Small turbo shaft engine project

[mckiwi]

Hi guys, I am new to this site and very please to have found you. My name is Craig and I am a long time turbine enthusiast. I have built a turbocharger base turbine already that ran on liquid fuel (jet A). I added a free power stage to it but failed due to poor matching of parts and fundamental design.
I still have the turbine disease!
I would like to build a small power turbine that I could power a scooter or small bike.
I was impressed with the FADEC controlled auto-start jet engines used in model planes so have bought a Jet Joes 1400 with all the electronics.

I have had some help from John (aka Racket) with the maths and now have a plan to fabricate a power stage using a turbocharger wheel and vaned radial inflow housing ( I think that's how you describe it).
I will use a small planetary gearset and centrifugal clutch to maximise useful power available.

So far I have made the interstage section and will continue with the vaned scroll and bearing housing.
I appreciate all input and comments.

Progress may be slow at times due to limited play time!

Craig

Attachments:

[racket]

Hi Craig

Good to see you starting a Build Thread :-)

Will be looking forward to progress reports

Cheers
John

[smithy1]

Hi Craig,
I've had a few of the JJ-1400 engines, still have a couple at home in various stages of assembly, even a JJ-3000 and a couple of Kingtech's, K80E and a K180G full kerosene start.

Cheers,
Smithy.

[mckiwi]

Progress report. I have designed the parts for the scroll and vanes. They are getting laser cut out of 304 stainless plate of various thickness. Can't wait to start putting this thing together! (-:

[racket]

Hi Craig

Excellent news :-)

Cheers
John

[mckiwi]

Hi guys. Just thought I should post an update on my progress so far. Its been a slow build but chipping away at it.
My workshop has a small lathe, TIG and MIG welding gear, drill press and grinders. I have designed many of the parts on CAD and had them laser cut from stainless plate.
The inter stage section is complete and the turbine run nice and cool with this fitted.
I have assembled the NGV according to Johns calculation. The outlet and flange is done and the scroll shape has been cut from 3mm stainless plate.


I have the material for the shaft tunnel ready to machine.
After that I will assemble and weld the scroll. Then the gearbox....

[mckiwi]

[racket]

Hi Craig

Coming together nicely :-)

One thing I feel I should mention , the tip clearance on the freepower wheel exducer , because you have fairly heavy section material on the shroud you might find the turb wheel blades will expand a lot quicker than the shroud and they could rub unless theres a reasonable clearance .

Cheers
John

[mckiwi]

Thanks for that John. I was careful not to have excessive clearance. What would be acceptable for this design (62mm exducer)?.

[racket]

Hi Craig

Anything up to 0.010" radial clearance won't be a problem as gas pressures are rather low at that point so minimal tip leakage , besides , radial wheels are fairly tolerant of a bit of clearance , I'd be inclined to go closer to 0.015" radial clearance just to be on the safe side .

Cheers
John

[mckiwi]

Hi team
Just a question about lubricating the bearing on the free-power. I was thinking of supplying oil from a pump to the bearing closest to the power turbine. this would flow through the second bearing and drain onto the sun gear (planetary gear-set). Then lubricating the rest of the gear-set.
I have the original piston ring type oil seal on the shaft. I am using C3 bearing races and will preload them. Not sure what style of oil pump I will need, hoping for some suggestions please. Should I run this pump after the gas producer has shut down to keep cooling the bearings?
What sort of flow rate/pressure would be required with this set up?

Thanks

Craig

[racket]

Hi Craig

You might be able to use an RC turbine engine gear fuel pump for the lubrication.

Post shutdown lubrication would help remove any heat soaking back to the bearing from the big lump of turb wheel .

Depending on your length of run times and power output average the amount of lube required will vary , for a few short duration runs lasting maybe 30 seconds at a time you won't need a lot of lube, but for extended running at high power settings then there'll be a need to remove a lot of heat being generated .

Oil pressure has to be high enough to breakthrough "windage" forces and get the lube to where it has to , so 50psi might be needed at high power .

Theres lotsa unknowns with such a small unit where it could be difficult to fit the normal amount of lubrication points into the available space , you may need to make compromises.

Cheers
John