A centrifugal compressor includes a casing, a first impeller, a motor, a cooling medium delivery structure, a shaft, and a first bearing. The casing has a first inlet portion and a first outlet portion. The first impeller is attached to the shaft and disposed between the first inlet portion and the first outlet portion. A first axial gap exists between the first impeller and the casing. The shaft is rotatably supported and axially moveable with respect to the casing by the first bearing. The motor is arranged inside the casing to rotate the shaft. The cooling medium delivery structure is configured to vary a supply of a cooling medium to the casing.

An impeller clearance control apparatus for a centrifugal compressor includes a sensor and a controller. The controller controls a supply of a cooling medium to the casing based on a value detected by the sensor.

A cross-flow fan includes a shaft, a plurality of impellers, and a regulation portion. Each impeller has: an opening into which the shaft is inserted; fitting portions provided at a first end portion and a second end portion in an axial direction of the shaft such that the fitting portions at the first end portion and the fitting portions at the second end portion are fittable into each other; and a blade portion provided between the first end portion and the second end portion. The regulation portion is configured to regulate movement, in the axial direction, of each of the plurality of impellers connected in the axial direction by the shaft being inserted into the opening and the fitting portions being provided, the regulation portion regulating the movement of each impeller on both ends, in the axial direction, of the plurality of impellers. Thus, assembling process is simplified.

Examples are disclosed that relate to fans configured to automatically adjust for imbalances in mass. One example provides a self-balancing fan, comprising a hub comprising a plurality of blade interfaces, and a plurality of blade structures each attached to a corresponding blade interface of the hub, each blade interface comprising a tapered notch in the hub and being configured to increase a balancing force exerted by the hub against the blade structure as a function of increasing distance of the blade structure from the hub.

A fluid vacuum pump includes a motor assembly including a single motor or multiple motors, where one motor may be configured for operation in a first medium and another motor may be configured for operation in a second medium; an impeller assembly including a single impeller, which may of a fixed or variable configuration, or multiple impellers, where one impeller may be configured for operation in a first medium and another impeller may be configured for operation in a second medium; and a linkage operatively connecting and adjustably transmitting power from the motor assembly to the impeller depending on the type of medium present.

A fluid vacuum pump includes a motor assembly including a single motor or multiple motors, where one motor may be configured for operation in a first medium and another motor may be configured for operation in a second medium; an impeller assembly including a single impeller, which may of a fixed or variable configuration, or multiple impellers, where one impeller may be configured for operation in a first medium and another impeller may be configured for operation in a second medium; and a linkage operatively connecting and adjustably transmitting power from the motor assembly to the impeller depending on the type of medium present.