Question about turbo bearings
I was pretty sure that all turbos used fluid bearings but I'm not finding much information on this. Everyone talks about ball bearing turbos but from what I know the average ball bearing cannot deal with the pressure, temperature and wear that it'd see in a turbo. So I'm wondering if all turbos actually run on a fluid bearing at high speeds.
Also, are there any foil bearing turbos out there yet? (Probably for diesel or other high up-time applications since they have a set start-up cycle life.).
To your second question: I don't think there are any automotive applications, but foil bearing Turbines have been around for a while. That's how early turbojet engines were put together, I'm not sure how a foil-bearing automotive turbo would have an advantage of what has been considered the superior ball-bearing-in-pressurized-oil system...
To your first question: It works as a standard oiled ball-bearing at low speeds and at high speed as a kind of hybrid ball/fluid bearing. When the shaft is spinning that fast the oil is doing most of the work but is working from inside the bearing. It's hard to explain but you couldn't have a true fluid bearing with the setup of the turbo in the way that journal bearings are. There's no way to seal the oil in properly and still allow the shaft to have zero contact and near-zero friction. These are not average ball bearings, either.
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