"Fat Boy" 12/118 thrust engine

[monty]

May 8, 2019 12:45:25 GMT -5 Johansson said:

Hi John,

Tell me about it, the darn things must have a life of their own. The JU-02 clearances have changed noticeably over the test run period and I´ve had to modify it a couple of times to keep it running true.

Cheers!
/Anders

John/Anders,

What do you guys think is moving? The aluminum diffuser/tunnel or the NGV?? Any insight is greatly appreciated and may change my design plans.

Monty

[racket]

Hi Monty

Just finished chucking the NGV up on its mounting jig in the lathe , the NGV is "wobbly" ...............LOL, can't find a surface on it thats running true ,...... thats the problem with a welded up NGV , too many stresses built in that relieve themselves in different ways at different spots depending on different temps from any hot streaks etc , theres up to ~0.017" out of round at the outer can slipjoint at the rear , this is then tilting the outer can at the front securing screws making for the slight out of alignment between can and comp front cover face.

The only solution is to increase the exducer shroud clearance and realign the jetpipe in the V band flange .

Ideally the NGV needs to be a "floating" assembly and not part of the hard fitted parts .

As for my comp inducer being slightly off centre , I think its caused by the lube pipes possibly wedging the front cover a bit to one side , I allowed a few thou "movement" when the front cover was machined relative to the diffuser wall to let me centralise the comp , but if the lube pipe bends have relaxed a tad they might be restricting the movement , I might just need to get a round file through the pipe holes and open them up a tad to give a bit more "rattle".

Cheers
John

[monty]

May 8, 2019 21:03:03 GMT -5 racket said:

Ideally the NGV needs to be a "floating" assembly and not part of the hard fitted parts .

John,

Point taken. Will proceed accordingly.

Monty

[pitciblackscotland]

May 8, 2019 21:03:03 GMT -5 racket said:

Hi Monty

Just finished chucking the NGV up on its mounting jig in the lathe , the NGV is "wobbly" ...............LOL, can't find a surface on it thats running true ,...... thats the problem with a welded up NGV , too many stresses built in that relieve themselves in different ways at different spots depending on different temps from any hot streaks etc , theres up to ~0.017" out of round at the outer can slipjoint at the rear , this is then tilting the outer can at the front securing screws making for the slight out of alignment between can and comp front cover face.

The only solution is to increase the exducer shroud clearance and realign the jetpipe in the V band flange .

Ideally the NGV needs to be a "floating" assembly and not part of the hard fitted parts .

As for my comp inducer being slightly off centre , I think its caused by the lube pipes possibly wedging the front cover a bit to one side , I allowed a few thou "movement" when the front cover was machined relative to the diffuser wall to let me centralise the comp , but if the lube pipe bends have relaxed a tad they might be restricting the movement , I might just need to get a round file through the pipe holes and open them up a tad to give a bit more "rattle".

Cheers
John

Hi John,
Do you think maybe we could get the NGV cast up similar to the T30 NGV

[racket]

Hi Mark

I once made up a wooden pattern for Andrew to get a NGV cast in stainless , but there was some reason why the couldn't do it , ......its a simple item so shouldn't really be a problem

Cheers
John

[pitciblackscotland]

Hi John,
Mmmm you got my thinking here next time i see Andrew i will ask him. That NGV on the T30 is cast iron i think will check it out tomorrow.

Cheers,
Mark.

[racket]

Hi Guys

After a fair bit of messing around I've got the comp front cover to "move around" a few thou more, which should allow centralisation of the inducer.

The turb wheel exducer shroud was another matter , no easy solution other than a "two wrongs making a right" , the jetpipe was chucked up in the lathe and the shroud "cleaned up" to remove high spots , then it was fitted to the NGV stub and checked aginst exducer , the exducer was offset a tad to the bottom side and rather than making new bits , I refitted the jetpipe to the lathe and set it up a bit "off" so as to skim out several thou on the offending side.

When refitted to the NGV I had my 0.025" clearance , though theres a bit more on the other side which I'll live with .

Time to finish reassembling the engine :-)

Cheers
John

[Deleted]

Nice..... looking forward to seeing it run again....

[turboron]

John, the distortion you and Anders are experiencing on you gas turbines points to a need for stress relief during fabrication. Have you checked the temperature soakback to the compressor upon shutdown? The soakback may be relieving the stresses in the fabricated compressor parts.

Thanks, Ron

[racket]

Hi Ron

Stress relief ................LOL, I think this fabricator has the greater need for that ;-)

I'm pretty certain my raw casting were stress relieved initially , but as with anything thats machined up, with metal removed here and there , theres going to be a difference introduced , my comp centralisation was only a few thou out , allowing the inducer to just scrape the shroud over a wide arc when forced to one side with dry bearings, it should "centralise" once the lube is introduced.

Theres undoubtedly more stress relieving going on with each "cycle" as you mentioned , but with our limited means, I guess the best we can do is run a tad more clearance than ideal , probably why standard turbo clearances are pretty generous.

Cheers
John

[racket]

Hi Guys

Well she's finally all assembled and back on the test stand .

Everything tested out OK , ignition of the preheat gas with the new flametube and different gas manifold , rpm of the starter checked and found to produce ~0.15 Bar - 2.2 psi of static pressure ( P2) from the compressor at ~11,000 rpm , just need to make up a new brew of fuel and I'll be ready to take her out for a test run , hopefully next week .

Cheers
John

[turboron]

John, cross all unused digits.

Thanks, Ron

[CH3NO2]

Thanks for the heads up John and Anders.

[racket]

Hi Guys

Another test run this morning , bit of video youtu.be/GHye60WQn7Y

Time to drop the engine out and check the flametube ...................still getting large variations of jetpipe temps between thermocouples ..................but did get up to a 3.85:1 PR :-)

Cheers
John

[Deleted]

May 21, 2019 19:10:39 GMT -5 racket said:

Hi Guys

Another test run this morning , bit of video youtu.be/GHye60WQn7Y

Time to drop the engine out and check the flametube ...................still getting large variations of jetpipe temps between thermocouples ..................but did get up to a 3.85:1 PR :-)

Cheers
John

Nice to see it running again.... its making some noise

Chat soon, all the best Andy