CROSS FLOW IMPELLER

PROBLEM TO BE SOLVED: To reduce fan rotating noise, and simultaneously suppress generation of noise of a low frequency band of a specified value or less by providing with a plurality of impellers between a plurality of separating plate which is transversely to a rotary shaft, and arranging the installing the position of the impellers at an interval of a specified condition. SOLUTION: An impeller 4 is formed at an arranging angle θ which is regulated an impeller installing position on an impeller 1, a referential impeller 2, and a separating plate 3. Impeller installation is displayed by the formula of a position angle which is relation to θk=θk0+α.dθSin(β.θo)k(θk; an arranging angle regulated the installing position of the impeller, θko; an arranging angle in the case arranged at an equal interval, α; an arranging angle fluctuation rate, dθ; an inter-blade angle at the equal interval, β; a cyclic degree, θo; an impeller arranging referential angle, k; an impeller number in the case where an impeller arranged at the referential angle is set to 0). Since the installing position of the impeller 1 is fluctuated cyclicly, modulation is applied on a fan rotary noise related to the number of the impeller, a peak level is dispersed, and a noise level is reduced. It is thus possible to suppress the noise level.