richardm
Senior Member
Joined: June 2022
Posts: 261
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Post by richardm on Feb 16, 2024 20:56:34 GMT -5
Or maybe multiple nozzles..primary and a secondary kicking in at some preset pressure... Or a duplex nozzle.... stuff to cogitate on
Still pretty amazing how inefficient a turbo based engine can be compared to a real turbine engine
Those PT-6 engines ( Nozzle is from one) yields 620 shaft hp on top of the energy required to drive its compressor and accessories plus a little residual thrust on about 450 pounds an hour at max power
I will eventually be burning some 75 pounds and might not get 110 pounds of thrust...
But we know it and keep going Just for the fun of it.
Hope no climate anxious guy is reading ...
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Post by racket on Feb 16, 2024 22:04:34 GMT -5
If you compare our turbo based engines to the early jet engines like the Ghost with their radial comps , we're not too bad actually , similar pressure ratios and comp efficiencies whilst we can probably run a tad higher temps , at a lower efficiency , we can get ~60 lbs of thrust per pound per second , the Ghost produced 5,000 lbs from 88 lbs/sec or ~57 lbs/lb .
The Goblin produced ~3,000 lbs at a SFC of ~1.23 lbs /lb . whilst your 110 lbs for 75 works out at only 1.46 SFC , less than 20% extra , not bad considering the scale issues .
Our DIY turbo based engines do a pretty good job considering they're not designed for producing thrust :-)
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richardm
Senior Member
Joined: June 2022
Posts: 261
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Post by richardm on Feb 17, 2024 6:38:20 GMT -5
I wrote about adding nozzles yesterday... Can't say were goes my brain when Im asleep but I woke up remembering those old British jets like the " Viper " series. I think they used vaporizer tubes but with some kind of a starting fuel nozzle to heat em up. Do you know anything about that ? I could maybe use that idea since I already have a nozzle based system. Just had a vaporizer of some sort and pump some more fuel in it after its started up. What do you think? You' say that a bigger fuel nozzle is the easiest mod but where do you get a nozzle capable of that much flow...
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Post by racket on Feb 17, 2024 16:49:09 GMT -5
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richardm
Senior Member
Joined: June 2022
Posts: 261
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Post by richardm on Feb 17, 2024 17:57:36 GMT -5
Ok Thanks I Thought I would have to look for something like 10 or 12 GPH as i m now pumping 3.2 gph ( US) at 250 psi
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Post by racket on Feb 17, 2024 20:31:59 GMT -5
Hi Richard
Sq root 250 = 15.8 , sq root 100 (rating pressure) =10 , 15.8/10 = 1.58 more flow , your current 3.2/1.58 = 2.02 GPH nozzle at the usual rated 100 psi , so 3 times gives us a 6GPH nozzle which will eventually flow ~9.5 GPH (6 X 1.58 ) at 250 psi
My bikes 6GPH nozzle at 750, sq root 27.3 , div 10 = 2.73 , 6 X 2.73 = 16.43 GPH flow .
My 88 mm inducer = 6082 sq mms , your 71 mm 3959 , mine was 1.53 times larger area , 16.43 gph/9.5gph = 1.72 times , LOL......I was running it kinda hot and hard :-)
Hope this helps .
Cheers John
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richardm
Senior Member
Joined: June 2022
Posts: 261
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Post by richardm on Feb 18, 2024 5:03:23 GMT -5
Thanks again! You're THE man!
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