11 October 2015

I Did Not Think that You Could Use Roller Bearings for This

There are a number of reasons why roller bearings (ball bearings, cylindrical roller bearings, spherical roller bearings, tapered roller bearings, etc.) find use.

They provide a low drag solution, and, particularly for low speed applications, like turret rings, they tend to be the favored solution.

For higher speed applications, things like crankshaft bearings and bearings though, they are not used, because they tend to shake themselves to pieces.

Instead, fluid bearings are used, where the bearing moves with respect to the journal supported on a thin film of a fluid, typically some sort of oil or air. (Think air-hockey puck)

There is more drag in the system, but it functions at much higher speeds.

This is why you do not see roller bearings in jet enginse, at least that was why until now: (paid subscription required)
A recent development in Germany by FAG Aerospace and MTU Aero Engines could affect turbofan engine operations in three key areas: oil consumption, fuel economy and power generation.

The companies designed a main-shaft ball bearing that exceeds, reportedly for the first time, an operational speed parameter of 4 million mm/min. (160,000 in./min.)—66% greater than the 2.4 million mm/min. generated by most conventional bearings during takeoff.

At maximum speed, the bearing reportedly consumes the same amount of oil and generates identical temperatures as conventional bearings. At normal speed up to 50% less oil—6 liters/min. (1.6 gal./min.)—is needed for cooling, temperature is 25C (77F) lower and power loss drops as much as 25%.

Peter Glockner, head of product design at FAG Aerospace, attributes the reduction in oil consumption to, among other features, outer-ring cooling technology and an “integrated squeeze-film damper” that mitigates vibration load. The benefits of lower oil consumption and reduced vibration include power-loss savings, which “increase[s] the mechanical efficiency of the engine” and thus lowers fuel consumption, he adds.

The fuel savings are low: FAG Aerospace estimates the technology could save 200,000 tons of fuel annually for global turbofan fleets. In 2015, total fuel consumption for all aircraft is forecast to be up to 230 million metric tons.

Nevertheless, the technology appears to have clear engine-power advantages, and even minuscule savings add up for large operators, including the military.
Assumign that the price comes down, I would expect to see this in automotive turbocharger bearings, and (eventually) main engine bearings.

When I was in E-school, this was the sort of application for roller bearings that we were basically told, "Don't even think about it".

And now someone is trying to sell it.

I am impressed


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