Sanyo Denki Co., Ltd.

Fujitsu Corporation

The University of Tokyo

Yoshihiko Aizawa

Honami Oosawa

Katsumichi Ishihara

Masahiro Suzuki

Akira Ueda

Tadashi Katsui

Atsushi Yamaguchi

Kazuhiro Nitta

Chisachi Kato

Akihiro Otsuka, Sr

Toshiyuki Nakamura

Naruhiko Kudo

Honami Osawa

Takashi Kaise

Seiji Nishimura

A counter-rotating axial flow fan with reduced noise at the target operating point achieved without modifying a front impeller, a rear impeller, or a middle stationary portion is provided. An annular rib including a projecting surface for generating turbulent flow is formed on an inner wall portion of a casing at a position off from the middle stationary portion to a side of the rear impeller, the projecting surface extending radially inwardly of the inner wall portion and extending continuously in the circumferential direction of the inner wall portion. A fluid striking the projecting surface for generating turbulent flow is partially disturbed to form a turbulent flow before entering an area in which the rear impeller is provided. The turbulent flow suppresses flow separation of a fluid flowing along the surfaces of rear blades of the rear impeller from the surfaces of the rear blades.

Counter-rotating axial flow fan

A counter-rotating axial flow fan with improved characteristics and reduced noise compared to the related art can be provided. Defining the number of front blades as N, the number of stationary blades as M, and the number of rear blades as P, and defining the maximum axial chord length of the front blades as Lf, the maximum axial chord length of the rear blades as Lr, the outside diameter of the front blades as Rf, and the outside diameter of the rear blades as Rr, the counter-rotating axial flow fan satisfies the following two relationships: N&#x2267;P&#x3e;M; and Lf/(Rf&#xd7;&#x3c0;/N)&#x2267;1.25 and/or Lr/(Rr&#xd7;&#x3c0;/P)&#x2267;0.83.

A counter-rotating axial flow fan in which the shape of stationary blades of a middle stationary portion is optimized to reduce noise is provided. Defining the maximum axial chord length of front blades as Lf, the maximum axial chord length of rear blades as Lr, and the maximum axial chord length of stationary blades as Lm, a relationship of Lm/(Lf+Lr)&#x3c;0.14 is satisfied. Defining the maximum dimension between the blade chord for lower surfaces of the stationary blades and the lower surfaces as K, the maximum axial chord length Lm of the stationary blades satisfies a relationship of Lm/K&#x3e;5.8.

A counter-rotating axial-flow fan may be controlled to improve both cooling efficiency and operating efficiency. A first motor and a second motor are started in a given starting mode. Then, if the temperature of an object to be cooled is higher than a given reference temperature, the rotational speed of the first motor and the rotational speed of the second motor are controlled in a predetermined cooling efficiency mode that gives priority to cooling the object to be cooled over the operating efficiency of the counter-rotating axial-flow fan. If the temperature of the object to be cooled is equal to or lower than the given reference temperature, the rotational speeds of the first and second motors are controlled in a predetermined operating efficiency mode that maintains the object to be cooled at a temperature equal to or lower than the given reference temperature and reduces the power consumption of the counter-rotating axial-flow fan.

Method of controlling counter-rotating axial-flow fan

An axial-flow fan with double impellers is provided that can produce a larger amount of air and a higher static pressure than can be achieved with conventional fans. The axial-flow fan with double impellers has a first axial-flow fan unit and a second axial-flow fan unit. The first axial-flow fan unit includes a first case, a first impeller and a plurality of webs that fix a first motor to the first case. The second axial-flow fan unit includes a second case, a second impeller and a plurality of webs that fix a second motor to the second case. The first case and the second case are coupled together to form a housing. The webs of the first axial-flow fan unit and the webs of the second axial-flow fan unit are combined together to form a plurality of stationary webs arranged in the housing. The number of front blades provided at the first impeller is set to five, the number of stationary blades is set to three, and the number of rear blades provided at the second impeller is set to four.

Counterrotating axial blower

Impeller for an axial fan

Axial fan with double impellers rotating in mutually opposite directions

Growing community of inventors

Nagano, Japan

Yoshihiko Aizawa