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Post by racket on Jul 23, 2024 20:56:34 GMT -5
Hi Chris
Thats not too bad actually :-)
I've done some thinking and I've decided to reduce my NGV throats back to a tad under 10 mm from the current 11mm , this should increase my "impulse" onto the turb wheel to offset the reduced efficiency.
An earlier test with 9mm throats was too tight, but with low temps , so maybe a bit of compromising required
Cheers
John
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Post by racket on Jul 24, 2024 4:12:17 GMT -5
Hi Chris I've gone back to look at this Paper web.unica.it/unica/protected/372063/0/def/ref/MAT292228/ some good "numbers" in it ,especially their flow through their NGV throats, which works out at a Corrected Flow of 3.166 lbs/sec through 10.6 sq ins of throat area , so 3.347 sq ins /corrected lb/sec . If I use the same rate for 5 lbs/sec at 1173K , then I need throats at ~9.5mm . Engine is being disassembled and I'll tighten up the throats to that size and give it a go :-) Cheers John |
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Post by racket on Jul 25, 2024 22:28:10 GMT -5
Hi Guys
Don't you hate it when you're assembling something and theres a washer missing , one little spring washer for a 5mm screw , couldn't find it anywhere , did I accidently drop it in the engine , are there 2 washers on one of the other screws , spent a good half hour searching until I found it hiding where it shouldn't have been .................engine now back on the test stand :-)
Cheers
John
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richardm
Senior Member
Joined: June 2022
Posts: 413
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Post by richardm on Jul 26, 2024 4:10:53 GMT -5
Half an hour ! You were fast. Some surgeons took days to find out that missing forcep was left inside their patient body...LOL!
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Post by racket on Jul 28, 2024 1:01:24 GMT -5
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Post by racket on Jul 30, 2024 0:59:04 GMT -5
Hi Guys
NGV needs redoing , the same vane burnt out again :-(
I really can't understand why the hot streak , the flametube hasn't any damage , all of the evap tubes look the same colouration ...........I'm going to have to do a very accurate flow test on each injector at full pressure .
Ah well , it'll give me something to keep busy with :-)
Cheers
John
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Post by racket on Jul 30, 2024 19:21:54 GMT -5
Hi Guys I think I've been looking at the wrong end of the engine :-( Just had a look at an old vid from Nov '21 www.youtube.com/watch?v=mKEh9mw7pf4&ab_channel=racketmotorman , same open exhaust as the other day but thrust levels were a lot different , at 1 Bar P2 I had 48 lbs vs 26 on monday , at 2 bar..... 120 lbs vs 70 , this was with my "racketjectors" , but I now have 18 X 0.5"dia evap tubes at the entrance to the NGV , which with the extra swirl I'm now producing within the flametube would mean lotsa turbulence at the NGV entrance as well as flow restriction . This might account for why the engine doesn't behave as it should when I change NGV throats , they're not "filling" correctly , so even though a 9.5mm throat should choke flow it isn't , the engine works better with 11mm throats . P4t was 0.45 Bar back in '21 vs 0.18 Bar the other day. Got some thinking to do to correct this :-) Cheers John |
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Post by racket on Jul 30, 2024 21:27:04 GMT -5
Hi Guys NGV split , time for a redesign :-)   Cheers John |
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Post by racket on Jul 31, 2024 1:52:42 GMT -5
Hi Guys
Rummaged around and found my fuel manifold from when I first made the engine and removed the smaller injectors , holes drilled out for the 16G needles I now need .
Will go and get some stainless for new NGV vanes and some good silver solder for the injectors.
Cheers
John
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Post by racket on Aug 8, 2024 2:34:54 GMT -5
Hi Guys
New injectors fitted to the fuel manifold and mounted on the front of the flametube , made a mess of them on the first attempt and had to extract them all and do it again .
13 of the required 18 NGV vanes have had their tapered section milled, I finish the others tomorrow , this 316 stainless is a slow job :-(
Cheers
John
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Post by racket on Aug 11, 2024 1:38:31 GMT -5
Hi Guys
NGV vanes all finished, massaged into shape , a bit of a strange double curve so as to try and get the correct throat area and angle .
Welding tomorrow , shouldn't take long , then a grind to finished width and diameter so that it fits up into the recess on the back wall of the NGV .
Hopefully the circumferential alignment holes will save me having to adjust the ignitor position .
Once the NGV is back together its just a quick reassembly of the engine :-)
Cheers
John
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Post by racket on Aug 12, 2024 3:52:32 GMT -5
Hi Guys A few pics of the NGV design , its all together and waiting for me to finish a couple of other jobs before I reassemble the engine .     Cheers John |
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Post by andym on Aug 12, 2024 7:47:21 GMT -5
Looking good, will be interested.... might have to copy you in the new engine
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Post by racket on Aug 12, 2024 16:55:55 GMT -5
Hi Andy
LOL........hopefully the mods will have a positive outcome ..........otherwise , just another dead end .
Throats set to 9mm X 24.5mm X 18 of
Back to the shed today for another busy day , its an absolute shambles with dirty machines, tools everywhere along with engine parts , more like a farmers shed than an aerospace assembly area ;-)
Cheers
John
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Post by racket on Aug 13, 2024 21:28:39 GMT -5
Hi Guys
All back on the test stand , its been a bit of a job , hopefully some good results , LOL...............sorta gone full circle , back with my bent tip injectors in the flametube front wall , getting the fuel manifold mounted on this latter model flametube meant some compromises, but everything seems to look OK .
I'll spend a couple of days tidying up the workshop and think about doing a testrun on the weekend :-)
Cheers
John
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