nbatten
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Joined: January 2020
Posts: 21
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Post by nbatten on Mar 8, 2020 8:40:26 GMT -5
Woops....my fault, I went back and yes I forgot the secondary holes in my sketch about the hemispherical base of the "can". Sometimes I confuse myself... Lol
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nbatten
Member
Joined: January 2020
Posts: 21
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Post by nbatten on Mar 8, 2020 9:14:21 GMT -5
Here is a better drawing of my proposed combustor. Any issues you guys see ? Thanks in advance, Nik
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Post by racket on Mar 8, 2020 18:27:45 GMT -5
Hi Nik
The ignitor plug needs to be only just protruding inside the flametube
Cheers John
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nbatten
Member
Joined: January 2020
Posts: 21
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Post by nbatten on Mar 11, 2020 18:36:41 GMT -5
How does one calculate the amount of propane use at full power for an engine ?
Is there a formula or a calculator?
I would guess it would need temp., Humidity, gas vapor pressure, air flow through the combustor, the 15:1 ratio for propane.....
Any formulas or thoughts?
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Post by racket on Mar 11, 2020 18:53:53 GMT -5
Mass flow per second of air = mass flow of fuel per minute ..............eg , 1 lb/sec of air needs 1 lb/minute of fuel, as a rough guide we use have an overall A/F ratio of 60:1 for moderate/safe turb temps
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nbatten
Member
Joined: January 2020
Posts: 21
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Post by nbatten on Mar 11, 2020 19:37:25 GMT -5
So if I have 0.75lbs/sec. mass flow, I need 0.75 lbs/mins of fuel.
A 20lb propane tank would yield approximately 25 mins of run at full power? Is that correct?
Thanks, Nik
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Post by racket on Mar 11, 2020 19:54:41 GMT -5
Yep
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nbatten
Member
Joined: January 2020
Posts: 21
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Post by nbatten on Mar 11, 2020 20:14:48 GMT -5
What is the math formula(s) for figuring the mass air flow based on compressor inducer size ? Or does jetspecs provide that data in the turbo specs section...
Thanks, Nik
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Post by racket on Mar 11, 2020 23:30:06 GMT -5
Hi Nik As a rough guide use a mass flow of ~11 lbs/min/square inch of inducer , your 2.24 inch dia inducer has ~4 sq ins of area , so ~44 lbs/min mas flow or ~0.75 lbs/sec which corresponds reasonably well with the Garrett map . BUT, and its a big but, only if the turb stage can voluntarily swallow that amount , if the turb stage is undersized then the comp will have to flow less, but if its oversized you can flow more but at poorer efficiency which may offset any gains in thrust due to more turb power being required which means a greater pressure drop across the turb stage and less energy downstream for producing thrust . Your 84/60mm turb wheel is a strange size , I think you may be mistaking the 84 Trim for the inducer size, you may find its only a 60 mm inducer with a 55 mm exducer , your 0.82 A/R may restrict flow , the Garrett map www.garrettmotion.com/wp-content/uploads/2018/05/Turbine-Flow-GT30.jpg indicates a Corrected Flow of ~22 lbs/min at a 2:1 PR across the stage , meaning an Actual Flow of only ~35 lbs/min but at poor efficiency close to the surge line , and with a turb effic that maxes out at only 72% , the engine will run but don't expect good output Cheers John
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nbatten
Member
Joined: January 2020
Posts: 21
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Post by nbatten on Mar 12, 2020 8:09:22 GMT -5
John, the turbine is a 51 trim with a turbine inducer of 84mm and exducer of 60mm. 0.82 A/R. The compressor is a 56 trim with an inducer of 57mm and an exducer of 76.2mm. 0.6 A/R
Thanks, Nik
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Post by racket on Mar 12, 2020 18:12:18 GMT -5
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nbatten
Member
Joined: January 2020
Posts: 21
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Post by nbatten on Mar 16, 2020 19:37:26 GMT -5
What is the minimum thickness of 304 stainless steel for construction of the flametube ? and outer canister ?
Thank you, Nik
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Post by racket on Mar 16, 2020 20:57:58 GMT -5
Hi Nik Minimum 0.5 mm stainless for the flametube , though 1.0 mm copes better with localised hot spots . Outer can needs to be a pressure vessel , so depending on the security of welds etc it will vary , the 7" dia air over water fire extinguishers have nice thin stainless cans that will more than cope with the pressure. I used 0.5 mm stainless for the kart flametube and extinguisher for the outer can jetandturbineowners.proboards.com/attachment/download/68Cheers John
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