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Post by racket on Dec 5, 2019 18:32:12 GMT -5
Hi Chris
You could simply reduce the number of tubes to 3 and go with the same dimension that I used in the kart , the 10% figure can be a bit "flexible" , if its greater then we can simply reduce the wall holes area a tad .
Cheers John
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BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Dec 6, 2019 7:54:28 GMT -5
Evaporators works fine but the syringes can clog easy, so a good filter is needed. And make the evaptubes thin, mine is a bit thick so the preheat needs to be on for around 20-30sek before i introduce liquid fuel.
I got 3 evaptubes, ID Ø14mm and 150mm long for my 65mm inducer. www.imagebam.com/image/ed5be8582750473
If i build another one i would go for a spray nozzle. No syringes, less fuel lines, no fuel block, less complex FT and so on.
/ T
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ckliever
Member
Joined: November 2019
Posts: 28
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Post by ckliever on Dec 6, 2019 18:53:51 GMT -5
Wow your engine looks great! I see where all the complexity of an evap system comes into play. I guess I’m a glutton for punishment though and I’d still like to give it a shot. I’m curious, were you guys able to do any testing of the evap tubes prior to starting the engine for the first time? If you took the end cap off so that you could monitor the evap tubes there would be no way to circulate any air through the CC, so is there any benefit to testing the tubes? I was thinking that it would at least be nice to know whether the propane preheat system is working and will get the liquid fuel to burn, etc.
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Post by racket on Dec 6, 2019 20:35:13 GMT -5
Hi Chris No testing done with my builds. I guess the easiest way to test is to attempt a spoolup , just add the propane , hear the ignition and get the starter to spin the rotor ,..............wait a few seconds then slowly start feeding in the liquid fuel .........if everything is OK then you'll hear the engine start to accelerate away to idle as more fuel is added . The amount of propane that needs to be fed in to heat the vapourisers can vary from engine to engine but I've always found a half turn of the propane cylinder valve is more than enough . With our micro style engines fitted with annular flametubes and multiple injectors and vapouriser tubes , its not necessary to feed propane to all of them , with my engines even though there are 18 vapouriser tubes I only have 4-5 propane injectors and only to those in the "bottom" half of the engine , every second tube postimg.cc/XBctT1fz ..............as the tubes are only 0.025" wall thickness they heat up almost instantaniously so its possible to start feeding in the fuel as soon as the starter is activated. Cheers John
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ckliever
Member
Joined: November 2019
Posts: 28
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Post by ckliever on Dec 6, 2019 22:53:43 GMT -5
John,
Great insight, thank you. And wow!! That engine is beautiful. I was pondering how I will deploy the propane and that is very helpful to know that I don’t need to be too concerned with striking all the tubes.
Chris
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Post by racket on Dec 7, 2019 1:02:00 GMT -5
Hi Chris
Its probably better/easier not to feed the propane into the tubes, I've heard that it can cause "problems" if the tubes get past red hot and the propane ignites within the tube and actually ruptures the tube because of the sudden "explosion" within the tube , it might be the reason behind the problems Smithy encountered with the GT6041 vapourisers .................so maybe just have an injector that feeds propane externally around the tubes .
Cheers John
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ckliever
Member
Joined: November 2019
Posts: 28
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Post by ckliever on Dec 7, 2019 14:54:41 GMT -5
More good info John! I think that based on your comments I will just have one propane injector enter the FT axially and somewhat offset but still near the centerline so that the injector is positioned between the tubes and can reasonable heat at least two of them. Hopefully that’s good enough to get the liquid fuel burning
Chris
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Post by racket on Dec 7, 2019 17:02:00 GMT -5
Hi Chris
It is only a preheat so doesn't need to be sophisticated, as long as we get some flames around the tubes things will work
Cheers John
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