11/127 manned flight engine.

[racket]

Hi Guys

Started pulling CHRA apart .

The left hand nut needed ~70 ft lbs of torque to crack it , then a bit of comp warming and it slid off OK

A large circlip holding "the guts" in place


The comp piston ring holder was easily removed with a bit of gentle prying



The main clamping piece that the circlip held in place was a bit harder to remove as it has a large O'ring sealing its outer wall



This revealed a lube deflector shield which once removed exposed the thrust washer and bronze thrust bearing which is pinned for location



The bronze thrust bearing didn't want to move off its locating pin but a bit of gentle pushing with a length of alloy drift through the tunnel and some wobbling of the plate had it coming out.

Then a case of removing the other thrust washer



Then into the brass bushes , the comp one was easy as the thrust washer kept it in place , but the turb end needed the circlips removing



Oil to the thrust bearing is via the hole near the locating pin .

I slipped on the KTS 130/180mm comp to see what it'd look like



And finally I needed to measure up the max distance between comp and turb wheels with a view to flametube possible length




Turbine wheel/shaft weighs in at ~3100 grams , the comp wheel at ~1100 grams , a 4200 gram rotative , kinda heavy , it won't be a fast acceleration of the rotor .

The thrust bearing is interesting in that it has different diameter thrust lands from one side to the other , the main "forward" load is much bigger than the "bump" bearing .

Now I need to measure everything accurately and figure out how to "modify" the thrust bearing mounting into my engine design , I'd like to move the comp as far forward on the shaft as possible to increase flametube length

Cheers
John

[madpatty]

Hi Racket.

This CHRA looks strikingly similar to the holset CHRAs I have worked with over the years, especially smaller HX35 and HX40 ones.
Really simple and easy to replicate.

The distance between compressor and turbine is what. 170mm approx?

Cheers.
Patty

[racket]

Hi Patty

Maybe 150-160 mm , but should allow a flametube at least 30-40% longer than the one I used in the 12/118 engine which will hopefully simplify combustion by providing a better L/W ratio for the annulus .

Cheers
John

[racket]

Hi Guys

A few pics of the diffuser .

Setting out the spacing and angles





Glueing on the diffuser wedges , 13 of with an 18 degree wedge centre line at 24 degrees above tangent , wedges have a 2 degree release angle on their sides



Still waiting on the chinese comp wheels to be shipped , so making the diffuser for the high pressure KTS 130/180 wheel

Cheers
John

[slittlewing]

Hi John,

Looking good!! How did you decide on the angles and spacing for the diffuser? I know it needs a different number of wedges to the number of comp blades to avoid harmonic issues but that’s all 😂

Will you cast this at home?


Cheers

Scott

[racket]

Hi Scott

Theres a bit involved with getting the air angle at the diffuser vane tip , theres considerable diffusion in the vaneless space between exducer and vane tip , so speeds drop and angles change depending on the height of the vane and the available cross sectional area , things can be "fiddled" a tad to achieve desired outcomes , I'm hopefull that by adjusting the vane heights I can use the same diffuser for both the KTS and Chinese wheels at their different Pressure Ratios and RPM tip speeds .

I chose 13 vanes as it worked OK with the 12/118 engine and will be useable with either a 14 or 16 bladed comp wheel .

I'll send the patterns down to my fellow collaberator Andrew in Melbourne who gets them professionally cast and heat treated in a tough alloy .

Cheers
John

[racket]

Hi Guys

The diffuser is finished and ready to be packaged up and sent off for castings to be made :-)

Looks "just right" with the 130/180 wheel sitting inside it .





It takes twice as long to make the patterns as machining the castings

Cheers
John

[pitciblackscotland]

Hi John,
Diffuser looking good Are you going to cast the NGV part this time?

Cheers,
Mark.

[racket]

Hi Mark

I'd love a cast NGV , but Andrew tried to get one done for me years ago and wasn't able to , might need to ask him again , it was more than a decade ago , it'd save a couple of weeks work carving away a big lump of stainless, I think I still have some suitably shaped timber for the vanes from last time .

Cheers
John

[slittlewing]

The diffuser is looking great John 👍👍
Nice that it can be tailored to be used with either comp wheel spec too.

Cheers
Scott

[racket]

Hi Guys

I've been attempting to get my shaft tunnel worked out , so made up a wooden dummy to see how things would fit , my current 85mm dia is a tad too small , looks like 89 mm required so that theres enough space available .


Then it was the turn of getting the length "just right" , 106.5 mm seems to be whats needed



This give enough distance between shaft tunnel and turbine wheel for mounting the NGV with its piston ring seal shroud



Now all I need is a chunk of 90 mm alloy round bar

Cheers
John

[racket]

Hi Guys

LOL.......I'm getting enthusiastic about the build so decided to tackle the turb exducer mods .

Original exducer tip angle was a very shallow 25 degrees , great for extracting every last bit of energy from the diesels exhaust but not necessary for a jet engine where the extra flow area from the clipping means more mass flow and thrust .

The 25 degree exducer gave ~7.46 sq ins of flow area , at 40 degrees its now ~10.2 sq ins , a 37% increase , 40 degrees is what our TV94 turb wheel exducers are at , the G Trim turb wheel in the 12/118 ( thanks Monty ) has an area of ~7.86 sq ins and I was able to get ~195 lbs of thrust out of it , with ~30% more exducer flow area , 250 lbs might be worth aiming for

A few pics of the "dirty job" , a couple of hours work slowly taking off 0.015" per cut







Cheers
John

[dieselguy86]

John,

I can feel the grit in my eyes and teeth just looking at those pics lol.

[pitciblackscotland]

Hi John,
Thanks for showing your work I'm trying to send you a email but not working at the moment regarding alloy round bar, i have some if you want

Cheers,

Mark.

[racket]

Hi Joe

Yep , lotsa grit and the stink of the side grinder wheel , gets everywhere :-(

Cheers
John