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Post by z28guysteve on Oct 9, 2021 7:16:40 GMT -5
I'll get the measurements soon, but... Very close clearances. It was my first suspect. The turbine to nozzle guide vanes are like a piece of standard notebook paper. So definitely not the turbine side. I think I had .015" from the compressor outer tips to the inside front of the cover. And about .010 around the tips to the inducer. I actually took about .020" off the diffuser wedges, trying to get the cover closer to the compressor.
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Post by jetjeff on Oct 9, 2021 9:03:39 GMT -5
Hi Steve,
.015" gap on the compressor exducer side is quite a lot. Reducing the wedge height is what I would have done. It's kind of tough to really measure the clearance on the blind side of the compressor blades, I've though about using a small ring of modeling clay to check it.
Kurt Schreckling has stated in his book that micro turbines using turbocharger compressors are very sensitive to tolerances in the axial direction.
Regards
Jeff
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ripp
Veteran Member
I'm sorry, I don't speak english, so I torment you (and myself) with a translation program,Sorry
Joined: January 2013
Posts: 230
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Post by ripp on Oct 9, 2021 9:29:19 GMT -5
the clearance at the compressor wheel should be: 0,1 mm
on the turbine wheel: 0,15mm
Ralph
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Post by jetjeff on Oct 9, 2021 11:51:52 GMT -5
Hi Steve,
I forgot to mention that Kamps recommends to get the turbine running reliably on propane before even thinking about liquid fuel. Things can go south in a hurry on liquid fuel especially without a FADEC.
Regards
Jeff
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ripp
Veteran Member
I'm sorry, I don't speak english, so I torment you (and myself) with a translation program,Sorry
Joined: January 2013
Posts: 230
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Post by ripp on Oct 9, 2021 15:40:42 GMT -5
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Post by racket on Oct 9, 2021 16:46:53 GMT -5
Yep , 0.015" is a lot of clearance for such a small wheel , I try for 0.012" with my larger wheels which equates to ~2.5% of tip height , no more than 0.008" for you .
But even with 0.015" clearance it should be possible to get up to a higher P2 .
I check clearances using masking tape , each layer represents ~0.003 - 0.004" , you'll only need a couple of layers , just cut small squares of tape and fold over the exducer , you only need it in 3 or 4 positions , then replace and tighten the front cover and check for free movement of the rotor , if its still free , add an extra layer or two until you get a firmish drag as you rotate it .
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Post by z28guysteve on Oct 9, 2021 17:39:10 GMT -5
Thank you all. I have a new diffuser I designed being machined in China. In the mean time I'll try to close up the front cover clearance some more by filing down the wedges until the desired clearance is achieved. Ill have to get back to everyone next week. I'm an airline pilot and I have a 5 day trip tomorrow.
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Post by z28guysteve on Oct 16, 2021 11:37:39 GMT -5
I was mistaken on the clearance when I quoted it from memory so I re measured it.
Turbine to Nozzle guide Vane is 0.008" inch or 0.203mm Compressor inducer to inlet side clearance is also 0.008" inch or .203mm Compressor exducer face to inlet face clearance after sanding diffuser vanes is .0035" or 0.089mm or two pieces of office clear tape definitely create contact.
Turbine major diameter is 51.181mm Turbine Minor diameter is 32.766mm Case diameter is 83.16mm
Overall I would say clearances are perfect.
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Post by jetjeff on Oct 16, 2021 13:01:12 GMT -5
Hi Steve,
The turbine of radial or axial design (I'm guessing axial)? How big is the compressor at the exducer (an oversized compressor in relation to the turbine can cause overheating problems too)?
As John mentioned before as the size of the rotor shrinks, the tolerances have to be super close, I'd say .004" for compressor and turbine clearance.
Regards
Jeff
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ripp
Veteran Member
I'm sorry, I don't speak english, so I torment you (and myself) with a translation program,Sorry
Joined: January 2013
Posts: 230
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Post by ripp on Oct 16, 2021 14:36:17 GMT -5
The distance at the compressor wheel is now tight, but as long as there is no contact with the housing while the turbine is in operation, it is okay now I see the problem with the combustion chamber and the injection From my point of view, the combustion chamber may have more flow area that means more holes and larger holes in the case of the inner pipe, the number of tertiary holes must be adapted to the number of the outer pipe and must face them The sticks must always be arranged between the tertiary holes and never be blown by cool air. They must glow during operation the tertiary holes should be drilled out to 5 millimeters and 10 3.5 mm holes added beforehand see image Ralph
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Post by z28guysteve on Oct 16, 2021 17:37:01 GMT -5
The vapor tubes are centered between the tertiary holes. Can you dumb down the post a bit. This is my first annular motor so I'm dimwitted with the phraseology
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Post by racket on Oct 16, 2021 18:50:12 GMT -5
Hi
After checking out your video again I notice you are trying to get the engine to run on a rather small propane cylinder , may I suggest using a larger 20 lb/9 kg BBQ cylinder simply to allow sufficient gasious fuel flow to the engine, also make sure there isn't any "safety" device on the cylinder.
Once you have the engine setup for propane , you don't need to be concerned about your vapouriser tubes and fuel injector lengths/orientation as propane will burn .
Cheers John
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Post by z28guysteve on Oct 16, 2021 19:13:06 GMT -5
I just did today I'll try it out next week. New diffuser I think will help though. I haven't made more than 2.5 psi and I know this thing is screaming
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Post by racket on Oct 17, 2021 0:10:05 GMT -5
Hi
The propane will negate any combustion issues , its fast burning and will burn over a wide air/fuel range .
The removal of the jet nozzle will maximise the pressure ratio across the turbine wheel allowing it to power the comp with lower temperatures , your current ones are way too high , a bit of red colour is OK , but orange/yellow is a NO NO .
Which parts of the engine did you make from plans and which parts are as "supplied" ??
A heap of pics will help explain things .
And as Jeff mentioned , the comp wheel dimensions are important , so if you could supply them it'd be appreciated
Cheers John
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Post by z28guysteve on Oct 17, 2021 4:39:03 GMT -5
Every part was supplied except the basket, but numerous people have said the diffuser is very wrong. The wedges equaled the number of comp blades, they have square blunt edges on the wedges, and they don't expand at all just straight passages. I tried on propane and can only get at most 2.5 psi behind the diffuser no matter how fast I spin it. Even with the BBQ tank now
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