Post by racket on Apr 5, 2020 19:19:51 GMT -5
Ideal length of jetpipe is that which produces the best thrust outcome , but again , lotsa variables between engines , so can't give an answer, we want the gases exiting the exducer to seamlessly transition into the jetpipe and out through the jet nozzle with the least losses, the micro RC turbine engines use very short jetpipe/nozzles even when running radial turb wheels,though with more efficient NGVs rather than scrolls, we possibly need a bit more length to allow the gases to "even out" before entering the nozzle due to the often messy gas flow exiting the wheel when fitted with a scroll housing, hence my recommendation of between 1 and 3 exducer diameters depending on whether or not flow straighteners are fitted into the jetpipe. Checkout the jetpipe I used on the GT6041 build jetandturbineowners.proboards.com/thread/78/garrett-gt6041-powered-kart?page=8 half way down page
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Post by aquaticharpy on Apr 5, 2020 19:28:40 GMT -5
How large should the exhaust cone be in comparison with the jet pipe.
Thanks John
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Post by racket on Apr 5, 2020 20:00:24 GMT -5
The cone need only be as long as necessary to produce the required exit area
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Post by aquaticharpy on Apr 5, 2020 20:17:54 GMT -5
Should the cone poke out the nozzle? 80% of jet pipe? How long is necessary to produce required exit area. The cone will start at 2in diameter and go to a fine point.
Thanks John
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Post by turboron on Apr 5, 2020 20:26:36 GMT -5
aquaticharpy, the cone is sized by picking an included angle to reduce from the straight section after the turbo exit flange to the exit area. The exit area is determined by trail and error to prevent surging the compressor. Just use a straight section until you have the engine sorted.
Thanks, Ron
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Post by aquaticharpy on Apr 5, 2020 20:39:07 GMT -5
What sort of trial and error? How will I figure out the length, how will I get it 'sorted out'?
Also, is the nozzle part of the jetpipe in terms of length or is it its own independant length. Say the jetpipe is 12inches and the nozzle at the end is 6 inches to get from 4.5 inches to 2.5 inches at 10 degrees. Would I shorten the jetpipe to account for the nozzle?
Thanks John
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Post by racket on Apr 5, 2020 21:33:59 GMT -5
Where did you get your "2 inch" number from ??
Where did you get your "4.5 inch" number from ??
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Post by aquaticharpy on Apr 5, 2020 21:40:06 GMT -5
Inducer and exducer
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Post by aquaticharpy on Apr 5, 2020 21:44:48 GMT -5
Does the nozzle count towards length or not
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Post by racket on Apr 5, 2020 22:55:38 GMT -5
Neither 2" or 4.5" are inducer or exducer ....................answer my questions , I'm giving you one last chance , then I'm out of here and you're on your own !!
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Post by aquaticharpy on Apr 5, 2020 23:03:54 GMT -5
Exducer is 4.8in OD and inducer is 2.8in ID. I was using rough guesses since I wasnt there at the time. The jetpipe is 12 inches at 4.8in diameter and at the end is another 6inches which tapers to 2.8 inches at a 10 degree angle. Sorry for taxing your patience.
Thanks John
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