Patent ID: 9175691
Filing Date: 2015-11-03
Classification: F04B,F04C,F04D,F25J,Y02B

Abstract:
1. A method of producing a compressed gas and controlling flow rate of the compressed gas, said method comprising: compressing a gas within a compression system having an electric motor and at least one stage of compression directly coupled to the electric motor and configured to compress a gas and thereby to produce the compressed gas, the compression system having a restricted speed zone corresponding to a range of speeds of the electric motor at which vibrational modes can damage the compression system; determining a flow rate and a desired flow rate of the compressed gas through the compression system; controlling the flow rate of the compressed gas through the compression system to produce the desired flow rate by adjusting inlet guide vanes of a centrifugal compressor of the at least one stage of compression and by adjusting the speed of the electric motor and therefore, an impeller of the centrifugal compressor with a speed controller; wherein, when the desired flow rate is able to be obtained with the speed of the electric motor situated above or below the restricted speed zone, the flow rate of the compressed gas through the compression system is controlled by adjusting the speed of the electric motor with the speed controller and with the inlet guide vanes set at a 0° swirl angle; and wherein, when the desired flow rate is not able to be obtained without the speed of the electric motor situated within the restricted speed zone, the flow rate of the compressed gas through the compression system is controlled by setting the speed of the electric motor with the speed controller at an upper speed, above the restricted speed zone and adjusting the inlet guide vanes to obtain the desired flow rate; wherein, when the speed of the electric motor is set at the upper speed, above the restricted speed zone and the desired flow rate requires adjusting the speed of the electric motor to a speed below the restricted speed zone, the speed of the electric motor is decreased in decreasing speed steps until a lower speed, below the restricted speed zone, is obtained and the inlet guide vanes are successively opened during each of said decreasing speed steps such that the inlet guide vanes are set at the 0° swirl angle when the speed of the electric motor is at the lower speed, below the restricted speed zone; and wherein, when the speed of the electric motor is set below the restricted speed zone and the desired flow rate requires adjusting the speed of the electric motor to a new speed above the restricted speed zone, the speed of the electric motor is increased in increasing speed steps until the new speed, above the restricted speed zone, is obtained and the inlet guide vanes are successively closed during each of said increasing speed steps such that the position of the inlet guide vanes required to obtain the desired flow rate will be reached when the new speed, above the restricted speed zone is reached.