Effect of Flow in the Rotor on the Performance of a Sirocco Fan

Effects of blade shape on the performance of a Sirocco fan was measured using9runner blades with different blade shape in the same casing.These9different runner blades have inner diameter of 130 mm，outer diameter of 160 mm，and 46 mm in width.Considering from the velocity triangles at the blade inlet，the blade inlet angles are to be taken 10至15°。For the runner blades with these values the efficiency was good，but large discharge couldn‘t be obtained。Inlet angle must be taken in the range of 75-90°。The outlet angle is desired to be 150~160°。For these runner blades flow flows along the blade surface，though it once separates at the leading edge and reattaches at the trailing edge.The flow velocity takes large value at the pressure surface and smaller values at the suction surface at the center of the blade width.Deviation angle，i.e.，the difference of blade outlet angle and flow outlet angle，takes zero value，if proper design is conducted。The ratio of wake width to the blade pitch becomes larger，if the blade thickness is larger。If the blade outlet angle is larger than 160°，the outlet flow circulate。Inlet vortex arise because of the sudden flow turning at the blade inlet。The extent of inlet vortex is influenced by the inclination angle of blade。The inclination ratio，i.e.，the ratio of blade inclination angleθand the inlet angleβ-I D21--D2is important。The maximum values of pressure and discharge can be obtained at(θ/βI D21 ii D2)=0.35。Considering the above affairs，the valuesβI D 21 I D 2)=75~90°，(θ/βI D 21 I D 2)=0.35 andβI D 22 I D 2=150~160°are suitable for the blade design.The blade thickness must be thinner as possible.

Effects of blade shape on the performance of a Sirocco fan was measured using 9 runner blades with different blade shape in the same casing. These 9 different runner blades have inner diameter of 130 mm, outer diameter of 160 mm, and 46 mm in width. Considering from the velocity triangles at the blade inlet, the blade inlet angles are to be taken 10〜15°. For the runner blades with these values the efficiency was good, but large discharge couldn't be obtained. Inlet angle must be taken in the range of 75〜90°. The outlet angle is desired to be 150〜160°. For these runner blades flow flows along the blade surface, though it once separates at the leading edge and reattaches at the trailing edge. The flow velocity takes large value at the pressure surface and smaller values at the suction surface at the center of the blade width. Deviation angle, i.e., the difference of blade outlet angle and flow outlet angle, takes zero value, if proper design is conducted. The ratio of wake width to the blade pitch becomes larger, if the blade thickness is larger. If the blade outlet angle is larger than 160°, the outlet flow circulate. Inlet vortex arise because of the sudden flow turning at the blade inlet. The extent of inlet vortex is influenced by the inclination angle of blade. The inclination ratio,i.e., the ratio of blade inclination angle θand the inlet angle βィイD21ィエD2 is important. The maximum values of pressure and discharge can be obtained at (θ/βィイD21ィエD2) =0.35. Considering the above affairs, the values βィイD21ィエD2)=75〜90°, (θ/βィイD21ィエD2) =0.35 and βィイD22ィエD2=150〜160°are suitable for the blade design. The blade thickness must be thinner as possible.