离心泵瞬态空化流动及压力脉动特性

Characteristics of transient cavitation flow and pressure fluctuation for a centrifugal pump

基于RNG k-ε湍流模型及输运方程空化模型,考虑空化流动可压缩性影响修正湍流模型,考虑湍流压力脉动对饱和压力影响修正空化模型,对小流量工况离心泵瞬态空化流动进行数值模拟,计算所得扬程随进口压力变化曲线与试验结果吻合较好,能较准确预测离心泵在空化临界点扬程陡降过程。在离心泵叶轮流道中间与叶片压力面、吸力面布置监测点,对比分析非空化、空化时叶轮内压力脉动特性。结果表明:叶轮内压力脉动主频为叶轮转频;在叶轮流道及叶片吸力面,叶轮内压力脉动最大幅值由进口至出口逐渐增大,而在叶片压力面,压力脉动最大幅值在叶片进口4/5处最大。空化流动各监测点压力脉动最大幅值大于非空化,在流道进口处约为非空化时2倍。受蜗舌结构影响,叶轮内各流道空化区域分布不均匀。

The transient cavitation flows in a centrifugal pump with small flow rate were numerically simulated using RNG k-e turbulence model and the transport equation cavitation model, both models were modified by taking the influence of the compressibility of fluid on turbulence and the effect of pressure fluctuation on saturation pressure into consideration. The calculated variation of pump head with pump inlet pressure agreed well with the test data. The results demonstrated that the numerical model and method can accurately predict the cavitation flows in a centrifugal pump. The characteristics of pressure fluctuation with and without cavitation were compared and analyzed. It was shown that the dominant frequency of pressure fluctuation in an impeller is the rotating frequency; from the impeller inlet to outlet, the maximum amplitudes of pressure fluctuation in flow passage and blade suction side gradually increase; but the maximum amplitude reaches the largest value at the 4/5 length of the blade from the blade inlet side for the blade pressure induced by the flow separation in this area; the pressure fluctuation maximum amplitude of the cavitation flow is larger than that of the non-cavitation flow, the former is about 2 times of the latter at the flow passage inlet ; with the influence of asymmetric structure of volute tongue, the distribution of cavitation in the impeller is not uniform.