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Post by racket on Dec 9, 2022 0:09:13 GMT -5
Hi Guys Another test today with the surge slot closed , crappy results , very poor comp effic , too close to surge :-( youtu.be/TGspV5qNsxACheers John
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monty
Senior Member
Currently being spanked by mother nature.......
Joined: September 2018
Posts: 400
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Post by monty on Dec 9, 2022 0:29:07 GMT -5
John,
That's a bummer. Do you think it's a diffuser/comp miss match issue, or NGV/turbine exducer too small?
Monty
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Post by racket on Dec 9, 2022 5:07:23 GMT -5
Hi Monty I feel......know , the comp has too much flow capacity for the turb stage ,.... with the surge slot exhausts covered in this test , the comp is flowing right over near surge in very poor efficiency , the poor efficiency needs more turbine power , this in turn needs either more pressure drop or higher temps to achieve , both of which exacerbate the inbalance of flows between comp and turb . Currently its indicating a too small a jet nozzle , even though a 118 mm nozzle is pretty big , but I might need to do a test with an even bigger nozzle to reduce temps , the reduced temps might improve the mass flow through the comp shifting the efficiency up a bit , theres a balance I need to achieve ...............at present this beautiful comp wheel is being severely hindered in performing to its best :-( Another vid of me having problems getting a decent spoolup youtu.be/Bw8zupb7BjwAlthough the test was a bit of a failure , I was able to gather more info , the T2 numbers are sorta aligning , the T2 minus T1 was pretty close to one of the T2 total readings allowing for the 21 deg C ambient temp , whilst the lowest T2 only measured static T2 not total temp in a high speed airflow . Cheers John
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monty
Senior Member
Currently being spanked by mother nature.......
Joined: September 2018
Posts: 400
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Post by monty on Dec 10, 2022 9:57:17 GMT -5
You need this!
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Post by racket on Dec 10, 2022 16:31:53 GMT -5
Hi Monty
LOL.......you're a bad man ;-)
Cheers John
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praendy2203
Veteran Member
Joined: August 2020
Posts: 160
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Post by praendy2203 on Dec 11, 2022 14:18:58 GMT -5
Hi John,
does it mean the ngv, or turbine throat area is again too small?
The comp wheel produces too much air flow to get it squeezed through the aft section and thats why the temps rising?
It could also be a diffuser problem.
You wrote, you have to minimize the wedges 3mm to fit for the new comp wheel tip hight. Your engine sounds in idle like my engine.
Either the bigger radial gap, or the diffuser makes this strange sound.
I also have a 96,5 mm air intake dia for a 95 mm wheel, because of a "mistake". Since I have the Mitsubishi TD 13 wheel and the bigger gap, the engine sounds different to the older Garret wheel with a "normal" 0,2-0,3mm gap.
Investigation time๐
Andy
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Post by racket on Dec 11, 2022 15:38:53 GMT -5
Hi Andy
I've uncovered the surge slot exhaust so that it can work again and improve comp efficiency which in the last test averaged ~65-66% across the entire power range , very poor :-(, the previous test with the surge slot operational saw efficiencies in the 73-75% range .
This new comp was probably running very close to , or even mildly into , surge , especially at idle where there was enough instability to cause the gauges camera mounting to shake .
~25 mm has been cut off the length of the jet nozzle to open it up by ~6mm in diameter, 10% area , to see if that will lower temps back to where they were with the old compressor wheel and allow me to increase the P2 to 3.5 bar
More testing required :-)
Cheers John
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Post by racket on Dec 15, 2022 20:15:13 GMT -5
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Post by racket on Dec 15, 2022 20:37:00 GMT -5
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dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
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Post by dieselguy86 on Dec 15, 2022 21:54:59 GMT -5
John,
Could you machine up a quick bushing that would fit into the inlet and act as a restrictor, limiting the flow into the comp? Maybe it would give you an indication if you are indeed pushing up on surge. Would pre-swirl help?
-joe
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Post by racket on Dec 16, 2022 0:05:12 GMT -5
Hi Joe
Something radical might need to be done , currently its not full blown surge , but that might be due to the wheel design , but theres something else going on , rotary stall?? , I really don't know .
The small gauge at the top of the panel is reading the pressure at the surge slot exhausts , even though the needle starts at 20 kpa , it rises by 10 kPa or ~1.5 psi during engine operation , theres a real blast coming out of the surge slot , probably dumping > 0.5 lbs/sec , the surge slot area is equal to a 2" dia hole .
When I compare my recent results against the old wheel's , the current ones are kinda crap :-(
My T2 readings today are all over the place , the T2 minus T1 numbers are probably being corrupted by "hot" air exiting the surge slot and heating the T1 thermocouple , as during the last test with the slot exhausts blanked off the numbers were all where they should have been in relation to positions etc .
Lotsa thinking required :-( .......I'll do some research on restricting the inlet flow :-)
Cheers John
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Post by racket on Dec 17, 2022 0:56:23 GMT -5
Hi Joe
I've started making up an IGV stator like I used in the 12/118 engine .
I'll do a bit more research to get a better idea of how much deflection I need , but have started making up a jig to help with positioning vanes etc .
My thoughts are that the "high" inducer angle is creating some sort of "problem" due to poor alignment with the ingoing air , maybe a disturbance that is then flowing through the comp wheel ...............I guess I'll find out once I fire her up with the IGV in place :-)
Cheers John
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Post by racket on Dec 18, 2022 19:09:09 GMT -5
Hi Guys IGV starting to come together , slowly making the vanes . A tack weld with the TIG , then silver solder to the central mount , and a silicone bead around each at the bellmouth Cheers John
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praendy2203
Veteran Member
Joined: August 2020
Posts: 160
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Post by praendy2203 on Dec 18, 2022 19:19:12 GMT -5
Hi John,
looks very good๐๐๐
I hope it will help!
Andy
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Post by racket on Dec 18, 2022 21:21:43 GMT -5
Hi Andy
Hopefully it will , sorta like the IGVs in front of an axial comp wheel that get the airflow going in the right direction so that the incidence angle onto the blades is correct , I've got them set at ~45 degrees at the tip .
Heh heh , maybe you need some ;-)
Cheers John
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