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Post by racket on Sept 11, 2015 21:11:49 GMT -5
Hi Smithy
Bugger , work has to come first though , I was looking forward to catching up for a chat :-(
Hope you make it to Moss Vale , not too far from your home these days:-)
Cheers John
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Post by smithy1 on Sept 28, 2015 20:29:40 GMT -5
Hi Gents, A bit of an update on the "Beast"...it has been a while since my last update so I must apologize....
Some time back I asked Andy M if he could help me out with some info regarding A/B pipe ideas/setup etc and he has done just that...thanks muchly Andy!!....Long story short, Andy gave me some great advice and the Beast is now singing as it should...I did a 2 day car show over the weekend down at a place called Pambula on the far south coast of NSW..... and over the two days I put ~70 liters of Jet-A1 through the Beast.... John, I have wound up the throttle stop to just shy of 40psig P2, (39.7psig indicated). We were at sea level so the air was quite good and ambient temps were ~20-22C. As luck would have it we also had a spring balance handy thanks to some nice guys at the show who had all sorts of old stationary engines and old machinery etc...we decided to hook the old spring scale up to the back of the Beast and check the static thrust...to my surprise we had an indication of 225lbs-F...I must also mention that the scales were in no way calibrated and were indeed quite old.....so even with a probable 10% error we were still getting on the good side of 200lbs-F..!
Some numbers: Ambient air temp: 20-22C EGT @ idle: ~460c (~23,000 rpm) P2 ~3.5-4 psig EGT @ 39.7 P2: sans A/B = 645C (~78,500 rpm) EGT @ 39.7 P2: with A/B = 728C ~75,600 rpm,(Pretty close to the mark here John..!) I am getting a little rpm droop here on A/B application, but nothing drastic. When A/B is shut off I am seeing a quick rise to ~80,500 rpm, to be expected, but it soon recovers back to ~78,500 rpm. I suspect these figures will vary somewhat with different ambient temps and relative altitudes etc...But she sure is working well now...very happy indeed.
The Afterburner is now hitting nice and hard and as often as I like...the hot streak is working really well too, I'm afraid I have no video as I didn't have my Go-Pro with me....no excuse though...! She lights-off easily and runs up to idle well.... and I'm seeing a peak EGT of ~780-800C during start...not too bad really...I can live with that.
So thanks to John & Andy's help we now have a nicely running A/B system....finally..! I'm planning to experiment with varying amounts of A/B fuel flows....although with a finite amount of oxygen available I suspect I'll get to a point of "more fuel does nothing"..! I dare say the ~200lbs-F I'm seeing is about as close to design thrust as I could ask for.
Cheers, Smithy.
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Post by racket on Sept 28, 2015 21:00:44 GMT -5
Hi Smithy Excellent news Yep, 190 lbs was my original theoretical thrust projection with A/B ................she's right in the ballpark . MMMMMM..........now all you need is a decent stretch of tarmac , I know how well my 2 shaft kart went with only 160 lbs of "thrust" . Your rpm are a tad higher than expected from looking at the comp map at 40 psi P2 , so maybe the turb scroll is allowing the comp to flow a tad towards the choke side of the map , maybe a bit of water injection into the flametube to pad out the "gas " flow and bring rpm back a bit , the reduced flow through the comp should also improve the compression efficiency a bit and with the water injection increasing/restoring mass flow through the turb there should be a tad more pressure energy in the A/B, and/or maybe another psi or so P2 if you still want to use the same rpm as at present ...............heh heh , just some very fine tuning required at most If the A/B is working like Andys , she'll be a noisy bugger , and thirsty at 70 litres for the weekend , I hope the "punters" enjoyed it . Cheers John
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Post by smithy1 on Sept 28, 2015 21:28:52 GMT -5
Hi John, I suspect you're right with the rpm's I'm seeing....maybe the "air" wasn't as good as I though it was...although, some time back Andrew and myself did see some strange rpm numbers IIRC...no matter, as long as I'm not destroying things I'm happy enough, I guess the rpm readings from my cheap-ar$e tacho could be a bit astray but should be close enough for us.
The bearings are still nice and smooth with no evidence of comp or turbine rub, no smoke and no oil usage...That big old GT6041 is sure strong. I doubt whether I'll go the "water injection route though....I like simple...!
The pipe doesn't glow as much as Andy's does, just a mild "cherry" after ~5-10secs of A/B use, so I guess a little more fuel could be put through it. Noisy doesn't describe it...she's nearly big enough to re-arrange one's internal organs...I can feel the "hit" from in front....so I suspect the hit from behind is certainly noticeable..! Some of the people watching were suitably impressed.....even had one woman complain bitterly that I scared her and her daughter with my "infernal banging"....I then told her.."It's essentially an afterburning jet engine, what did you expect?"...she wasn't real happy and scoffed off to tell her horror story to the nearby local police display.... who were only too happy for me to "do it again"...!
I did burn a bit of the local scenery though, there's 2 lots of ~20m of burnt grass on the Pambula Sports ground..it'll take a while for that to grow back methinks.
Cheers, Smithy.
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Post by pitciblackscotland on Sept 28, 2015 22:17:25 GMT -5
Hi Brett, Nice work mate, sound like you are having a good time with this beast keep up the good work mate. Cheers, Mark.
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Post by racket on Sept 29, 2015 0:38:23 GMT -5
Hi Smithy
I've rechecked all the numbers and "corrected" them to Garrett factors , both comp and turb flows as well as rpm corrections and it still looks like the flow should be at ~165 lbs/min -2.75 lbs/sec,the turbine stage is the restricting factor, flow line on the turb map is flatlining at 165 lbs/min at your temps and pressures , the rpm correction only changes things by ~1,000 rpm ,so maybe the P2 g/g is slightly under reading for the rpm you're doing , but everything is well within the ballpark .
Fuel burn rate should be ~1.7 litres/min to the combustor if burning at a reasonable 98% efficiency , the afterburner at 90% burn effic will need ~5.1 litres/min , for a total engine burn rate of 6.8 LPM.
20 metre burn marks sorta indicate she's probably as good as she'll get ..............heh heh , but we always want more ;-)
Excellent results all round.
Cheers John
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Post by smithy1 on Sept 29, 2015 1:26:17 GMT -5
Hi Smithy I've rechecked all the numbers and "corrected" them to Garrett factors , both comp and turb flows as well as rpm corrections and it still looks like the flow should be at ~165 lbs/min -2.75 lbs/sec,the turbine stage is the restricting factor, flow line on the turb map is flatlining at 165 lbs/min at your temps and pressures , the rpm correction only changes things by ~1,000 rpm ,so maybe the P2 g/g is slightly under reading for the rpm you're doing , but everything is well within the ballpark . Fuel burn rate should be ~1.7 litres/min to the combustor if burning at a reasonable 98% efficiency , the afterburner at 90% burn effic will need ~5.1 litres/min , for a total engine burn rate of 6.8 LPM. 20 metre burn marks sorta indicate she's probably as good as she'll get ..............heh heh , but we always want more ;-) Excellent results all round. Cheers John Yeah...thanks for the confirmation John...I'm pretty sure she's doing a fair job of it and trying her best.....I guess not everything can be optimal all the time...so a little "fudge" factoring is always needed I suspect ....I'm very happy with the way she's running anyway....no silly temperatures indicated, rpm's & pressures are all in the ballpark-ish range and she makes a nice "jet" type of noise...who could ask for anything more..?? I might pull the gauges this week and take them to work and see if there's anything amiss and adjust as required. As mentioned earlier, Andrew and I were rather baffled by the rpm readings we were getting compared to the P2's we were seeing some months ago...so there's something not quite on the money.....but....it is a go kart after all...not a passenger carrying aircraft..! We can forgive her for that.. Cheers, Smithy.
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Post by enginewhisperer on Sept 29, 2015 3:26:45 GMT -5
I'm keen for a drive
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Deleted
Joined: January 1970
Posts: 0
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Post by Deleted on Sept 29, 2015 13:25:29 GMT -5
Hi..... glad all is going well, would love to see it working, hope the little info i was able to give you helped
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Post by smithy1 on Sept 29, 2015 14:47:05 GMT -5
Hi Brett, Nice work mate, sound like you are having a good time with this beast keep up the good work mate. Cheers, Mark. Cheers Mark.....Yes, I'm having quite a bit of fun with it, I'm very happy just to be running it, much better than having it sit idle in the shed. My son is actually getting a little "turbine savvy" of late and I might even be able to convince him to get a small turbine project going one day... Cheers, Smithy.
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Post by smithy1 on Sept 29, 2015 14:48:07 GMT -5
Hi..... glad all is going well, would love to see it working, hope the little info i was able to give you helped More than helped Andy....thanks once again... Cheers, Smithy.
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Post by smithy1 on Sept 29, 2015 14:50:06 GMT -5
I'm keen for a drive Me too ....I just need to find somewhere reasonably local to open her up. Cheers, Smithy.
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Post by racket on Sept 29, 2015 20:40:22 GMT -5
Hi Smithy
LOL, I sometimes forget , this is only amateur gas turbines and ballpark is good enough ...............I'm forever the perfectionist , its an unhealthy curse :-(
Cheers John
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Post by smithy1 on Sept 30, 2015 18:45:27 GMT -5
Hi Smithy LOL, I sometimes forget , this is only amateur gas turbines and ballpark is good enough ...............I'm forever the perfectionist , its an unhealthy curse :-( Cheers John Yeah... I used to be anal and worry a lot about the numbers and making sure everything was just so....but not so much these days...the way I see it....if the engine runs, makes all the right noises, feels smooth and is showing reasonable numbers in regards to EGT's, oil pressure and P2's etc...I'm happy. There's just too many variables to worry about with our "amateur" turbines ....I'd rather enjoy running the machine than worrying about all the numbers being perfectly correct. A periodic inspection of critical items is a must though, a lot of bad things can be eliminated through a thorough inspection. I've often found that if it looks bad, sounds bad or feels bad....it probably is...so... as long as the beast looks, feels and sounds good...I'll just enjoy it for what it is. If we keep a keen eye on the important numbers we can usually pick up problems before they become nasty. Cheers, Smithy.
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Post by racket on Sept 30, 2015 21:07:07 GMT -5
Hi Smithy
LOL, you've had more than enough experience to not worry ;-)
Variables, variables,..... I have bad dreams about variables .
Yep, good inspections are a must .
I'm really happy she's finally singing the way she should :-)
Cheers John
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