A New Method for Adjusting Setting Angle of Rotor Blade for Axial Fan in Wind Tunnel

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. 依据轴流风扇二维叶素理论及低速风洞回路气动特性，将风扇效率及风洞损失系数作为关键参数，推导出风扇在非设计点时，风扇桨叶安装角与风扇转速、气体流量之间的固有关系，由此发明了一种不需要测试风扇压升，仅根据风扇基本运行参数即进行风扇非设计点安装角调整的新方法。某风洞风扇的调试过程中，在测试得到风扇转速与试验段风速对应关系的基础上，利用该方法，直接计算出风扇安装角的调整量，一次成功。试验结果表明，在风扇安装角调大4.5°后，风洞试验段风速60 m/s对应的风扇转速为570 r/min，与预测值575 r/min偏差0.9%，预测值与实际值吻合较好，由此证明了此方法在工程运用中的可靠与准确性。