After a long, long day full of anticipation I finally could pull the engine apart to check out the internals. What would the core look like after several minutes of full power runs with high temps?
Unbelievably good actually! The NGV section looks fine with the coating still in place although a bit discoloured, vapor tubes ok as well, some slight rounding around the end of the tubes but I had to look for it to see it.
The guide vanes are still as sharp as they were when they were new, hard to believe since they are the most exposed pieces of metal in the engine. The combustor is looking like new as well, no cracks or dents anywhere.
The turbine wheel has some burned oil deposits near the blade roots, might be some minor oil leak past the shaft seal. Other than that it looks fine, no signs of heat soak past the rear bearing.
I removed the fuel manifold and tested it with propane, it was difficult to take a good picture of it since I had to hold the preheat button down to keep the propane flowing. No blocked syringes but two of them were flowing a bit less than the others so that will be adressed later.
And now to the main attraction, the NGV throat area! *drum roll*
I finally think I´ve nailed the temp issue, the throats measures 10mm x 19mm which calculates to a total of 34.2cm2. Take away the impingement nozzle area and I end up at 33.7cm2. That is not exactly near the 31.6cm2 I should have had.
If I block one of the passages I get a total of 31.8cm2 which is close enough I think, might be worth a try before I go ahead and make a completely new NGV.
Cheers!
/Anders