蜗壳形状对离心泵流动诱导噪声的影响

由于蜗壳对离心泵流动诱导噪声的产生及传播具有重要影响,在原马蹄形断面蜗壳的基础上重新设计了一种矩形断面蜗壳,并将两种断面的蜗壳与同一叶轮组合进行流场数值模拟和声学求解.流动诱导噪声的求解基于Lighthill声类比理论,采用大涡模拟和声学有限元法相结合的混合算法.在原型泵的基础上还分析了采用矩形隔舌和圆角隔舌的扬程、效率和声学性能差异,并对模拟结果进行了试验验证.计算结果表明:矩形断面蜗壳模型泵和马蹄形断面蜗壳模型泵的水力性能近似;2种断面模型泵内流动诱导噪声的主频均为叶片通过频率290 Hz;从内部流场的压力云图、速度矢量分布及方向分析可发现矩形断面蜗壳内的流动状态更佳;相对于马蹄形断面蜗壳,采用矩形断面蜗壳模型泵的声压级平均小5 dB,声学性能更优;相对于矩形隔舌模型,采用圆角隔舌模型泵的水力性能更优,声学性能也较好,声压级平均小4 dB.

Effects of cross-section and cut-water shapes of volute on flow induced noise in centrifugal pumps

Volutes have significant impact on the generation and propagation of flow-induced noise in centrifugal pumps. A volute with rectangular cross-section is designed to replace the original one with horseshoe-shaped cross section; subsequently, fluid dynamics simulation and acoustics computation are carried out in a centrifugal pump which is composed of the same impeller and either newly designed or original volute. The generation and propagation of flow-induced noise in the pump is solved by using a hybrid algorithm in which large eddy simulation and acoustic finite element analysis are combined based on the Lighthill acoustic analogy theory. The effects of cut-water of the volute on the pump head, efficiency and acoustic performance are also analyzed by employing two cut-water shapes, namely sharp and round edges. Some simulation results are verified by the existing experimental data. The analysis results show that both kinds of volute produce a similar hydraulic performance and result in a 290 Hz dominating frequency, i.e. blade passing frequency, for the noise. The volute with rectangular cross-section exhibits a better flow pattern than that with horseshoe-shaped cross-section according to the pressure contours, velocity vector distribution and flow direction inside the two pumps. Further the volute with rectangular cross-section lowers the averaged sound pressure level by 5 dB, showing an improved acoustic performance. Compared with the volute with sharp edge cut-water, the volute with round edge cut-water not only demonstrates a better hydraulic performance, but also possesses a more attractive acoustic behavior in account of 4 dB averaged sound pressure level reduction.