叶顶形状对轴流风机气动噪声影响的数值研究

Aerodynamic Acoustic Characteristics of an Axial Flow Fan with Different Blade Tips

以某两级动叶可调轴流风机为例,采用Fluent软件对5种改进的叶顶形状下的风机性能进行了模拟,并引入大涡模拟和FW-H声学模型获得了不同叶顶形状下风机的噪声源分布和气动噪声特征.结果表明:5种叶顶形状均可有效提高风机性能,提升效果依次为逆流向斜槽、双斜槽、上阶梯叶顶和下阶梯叶顶,而顺流向斜槽仅在小体积流量下使得风机性能明显提升;叶顶形状改进后,叶顶泄漏涡的影响增强,造成叶顶区和叶片前缘噪声显著增大,为风机内主要噪声源;风机各区域的声压幅值均受显著影响,且越靠近噪声源,受影响越突出;该风机内噪声主要以中低频的旋转噪声为主,各区域噪声均在基频位置达到最大值,叶顶形状改进后声压级随频率增大发生小幅提高,频谱形态发生明显改变.

Taking a two-stage variable-pitch axial flow fan as an example, the performance of the fan respectively with five differently shaped blade tips was simulated using Fluent software, so as to obtain the distribution of sound source and acoustic characteristics based on large eddy simulation and FW-H noise model. Results show that all the five blade tips in different shapes can improve the fan performance, in which, the countercurrent-flow-grooved blade tip has the highest improvement effect, followed by the double grooved blade tip, the up-step blade tip and the down-step blade tip, while the current-flow- grooved blade tip only improves the fan performance at lower flow rates. After improving the tip shape of blade, the noise level at tip region and leading edge increases apparently, due to enhanced leakage vortex at blade tip, which are the main sound sources. The tip shape has a significant effect on the amplitude of sound pressure, especially in the area closer to the noise source. The noise within the fan is mainly of the low and medium frequency rotational type, and the noise in all regions reaches its peak value at the fundamental frequency. The blade tip grooving exhibits a slightly increased effect on the sound level resulted from rising frequency, and the morphology of frequency spectrum changes appreciably.