reedy
Veteran Member
Joined: January 2017
Posts: 111
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Post by reedy on Jan 5, 2018 19:47:35 GMT -5
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Post by madrocketscientist on Jan 7, 2018 22:53:25 GMT -5
And some turbine bits arrived today, A couple of dents on the rear part of one of the NGV but otherwise all in good nick.
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Post by racket on Jan 8, 2018 0:01:04 GMT -5
Very Nice :-)
Now we need to measure up all the NGV and wheel angles and flow areas to see how they match the comp wheels , I hope its just the camera angle/s but the comp wheel looks a bit over shadowed by the NGV and turb wheel sizes.
Cheers John .
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Post by madrocketscientist on Jan 8, 2018 0:18:46 GMT -5
The comp wheel is the same diameter (84mm) as the turbine wheels, it might just be the camera angle. I am still thinking of the best way to get a good idea of the NGV blade shapes, considering taking a 2 piece casting around a blade or two and measuring that for size. I will get some better pictures and more details when I have more time Shannon
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Post by madrocketscientist on Jan 8, 2018 4:45:53 GMT -5
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Post by madrocketscientist on Jan 9, 2018 0:21:59 GMT -5
A few more images, The compressor wheel is 83.9mm diameter and the turbine wheel 84.6mm, so technically the turbine wheel is slightly bigger... (edited the compressor size, typo) Shannon
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Post by jetjeff on Jan 9, 2018 1:25:04 GMT -5
Hi Shannon,
4.7mm in difference isn't bad, I'd be more concerned about the one N.G.V. assembly having a couple dents in it.
Regards
Jeff
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Post by madrocketscientist on Jan 9, 2018 2:02:10 GMT -5
Hi Shannon, 4.7mm in difference isn't bad, I'd be more concerned about the one N.G.V. assembly having a couple dents in it. Regards Jeff Oops, the compressor size is 83.9mm diameter I have got most of the denting out of the NGV with some careful panelbeating. I will put it in the lathe to get the rest out using a dial indicator. They were on the very back of the exhaust flange and that overhangs out the back quite a way past where the turbine wheel sits. I dont think it even affected the clearances at all. The packaging could have been better to avoid the damage. Shannon
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Post by madrocketscientist on Jan 10, 2018 4:53:39 GMT -5
I received some glow plugs in the mail today and promptly disassembled a couple. I should be able to get the size down even further and make them into ignitors. The off the shelf turbine igniters are really expensive for what they are, these should work out quite a lot more affordable. The rated voltage is 4.4 volts. Shannon.
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Post by madrocketscientist on Jan 23, 2018 5:42:08 GMT -5
I have finally managed to get around to measuring up the turbine wheel and NGV sizes and angles. I have tried calculating things using the formulae in the Kamps and Schreckling books but end up with a really low figure for the thrust.
The measurements I get are as follows
NGV Vanes outer diameter 82.8mm Vanes inner diameter 61.4mm Outlet angle 30°
Turbine wheel Blade outer diameter 84.6mm Blade inner diameter 60.0mm Blade inlet angle 90° Blade outlet angle 37°
The AMT Olympus specifications (which these turbine parts seem to match up with) Rpm 108,500 Thrust 230N Mass Flow 0.45 Kg/s EGT 700°C
I must be doing something wrong in my calculations...
Shannon.
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Post by racket on Jan 23, 2018 18:07:46 GMT -5
Hi Shannon
What "numbers" are you getting for thrust ??
The Olympus will be running a lot higher Pressure Ratio than either the Kamps or Schreckling engines .
Could you post your calcs so that we can go over them for you .
Cheers John
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Post by madrocketscientist on Jan 24, 2018 0:10:04 GMT -5
John, I end up with around 70N for the thrust, I will see if I can type my calculations out. I Have been doing them on paper but my handwriting is terrible Shannon.
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Post by racket on Jan 24, 2018 18:47:12 GMT -5
Hi Shannon
The Olympus runs a 3.8:1 PR , your comp only puts out a 2.8 PR at similar rpm ..............you'll be needing more "tip" on your comp wheel , its a high Trim wheel at a 63 Trim , lotsa flow but poor Pressure Ratio , you need a comp wheel with a similar inducer size/flow but the exducer needs to be ~90 -93 mm , your current comp is smaller than your turb dia .
When I did some rough numbers using the "lowish" PR I couldn't get the required mass flow through the NGV without "excessive" gas speeds which would in turn produce too much power/gas deflection , in other words , theres a missmatch of components when using your low PR comp wheel .
Look around for a comp wheel/map that flows the required 0.45 kgs/sec - 1 lb/sec at your design rpm of 108k and with a PR of 3.8 :1 , probably a 48-52 Trim wheel
Cheers John
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Post by madrocketscientist on Jan 24, 2018 19:34:26 GMT -5
Thanks John,
I will have a look around and see what I can come up with.
Shannon.
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Post by madrocketscientist on Jan 24, 2018 20:30:16 GMT -5
John, I have measured up the Olympus compressor and get the following, Inducer 63mm Exducer 87mm Length 45mm Trim 52 From my reading about Gerald Rutten's turbine build it seems that there is still power to be gained from the turbine by going to a bigger compressor wheel. The amounts of thrust available from the smaller 70 and 74mm turbine wheels rival what the stock Olympus puts out. The GT42 series are looking to be in the right ballpark but finding good compressor maps is easier said than done! Shannon.
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