BFTO
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Joined: February 2016
Posts: 128
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Post by BFTO on Nov 7, 2017 16:05:55 GMT -5
Beautiful bit of stainless work :-) Have you calibrated the A/B nozzle size , from the pics it looks a bit small in diameter ?? Also the support brace ...............is there allowance for axial expansion in the mounting holes?? Cheers John Hi John! I made the nozzle 65mm, easy to cut a bit off if needed. Is it way to small? The support brace have allowance for 15mm expansion of the AB.
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Post by racket on Nov 7, 2017 16:37:36 GMT -5
Hi
All good with the expansion :-)
The problem with an A/B nozzle thats too small is that it'll cause too much backpressure on the gas producer which will elevate your turb temps at the least and surge at the worst .
Ideally its best to get the engine sorted using a plain jet nozzle and once the nozzle size is optimised , then simply calculate the theoretical A/B sizing , basically we double the plain nozzle area , then divide by 1.4 .................this is because the gas density has halved , but gas velocity has only increased by ~40%.
Your current A/B's 65 mm dia = 3318 sq mms X 1.4 = 4645, div by 2 = 2323 sq mms = 55 mm dia for a plain nozzle , probably a 57 mm used to allow for boundary losses.
If a 57 mm dia nozzle produced the design TOT at full rpm then its "optimised" .
Cheers John
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CH3NO2
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Joined: March 2017
Posts: 455
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Post by CH3NO2 on Nov 7, 2017 19:29:21 GMT -5
Excellent. Can't wait to see this one light up.
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BFTO
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Posts: 128
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Post by BFTO on Dec 4, 2017 3:04:10 GMT -5
We spent couple of hours this weekend to redo the fuel system and added a bypass valve. Flow tested the syringes with sucsess at different pressures. BUT when we tried to fire her up, she refused to keep the propane flame alive even with the lowest setting on the leaf blower. Nothing has changed since last time except it was -8deg C and the propane bottle is 40% full She has been a little bit moody before but not like this. My teori is the primary holes needs to be moved/rearrange to make a quite place at the top. Any other idés?
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Post by racket on Dec 4, 2017 3:16:13 GMT -5
At minus 8 C the vapour pressure in the propane cylinder will be getting pretty low
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BFTO
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Posts: 128
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Post by BFTO on Dec 4, 2017 3:27:01 GMT -5
At minus 8 C the vapour pressure in the propane cylinder will be getting pretty low Yea, we thought about that but at -8c it should have a couple of bars pressure? maybe time to get a pressure gauge. Next try we talked about heating the bottle with hot water, but I think the big problem is the primary holes.
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Post by racket on Dec 4, 2017 3:31:03 GMT -5
Yep ,a fuel pressure gauge is a must have item
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CH3NO2
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Posts: 455
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Post by CH3NO2 on Dec 4, 2017 7:33:49 GMT -5
It looks like your vapor pressure may be in the 10psi - 20psi range. After dropping 20%-50% in the plumbing system, there wont be much pressure left to run the engine. The best case scenario is 16psi vapor pressure delivered to the flame can. This is great news because it means you dont have to mess with the primary holes. Not yet anyways. e
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BFTO
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Posts: 128
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Post by BFTO on Dec 4, 2017 8:21:29 GMT -5
It looks like your vapor pressure may be in the 10psi - 20psi range. After dropping 20%-50% in the plumbing system, there wont be much pressure left to run the engine. The best case scenario is 16psi vapor pressure delivered to the flame can. This is great news because it means you dont have to mess with the primary holes. Not yet anyways. e Will try to heat up the bottle before next start, we have 95% propane. Should be ~2,5bar @ -10degC. If that doesnt work, we will use the angle grinder and the weld to redo the primary holes. www.flogas.se/sites/default/files/propan_95_engelska.pdfWe extinguished the flame even before the leaf blower was against the bellmouth, we tried maybe 15-20times to start without success. We tried to crank the propane way up and it got very hot and she was spitting a blue flame out of the turbine. But as soon I cranked the leaf blower to full the flame was extinguished. I can understand that the flow of propane would be a problem if we did a P2 of 0,5bar, but the propane is only to start the engine and heat up the evaporators. Now the needle didnt even rise above 0,0bar. Love R/D
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BFTO
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Post by BFTO on Dec 10, 2017 7:10:24 GMT -5
After a few trys the engine roared to life yesterday, didnt make any big changes from last week.
The fuel system worked smoothly and easy to throttle! she was moving some air at 1bar!. I can hear she has alot left to give but we take it slowly. Have a handheld IR tachometer but its useless, cant read the RPMs right. Any ideas what kind of P2 is our max RPM?
The numbers:
Without nozzle: P2 1bar, TOT 375deg C, fuel flow ~400ml/min.
AB attached with 65mm nozzle: P2 1bar, TOT 495deg C, fuel flow ~400ml/min.
Next thing to improve is the ignition system, up till now we have used a blowtorch to ignite the propane. Any ideas how we can build ignition system with a big spark? have tried a ignition coil from a car and some relays but the spark is far from good and was not reliable.
Have alot of photos and videos of yesterdays runs, will upload that later this week.
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Post by racket on Dec 10, 2017 14:51:02 GMT -5
Nice cool temperatures .
P2 vs max rpm can be hard to predict , it depends where on the map you are flowing , along with the comp wheel design , but you should be safe to go to 1.5 bar no matter where on the map it is flowing , just looking at your turb scroll though , it appears to be fairly "fat" compared to the comp scroll , so you might be running a bit to the choke side of the map , I wouldn't be taking it past 2 bar without doing some testing of T2 numbers vs P2 to determine if the comp efficiency is indicating where on the map the flow is , as long as efficiency stays above 70% you should be OK .
Cheers John
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CH3NO2
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Post by CH3NO2 on Dec 10, 2017 15:54:54 GMT -5
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BFTO
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Post by BFTO on Dec 15, 2017 13:27:55 GMT -5
Installing T2 tomorrow. And installing an old VW ignition with huge spark. The fuel tank is made bigger. 1bar 495deg with AB attached on diesel. First run on diesel @ 3:00 into the video, ~375deg 1bar after 5min into the video. Ignore the P2-reading on the display.
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Post by Johansson on Dec 15, 2017 15:22:25 GMT -5
Awesome! Good job guys!
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Deleted
Joined: January 1970
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Post by Deleted on Dec 15, 2017 15:59:40 GMT -5
Nice work guys
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