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Post by racket on May 26, 2021 23:22:18 GMT -5
HI Cullen
Just the 8" flametube needs to be "funneled" into the scroll inlet
Cheers John
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Post by turbojet atv on May 27, 2021 5:22:33 GMT -5
Awesome, thank you John!
I’ve seen the exhaust funnel/cone done in both ways so I thought I’d ask the professionals what works best to avoid messing up and having to redo it.
-Cullen.
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Post by racket on May 27, 2021 5:32:40 GMT -5
Hi Cullen
Theres lotsa different ways of configuring the combustor , just look through the various builds to find one that you feel you're able to make , it can be as simple or as complicated as your skill level allows , I've often had to compromise on a design because its the only way I can make it .
Cheers John
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on May 27, 2021 10:46:50 GMT -5
Hi Cullen, For making your transition from 8" Flame Tube to the turbine housing, I would strongly suggest doing it with a manual bender (I tried a couple of ways before that!) jetandturbineowners.proboards.com/post/30456/threadWhen you design your FT and outer can, I would also bare in mind making it easy to remove/modify. Cheers Scott
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Post by turbojet atv on May 27, 2021 18:07:14 GMT -5
Hi Scott, that’s some nice looking work you did on your engine. I’m going to bend a piece of tube to get it to fit the FT & to the turbo. Well that’s the plan at least.
I made the end piece where the injectors go bolt up to the combustion chamber. It’s got 16 bolts that will hold it all together. I figured it would be helpful if I needed to change or clean the injectors.
-Cullen
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on May 29, 2021 4:07:11 GMT -5
Sounds good Cullen! What injectors are you using?
One other thing, the end caps of the combustor need to be very thick. I have ended up with 12mm on turbo end and 6mm on the other end.
Cheers
Scott
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Post by turbojet atv on May 29, 2021 7:10:13 GMT -5
Hi Scott,
I got to measure mine to see how thick they are. I’m not sure off the top of my head. I’m using 10ga stainless steel plate for the end caps, which I think is an 1/8” thick.
The injectors are kind of blurry right now on what exactly to use. My plan is to stage 8 injectors through out the whole throttle range. From idle to full throttle. My FT will have 6 injectors (3 come on at low rpm & 3 come on at mid rpm) & will constantly stay flowing. The last 2 injectors I’m going to up in my charge pipe as back up injectors at full throttle. That way fuel is already atomized when it hits the FT.
Sounds like a good idea since it works on a lot of blown alcoholic cars on drag strips around my area.
-Cullen
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on May 29, 2021 12:07:24 GMT -5
Hi Cullen,
You may want to rethink the end caps. 1/8” will deform very badly. Flat surfaces do not handle pressure well, my old FT had a 6mm end at the turbo and even that bevelled under pressure and stopped sealing well against the turbine housing, which is when I upgraded to 12mm.
As for the injection, adding fuel before the Ft I think is a no-go. It’s very different to adding fuel in the intake of a piston engine!! You could end up with flames and liquid pooling in the gap between FT and casing. The simplest thing to use is stainless oil burner nozzles, you could use between 3 and 6 on an almost mid-radius PCD in the top cap if you want good atomisation, otherwise one big one and high fuel pressure. another alternative is “evaporation tubes”, a forum search will probably show you that arrangement. To control fuel pressure and give you everything from idle to full power, you can either use a manual bypass needle valve (bypasses fuel back to tank, after the pump) or PWM control your fuel pump.
Cheers
Scott
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Post by turbojet atv on May 29, 2021 15:55:41 GMT -5
Thanks Scott for the info,
You mentioning to injector setup makes since now about the ones in the charge pipe. I Guess this ain’t no piston engine kind of animal. Haha. I was looking into the SS oil burner nozzles as a starting point; I planned on 6 in a circle in the middle of the FT.
As for the end cap, I can kinda see how it could “flex” under pressure. Did you use a 12mm end cap for just the turbo side or did you use 12mm on both injector & turbo side?
-Cullen
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Post by racket on May 29, 2021 18:08:17 GMT -5
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Post by turbojet atv on May 31, 2021 7:10:44 GMT -5
Hi John, that’s interesting to hear that I’d only need a single injector for my size engine. I’d assume it’d be a 20ish gph injector? also check out this gem I picked up for my puzzle ibb.co/HN9ncM4ibb.co/SBKc7CTibb.co/VSyPHxhstill learning how to post full size pics but this is a Honeywell air turbine starter off of a JT8D engine. It came with its shut off valve so that’s a plus for me. construction on the combustion chamber has begun as I got every piece I need to build the engine now. -Cullen
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on May 31, 2021 17:14:50 GMT -5
Hi Cullen,
Really looking forward to seeing your build come together!!
I now run a 12mm thick flat “base” on the combustor where it attaches to the turbine and a 6mm thick top, no bevelling issues so far and vastly improved on before.
Obviously the forces will be about 2.5x greater on a 10” version (mine is 6” dia casing). You could funnel the FT and the casing both down to a smaller dia at the turbine end to reduce the issue (I.e. just big enough to cover the turbine studs). A domed top cap would be ideal, but if not a 6mm thick one may do the job. An additional problem for me was that when my top cap bevelled compared to the casing, that expansion put my spark plug in shear(which went through both the casing and Ft wall).
If you want to use a domed top, you can buy them from AliExpress in 250mm, 3mm thick.
Lots of options, just need to think about your design.
Cheers Scott
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Post by racket on May 31, 2021 17:23:14 GMT -5
Hi Cullen Fuel nozzle size will depend on your fuel pressure, more pressure smaller size , but remember flow is at square root of pressure , at 200 psi its only ~40% greater than at 100psi www.imagebam.com/image/1bff15655398193Cheers John
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Post by turbojet atv on May 31, 2021 21:57:24 GMT -5
Hi Scott, I’ll try to see about getting a 12mm end cap for turbo side to hold all the pressure in. Also, just to point out what design I have drawn out on my white board. I’m connecting my turbo through a 90° bend. Going from 8” to 4”. One side is welded directly to the engine, the other side has a pro modified V band clamp. Those clamps hold up to 800psi of pressure so I don’t see them breaking loose.
I’m doing this for packing the engine in my frame. Placing my turbo 90° off of the casing. If I didn’t, my steering stem wouldn’t fit.
I’ve seen someone use a dome top on their go kart; looked very nice, but for packaging I’m going to try a flat 6mm end cap on my injector side.
-Cullen
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Post by pitciblackscotland on Jun 1, 2021 2:23:30 GMT -5
Hi John, that’s interesting to hear that I’d only need a single injector for my size engine. I’d assume it’d be a 20ish gph injector? also check out this gem I picked up for my puzzle ibb.co/HN9ncM4ibb.co/SBKc7CTibb.co/VSyPHxhstill learning how to post full size pics but this is a Honeywell air turbine starter off of a JT8D engine. It came with its shut off valve so that’s a plus for me. construction on the combustion chamber has begun as I got every piece I need to build the engine now. -Cullen This will be a interesting build I'm sure you will machine up a output shaft support to take up side loads I did on my cartridge starter, some photos here not finish yet but may give you a idea. Cheers, Mark.
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