11/127 manned flight engine.

[racket]

Hi Mark

I might take you up on the offer :-)

What sort of coupling did you use at the engine ??

I've been thinking some sort of hydraulic quick connect , I'll fit a 1/4 BSP thread into the housing .

Cheers
John

[pitciblackscotland]

Hi John,
I didn't use a coupling just screw in the fitting to the engine. This 24 volt valve is NOS i cannot remember if it is a open or close valve. I'll see if a have a female plug for it, if not you can unscrew the plug port and solder a switch onto the wires. This valve will give you a instant 3,000 pis air pressure to start your engine if that's what you want When i start the JFS i just switch on oil pump, then fuel pump and soon as i see a flame come out of the exhaust i flick the air valve switch and she starts I'll pop over to the workshop tomorrow and see what i have in the parts inventory.

Cheers,
Mark.

www.youtube.com/watch?v=bi6FamS5aG8

[racket]

Hi Mark

I've been having a think on it and I'm not sure if it'll be OK to have instant 3,000 psi with such a heavy rotor and a left hand thread on the comp , the comp will be powering the turbine wheel initially and would be trying to undo the nut .

Maybe a manual opening of the scuba tank will provide a "soft start" , your JFS was virtually instant start , but I've got a 5 kg rotor , its gunna take/need time to accelerate if I don't want to "overload" anything .

Your thoughts

Cheers
John

[pitciblackscotland]

Hi John,
Yeah i had a think about it and check on some photos of the JFS, as you can see there are 4 x small tubes coming out of a larger tube and angled at the turbine wheel, so maybe that's to spread out the high pressure air on the turbine wheel I was thinking to use the 24 volt valve on the JU-1 engine,but there is only one tube angled at the turbine wheel, so i will go with a manual opening. Now having a look at the GTC20 turbine engine,it has a electric valve i think it's set at 140 psi. OK manual opening it is, i have some of them will get them out and send you photos of what i have

Cheers,
Mark.

[dieselguy86]

Hi John,

Was scrolling through one of the new books Chris mentioned and came across pinch. If I understand it correctly, it organizes the flow some before heading into the diffuser channels. I'm just curious how you settled on 2mm of pinch, calculated design, or calculated guess lol.
I'm wondering if it's something I should add into my design.

-Joe

[racket]

Hi Joe

As I like a generous vaneless space between comp exducer and diffuser vane tip , theres considerable diffusion in that vaneless space , this would normally mean the radial velocity component of the outflow would be reduced leading to a longer path for the gases with greater losses , the solution is to "pinch" , this then keeps the radial component at the "same" level and as the whirl component decreases with increase in radius , the resulting air flow is at a "higher" angle , shortening the flow path especially at the higher PRs where densities are high .

LOL........calculated guess, with calcs to verify :-)

As for whether or not it needs to be a consideration in the design , it'll depend on the tip height of the exducer , my comp has a relatively generous tip height so I felt a bit of pinch was in order .

Cheers
John

[racket]

Hi Guys

Got the main bits roughly bolted together


Comp cover , diffuser , shaft tunnel and NGV , weighs in at 9.8 kgs 21.5 lbs .

One happy ol' fart



Still plenty to do , but working through them

Cheers
John

[madpatty]

That’s a beautiful beast of a machine you are building John.
The bare metal look is almost unbeatable.

Cheers.

[wannabebuilderuk]

Jesus now we have a john-for-scale™ I see how big it really is.. Can't wait to hear it spool up ha

[racket]

Thanks guys :-)

Its starting to look like an engine , and most of my concerns are fading away .

Cheers
John

[racket]

Hi Guys

Finally got the lube drain bits made so thought I'd checkout how the flametube will sit over it .

With 35 mm packers under the front wall of the flametube theres ~5-6 mm clearance between the drain and the fuel manifold ...............35 mm is a fair bit of gap between diffuser wall and front wall of flametube representing some "lost" axial length for the flametube


But even with this much gap it appears as though the flametube outer wall will be ~150 mm long and the shorter inner wall of the main combustion section will be ~90 mm long , which is pretty good and represents an ~1.5:1 length/width ratio , considerably better than the 12/118 engines







Cheers
John

[jetjeff]

Hi John,

Looking great so far. Are there any regulations regarding homebuilt power plants in OZ? Any thoughts as to what kind of airframe this will go into (ultralight, BD5-J)?

Regards

Jeff

[racket]

Hi Jeff

It'd be for Experimental Class which is somewhat "relaxed" with regards regulation.

At this stage some guys want to fit it to self launch a glider , but theres talk of a more speedy airframe like the BD5.

20 years ago a guy contacted me about an engine for his BD5 kit but I had to tell him it wasn't possible as suitable comp/turb weren't available in a large enough size, now they are with marine turbos running 5.8:1 PRs as a common thing for thousands of hours between overhauls

Cheers
John

[racket]

Hi Guys

Flametube finished , 2.17 kgs - 4.75 lbs , 550 holes , some drilled 3 times , most twice , with all edges chamfered , they'res bit of stainless chips everywhere , including in my fingers

But it looks OK and I'm happy with the result , half way through it looked like there were too many holes with too much area , so went back and rechecked all the numbers and theres 12,900 sq mms of hole area , same as the inducer.








The job list is getting smaller

Cheers
John

[wannabebuilderuk]

One hell of a lampshade there 😂