The disclosure includes controlling a pressure ratio for a compressing system, comprising introducing a quantity of liquid into an input stream to create a multiphase input stream, compressing the multiphase input stream with a centrifugal compressor to create a discharge stream, measuring a parameter of the discharge stream, wherein the discharge parameter corresponds to a pressure ratio for the centrifugal compressor, when the parameter exceeds a first predetermined point, increasing a pressure ratio of the centrifugal compressor by increasing the quantity of liquid introduced, and when the parameter exceeds a second predetermined point, decreasing the pressure ratio by decreasing the quantity of liquid introduced.