|
Post by racket on Sept 26, 2023 16:01:12 GMT -5
Hi John, How do the NGV vanes look? Hope there isn’t too much repair needed! Cheers Scott Hi Scott NGV vanes are looking pretty sad Cheers John
|
|
|
Post by racket on Sept 26, 2023 16:06:17 GMT -5
Sorry to see the damage, but like was said before, glad you're ok. Here is my theory. Once the liner burned through, the pressure drop across the liner is drastically reduced. This leads to poor mixing, higher local gas temps and a large streak of oxygen rich cold air. So for the majority of the wheels rotation it is overtemping, but when it go through the cold streak the high O2 burns the tips off. Think of an oxy-acetylene torch. You heat up the metal then hit it with a blast of oxygen to burn the metal away. Thus the different appearance. When it is jagged, that is due to the metal getting hot enough to loose tensile strength and then chunks are ripped off due to the centrifugal forces. Now why the combustor burned through, still needs some thinking. - Chris HI chris Its the same thing that happened to the 10/98 engine jetandturbineowners.proboards.com/thread/19/10-98-engine?page=4 some good air deflection ducts to force air to the inner wall fixed the problem . Cheers John
|
|
|
Post by racket on Sept 26, 2023 16:17:09 GMT -5
Hi Ralph
Its only the inner walls that are damaged , the outer wall is OK , the only way that the shaft tunnel's heat protection shroud could be damaged is by flames exiting the flametube and impacting the steel cover with enough force to melt it , thankfully the ceramic blanket saved the shaft tunnel from the direct blast .
The static air pressure within the flametube should be lower than the air surrounding it making it impossible for air/gases/flames to exit it , in my case the static air pressure between flametube inner wall and shaft tunnel was lower than within the flametube resulting in the "blowout".
Theres a wider axial gap at the front of the OD of the flametube but at the shaftunnel it becomes restricted , so a longer flametube isn't possible , maybe 10 mm or so but not going help with this problem :-(
Cheers John
|
|
|
Post by racket on Oct 5, 2023 3:26:31 GMT -5
Hi Guys
Bit of an update ........... most bits have been cleaned up as best as possible , but there are warped parts that will make getting it running again a tad more difficult , but not impossible .
New thermocouples fitted , new P4t pitot tube made , A/B main body seam welded up where it split during the failure , there must have been a pressure spike , A/B spray ring checked out OK , NGV walls prepared with new vane slots cut, just need to redesign the vanes so that I get better velocity triangles going into the wheel .
Still chewing over what sort of air deflection out of the diffuser to feed the flametube inner wall .
Slowly slowly , it'll come together :-)
Cheers John
|
|
|
Post by racket on Oct 14, 2023 0:58:49 GMT -5
Hi Guys
Just spent a coupla boring days milling the tapers on my 18 NGV vanes :-(
I'm only using 316L stainless this time , so a bit easier than Inco .
Thankfully the final shaping of the vanes is a quicker job :-)
Cheers John
|
|
|
Post by racket on Oct 19, 2023 1:31:04 GMT -5
Hi Guys NGV is back together My alignment drill holes worked out great , when I tacked the NGV together and reassembled the engine, with great relief , the ignitor plug screwed straight in Theres some minor mods to the flametube still to do and the air deflector ducting to be made and fitted , but not much more , maybe another week and I'll be needing a turbine wheel to complete the build . Cheers John
|
|
|
Post by racket on Oct 19, 2023 19:54:30 GMT -5
Hi Guys A small mod to the flametube Hopefully the "ears" will grab a bit more air as it turns the corner and direct it into the inner wall primary holes Cheers John
|
|
|
Post by racket on Oct 22, 2023 18:47:12 GMT -5
Hi Guys Air deflectors fitted to 6 of the diffuser outlets , the air has to go to the inner wall of the flametube now :-) Not much left to do Cheers John
|
|
|
Post by andym on Oct 23, 2023 16:07:59 GMT -5
Hi Guys Air deflectors fitted to 6 of the diffuser outlets , the air has to go to the inner wall of the flametube now :-) Not much left to do Cheers John Looking good John..... they worked well on the 10/98..... we both know some of the bigger companys had issues to over cone when biulding there engines
|
|
Chuks
Senior Member
Joined: August 2015
Posts: 498
|
Post by Chuks on Oct 29, 2023 4:07:16 GMT -5
Hi John, I found an interesting video about different fuel with different results in same rc gas turbine. I got problem with the same amount of oil added for bearing lubrication since these fuel must have different viscosity. youtu.be/SIfWCWZdfuc?si=xYuS3meS78_p12JE
|
|
|
Post by racket on Oct 29, 2023 16:16:14 GMT -5
Hi Chuks
Unfortunately the "full throttle"setting on the controller was calibrated for Jet A , so even though each run was at 100% the fuel pump would have been supplying different quantities of fuel , hence the different thrust levels which were controlled more by RPM differences ............theres was nothing conclusive about the results other than its necessary to calibrate the controller for different fuels.
If he'd tried to reach 100% RPM we would have seen some "interesting??" temperatures
Cheers John
|
|
Chuks
Senior Member
Joined: August 2015
Posts: 498
|
Post by Chuks on Oct 29, 2023 17:43:49 GMT -5
Got it John. Thanks
|
|
|
Post by racket on Nov 25, 2023 21:22:51 GMT -5
Hi Guys
Turbine wheel arrived this morning , already clipped and will have the rotor ready for taking to be balanced tomorrow morning , I'll be waiting on their doorstep for them to open :-)
Cheers John
|
|
|
Post by Johansson on Nov 26, 2023 4:10:21 GMT -5
Great news!
|
|
jetmanjoe
Junior Member
Joined: October 2023
Posts: 64
|
Post by jetmanjoe on Nov 26, 2023 4:18:45 GMT -5
Hi Guys Turbine wheel arrived this morning , already clipped and will have the rotor ready for taking to be balanced tomorrow morning , I'll be waiting on their doorstep for them to open :-) Cheers John haha I can just imagine you looking through their window waiting for them to turn the sign to say open.
|
|