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Post by smithy1 on Nov 22, 2016 1:37:52 GMT -5
Yeah....50psi is a good round number for warm oil.....if you can hold ~50psi with the oil warm and engine running at a decent P2....you should be good to go.
Insufficient oil pressure and volume can turn an otherwise good turbine into a pile of junk in no time.
Cheers,
Smithy
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mitch
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Posts: 285 
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Post by mitch on Nov 22, 2016 14:56:11 GMT -5
Smithy,
Thanks for the input. I will run some more tests to make sure that my oil system works sufficiently before running the engine.
How should I go about heating the oil for tests without the engine? I have tried a blow torch on the oil tank, but that seems to take forever to heat things up even a small amount.
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Post by smithy1 on Nov 22, 2016 21:16:28 GMT -5
Smithy, Thanks for the input. I will run some more tests to make sure that my oil system works sufficiently before running the engine. How should I go about heating the oil for tests without the engine? I have tried a blow torch on the oil tank, but that seems to take forever to heat things up even a small amount. LOL...light a fire under it..  I have heated the oil before pouring it into the tank before, for testing purposes.... but that's not real practical in most cases. I suspect your system will be fine once the "by-pass" tap is utilized. Cheers, Smithy. |
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mitch
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Post by mitch on Nov 23, 2016 16:44:11 GMT -5
Smithy,
Hopefully it will work okay during my first test!
I had a chance to test the combustion chamber today, after making some modifications to it. I changed out my old propane injector for a new one that directs the propane into the evap tube for a more even burn, and I changed the flame tube holes slightly.
I instrumented the test with a thermocouple so I could get a rough egt estimate.
The liquid fuel being used was very low quality, it was some old kerosene (which had been sitting in my barn for well over a year) mixed with 70% isopropyl rubbing alcohol.
During testing I found that the propane had a nice uniform burn around the combustion chamber, and the EGT ranged anywhere from 200 degrees F to 400 degrees F on propae alone. Keep in mind, this was with a cold tank of propane that was probably only 1/2 way full.
With Kerosene on, I found that I could spike EGT to 700 degrees F +, but was having trouble keeping a steady injection pressure. The combustion was pretty much un effected until the fuel pressure reached 20+ PSI. I am going to re run all these tests using a smaller 4 gph injector nozzle, as I had used a 15gph nozzle in this test, which is way too big. I have some video showing the combustion chamber's burn characteristics that I will upload later.
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Post by racket on Nov 23, 2016 16:50:54 GMT -5
Hi Mitch
Yep , a small fuel nozzle will produce a more realistic representation , you need to be able to get those "exhaust" temps up to ~1,500 F with stable combustion .
Cheers
John
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mitch
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Posts: 285
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Post by mitch on Nov 23, 2016 16:51:50 GMT -5
  It was hard to get a good picture of the inside of the combustion chamber, but during all the tests, the combustion seemed to be pretty even around the entire chamber, with most of the burning occuring near the primary zone. |
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mitch
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Post by mitch on Nov 24, 2016 19:37:22 GMT -5
Ran another test today with the new 4gph nozzle, and I found that it will not flow any fuel for some reason. I'll have to look into that later. I was able to get my EGTs are propane alone to around 1100 degrees F, however, which is better than yesterday. I also found that I had some weird heating patterns on the combustion chamber too, and an odd red residue on the internal components after test running.    |
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Post by racket on Nov 25, 2016 15:55:35 GMT -5
Hi Mitch
That red stuff is strange , no consistency with its placement which makes it hard to explain .
Keep getting those temps up .
Cheers
John
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Post by finiteparts on Nov 27, 2016 15:03:24 GMT -5
Hi Mitch,
I have seen that same red oxide coating on my early engine builds that were using steel flametubes. I am pretty sure it is a iron oxide formed in an oxygen rich flow region, likely a local region where there is little to no reaction occurring, but near enough to the reaction that the local heating is driving the oxidation rate to be much faster. It looks like you are using steel or iron tubing there.
A bit of background to help in this discussion...almost all chemical reactions increase their rate as you go up in temperature and you can use the Arrhenius Rate Equation as a estimate of this. Since combustors are very high temperature regions with "high" concentrations of oxygen, oxidation resistant materials are required. That is one reason why materials like Hastelloy X, Inconels, etc. are chosen for use in combustion liners, because they take a very long time to form oxidation build up. So when iron is used in high temperature regions, it is very susceptible to rapid oxide formation...at even higher temperatures, the iron just burns (like when you use an oxy-acetylene torch).
It looks like you propane was burning in the upper cup area...was that your intention?
Good luck,
Chris
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mitch
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Post by mitch on Nov 27, 2016 16:53:59 GMT -5
finiteparts,
Your explanation of the red residue makes sense, as it is a mild steel combustion chamber, flame tube, and evaporator assembly. I may consider switching to some stainless steel parts in the future after some testing.
When you say "upper cup area" are you referring to the upper section of the evaporator assembly? The propane "injector" in my combustion chamber is positioned to flow propane right into the evaporator tube.
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mitch
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Posts: 285
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Post by mitch on Dec 6, 2016 16:41:32 GMT -5
Did some work on the turbine today, decided to scrap my current oil setup. The modified small block pump was just too leaky and junky for me to stand. I am considering trying to modify it further to make it work, but I might try to just buy a different pump instead, that requires less modification to work.
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Post by smithy1 on Dec 6, 2016 17:54:26 GMT -5
Did some work on the turbine today, decided to scrap my current oil setup. The modified small block pump was just too leaky and junky for me to stand. I am considering trying to modify it further to make it work, but I might try to just buy a different pump instead, that requires less modification to work. I have an old "pushrod" Subaru engine oil pump driven by a 36v electric motor, John originally designed & built this for the 6041 Go-kart....works perfectly. TBH, I've not had to do anything to it, mainly because it just works..! I have added an oil cooler with the associated hose work etc, but the original system is still sound...This is where the "KISS" principle works best. Cheers, Smithy |
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Post by racket on Dec 6, 2016 18:27:12 GMT -5
Yep , the Subaru pump is a nice unit to work with as it has filter mount and internal pressure relief built in , just a case of making up the adapter.
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mitch
Senior Member
Joined: August 2014
Posts: 285
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Post by mitch on Dec 7, 2016 10:53:12 GMT -5
Did some work on the turbine today, decided to scrap my current oil setup. The modified small block pump was just too leaky and junky for me to stand. I am considering trying to modify it further to make it work, but I might try to just buy a different pump instead, that requires less modification to work. I have an old "pushrod" Subaru engine oil pump driven by a 36v electric motor, John originally designed & built this for the 6041 Go-kart....works perfectly. TBH, I've not had to do anything to it, mainly because it just works..! I have added an oil cooler with the associated hose work etc, but the original system is still sound...This is where the "KISS" principle works best. Cheers, Smithy Smithy, do you know what model Subaru, or what engine the pump came off of? |
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mitch
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Posts: 285
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Post by mitch on Dec 7, 2016 14:52:12 GMT -5
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