Patent ID: 8756938

Claim:
A method for operating a gas compressor which compresses gas whose supply conditions change and which is equipped with an intake-flow regulating mechanism, said method comprising: determining a reference limit pressure ratio based on design conditions of the gas compressor; detecting an operating-state value of the gas compressor; determining a first correction factor based on the detected operating-state value; deriving a corrected limit pressure ratio by correcting the reference limit pressure ratio using the first correction factor; and operating the gas compressor using the corrected limit pressure ratio, wherein each of the reference limit pressure ratio and the corrected limit pressure ratio defines an operational upper limit of a pressure ratio relative to an intake flow rate of the gas compressor or a degree of opening of the intake-flow regulating mechanism to prevent surging in the gas compressor, and wherein the first correction factor is obtained from a correcting rotational speed ratio (α) obtained from the following [Eq. 1], where N 0 is a reference rotational speed of the gas compressor, κ 0 is a reference specific heat ratio of the intake gas to the gas compressor, R 0 is a reference gas constant of the intake gas to the gas compressor, T 0 is a reference temperature of the intake gas to the gas compressor, N is an actual rotational speed of the gas compressor, κ is a present specific heat ratio of the intake gas to the gas compressor, R is a present gas constant of the intake gas to the gas compressor, and T is a present temperature of the intake gas to the gas compressor. Correcting ⁢ ⁢ rotational ⁢ ⁢ speed ⁢ ⁢ ratio ⁢ ⁢ α = N ⁢ κ 0 ⁢ R 0 ⁢ T 0 N 0 ⁢ κ ⁢ ⁢ RT . [ Eq . ⁢ 1 ]