Experiments were performed previously by the same author on a centrifugal blower fitted with impeller, the number of blades of which being 4, 8 and 16, with the results that the larger the number of blades the better the performance characteristics. It is easily expected, however, that the further increase of the number of blades will lower the performances of the blower as the resistance of impeller channels increases. To ascertain this, experiments were performed with different centrifugal blower with impellers fitted with straight radial blades, the number of which now selected to be z=2, 4, 8, 16, 20 and 32. The optimum number of blades, in this case, is found to be z=10~12, but these figures are not applied generally to all blowers, even if the blower types were the same. In this report, the relations between the slip coefficient of impeller and the number of impeller blades are surveyed both theoretically and experimentally to find a new formula which holds quite satisfactorily with high speed blower fitted with straight radial blades.
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