Testing KJ-66 for research
Hello, I am a masters' student in mechanical engineering. I'm investigating small scale electrical generation, specifically at using gas turbines for small (>10 kW) generator units. I'm experimenting with a KJ-66 engine to determine how much shaft power I could extract from the engine. To convert from a jet engine to a gas turbine I replaced the propelling nozzle with a diffuser that I had made.
Last week after a long time of setting up and testing problems (I have completely got rid of the manufacturer's control system and have my own, as well as custom sensors throughout the engine) I finally got the engine up to 126 kRPM. Unfortunately the engine failed at this speed (but I did have enough data for that run to be useful). I think it was actually a rear diffuser guide vane that failed and then hit the turbine which ripped off a turbine blade and generally caused havoc all through the engine. I do have a backup engine worth of parts so its not catastrophic or anything, just annoying to have to reassemble everything (and also not have a backup from now on).
In assembling the engine I found that the shaft tunnel and the NGV piece had a sliding fit. I know the previous ones I had used were pretty tight so I was surprised. Now I looked in the KJ-66 assembly manual and it didn't say anything about the fit. I also have a JG-100 manual which says it should be a sliding fit (for the JG-100 engine which is very similar to the KJ-66). So essentially I was wondering, why would a sliding fit be good? How does the NGVs stay in place? Is the outer casing the only thing holding it from moving axially?
If you guys are interested I can put up some pictures later (and give updates on how the research is going)
Paul