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Post by enginewhisperer on May 6, 2018 17:27:48 GMT -5
good luck!
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Post by smithy1 on May 6, 2018 19:02:56 GMT -5
Yes John...good luck mate...!! We need this machine to hum nicely......it did sound great before and I'm sure it will again.  Smithy. |
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Post by racket on May 6, 2018 19:55:31 GMT -5
Hi Guys Well ...............there is some improvement , got up to 1.75 Bar P2 - 2.75 PR before temps again spiked and fuel pressure up at >90 psi . The good news is that comp efficiency improved , maybe due in part to the cool morning at 16 deg C , but efficiency was at ~80% between 1 and 1.75 Bar , a couple of percent improvement , I also checked the inlet air direction indicator ( bit of string), and it shows the airflow is being deflected nicely by the IGVs and is flowing at a considerable angle from axial . A bit of video youtu.be/mZH5i0iyHR0 I did notice that the trailer and back of car suddenly lifted when I killed the power after the full bore run , she was producing some thrust . The test run was conducted with the "old" jetpipe installed to give a comparison with previous runs , I still think its "choking"" the flow somewhat , so will install the larger diameter "new" pipe for further tests . Cheers John |
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Post by racket on May 6, 2018 20:19:44 GMT -5
And another one of me stuffing up the first spoolup attempt youtu.be/8eQzNJ9pUC8 ..................not quiet enough idle fuel flow Cheers John |
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Post by smithy1 on May 6, 2018 21:25:06 GMT -5
That sounds more like it John...well done Sir....a little warm but heading in the right direction. Yep, open up the pipe a tad and she might come down to a reasonable TOT...800C+ is a tad high @ 1.75 bar, she should be quite happy at ~25-26psi P2....getting close to the sweet spot. But nice nonetheless... Smithy. |
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Post by pitciblackscotland on May 6, 2018 22:10:07 GMT -5
Nice one John  I see the electric start is still working OK  Cheers, Mark. |
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BFTO
Veteran Member
Joined: February 2016
Posts: 128 
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Post by BFTO on May 7, 2018 0:26:40 GMT -5
You cant run her in the backyard anymore?  |
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Post by racket on May 7, 2018 0:46:40 GMT -5
LOL...............no more backyard tests :-(
But only a 5 minute drive to a quiet spot just outside the village near the sand quarry .
Yeh Mark , electric starter still doing the job ...........just .
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Post by stoffe64 on May 7, 2018 1:55:58 GMT -5
Congratulations john, she is getting there!
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Deleted
Joined: January 1970
Posts: 0
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Post by Deleted on May 7, 2018 2:27:06 GMT -5
Nice John
Always good to know that changes you have made are an improvement :-)
To be moving tailor and the car, its putting a good amount out already..... good signs
Chat Soon
Andy
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Post by racket on May 9, 2018 20:22:21 GMT -5
Hi Guys
I've been working some numbers and the fueling flow rate isn't looking good .
At 1 Bar - 15 psi P2 I had ~27 psi fuel pressure so ~12 psi of pressure drop across the fuel system between the pump where the pressure is measured and the injector outlets.
An insitu test was conducted with 12 psi on the fuel pressure gauge and a flow of 1.5 litres per minute was measured exiting the combustor drain , which when taken in conjunction with the TOT assuming an ~625 C degree rise in the combustor indicated an airflow rate of ~2.7 lbs/sec , an amount which would be impossible to get through the turb stage with only 1 Bar of pressure .
Subsequent insitu testing for the 1.5 Bar P2 numbers produced an even worse reading of ~2.2 lpm of fuel from a 23 psi pressure drop .
During a full throttle attempt the fuel pressure registered 92 psi with ~26.5 psi P2 so a 65.5 psi pressure drop , the insitu test produced a fuel flow of a bit over 4 lpm - 7 lbs/min , a massive amount of fuel , probably 50% more than what should be expected from mass flow and temperatures .
Something is wrong with the combustor :-( ....................I'll have to do some "Combustor Intensity" calcs to see if I'm simply overloading the available combustion volume , the residence time might be just too short .
Maybe a special brew of 50/50 mix of kero/petrol might be worth a try , something like JP3 - JP4 - Jet B .
Because of the high projected airflow rate I need a fairly large cross section for the flametube , but because of the short distance between comp and turb when using the standard shafting , the "length : diameter ratio" is only ~1.2 :1 , very short :-( .................total volume of the flametube up to the NGV inlet is only ~200 cubic inches - 0.116 cubic feet .
With 4 lpm/7 lbs/min of kero , thats ~130,000 BTUs/min or 7,786,800 BTUs/HR , divide by our 0.116 cubic feet , gives us 67,127,586 BTUs/HR/CF, divide by my PR of ~2.8 at the time , gives us ~24 million BTUS/cubic foot/ HR/atmosphere, me thinks thats a tad high , I originally designed for about half that when running at a 3.5 PR .
The new mods with the square springs inside the evap tubes has produced a bit better combustion allowing a higher PR before the problems start , but I might just be coming up against a "brick wall" unless I can increase combustion speeds/efficiency .
Time to sit in the chair and think a bit .
Cheers
John
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Post by azwood on May 10, 2018 5:06:00 GMT -5
Hi Guys I've been working some numbers and the fueling flow rate isn't looking good . At 1 Bar - 15 psi P2 I had ~27 psi fuel pressure so ~12 psi of pressure drop across the fuel system between the pump where the pressure is measured and the injector outlets. An insitu test was conducted with 12 psi on the fuel pressure gauge and a flow of 1.5 litres per minute was measured exiting the combustor drain , which when taken in conjunction with the TOT assuming an ~625 C degree rise in the combustor indicated an airflow rate of ~2.7 lbs/sec , an amount which would be impossible to get through the turb stage with only 1 Bar of pressure . Subsequent insitu testing for the 1.5 Bar P2 numbers produced an even worse reading of ~2.2 lpm of fuel from a 23 psi pressure drop . During a full throttle attempt the fuel pressure registered 92 psi with ~26.5 psi P2 so a 65.5 psi pressure drop , the insitu test produced a fuel flow of a bit over 4 lpm - 7 lbs/min , a massive amount of fuel , probably 50% more than what should be expected from mass flow and temperatures . Something is wrong with the combustor :-( ....................I'll have to do some "Combustor Intensity" calcs to see if I'm simply overloading the available combustion volume , the residence time might be just too short . Maybe a special brew of 50/50 mix of kero/petrol might be worth a try , something like JP3 - JP4 - Jet B . Because of the high projected airflow rate I need a fairly large cross section for the flametube , but because of the short distance between comp and turb when using the standard shafting , the "length : diameter ratio" is only ~1.2 :1 , very short :-( .................total volume of the flametube up to the NGV inlet is only ~200 cubic inches - 0.116 cubic feet . With 4 lpm/7 lbs/min of kero , thats ~130,000 BTUs/min or 7,786,800 BTUs/HR , divide by our 0.116 cubic feet , gives us 67,127,586 BTUs/HR/CF, divide by my PR of ~2.8 at the time , gives us ~24 million BTUS/cubic foot/ HR/atmosphere, me thinks thats a tad high , I originally designed for about half that when running at a 3.5 PR . The new mods with the square springs inside the evap tubes has produced a bit better combustion allowing a higher PR before the problems start , but I might just be coming up against a "brick wall" unless I can increase combustion speeds/efficiency . Time to sit in the chair and think a bit . Cheers John So your saying the burn rate is to slow for the air speed? Hence the 50/50 mix |
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Post by stoffe64 on May 10, 2018 5:13:55 GMT -5
Hi John...So theoretically, this With a 50/50 mix could work With say a too small combustor? On a normal turbo based engine
Cheers /stephan
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Post by racket on May 10, 2018 19:01:50 GMT -5
I haven't the faintest idea if the 50/50 mix will improve things , all I can do is try something and see what happens .
I was very hopeful that the evap mods would have improved things more than they did , but theres a chance that the mods simply meant more fuel was in contact with the tube wall and kept the wall too cool to evaporate the higher boiling point bits of the kero , perhaps all the lighter fractions evaporated compared to before where they may have been a broader range but less off it .
Vapouriser tubes never evaporate all the fuel, even in full sized aero engines, a large percentage gets blown onto the front wall of the flametube to be evaporated off , but it appears I have a greater percentage dribbling down the front wall the higher the P2 , this is whats giving me an ever increasing difference in temps between the two thermocouples as P2 increases.
Stephan , ...........on a turbo based engine theres no excuse for having an undersized combustor , but on our "micro" types it gets more complicated as axial distance is severely limited , ideally we need ~1.5 times the flametube diameter/annular width as the length of just the Primary Zone , my whole flametube length is only 1.2 times, its extremely short.
If the 50/50 mix doesn't cure the problems I can always try a bit higher concentration of petrol, then if that fails , I probably need a different flametube , with more evap tubes to change the effective flametube L/D ratios ....................the funny part is , I originally was going to have 27 X 3/8" tubes , a 50% increase on our 18 X 3/8" TV94 number to match the increased mass flow , but decided the extra complication was something I didn't need ...............duh, it might have been a smarter move in hindsight .
Cheers
John
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Post by azwood on May 10, 2018 19:09:57 GMT -5
What about some sort of danfoss jet on the end of your evap tubes to make sure the fuel that gets out atuly cums out in a mist just an idear I'm not that educated on them yet
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I see the electric start is still working OK 
