Abstract
Combining the fan aerodynamic efficiency with the wind tunnel pressure loss coefficient, a new equation which points out the inherent relationship of the fan blade setting angle, fan rotating speed and gas flow rate in wind tunnel circuit is derived according to the two-dimensional flow theory of the axial fan rotor blades and the aerodynamic characteristics of the low speed wind tunnel. So a new method for setting angle adjustment of fan rotor blade to satisfy the fan performance at off-design point by getting the test results of fan operation parameters but without the fan total pressure rise in the low speed wind tunnel is developed. Flowing the new method, the setting angle adjusting value of fan rotor blade was provided only with the fan rotating speed and flow velocity in the test section of a low speed wind tunnel directly before the fan setting angle altered, the adjusting target was achieved by the new blade setting angle successfully and the time and cost of the wind tunnel commissioning test were saved. The test results show that, after increasing the fan rotor blade setting angle by 4.5 degrees, when the flow velocity in the wind tunnel test section reaches 60 m/s, the fan rotating speed is 570 r/min, the deviation from the predicted fan rotating speed value of 575 r/min is 0.9%. For the same test section flow velocity, the predicted value of the fan rotating speed is in a good agreement with the real value, it proves that this method is reliable and accurate in practical application.
Highlights
[1] SARRAF C, NOURI H, RAVELET F, et al Experimental Study of Blade Thickness Effects on the Overall and Local Perform⁃ ances of a Controlled Vortex Designed Axial⁃Flow Fan[ J]
Experimental Thermal and Fluid Science, 2011, 35: 684⁃693
Summary
扇效率,在风扇设计时,一般采用孤立翼型设计法, 避免叶间干扰带来的效率损失;通过选择合理的风 扇直径、桨毂比及转速等参数,严格控制风扇叶尖速 度;通过优化叶片数目及桨叶剖面的翼型弦长控制 径向各位置实度,尽可能地避免风扇运转中三维效 应对其气动性能的影响[11⁃12] 。 风扇一般由桨叶、止 旋片、整流罩和外壳体构成,如图 1 所示。 为实现不获取风扇具体的压升及效率信息,而 进行风扇安装角的调整及性能预测,首先要分析风 扇桨叶剖面速度三角形中各项参数的固有关系,常 规风洞轴流风扇叶剖面的速度构成如图 2 所示。 风 扇运行过程中,以风扇桨叶径向位置 r 的坐标系作 参考,则轴向、周向气流在叶剖面构成的速度三角形 为图 2 中 的 △AEB。 气流轴向相对速度U = | EB | 。 气流通过桨叶做功后, 会在叶剖面后方产 要建立 εS 和 φ 的关系,还需要求解(4) 式中的 sin(φ - ψ) ,由图
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