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Post by wannabebuilderuk on Apr 7, 2024 11:38:32 GMT -5
Well after spending an half an hour rewiring in the new buck converter to fix the gauge issue and an hour trying to get the spark plug working due to a bad ground and the flame tube being slightly too far back meaning no fuel went to the plug she started up, little bit hot up to 660ish but that was because I momentarily turned up the fuel as blower was slowing but once running dropped down to 350-450°c between idle and full throttle. So my fear is true and it is compressor surge as you can see the string moving each time it stutters but at least I now know it's that so can figure out how to fix it.  www.instagram.com/reel/C5d4QugMtvk/?igsh=MWUxcHhuaXZ5Z3drNQ== |
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Post by racket on Apr 7, 2024 16:49:16 GMT -5
Well , thats the strangest thing :-(
With such low temperatures you shouldn't get surge unless theres a restriction somewhere .
LOL................I once left a rag inside my TV84s delivery air tube that had me scratching my head for quite a while trying to workout why the engine wouldn't work , this is just as perplexing :-(
Could you collect some data on when the string bounces , its a bit hard seeing the numbers on the video .
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richardm
Senior Member
Joined: June 2022
Posts: 411
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Post by richardm on Apr 7, 2024 17:04:38 GMT -5
Does'nt 450° C at full throttle seem a bit low? Personally I m a little suspicious about that ..Assuming the thermocouple at the right placement , did you cross checyour thermocouple/ gauge against a known reliable instrument?
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Post by wannabebuilderuk on Apr 7, 2024 20:05:25 GMT -5
Well , thats the strangest thing :-( With such low temperatures you shouldn't get surge unless theres a restriction somewhere . LOL................I once left a rag inside my TV84s delivery air tube that had me scratching my head for quite a while trying to workout why the engine wouldn't work , this is just as perplexing :-( Could you collect some data on when the string bounces , its a bit hard seeing the numbers on the video . There's no obvious pattern to it, sometimes it surges on full throttle sometimes it doesn't, sometimes it surges at idle and others it doesn't. It's quite bizarre... Might have to put a couple more holes in the 2nd/3rd stages to see if it improves, couple 10mm holes spaced between existing and if nothing changes I can just patch them up. If there's too much back pressure from gas expansion and flame tube then reducing the restriction might help. I'll see if I can get better footage, just want to fix this before it damages the turbo |
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Post by wannabebuilderuk on Apr 7, 2024 20:15:09 GMT -5
My original hole calculations below for 85mm inlet, if I add 6 10mm holes by the 3rd zone thats an extra 471mm2 which bumps the inlet area to equal an 88mm comp.  Perhaps my compressor is more efficient than expected or not but whatever it is something is causing it to produce too much air to swallow so need to do some investigating 😁 |
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Post by racket on Apr 7, 2024 20:39:39 GMT -5
If surge is intermittent and at all rpm I don't see it being the turbo configuration , the TV81 map is a bit skinny at higher PRs but at say 2:1 PR it goes from ~37 lbs/min Corrected flow to 85 lbs/min which is quite acceptable .
What fuel are you using ??
Is your combustor drain valve open??
Is there fuel exiting the drain ?
I'm trying to determine if theres fuel possibly puddling and suddenly flashing off and causing a momentary thermal choking of the turbine , ..........its got me puzzled :-(.
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Post by racket on Apr 7, 2024 20:57:16 GMT -5
If you're running at surge , then the flow is less than design , so your design hole area is now relatively oversized, adding more holes will potentially make the situation worse .
I've had another look at your flametube and really can't see any problems .
Is there any indications of where combustion is occurring ??
Generally the stainless will provide some "colour" variations that can provide clues .
The TV81 is an old design like my TV84 was but even when I was running an undersized turb stage in the very early days , it didn't surge until I fitted the jet nozzle and increased temps .
My undersized turb wheel was 97/86 mm with 15 mm inducer tip height , , I tried 1.08 and 1.39 A/R scrolls , the 1.08 was too small , but the 1.39 was OK without the nozzle .
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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: 237
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Post by ripp on Apr 8, 2024 1:20:38 GMT -5
" Might have to put a couple more holes in the 2nd/3rd stages to see if it improves, couple 10mm holes spaced between existing and if nothing changes I can just patch them up. If there's too much back pressure from gas expansion and flame tube then reducing the restriction might help. I'll see if I can get better footage, just want to fix this before it damages the turbo[/quote]" With a "Kamps turbine" I also made a few attempts with a metal ring around the combustion chamber,easy to make. But I realized that the original plan worked well.  Ralph |
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Post by wannabebuilderuk on Apr 8, 2024 3:14:21 GMT -5
If surge is intermittent and at all rpm I don't see it being the turbo configuration , the TV81 map is a bit skinny at higher PRs but at say 2:1 PR it goes from ~37 lbs/min Corrected flow to 85 lbs/min which is quite acceptable . What fuel are you using ?? Is your combustor drain valve open?? Is there fuel exiting the drain ? I'm trying to determine if theres fuel possibly puddling and suddenly flashing off and causing a momentary thermal choking of the turbine , ..........its got me puzzled :-(. Yea I have the drain open till it's running and there's just air coming out, running it on kerosene currently. It doesn't appear to make a difference having the drain open when running as still surges. I don't think it's fuel puddling since I'm running such high pressure the atomization is so good I doubt it gets a chance before burning. It appears to be quite uniform, the flame tube is a nice straw colour that's fairly all over with no obvious random hot spots to indicate issues which is odd. |
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Post by racket on Apr 8, 2024 3:50:50 GMT -5
LOL............back to the drawing board :-(
Could you post some closeup pics of the air delivery system to the combustor .
There is one other thing ...............the turbos heritage ............any chance theres something wrong inside ??
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jetric
Veteran Member
Joined: December 2014
Posts: 147 
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Post by jetric on Apr 8, 2024 7:04:19 GMT -5
It's simple, just run the engine on propane to see if you've got a combustion issue as propane is a more forgiving fuel with a wider air/fuel ratio than kero, then you'll know where to concentrate your efforts. I don't like the look of those two rows of hundreds of tiny holes in your primary zone, all they will be doing is film cooling and not aiding to the combustion in the primary zone. Richard S. Well , thats the strangest thing :-( With such low temperatures you shouldn't get surge unless theres a restriction somewhere . LOL................I once left a rag inside my TV84s delivery air tube that had me scratching my head for quite a while trying to workout why the engine wouldn't work , this is just as perplexing :-( Could you collect some data on when the string bounces , its a bit hard seeing the numbers on the video . There's no obvious pattern to it, sometimes it surges on full throttle sometimes it doesn't, sometimes it surges at idle and others it doesn't. It's quite bizarre... Might have to put a couple more holes in the 2nd/3rd stages to see if it improves, couple 10mm holes spaced between existing and if nothing changes I can just patch them up. If there's too much back pressure from gas expansion and flame tube then reducing the restriction might help. I'll see if I can get better footage, just want to fix this before it damages the turbo |
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Post by wannabebuilderuk on Apr 8, 2024 9:30:57 GMT -5
LOL............back to the drawing board :-( Could you post some closeup pics of the air delivery system to the combustor . There is one other thing ...............the turbos heritage ............any chance theres something wrong inside ?? The turbo was basically unused as guy said low hours plus it basically had no carbon buildup in turbine housing and paint looked fresh/minimal heat, I think the turbo is fine and not sure there could be anything wrong with it. You can see pics of the lobster claw on page 14, fairly wide with minimal swirl so should slow the airflow down going in. jetric the row of small holes is a total of 54 cooling holes with area taken from primary zone area as I wanted to make sure it wouldn't get too hot in the primary zone and they seem to do the trick so not sure they'd be causing any issues. I'll give the propane idea a think, might not be enough to get it to even idle and I'll have to figure out how to supply it since can't use existing nozzle.  |
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