11/127 manned flight engine.

[racket]

Hi Guys

Testrun this arvo , things survived , not much different than previous test

youtu.be/DMTVEmxeRfQ

youtu.be/uLhqQwhup0I

youtu.be/An7DK0iwaY8

Cheers
John

[racket]

Hi Guys

Some numbers from the last test




The static pressures at the NGV throat exits are " interesting" , it appears as though theres only around a 1.55 PR across the NGV , the rest of the choking is in the vaneless space between throat and inducer .

I've been doing some calcs based on centrif comp calcs and working with a 2,000 ft/sec exit velocity from the comp at a 75 mm radius and seeing how the velocities and densities change as we go " out" to an 85 mm " diffuser" throat radius , I got a pressure ratio increase of ~1.3 , which if used in conjunction with my 1.55 through the NGV would produce a choked flow .............they're only rough calcs etc but it might help explain whats happening .

Cheers
John

[racket]

Hi Guys

Finally got back in my shed :-)

Engine pulled apart , a bit of minor NGV damage , but OK .

NGV throats increased to 12mm from 9.5 mm , but then found the outlet tips were getting too close to the turb inducer so had to set the NGV up in the mill and grind the tips all back by a few mms .

The engines bellmouth is soaking in kero overnight to soften the silicone used to hold the IGV stator in place as I want to remove it for future testing/development , no point holding things back , time for more radical approaches to getting the engine sorted .

Hopefully back together in a few days and ready for testing ............I'd like to only run her up to 4:1 PR at ~57,000 RPM , there'll be a bit of a drop in pressure energy in the jetpipe but hopefully the mass flow increase will more than compensate when making thrust .

Cheers
John

[racket]

Hi Guys

Engine back together , hopefully remounted on the test stand tomorrow ............a topup of the fuel drum and I'll be ready to test :-)

NGV throats are back where they were 2.5 years ago , same with the turb clipping , just the increase in exducer clearance a difference , so I'll have some numbers to compare with.

Cheers
John

[ripp]

Sept 4, 2024 3:47:30 GMT -5 racket said:

Hi Guys

Engine back together , hopefully remounted on the test stand tomorrow ............a topup of the fuel drum and I'll be ready to test :-)

NGV throats are back where they were 2.5 years ago , same with the turb clipping , just the increase in exducer clearance a difference , so I'll have some numbers to compare with.

Cheers
John

Hi John,

That means you have a new turbine wheel?

Cheers
Ralph

[ripp]

Sept 3, 2024 4:12:39 GMT -5 racket said:

Hi Guys

Finally got back in my shed :-)

Engine pulled apart , a bit of minor NGV damage , but OK .

NGV throats increased to 12mm from 9.5 mm , but then found the outlet tips were getting too close to the turb inducer so had to set the NGV up in the mill and grind the tips all back by a few mms .

The engines bellmouth is soaking in kero overnight to soften the silicone used to hold the IGV stator in place as I want to remove it for future testing/development , no point holding things back , time for more radical approaches to getting the engine sorted .

Hopefully back together in a few days and ready for testing ............I'd like to only run her up to 4:1 PR at ~57,000 RPM , there'll be a bit of a drop in pressure energy in the jetpipe but hopefully the mass flow increase will more than compensate when making thrust .

Cheers
John

I am very excited to see in which direction you will develop it further.

Cheers
Ralph

[racket]

Hi Ralph

Nope , no new turbine wheel , just this rather "worn" one with half its inducer tips missing .

The new direction is to let the compressor wheel flow what it wants to flow and "adjust" the hot end flow , for some unknown reason the NGV throat area isn't behaving according to the theory , so I'll keep opening it up to increase flow whilst still keeping it choked by increasing the exducer clearances until my temperatures dictate differently .

I don't know if it'll make any difference but I've got to try something as "standard" techniques aren't producing the required results .

I'm planning on a test run on Sunday as the weather should be OK :-)

I'll post the resulting "numbers" .

Cheers
John

[madpatty]

Sept 6, 2024 4:24:34 GMT -5 racket said:

Hi Ralph

Nope , no new turbine wheel , just this rather "worn" one with half its inducer tips missing .

The new direction is to let the compressor wheel flow what it wants to flow and "adjust" the hot end flow , for some unknown reason the NGV throat area isn't behaving according to the theory , so I'll keep opening it up to increase flow whilst still keeping it choked by increasing the exducer clearances until my temperatures dictate differently .

I don't know if it'll make any difference but I've got to try something as "standard" techniques aren't producing the required results .

I'm planning on a test run on Sunday as the weather should be OK :-)

I'll post the resulting "numbers" .

Cheers
John

Reminds me of when I was experimenting with HX35 with its “comparative to compressor” undersized turbine wheel. None of the theory made sense.

Seems like these modern compressors just want to flow a lot more.

Hoping to see the Sunday test run produces an understandable trend.

Cheers.
Patty

[racket]

Hi Patty

Yep , in the "old days" we could use a ratio of 12 lbs/minute/sq inch of inducer , but now some of the newer ones are up at 15-17 lbs, but it creates problems with turbine sizing for a gas turbine engine , but OK when used on an automotive turbo as the pistons can force the gases through at higher than P2 pressures , but a gas turbine will need a turbine wheel that will run into tip speed problems at high P2s from the comp .

Hopefully I'll find a solution :-)

I'll keep you posted

Cheers
John

[racket]

youtu.be/tbxl1SjOm3U

[racket]

Hi Guys

Todays test was a bit of an ordeal :-(

Couldn't get ignition to start with , fuel spewing out the rear end , starter getting hot and batteries fading , gave things a bit of time and eventually got a spoolup on the third attempt , but it was slow and labored needing a lot of extra fuel/temps to get over the hump , and the 1 Bar idling temps were rather high and didn't improve as P2 was increased .

Thrust at 3 Bar was 182 lbs , way better than the 130 lbs during last test , but at the expense of high temps .

My manometer readings weren't very good , the red surge slot dump pressure initially dropping as P2 increased , but then increased again as we progressed towards 3 Bar even though the green comp inlet vacuum was only steadily increasing .

Interestingly there wasn't any "chuffing" despite the removal of the IGV stator , so comp was a bit "happier??" from the extra mass flows.

I'll need a couple of days to digest things and hopefully come to some conclusions

Cheers
John

[racket]

Hi Guys

Conclusion .............gotta change turbine wheel to something bigger :-(

The current , no IGV stator, green manometer suction reading of just 850 mm of H2O or ~1.2 psi , means a velocity of ~400 ft/sec into the comp inducer annulus and a flow of ~3.5 lbs/sec at 3 Bar P2 and 57,000 rpm , this is too low .

The red manometer has a minimal pressure reading of 180mm of H2O at 2 Bar P2 but then increases to 350 mm at 3 Bar as rpm go from 48 to 57,000 rpm , the comp is biting off more air as per the green manometer readings but more of it is being dumped out of the surge slot rather than going through the engine .

The NGV throat outlet static pressures have been fairly close between this test and the previous one despite a lot more air/gases going through them given an increase in throats from 9.5 mm to 12 mm , at 2 Bar P2 both tests produced a P3.5s of 0.85 Bar , at 3 Bar it was 1.5 Bar this test and 1.45 Bar on the previous test , close enough :-)

Thrust outputs changed a lot , 182 lbss vs 130 lbs previously , but when taking temperatures and P4t pressure differences into account , 0.5 Bar this test and only 0.35 Bar previously , actual mass flow only changed from 3.3 lbs/sec previously to the current 3.5 lbs/sec , despite a 26% increase in NGV throat areas .

Without the IGV stator the spoolup is more difficult if I want to flow "unrestricted" , sorta pointing to a comp wheel suitable for having P2 bleed air once up to speed , but thats not what I'm trying to achieve , so I need to redesign .

I've got some Allison C20 3rd stage turb wheels that I might try using , I have a C28 wheel as well with 14 sq ins of flow area through its 40 blades , but they're less common so I'd like to use the C20 with its 30 blades but less flow area , well it might have a tad more after I grind some of the blade outlet away ............LOL, I like clipping wheels , never done an axial wheel before though , so something new to do , will probably remove the laby seal at the tip to reduce stress on the blades which will be severely over spun , I might install water cooling to the disc rim to increase tensile strength so it'll cope.

The 3rd stage wheel will end up at ~180 mm dia , a tad larger than the comp at 175 mm , but the extra blade speed will produce more torque/HP for powering the comp .

I'd like to use the same cold end of the engine and simply lengthen the shaft tunnel to accommodate the new shafting whilst running on my "brass" bearings which have given no troubles what so ever .

Best thing will be ...........a longer flametube , something closer to "normal" gas turbine proportions rather than my fat doughnuts :-)

Cheers
John.

[enginewhisperer]

I was thinking why not run a P2 bleed into the afterburner, until I got to the middle of the post...

An axial wheel and longer flame tube could definitely be a nice combo if the numbers all stack up at least!

[madpatty]

Hi Racket.
It would be interesting to see the axial turbine wheel being used.

The best part about using them apart from a longer flametube would be custom made, thicker in the middle, shaft to give you even better and Robust rotor dynamics (not that it was an issue with journals but still).

Cheers and good luck.
Patty

[racket]

Hi Guys

Spent the day trying to cobble together a turb wheel from a C20 third stage freepower one , not a lot of success getting the extra flow area as the original design of the C20 wheel was meant to extract power rather than produce free flowing passageways .

I cut off the curvic coupling and odd overhung mounting that has always been a problem in the C20 , then starting clipping back the outlet side of the blades to open up the "throats" , but needed a lot of grinding

The labyrinth tip seal was an easier job to remove , wheel is 180 mm at tip and 116mm at root .

I'm waiting on some Dremel grinding stones to clean things up , lotsa sharp edges

A few pics







Cheers
John