Cooling Jacket Pros/Cons

[badger]

Would a cooling jacket, surrounding the turbo-charger, be a worthwhile thing? By 'cooling-jacket', I mean a simple shroud, surrounding the turbo, that will use the fast moving exhaust gasses to create a vacuum, up front, and thus pull free-flowing cool air into the front of the jacket and over the hot turbine section of the turbo-charger. Would this be a worthwhile thing, or just a waste of time?    

[Richard OConnell]

I'm trying to picture what you're describing. If you mean to divert air from the compressor past the combustor along the outer skin of the engine and bypass the turbine and be recombined with exhaust pre-nozzle, you're going to lose some power. if you're wanting to dump cool air in front of the turbine, you're working against your reasoning for heating the air up in the first place. Could you explain in better detail? What are you trying to cool, the turbo housing?

[azwood]

If you mean a turbo beanie the idea is to keep the heat in and make it more efficient. The down side is they can promote cracking in the housing prenty of people use them I had one on my car never cracked anything.despite the headers getting cherry red

[badger]

Not diverting air from the compressor, nor do I know what is meant by the term 'Beanie'..?
Here's a 'concept' drawing for a visual aid. There is 'NOTHING' drawn to actual scale, here. Concept only...

[racket]

It will keep radiant heat and potential burns from the operator , normal practice on some commercial APUs where the exhaust creates a "chimney" effect to cool the compartment by drawing in cool air and using the high speed exhaust to "power" the system .

[badger]

What about the compressor side of the turbo? I might be wearing my 'half-arsed' engineering hat a bit too tight, and in such foolishly over-thinking this, but... Wouldn't keeping the compressor section of the turbo a bit cooler, in temp, make for a more 'dense' flow of air interring the combustion chamber, thus allowing for a hotter burn and more gas expansion/thrust?

[azwood]

Ahh Roger that not what I thought you meant

[Richard OConnell]

Generally speaking, the cooler the air at the intake, the denser and more power you can make.

[sauerkraut]

An easy way to get denser air is to use a diffuser rather than a constant cross-section to connect the comp outlet to the combustor.

EDIT: Also, intuitively I would imagine that what you describe you hurt you more than it would help. Not only would it "cool" the cold side of the turbo (which is a good thing), it would also cool the hot side (which is a bad thing, it reduces turbine efficiency). The thing is, heat transfer is a function of temperature difference(among other things), so your cooling air will be doing relatively little on the cold side, but it will be pulling a lot of heat from the hot side.

[racket]

Hi Tom

Theres such huge amounts of heat energy within our turbo scrolls, both comp and turb, that theres very little drop in temp to be achieved by any form of draught cooling , a shroud has a benefit with regards safety more than any other .

With regards getting a denser airmass going to the combustor, there would be negligible difference .

As for adding a diffuser delivery tube, it'll only change dynamic pressure energy into static pressure , the density will go up a tad but the reduction in velocity needs to be restored within the flametube , so theres no overall gain to be had , the positive with a delivery tube diffuser is the ability to feed air into the combustor more efficiently and in the process improving combustion and reducing losses , not attempting to increase density of the air, we need to consider total pressure as well as static pressure , generally a turbos comp housing outlet is sized to provide the "best" flow area with respect to its velocity , not too fast and not too slow , theres a "sweet spot" ..........it gets complicated.

Cheers
John

[badger]

I understand. Thanks for chiming in, guys!
Tom...