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Post by smithy1 on Aug 25, 2014 17:10:42 GMT -5
Ah...excellent. Pro-Modified is the equivalent of "Top Doorslammer" here in Australia, our guys are running consistent 5.9's now, crazy quick.
Like John, I look forward to your test numbers, will be interesting to see if the temps settle down without the free power unit fitted.....this will then give you an idea of where to look.
Cheers, Smithy.
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Post by Johansson on Aug 26, 2014 15:17:06 GMT -5
I just wrote down half an A4 paper full of stuff I need to get done around the house before the snow falls, so it feels like I have my work cut out for me. Will still try to test the bike as planned this weekend, stay tuned.
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Post by racket on Aug 26, 2014 16:52:04 GMT -5
Hi Anders
LOL, naughty boy , forgetting your home duties in preference to wasting time on your bike project ;-)
Looking forward to the weekend, those numbers will be interesting
Cheers John
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Post by smithy1 on Aug 26, 2014 18:17:57 GMT -5
Yeah John....aren't we lucky not to get lumbered with snow here in most parts of Australia? Even in the middle of winter we can still get things done around the house..! Bring on Spring and daylight savings..!
Anders, you should pack up everything and setup "down-under" here with us.!
Cheers, Smithy.
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Post by racket on Aug 26, 2014 19:34:57 GMT -5
Hi Smithy
Heh heh , this year winter has been cold up here on the coast , a few times it got down to 6 degrees C overnight, but then I had to strip off to my tee shirt in the daytime whilst fishing in the sunshine on the breakwall .
Yep , looking forward to Spring :-)
Cheers John
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Post by turbochris on Aug 29, 2014 23:19:32 GMT -5
I've been busy working on this pro mod, I'm on the put crew. Y'all need to come watch
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Post by Johansson on Aug 30, 2014 16:18:00 GMT -5
Very cool looking Pro Mod Chris! I did the static test today, the crappy english is only for you guys. The Gopro video of the gauges. Some closeups of the gauges at 15°C and 1018hPa ambient pressure: 0.4bar (32.900rpm): 1.0bar (47.900rpm): 1.5bar (55.000rpm): 2.0bar (no RPM reading): 2.5bar (no RPM reading): Too bad the reflective paint on the compressor nut came off, but I´ll fix that before the next test. Cheers! /Anders
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metiz
Senior Member
Joined: April 2011
Posts: 297
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Post by metiz on Aug 30, 2014 18:13:27 GMT -5
Any preliminary conclusions you can draw from this test?
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Post by racket on Aug 30, 2014 18:41:24 GMT -5
Hi Anders
Thanks for the "numbers" ..............very interesting , even if a tad confusing .
TOTs were still high at ~675 C for idling conditions considering the "open pipe", but then they didn't change much until you were up over the 3:1 PR at which point you were really starting to build some rather high total pressures downstream in the exhaust, 0.6 Kg/cm2 is ~8.5 psit- 1.57 PR thats getting up into the range I'd be expecting with a jetnozzle on her , when I was testing the 10/98 engine I only had a 1.45 PR with a 89mm jet nozzle ............heres an extract from my test .......
..... "A couple of short burst were made to 70,000 rpm -106% - 1,700 ft/sec tip speed (last line on the comp map ) with the comp putting out a 3.88 :1 PR and 8.5 psit in the jetpipe producing a PR across the jetnozzle of 1.64:1 and gas velocities of ~1650 ft/sec at ~700 deg C for a theoretical thrust of ~115 lbs ( ~128 lbs if at sea level with "heavier" air ) from its ~2.25 lbs/sec mass flow (2.5 lbs/sec if at sea level)" ................
Could your exhaust bend be creating enough "backpressure" to raise those P4t pressures that high , with a 3.5 PR you'll have an ~165deg C rise in compression requiring ~145 deg C drop in the turb stage, so if you were running an ~725C in the exhaust you'd have a T I T of ~870 deg C , still OK , but a bit high for an open pipe exhaust even taking into account the slight area restriction between exducer and pipe ID .
It could be a result of your largish NGV throat area allowing a bit more than ideal mass flow.
How does this set of numbers compare against your test stand numbers ??
Cheers John
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Post by racket on Aug 30, 2014 20:24:12 GMT -5
Hi Anders
Your TOT g/g does a strange thing at 0.28 seconds ( second vid of instruments) , the temp drops back to ~525 C , then climbs again to >625C whilst the P2 remains constant, any thoughts about this ??
Would it be possible to add a T2 temperature gauge to see if the high temperature is being caused by compression inefficiency , there doesn't appear to be any airbox restriction but there could be turbulence problems with air going into the compressor wheel thats causing compression problems , I used an unsheathed thermocouple for the 10/98 engines T2 reading , it was situated at the diffuser outlet , but even a case surface temperature pickup ( suitably insulated externally) would give a reasonable indication .
At a 0.5bar P2 it should be at less than 65 deg C on a 15 C day , at 1.0 bar P2 <103 C, 1.5 bar P2 <135 C , 2.0 bar P2 <163 and 2.5 bar P2 <187 C
Cheers John
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gidge348
Senior Member
Joined: September 2010
Posts: 426
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Post by gidge348 on Aug 30, 2014 20:32:30 GMT -5
HI Anders, Just a small observation.
I noticed that the P1 pressure did not change until you got to 2.5bar P2. The change was only small (maybe 0.02bar) but noticeable. I was wondering if you have a bell mouth inside the air-box? Could there be some turbulence in there?
Cheers Ian...
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gidge348
Senior Member
Joined: September 2010
Posts: 426
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Post by gidge348 on Aug 30, 2014 20:56:22 GMT -5
I have been looking into ducting for my project and came a cross a thesis with regards to inlet ducts on UAV's and how what looks like a good design may not be? "Active Flow Control in an Advanced Serpentine Jet Engine Inlet Duct" (repository.tamu.edu/bitstream/handle/1969.1/ETD.../KIRK-THESIS.pdf) It's a lot of reading, but the bottom line is a bell mouth on the intake is needed with as large a plenum in front as possible? Would it be feasible to run the test again without the air-box? Or maybe the problem will sort itself with the bike moving or a positive airflow into the air-box??? Cheers Ian...
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gidge348
Senior Member
Joined: September 2010
Posts: 426
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Post by gidge348 on Aug 30, 2014 21:22:47 GMT -5
Hi Anders,
Just had a quick look at your post of 20 August and the pic of the air-box and have a theory.
I note that the inlet does have a bell mouth, but the outer diameter of it is flush with the rear wall of the plenum. There are a lot of articles on the net about bell mouth design but all have a standoff between the outer diameter and any rear wall.
My theory would be that this may be causing all kinds of weird flows into the engine as air flows around the corners, bolts etc.
Cheers Ian...
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Post by Johansson on Aug 31, 2014 2:14:08 GMT -5
Hi guys! I haven´t got time to answer all your questions now but I´ll get to it tonight when my daughters are asleep. The temp drop John asked about was probably air from the scuba tank cooling the exhaust flow, you can see in the first video that the temps start to rise when I close the bottle valve. It feels like the 4" bend is restricting the exhaust a bit, yes. I have the original jet nozzle and plan to weld it to the end of the bend to see what it does to the numbers, that should cancel out any restrictions in the bend since the nozzle will be the larger restrictor. The comp inlet is bellmouthed and sits flush with the air box, regarding the air box restriction I was surprised I could run the engine this hard stationary without any ram air. My newly found friend Fläppen (professional gas turbine designer and fellow DIY turbine fan at Volvo Aero) will punch the numbers into one of his design programs and make a complete computer model of it. I´m on the edge of my chair right now waiting for the results and I´ll tell you all about it immediately. Cheers! /Anders
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Post by racket on Aug 31, 2014 2:16:45 GMT -5
Hi Ian
Well spotted :-)
A boundary layer might develop on the flat wall that is eventually "dragged??" into the bellmouth , they can get up to 0.3" thick and can be a problem , a standoff bellmouth wouldn't be able to "pickup" that boundary layer ..........mmmmmmm, interesting thought , a T2 gauge should soon tell us if theres a turbulence problem affecting compression.
Cheers John
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