动叶异向偏转对轴流风机失速的影响

Influence of abnormal deflection of abnormal blade on stall of axial fan

采用非定常数值模拟的方法捕捉失速现象,研究失速机理,所选择的对象为动叶可调式轴流风机,模型一的动叶安装角正常,模型二存在两个偏转角度为-9°和+9°的异常叶片。通过计算可以得知:两只异常叶片改变了同流量下风机的出口静压,但未改变风机运行的稳定范围。同正常叶片的失速变化过程相同,异常叶片的风机也会沿着失速预兆的发生、发展、合流,直到最终变成完整失速团这4个步骤。+9°异常叶片吸力面顶部是失速先兆的源头,而-9°异常叶片附近的流场相对平稳。异常风机产生失速先兆时刻的湍动能峰值较正常风机低72. 7%,形成完整失速团时刻的湍动能峰值较正常风机低41%,可见,异常叶片不但使失速先兆出现的时间前移,还减少了失速团的演化周期,该结论扩展了异常叶片影响失速变化过程的理论。

Taking a two-stage axial fan with adjustable vanes as the research object, the 3D unsteady numerical simulation was conducted on the axial fan with abnormal installation angles of the second rotor based. The abnormal installation angles of two adjacent blade in the second rotor were-9°and +9°,and the other is normal fan. The numerical results show that although the abnormal blade changes the static pressure of the fan, the stable operating range of the fan is unchanged. The stall change process being the same as the normal fan , the fan with ±9 abnormal angle experiences four stages before entering stall: appearance, development, merging and developing into stall cell. The top of suction surface in +9°blade is the source of stall precursor, and the flow field is stable around -9°blade. The peak value of turbulent kinetic energy in the abnormal fan is 72.7% lower than that of normal fan when the stall precursor appears and 41% lower when the complete stall cell has been formed. It can be seen that the abnormal blades not only advance the time of stall precursor, but also reduce the evolution of stall cell. The conclusion of the paper extends the theory about abnormal blade and stall.