dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
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Post by dieselguy86 on Dec 13, 2023 20:12:09 GMT -5
Hi John,
This is a bit out of left field, and way too late in your engine development to incorporate, but it seems like a good case for vnt.
Have you looked at how holset does theirs? Vanes are fixed, but a ring slides axially fwd/back to vary the amount of throat area. I think it would be a good system to implement, and it's a wayyy simpler system than garret's.
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Post by racket on Dec 14, 2023 0:16:28 GMT -5
Hi Joe
I'd love VNT , but attempting to fit the extra complication into my engine would be a challenge I don't think I'd want to start on .
This poor old engine is already feeling the effects of too many things going wrong , nothing is straight or true anymore :-(
Cheers John
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monty
Senior Member
Currently being spanked by mother nature.......
Joined: September 2018
Posts: 400
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Post by monty on Dec 14, 2023 10:54:54 GMT -5
Joe and John,
Regarding the VNT. I have room in the HX82 concept I'm working on, but there isn't any reason I can think of to use it in a jet. Maybe in a turboprop to allow better efficiency in reduced power cruise. In a jet if you choke the NGV you get fixed geometry that works over the range of pressure ratios and mass flows that the engine sees in use. Nobody cares if the idle efficiency is a little better. Not worth the effort. The key is to match the turbine/ngv and compressor/diffuser so VNT isn't needed. The VNT might allow you to keep the zero exit swirl condition all the time, but I'm not sure that's really worth the extra complexity.
It "might" be worth looking at for my fan engine, but there isn't much physical space to work with.
Monty
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Post by racket on Dec 14, 2023 16:40:18 GMT -5
Hi Monty
Yep , a VNT would help with getting the engine "tuned", then lock in place , .............space is at a premium for me too :-(
Hopefully get the engine apart today if the weather stays cool enough for me to work in my shed :-)
Cheers John
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dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
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Post by dieselguy86 on Dec 14, 2023 18:29:24 GMT -5
Hi Monty, John Just seems like it would be a tool to help better match the turb to the compressor, a large throat for wot, and slightly reduced throat for cruising or low power settings to help power the turb. But I might be thinking of when John had the really clipped turbine and had issues... It wouldn't have to be as extreme as one for a turbo. If you look at holsets design, I think it could be adopted and made pretty compact. The ngv backwall basically slides over the vanes. Instead of using an actuator and posts like holset does, a simple ball and ramp design could be used. If you've ever seen how brake disks work in older tractors, that's what I'm referring to. Here's a vid I found, it's backwards to what I proposed. Instead, leave the ngv fixed and move that ring.... youtu.be/WfL0jo8XIME?si=7hUCOYxZyYTctJLL
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Post by racket on Dec 15, 2023 3:33:03 GMT -5
Hi Guys Engine pulled apart and "most" bits look OK and running cool. BUT..............I love buts :-) two of my Primary air injection tubes ibb.co/74ZT5jm have been burnt off , and their fragmented molten remains were ejected/sprayed back out of the tube and down the outside of the flametube and along the inside of the outer can , some interesting witness marks . I guess the surge during the last testrun caused this , but it doesn't explain why only 2 of them and not besides each other . The FT inner wall is now running a lot cooler . The NGV throats have been opened up to 10 mm from the previous 9.2 mm ,~9% extra area , hopefully enough to shift the flow to more stable regions . I'll need to have a bit more of a think on the burnt tubes before I try rectification and reassembly Cheers John
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Chuks
Senior Member
Joined: August 2015
Posts: 498
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Post by Chuks on Dec 16, 2023 6:34:19 GMT -5
Good thing is that there no more major damage. Opening up the throat hopefully will be the only solution remaining. Don't forgot to take pictures of how the throat can be adjusted.
Thanks.
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monty
Senior Member
Currently being spanked by mother nature.......
Joined: September 2018
Posts: 400
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Post by monty on Dec 16, 2023 12:30:52 GMT -5
If you've ever seen how brake disks work in older tractors, that's what I'm referring to. I know EXACTLY what you are talking about. CASE tractors and backhoes specifically. Living in a place that has hills where tractors need brakes or you die, next to a place that is flat (KS, OK) where brakes are optional and old tractors are plentiful.....I have replaced many of those balls that became eggs...Case brakes are still marginal even when they "kind of" work... ;-)
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monty
Senior Member
Currently being spanked by mother nature.......
Joined: September 2018
Posts: 400
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Post by monty on Dec 16, 2023 12:33:32 GMT -5
John,
Which two tubes? Were they on the bottom? Or is it random.
Monty
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Post by racket on Dec 16, 2023 18:39:30 GMT -5
Hi Monty
At 4.30 and 7 O'clock with 3 unaffected tubes inbetween , I've looked for any sort of reason and can't find it , I'll just put it down to aberrant surge which should go away once I fix the surge problem , hopefully :-)
I've replaced the two tubes , opened up the NGV , time to clean up the parts and reassemble .
I might just increase the P2/fuel pump interlock safety setting so that I can take her up to 5:1 PR ..............let this race horse of a comp wheel have its head, its not happy being just a cart horse .
Cheers John
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Post by racket on Jan 3, 2024 4:42:04 GMT -5
Hi Guys
Test today
Finally got the videos downloaded .............computer was reprogrammed over Christmas by the family techy , we seem to have lost some things :-(
Will get them onto Youtube tomorrow , took her up to 5:1 PR .............just to check the fuel pump safety interlock :-)
Cheers John
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Post by racket on Jan 3, 2024 5:19:32 GMT -5
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Post by Johansson on Jan 3, 2024 13:27:19 GMT -5
Awesome John! I was a bit nervous when you left the engine running at 3.5bar P2 to take the temp readings, opening up the NGV throats seems to have done the trick!
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Post by racket on Jan 3, 2024 14:47:39 GMT -5
Hi Anders
Yep , a big improvement over the last testrun , lots more air going through the engine , the P2 gauge a lot steadier , not the surge of last test , lotsa info to digest today :-)
Cheers John
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Post by racket on Jan 3, 2024 15:16:48 GMT -5
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