CAPACITY CONTROL SYSTEM AND METHOD FOR CENTRIFUGAL COMPRESSOR

摘要

A system and method for controlling compressor capacity while maintaining compressor stability includes providing a compressor and a flow reduction device for controlling flow of refrigerant through the compressor; measuring suction pressure and discharge pressure of the compressor; calculating a compressor head factor based on the suction discharge pressures; calculating the speed of sound in the refrigerant; calculating the tip speed of the impeller divided by the speed of sound; calculating the tip speed of the impeller at the minimum Mach number; calculating a multiplier of speed increase as a function of the flow reduction device based on an actuator feed-back signal; determining a minimum rotational speed at which the compressor may operate free from a surge condition; and controlling a rotational speed of the compressor above the minimum rotational speed.