20 November, 2017

Turbo blowers with air bearings

13 April, 2017

Aeration tanks for wastewater treatment must be continuously provided with large air volumes, and turbo blowers can offer an energy efficient solution. Aerzen has developed a simple method for fast-rotating turbo blowers – air bearings.


The construction of Aerzen turbo blowers is quite simple: A blade wheel, aerodynamically optimised and located directly on the motor shaft, rotates in a spiral housing thus generating the volume flow. The particular challenge of this technology is the high speed range from 20,000 to 70,000 rpm. Besides special motors and a frequency converter, the shaft bearing is an important issue. Aerzen comments that standard industrial roller bearings are not appropriate for the occurring loads.

In this regard, Aerzen claimed to have found an optimal solution for this problem: The two radial bearings of the drive shaft and the thrust bearing for absorbing axial forces have contact-free air bearings. As the turbo blower is started, the shaft rotation generates a circular motion in the air gap between shaft and bearing through natural imbalance, compressing the air in the gap. With increasing speed, the axis centres itself and is held in a contact-free position by an air pressure of over 30 bar. This system is completed by what is described as a maintenance-free two-component coating, which serves as a friction partner between the highly finished surfaces when the turbo machine is activated and the air cushion is formed within fractions of a second. The PTFE layer is said to provide good lubricant-free sliding properties.

With regard to magnetic bearings, Aerzen states that magnetic bearings basically work as good as air foil bearings, but they have certain disadvantages compared with the Aerzen bearings: The company comments that solenoids, arranged circularly, require a highly complex control system and an uninterrupted power supply. This, claims Aerzen, makes the magnetic bearing expensive with more maintenance being required, which can considerably increase life-cycle costs.

Aerzen states that the air bearing principle does not require any electrical, mechanical or pneumatic controls.

www.aerzen.com/en-gb




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