对旋轴流式喷水推进泵压力脉动的数值计算

为了解喷水推进泵内部压力脉动特性,以对旋轴流式喷水推进泵为研究对象,应用计算流体动力学(CFD)方法,采用雷诺时均法并引入SST k-ω湍流模型使方程封闭,对对旋轴流式喷水推进泵进行设计工况下非定常数值模拟.经网格无关性检验后,计算得到的推进泵功率与扬程与设计值基本一致.在首级叶轮进口处,首、次级叶轮轮缘间隙处,轴向间隙及导叶进口处设置监测点,监测不同位置的压力脉动数据.得到各监测点的时域图和频域图并对各监测点压力脉动特性进行了对比分析.结果表明:对旋轴流式喷水推进泵内压力脉动主要受叶频的影响,首级叶轮和次级叶轮轮缘间隙处的压力脉动不仅与首、次级叶轮的叶片数有关,还与喷水推进泵叶轮数量有关;受两级叶轮反向旋转的影响,轴线方向上首级叶轮与次级叶轮之间轴向间隙处的压力脉动幅值最大, 轴向间隙的压力受到首级叶轮和次级叶轮的共同影响;次级叶轮出口与导叶进口处压力脉动主要受到导叶回流的影响.

Numerical calculation of pressure fluctuation in contra-rotating axial flow waterjet pump

The unsteady pressure fluctuations in an optimally designed contra-rotating waterjet axial flow pump are identified by using unsteady numerical simulation under design condition based on CFD method with the SST k-ω turbulence model. A mesh independence analysis shows that the calculated power and head are well consistent with the design data. The monitoring points are mounted at the inlet of front impeller, in the tip region of front and rear impellers, in the axial clearances and at the diffuser inlet. The time domain pressure fluctuation data are recorded at each monitoring point, meanwhile the pressure fluctuation characteristics are analyzed and compared in both time and frequency domains. The simulation results indicate that pressure fluctuation is mainly affected by blade passing frequency, however, the fluctuation in the tip region of the front and rear impellers depend on the number of blades and impellers. Influenced by reverse rotation of the two stage impellers, the pressure fluctuation amplitude in the axial clearance between the front impeller and the rear impeller is the maximum. The pressure fluctuations at the rear impeller outlet and diffuser inlet are mainly influenced by reverse flow from the diffuser.