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Post by racket on Aug 23, 2023 22:33:29 GMT -5
Hi Mark
LOL.......thats my little brother :-) ...................he got his "teckie"son inlaw to splice things together so all are in the same time frame .
Yep , the the over speed protection works , but it soon reignites , Heh heh , must be some hot bits inside ;-)
Cheers John
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Post by racket on Aug 27, 2023 1:37:55 GMT -5
Hi Guys
All back together and on the trailer ready for a few static tests of pumps etc , I've added another 12V battery to aid with powering the ancillories as the A/B pump wasn't putting out full fuel pressure during the last test .
Hopefully this will be the last test :-)
Cheers John
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Post by racket on Sept 4, 2023 4:09:21 GMT -5
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Post by racket on Sept 4, 2023 4:25:00 GMT -5
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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: 236
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Post by ripp on Sept 4, 2023 6:11:52 GMT -5
Hi John, at first glance the temperature has increased dramatically🤔 otherwise the values have all remained the same 👍 I'm waiting for your analysis thanks Ralph
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Post by racket on Sept 5, 2023 4:14:18 GMT -5
Hi Ralph
I feel theres something wrong with my TOT gauge , its >17 years old .
The T2 minus T1 temperatures are indicating quite good compression efficiencies , so there shouldn't be a need for such high jetpipe temps, or such large variation between thermocouples . .
A problem I have noticed is fuel pressures , both for the engine and afterburner , they are varying between test runs , I feel its a battery problem, even though for this test I added an extra 12V battery to provide more capacity .
I don't think theres much more I can do with what I have currently , theres too many compromises being made after the comp wheel change :-(
Cheers John
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Post by racket on Sept 6, 2023 19:31:42 GMT -5
Hi Ralph
I also just noticed that my "high" TOT reading has changed position on the thermometer , maybe I inadvertently fitted the thermocouples into the opposite positions , but they appear to be marked correctly .
I've swapped the TOT and T2 thermometers around to see if theres a change , also I've adjusted the thermocouples so that they both measure at the same radius in the jetpipe .
Another testrun soon :-)
Cheers John
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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: 236
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Post by ripp on Sept 8, 2023 4:47:20 GMT -5
Hi John, I was watching your runs and thought I would have a go at calculating the rotor speed from the acoustic blade passing frequencies with the spectrum analyzer and some calcs. On your March 22nd test run, with AB duct, but dry, I am getting 61,885 rpm when your P2 gage shows ~ 3.5. Now on your most recent test, with the AB duct,dry, I am getting 60,188 rpms. It is likely that the reduced NGV area reduced the mass flow, thus shifting the compressor op-line over to the left. This would be consistent with the same P2 but reduced rpm, but the IGV and diffuser mods might also be at play. This new compressor appears to be running consistently lower in speed to produce the same PR, since it was installed. I am calculating roughly 3.35 lbm/s to get the 268 lbf at max AB, PR~ 4.5. Is that roughly the number you are getting? I went back and checked some of your older runs, and this is what I collected... 6/9/2022 test: P2 gage ~ 3.0, 64,688 rpm (old compressor impeller) 12/16/2022 test: P2 gage ~ 3.0, 58,662 rpm (new compressor impeller) 12/20/2022 test: P2 gage ~ 3.0, 58,371 rpm ~ 3.5, 61,714 rpm 2/14/2023 test: P2 gage ~ 3.0, 58,328 rpm ~ 3.5, 61,088 rpm 3/4/2023 test: P2 gage ~ 2.0, 51,171 rpm ~ 3.0, 58,885 ~ 3.5, 62,382 3/22/2023 test: No AB (damaged turbine during test) P2 gage ~ 3.0, 58,431 ~ 3.5, 61,885 With AB P2 gage ~ 3.0, 57,711 ~ 3.5, 60,205 6/16/2023 test: Max AB, 60,565 rpm (new turbine) Idle, 30,960 rpm No AB: P2 gage ~ 2.0, 49,714 rpm ~ 3.2, 58,714 rpm ~ 3.5, 60,188 rpm Just thought I would share and hoping that it helps something "click" in your mind about what may be going on. Good luck, Chris Hi Chris, how are things in general and specifically with the 11/127 turbine. If I replace the compressor wheel in an existing system, all dimensions are the same except the tip height is smaller, what happens then? the maximum pressure remains the same but the RPM is lower?, the flow rate and also the thrust is lower? and what about the temperatures of NGV/turbine? John, are you getting the maximum RPM at 3.5 par? (I can't see the tachometer) thanks Ralph
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Post by racket on Sept 8, 2023 16:27:38 GMT -5
Hi Ralph
No tach readings , too difficult with the IGV stator in place
Cheers John
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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: 236
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Post by ripp on Sept 9, 2023 2:23:53 GMT -5
Hi John, By extending the inlet funnel you can perhaps reach two things. a, less TOT temperature and b, space for the tachometer (or probe) In the picture you can see an inlet funnel that supposedly produces a jet of exhaust gas down to -50°C. I've never tried it because my KJ66 only reaches around 620°C at full power Cheers Ralph
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Post by racket on Sept 9, 2023 2:54:50 GMT -5
Hi Ralph
My green manometer read a "vacuum" of 1250 mm of water , that equates to ~2psi of dynamic pressure , so ~10 C degree drop from ambient at the inducer face .
We can only convert a small part of ambient total temp into velocity temperature equivalent , ~10 C degrees is roughly the limit ................LOL, so if ambient is minus 40C then it'll be -50C at the inducer face:-)
Cheers John
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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: 236
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Post by ripp on Sept 9, 2023 12:58:59 GMT -5
Hi John,
What I wanted to say is, the KJ66 runs at full throttle and nozzle at approx. 620°C, with a long inlet funnel up to 50°C cooler, i.e. approx. 570°C It wasn't explained to me why this happens (perhaps less turbulence or stalls?) I bought it but didn't test it, but almost all RC jet engines have a longer inlet funnel.
can you think of anything about that?
thanks Ralph
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Post by racket on Sept 9, 2023 17:17:47 GMT -5
Hi Ralph
Ah , thanks for the clarification :-)
Yep , probably it provides a more axial air flow onto the inducer , the RC engines being on a small physical size but with full sized air flow speeds means very small time frames for things to sort themselves out, the bit of extra time during flow down the longer inlet funnel could provide the difference .
A similar thing occurs when I try using water injection , the time scale for evaporation is too small for it to work effectively compared to full sized engine , I might have 1 millisecond whereas the larger engines would have several milliseconds.
Cheers John
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Post by finiteparts on Sept 10, 2023 13:47:31 GMT -5
Hi Chris, how are things in general and specifically with the 11/127 turbine. If I replace the compressor wheel in an existing system, all dimensions are the same except the tip height is smaller, what happens then? the maximum pressure remains the same but the RPM is lower?, the flow rate and also the thrust is lower? and what about the temperatures of NGV/turbine? John, are you getting the maximum RPM at 3.5 par? (I can't see the tachometer) thanks Ralph I moved this over to the General operability tab ( jetandturbineowners.proboards.com/post/34901/thread ) so as to not hijack John's Thread and make it easier for others to find if needed for future reference. - Chris
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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: 236
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Post by ripp on Sept 14, 2023 1:05:35 GMT -5
Hi Ralph No tach readings , too difficult with the IGV stator in place Cheers John Hi John, Perhaps a speed measurement through the front would be possible. You could make an adapter and insert the tachometer into the sleeve. That would be great if this measurement value were also recorded during a test run. but just a suggestion! thanks Ralph
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