Miniture gas turbine overhaul

[Bjorn_B]

About a year ago, I built this.
<a href="https://www.youtube.com/watch?v=DJSrzSZ8_7M" target="_blank">http://www.youtube.com/watch?v=DJSrzSZ8_7M</a>

As winter came and the lake next to our house froze, I thought what would be more natural than to stick it on a snow-racer. With up to 180N of thrust on tap, it is enough to get me scared I hope.

However, strange sounds and a bit of suspected snow ingestion meant overhaul time.

Inspection revealed slight damage to the compressor wheel, not too bad after a light touch up with a small file and emery cloth. In worst case it is due for replacement.

Combustor and fuel distribution system is ok no problem.

Need to take it apart further for bearing replacement, will probably increase bearing preload a little bit. More on this later when I get there.

[Bjorn_B]

Some pictures

[Bjorn_B]

The snowracer

[rythmnbls]

Hi Bjorn,

Very impressed ! 400 degrees C @90K rpm is something to be proud of.  Great work.

Looking forward to seeing more runs.

Regards,

Steve.

[Roger B]

That looks to be a fun (slightly dangerous toy  )   

[Bjorn_B]

Hi Bjorn,

Very impressed ! 400 degrees C @90K rpm is something to be proud of.  Great work.

Looking forward to seeing more runs.

Regards,

Steve.

Thanks steve, there is room for choking the exhast nozzle a bit more for more thrust, temps at 120.000 are about 600C

[Bjorn_B]

That looks to be a fun (slightly dangerous toy  )   

Yes, sadly the snow has melted away, hoping for another cold period because if that happens the ice will be awesome!

[vcutajar]

Impressive RPMs for such a small engine.  What sort of fuel are you using? JetA1?

Vince

[Bjorn_B]

Impressive RPMs for such a small engine.  What sort of fuel are you using? JetA1?

Vince

Vince, Mostly ordinary diesel, some camping kerosene (for the smell) and some oil added to the mix for bearing lubrication. Jet fuel is hard to get over here without contacts.

[vcutajar]

Thanks.  Was just curious what is used on model gas turbines.  On the real big engines there is a procedure (limitation) that they have to run at idle for at least 2 minutes before high power is applied.  This is also done for shutdown.  Is this done on the model engines or is it not required?

Vince

[scc]

A very scary looking toy.   Is that a steering device or just  something to hang onto and steer by weight transfer? It looks easy to set fire to the back of your jacket!     Awesome........I'd love to see a video of you riding it.          Terry

[zeeprogrammer]

 

Good grief. I'd be in another room watching it. In the next state.

[Dave Otto]

Inquiring minds want to know; did you ride it? and how did it go?

Dave

[Bjorn_B]

Vince; No real need for a delay after idle rpm is reached, the ecu links rpm to throttle demand after that. It is propably a good idea to wait a bit further for temperatures to stabilize. Idle is not really ideal however since exhaust temps are higher there than higher up in the rev range. This is due to low compressor efficiency at idle I guess. Full size turbines have longer shafts and hence more thermal expansion in absolute numbers. They they to be more careful because of that I guess. The steam turbines at work takes hours to start from cold...

The stop sequence pulses the starter motor for cooling until egt goes below 100C. There is actually need for less colling if shutdown is done from about 60.000 rpm than at 35.000.

Terry, yes that is thougt to be a steering device, not known to be effective..

Dave, only a short test in the garden yet in wet snow

Zee, In on the other side of the atlantic