| 摘要 |
PROBLEM TO BE SOLVED: To optimally keep the chip clearance of an open impeller independent of an operation state of a centrifugal compressor. SOLUTION: A balance piston 50 is installed on the back surface of the final step impeller 27c of the centrifugal compressor 1, the pressure within a balance chamber 57 is applied to the balance piston 50, and the pressure within the balance chamber 57 is controlled by adjusting the opening of a balance valve 59 installed in a balance connector passage 57 connecting the balance chamber and a suction port of the compressor. A shaft position sensor 45 for detecting the displacement of a rotating shaft is installed at the shaft end of an impeller rotating shaft 25 of the compressor, and the opening of the balance valve is controlled so that the detected shaft position becomes a previously set target value. Even if gas thrust force acting on each impeller is varied by the change in operation state, the impeller rotating shaft is always kept in the target position where the chip clearance of the open impeller becomes optimum.
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