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Post by wannabebuilderuk on Mar 31, 2024 20:00:37 GMT -5
Also I copied you john, I left the igniter on during the 2nd 3 minute long run and it's still working so good to know it's gonna last 😂
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Post by racket on Mar 31, 2024 20:53:54 GMT -5
OK , yep a 1ml/rev will be spinning quickly so that shouldn't be causing a problem unless the "electronics" are an issue , the engine is chuffing a bit .
A bit more thinking required
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Post by racket on Mar 31, 2024 20:55:19 GMT -5
You might need a push button on the ignitor to prevent exceeding its duty cycle
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Post by wannabebuilderuk on Apr 1, 2024 4:47:45 GMT -5
OK , yep a 1ml/rev will be spinning quickly so that shouldn't be causing a problem unless the "electronics" are an issue , the engine is chuffing a bit . A bit more thinking required The pwm controller spins the pump at a consistent RPM and even when it's at full Throttle there should be no pulsing from the pwm so don't think it could be that. Perhaps the flame is unstable but considering how well it atomizes that would be a bit odd, shame I can't see inside the combustion chamber easily. As for the accidentally leaving the ignition system on it's good to know it can continuously spark for several minutes without failing unlike previous versions.
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Post by andym on Apr 1, 2024 6:26:36 GMT -5
Wonderful you got it running, did things get any better at higher settings.... nice
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richardm
Senior Member
Joined: June 2022
Posts: 268
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Post by richardm on Apr 1, 2024 7:26:46 GMT -5
You're saying " a lot of soot" Soot is usually related to a too rich combustion. I dont think that fuel pulsations are the cause. I would rather look at the flame tube design. Enough primary and secondary air ? Lack of those could cause a pulsating flame as it goes from lean to rich.
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Post by wannabebuilderuk on Apr 1, 2024 8:18:56 GMT -5
Wonderful you got it running, did things get any better at higher settings.... nice It was pretty much unstable all the way from idle to full throttle, only started going stable when throttling down. Will keep investigating and try to rule out the obvious issues.
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Post by wannabebuilderuk on Apr 1, 2024 8:21:09 GMT -5
You're saying " a lot of soot" Soot is usually related to a too rich combustion. I dont think that fuel pulsations are the cause. I would rather look at the flame tube design. Enough primary and secondary air ? Lack of those could cause a pulsating flame as it goes from lean to rich. All the holes were calculated correctly and the soot is possibly from the failed start attempt on the driveway, I'll clean it all up and do another test to see what could be causing it and maybe add more holes if soot reappears
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richardm
Senior Member
Joined: June 2022
Posts: 268
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Post by richardm on Apr 1, 2024 8:35:25 GMT -5
Yes try more holes I would try in the primary zone first since the soot seems to be located in this area ( near the injector) In any case it easy to weld plug those extra holes if not needed. You saying that combustion seems more stable when throttling down sound to me like not enough air is reaching. As you throttle down you re cutting down the fuel flow with the engine is still spinning faster with results with more air being available to less fuel.. Did the unstable condition reappeared after spooling down to "idle" If so that would confirm this hypothesis.
And about calculations, You probably did em right since its running but so many more factors are involved , turbulence, pressure losses etc ...
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Post by wannabebuilderuk on Apr 1, 2024 10:11:22 GMT -5
Yes try more holes I would try in the primary zone first since the soot seems to be located in this area ( near the injector) In any case it easy to weld plug those extra holes if not needed. You saying that combustion seems more stable when throttling down sound to me like not enough air is reaching. As you throttle down you re cutting down the fuel flow with the engine is still spinning faster with results with more air being available to less fuel.. Did the unstable condition reappeared after spooling down to "idle" If so that would confirm this hypothesis. And about calculations, You probably did em right since its running but so many more factors are involved , turbulence, pressure losses etc ... I'll clean the soot off before the next test (glad I didn't do all the locknuts up lol) and see if it reappears and go from there, easy enough to weld patches on if I add tok many holes. Got a nice 150k views so far from last 2 posts on my insta lol
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Post by racket on Apr 1, 2024 16:24:38 GMT -5
Perhaps your fuel nozzle is the problem if it was running better after spooling back from high powers , with the flametube heated up, any "aberrant" fuel hitting it would be better vapourised .
What sized fuel nozzle and pressure are you running ??
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Post by wannabebuilderuk on Apr 1, 2024 16:56:43 GMT -5
Perhaps your fuel nozzle is the problem if it was running better after spooling back from high powers , with the flametube heated up, any "aberrant" fuel hitting it would be better vapourised . What sized fuel nozzle and pressure are you running ?? 6gph at 600psi although I set the 600 with no chamber pressure so probably running closer to 570 at full throttle. I did see Google results saying blocked/damaged nozzles can cause this "wet soot" which is what I had so I'll check if there's something wrong with it, perhaps it's spraying a jet from one part and the instability is from the jet burning as it hita the flame tube and breaks apart 🤷🏼♂️ For the next run I'll check nozzle/soot production/stutter and if no improvements or obvious causes I'll start adding extra holes in the flametube
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Post by racket on Apr 1, 2024 17:52:03 GMT -5
Don't change the flametube just yet , extra holes generally exacerbate problems .
Wet soot at the top end sorta indicates "reversal" of the fuel spray, you've got plenty of air holes in the FT end cap , more than enough to produce airflow in the right direction
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Post by wannabebuilderuk on Apr 1, 2024 19:43:48 GMT -5
Don't change the flametube just yet , extra holes generally exacerbate problems . Wet soot at the top end sorta indicates "reversal" of the fuel spray, you've got plenty of air holes in the FT end cap , more than enough to produce airflow in the right direction The plot thickens lol. Perhaps it's pulsing as the flame isn't getting anchored to the primary zone, sorta like imagine a candle flickering vertically but inside the flametube. I'll run some tests to confirm it's not surge which is worse case as can actually cause damage vs combustion instability and try to iron out the kinks before moving onto gaining thrust. Gotta sort out the outlet oil leak along with the leak around the pump shaft, I think it doesn't have a seal by default since the gear end is inside the car engine block so doesn't require one. It loses about a shot glass say every 15m so not a massive concern but needs fixing.
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Post by racket on Apr 1, 2024 19:55:46 GMT -5
Yep , my oilpump leaks back out the shaft , I have a drain line back to tank fitted and an oilseal further out on the shaft .
I really can't see it being surge , your comp/turb combo along with scroll A/R are all "right", my TV84 with the 88mm inducer never had surge problems with that size hot end .
All the best with the next test :-)
Cheers John
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