11/127 manned flight engine.

[racket]

Hi Guys

Did a test run today with a couple of mods from the last test , I shimmed the turb exducer clearance back closer to normal and fitted longer fuel injectors to displace the spray from hitting the front wall .

Spoolup was better from the exducer doing more work , but combustion was horrible with flames out of the turbine from low power to higher powers .............the combustor isn't long enough to cope with even a small increase of ~10mm in the rearward placement of the injectors.

The only positive was the poor combustion , it finally showed just how marginal things have been and might account for a lot of my temperature problems in the past .

LOL..............the more I think about it the more I'm convinced I'll never get this comp wheel tamed with my current setup .

Cheers
John

[racket]

Hi Guys

Engine is pulled apart in preparation for conversion to an axial turb wheel.

The front end should be OK , so just the shaft tunnel , flametube and hot section to work on .............no hurry , so I'll go at it one job at a time , considering I've wasted 2 years going around in circles with this comp wheel , it might be the quickest solution :-)

LOL , maybe I should start a new Build Thread so that I can leave all my failures behind .

Cheers
John

[racket]

Some video of the last test run youtu.be/wceij2fhsMI

[praendy2203]

Hi John,

it would be awesome to see the build with an axial turbine wheel.

How much rpm the wheel 180mm is able to run?

I think on my "little" 130mm wheel.
The rpm restriction is 70 000.

Whatever, I would try to run an axial one👍👍👍

Andy

[racket]

Hi Andy

I was thinking ~57,000 rpm so as to get 3 Bar from the comp .

This represents a pretty fast blade speed for the wheel unfortunately :-(

I was thinking of a bit of water cooling of the turb disc rim to maintain high tensile strength from low metal temps.

I've been trying to get some idea of how to fit things together , but am running into problems when I look at what my machinery can do , the parts are getting pretty long which would mean precision alignment of components is an issue .

I'll keep thinking on it but if it doesn't look like a reasonable build I won't attempt it .

Cheers
John

[racket]

Hi Guys

Scrapped the axial route , too many problems for me to overcome , so have cobbled the engine back together with a new flametube , that has air entry caps on the front wall which are made in thicker material and mounted in a 2mm thick wall so shouldn't end up with FOD this time , evap tubes refitted , and some changes to Zone spacing to get more tertiary length .

Afterburner has been repaired with a diffuser cone at entry along with a set of three flameholders to supplement the reduced width dump .

The extra length on the diffuser meant my sparkplug lead wasn't long enough , so I went off to purchase a few feet of copper core lead ...............PROBLEM , can't buy it anymore , bummer , so had to join on a short length to the old lead with a bit of rubber hose over the soldered joint ...............seems to work

A few pics of the A/B additions , please excuse the crap welding , I tried using my MIG welder , its been sitting in a box in my shed for >12 years and thought it might make an easier job of the sheet metal welds ............didn't , now I know why I went to TIG , used it on the main joint of A/B outer can and the front wall cap ...............wished I'd used it for the rest , the MIG is back in its box and on the shelf never to be used again .











Cheers
John

[enginewhisperer]

that's similar to my general MIG vs TIG experience!
I always TIG welded stuff that people said I should be MIG welding - but it always worked well for me even if it maybe took a bit longer.

More recently I did buy a tiny inverter MIG though which is handy sometimes for fixing outdoor stuff like gates or tacking parts for trailer repairs etc.

[racket]

Hi Andrew

Yep , I agree , my MIG is a UNIMIG 120 Amp unit , made in Italy , cost me a fair bit 15 years or so ago , I doubt its had more than a couple of hours work, still in shiny condition , but I guess I shouldn't blame my tools , I'm just a crap welder , hands too shaky these days and I can never seem to be able to see what I'm trying to weld , tried adjusting all the knobs in the helmet to no avail :-(

Cheers
John

[enginewhisperer]

MIG is meant to be the super easy "glue gun" of welders, but I never found it very easy to get good welds.
The MIG controls are also not super easy to dial in I found.
My Unimig Viper 120 only has one knob and a wire thickness setting. It seems to be much easier than the other MIGs I've tried, but still doesn't get much use!

[Johansson]

Stick welding stainless is really fun once you get the hang of it, I prefer a stick welder over a MIG every day. TIG is the king of welding machines though.

[slittlewing]

Nice little detail on the “fillets” for the centre of the flame holder 😊

[racket]

Hi Scott

LOL..............a bit of a "dogs breakfast", hopefully it'll work OK .

The diffuser cone project an inch inside the A/B endwall and the V gutters are slotted into the projection so they connect with the dump section of flameholder which is now only ~1.5 inches wide.

Hopefully a test soon , everything is ready , just waiting on a cloudy day for better video, warm and sunny today , but forecasts look promising :-)

Cheers
John

[racket]

Hi Guys

Was able to do a test run yesterday and she fired up OK, and after a quick spoolup I thought "this is encouraging" , but temps were still way too high :-(

Did a few runs up to higher P2s but things only got worse.

So decided to see if the A/B would fire up , not a problem :-) ..................one win ......, but by this time the fuel drum was getting kinda empty and air was being sucked , but at least a couple more A/B ignitions were successful.

Pulled the engine apart to have a look inside and late combustion was obvious from the flametube colouration patterns , reusing the old evap tubes which had previously been cut off and were shorter than ideal wasn't a good idea , gotta make new ones .

But the engine did survive and will be tested again with a full tank of fuel next time :-)

I'll get some pics today and Post

Cheers
John

[racket]

Hi Guys

A few pics of the flametube

Outer wall indicating combustion not starting until the Secondary Zone



Inner wall a bit better



Front wall still not hot enough



Cheers
John

[racket]

A bit of video , nothing spectacular

youtu.be/K-U18X-Dn0A