Feathers
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Joined: August 2010
Posts: 169
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Post by Feathers on Jan 13, 2012 9:58:35 GMT -5
RIP Sorry for your loss... Just forwarded you those files. And I have heard back from George, unfortunately 2,500 USD for a unit is out of my budget... I've send Adrian bennet and Tim arfons emails describing my project and what I would need. Hoping to hear back soon! Thanks again for the info and I hope you get your computer up and running again!
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Post by pitciblackscotland on Jan 14, 2012 2:18:05 GMT -5
Hi Feathers, Thanks mate I sent you a pm.
Cheers, Mark..
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Feathers
Veteran Member
Joined: August 2010
Posts: 169
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Post by Feathers on Jan 15, 2012 11:04:12 GMT -5
Does anyone know what kindof "oil attention" a JFS unit needs?
Does it need constant pressure, "drip" feeding, etc?
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Post by pitciblackscotland on Jan 15, 2012 12:21:11 GMT -5
Hi Feathers, he is a bit of info on the power turbine unit. the lubrication system is a sump type splash system sump capacity 13.5 fluid ounces. So in your set you will need to circulate the oil, i don't no what pressure. And don't forget to use a good oil cooler . I'll have a read in my JFS technical manual to get some more info for you . Cheers, Mark.
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Feathers
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Joined: August 2010
Posts: 169
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Post by Feathers on Jan 16, 2012 15:01:30 GMT -5
Thanks again Mark.
The oil cooler I've got on the engine now is a beast, and should more than handle the turbo and the N2 stage. I've never had oil temperatures over 100*F yet. And it looks like $800 is the last word on the unit. It could very well be worse! Better start saving.
By the way, did those files ever make it back to you?
Thanks!
Feathers
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Feathers
Veteran Member
Joined: August 2010
Posts: 169
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Post by Feathers on Jan 16, 2012 15:34:33 GMT -5
So I've taken apart the engine to check out all the components after its first ~hour and a half of runtime. And finally, I was able to separate the turbine scroll from the core, and completely disassemble the turbo! As far as I can tell, everything looked very sound and smooth. Still zero play in the shaft. Everything looked good from a mechanical standpoint, but was filthy. So I cleaned everything up with a wire wheel, brake cleaner, dried it all, then went over it with an oil cloth (all this with the exception of the inside of the core, turbine and compressor wheels, shaft and bushings of course ) Not noticing too much wear and tear on the flame tube and evap system. Happy with that. Here's some pics: Feel free to add any input, I think everything looks okay, but I've got no expert eye yet. -Feathers
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Post by racket on Jan 16, 2012 20:26:23 GMT -5
Hi Feathers
All looking good :-)
Just a couple of comments , generally evaporator outlets need to be ~1.5 times their diameter away from the "wall" they discharge against , from the first pic I'm not sure you have that sort of clearance.
Your turb wheel's exducer has the blading at a very large (open) angle, have you noticed any problem with temperatures at higher power settings , generally such a large angle will require a "tight" turb scroll to limit comp flow and provide sufficient pressure drop in the scroll to power the comp as theres going to be very little power developed from gas deflection with such an open exducer .
Cheers John
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Feathers
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Joined: August 2010
Posts: 169
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Post by Feathers on Jan 16, 2012 22:04:17 GMT -5
Hey John!
I didn't know that about the evap tubes. Is it absolutely essential?
And this might answer your second comment. I've noticed that the turbine inlet on my particular VT-50 is alot longer than in the other vt-50s and st-50s I've seen (the ones with four bolts on the turbine inlet rather than six). As well, the turbine scroll seems to be a bit smaller in general. I think this is what your talking about.
Anyhow running at 15 PSI P2, I've only measured exhaust temps at 450*C.
What could I do about the evap issue?
Thanks!
Feathers
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Post by racket on Jan 16, 2012 22:20:47 GMT -5
Hi Feathers
With the evaporators we need sufficient room between the end of the evap and the wall so that there isn't any "backpressure" created which may reduce the airflow through the evap, we're trying to create a reasonable fuel/air mix exiting the evap , a 1.5 times diameter gap provides a reasonable distance/area for the mixture to flow through , you could simply cut off the ends of the evaps to produce a bit more clearance , it looks like you have plenty of surface area as is , so a small amount off the length of the outlet arm shouldn't be a problem
Yep, sounds like you've got a "tight" scroll , 450 C is a low temp for a 2:1 PR , plenty of scope for increasing that as your P2 pressures rise :-)
Cheers John
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Feathers
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Joined: August 2010
Posts: 169
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Post by Feathers on Jan 17, 2012 10:52:57 GMT -5
So cut along the red lines? I think that would almost eliminate any backpressure. Thanks for the advice! -Feathers
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Post by racket on Jan 17, 2012 15:34:27 GMT -5
Hi Feathers
I'd cut them off square , if you cut them on the angle the fuel mix will be expelled away from the evaps , you want the mix to hit the wall square on, then mushroom over and burn down around the evaporator legs/arms.
Cheers John
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Post by pitciblackscotland on Jan 18, 2012 1:17:50 GMT -5
Hi Feathers, Yep files came threw thanks. I am away for this week so will get you some more info the the power turbine next week.
Cheers, Mark..
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Feathers
Veteran Member
Joined: August 2010
Posts: 169
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Post by Feathers on Jan 20, 2012 22:08:53 GMT -5
So my gear-type oil pump has been leaking badly forever. It got to be too annoying to deal with, so I sealed up the "face" with a larger and more supple o-ring. The problem now is that the cover of the face of the pump ( made from cheap brass plate) is warping. The tops of the gears in this pump need to be basically touching the face-plate. And with this seal-induced warping, it may not generate enough pressure as oil temperature increases. Time will tell. As well as this leak, the combustor "lid" so far has not had a gasket, and has been leaking perfectly good air that should be burning fuel and cooling gasses. While I was at it, I cut gaskets for the turbine inlet-combustor outlet coupling, and some of the inner components on the "cool" side of the combustor, where air might leak out past fasteners. I'm hoping these gaskets might improve performance and reduce EGTs, at least a little bit. Finally, I have had issues with the silicone elbow linking the compressor outlet and the combustor inlet. When I run the engine up to 15 PSI, this elbow slides loose of the combustor inlet causing a shutdown and a small hurricane, no matter how tight I got the clamp. I used a crescent wrench to flute the end of the inlet. Hopefully this will keep it in place. Plans for the future are controlling fuel flow by PWM of the fuel pump, which will involve removing the regulator, programming my arduino to drive a simple speed controller (hopefully for the oil pump as well) and removing the fuel pressure regulator. A much simpler system methinks. I'll keep the updates coming until someone tells me to stop! -Feathers
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Post by racket on Jan 21, 2012 0:28:14 GMT -5
Hi Feathers
You need a thicker oil pump cover , any end float in the pump gears will definitely cause pressure problems with hot thin oil.
Yeh , seal her up , even a minor leak will see temperatures climb, lotsa small leaks will make it hard to get usable power out of her .
With the flexible connection between comp and delivery tube , we probably need metal to metal distances of only 1/4" max , with the hose clamped close together , with minimal hose length between clamps as hoses tend to bulge under pressure and this can cause the hose to shrink axially and cause problems , the hose shouldn't have to hold any forces other than radial air pressures.
Cheers John
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Post by Johansson on Jan 21, 2012 4:25:12 GMT -5
Looking good Feathers! I would recommend that you run the oil pump directly from the battery and use a mechanical pressure regulator, we have been struggling with hung up Arduino boards and failing PWM controllers for a couple of years now and I would never trust it for something as vital as the oil pump.
One thing we found is that the afterburner ignition messes with the Arduino board somehow, we have fixed it more or less by working on the grounding and adding diodes here and there. (donĀ“t ask, it is my friend who knows about these things)
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