Screw compressor equipment for accommodating low compression ratio and pressure variation and the operation method thereof

摘要

The invention provides a method of operating a screw compressor equipment without reducing the efficiency, in which a screw compressor 1 of which the internal volume ratio is variable by means of an internal volume ratio control valve is driven by a driving machine 2, the discharge side of the compressor 1 is communicated with the suction side of the same by way of a bypass control valve 9 as needed, the internal volume ratio control valve 3 is always controlled to be located at a position calculated so that the internal volume ratio with which the polytropic efficiency is maximum is obtained, and gas flow rate is controlled by controlling the rotation speed under normal conditions and controlled by controlling the bypassing flow rate from the discharge side to the suction side under very low rotation speed.