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

横流风机在空调的内部机组中被频繁使用，并被强烈要求静音。本课题通过实验研究交叉流风机的几何参数与产生的风机噪声水平及流体动力特性之间的关系，建立了大型低噪声交叉流风机的设计方法。研究结果总结如下：1。阐明了风机机匣几何形状的影响：(a)风机机匣扩压部分存在一个最佳发散角，此时流体动力特性和噪声特性均达到最佳。(b)舌部上游机匣的几何形状控制了涡中心，影响了流体动力性能。(c)涡的位置既影响噪声又影响流体动力学特性。离转子旋转中心越远，离舌部越近，两者的性能越高。对内部流型的研究表明：(a)在机匣壁面涡旋与扩压器交界处静压急剧下降，在风机出口处静压渐近增加，直至大气压。(b)在涡旋机匣几何形状较好的情况下，这种急剧下降的速率较小。(c)在噪声和流体动力特性都较好的情况下，内部流动在管道中变得更加均匀。采用几何形状相似但尺寸不同的两个交叉流风机进行相似度研究，结果表明：(a)在同一风机中，雷诺数超过临界数（约1.6*10^4）时，相似度保持良好。(b)当流量不超过较小风机的最大效率点，但不超过其上的流量区域时，两种几何相似但尺寸不同的风机的噪声和流体动力特性具有良好的相似性。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