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Post by madpatty on Aug 28, 2020 6:13:37 GMT -5
Hi Ralph.
Wow, that engine is exactly similar to my engine.
Were you having any problems running that engine? How was the performance of your engine.
Also by looking at your’s turbine shaft it appears extended...did you increase the shaft length. In my case the curved rear plate of NGVs is eating away precious combustion chamber length/volume.
Regards
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ripp
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Post by ripp on Aug 29, 2020 14:48:35 GMT -5
Hi Patty, yes, both engines are similar because they have a not fully developed combustion chamber. I haven't been able to test the engine yet because the combustion chamber is still missing the evaporator tubes. the phoenix 30.3 engine is probably a prototype www.gtba.co.uk/engine_designs/phoenix.htmI think the curved rear plate of NGV is not so bad. if you change the combustion chamber correctly it should work. Cheers Ralph translate.google.at
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Post by madpatty on Aug 30, 2020 8:19:54 GMT -5
Hi Patty, yes, both engines are similar because they have a not fully developed combustion chamber. I haven't been able to test the engine yet because the combustion chamber is still missing the evaporator tubes. the phoenix 30.3 engine is probably a prototype www.gtba.co.uk/engine_designs/phoenix.htmI think the curved rear plate of NGV is not so bad. if you change the combustion chamber correctly it should work. Cheers Ralph translate.google.at Hi Ralph. I see your engine’s shaft is an extended one. Mine is of the standard length which is already too short. That curved rear wall of NGV further reduces effective overall length of my combustor to just 70mm after which dilution holes start. Combustion intensity is already too high for my combustion chamber. That’s why I decided to change that rear wall also. Cheers.
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Post by racket on Aug 30, 2020 17:15:49 GMT -5
Hi Patty The standard length turbocharger shaft makes for lots of problems , the flametubes length/width ( L/W) ratio isn't conducive to easy combustion and is the reason why all of the commercially produced engines have either extended the shaft or gone to axial turb wheels and bespoke longer shafting that produces a better L/W ratio. My earlier engines using the TV94 comp with the 98mm inducer were able to perform OK with the L/W ratio flametubes available , but my 12/118 engine started having combustion problems due to the larger Width of the annulus, the Length remaining the same as with previous engines using the same turb/shaft. Andy's engine jetandturbineowners.proboards.com/thread/1025/hx-102-255-money-pit with its standard HX82 turb wheel the same as you are using has a workable flametube jetandturbineowners.proboards.com/thread/1025/hx-102-255-money-pit?page=5 so it is possible to get your engine working. Cheers John
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ripp
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Post by ripp on Aug 31, 2020 1:05:13 GMT -5
Hi Patty, Anders has already shown us how his JU 02 turbine work with a fully wedge diffuser. that would be the most promising version for me. the combustion chamber could also be extended to the diffuser. And the lower part removed, so there is enough flow area for CC Inner wall. Then looks like in this picture. (thanks John.) So it could work with a curved rear wall of NGV Cheers Ralph translate.google.at
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Post by ripp on Aug 31, 2020 1:20:39 GMT -5
Hi John,
I really hope that the combustion chamber from Andy's engine proves itself, that would be awesome, so you could leave out the evaporator tubes, there would be more space in the combustion chamber and the production of the combustion chamber would be easier, I hope time will tell whether this version will catch on.
Cheers Ralph
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Post by racket on Aug 31, 2020 4:11:07 GMT -5
Hi Ralph
I think for the larger engines its an option to leave out the vapouriser tubes as the injector syringes used are reasonably strong and the fuel pressure high enough to produce an atomised spray off the "bent tip" , though for smaller engines less injectors could be used so as to use the same injectors and pressures, hopefully one day someone might try it .
Andy's engine appears to work OK even with the very short length of flametube , a "normal" RC micro engine with a longer flametube shouldn't have any problems .
Cheers John
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Post by ripp on Sept 1, 2020 1:08:31 GMT -5
Hi Patty,
please post a few more photos e.g. shaft tunnel length and diameter or diffuser and ball bearing dimensionsers,
Thanks!
Ralph
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Post by madpatty on Sept 1, 2020 22:37:33 GMT -5
Hi Patty, please post a few more photos e.g. shaft tunnel length and diameter or diffuser and ball bearing dimensionsers, Thanks! Ralph translate.google.at Hi Ralph. Here you go- Diffuser is 8 inches in diameter. Cheers.
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Post by ripp on Sept 3, 2020 0:56:44 GMT -5
Hi Patty, thanks for the photos Which combustion chamber design will you choose? Ralph translate.google.at
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Post by madpatty on Sept 3, 2020 3:57:55 GMT -5
Hi Patty, thanks for the photos Which combustion chamber design will you choose? Ralph translate.google.at Hi Ralph. I prefer the one in GTM glass engine. Cheers.
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Post by madpatty on Sept 9, 2020 10:38:49 GMT -5
Hello Jet’o mates.
I had a few questions and doubts regarding the usage of preload in bearings.
I partially understand it’s because you want to keep spinning balls in contact with the races and I also understand the usage of springs in maintaining a consistent force to keep everything in contact.
BUT what are some other ways of setting/maintaining the preload? Why turbochargers with ball bearing cartridges don’t use a preload spring or do they use some other method of maintaining a set preload?
Lastly why can’t we simply preload a bearing by ‘say’ fixing the outer case and axially displacing the inner race by a set value and locking it at that displaced position. Or Vice Versa by fixing the inner race and axially displacing the outer race.
Regards.
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Post by racket on Sept 9, 2020 18:10:50 GMT -5
Hi Patty
Its possible for the axial forces to change direction during operation, that combined with fairly large temperature/expansion changes in our engines require the use of one "sliding" bearing, a fixed preload as in back to back angular contact bearings in machine tool spindles relies on minimal temperature/expansion changes.
Springs are realy the only way we can provide the preload.
Cheers John
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Post by smithy1 on Sept 9, 2020 19:11:52 GMT -5
Wave washers...(which are basically just another form of spring), are a common way to do it in the RC turbines...works really well too. They're able to keep a nice constant load over a wide range of temps whilst still allowing for expansion.
Smithy.
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Post by madpatty on Oct 21, 2020 9:26:45 GMT -5
Hello Fellas. I went ahead and redesigned almost all of this engine into a more accommodating design. Redesigned Diffuser, shaft tunnel, Nozzle guide vanes and all parts are made on CNC this time. Some pics below- Engine spools up much easier with this redesign. I am pretty confident that the startup related combustion problems are gone BUT I haven't tested it beyond idling rpm (7-10 psi P2 approx. 23-30k rpm) as there's another issue that keeps coming up as soon as I try to ramp the engine up to anything above idle. Bearing failure. Repeated Bearing failure. I have wrecked 4 bearings on this engine. The rotor starts vibrating and damn, bearings gone. Rotor seizes. Pictures below- I think I have tried everything and I am out of ideas as to why this can be happening. Front preload, rear preload, shaft balancing. BUT it fails everytime. Feels like one step forward and one step backward sort-a-situation. All Ideas and comments are welcome. Cheers.
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