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Post by racket on Feb 22, 2018 19:56:10 GMT -5
Yep , Jetspecs will give you twice inducer diameter ,( 3 times for small turbos) this will provide a generously proportioned flametube that shouldn't give you problems even if the fuel and air presentation isn't the best .
LOL, I provided the info for Jetspecs' creator , so I made sure that the guys who always "know better" would have a chance of getting an engine to run when they inevitably skimped on flametube diameter .................we need 3 times inducer area as a minimum for the FT cross section if we want trouble free running , so with your 81 mm inducer a minimum ID for the flametube of 140 mm , it can be made a tad smaller if theres more effort/sophistication put into the fuel/air presentation, I used a 145 mm FT with my 89 mm inducered TV84 when I really needed a 154 mm one , but I needed to fit the FT into the 7" fire extinguisher can I used for the outer can , so I took extra care with the FT design to compensate .
Theres been some pretty small combustors used at times by various guys , but whatever you do , don't think increasing the length will solve the problems caused by a skinny flametube , it simply won't, be generous and save all the hassles.
Because not all turbos are going to be "ideal" for conversion to a gas turbine , the generous combustor will be more "accommodating" , the engine still mightn't run perfectly but it should run which is a lot better than the disappointment of a nonrunner simply because the FT is a tad too skinny, it can be grossly oversized and it'll work , but a tad undersized and theres nothing but problems.
Hope this helps explain things
Cheers
John
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Post by azwood on Feb 23, 2018 17:17:56 GMT -5
Yep , Jetspecs will give you twice inducer diameter ,( 3 times for small turbos) this will provide a generously proportioned flametube that shouldn't give you problems even if the fuel and air presentation isn't the best . LOL, I provided the info for Jetspecs' creator , so I made sure that the guys who always "know better" would have a chance of getting an engine to run when they inevitably skimped on flametube diameter .................we need 3 times inducer area as a minimum for the FT cross section if we want trouble free running , so with your 81 mm inducer a minimum ID for the flametube of 140 mm , it can be made a tad smaller if theres more effort/sophistication put into the fuel/air presentation, I used a 145 mm FT with my 89 mm inducered TV84 when I really needed a 154 mm one , but I needed to fit the FT into the 7" fire extinguisher can I used for the outer can , so I took extra care with the FT design to compensate . Theres been some pretty small combustors used at times by various guys , but whatever you do , don't think increasing the length will solve the problems caused by a skinny flametube , it simply won't, be generous and save all the hassles. Because not all turbos are going to be "ideal" for conversion to a gas turbine , the generous combustor will be more "accommodating" , the engine still mightn't run perfectly but it should run which is a lot better than the disappointment of a nonrunner simply because the FT is a tad too skinny, it can be grossly oversized and it'll work , but a tad undersized and theres nothing but problems. Hope this helps explain things Cheers John Thanks for the tips is there an optimum air gap between the ft and the outer case.also it's telling me ft length should be about 18in I'm assuming that's to the turbo flange. |
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Post by racket on Feb 23, 2018 17:51:27 GMT -5
For your sized turbo/combustor you probably need at least 12mm gap , preferably a tad more , If you use a common ~7" dia fire extinguisher ( air over water type) for the outer can with a 140 mm flametube you'll end up with a nice gap . The 18" length can include the outlet funnel blending the round FT to the rectangular scroll port , as long as the main cylindrical portion of the FT is ~350 mm long , with the main dilution holes positioned right at the bottom of the section, it should be OK , we "lose" a bit of length at the top end because of spray angles etc , and its ideal if the length/diameter ratio is ~1.5:1 when using a single spray nozzle, so you'll need ~190 mm just for the Primary Zone , then maybe another 100 mm for the Secondary, so up to ~290mm before getting to the main dilution holes . Its more of a length/diameter sorta thing , even with my micro annular flametubes , they might be only 110 mm long , but the cross section is only ~50 mm , ..................we need 18 fuel delivery positions to adequately cover the annulus , its sorta like having 18 small flametubes "segments" in a single ring .http://jetandturbineowners.proboards.com/attachment/download/25 With my GT6041 build the 6 evaporators produced 6 "segments" which allowed the main body of the FT to be relatively short jetandturbineowners.proboards.com/attachment/download/177 Cheers John |
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Post by azwood on Feb 23, 2018 18:46:20 GMT -5
For your sized turbo/combustor you probably need at least 12mm gap , preferably a tad more , If you use a common ~7" dia fire extinguisher ( air over water type) for the outer can with a 140 mm flametube you'll end up with a nice gap . The 18" length can include the outlet funnel blending the round FT to the rectangular scroll port , as long as the main cylindrical portion of the FT is ~350 mm long , with the main dilution holes positioned right at the bottom of the section, it should be OK , we "lose" a bit of length at the top end because of spray angles etc , and its ideal if the length/diameter ratio is ~1.5:1 when using a single spray nozzle, so you'll need ~190 mm just for the Primary Zone , then maybe another 100 mm for the Secondary, so up to ~290mm before getting to the main dilution holes . Its more of a length/diameter sorta thing , even with my micro annular flametubes , they might be only 110 mm long , but the cross section is only ~50 mm , ..................we need 18 fuel delivery positions to adequately cover the annulus , its sorta like having 18 small flametubes "segments" in a single ring .http://jetandturbineowners.proboards.com/attachment/download/25 With my GT6041 build the 6 evaporators produced 6 "segments" which allowed the main body of the FT to be relatively short jetandturbineowners.proboards.com/attachment/download/177 Cheers John That's great info I thought a decent air gap would help sorta like a plenum chamber on a engine so now I have a idear if what it need I can start building |
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Post by racket on Feb 23, 2018 20:29:08 GMT -5
Its important to have some sort of diffusing funnel where the delivery tube from the comp joins the outer can so as to increase the flow area into the gap between FT and can
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Post by azwood on Feb 24, 2018 20:28:11 GMT -5
Its important to have some sort of diffusing funnel where the delivery tube from the comp joins the outer can so as to increase the flow area into the gap between FT and can That was something I was thinking about too when I make plenum chamber's for cars you need even flow across all runners I guess the ft holes are the same what about adding an intercooler to it aswell |
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Post by racket on Feb 24, 2018 21:20:55 GMT -5
Nope , intercoolers are only of any use between compressor stages , an intercooler between comp and combustor will reduce your air pressure entering the combustor and add to the loses, the drop in temperature will mean you'll need to burn more fuel to reach your turb stages max temp , again thats a "loss" in SFC .
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Post by azwood on Feb 25, 2018 2:54:32 GMT -5
That's interesting thanks I'm on the hunt for the flame tube pipe and the outer case atm I'll post some pics as I build
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Post by azwood on Feb 28, 2018 19:58:29 GMT -5
That's interesting thanks I'm on the hunt for the flame tube pipe and the outer case atm I'll post some pics as I build So I now have the flame tube 150mm I'd all I could get and a outer case too just been working on a good design to reduce it to the turbo flange I want it to flow nice as possible |
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Post by azwood on Feb 28, 2018 20:01:31 GMT -5
Hope the fact that it's a twin scroll isent to much of a problem but it's a nice 128 ar
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Post by racket on Feb 28, 2018 22:27:25 GMT -5
Theres been plenty of twin scroll engines built , theres extra losses within the scroll from all the extra wall area friction .
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Post by azwood on Mar 1, 2018 2:23:28 GMT -5
Theres been plenty of twin scroll engines built , theres extra losses within the scroll from all the extra wall area friction . As long as I can put it in a bike and it moves under it's owne power I'm happy not looking to break any land speed records I have sport bikes for that stuff.does anyone have a pic of a good flame tube shape I was thinking a round top might work well and a nice taper into the turbo housing |
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Post by azwood on Mar 1, 2018 2:49:15 GMT -5
Something like this shape  |
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Post by racket on Mar 1, 2018 3:10:10 GMT -5
Yep :-)
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Post by azwood on Mar 1, 2018 3:26:40 GMT -5
Do you have any YouTube vids of the bike is love to see it |
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