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Post by enginewhisperer on Jul 17, 2023 21:04:33 GMT -5
I think it's the first time I've seen John jump at the afterburner ignition!
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Post by racket on Jul 17, 2023 21:21:44 GMT -5
Hi Andrew
LOL........I was a tad jumpy , I tried igniting the A/B at 2 bar P2 but it wouldn't , also there wasn't any "smoke "from the A/B so I was a bit concerned , but once I dropped back to 1 bar P2 she lit straight away , a bit too quickly for my liking , and with the whole test stand making a jump at me from the massive sudden increase in thrust , it was unnerving , I'm getting too old for this sorta stress :-(
Cheers John
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rkr2000
New Member
Joined: July 2023
Posts: 1
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Post by rkr2000 on Jul 27, 2023 20:57:42 GMT -5
Hi John,
I've got the rotating assembly of the low pressure turbo from a ford power stroke (high pressure turbo ate a bolt so I don't have both unfortunately). It uses a journal bearing, and I am wanting to make a jet engine out of it. I have seen multiple projects of yours and other members of this forum use brass journal bearings in jet engines and I would like to know how you did it. Specifically, how did you make the housing for the bearing, did you just take the center housing from the turbocharger and cut off all the unnecessary parts? Or did you make the entire housing from scratch?
Thanks, Robert
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Post by racket on Jul 27, 2023 23:25:06 GMT -5
Hi Robert
We machine up a new bearing housing , its not a difficult job especially if you have an original turbo piece to copy the various dimensions/clearances etc from , its probably easier than trying to remove all the bits from the turbo housing and attempt to mount the diffuser and NGV to it , a bespoke shaft tunnel can be configured/designed with their attachment in mind .
There should be pics of building our shaft tunnels in their Build Threads
Cheers John
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Post by racket on Jul 28, 2023 1:45:32 GMT -5
Hi Guys
Test run this afternoon ...............scared the crap out of me :-(
One very hot A/B :-)
Video to follow
Cheers John
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Post by racket on Jul 28, 2023 2:09:45 GMT -5
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Post by racket on Jul 28, 2023 2:22:09 GMT -5
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Post by racket on Jul 28, 2023 2:36:10 GMT -5
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Post by racket on Jul 28, 2023 3:16:17 GMT -5
HI guys At 2:10 in this video , www.youtube.com/watch?v=1YuFKs3nkrQ run it at 25% speed for some interesting P2 and P4t numbers .................I'd better have a look inside, thrust was near 400 lbs :-)
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bigkwaka
Member
Joined: August 2010
Posts: 11
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Post by bigkwaka on Jul 28, 2023 3:20:03 GMT -5
That’s Crazy Racket. You are playing an extreme sport there. I think you’ve hit your thrust mark and then some, before the scale became possessed.
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Post by racket on Jul 28, 2023 4:36:36 GMT -5
Yep , she got out of control for some reason , it was interesting at the time , certainly had me jumping :-)
Lotsa chewing over the numbers tomorrow .................LOL, I'll sleep well tonight .
I think I can sign it off as "done "
Cheers John
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Post by finiteparts on Jul 28, 2023 13:00:34 GMT -5
John,
That is a very interesting behavior. The frequency spectrum waterfall shows that the rotor speed drops and gets very "fuzzy", which maybe suggests it was pushing into some form of instability? The fact that the afterburner inlet total pressure tracks with the P2 seems like it is a whole system effect and not just a compressor surge.
What was happening when this occurred? Were you increasing AB fueling? ...or engine fueling?
- Chris
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Post by finiteparts on Jul 28, 2023 16:21:24 GMT -5
Rewatching I see that the main fuel pegs the gauge, so I guess you cranked up the primary fuel? The AB fuel pressure goes up too, but not as much...maybe responding the the higher duct pressure?
It is interesting that the fuel flow and PR increased but the rotor speed dropped. It sort of suggests you thermally choked the nozzle and lost control of the rotor pressure ratio. If it had been choked at the NGV or rotor, you likely wouldn't have seen the pressure response in the AB duct.
Of course this is speculation since the transient happened so fast and it is hard to determine what is happening from gauges that don't have the frequency response needed to really see the behavior in detail. The videos mention that you upgraded the fuel and AB pump batteries? Can you give details?
Very interesting behavior.
-Chris
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Post by racket on Jul 28, 2023 19:46:05 GMT -5
Hi Chris I don't know what happened :-( I didn't alter the fuel flow , the combustor drain was open , I leave it open all the time just in case . Back on June 24 last year www.youtube.com/watch?v=gYcGfHTbMzk when I registered 357 lbs of thrust with the chinese comp wheel there were "similar " excursions , I had the same 24V on the combustor fuel pump and 12V on the 2 A/B pumps , but I switched the combustor pump back to 12V after that test as the comp bore stretched , in July there was more clipping of the exducer by another 5 degrees before fitting the spare comp wheel and water injection , but my thrust was down by ~80 lbs . I think my ancillories 12V battery , a 75 Amp deep cycle unit, wasn't up to the job of powering everything , hence my change back to 24V for the combustor pump this test . I agree with you about the A/B nozzle thermally choking , by running the Youtube vids at 25% speed the P2 gauge climbed alarmingly , to what looks like ~5 Bar :-( and P4t to ~1.25 Bar , the thrust readings would have been at ~400 lbs taking into account the rolling resistance of the test stand which was a tad uphill , that was before the massive swings which saw every dial going wild at unknown readings . That was one scary testrun at the time , even worse once I viewed the slow motion video , LOL......it took some time for me to get to sleep last night , a bit of an Adrenalin overdose late in the day took some time getting out of the system ..............oh for the days when I knew nothing and cared even less . The front wall of the A/B has a more concave appearance now , but at least no splits . Cheers John
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Post by racket on Jul 28, 2023 20:52:09 GMT -5
Hi Guys Thrust spring balance is a bit worse for wear Cheers John
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