Why no foil bearing turbos yet? 2

[Nicator]

As I understand, foil bearings are not a terribly new technology. Supposedly when used in conjunction with modern high temperature coatings, the technology is quite effective.

Google "Nasa foil bearing turbo" and you will see that they claim the technology works and has good potential. Supposedly they've been able to match conventional bearing turbo performance, using air as the lubricant in foil bearing units.

My question is, why aren't these being widely used yet? Why aren't they commercially available? Is it purely a matter of economics, or is there an engineering concern that prevents them from being adopted?

Evidently Garrett has been behind much of the research into foil bearings to be used in turbochargers, but they're actively pushing their ball bearing, ceramic turbine units instead. Anyone know why?

Thanks

 

[tbuelna]

The automotive OEMs are notoriously conservative when it comes to adopting new technology. Apparently, they feel the liability risks (potential recalls) outweigh the benefit of not having oil in the turbocharger.

A few weeks back, I spoke with a Garrett rep at the SEMA show in Vegas. He said that most of the development work he knew about going on at Garrett was focused on VNT and EGR coolers.

 

[globi5]

Don't the foil bearings have more wear at no or low speeds? (So this might not be ideal in an application where the engine is frequently turned on and off.)

 

[tbuelna]

NASA claims they have successfully tested foil bearings on their test rig for up to 100K start/stop cycles.

http://www.nasa.gov/centers/glenn/about/fs14grc_prt.htm

 

[MikeHalloran]

I believe the NASA report. The sample size was ... one.

I guaran- damn- tee that the NASA test rig was not assembled in a working factory.

Would you risk a couple billion dollars on that data?





Mike Halloran
Pembroke Pines, FL, USA

 

[drwebb]

Doesn't cost a couple billion dollars for an OEM to build some prototypes and see for themselves. US OEMs aren't the leaders on passenger car turbos; maybe the Europeans are looking into it?

 

[MikeHalloran]

Prototypes don't tell you squat.



Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

By which I mean, I've lost count of the number of my projects where the prototypes, even those produced in moderate numbers in a semi- production environment, worked flawlessly, and real production parts failed almost immediately upon entering service.

Therefore I amend my previous statement as follows:

Prototypes don't tell you squat about real world durability.



Mike Halloran
Pembroke Pines, FL, USA

 

[r2800]

You're dead right why bother to experiment with high tech if low tech works ok,all you need is an oil pipe and a drain for the turbo how difficult is that.
Besides the manufacturer can design it and make it and sell it just so Joe Public can abuse it and wreck it!

 

[Nicator]

Why? For more flexibility and efficiency. Your point on turbochargers is somewhat valid, but as remote mounted units become more popular, more people will become dissatisfied with having to rely on an electrical oil pump to pump the oil back to the engine.

And, for what its worth, the technology could potentially change other applications besides just turbos.

 

[patprimmer]

Why will remote mounted units become more popular. Remote mounting increases pipe lengths between ports and turbo, therefore reducing efficiency and response.

I should imagine there are also cracking problems in the exhaust upstream of the turbo as support while accommodating thermal expansion in the longer pipe will be a problem.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Peter7307]

r2800's comments above sum up the situation for most suppliers who are in the business of making money for their shareholders through the products they retail or supply to car builders.

Because new technology is out there it does not necessarily follow manufacturers will adopt it.
The concept of financial inertia plays a large part in these considerations.
They may not be prepared to have their technology based on that of another source which they would need to pay licencing fees to obtain which adds to their cost base.

The more satisfactorily the current technology fills the need of the marketplace the less likely this is to happen.

Turbo builders such as Garrett would certainly be aware of the foil bearing but since they most likely already have their manufacturing equipment set up to build conventional bearing turbos they would be unlikely to change unless some clear advantage could be proven.

They would also have their own patents and methods in place so it is also unlikely they would move away from these.

Pete.

 

[r2800]

Peter 7307 has succinctly covered all aspects of introducing new technology. Too often these days new ideas are introduced that have no real advantage over their predecessors other than that they are new.I personally welcome new,useful and cost effective improvements providing they do what is written on the tin.

 

[SomptingGuy]

Doesn't cost a couple billion dollars for an OEM to build some prototypes and see for themselves.

So which OEMs make their own turbos?

 

[NickE]

Adn it does cost quite a large amount of money (not billions) but it could be millions to get a new technology to the quality level required for use in a car.

(Heck PPAP could cost millions for some components.)

 

[r2800]

It is important to note that manufacturers are there to make profit for their shareholders not to speculate in technology for the sake of it. If something has benefits that are worthwhile eg cheaper,lighter,faster etc then they will rise to the pile and be selected for production.
If something still does a good job why change for the sake of it.

 

[turbomotor]

Nicator,

I love air bearings. I've made a motor driven compressor for primary charge air supply to a PEM FC at high altitude, and it was a joy to test (no messy oil based lube system).

But understand that only aerospace programs can possible justify the current cost. Remember that the highly engineered damping component of compliant foil bearings is absolutely critical in a high speed turbomachine that typically traverses two rigid body critical speeds. And this assumes a "sub-critical" machine, that is, operation below the first bending critical.

Don't take my word for it. Call the folks at MITI and get a ROM quote on a bearing development program and recurring production cost.

Dick

 

[turbomotor]

Gentlemen,

I just re-read the string more carefully. Mike Halloran hit the nail on the head. I won't bore you with the many examples I have that support his claim, as I'm sure that you all have your own set of horror stories. I just happen to have some that involve high volume production turbocharger bearing systems, including the wonderful, aerospace proven, compliant foil air bearing.

Name withheld so that my ex-Garrett compatriates won't hunt me down and shoot me.