Test Compressor

The modeled and measured compressor is a one-stage radial compressor. The compressor is driven directly by a 175 kW high-speed electric motor that is supplied with variable frequency AC-current by a 200 kW inverter. No gear­box is needed because of the single shaft construction, and the use of an in­verter allows variable speed control from zero RPM to full speed. Active mag­netic bearings are used in the rotor. The compressor has a mass flow rate of 1.574 kg/s, pressure ratio 2.01, and rotational speed 21640 RPM at the design operation point, and it produces a 50-kPa vacuum at the inlet.

The impeller has 7 full blades and 7 splitter blades with 30 ° backsweep at the trailing edge measured from the radial direction. The diameter of the
impeller is 309 mm. The diffuser is vaneless and the overhung volute has a circular cross-section. The area of the cross-section of the volute is designed for a constant static pressure along the circumference at the design operation point. More detailed information about the test facilities and the simulated compressor are presented in Ref. [6].