Development of a large-scale, low-noise, cross-flow fan

空调内件经常使用横流风机，强烈要求保持安静。本文通过实验研究了横流风机几何参数与风机噪声水平及流体力学特性之间的关系，以期为大型低噪声横流风机的设计提供依据。主要研究结果如下：1.在风机壳体几何形状的影响下，阐明了：(A)存在一个最佳的风扇壳体扩散器部分的扩散角，在该角度下，风扇壳体的流体动力特性和噪声特性都达到最优。(B)舌体上游的壳体几何形状控制着涡流中心，从而影响流体动力性能。(C)旋涡的位置对噪声和流体动力学特性都有影响。离转子旋转中心越远，离舌部越近，两者的PE…越高。更多的表演变得越来越多。对内部流型的研究表明：(A)蜗壳壁上涡旋和扩散器交界处的静压急剧下降，并逐渐增加到通风机出口的大气压力。(B)涡旋蜗壳的几何形状越好，这种急剧下降的速度就越小。(C)在噪声和流体动力特性都较好的情况下，内部流动在管道内变得更加均匀。对两台几何相似但尺寸不同的横流风机的相似性研究表明：(A)在同一风机中，当雷诺数超过临界值(约为1.6×104)时，相似性较好。(B)如果流量不超过较小风机的最大效率点，但流量不超过其上方的流量区，则两台几何相似但尺寸不同的横流风机之间的噪声和流体动力学特性都具有良好的相似性。较少

Cross flow fans have been frequently used in the inner units of air conditioners and strongly requested to be quiet. In this research projict the relation between the geometrical parameters of a cross flow fan and the generated fan noise level as well as the fluid-dynamic characteristics has been experimentally investigated to create the designing method of large-scale, low-noise, cross-flow fans. The results are summarized as follows :1. On the effects of the geometry of the fan casing it is clarified : (a) There is an optimum divergent angle of the diffuser part of the fan casing, at which both the fluid dynamic and the noise characteristics become optimum. (b) The geometry of the casing upstream of the tongue controls the center of the vortex, which affects the fluid-dynamic performance. (c) The location of the vortex affects both the noise and the fluid dynamic characteristics. Farther from the center of the rotation of the rotor and the closer to the tongue, the higher the both pe … More rformances become.2. The investigation of the internal flow pattern reveals that : (a) The static pressure decreases sharply at the boundary between the scroll and the diffuser in the casing wall and asymptotically increases up to the atmospheric pressure toward the exit of the fan. (b) The rate of this sharp decrease is smaller in the case of the better geometry of the scroll casing. (c) In the case both the noise and the fluid dynamic characteristics are better the internal flow becomes more uniform across the duct.3. The investigation of the similarity by using the two cross-flow fans which are geometrically similar but different in size reveals that : (a) In the same fan the similarity holds good in the case the Reynolds number exceeds the critical number, which is about 1.6*10^4. (b) The similarity of both the noise and fluid dynamic characteristics holds good between the two geometrically similar but different in size if the flow rate does not exceed the maximum efficiency point of the smaller fan, but not in the flow rate region over it. Less