Centrifugal compressor

Abstract

The present invention provides a centrifugal compressor that inhibits possible leakage while reducing a destabilizing fluid force generated in a seal to prevent the possible instable vibration of a rotor. The centrifugal compressor includes a casing, a rotor rotatably installed in the casing and having an impeller, and seals provided in the clearance between the casing and the rotor to prevent a fluid from leaking through the clearance from a high pressure side to a low pressure side. The rotor rotates to compress gas. For example, the balance piston seal is composed of a damper seal with a plurality of holes and a labyrinth seal with an annular parallel groove; the damper seal and the labyrinth seal are continuously provided. The damper seal is disposed on the high pressure side in a leakage flow direction. The labyrinth seal is disposed on the low pressure side in the leakage flow direction.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a seal structure for a centrifugal compressor, and is suitable particularly for preventing unstable vibration of a rotor during a high-speed, high-pressure operation.[0002]Centrifugal compressors compressing gas such as air are widely utilized for various machines. Inside of a casing of a centrifugal compressor, a rotating shaft with an impeller installed thereon is rotatably supported by bearings. Gas sucked through a suction port is compressed by rotation of the impeller and discharged through a discharge port. The gas compressed by the impeller is sealed by an impeller eye seal of an impeller eye, an inter-stage seal between stages of the impeller, and a balance piston seal provided in a last stage.[0003]A labyrinth seal and a damper seal are known as conventional seal structures. As shown in a sectional view of any impeller stage in a centrifugal compressor in FIG. 1 of JP Published Patent Application No. 6-249186...

AI Technical Summary

Benefits of technology

[0007]An object of the present invention is to provide a centrifugal compressor that can be stably operated under a high-speed and high-pressure condition, with possible leakage from a seal prevented.

[0012]According to the present invention, the damper seal and the labyrinth seal are continuously provided. Thus, the labyrinth seal can inhibit possible leakage, while the damper seal can stabilize the rotor. Moreover, the damper seal is disposed on the high pressure side of the seal, whereas the labyrinth seal is disposed on the low pressure side. Thus, on the high pressure side, where a relatively strong destabilizing fluid force may be generated, the damper seal can exert a damping effect. Furthermore, on the high pressure side, corresponding to a leakage flow upstream side, the circumferential component of the leakage flow velocity can be reduced. This enables the rotor to be further stabilized. Additionally, the length of the damper seal in the leakage flow direction is set to at most half of that of the entire seal. This allows the rotor to be effectively stabilized, with possible leakage from the seal inhibited.

Problems solved by technology

This results in a fluid force (hereinafter referred to as a “destabilizing fluid force) destabilizing the rotor.

In the worst case, the destabilizing fluid force causes the rotor to vibrate unstably.

In particular, if the rotor rotates at high speed or there is a high differential pressure between the seal inlet and outlet, the destabilizing fluid force is increased.

However, the increased discharge pressure of the centrifugal compressor increases the destabilizing fluid force, thus reducing the vibration stability of the rotor.

However, the damper seal is inferior in the leakage prevention property, thus reducing the efficiency of the compressor.

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