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Post by Johansson on Mar 17, 2012 15:27:12 GMT -5
The engine performed nicely today, I ran it up to 2.2bar and aprox. 61.000rpm without any problems. The reflective tape on the comp wheel dropped off at 2.0bar when the rev counter read 60.000rpm so I decided not to run it much higher without knowing the exact revs. The new silicone O-ring for the engine cover dropped the TOT by 60-70°C so instead of seeing over 700°C I had a pleasant 650°C TOT until I started to reach 2bar when it climbed to 670°C. The jetpipe pitot tube read 0.45bar at 2.2bar P2. The oil pump cannot hold the pressure high enough once the oil starts to heat up so I will have to build a gear pump to solve this. I also had some slight vibrations at certain revs that needs curing, it might be that the home made spacer ring behind the comp wheel isn´t perfectly flat so I will have its surfaces precision ground and see if that helps, if not I will send the rotor away for rebalancing in case the turbine rubbing has affected the balance somewhat. With a smaller jet nozzle and more revs I will face an impossible task if I try to push the test stand again, it was hard enough now at 2 bar P2 so it feels like I will get some serious speed out of the jet kick next year! Cheers! /Anders
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Post by racket on Mar 17, 2012 17:47:20 GMT -5
Hi Anders Congratulations on an"uneventful " test run 0.45 bar - 6.6 psia at 670C should be producing ~ 78 deg C drop across the jet nozzle for a velocity of ~1400 ft/sec -425m/s. The comp map gives a mass flow at 3.2 PR of ~130 lbs/min -2.16 lbs/sec , so a theoretical thrust of ~94 lbs ~430N , still got at least another 30-40% more to go from any higher rpm , you'll notice a big jump once past 66,000 rpm ,.................all looking good , temps are still highish , but within design ;D The "vibration" at various rpm could be the rotor going through its "normal ??" vibrations , have a read of this paper www.rodyn-inc.com/ISCORMA3_Gunter%26Chen_TurbochargerVer2.pdf . Its those "vibrations" that make it hard to mount a turbo rotor in ball bearings and have them survive without "damping" It looks like the guys all enjoyed the test run , congrats again on a successful test :-) Cheers John
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Post by ernie wrenn on Mar 17, 2012 20:40:04 GMT -5
Great run-up..
Do you have a tension gauge? It would be nice to see the thrust generated..
ernie
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Post by Johansson on Mar 18, 2012 4:00:25 GMT -5
Thanks guys! It felt good to finally have moved past the emergency repair/remake phase of the build. Unfortunately no thrust measurements, the heavy test stand standning on gravel wouldn´t have given any accurate readings anyway so I didn´t bother to fit a gauge to the tiedown rope. I think I will take the engine apart and send the rotor away for balancing anyway just to be sure, I don´t know the right position of the comp wheel on the shaft either and since the rotor is dynamically balanced with the comp wheel fitted to the shaft that might be the main reason for the imbalance. There are some rubbing marks on the turbine wheel after the comp wheel drop and those might have upset the balancing as well, so better safe than sorry. Most of the guys attending to the test run are well familiar with gas turbines and other jet contraptions, my friends from the Mobacken team and Black Hole Racing along with a couple of other friends who have helped out at the Speed Weekend race with the jet kick.
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Deleted
Joined: January 1970
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Post by Deleted on Mar 18, 2012 4:18:10 GMT -5
Hi All looking very good
as for oil pump, you mite want to have look at one of these, a few of us over here are running them
Ebay 320562646412
The new mobil 10w60 oil works very well, don't thin out to much at high temps
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Post by Johansson on Mar 18, 2012 4:49:41 GMT -5
I have two of those pumps as oil scavange pumps, are they really capable of 5kg oil pressure? I sort of remember a test I did years ago to find out if it was suitable as a fuel pump and the max pressure wasn´t impressive, but I might be wrong.
10w60, never heard of it before. Will check it out, thanks!
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Deleted
Joined: January 1970
Posts: 0
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Post by Deleted on Mar 18, 2012 5:23:27 GMT -5
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Post by Johansson on Mar 18, 2012 6:12:32 GMT -5
Aha, that is a bigger version of the pumps I am using. If it manages 5 bar oil pressure with low viscosity oil it would suit me perfect!
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Post by turbochris on Mar 18, 2012 7:15:30 GMT -5
Did anyone see the spool in the link John posted? Did someone actually make a turbo with a 2 stage compressor?
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Post by pitciblackscotland on Mar 19, 2012 12:22:57 GMT -5
Hi Anders, Nice run on your engine Have you thought of using a oil pump like John has on the 10/98?. Here is a cheap Subaru oil pump on e bay Item number: 220924114647. Cheers, Mark..
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Post by Johansson on Mar 19, 2012 15:26:10 GMT -5
Hi Anders, Nice run on your engine Have you thought of using a oil pump like John has on the 10/98?. Here is a cheap Subaru oil pump on e bay Item number: 220924114647. Cheers, Mark.. Thanks! I´ve considered building an oil pump from a gear pump and a 12V motor, but since the JABSCO pump Andy told me about should work I think I´ll pay the extra buck to get a ready made pump.
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Post by racket on Mar 19, 2012 17:10:10 GMT -5
Hi Chris
I haven't come across any of those two stage turbos , they seem to be one of those "just around the corner" designs that never make it onto the market , probably because of an inherent design problem , they've gone instead for billet wheels and/or cast titanium to get the higher pressure ratios at a reasonable cost and "simplicity".
Cheers John
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Post by racket on Mar 19, 2012 17:17:15 GMT -5
Hi Anders
One thing we have to consider in addition to the usual turbo lube pressure/flow is the extra heat being picked up by the lube as it enters and leaves our engine's bearings , the T2 air temps surrounding the lube plumbing can be at >150 C also shaft tunnels and diffuser walls are subjected to radiant heat from the flametube , I feel we get ~twice the temp rise rate as a turbo , so some form of oil cooler is essential unless we use a large lube supply for anything other than short test runs .
Cheers John
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Post by Johansson on Mar 20, 2012 0:49:23 GMT -5
Hi Anders One thing we have to consider in addition to the usual turbo lube pressure/flow is the extra heat being picked up by the lube as it enters and leaves our engine's bearings , the T2 air temps surrounding the lube plumbing can be at >150 C also shaft tunnels and diffuser walls are subjected to radiant heat from the flametube , I feel we get ~twice the temp rise rate as a turbo , so some form of oil cooler is essential unless we use a large lube supply for anything other than short test runs . Cheers John I have a large Mocal oil cooler at home just waiting to be fitted, I didn´t bother during the first test runs since I didn´t expect the engine to last long enough to get the oil up to temps.
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Post by racket on Mar 20, 2012 3:21:18 GMT -5
Hi Anders LOL...............guess you'll have to accept the fact that the engine might keep working and fit the cooler ;-)
I was running ~7 litres of 5W-40 synthetic oil for the 10/98 tests and it only took a few minutes to get the temp up close to 100 C , at the time I was a bit surprised by how quickly it happened , I was expecting a little longer from my turbo experience of oil warming , the GT6041 by comparison was relatively "slow" at heating the ~6 litres in its oil tank.
Cheers John
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