I got it! I got it! - - - I don't got it! (groan)

So what's happenin' Dude? I hear you ask.

Well, I almost had it running - but you've heard that story before? no - really!

My careful measurements of the power required to drive the engine from an external motor as I brought the fuel flow up have convinced me I'm on the right track.
The plot of power versus temperature exactly parallels the theoretical calculation.

Except for two effects.

The predicted relation is a straight line but I found I was getting a curve that showed power being lost in two ways:-
One was at startup. The effort required to spin the engine cold is much greater than expected. I put this down to the effect of oil viscosity.

As an aside, it's amazing how fine the operating point of the turbine is - If losses exceed gains by even the smallest part of a watt the engine won't run.
If gains exceed losses by just as much, the turbine can accelerate out of control in seconds.
Despite the massive power potential, the friction losses resulting from a few grammes of resistance observed at the turbine diameter make the difference between life and death.

The second effect is a similar frictional loss that appears at high temperature - I have no idea what is causing it. It's tiny - I can barely feel it when turning the shaft by hand - but it kills the engine stone dead.

I said I almost had it running?
Yes: With the engine being driven flat-out by my blower and pushing the combustion temperature right up to the limit, I reached a region where the engine definitely tried to run.

No doubt in my mind at all. It suddenly accelerated, becoming very sensitive to the amount of fuel being fed in - for a moment I thought I had lost control from the way it accelerated. But then effect #2 kicked in (I think) and the engine slowed again -then picked up - and slowed again.
After a few such spurts, I decided to stop the test because the turbine wheel and NGV were glowing brightly and I know where that leads! (See last post)

Anyway - Got to find the cause of that friction.