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Post by racket on Feb 18, 2022 16:47:21 GMT -5
LOL......lets hope those ideas come to pass :-)
The experimental class has cost constraints , so simple/cheap will have more appeal , as for unmanned usage , its a crowded marketplace already , plenty of research required before spending too much cash .
Cheers John
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Post by racket on Feb 17, 2022 22:09:22 GMT -5
Yep , they were/are a nice little engine with a lot of development put into them over the years .
They're probably a bit too complicated for general aviation , but OK for military use , complication equals cost unfortunately .
It would depend on what you see as their potential end use though
Cheers John
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Post by racket on Feb 16, 2022 16:15:09 GMT -5
Hi
Larger flow at a lower pressure ratio but with the same power requirement , the LP turbine RPM would need different gearing to match the larger fan , things get difficult once we start trying to modify a design , we basically need to redesign the whole stage .
The original engine had a job to do within certain parameters , you want to change "the job" , so a rethink on the entire engine required , a pretty big , and expensive, task especially if you want to get it Certified for GA use
Cheers John
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Post by racket on Feb 15, 2022 17:04:18 GMT -5
Hi
You'd need to increase the fan contribution to thust , a >3:1 bypass ratio , you won't be making a missile engine , you'll be be making a "slower" engine , so greater mass flow at a lower fan pressure ratio
Cheers John
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Post by racket on Feb 14, 2022 16:21:57 GMT -5
Hi Andym
OOPS , missed your email :-(
I'll be here for a chat
Cheers John
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Post by racket on Feb 14, 2022 16:20:13 GMT -5
Hi Richard
Yep , those 900C temps are high , but I think they're more from jetpipe combustion as the wheel colour doesn't indicate the same level .
Flametube combustion is still displaced too far down it , the new flametube design with better hole placement and front wall thimbles should bring that much closer to the front wall as it did with the 12/118 engine .
Cheers John
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Post by racket on Feb 13, 2022 18:50:24 GMT -5
Hi Andy
Yes much improved , temps are still high because of the delayed combustion , but thats not such a problem now .
Interestingly there was more needle bouncing from the P4t gauge than the P2 gauge, maybe the jetpipe combustion was causing that
LOL.....does 3 passes with the 4mm drill make a 12mm hole ;-)
I've got a 500kg load cell available , just need to workout how to get it hooked up to a computor , I'll be needing it once the A/B is fired up .
Cheers John
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Post by racket on Feb 13, 2022 18:44:43 GMT -5
Try a fuel mix with 50/50 petrol/kero , plus oil ............the increased volatiles might help ...........they do with my engine :-)
3 psi P2 is still a fairly low power setting , is there any way you can increase your starter contribution until at least 5 or 7 psi is obtained .
Cheers John
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Post by racket on Feb 13, 2022 0:25:55 GMT -5
Hi Mark
Yep , sure did , well onto a second go around the dial , LOL, I couldn't find the needle the first time I looked , I wasn't expecting that much increase in thrust :-)
I've pulled the engine apart and alls well inside , still the original soot on the front wall and not much combustion happening any earlier than before , the evap tubes have a tad of "colour" .
Good to see 55,000 on the tach , so a tip speed ~1640 ft/sec , my "design " 1700 ft/sec if we use tip speed squared for increasing P2 it should give another 7.4% ,1.074 X 3.75 = 4.02 PR ,.......just right :-)
I'll make a new flametube thats more sympathetic towards the evap tube placement , currently a number of tubes have "cold" air blowing onto them , it'll also have the "thimbles" in the front wall to get air and fuel mixing earlier , I'll have a think on the thimble desiogn to see if I can make something thats easier to manufacture .
I think I can call it a successful testrun, a few more steps forward towards her 250 lbs of dry thrust, she's rumbling nicely .
Cheers John
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Post by racket on Feb 12, 2022 21:37:33 GMT -5
Don't change flametube holes just yet .
What fuel are you using ??
Cheers John
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Post by racket on Feb 12, 2022 20:49:41 GMT -5
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Post by racket on Feb 11, 2022 16:08:39 GMT -5
Hi Chris
The fuel manifold is made from 5/16" steel bundy tube( brake line) , ID is 6.8 mm , supply line to the manifold Tee piece is 1/4" OD bundy tube , all entries to injectors are positioned on the downstream side of flow in the manifold to minimise flow variations
I'm keen to see how it performs with the mods, hopefully the pulsing will subside and I'll get her up to at least a 4:1 PR and some serious thrust levels :-)
Cheers John
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Post by racket on Feb 10, 2022 23:38:17 GMT -5
Hi Guys The 18G syringes finally arrived in the Post A pretty simply job to grind back the sharp point by about half, clean the bore with an oxy torch tip cleaner and gently tap the syringe through the slight inference 1.25 mm hole in the manifold , and with compressed air being fed into the manifold the Dremel cutoff disc took care of removing the plastic bit, a bit more emery to take off the rough edges and another clean of the bore with the tip cleaner and one injector in place. A dob of 45% silver content silver solder on each to seal and hold them and the job was done With the manifold fitted to the engine along with a propane preheat manifold it was time to fit the outer can The engine is now mounted back on the test stand Test run next week Cheers John
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Post by racket on Feb 8, 2022 19:05:50 GMT -5
Hi Guys Bit of an update . Almost ready to put the engine back together , just waiting on the new 18G syringe needles to arrive in the Post , hopefully this week . Fuel manifold made along with propane preheat manifold feeding several evap tubes on the ignitor side of the engine , I'll try to fire her up without the preheat , but if it doesn't ignite, I can feed in some propane . Flametube front wall has a cover plate fitted over it, hopefully it won't leak fuel too readily, its only a temporary measure , a new flametube will be made if combustion is OK and the pulsing ceases . Maybe a testrun next week where I can also measure static air pressure just forward of the comp inducer , I drilled a 1.1mm hole through the alloy housing which I can slide a 19G syringe needle into to pickup the pressure . Cheers John
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Post by racket on Feb 5, 2022 20:48:14 GMT -5
Hi Scott
Gotta have swing for our sorta work , we might start off thinking the lathe is too big , but it can become too small eventually :-(
Cheers John
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