Takayuki Kishi

High Efficiency, High Reliability Oil Injection Type Helium Screw Compressor

Investigation of the optimum condition and the reliability of two-stage oil injection type helium screw compressor has been carried out, in order to determine ways of enhancing compressor performance with high reliability. It was found that the volumetric efficiency of the compressor is increased by reducing the mass flow ratio of the helium gas / lubricating oil while accelerating compressor revolution speed. And it was proved that compressor volumetric efficiency is significantly influenced by sound speed in the mixture of gas and lubricating oil. The authors were able to derive a formula for predicting the change of compressor volumetric efficiency, when the mass flow ratio of gas / lubricating oil and the revolution speed are changed. It was also found that shaft power decreases when the ratio of theoretical volumetric flow rates of the high- and low-stage machines is set at 1:4 or a low density lubricating oil is utilized. In result, the advanced experimental machine achieved an isothermal efficiency level of 60% without any trouble.