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Post by racket on Apr 26, 2015 21:56:24 GMT -5
Hi
NO NO NO
Use a good quality , preferably synthetic, oil that the turbo would have had when on the IC engine .
The hydrodynamic bearings need oil for not only lubrication and cooling but also to control rotor gyrations which can be quite complex in extremely high rpm shafting .
Cheers
John
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parkland
Junior Member
Joined: February 2015
Posts: 57 
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Post by parkland on Apr 27, 2015 9:02:34 GMT -5
Cheers to you John,
You must really love these engines to help everyone the way you do!
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Post by racket on Apr 27, 2015 16:15:17 GMT -5
LOL...............its a love/hate relationship at times :-)
Being retired gives me the time to help where I can
Cheers
John
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mitch
Senior Member
Joined: August 2014
Posts: 285
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Post by mitch on Apr 28, 2015 6:50:05 GMT -5
parkland, please be sure to pump the oil into the turbo also, don't do any of those gravity fed setups like this one: www.youtube.com/watch?v=CbIojOKp3-kThe bearings need a high volume flow of oil to back up and create pressure in the core, to make sure the bearings ride on the thin film of oil. You probably already knew this, but I just want to make sure! Running without a pressurized oil system can be dangerous |
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parkland
Junior Member
Joined: February 2015
Posts: 57
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Post by parkland on Apr 29, 2015 9:31:54 GMT -5
Yup I did read that somewhere, I was just more curious about the thinner oil's ability to flow faster and remove more heat.
I didn't realise there was so much protection required also, I thought they just used say 15w40 because thats what the engine runs on.
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parkland
Junior Member
Joined: February 2015
Posts: 57
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Post by parkland on Apr 29, 2015 12:11:06 GMT -5
Forgive me for the truly random question, the mind wanders sometimes.
I was bored again, and looking at videos about jet tip helicopters.
I immediately thought "What about a gas producer engine on the helicopter, and putting exhaust tubes on the rotor, to make it spin."
And then, I thought, what about an air pump (compressor wheel), on the helicopter, driven by the rotor, and the compressor pushes air along tubes along the rotor blades, and then have combustion chambers on the tips with nozzles?
Just a random thought of the day haha.
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Post by racket on Apr 29, 2015 17:15:56 GMT -5
Rotor tip combustion is "difficult" due the massive centrifugal loads , though it was used with a type of pulsejet
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parkland
Junior Member
Joined: February 2015
Posts: 57
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Post by parkland on Apr 29, 2015 22:26:35 GMT -5
Rotor tip combustion is "difficult" due the massive centrifugal loads , though it was used with a type of pulsejet But what if the rotor tips had only the combustion chamber and nozzle, and the pressurized air was fed through the blades, from a compressor that was on the body? The rotor spinning would power the compressor. Surely a combustion chamber and nozzle could be built really light with the right materials, and tubing to hold 50 psi of warm air certainly doesn't ask much of any materials.... ?  |
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Post by racket on Apr 29, 2015 23:20:45 GMT -5
But its the centrifugal loads on the fuel spray within the combustor , the combustor needs to be at right angles to the rotor blades to minimise drag , this then forces the fuel to the outside of the combustor ...............its not a construction problem.
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Post by racket on Apr 29, 2015 23:25:27 GMT -5
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parkland
Junior Member
Joined: February 2015
Posts: 57
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Post by parkland on May 2, 2015 11:59:22 GMT -5
John,
I was reading some other threads on here, and I noticed somewhere, you mentioned that some turbine blades found from commercial turbines can stand much greater temperatures than automotive turbo jet engines.
Thinking of that, could decent power gains be had by injecting fuel after the gas producer, before the power turbine?
The reason I ask, is I notice a concern of a few people is fuel efficiency.
You mentioned fuel burn rate is roughly ~1 lb/hp/ hr.
So if someone was going to build a vehicle of some kind, and it needed say 20 hp to move, but 40 hp to accelerate quickly, is it possible that with the right parts, you could have a 20 hp gas producer, and get the extra 20 hp from injecting fuel after the gas producer?
This would save a ton of fuel when not accelerating quickly.
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Post by racket on May 2, 2015 18:17:33 GMT -5
Hi
Nope , I wouldn't have said they can stand much greater temperatures , ..............most commonly available aero turbine blades can't take any more temperature than our Inconel based turbo turbine blades as they're made from the same material basically, its only the aero blades with cooling holes and very sophisticated construction that can cope with another couple of hundred degrees C .
There is room for post gas producer combustion to restore TOT temperatures to T I T temperatures , but thats only another ~150 degrees C in most cases, it will improve output but not by more than a handful of percentage points , theres no 100% increases to be had .
If a lot of fuel/heat is added at the interstage theres the possibility of surging the gas producer unless the freepower had variable NGV geometry and that the wheel was sized big enough to cope with the greater volume ...............complication , complication and more complication , great in theory but really out of a DIY'ers reach .
Cheers
John
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