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

贯流风机是空调机内部的常用风机，对风机的静音性能要求很高。本文通过实验研究了贯流风机的几何参数与风机噪声级及流体动力特性的关系，建立了大型低噪声贯流风机的设计方法。主要研究结果如下：1.关于风扇壳体的几何形状的影响，阐明了：（a）风扇壳体的扩散器部分存在最佳发散角，在该最佳发散角处，流体动力学和噪声特性都变得最佳。(b)舌部上游的壳体的几何形状控制涡流的中心，这影响流体动力学性能。(c)涡流的位置影响噪声和流体动力学特性。离转子旋转中心越远、离舌部越近，两者的pe值越高 关于我们 改进成为.2.内部流态的研究表明：（a）在蜗壳和扩压器之间的边界处，静压急剧下降，并逐渐增加到大气压力向风扇的出口。(b)在蜗壳的几何形状较好的情况下，这种急剧下降的速率较小。(c)在噪声和流体动力学特性都较好的情况下，管道内的流动变得更加均匀.利用两个几何形状相似但尺寸不同的贯流风扇进行的相似性研究表明：（a）在同一风扇中，当雷诺数超过临界数（约为1.6*10^4）时，相似性保持良好。(b)噪声和流体动力学特性的相似性在两个几何相似但尺寸不同的风扇之间保持良好，如果流量不超过较小风扇的最大效率点，但不在流量区域内。减

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