Experimental study of small-size air turbo blower supported by externally pressurized conical gas bearings

• We made small conical bearings with a 10 mm maximum diameter.
• Measured characteristics were agreed with the calculated values.
• The rotor vibrates with a forward whirl in the rotational direction.
• The vibration is a conical mode.
• The blower produces 1.77 kPa and 19.2 × 10− 5 m3/s at 350 Hz.

This paper describes a several ten thousand rpm class small-size air turbo blower. This has been newly developed using externally pressurized conical gas bearings and blower impeller with centrifugal suction blades on both faces. This bearing can reduce the number of machine parts since it is possible to support the thrust and radial load components in both directions. Calculations of the characteristics were conducted and investigated using the manufactured test bearings. A test rig was manufactured, and the characteristics were experimentally verified. These bearings have a conical bearing surface with diameters of 10 mm and 8 mm and a length of 15 mm. A pair of length is 30 mm. The actual bearing clearances are 0.012 mm and 0.014 mm, respectively. The measured bearing characteristics agreed with the designed values. It was clarified that the proposed calculation method is useful for predicting the characteristics in a relatively simple way. The air turbo blower impeller has a 15 mm diameter and a 3 mm thickness with centrifugal suction blades on both faces that were made by precision machining. The measured rotational frequency of the rotor exceeds 350 Hz (21,000 rpm) in the test. The rotor vibration was verified as a forward whirl with a conical mode. The blower characteristics were also investigated. The maximum discharge air flow rate and the pressure were 19.2 × 10− 5 m3/s and 1.77 kPa, respectively, at the maximum rotational frequency of 350 Hz. This may be used as a small-size air supply blower.