Abstract: In a fluid machine such as multistage centrifugal compressor, the pressure of a working fluid is raised with the rotation of a impeller. A shaft sealing device is mounted at the end of the rotary shaft in order to prevent the working gas of the raised pressure from leaking out of the fluid machine and then polluting the surroundings. In a case where the fluid machine operates to rotate at high speed, a labyrinth sealing device is employed for the purpose of reducing a frictional loss in the shaft sealing device. The labyrinth sealing device includes a plurality of stages of labyrinth fins which are formed on a casing or the rotary shaft, and a layer of abradable coating to-be-bitten which is formed in the surface part of the rotary shaft or the casing opposing to the labyrinth fins. The clearances between the labyrinth fins and the rotary shaft or the casing are made narrower on the low-pressure side of the labyrinth sealing device than on the high-pressure side thereof.

Abstract: By changing a vane height to produce different vanes from master vanes, different impellers are produced, and therefore there can be obtained an inexpensive and high-reliability multistage centrifugal compressor and an impellers therefor. An impeller for multistage centrifugal compressor, which is to be mounted on a rotary shaft, comprises a plurality of vanes disposed between a disk and a shroud and separated from one another equiangularly. By changing the vanes of the impeller only in height without changing the configuration, vanes can be obtained, and then a different impeller comprising the disk, a shroud and vanes is also obtained. Since a whole of the vane has a configuration identical to a part of the vane, these vane can be produced by a single pair of the pressing dies.

Abstract: In a fluid machine such as multistage centrifugal compressor, the pressure of a working fluid is raised with the rotation of a impeller. A shaft sealing device is mounted at the end of the rotary shaft in order to prevent the working gas of the raised pressure from leaking out of the fluid machine and then polluting the surroundings. In a case where the fluid machine operates to rotate at high speed, a labyrinth sealing device is employed for the purpose of reducing a frictional loss in the shaft sealing device. The labyrinth sealing device includes a plurality of stages of labyrinth fins which are formed on a casing or the rotary shaft, and a layer of abradable coating to-be-bitten which is formed in the surface part of the rotary shaft or the casing opposing to the labyrinth fins. The clearances between the labyrinth fins and the rotary shaft or the casing are made narrower on the low-pressure side of the labyrinth sealing device than on the high-pressure side thereof.

Abstract: In a multi-stage centrifugal compressor, having a plurality of impellers mounted on a rotation shaft, or a single-stage centrifugal compressor, a vaned diffuser, having a plurality of vanes, is mounted at a downstream side of the impeller, and a vaneless diffuser portion is formed downstream of this vaned diffuser. A meridian plane cross-sectional shape of each of two wall surfaces forming the vaneless diffuser portion provided downstream of the vaned diffuser is such that its channel height is decreased progressively in a downstream direction. Instead of this vaneless diffuser, there can be provided a second vaned diffuser having a small number of vanes. In this case, also, two wall surfaces, forming the second vaned diffuser, are contracted progressively in the downstream direction.

Abstract: In a fluid machine such as multistage centrifugal compressor, the pressure of a working fluid is raised with the rotation of a impeller. A shaft sealing device is mounted at the end of the rotary shaft in order to prevent the working gas of the raised pressure from leaking out of the fluid machine and then polluting the surroundings. In a case where the fluid machine operates to rotate at high speed, a labyrinth sealing device is employed for the purpose of reducing a frictional loss in the shaft sealing device. The labyrinth sealing device includes a plurality of stages of labyrinth fins which are formed on a casing or the rotary shaft, and a layer of abradable coating to-be-bitten which is formed in the surface part of the rotary shaft or the casing opposing to the labyrinth fins. The clearances between the labyrinth fins and the rotary shaft or the casing are made narrower on the low-pressure side of the labyrinth sealing device than on the high-pressure side thereof.