A centrifugal fan noise-lowering structure includes a frame having an upper and a lower cover and a sidewall, which together internally define a receiving space communicable with an air inlet and an air outlet of the frame; a stator assembly located in the receiving space and fixedly mounted on the lower cover; and a rotor assembly correspondingly assembled to the stator assembly. The receiving space is internally defined a high pressure zone and a low pressure zone. The upper cover is provided with an airflow passage, which has an inlet located at a position corresponding to the high pressure zone, and an outlet located at a position corresponding to the low pressure zone. With the airflow passage, air in the high pressure zone can be guided to jet out to the low pressure zone to thereby reduce noise produced by the centrifugal fan during its operation.

An electronic system includes a fan module, an embedded controller, an error microphone, an active noise cancellation controller, and a micro speaker module. The error microphone is configured to output an error signal by detecting the noise level during the operation of the electronic system. According to the error signal and the fan information provided by the embedded controller, the active noise cancellation controller calculates the narrow-band noises associated with the actual single-blade fundamental frequency noise and the actual BPF fundamental frequency noise generated by the fan module, and drives the micro speaker module accordingly for providing a noise cancellation signal. The error signal may be reduced to zero by adaptively adjusting the noise cancellation signal for canceling the noises generated during the operation of the electronic system.

Provided is an axial flow blower capable of improving an intake efficiency even when air is introduced from a plurality of suction openings. An axial flow blower includes a housing including an air blowing passage extending from a plurality of suction openings (lateral suction opening and lower suction opening) to an ejection opening, an electric motor, and an air blowing fan that blows air from the plurality of suction openings (lateral suction opening and lower suction opening) toward the ejection opening. An air blowing guide member is provided closer to the plurality of suction openings (lateral suction opening and lower suction opening) than to the air blowing fan, inside of the plurality of suction openings (lateral suction opening and lower suction opening). The air blowing guide member guides air introduced into the air blowing passage from the plurality of suction openings (lateral suction opening and lower suction opening) toward the air blowing fan.

A blower unit, particularly for an apparatus for assisting respiration, comprises a housing (2), an impeller (1) accommodated in an impeller chamber (3) in the housing (2), and a motor (12), connected to the impeller (1) via a shaft (15), which is accommodated in a motor chamber (13) in the housing (2). The motor (12) is fixed between walls (14, 18) of the motor chamber (13) by means of buffers, with at least one of the buffers being a sealing ring (16) which separates the shaft (15) from a passage for cooling air (33) which, in radial section, extends annularly around the motor (12).

A centrifugal fan includes a housing and an impeller. The housing includes a sidewall, and the sidewall includes a tongue portion. The impeller includes a fan hub and a plurality of blades. The fan hub is rotatably disposed in the housing, and the tongue portion has an inner contour line on a reference plane. The blades connect to the fan hub. Each one of the blades has an end surface facing the sidewall. The end surface has an outer contour line on the section of the blade. Any two adjacent blades have different outer contour lines. The outer contour line of at least one first blade of the plurality of blades is parallel to the inner contour line. The outer contour line of at least one second blade of the plurality of blades is not parallel to the inner contour line.

Provided is a refrigeration machine provided with: a refrigeration cycle having a compressor, a condenser, an expander, an evaporator, and piping (12) which sequentially connects the compressor, the condenser, and the expander; and an acoustic device (13) having a space formation section (14) which has one end (14a) connected to the piping (12) and in which a space is formed, the acoustic device (13) also having a vibration body (20) which is affixed integrally to the other end of the space formation section (14) and which has a lower natural frequency than the space formation section (14).

A vehicle heater includes a heater housing (12′), through which heating air to be heated can flow, with a heating air inlet area and with a heating air outlet area. A burner unit is arranged in the heater housing. A combustion air blower (46′) is arranged in the heater housing for delivering combustion air to the burner unit. A heat exchanger unit is arranged in the heater housing (12′). Heating air flowing through the heater housing (12′) can flow around the heat exchanger unit. A combustion air intake muffler (76) is arranged essentially in the heater housing (12′). A muffler housing (78) made in one piece with the heater housing (12′) is associated with the combustion air blower (46′).

An apparatus for cleaning aquaculture nets underwater. The appartus employs a propeller housing with a centrally disposed axis with a plurality of propeller blades extending therefrom. An outer perimeter ring secured to an outer tip of each propeller blade with a plurality of knuckles secured to the outer perimeter ring. Each knuckle including a curved surface constructed and arranged to strike the aquaculture net upon rotation of the blades for removal of growth by impact and shaking of the aquaculture net.

A fan frame body structure includes a first frame body. The first frame body has a first upper end, a first lower end, a first frame wall and a first main flow way. The first main flow way passes through the first frame body and is formed with a first main inlet and a first main outlet respectively at the first upper end and the first lower end. A first subsidiary flow way is disposed in the first frame wall. The first subsidiary flow way is in parallel the first main flow way. The first subsidiary outlet is positioned at the first upper end of the first frame body in flush with and in adjacency to the first main inlet.

A fluid pressurizing structure and fan using same are disclosed. The fluid pressurizing structure includes a hub having a plate portion located therearound. The plate portion has a first and a second surface provided with a plurality of first and second hollow protrusions, respectively. Each of the first hollow protrusions has a first fluid inlet and a first fluid outlet, and each of the second hollow protrusions has a second fluid inlet and a second fluid outlet. The first and second fluid outlets extend through the plate portion to communicate the first and second fluid inlets with the second and first surface, respectively. When the fan rotates, fluid drawn thereinto sequentially flows through the first fluid inlets and outlets and the second fluid inlets and outlets in a helical movement in cycles, and is therefore continuously pressurized, which facilitates reduced fan vibration and noise and fan motor power consumption.