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Post by racket on Jul 6, 2015 2:23:40 GMT -5
Hi Smithy
23,000 rpm, LOL, .....thats barely spinning around , the extra comp outlet blade angle swept back , compared to our TV94 wheels, must make the difference , also having a vaneless diffuser means never being "off design" , at 23K for my micro engines I'm barely over self sustain , interesting ................I wonder what I'll be able to idle the 12/118 down to , it having a 60 degree exducer angle like the 6041, hopeful something similar .
700C is good , thats ~50 degrees below "design" with everything producing the correct back pressure on the gas producer............still a bit of margin for hot days .
The turb wheel would be good for probably 850 C for a TOT at full noise , but the mass flow through the turb scroll starts to be limited past ~750 C , the scroll A/R is a tad small for really high temps .
I'll be looking forward to those pics to see how the bits are coping and what their heat colouration is to see how well the design is working ...................heh heh , you've probably burnt more kero in the 6041 than I have in all my engines put together :-)
Cheers
John
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Post by smithy1 on Jul 6, 2015 3:55:03 GMT -5
Hi John,
I believe the 6041 will idle quite a bit lower than the 23k too...TBH I think under 20k is extremely possible....but there's no real point in doing that. I have removed the CC and will take it to work in the morning to give it a good looking at...the pipe should be off tomorrow arvo and I'll give the turbine wheel a bit of a look too.
Yeah...I did six engine runs over the weekend, so probably put 40L+ of JET A-1 through it...!
Cheers,
Smithy.
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Post by smithy1 on Jul 6, 2015 17:07:54 GMT -5
Hi John, I've got the CC at work and have taken a few photos for you, as can be seen, it looks ok. There is however some burning of two of the internal evap "J" tubes, it's not bad but I'll need to do something about it soon-ish. Apart from that there's no distortion or cracking evident anywhere, all in all, not too bad. The propane and fuel injection rings are all good with no evidence of heat distress.      Cheers, Smithy. |
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Post by smithy1 on Jul 6, 2015 19:37:47 GMT -5
Hi John,
Thinking outside the box a bit here:
I've been thinking about fitting a Rolls-Royce (Allison) C20B combustion liner into the go-kart, I know the mass flows are not the same but they are reasonably similar, I have access to a recently unserviceable combustion liner and could basically stitch weld part of the lower cone section of the original 6041 CC to the C20B item.... I also have a fuel nozzle and igniter system to go with it, I'm sure I could modify the original outer combustion can to suit or modify the existing one...One thing that may screw me up is the fact that the C20B compressor is capable of producing far more P2 pressure than the 6041....but it can only process the air it receives and if I supply the correct amount of fuel it should be ok-ish. At ground idle the C20B is producing ~31psia (~16.3psig) and flowing ~55lb/hr fuel flow...and this is at ~62% N1 rpm....the 6041 can easily idle much lower than that.
I guess my question is....do you think it's feasible..?? I would appreciate your thoughts...?
Cheers,
Smithy.
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Post by racket on Jul 7, 2015 4:23:58 GMT -5
Hi Smithy
Heh heh , anythings feasible :-)
Actually , after building the engine I felt it would have been easier to have used a single spray nozzle and high pressure fueling than go through making the evaporators and other associated bits .
To get the high fuel pressure ( 500 psi ) I was going to use a 24 volt scooter motor like the one for the kart oilpump , and mount up the 1 cc/rev hydraulic pump I originally used on the TV84 engine , to control the output ( throttle) I intended using the compatible 24V scooter controller .
Making the fuel pump was going to be the biggest job .
Rather than fitting the C20 flametube , have you considered just swapping out the evaporators for a centrally mounted C20 fuel nozzle with some swirl vanes surrounding it that can flow the same ~10% airflow that the evaps do .
A few minutes work with an angle grinder fitted with a thin cutoff blade will see the flametube cap removed ( premark the cap to sidewall orientation for easy replacement)
Remove the evaps and fit a blanking off disc with a threaded boss for the spray nozzle , have the blanking off disc contain the swirl vanes .
If you want to use the C20 FT then its hole area might be a tad small due to the lower cubic feet per second flow from its normally higher pressure ratio , probably ~15% less CFS.
If you were to try using the C20 outer can as well, you might need to have both delivery tubes hooked up to the 6041 comp outlet otherwise there'll be asymmetric air delivery if only one is used which will probably result in some uneven combustion.
I can understand wanting to use the C20 bits , they're beautiful bits of gear ...............LOL, if I'd had them, I'd have tried to use them :-)
Lets throw some ideas back and forth .
Cheers
John
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Post by smithy1 on Jul 7, 2015 15:50:12 GMT -5
Hi John,
I quite like throwing ideas around..I believe we don't need anywhere near 500psi for the C20B fuel nozzle at the flows we'll be needing, I can "calibrate" it to pretty much flow whatever I like, they have internal spring and shims to adjust the flows & pressure requirements. It happily sprays a fine cone pattern at just 40psig and above. In stock form and at 40psig it's only flowing ~15-20PPH. Maximum fuel flow for a C20B is 285PPH @ ~400psig, can't see us needing that much fuel TBH.... plus I can vary the flow/pressure slope via spring and shim adjustment ;-) ...spray angles vary from ~80-110 degrees.
I have a couple of spare Bosch 044 pumps at home, these can easily handle ~100psi at the flows we'll need, even with ~40psi P2 I believe we'll have plenty left over.
I might add that the C20B flame tube "swirl vanes" are quite small and to be honest we could probably get away with just a few directional "slits" in the end cap to accomplish the same thing and keep the same airflow rates. I might take your advice and see what can be done to your original CC to accommodate the C20B fuel nozzle.....or...I could possibly remove the C20B end cap and adapt/fit it to the original flame tube and that would negate a lot of the issues.
As regards the placement of the fuel nozzle, it does indeed fit in the center of the C20B end cap...but it actually just sits there, the thread is in the outer can and the nozzle spray tip outer shroud is essentially a flame tube holder. The igniter could then basically go anywhere, I have a full C20B igniter system sitting at home which is a bonus...and I dare say we might even be able to light-off on liquid fuel...which would be pretty cool.
Lots to think about..
I'm planning on getting a basic gasless Mig welder in the not too distant future so I can at least do some rudimentary welding.
Cheers,
Smithy.
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Post by enginewhisperer on Jul 7, 2015 19:19:55 GMT -5
If you get a welder - get a basic inverter TIG  It'll take a bit more time to learn, but then you can weld thin stainless, etc which is much more useful for turbine engine building! Otherwise if you need anything welded, feel free to bring it to my workshop any time. A cheap gasless MIG is the worst welder option in my opinion. A good quality one is much better - but will cost more than a good TIG and is still much less versatile. |
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Post by smithy1 on Jul 8, 2015 2:19:55 GMT -5
If you get a welder - get a basic inverter TIG It'll take a bit more time to learn, but then you can weld thin stainless, etc which is much more useful for turbine engine building! Otherwise if you need anything welded, feel free to bring it to my workshop any time. A cheap gasless MIG is the worst welder option in my opinion. A good quality one is much better - but will cost more than a good TIG and is still much less versatile. Thanks Andrew...I will take your advice and get a reasonable quality TIG. Might even take you up on the offer to do some welding for me too..! I need to do some decent "thinking" first and get all my ducks in a row before I tackle the combustion chamber on the kart. Cheers, Smithy. |
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Post by racket on Jul 8, 2015 3:52:20 GMT -5
Hi Smithy Yep , get a TIG , I purchased a MIG when I made the FM-1 engine , but have never used it since , a TIG is a much more civilised beast to use , its very much like oxy welding where you just melt things together , I gave my huge TIG away when I moved house and have recently purchased one of these www.ebay.com.au/itm/NEW-ROSSI-Welder-Inverter-TIG-ARC-Plasma-Cutter-Welding-Machine-DC-Portable-/130836607781?pt=LH_DefaultDomain_15&hash=item1e76783325 , does TIG, stick and plasma cutting all in a very lightweight package , good enough for the limited use I'll put it to, just gotta get myself a bottle of argon pretty soon as theres some stainless 12/118 engine bits needing welding together . Had a look at the C20 fuel nozzle you gave me some time back and I can't see too many problems fitting it into the current 6041 flametube once the evaps are removed, just fit a blanking plate inside the "round house" with a tubular extension into the flametube that the fuel nozzle slips into , the metal fuel line will keep it in place , slip the fuel line down through the current fuel/lpg arrangement , no need to make many mods at all :-) The nice wide spray angle of the C20 nozzle will be right at home in that fat flametube Cheers John |
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Post by smithy1 on Jul 8, 2015 14:56:20 GMT -5
Thanks John,
The Tig you link to is pretty much what I'm after too, thanks. Andrew and yourself have given me lots to think about.
Yeah....I might do as you mention and make the C20B fuel nozzle fit in the original 6041 flametube, can't be too difficult I hope, although I might see if I can make it removable from the top of the outer housing ....a job for the near future as I fear the original "J" tubes might not last too long.
As mentioned, I might even be able to make the C20B igniter fit in the system somewhere too, having a liquid fuel start would be a really cool feature, needs lots of energy to work well though, might need to have a small high voltage power supply for it....a 6 cell Li-Po might do the trick methinks, they run to 25.2v on a fresh charge and the ignition exciter will work nicely with that....it even works ok on 12v albeit with a slower rate..
Cheers,
Smithy.
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Post by enginewhisperer on Jul 8, 2015 19:44:26 GMT -5
There are places now that will sell you an argon bottle so you don't have to pay rental. It pays for itself in a couple of years - and you don't have to deal with BOC!
Most people go through a bottle in a year or two - which is around $135 to refill (they do a swap system like the BBQ gas)
There is someone on ebay now who does the refills for $160 including delivery (they pick up your empty one), which makes it a very low fuss setup!
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Post by smithy1 on Jul 8, 2015 20:35:40 GMT -5
There are places now that will sell you an argon bottle so you don't have to pay rental. It pays for itself in a couple of years - and you don't have to deal with BOC! Most people go through a bottle in a year or two - which is around $135 to refill (they do a swap system like the BBQ gas) There is someone on ebay now who does the refills for $160 including delivery (they pick up your empty one), which makes it a very low fuss setup! OK...so for general stainless TIG welding, do you recommend 100% Argon or 98% Argon & 2% CO2...or something else.?? Cheers, Smithy. |
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Post by enginewhisperer on Jul 8, 2015 23:25:21 GMT -5
100% argon for everything |
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Post by pitciblackscotland on Jul 9, 2015 1:04:52 GMT -5
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Post by enginewhisperer on Jul 9, 2015 2:48:56 GMT -5
yep that's the one. I wouldn't buy one of those bottles though, go for a D or E size (E is much better value for refills, but is very heavy to cart around)
That particular one is bottle and gas - the refill on its own is a lot cheaper. E size is $160 including delivery from memory.
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