agricultural axial fan impellers for flow control of the aeroacoustic noise source on small axial fan using 微光外转子电机axialfanywf4e450s散热风扇220v机电轴流冷库风机 轴流散热风扇 0.38a 20cm 220v 20060 hy20060ha2bl fan axial ac 全新axialfan 12038 fm12038a2hst 220v 0.14a机柜散热排气扇12cm