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Post by madpatty on Feb 19, 2021 19:34:59 GMT -5
Patty, what is the current squeeze film damper configuration? Inquiring minds want to know. Thanks, Ron Hi Ron. I am using an unsealed ended squeeze film damper much like what is used in Ball Bearing turbochargers. Regards.
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Post by turboron on Feb 19, 2021 21:06:27 GMT -5
Patty, thanks. Great to see a successful development program.
Thanks again, Ron
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Post by madpatty on Feb 22, 2021 12:19:10 GMT -5
Hi Guys.
Plan was to order some right sized SiN balls so that I can make hybrid ceramic ball bearings of my own and then using those to try and make a full power run.
BUT obviously I couldn’t wait for the SiN balls to arrive so went ahead and made some “full complement steel ball” bearings to try and run the engine upto 50k rpm.
It was a risky territory for steel balls. BUT test run was successful and engine disassembly after the test run showed the bearings without any stress/heat marks and running smoothly as new.
Video below-
Regards. Patty
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Post by wannabebuilderuk on Feb 22, 2021 18:01:07 GMT -5
BUT obviously I couldn’t wait for the SiN balls to arrive Living up to your name and risking it
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Post by racket on Feb 22, 2021 19:07:14 GMT -5
Hi Patty Another few step further along the development road , great news :-) 60,000 for next run ?? Now that you can be a bit more confident of the engine not destroying its bearings in seconds, please try and fit a bellmouth on your comp housing inlet as you are probably experiencing a vena contracta at present en.wikipedia.org/wiki/Vena_contracta#:~:text=Vena%20contracta%20is%20the%20point,cross%20section%20area%20is%20minimum. A vena contracta will be affecting the engine performance making it run hotter than necessary . Also a bellmouth makes it easier to seal the blowers "funnel" against , nudge nudge ;-) Can't wait to hear her on full throttle, keep persevering , not far to go now :-) . Cheers John
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Post by madpatty on Feb 24, 2021 21:43:03 GMT -5
Hi Guys.
Testing Update. Took the engine up to 60000 rpm on my homemade steel ball full complement bearings without any problems.
This thing makes so much noise and rumble that it gets so difficult to keep ramping it up without being afraid of all the power this thing is making.
My white paint from one of the compressor blades flew off at higher rpm so couldn’t go higher in rpm without proper rpm reading.
Next step is to improve the rpm measurement technique and attempt the last 10% milestone.
Regards. Patty
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Post by racket on Feb 24, 2021 22:26:38 GMT -5
Hi Patty
Yep , once we get up around that 100mm inducer size the engine starts to become a serious turbine with hundreds of horsepower being developed and consumed within the engine and not much less going out through the jetnozzle ...... stay brave :-)
The next 10% is where the real power is produced ..............enjoy .
Cheers John
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Post by finiteparts on Feb 27, 2021 17:24:55 GMT -5
Congrats on the success! Glad to see your perseverance and effort paying off.
- Chris
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Post by madpatty on Jul 6, 2021 10:22:23 GMT -5
Hello Gents. Out of curiosity I was reading the literature available and playing around with possible compressor diffuser vane designs and had this question came lingering up in my mind. Why can’t we design something like this- Sorry for the crapy drawing but this gives the idea. The flow at the diffuser outlet has significant swirl component and follows the path shown by yellow line and we need to get rid of that swirl somehow. Why can’t we modify the shape of the vanes(shown by green colour) so that the swirl gets reduced at the diffuser outlet (new air path shown in red). Am I missing something? BUT I have yet to see a diffuser with these shaped vanes. I know the axial vanes do this but this way we can get away without them this reducing the overall thickness of the diffuser especially for engines with already restricted lengths due to standard turbo shafts. Regards. Patty
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Post by turboron on Jul 6, 2021 17:01:42 GMT -5
Patty, my guess is that your suggest vane shape could cause flow separation and high losses in the vane passages. You need to run a CFD program to determine the velocity ratio of the pressure side to the suction side. The ratio should not exceed 1.3 as I recall.
Thanks, Ron
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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 Jul 7, 2021 1:03:00 GMT -5
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Post by madpatty on Jul 19, 2021 18:46:11 GMT -5
Hi racket. Continuing the axial vs radial turbine discussion here. I just rechecked my calculations and found I did use 80% as overall stage efficiency for axial wheel as wheel as well. Some preliminary calculations for a 99Kg thrust engine showed it needs a larger ~150-160mm turbine inducer with a much steep 28 degrees of NGV angle and atleast 130mm of turbine exducer. Are these similar to what you are seeing with your manned aircraft engine Whereas commercially available engines in this category are available to get 100kg thrust out with just ~140-145mm turbine wheels, which is quite impressive. Thanks.
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Post by racket on Jul 19, 2021 19:21:25 GMT -5
Hi Patty You've got to look at comparing radial exducer diameters against axial wheel diameters. My TV84 turbo based engine with a 96 mm exducer produced 50 kgs of thrust If you check my numbers for the 12/118 engine imgbb.com/3CgnVKX the turb effic is pretty good to allow 0.9 Bar of P4t from only a 3.7 :1 comp pressure ratio . Radial turbines will always be bigger at the inducer , though it is possible to have it the same diameter as the exducer but at lowered efficiency, than a comparable axial wheel , but if we only use exducer diameters then things look better My 12/128 engine with its ~126.4 mm exducer should produce 100 kgs of thrust , inducer 149.6 mm , NGV vanes at 26 degrees and 23.5 mm wide ( 22mm inducer tip plus clearances) Cheers John
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Post by madpatty on Aug 25, 2021 14:56:53 GMT -5
Hi All. So this happened when I tested my engine last. I saw a small pin hole crack in the turbine inducer after I disassembled the engine. Also the turbine inducer tips have “grown” radially by atleast 2 mm as I had a hard time pulling the turbine out of the NGV top plate. I don’t know if it was there before or it’s a result of creep. The turbine wasn’t even run to full rpm, max. Turbine tip speed was about 1450ft/s and temperatures were surely not high. I have seen much worse colours on turbine wheel at much higher temperature. Has anyone seen this before, or maybe it was just a bad quality wheel. Regards. Patty
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Post by racket on Aug 25, 2021 16:15:00 GMT -5
Hi Patty
If there was a bearing failure the resulting gyrations will result in extra tensile loads being placed on the blades above the usual ones from temps and rpm , it might have exacerbated an already "weak spot" in the wheel .
I've had a wheel "expand" during a bearing failure and had to cut the tips off the wheel with the oxy torch so as to disassemble the engine
Cheers John
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