11/127 manned flight engine.

[racket]

Hi Scott

Yep , things are still progressing , once we get up to this size the bits gets harder to find , the KTS wheel isn't suitable for a "normal" engine because of its configuration for tractor pulling , so it'll require a "special" engine build , whereas the other comp should be "just right" hopefully , will need to wait until its "in the hand" and I can measure everything up .

The original Chinese quote for the 10 wheels was "wrong", someone stuffed up the sizing ,mistake only found when the order went to manufacturing dept., the redone quote is more "realistic" and there are 2 wheels coming for evaluation , still at a very competative price compared to KTS ones , and I feel might actually have better configuration as its a "normal" turbo comp meant for a big diesel engine , rather than a race engine , so hopefully better at a normal PR of ~4:1 , rather than 90 psi of boost on a tractor puller, its all to do with the exducer tip height and in/out area ratio of the wheel .

More updates as things arrive :-)

Cheers
John

[racket]

Hi Guys

A few pics of the KTS wheel









Cheers
John

[finiteparts]

Practically a GTCP85 impeller! Nice find!

[turboron]

John, I am confused. I understood you to say on your March 25 post that you were on going with a KTS impeller.

Thanks, Ron

[racket]

Hi Ron

The KTS wheel I was looking at using was simply too expensive , so had to go looking elsewhere :-(

The KTS wheel I did purchase was considerably cheaper but isn't "right" for a flight engine

Cheers
John

[racket]

Hi Ron

Further to my earlier email ................the way KTS measures their tip heights is different to the usual Garrett way which is the actual passageway height , KTS measures from the back of the wheel to the shroud surface which invariably means a "bigger" tip height by a couple of millimeters , unfortunately this distorts the inlet/outlet area ratio of the wheel and along with that the diffusion within the wheel and the radial outlet air speed and the approach angle to the diffuser vanes .

The wheel I was intending to use is advertised as having an 11mm tip height, but instead it'd be closer to 9mm passageway height , at 11mm the in/out ratio is a"normal" 2.09 :1 ratio , but at 9mm is a highish 2.56 :1 .

It would appear the KTS wheels are all for tractor pulling running very high pressure ratios with vaneless diffusered turbos .

Hopefully the Chinese wheels are standard diesel turbo types with normal in/out ratios suitable for vaned diffusers and potentially higher efficiencies .

LOL...............R&D gets expensive when parts don't turn out suitable :-( ................but the experience gained is "valuable" :-)

Cheers
John

[turboron]

John, thanks. I have one KTS impeller which I have successfully tested. I set the shroud clearance used your masking tape method so I did not pick up the difference in the tip height dimensioning difference.

Thanks again, Ron

[racket]

Hi Ron

The specs given for the 130/180 wheel www.ebay.com/itm/MAMBA-Billet-Turbo-Compressor-Wheel-Mitsubishi-TF15-130-180-7-7-/264350238104 indicate an 8.43mm tip height which was going to be a tad small , but when I measure it , the actual passageway height is a rather small ~6.7mm , the rear wall of the wheel is ~1.8mm thick.

The resulting in/out area ratio is a very high 3.5:1 , this wheel is made for a very high PR useage where the greater density exiting the wheel will reduce the radial velocity and produce more "normal" velocity triangles from the wheel , I might need to explore the comp wheels advertised "70 psi of boost" potential with a special engine .

Cheers
John

[turboron]

John, 70 psi boost is a 5.8 pressure ratio. Do you think you will need a Titanium impeller or a solid impeller(no shaft bore) to handle the stress? Allison's 6.0 and 10.0 pressure ratio impellers are both Titanium and solid. An aluminum forging may be okay short term. Aluminum may be questionable for a higher cycle application.

Thanks, Ron

[racket]

Hi Ron

This would be for short duration use , seconds not minutes/hours.................LOL, I couldn't afford the fuel bill :-)

ABB use comp rear wall bleed air cooling on their high pressure marine turbos to allow the use of alloy wheels , for short duration use I could even use water spray , either externally or internally , I've even considered water for the turbine wheel to keep its hub temp down at the higher rpm.

This would be an engine for exploring "new frontiers" ;-)

Cheers
John

[madpatty]

Apr 1, 2021 16:22:37 GMT -5 racket said:

Hi Ron

This would be for short duration use , seconds not minutes/hours.................LOL, I couldn't afford the fuel bill :-)

ABB use comp rear wall bleed air cooling on their high pressure marine turbos to allow the use of alloy wheels , for short duration use I could even use water spray , either externally or internally , I've even considered water for the turbine wheel to keep its hub temp down at the higher rpm.

This would be an engine for exploring "new frontiers" ;-)

Cheers
John

Hi Racket.
Interesting.
I am wondering from where do ABB get cooling air for compressor wheels.

Regards

[racket]

Hi Patty

They simply bleed off P2 air thats on its way to the diesel engine inlet after the intercooler, then plumb it to the backside of the comp wheel where the static pressure is lower than P2 air , the cooled air removes heat from the wheel and simply passes out with the comp discharge air to the engine , so no loss of mass flow , but a very slight loss in comp effic . ............simple arrangement :-)

Theres an ABB Paper on it .

Cheers
John

[slittlewing]

Hi John,

Interesting reading, but I’m slightly more confused than normal! Am I understanding this correctly 😂

You mentioned the in/out ratio specs of the kts comp wheel you purchased ended up at 2.56:1 due to the way they measure the passageway. This was higher than expected/desired, and this wheel was therefore made for tractor pulling at high PR which meant low efficiency at lower PR. So you were hoping for more normal proportions from the cheaper mamba wheel.

But then after finding the cheaper mamba wheel has an even higher still in/out ratio of 3.5:1 (which could make 70psi boost), you will now focus on producing a special engine design, tailored for these high pressures?

Sounds exciting! 😁

Cheers
Scott

[racket]

Hi Scott

LOL, now you've got me confused :-)

The average turbo comp wheel has an in/out ratio ~1.6-2:1 , the X858 in your kart has a ~1.6 :1 area ratio and ~1,300 ft/sec outlet speed , this keeps the outflow actual angle ~20 degrees above tangent with actual velocity hopefully subsonic so that theres no shocks in the diffuser.

By having a larger in/out ratio , it doesn't mean poor effic at low PRs if the diffuser is vaneless , but it creates problems with a vaned diffuser, I might need to arrange a different diffuser , larger vaneless space before the vanes to build in some "flexibility".

Some of the tractor pullers are running 100psi boosts from these sized KTS wheels , the wheels don't last long , but they don't care ..

Think of it in densities coming out of the comp , if we're only running normal P2s the density coming out of the wheel might only be say 10 cubic feet per pound of air , but at high PRs it could be only 5 cubic feet per pound , so we only need half the tip height at the exducer for the same "radial" speed , but because the tip speed would be higher at the higher PRs the actual air angle would be lower , theres plenty of juggling that can be done between tip heights , PRs , flow rates , tip speeds, swept back angles etc etc :-)

But a "special" engine will be needed for the KTS wheel I purchased , if they advertise 70 psi of boost capability , then why not try for it, the inducer will hopefully have been designed for high Mach numbers at the tip with such an "abnormal" in/out area ratio, might even get shock diamonds in the exhaust of the A/B :-)

Cheers
John

[Chuks]

hi John.

Thants a big dissapointment for us designing based on datas in the KTS CATALOGUE.
Maybe one should assum -1.8mm for the tip height.