不同形式高速离心叶轮内部流动的数值模拟

为分析叶轮结构对于叶轮内部流动的影响,对8叶片的闭式和半开式两种形式低比转速高速离心复合叶轮进行研究.采用S-A湍流模型和雷诺时均N-S方程,对叶轮内部的流动进行三维紊流数值计算和分析,并对离心泵进行试验研究.数值计算结果表明,两种形式叶轮内部都存在回流,其中半开式叶轮内部的回流区域较少,液流在间隙里的相对流动大致为圆周方向;叶轮内部的静压力都是由叶片进口到出口逐渐升高,等静压曲线几乎是沿圆周方向,半开式叶轮叶片顶部的静压力低于相应位置根部的静压力,闭式叶轮出口的压力系数高于半开式叶轮.试验结果表明,半开式叶轮离心泵的效率较高,说明叶轮内部的回流是影响离心泵性能的重要因素.

NUMERICAL SIMULATION OF INNER FLOW IN DIFFERENT-TYPE HIGH SPEED CENTRIFUGAL IMPELLERS

To analyze the effect of dsfferent impeller type on inner flow in impeller, two low-specific-speed high-speed com- plex impellers with eight blades are investigated whose types are closed and semi-open. Using the Spalart-Allmaras turbu- lence model and the Reynolds-Averaged Navier-Storkes equa- tions, the three-dimensional turbulent flow fields in impellers are analyzed numerically. And the experimental studies on the centrifugal pump are carried out. The simulation results show that there all exists back flow region in impellers, the back flow region is few and the relative flow in clearance is alone the circumferential orientation in the half-open impeller, the static pressure in impellers rises gradually from blade inlet to outlet whose contours are almost alone the circumferential orientation, the static pressure of blade tip is bigger than that of blade root in the same radius of the blade in half-open impeller, and the static pressure coefficient at outlet of closed impeller is larger. The experimental results show that the efficiency of the half-open impeller is higher and the back flow has important influence on the performance of pump.