Foil....

[bmxmike]

I was wondering if there are any turbos for us that use Foil Bearings yet? I just saw a turbo with one but wasnt sure if it was still in experimental stages.

[Stewi]

I was wondering if there are any turbos for us that use Foil Bearings yet? I just saw a turbo with one but wasnt sure if it was still in experimental stages.

im not even sure what a foil bearing is. For the most part, any high perfromance turbo is avail as a standard bearing which is cooled and lubricated by oil, single ball bearing (only one cartridge) or dual ball bearing (two cartridges) Most ball bearing turbo's are avail in steel or ceramic ball bearings, steel being more durable and ceramic being lighter in weight, more practice for larger harder to spool turbos. Also Ball bearing turbos typically are water cooled and oil lubricated.

[bmxmike]

Well a foil bearing acts as a Air foil.....It is a type of air bearing. Here is how it works.....

A shaft is supported by a complaint, spring loaded foil journal lining. Once the shaft is spinning fast enough, the working fluid(usually air), pushes the foil away from the shaft so that there is no contact. The shaft and foil are seperated by the airs high pressure which is generated by the rotation which pulls gas into the bearing via viscosity effect. A high speed of the shaft in respect to the foil is needed to initiate the air gap, and once this has been acheived, no wear occurs.

Unlike aero or hydrostatic bearings, foil bearings require no external pressurisation system for the working fluid, so the hydrodynamic bearing is self-starting. Anti-wear coatings exist that allow over 100,000 start/stop cycles for typical applications. New third generation bearings can hold 9000 times their weight, at extremely high speeds.

The main advantage of using these is that:
* Increased reliability
* Higher (unlimited) speed capability
* Higher and lower temperature capability (40 K to 2500 K)
* No scheduled maintenance
* High vibration and shock load capacity
* Quieter operation

Thats why they are start to use them in turbos. There are some applications that already have them. The main thing they were working on is a way increase the start stop. Cause once it start spinning its fine. It's just whenever you first start up the car but the protective coatings help keep wear slim to none. Though i have read that a company is looking at a way to suspend the bearing till min. speed is reached.

[Stewi]

That all sounds good, but I wonder how well it handles heat.

[evil-G-nius]

Yeah I was wondering about the heat too...I doubt its "Foil" like most of us are thinking. I think they just mean a thin metal...but even still...heat could be an issue

[bmxmike]

The reason its called "Foil" is cause it suspends it in air. It works how like a Hydrofoil works on a boat. As the speed increases and the water goes over the foil the boat begins to rise and has less drag as there is a pocket of air suspending the boat. Heat is actually not a problem cause bearing is made out of a strong material. And really that much heat isn't produced since the nothing is actually touching the bearing cause it is actually suspend in air.

[DOHCstunr]

The reason its called "Foil" is cause it suspends it in air. It works how like a Hydrofoil works on a boat. As the speed increases and the water goes over the foil the boat begins to rise and has less drag as there is a pocket of air suspending the boat. Heat is actually not a problem cause bearing is made out of a strong material. And really that much heat isn't produced since the nothing is actually touching the bearing cause it is actually suspend in air.

just the 1600* of noxious exhaust heat being continuously pumped through the turbine.
there woudl have to be some sort of seal on the shaft seprating the exhaust form the bearing, because the rich nature of a turbocharger woudl create a lot of carbon buidlup that woudl cause your bearing to fail.
you would also need to have a seal on the compressor side of the turbo to keep boost from blowing through your bearing and leaking out of the cold side of the turbo system.

if those seals are touching the shaft,
they will need to be lubricated.

with oil....

[bmxmike]

Well there doing something then that doesnt require oil. Cause i have seen a turbo with but not how it was setup internally and they have been using them since 1969 in the military and Garrett Air research is starting to install them in turbos more and more.