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Post by turboron on Jul 12, 2018 19:53:30 GMT -5
John, my version of copy shamelessly is "Grab It and Use It".
Thanks, Ron
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Post by racket on Jul 12, 2018 21:39:31 GMT -5
Hi Ron
Yep , that's it :-) ................no point reinventing the wheel .
Cheers John
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jeffreyguy
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Joined: June 2018
Posts: 51
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Post by jeffreyguy on Jul 15, 2018 18:42:39 GMT -5
Well I decided to go in a slightly different direction and just use the high pressure nozzles, the flame tube is removeable so if I need to change it later I can just take it out and make a new one. I read John's writeup on hole placement in Azwood's thread and used that as a guideline, the primary holes are placed where the fuel mist would theoretically hit the flame tube wall with 30% of the area used for 1/8" cooling holes. I had a chance to us the plasma table at work on the weekend and made a lot of progress. Got to love this thing! I cut all the larger flame tube holes with the plasma to save my drill bits Then I drilled the 90 1/8" cooling holes And some rolling Here's the combustor parts ready to be welded! My round to rectangle transition came out very nicely. I cut short kerf width slots with the plasma to indicate the break lines and I was just going to weld them solid but I'm thinking leave them in for shallow cooling as they're not very much area. These are the slots I'm a fabricator apprentice by trade but I rarely work with thin sheet like this so it was good practice. Plus I've been doing more R&D than fabricating lately so I was looking forward to it
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Post by racket on Jul 16, 2018 4:14:33 GMT -5
Yep , having made both types of "sore thumb" combustors, I think the single spray nozzle with high pressure fueling is probably the "best??" method , theres more work involved getting the fuel pressure up and constructing its controls , but theres no evap tubes to make , or worry about them failing in service and going through the turb wheel , if I ever needed to make another sore thumb , I'd go high pressure spray , the one on my bike worked great once its fuel control was sorted .
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jeffreyguy
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Joined: June 2018
Posts: 51
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Post by jeffreyguy on Jul 16, 2018 22:11:04 GMT -5
I got everything tacked up after work and it's starting to look like something This stainless stuff sure is hard on drill bits I like a nice tight fit I got the flame tube welded up after dinner but I didn't get any pictures which is just as well. My TIG definitely needs some improvement but I'm doing ok considering I only got my machine a few weeks ago. I'm thinking I'll use a 12v hydraulic vane pump of some sort for a high pressure fuel pump. Otherwise direct injection gas engines like the Ford ecoboost use a high pressure pump to pressurize the fuel rail to ~2000 psi. These pumps are driven off a lobe on the camshaft so it probably wouldn't be too hard to put a single lobe cam onto a 12v motor and mate the two together. The plan for oil is to run copper line with compression fittings to the turbo and a 1" stainless tube from the drain straight down into an oil tank below the turbo. That way I hopefully wont need a scavenge pump.
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jeffreyguy
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Joined: June 2018
Posts: 51
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Post by jeffreyguy on Jul 17, 2018 15:19:12 GMT -5
The outer housing is all welded up Some spots are better than others I rotated the housings so everything would line up and the oil would still drain properly Then I realized I have a slight problem. Ill have to make a 1" spacer with another flange
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Post by racket on Jul 17, 2018 16:49:26 GMT -5
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jeffreyguy
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Joined: June 2018
Posts: 51
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Post by jeffreyguy on Jul 17, 2018 16:49:48 GMT -5
Do I still need a propane pre heat with a high pressure fuel nozzle? Maybe I could use a glow plug instead of a spark plug but one less system wouldn't be a bad thing. Im looking for an electric power steering pump to use as a fuel pump. They're cheap at salvage yards, the flow rate is close but maybe a little high. Apparently they vary in pressure though so Ill have to get one and see. Im aiming for at least 1500psi
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Post by Johansson on Jul 17, 2018 16:57:13 GMT -5
Nope, the propane preheat is just to get the evaporator tubes glowing so you´ll do just fine without. You´ll need a proper spark though to light the fuel mist.
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Post by racket on Jul 17, 2018 17:17:23 GMT -5
Hi
For your initial spoolups a propane pilot light in the flametube will give you a positive ignition just in case your sparkplug positioning or spark strength isn't quite right to ignite the kero spray, you can always remove it once you have things sorted.
You only need ~750 psi max for the fuel pressure , this should still provide acceptable atomisation at idle flows/pressures , thats the pressures I eventually ended up with on my bike after some testing at >1,300 psi, not much to be gained at those very high pressures as the flow doesn't change much with big changes in pressure , its a "square root" thing , a 10 GPH nozzle flows 10 GPH at 100 psi , at 500 psi it flows 22.36 GPH , at 1,000 psi 31.62 GPH and at 1,500 psi only 38.73 GPH , at 2,000 psi 44.72 GPH , our flow has only changed from 10 GPH to 44.72 GPH , a bit over 4 times whilst pressure has gone up 20 times , square root 20 is 4.472 , our flow increase .
Cheers John
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jeffreyguy
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Joined: June 2018
Posts: 51
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Post by jeffreyguy on Jul 17, 2018 20:32:32 GMT -5
I've got a PDF writeup on building turbojets around somewhere with the formula on calculating flow rates through these nozzles that's pretty handy. Ill weld in an extra bung where I can stick a propane torch or something to ensure ignition. Should I drill and tap the bottom of the turbine housing for a drain valve? just in case I get some extra fuel in there.
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Post by racket on Jul 17, 2018 21:10:44 GMT -5
A drain won't go astray.
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jeffreyguy
Junior Member
Joined: June 2018
Posts: 51
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Post by jeffreyguy on Jul 18, 2018 19:56:30 GMT -5
I did some grinding on the flame tube and the slip ring and got them to fit nicely before I put the ring in. It fit so tight it was probably air tight before I welded it! I'm starting to get the hang of this TIG thing I plasma cut a pair of 1/2" flanges then welded them together to make a 1" spacer. Not the lightest way to do it but I can weld to it as a motor mount. I surfaced it on the mill so it would seal properly and I have some gaskets on order Its starting to look like an engine! I have to get some shorter bolts though
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Post by racket on Jul 18, 2018 20:41:03 GMT -5
Just be careful about slip joints , the inner wall can expand considerably and "bind" , a rattly fit is probably better
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jeffreyguy
Junior Member
Joined: June 2018
Posts: 51
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Post by jeffreyguy on Jul 18, 2018 20:45:10 GMT -5
The slip joint is nice and loose, I have to pass the whole flame tube assembly through it to install it. It was the ring to outer wall that was a press fif
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