CENTRIFUGAL BLOWER

PROBLEM TO BE SOLVED: To reduce noise generation, to improve fan efficiency, and to reduce electric power consumption in a centrifugal blower used as ventilation blowers. SOLUTION: A multi-blade fan 1 comprises an inducer 8 which has an inside diameter Dii equal to or smaller than 0.6 of an outside diameter D of a fan, a sweep-forward angle θf smaller than a blade pitch angle θt, and is smaller than the number of blades 7. With such a multi-blade fan 1, an air flow 9 from an intake orifice 2 can be introduced to a blade inlet part 10 while suppressing turbulence. Therefore, it is possible to reduce the noise, and at the same time, to increase the work-load by increasing the load of the air flow 9 on the inducer 8. In addition, because a turning angle of an air flow 9 from the inside of the inducer 8 to the outside peripheral part of the blade 7 becomes small, the generation of a turbulence flow due to the separation from a blade surface 16 of the inducer can be suppressed. At the same time, it is possible to suppress noise generation and to improve the fan efficiency by reducing a number of the inducer 8 to be smaller than the number of the blades 7.