ordonezs
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Joined: November 2020
Posts: 19
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Post by ordonezs on Nov 6, 2020 22:46:18 GMT -5
Anyone know some good cleaning tricks? This thing is covered with burnt oil, soot and sludge in every crevice. Edit: What are good cleaning chemicals to use on the hot end? Can I use WD-40?
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ordonezs
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https://youtu.be/hCHDC_XksKY
Joined: November 2020
Posts: 19
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Post by ordonezs on Nov 8, 2020 0:01:31 GMT -5
Thanks for the construction tips, John. Spooled it up this morning and it runs beautifully!
Some test notes:
Was tremendously hard to start. Flame doesn't keep as well as previous nozzle design, especially when adding air to ramp up. My previous startup method (using old axial nozzle) was to use the glowplug to light a pilot flame with no added airflow and increase fuel pressure to the upper limit before the mixture becomes too rich. I'd then be able to spool up the engine with a blower without even touching the fuel pressure - the upper rich limit without air was still above the lower lean limit with full blower. However, the engine would need a bit more power to self-sustain so I'd finish startup by bringing fuel pressure up the last bit.
With the new nozzle design, the mixture range seems to be much more narrow. To get the engine to start, I had to windmill the compressor about as slow as I could get it to turn. I would then try to get a pilot light with the glow plug, which would usually take several tries of quickly opening the fuel line. After making it pop maybe a dozen times, I was able to get it to stay on and slowly increase air and fuel. Even then, the fuel range was so narrow I lost the flame a few times and had to start over. Finally, I was able to catch a flame and walk it all the way up to self-sustaining power.
I think one of the reasons for this difficult startup behavior is that the flow rate through the nozzle is much higher than previously. I'm using a variable 30psi propane regulator, and even with the valve all the way open the nozzle will only produce 3psi or so back pressure. It's difficult to keep the nozzle back pressure above the P2 combustion chamber pressure as the engine spools up, and if the fuel pressure gets too low or drops below P2 the fuel flow stops and the flame is lost. The engine has to spool up slowly so the fuel line back pressure can slowly increase as the propane tank meets demand. It's also easy to run the flame tube too rich at low air flow and snuff out the flame.
Once running, the engine works great. I throttled it from about 2.5psi to 9psi P2 boost, it seemed to run best around 7.5psi. I didn't push the extremes of this range - not sure how much higher I could safely push it and the turbine begins glowing a dull red under 3.5psi. Must not have enough cooling airflow. There is still a small amount of smoke that looks like it's coming from the turbo's oil inlet. Ran the engine for over 5 minutes and I feel it would be fine running longer.
One last thing: the oil coming from the turbo was frothy and occasionally smoky. The oil temperature was never that high, so I suspect the cause is air flowing into the turbo's bearings. I'm confused how this would happen, as I was running at 40psi oil pressure and the highest boost pressure I ever had was ~9psi.
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Post by sauerkraut on Nov 8, 2020 0:11:24 GMT -5
Turbo's have piston ring seals. The center housing is not completely filled with oil, if it was it could spill out of the top gap in the piston ring in great volume. This means there is nothing preventing air from getting in thru this gap and mixing with the oil as it drains from the bearings. It is completely normal and nothing to worry about. The smoke is from the air itself, no biggie.
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ordonezs
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Post by ordonezs on Nov 8, 2020 0:23:31 GMT -5
Thought so. I saw smoke venting out from the oil reservoir but my IR gun showed it at room temp. Figured it was carried by the bubbles in the frothy oil. Thanks for clearing that up!
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Post by racket on Nov 8, 2020 0:53:20 GMT -5
Hi Sam
Congratulations :-)
Idle with a turbo based engine is best kept at ~5 psi P2 , below that, the component efficiencies drop off and we need to compensate with more fuel and hotter temps, your turbine colour is a lot healthier , try to keep it to a dullish red , no orange or yellow please .
Throw the regulator away and just use the cylinder valve , regulators never work for us , their flow rates are too small .
The fact that you only have 4 injection holes means there'll be segments of the flametube cross section that won't have fuel in it , we need at least six injection holes .
Have you reduced the flametube hole areas yet ?? without the correct hole areas the combustion becomes troublesome
As for the air/smoke from the oil tank , quite normal , we all have it .
What position is the variable NGV set at currently ??
All engines requires us to workout a spoolup method , they have diffent needs , no two engines seem to be the same , all part of the process .
Cheers John
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ordonezs
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Post by ordonezs on Nov 8, 2020 1:20:46 GMT -5
John,
Is dullish red the max tolerable temp or the optimal temp? Running at 7.5psi the turbine blades don't even glow at all, if that's preferrable.
Would have done that but I couldn't find an ACME fitting to hose without a regulator! They don't sell those at Home Depot lol. Would I have to splice my own tube?
My plan was to block some holes with SS hose clamps but they didn't fit inside the combustor shell. I got some thin sheet steel to wrap one row of primaries and crop the secondary/tertiary holes, but I'm not sure how to mount it. I ran the test today with the original flame tube - that probably added to startup difficulty.
NGV was set to a little bit less than open. Wasn't able to get it to start at half way, after nearly half an hour of fidgeting with everything I got the best results at about 80% open.
Sam
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Post by racket on Nov 8, 2020 1:42:01 GMT -5
Hi Sam
Dullish red is OK for a max temp , but you can run it without any colour , but for max power output we need to have colour.
You'll need to fix the flametube hole areas otherwise the engine will never run well, you'll continue to have start problems.
You need your NGV vanes to be set at ~30 degrees above the tangent , that provides both rotary gas velocity to power the comp, plus a smaller amount of radial velocity to get the gases into the wheel , everything needs to be "tuned" if you want it to run properly, its easy to just make some noise and flames , but attention to detail is required if you want it to perform , its just a case of doing the basics .
Cheers John
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ordonezs
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https://youtu.be/hCHDC_XksKY
Joined: November 2020
Posts: 19
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Post by ordonezs on Nov 8, 2020 2:21:41 GMT -5
John,
I'll find a way to wrap this steel sheet around some of the holes and see if I can get it to stay. Will also revisit the vanes setting on my next test.
One last question for now - where do your source your unregulated propane hose? I've not seen them at any hardware store I've been to.
Thanks for helping me get this running. Excited to get everything dialed in!
Sam
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Post by racket on Nov 8, 2020 3:29:01 GMT -5
Hi Sam
Use some 1/4" copper pipe and appropriate fittings to hook up the cylinder to the injector , don't use "rubber" hose anywhere near the engine
Cheers John
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pabloa25
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Joined: March 2021
Posts: 1
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Post by pabloa25 on Mar 23, 2021 9:50:11 GMT -5
Hi Sam Use some 1/4" copper pipe and appropriate fittings to hook up the cylinder to the injector , don't use "rubber" hose anywhere near the engine Cheers John I am using stainless pipe to connect my cylinder to my injector but I still have not managed to find a way to connect and ACME fitting to a cylinder without a regulator. Any advice on where I can get a hose without a regulator? Best regards, Pablo
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Post by racket on Mar 23, 2021 18:30:34 GMT -5
Hi Pablo
Try an engineering supplier.
Cheers John
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Post by turboron on Mar 25, 2021 7:02:50 GMT -5
pabloa25, propane(LPG) and Barbeque equipment suppliers have many adapters that you can use. I use a ACME to 1/4" NPT male adapter.
Thanks, Ron
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ordonezs
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https://youtu.be/hCHDC_XksKY
Joined: November 2020
Posts: 19
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Post by ordonezs on Nov 25, 2021 18:28:46 GMT -5
Hi all, Quick life update: I've put down the jet engine for a minute since I've moved from home to build rockets in California! Currently planning what work I want to get in during my next visit home this winter. My primary goals are to improve safety and maximize coolness. I don't plan to develop this engine to power anything so performance factors like thrust and efficiency are not priorities, however I do want it to be loud and cool to watch and most importantly safe to show off. The open safety work I am tracking is to replace the fuel and oil hoses with copper tube per John's suggestion. I have already tuned the turbine vanes to the 30 degrees from tangent also suggested in this thread. I have been running the engine with the oversized flame tube holes with it being easy to start and run at 4-8psi boost. Is there a safety reason to prioritize fixing the flame tube area? If the only concerns are performance/ease of use, then I don't see it as a top priority but feel free to check me here. Another update, I am working on a blog on my website which I should be releasing soon to document my build story! I will post it here when live. Lastly, a few links to share: 1) Here's a video of the most recent time I ran the engine with some friends, using my girlfriend's car battery to power the electrical system (oil pump, radiator fan and spark plug). We took turns starting it up: www.youtube.com/watch?v=DSsSuwEiAxM2) Demo and walkthrough of the engine. I'm sure there's a laundry list of safety items I could improve and I WANT TO HEAR THEM lol: www.youtube.com/watch?v=PHr3xTvaTlQ
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Post by racket on Nov 25, 2021 20:37:54 GMT -5
Hi Sam
Yep , please replace those plastic hoses , at 12 psi P2 you've probably got an air temp of nearly 200F coming out of the comp :-(
Thankfully propane will burn under a very wide range of conditions hence it runs even with the flametube holes being less than optimal .
She's firing up OK, nice strong starter :-)
Cheers John
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ordonezs
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Joined: November 2020
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Post by ordonezs on Dec 31, 2021 15:51:46 GMT -5
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