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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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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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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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Post by jetjeff on Oct 9, 2021 3:07:55 GMT -5
Hi Steve,
What kind of clearance do you have between the turbine wheel to turbine shroud and compressor to front cover plate?
A piece of paper is .004", a 3" x 5" index card is around .009".
Excessive clearance will cause the engine to run very hot (if at all).
Regards
Jeff
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Post by jetjeff on Oct 6, 2021 16:02:19 GMT -5
Hi Steve,
Where do these kits come from (who manufactures them)? The only other website that sold turbines in kit form was JetJoe.
Regards
Jeff
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Post by jetjeff on Sept 20, 2021 15:12:10 GMT -5
Doctorklein,
I think the hardest part of homebuilding a small self contained turbine, is balancing the rotor (with a homemade axial turbine). Static balancing is not nearly accurate enough. The talk of rotor balancing in both the Schreckling book and Kamps book didn't work for me. You need to have a turbocharger rebuilder balance the rotor. I can't speak for PA, but here in Michigan no local rebuilder would balance my rotor, I'm assuming liability issues.
As somebody already mentioned, the thin Inconel turbine wouldn't survive the heat and high speed rotation. Better to machine an axial turbine wheel from thicker material, 1/4".
Regards
Jeff Pittel
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Post by jetjeff on Sept 14, 2021 15:24:48 GMT -5
Hello,
Yes, the reply with the image link, is what I mean. I got a new Mac in 2014 and most of my photo's from this build (2nd Kamp build) is on my old Mac, which won't boot up.
You might seriously consider this style of compressor diffusor. You should have no problems making it on a 3 axis mill.
Regards
Jeff
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Post by jetjeff on Sept 13, 2021 1:31:03 GMT -5
Hi,
I would just continue the wedges to the outer case (like the Kingtech turbine). Much simpler design.
The wedges can be made slightly curved.
Regards
Jeff
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Post by jetjeff on Aug 18, 2021 14:26:27 GMT -5
Hi John,
Looking great so far. Are there any regulations regarding homebuilt power plants in OZ? Any thoughts as to what kind of airframe this will go into (ultralight, BD5-J)?
Regards
Jeff
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Post by jetjeff on Jun 6, 2021 7:26:41 GMT -5
Hi John,
Looks great. In the first pic, what is the smaller hole in the 11:30ish position from the central hole for? Balancing?
Regards
Jeff
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Post by jetjeff on May 28, 2021 13:10:03 GMT -5
I can't see any reason you couldn't do that.
Regards
Jeff
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Post by jetjeff on May 28, 2021 12:18:55 GMT -5
Hello,
Wave washers have been used successfully before. Either spring or wave washer, you just want the bearing to move axially with the thermal expansion of the shaft.
Regards
Jeff
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Post by jetjeff on Apr 15, 2021 2:17:52 GMT -5
Hi Andy,
You have to heat the blade to orange to bend it to 30-35 degrees. I've never made a turbine wheel from Inconel, just stainless. Even with heating, it takes a moderate amount of force to bend it with the claw tool.
If it's not going to power an R/C airplane, have you considered slightly enlarging the Kamps design? Reason being, the rotor becomes slightly more efficient the larger it's made.
Regards
Jeff
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Post by jetjeff on Mar 9, 2021 16:32:27 GMT -5
Hi John,
Have you ever considered pressing the standard turbocharger shaft into an interference fit tube (say with a .125"+ wall thickness), to add several inches to the length of the shaft (and to increase the diameter of the shaft)? You'd have to machine a spigot to accept the compressor.
1/2" quill diameter seems awful small for such a large rotor, plus you could design the engine exactly like your previous designs (with a longer turbine shaft, and longer combustion chamber.
Williams rotor shafts were hollow in design, and even I could make a tubular rotor shaft that works.
Regards
Jeff
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Post by jetjeff on Mar 3, 2021 3:35:16 GMT -5
I started tinkering again with my first build. I'm thinking it's not self sustaining due to the compressor gap being too large at the rear of the compressor. Instead of machine a new front cover, I just bogged up the area with Bondo and recontoured it. It's kind of hard to determine the radius of forward slanting bladed compressors. The compressor is not centered very well, not sure how that happened as everything was turned on a lathe. I enlarged the three front cover holes to try to center the compressor. Regards Jeff
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