| 摘要 |
PURPOSE:To remove the cause of noise generation and improve the ventilating efficiency by improving the shape of a blade and the fitting angle of a blade which forms a blade wheel rotated in a bell mouth. CONSTITUTION:The ratio between the radius of curvature R in a distance (hf) from the top of a forward blade 3 to a bell mouth part and the radius of curvature (r) in a distance (hb) from the bell mouth part to a rearward blade 4, that is, the ratio r/R is designated in the range of 0.6-0.85. The maximum total effect of the reducing of noise and of the improving of ventilation quantity is obtained by the structure due to said ratio. An air flow 9 passing through the bell mouth part is flowed in the direction of a synthesized vector 12 which is synthesized with a velocity vector 11 in centrifugal direction and a velocity vector 12 in horizontal direction. Accordingly, a swirl 13 is generated by the impact of the air flow against the front surface of a bell mouth 6. By the forward inclinating of the blade within the range of 5-15 deg. to the wind blowing direction 8 side, the cause of the swirl can be removed by the changing of the direction of the vector 12. |
