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Post by smithy1 on Jan 12, 2022 15:27:34 GMT -5
Hi Guys Thought it was time to have a look at the A/B mounting , so had a play today She's kinda long at ~5 feet - 1500mm Cheers John Only 5ft..?? Ppppffftttt....You can do better than that mate..! Dump type A/B too, very nice. What fuel supply/pump setup are you thinking..?? Am running twin Bosch 044's on mine, no need for a lot of pressure, just volume. Smithy.
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Post by smithy1 on Jan 8, 2022 19:04:03 GMT -5
Which of those two turbines would you go for? The 2.7 sprinter one is variable vane aswell. I genuinley cant find anything decent for my 70mm freepower turbine Ideally you want a turbo without a wastegate or variable guide vanes.....can be hard to come by unless you go big. The Garrett GT6041 is a good example...but it's huge compare to the unit you're using. 106mm comp inducer and 141mm exducer...has a straight turbine housing with no wastegate or guide vanes...makes a really good unit for a turbine engine, free turbine can then be made to suit from a 3rd or 4th stage RR-250 engine.....but again, would be way overkill for what you're after. Here it is fitted to my afterburning go-kart. Smithy.
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Post by smithy1 on Dec 1, 2021 16:19:47 GMT -5
Hi Smithy Yep , very happy with the temps :-) Currently only at ~49,000 87% N1 , 100% will be ~57,000 rpm with a 1,700 ft/sec -520m/s tip speed , and with only a 20 degree backsweep on the exducer it should be enough for a 4:1 PR , heh heh , if not , I can always crank another few thousand out of her ;-) Today I cobbled together an extra fuel pump onto the test stand , my old trusty 1980's Bosch unit , the one I replaced with the clone 044 , I'm hopeful it'll supply the extra fuel required ...............LOL, can't wait for the nice twin 044 unit I've purchased to arrive, ...........will try for another test as soon as the weather clears up . Once I have the 3 Bar of P2 I can concentrate on the A/B Cheers John 3 Bar plus A/B...now that's going to make a decent amount of noise, as you well know my 6041 makes enough noise at ~2.9 bar (~42psi P2) with the A/B. Be prepared to supply plenty of fuel to that A/B Sir. Cheers, Smithy.
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Post by smithy1 on Nov 30, 2021 21:16:53 GMT -5
All looks good John, good temps and pressures, sounds fantastic....a credit to you Sir. She seems much happier in the "hot end" than before...just a couple of licking flames...nothing to worry about.
As Andy says...plenty of room to go to near 3 bar...she'll be pulling some fuel then...plenty of thrust to be had too.
What sort of rpms are we talking at 3 bar P2..?? 65k-ish..??
Cheers, Smithy.
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Post by smithy1 on Nov 16, 2021 23:05:58 GMT -5
Hi Joe Yep , the air/gas gauges are still a bit too bouncy , especially the P4t , could be combustion as one side is a lot hotter than the other :-( But at least the surge indicator string wasn't bouncy :-) Cheers John Hi John.... Awesome work...sounds great and the temps aren't too bad. With the "bouncing gauges", might help to put an adjustable restrictor in the line to help dampen the pulsations...we had similar issues with our 250 C20/30/47/B17 engine test fixtures....some of those pressure gauges bounce around wildly at certain points of the rpm range.....then when the compressor bleed valve closes...it all goes smooth-ish.....not real sure why though...might just be a transitional thing....I fitted some adjustable manual regulators in the lines and we can now read the gauges without going blind. We now also have digital transducers with "smoothing" software which makes things a lot better. Smithy.
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Post by smithy1 on Nov 1, 2021 20:10:56 GMT -5
Hi Mark Yep , and the drain valve :-( Gotta write up and print a SOP to help my decaying brain cells :-) Theres a fueling problem , couldn't get past 2 Bar , the dump valve was closed , so gotta do some fueling checks . Cheers John Sounds awesome John....getting a tad warm at higher P2's, maybe due to the drain valve still being open...... but still a great achievement. My hat is off to you Sir. Ignitor on all the time doesn't matter....it's your "auto re-light" system..! What fuel pump are you using..?? Pressure and guestimated flow rates etc..?? BTW, I'll certainly take the starter off your hands...I still need to get a couple of 3rd and 4th stage RR-250 C20/30 turbine wheels down to you. I may be driving down to Sydney some time during the Xmas break...might be a good opportuninty to catch up if you're home. Smithy.
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Post by smithy1 on Nov 1, 2021 19:59:33 GMT -5
Hi Smithy, Yeah, the GRW bearings in this engine are showing signs of wear (slight rumbling when you spin the rotor), even though total time on these bearings can't be more than 50 or so minutes. Regards Jeff I have a Kingtech K180G and a K45G, both with more than 70hours on them ...on the same bearings....balanced them myself on an old 1980's Schenck CAB 960 balancing machine....(less than 1mg-in). Smooth as a babies bum, (not that I go around feeling babies bums though ). When I put a finger on the housing whilst running it's so smooth you wouldn't think they were running except for the noise. Smithy.
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Post by smithy1 on Oct 27, 2021 23:42:23 GMT -5
Hi Smithy Yep , theres something going on that I'm not understanding , but only a minor distraction :-) It'd be OK with an A/B on it with its BIG nozzle , the full RPM test with the open pipe should give me some number to work from ...............early days yet. Interesting that your temps are changing dramaticaly between dry and wet .........mmmmmm, gotta think on that . Cheers John I wouldn't call it dramatic as such, only 50-60C-ish. Pressure increase within the tail pipe during afterburn is the culprit for the temp increase I suspect. Happens on my little dragster too. I suspect any increase in tailpipe pressure will cause it to some degree and I suspect it tends to try and slow down the eflux speed. Often when I hit the A/B on the little dragster I can hear the rpm drop slightly...RPM Droop!! The ECU of my dragster senses the rpm drop and increases the fuel to compensate...hence the temp increase. As soon as I release the A/B button, the rpm increases slightly, overspeed, the ECU also senses this and then reduces the fuel flow to suit.. The same thing happens to the real jet dragsters when the hit the noisey lever, rpm droop. Speaking of your starter motor, I'm thinking of going the same route as you....what starter motor do you use..?? I'm sure I could make up a similar inlet guide etc to fit the 6041... Smithy.
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Post by smithy1 on Oct 27, 2021 23:19:29 GMT -5
Hi Shanaka, Thank you for your input. The clearance on one side of the compressor is about .004", however on the opposite side it's roughly .019", way too much. This weekend, I'll remove the front cover and add more Bondo or JB weld. Static balancing, isn't any where near accurate enough. I've used the prop balancer too, even machined a hub adapter to go from the 5/16" turbine hole to the 1/8" axel on the prop balancer with < .001" concentricity on the adapter. Problem is if you spin the adapter, you get different results, very frustrating. Regards Jeff Balance needs to be better than 10mg-in otherwise the bearings will not last more than a few minutes and it's possible the engine will just destroy itself. Smithy.
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Post by smithy1 on Oct 25, 2021 23:22:09 GMT -5
Hi Mark LOL .....I was being a bit cheeky fitting the jet nozzle before doing a full RPM run with the open pipe , but the theory recons that 108mm was more than big enough , its 20% bigger than what I used on the 12/118 , ah well , we live and learn :-) Cheers John Excellent work on your first spool-up mate......very enjoyable watching that, looked smooth and easy, sounds awesome...I know what it's like though, your brain is doing 100mph and trying to watch all the guages and need to be an octopus to adjust everything, very stressfull. She's gunna try to turn the world in the other direction when at full noise...there's going to be plenty of thrust to be had. 108mm nozzle on the new engine is too small methinks...I have 110mm on mine, (and only 106mm inducer) and it still gets to ~740C at full noise dry.....just a tad under 800C wet. Maybe as a temporary measure, you could make a bigger nozzle...say 116mm and then use tabs like they did in the old days to tune temps. Smithy.
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Post by smithy1 on Oct 19, 2021 0:16:25 GMT -5
I should have simply bought a jet Joe kit I have a few Jet-Joe kits....whilst they mostly work if built & balanced correctly, they're not the best quality. Their machining and balancing leaves a bit to be desired. I finally settled on Kingtech for my miniature turbines and find them very good and very reliable, not the best available but a good mid-range turbine. The one in my 1/4 scale jet dragster, a K180G is just about bullet proof and I've modified it to take an afterburner system, works brilliantly. I also have a tiny K45G which is equally bullet proof, can do 170,000rpm all day...just normal maintenance is all that is required. Smithy.
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Post by smithy1 on Oct 18, 2021 23:02:04 GMT -5
Hi Smithy Ah yes , thats the thing , thanks for that :-) Nice and "soft" for a better seal . I'll keep persevering with the leafblower for a bit longer, at least until I get the ignition of fuel well sorted , just the usual things to "learn" with a new build . How long does it normally take you to get the GT6041 spooled up ?? .............it'll give me a number to consider , its been so long, I've forgotten how a leafblower start behaves . Cheers John Hi John, Once light-off occurs.. I like to take things slow and steady watching for temp spikes. Plenty of blower helps.....I then chase it up with slow/steady increases in fuel till my idle setting of ~ 130psi fuel pressure, then I just open up the fuel supply tap fully as the throttle valve minimum flow setting now controls the fuel flow..... it usually takes a good 25 seconds or so to achieve a stable idle. I'd rather a slightly slower warm-ish start than a quicker hot one, less thermal stress on the hot bits. I try to limit max temp during start to ~800C...I know the inconel turbine wheel can handle 1000C for very short periods but I'd rather not go there. As you're well aware, the 6041 is a big heavy lump of a rotor to get spinning. Once up to idle she's happy to sit at just ~2-2.5 psi P2. Idle temps are usually in the mid 450C area. I have the max P2 limited via the max throttle stop to 42psi..... but achieving this often depends on the ambient air temp and altitude etc.. You may remember up in the mountains where you used to live.... it just wasn't possible. Cheers, Smithy.
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Post by smithy1 on Oct 5, 2021 20:28:44 GMT -5
Currently trying to find a plastic funnel to seal against the bellmouth, need a ~7-8" mouth on it and flexible enough to conform to the bellmouth for a good seal . Yep , spins easy :-) Cheers John John, I used a rubber plumbing fitting/reducer for the 6041. Bought it from bunnings in the plumbing section....like the ones which the toilets use between the bowl and subfloor pipes etc... much better than a plastic funnel. I found one which fits nicely on the elephant trunk pipe and seals nicely on the bellmouth of the turbo inlet. You can just see it here near the inlet. Smithy.
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Post by smithy1 on Sept 15, 2021 17:27:13 GMT -5
Love your work mate..!
Cheers, Smithy.
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Post by smithy1 on Sept 15, 2021 16:57:19 GMT -5
turbotom Thank you for all the feedback. You're right, the NGV blades have no curvature as shown in the photo, however my team and I plan on bending the fins after initial manufacturing because we have very somewhat limited access to reliable CNC mills and lathes. I did not know the turbine area was too small (I will have a look at that for sure as well as the turbine hub). I'll also have a look at the vaporizor tube position in relation to the combustion chamber holes as well as the spring placement. Just remember the "Kamps" design is very old, possibly getting towards 30 years, their thrust output was minimal and rpm's were quite limited due to many factors ....these miniature turbines have changed immensely over the last 10 years or so and designs of this type are now quite powerful for their size with rpm's approaching 130k+. I have a highly modified Kingtech K180G, it's rated to a nominal 18kg thrust and is only 112mm in diameter, turbine wheel is 66mm, (not much more than in your design). With afterburner it is putting out ~24kg-f ....the bare engine itself weighs quite a bit less than 1kg. www.youtube.com/watch?v=1XqoYhSxKCgSmithy.
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