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Post by racket on Oct 21, 2020 17:01:54 GMT -5
Hi Thomas Theres a problem with reconciling your RPM vs P2( P3) pressure , 90,000 RPM will produce a tip speed of ~1,800 ft/sec -550m/s , this is very fast and should normally have the compressor producing a P2(P3) ~3.5 Bar , this combined with your T2(T3) of 218C which represents an efficiency of ~70% on a 15 C ambient sorta indicates a "problem" . Your temp drop across the turbine stage is a little "low" at only 130 degrees , this would normally be a number associated with only a ~150 C deg rise through the compressor , a ~3:1 PR What sized turb scroll A/R does the turbo have ?? you could be flowing well off best efficiency . Pitot tube positioning , this pic shows where mine is ibb.co/gzCLnCN, a little downstream of the turb wheel and ~20-25 mm off the jetpipe wall in the area of greatest flow , the A/B will be too hot for any metal tube to survive Cheers John
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slittlewing
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Posts: 458
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Post by slittlewing on Oct 25, 2020 11:54:48 GMT -5
Hi Guys, The lube oil control box is slowly coming together. It is now bench tested and after correcting a design error it seems to work as planed. Have some modification work left to do on the vehicle with electrical connections but then it time to make some noise and do some testing and tuning of the system. Kind regards Thomas Well done on getting lots of testing done Thomas, your PCB case is really smart - particularly like the plug in fuse holders!! Nice details! The datalogging is also really impressive. What software are you using to view the graphs? Cheers Scott
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Sweetenough
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Post by Sweetenough on Oct 28, 2020 2:19:58 GMT -5
Thanks for your input John, Will try to meassure the compressor outlet temperature better next run (have been aiming for this the last 3-4 runs but failed in taking readings...) since I think the current meassuring position gets a fair admount of radiation heat from the flametube. Do not know the turb scroll A/R unfortnuatly, could it be determined from markings below? Or meassured on the housing in some way? By the way, would a low or high turb A/R be best for DIY jet engines? The exhaust housing have following marking One side: A1 5550-5060 606-145 HSM Other side: 10L25 Bearing housing has this sign: Will try to arrange a pitot tube as well. As an first indication, would it be any good to insert a pitot tube in the AB exhaust and meassure when AB is not running? Just to size the pressure gauge correctly, what kind of pressure could be expected? Kind Regards Thomas
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Sweetenough
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Post by Sweetenough on Oct 28, 2020 2:38:29 GMT -5
Hi Guys, The lube oil control box is slowly coming together. It is now bench tested and after correcting a design error it seems to work as planed. Have some modification work left to do on the vehicle with electrical connections but then it time to make some noise and do some testing and tuning of the system. Kind regards Thomas Well done on getting lots of testing done Thomas, your PCB case is really smart - particularly like the plug in fuse holders!! Nice details! The datalogging is also really impressive. What software are you using to view the graphs? Cheers Scott Thanks Scott, I am using Grafana as trend viewer. Works quite good. Only "problem" if you are picky is that it only can handle 2 different Y scales in one graph. But you can however create several graphs and then connect the cursors so you can view variables with different scales at the same time. I guess I am a bit spoiled, at work we have trend viewers that can handle one Y scale for each variable in the trend that is really handy when looking at data. Kind Regards Thomas
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Post by racket on Oct 28, 2020 3:14:53 GMT -5
Hi Thomas
The turb scroll A/R is generally cast into the housing .
A temporary pitot into the unlit A/B would work , expect ~0.5 - 0.7 Bar total pressure , any more is a bonus .
Cheers John
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Sweetenough
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Post by Sweetenough on Nov 2, 2020 8:33:33 GMT -5
Hi Guys, Finished the fan cover and mounted the new 50 row oil cooler and made a new test run yesterday. Started without cooler and thought that the oil tank in alumium would radiate away heat. The changed to, 11row with computer fans, then changed to 25row wiht 7" fan and now to 50 row cooler with dual fans and custom made fan cover. Will it be enough? Had great hope that it should be "to large" and would only have to operate on reduced capasity but it turns out for longer high power runs I have to run both the cooler circulation pump and cooling fan at nominal battery voltage to keep the heat down so it works but not with as much margin as I had hoped. When running during the winter on ice with speed it will of course be much easier but since I started work on improving the oil system I want it to perform in the workshop as well. Some head scratching and data analyse, then it will be more test and tune. Also run into a horse problem, a neighbor came by and said that his horses went mad of the noise. Think I need to by some hearing protection for the horses before the next run Installed a temporary t3 meassurment for comparisson, put a thermocouple just under the silicone hose. See pic. But to my surprize it showed simular values as my other t3 meassurement. Running with AB @ 90000 rpm p3 3,14bar t3 orginal 205°C temporary 207°C t7 (exhuast temp) 720°C t5 (turbo inlet temp) 844°C Have not got around to arrage a pitot tube yet but thats on the future plan. And more AB fuel.... And maybe change the fuel injection nozzles to the AB Will hook up dual bosch 044 pumps for testing purpose and see if that drowns the AB. My AB sparkplugs seems to be "one time" only, melts and needs to be replaced after each run. Do you guys have similar problems? Kind Regards Thomas
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Post by wannabebuilderuk on Nov 2, 2020 10:30:48 GMT -5
My AB sparkplugs seems to be "one time" only, melts and needs to be replaced after each run. Do you guys have similar problems? Got any photos of the AB sparkplug setup, it shouldn't be melting after each use so sounds like something is going wrong. Fuel directly spraying ontop/near it? Also love the cooler size progression picture, "hmm is this enough? More?, more??? Screw this!" lol
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Post by racket on Nov 2, 2020 16:07:06 GMT -5
Yep , horses hate turbine sounds , they can hear them from quite a distance , they get flighty , I once had problems even though the horses were >500 metres away .
Thats a lot of oil cooler .
Your comp discharge temps are OK for that PR , and reasonable efficiency .
Sounds like your A/B plug needs to be displaced further towards the turbo to find a cooler spot
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Sweetenough
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Post by Sweetenough on Nov 4, 2020 14:40:11 GMT -5
My AB sparkplugs seems to be "one time" only, melts and needs to be replaced after each run. Do you guys have similar problems? Got any photos of the AB sparkplug setup, it shouldn't be melting after each use so sounds like something is going wrong. Fuel directly spraying ontop/near it? Also love the cooler size progression picture, "hmm is this enough? More?, more??? Screw this!" lol Yepp, it is located approx 12 centimeters down stream the diameter change. It is in the fuel injector path but hidden behind the flameholder. Maybe it is time to change position or improve the fuel distrubution or build a new AB
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Sweetenough
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Post by Sweetenough on Nov 4, 2020 14:52:30 GMT -5
Yep , horses hate turbine sounds , they can hear them from quite a distance , they get flighty , I once had problems even though the horses were >500 metres away . Thats a lot of oil cooler . Your comp discharge temps are OK for that PR , and reasonable efficiency . Sounds like your A/B plug needs to be displaced further towards the turbo to find a cooler spot Thanks John, I wonder if it is my problem that my neighbor have horses next to my property or if it is the neighbors problem that the horses get crazy when I run my jet engine? Earlier on the seasson they have sheep that makes noise 24/7 next to my property that really disturbs me... Feel a little bit sorry for the horses though. Our cat does not like my jet hobby either... or my girlfriend for that matter.
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Post by racket on Nov 4, 2020 15:29:05 GMT -5
You mentioned your sparkplug is "hidden behind the flameholder" , do you have another flameholder besides the "step" , the step is your flameholder in that design. Have a read of this apps.dtic.mil/dtic/tr/fulltext/u2/a067277.pdf bottom of page 27 for ignitor position Cheers John
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Sweetenough
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Post by Sweetenough on Nov 5, 2020 4:05:31 GMT -5
You mentioned your sparkplug is "hidden behind the flameholder" , do you have another flameholder besides the "step" , the step is your flameholder in that design. Have a read of this apps.dtic.mil/dtic/tr/fulltext/u2/a067277.pdf bottom of page 27 for ignitor position Cheers John Thanks John, back when I builded the AB all I information I had/used was pictures of Mobacken racings differnt AB attempts. So I made a not needed flame holder just after the step change. Maybe it is time to make a new AB with general improvements to search for that extra performance Kind regards Thomas
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Sweetenough
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Post by Sweetenough on Nov 30, 2020 10:36:42 GMT -5
Hi Guys, Have anybody used a brushed RC speedcontroller instead of the "normal" PWM modules? For fuel/oil pumps? Seems like a compact and easy solution. Then connect it to an Arduino to control it. Just ordered a couple of controllers to test but is still interested if someone have tried this before?
Kind Regards Thomas
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slittlewing
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Post by slittlewing on Dec 1, 2020 5:31:56 GMT -5
Its a good point Thomas, I have not tried it yet but will be doing something similar with the Kart Oil Pump. For single pump control it could be a great way of doing it, but for controlling multiple pumps I think a custom PCB is a neater solution.
Look forward to seeing your results!
Cheers
Scott
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slittlewing
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Post by slittlewing on Dec 1, 2020 5:55:05 GMT -5
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