A return channel for a centrifugal turbo machine. The return channel includes a plurality of return channel vanes, arranged around a return channel axis. Each return channel vane includes: a leading edge at a first distance from the return channel axis, a trailing edge at a second distance from the return channel axis, the second distance being smaller than the first distance. A respective flow passage is defined between each pair of adjacently arranged return channel vanes. The return channel vanes are arranged with a non-constant pitch around the return channel axis.

A cross-flow fan, and blades of a cross-flow fan are provided. The cross-flow fan includes a rotary shaft; a plurality of blades that extends in a direction parallel to the rotary shaft and having a positive pressure surface and a negative pressure surface; and a connector that connects the rotary shaft and the plurality of blades. At least one protrusion that protrudes in a thickness direction and extends in a longitudinal direction of the plurality of blades is formed on the plurality of blades, and by means of the at least one protrusion formed on a blade surface, a flow separation phenomenon caused by friction with the blade surface is suppressed, thereby reducing noise generated by the cross-flow fan.

A compressor includes a housing having an inlet and an outlet and a fluid flow path extending between the inlet and the outlet. An impeller is mounted within the housing and is movable to move a fluid from the inlet along the fluid flow path to the outlet. A plurality of flow interference elements is arranged within the housing at one or more locations along the fluid flow path. When a fluid flows through the fluid flow path in a backwards direction of flow, a disturbance is generated in the fluid adjacent each of the plurality of flow interference elements.

An axial fan includes an impeller rotatable about a central axis extending in a vertical direction, a motor, and a housing. The motor includes a stator and a rotor. The impeller includes blades on a radially outer surface of an impeller cup fixed to the rotor. The housing includes a motor base portion below the motor to support the stator, a tubular portion radially outside of the impeller, a first rib below the blades to join the motor base portion to the tubular portion, and a second rib being annular, centered on the central axis, and joined to the first rib. A lower edge of each blade includes a first blade region that is convex downward. A radially inner end of the second rib is radially outward of a lower end of the first blade region.

A blowing system includes: a first blowing unit including a first body that houses a first fan and includes a first air outlet for blowing-out wind from the first fan; a second blowing unit including a second body that houses a second fan, includes a second air outlet for blowing-out wind from the second fan, and has a shape that is in two-fold symmetry with the first body; and a first connection that rotatably-connects an edge on a back face-side of a first side face of the first body and an edge on a back face-side of a second side face of the second body so that an angle formed by the first and second bodies is variable. The first and second blowing units come into contact at three or more points, and the directions of respective rotation axes of the first and second fans cross at a predetermined angle.

A method for controlling a fan in a fan start-up stage including a first time period and a second time period comprises the following steps of: during the first time period, continuously providing a first driving signal to drive the fan; and during the second time period, continuously providing a second driving signal to drive the fan; wherein, during the first time period the signal value (driving energy) of the first driving signal gradually decreases until being equal to the signal value of the second driving signal, and the signal value of the first driving signal is initially greater than the signal value of the second driving signal. A fan is also disclosed.

A vertical multi-stage pump includes a rotation shaft extending in a vertical direction, a plurality of impellers fixed to the rotation shaft, a multi-stage pump chamber accommodating the plurality of impellers and comprising a suction port for a first-stage impeller at a lower end, a lower casing comprising a suction nozzle extending in a horizontal direction and forming a communication space communicating the suction nozzle and the suction port, and an inner cylinder member interposed between the multi-stage pump chamber and a lower casing and expanding the communication space in a vertical direction.

A fan includes an air cylinder and an air outlet hood. An interior of the air cylinder is hollow to form a hollow cavity. The air cylinder has an air inlet and an air outlet. The air outlet hood is detachably disposed on the air outlet. The air outlet hood is provided with an annular air outlet for air outlet. An outer ring and/or an inner ring of the annular air outlet is formed with an annular guide rib extending toward the air inlet. The annular guide rib is configured to make an airflow cross section adjacent to the annular air outlet gradually decrease, so as to make an airflow in the air outlet hood cohesive, thereby increasing an air outlet speed of the annular air outlet. A hair dryer having the fan is also disclosed.

A cleaner reduces noise. The cleaner includes a motor, a fan including a number Z of blades and rotatable at a rotational speed N, indicating revolutions per minute, about a rotation axis by the motor, a cover having an inlet located frontward from the fan, and a number V of ribs located in the inlet. The ribs extend in a radial direction from the rotation axis and are arranged in a circumferential direction about the rotation axis. The fan is rotatable to produce noise having a frequency f.sub.NZ of 20,000 Hz or higher, and f.sub.NZ=(m−k×V)×N/60 and m=n×Z+k×V, where n is an order, m is an integer, and k is an integer.

A ventilation fan with illumination includes a housing, a fan, and lighting equipment in the housing. The housing includes a first opening communicating with an air outlet, the first opening communicating with a duct, and a second opening that communicates with an interior space, The lighting equipment includes a light, a cover in the housing that surrounds the light periphery, the cover reflecting light and transmitting the light into the space through the second opening, and a restrictor that restricts passage of air between the light periphery and the lighting cover. An air intake gap is provided between a lower end of the cover and an edge of the second opening and introduced through the second opening and the air intake gap, is discharged through the first opening into the duct, the edge of the second opening being located below the lower end of the cover.