userscott
Junior Member
Joined: March 2019
Posts: 96
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Post by userscott on Mar 25, 2020 20:43:27 GMT -5
Be careful that the propane flame doesn't heat up your main fuel sprayer , if the propane is only for a pilot light then injection only towards the ignitor rather than across the whole flametube might be a wiser route to go. Looks like your jobs to do are running out fast :-) What about if I bought the propane nozzle just past the kerosene one? The only issue that's obvious is the cone will be interrupted in that area. It would be nice to get her idling on propane, an in ideal world.... PS the entire nozzle assembly and nozzle itself for the main fuel spray are all solid stainless.. The end (of this stage!) is in sight. As soon as she's running happily (assuming she does lol) then I want to get straight onto the after burner...
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Post by racket on Mar 25, 2020 22:32:48 GMT -5
What I did with my TV 84 bike engine was feed the propane into a "tube" surrounding the spray nozzle , the "pure propane" flowed out of the annulus surrounding the spraynozzle , the end of the tube not interupting the fuel spray as it was displaced slightly towards the end cap , the outflowing propane won't ignite until theres airflow mixing with it and that doesn't happen until some distance in front/downstream of the nozzle .
When main fuel is activated it sprays through the propane and its downstream flame for positive ignition , this is a standard oil fired boiler setup
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userscott
Junior Member
Joined: March 2019
Posts: 96
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Post by userscott on Mar 27, 2020 11:55:45 GMT -5
What I did with my TV 84 bike engine was feed the propane into a "tube" surrounding the spray nozzle , the "pure propane" flowed out of the annulus surrounding the spraynozzle , the end of the tube not interupting the fuel spray as it was displaced slightly towards the end cap , the outflowing propane won't ignite until theres airflow mixing with it and that doesn't happen until some distance in front/downstream of the nozzle . When main fuel is activated it sprays through the propane and its downstream flame for positive ignition , this is a standard oil fired boiler setup I think I can visualise that. Do you have any pictures? Tried to search but it eludes me...
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Post by racket on Mar 27, 2020 18:58:46 GMT -5
After having a good look at your flametube and fueling setup I've been having another think on your setup and the "hairs on my butt" aren't happy , that long displacement of the fuel nozzle and a 160 degree sprayer could/will see circulation of flame back towads the flametube cap , 160 degrees is virtually spraying directly towards the FT wall , if this happens then any "tube" surrounding the fuel delivery tube won't be "liquid" cooled once the changeover of fuel is completed and the tube would be subjected to combustion heat and could fail.
The setup I used on the TV84 had a "conventional" flametube with a cap that had airflow surrounding it , the fueling , both kero and propane were "outside" the flametube , whereas yours is deeply inside .
If I was you, I'd serious consider only having a propane pilot light and only having that well away from the liquid fuel delivery bits and definetely not try to run up to idle on propane
Cheers John
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userscott
Junior Member
Joined: March 2019
Posts: 96
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Post by userscott on Mar 27, 2020 21:07:09 GMT -5
Hi John That makes sense. I'll implement those changes. The good news is that by nature of the design, I can easily build up another burner nozzle and move it as close to the cap as possible. I'll find an 80 degree nozzle, and that will allow me to bring it right back towards the cap and still hit the same point on the flame tube. I'll build the propane as a pilot light only. With that in mind, can it simply be a piece of 3.5 mm ID tube with an open end, about an inch or so inside the tube. If so, where will I get away with my spark plug placement in your opinion? A quick question on that actually - I think I messed up on my threaded boss. I'd assumed the spark plug tip only needs to go "just" inside the air gap between the outer and inner parts of the combustion chamber. Laterally, I was going to position it between the primary and secondary holes. Given the placement of the pilot light, perhaps an inch inside the FT, does this sound reasonable? Other jobs done tonight - replaced the pipe work to the gauges on the dash from 1/4 BSP Airline fittings (BSP Parallel) to 1/4 Hydraulic (60 degree cone). The Kerosene had already eaten through my PTFE so I've removed as much as physically possible from the system and it's now 99.99 mechanically sealed or using Dowty washes.
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Post by racket on Mar 27, 2020 22:58:14 GMT -5
Yep an open ended metal tube for the propane so that it simply flows propane past the spark plug thats positioned between Primary and Secondary lines of holes , I wouldn't project the tube very far inside the flametube , just enough to provide some rough direction for the propane, the distance between the tube and plug will allow some mixing of gas and air to form a combustable mixture , you don't want to flood the plug with pure propane . With your plug boss , can you just machine some of it down to 16 mm OD for enough length to allow the plug gap to be inside the FT , there'll hopefully be enough shoulder left on the boss for welding to the outer can, there are also some longer thread plugs available and as we only run low air/gas pressures the plug only needs a few threads to engage for sealing Theres pics of how I did things on the 12/118 jetandturbineowners.proboards.com/thread/612/fat-boy-118-thrust-engine?page=21 part way down the page
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userscott
Junior Member
Joined: March 2019
Posts: 96
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Post by userscott on Mar 28, 2020 9:47:43 GMT -5
Yep an open ended metal tube for the propane so that it simply flows propane past the spark plug thats positioned between Primary and Secondary lines of holes , I wouldn't project the tube very far inside the flametube , just enough to provide some rough direction for the propane, the distance between the tube and plug will allow some mixing of gas and air to form a combustable mixture , you don't want to flood the plug with pure propane . With your plug boss , can you just machine some of it down to 16 mm OD for enough length to allow the plug gap to be inside the FT , there'll hopefully be enough shoulder left on the boss for welding to the outer can, there are also some longer thread plugs available and as we only run low air/gas pressures the plug only needs a few threads to engage for sealing Theres pics of how I did things on the 12/118 jetandturbineowners.proboards.com/thread/612/fat-boy-118-thrust-engine?page=21 part way down the page That makes perfect sense, I'll have a go on that today. Daft question, perhaps, but I presume it's "ok" to drill another hole in the flame tube to allow it to protrude through? I'm off to go and turn the shoulders down on the boss and get it glued on!
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Post by racket on Mar 28, 2020 16:38:19 GMT -5
Yep , perfectly OK to add another hole in the FT , we don't need to be pedantic about the holes, both area and placement, a few percent this way or that isn't a problem as very few of us can be certain of all flow parameters from the comp.
Just be mindful of allowing for the differential axial expansion of the flametube in relation to the outer can with the hole size for the plug to protrude through , we don't want too big a hole as excess air will flow through it and blow the propane away from the spark
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userscott
Junior Member
Joined: March 2019
Posts: 96
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Post by userscott on Mar 28, 2020 20:12:00 GMT -5
Yep , perfectly OK to add another hole in the FT , we don't need to be pedantic about the holes, both area and placement, a few percent this way or that isn't a problem as very few of us can be certain of all flow parameters from the comp. Just be mindful of allowing for the differential axial expansion of the flametube in relation to the outer can with the hole size for the plug to protrude through , we don't want too big a hole as excess air will flow through it and blow the propane away from the spark Thanks John. I've done exactly that, I turned the boss down to 18 mm, sunk it into the CC and it protrudes through a hole with a small amount of clearance, with just the tip of the plug inside the FT. I got the propane pilot tube installed, and it sits about 1/2 or more back from the spray nozzle. I'll order an 80 degree nozzle and make up a new internal pipe and boss for it to solve our earlier discussion about the 160 degree spray, but I'll have to import this from the USA so I think I'll fire her up on the current system at some point shortly... Sadly I forgot pics of the insides but I'll get some tomorrow..
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Post by racket on Mar 28, 2020 22:18:16 GMT -5
Yep , fire her up as is , everything might work just fine :-)
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userscott
Junior Member
Joined: March 2019
Posts: 96
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Post by userscott on Mar 29, 2020 10:09:03 GMT -5
I can't quite believe we are at this stage, considering where we were at Page 1 of this thread. I'll get the last few bits updated and then have a go... I might have one or two more updates before we fire her up, but christ, we are here now.
Thank you in particular John, for your contributions both in this thread and others which have been quite literally invaluable in building her.
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Post by racket on Mar 29, 2020 16:47:16 GMT -5
I'll be looking forward to seeing her fire up :-)
Try a few ignition tests of the propane first to get that sorted before attempting a full spoolup , you might need to fiddle with just how much propane you need to inject to get a reliable ignition , remember to purge the combustor between attempts ................LOL, I couldn't workout why subsequent early attempts failed until I realise I'd used up all the oxygen on the previous one :-(
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on Mar 30, 2020 4:44:04 GMT -5
Well done Scott, the kart is looking great. Very quick progress, and I am looking forward to the fire up videos! With my similar sized turbo, I fired up on propane with a 4 bar regulator (set to around 2.5/3bar). Increase gradually whilst you feed air to the turbo. That was with a 4mm ID copper tube as the propane injector initially. Now i moved to an injector like this: Which should provide 3 flame jets targeted at the kerosene injector and one axial targeted at the spark plug. Cheers Scott
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userscott
Junior Member
Joined: March 2019
Posts: 96
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Post by userscott on Mar 30, 2020 15:21:36 GMT -5
I'm pleased to say, she runs...! The sparking system I made is pants, lit it with a MAPP blow torch, but other than that.... she's fine. Nozzle temps between 250 and 320 degrees typically, everything else quite low. Turbine inlet temp around the 200 mark. Compressor outlet sat around 60 degrees maximum. Very, very happy....... *edit* - I've fixed the wiring issues with the coil and it definitely works significantly better now!! I know this because it nearly blew my arm off!
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Post by enginewhisperer on Mar 30, 2020 17:40:49 GMT -5
that's a pretty painless first start up! It looks like you could have kept the blower on slightly longer, but hard to tell on a video. Pretty keen to see this thing rolling
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