"Fat Boy" 12/118 thrust engine

[racket]

Hi Smithy

LOL.............thanks for the encouragement , yep , I'll get there eventually , just a matter of time and plenty of fiddling around.

I remember Mike Early's ( Yahoo DIY Gas TUrbines) efforts with his 26 different flametubes before he was happy , I hope it doesn't take that long .

More time needed sitting and looking maybe ;-)

Cheers
John

[smithy1]

Yep, plenty of sitting and looking required...That's my excuse anyway..! ;-)

And you'll get it running as it should...I have confidence in you..!

Cheers,
Smithy.

[turboron]

John, would KTS make a titanium impeller with enough pressure ratio and flow that we could use the Allison Model 250 turbine parts?

[racket]

Hi Ron

KTS make a Ti wheel, # 6003 , that fits the Garrett GT6041 turb shaft , 104 mm inducer , 151 mm exducer with extended tip to 161 mm , but this is still a tad too small in diameter for the C20 second stage turb wheel which is ~163 mm .

Now a second thought on this is perhaps their "super charger" wheels , they have some very low Trim wheels which may work , maybe their #SC04 , 91 mm ind , 167/174 mm exducer , the C20 second stage turb wheel has "limited" flow capability due to the wheel having a lot of blades, so the 91 mm inducer could be about right .

I've dismissed the super charger wheels because, being a greedy bugger, they don't have >100mm inducers, but if someone wanted to make a nice engine and isn't concerned about the flow limitations , they'd be fine .

Cheers
John

[turboron]

John, I don't understand your point on the compressor diameter being too small for the C20 diameter. Do you mean that the compressor tip speed will not be sufficient to create a pressure ratio sufficient to satisfy the C20 turbine flow constant at a rotor speed limited by the turbine stress?

Thanks, Ron

[dieselguy86]

John,

How about this wheel? m.ebay.com/itm/MAMBA-Turbo-Billet-Compressor-Wheel-For-Holset-HX82-130-180-mm-8-8-/262588790484

-joe

[racket]

Hi Ron

The turbine tip speed would be getting excessive before the comp was producing a high pressure ratio if the diameters are similar , ideally we need a comp ~10% bigger in diameter , this then seems to find a better "balance" with the turbine power production whilst keeping those tip speeds within reason .

Without a high pressure ratio from the comp the flow through the turb is limited by the lowish density of the hot gases, theres always a "sweet spot" between comp mass flow/PR/temperature and turb stage flow areas and mean blade speed , trying to juggling things to find it is the challenge, some combos are " just right", whilst other require "two wrongs to make a right " .

Cheers
John

[racket]

Hi Joe

Great wheel ,a KTS X867 , but the mass flow from that 130 mm inducer would require a turb wheel I haven't been able to find :-(

With mass flow up near 4.5 lbs/sec , the turb wheel will need to be capable of producing >500 HP to spin it .

These guys www.yilicasting.com/ make 180 mm turb wheels and NGV castings , Cost ~$US 750 each for the rough castings in Inco 713C,.............. LOL, don't ask why I know ;-)

Cheers
John

[racket]

Hi Joe

Further to my last email ................that comp wheel is for a Holset HX82 turbo , but you'd need to have a higher pressure going into the turb wheel than whats coming out of the comp for it to work, this can be done on an IC engine but unfortunately we can't , also the diesel exhaust would be cooler than whats ideal for us , so the more favourable density on the diesel helps with the flow rate .

I have considered cutting down an Allison C20 4th stage turbine wheel to a smaller diameter , with the removal of the tip seal ring and a half inch or so of blading , there might be enough flow area for a large inducered comp .

Whether or not the turbine wheel could cope physically with the task of producing the necessary horsepower is debatable , I'd be looking at a 150% increase in horsepower production over standard , I might get away with it for a while , but the extra bending stresses from the higher gas pressures and velocities might destroy it , and the increase in rpm is another matter that is of concern , I don't want to spend a year and quite a bit of cash making something that might "grenade" :-(

Cheers
John

[dieselguy86]

Hi John,

Yep, HX82/83, thats the largest wheel ive been able to find.

Thats not a terrible price, i had a quote from jetmax for finished 70mm wheel and NGV shipped for ~$620USD. www.jetmax.ch/en/turbine_wheels.htm

Are you saying the 4th stage c20 wheel is designed for a higher pr? Since the compressor cant meet the pr requirement the turb wheel has to be "resized" to better match the lower pr of the compressor?

Another option would be to design a wheel according to kamps book, have someone design it in CAD, send it to me and i can have it 3D printed in inconel. I know its not as advanced as commercial wheels, but it can be tailored to your needs, something to think about.

[racket]

Hi Joe

Nope , the C20 4th stage would be lucky to see a PR of 1.8 :1 going into it with relatively modest gas velocities compared to a gas producer stage , its a fairly "lightweight" wheel compared to the ones driving the C20 comp stages, each of the two C20 freepower wheels only has to turn out 210 HP , whereas that 130mm comp wheel will be needing 500 HP .

The KTS wheels are quite reasonably priced for what one gets, they basically just charge for machining hours , the price goes up as the diameter goes up .

I've had the books out today checking the 12/118's flows vs flow areas vs velocities etc etc to see if I can find something that I made a mistake with , about the only area thats a bit suspect is the exducer flow area , as it has been from the beginning .................I'll keep searching :-)

Cheers
John

[dieselguy86]

Hi John,

Ah ok i understand now.
Are we approaching the age of diy "multi-stage turbine" engines? Like you stated the turbine that normally drives this is not suitable for gt use.
Id love to hear the roar that compressor could support. The 6x-mm compressor in my AMT rc turbine borderlines cackles in your ear drums at full tilt.

-Joe

[racket]

Hi Joe


NO NO NO , multistage turbines, just too much work .

Yep , that 130mm comp will just have to wait until a suitable turbine wheel becomes available , it'll need to be an axial wheel I feel as a radial inflow one would be just too heavy and virtually impossible to source, though there are some out there , the smaller ABB ones come to mind , but turn the wrong way for that comp wheel .

We'll just have to keep dreaming ;-)

Cheers
John

[dieselguy86]

Hi John,

Hmmmmm give me some dimensions and ill run a disk of SS to the machine shop around the corner from me. They have several 5 axis mills and make turbochargers daily.

-Joe

[racket]

Hi Joe

We need Inco for high temps , stainless wheels limit both rpm and T I Ts , so power production is down .

I'm just about to revisit that C20 4th stage wheel to see how much can be removed , maybe a way around it yet , leave it with me :-)

Cheers
John