旋壳差速效应对旋喷泵性能影响

以旋喷泵为试验对象,完成了旋壳与叶轮同步变转速性能试验以及旋壳与叶轮非同步差速数值研究.为避免各向同性涡黏假设,数值计算选择雷诺应力RSM linear pressure-strain模型,将数值计算与试验结果对比以验证其可信度.结果表明:变转速试验中该泵的流量与扬程符合相似定律,最优效率基本保持不变,各转速下最优效率的最大偏差为3.1%,趋于常数.差速试验中旋壳转速在升高引起径向液体压力梯度增大,导致旋壳内任意位置半径r大于叶轮出口半径r₂区域的液体压力增加,而旋壳内任意位置半径小于叶轮出口半径区域液体的压力降低.受叶轮与旋壳差速扰动影响,集流管进口和尾涡区域湍流动能数值普遍较高,该区域能量损失大,涡的大小、形态、涡心位置随旋壳转速不断变化,主要分布在叶轮出口与流动中心区.与额定工况相比,旋壳转速的升高能够提高旋喷泵的扬程,但由内壁面带动液体快速旋转增加液体能量的方式会导致泵效率下降.旋壳转速在一定范围内的降低有利于能源的高效利用,提高泵效率,该泵试验范围内最优旋壳与叶轮转速比为0.75,研究结果对今后旋喷泵差速运行有指导意义.

Effect of differential rotating shell on roto-jet pump performance

Taking the roto-jet pump as test object, the performance test of rotating shell and impeller with synchronous variable speed and numerical study of non-synchronous differential speed between rotating shell and impeller were completed. To avoid the assumption of isotropic eddy viscosity,RSM linear pressure-strain model of Reynolds gravity was selected for numerical calculation and the numerical results were compared with the experimental results to verify its reliability.The results show that in the variable speed experiment, the flow rate and head of the test pump conform to the similar law, and the optimal efficiency remains basically unchanged. The maximum deviation of the optimal efficiency at each speed is 3.1% and tends to be constant.In the differential speed experiment, the rotating shell speed increased causes the radial liquid pressure gradient to increase, resulting in the increase of the liquid pressure in the area of r>r₂ and the decrease of the liquid pressure in the area of r2. Affected by the differential disturbance between impeller and rotating shell,the turbulent kinetic energy values in the inlet and wake region of the collecting pipe are generally high and the energy loss is large. The size, shape and position of vortex center change with the rotating speed of rotating shell and are mainly distributed in the impeller outlet and flow center area. Compared with rated working condition, increa-sing the rotating speed of shell will improve roto-jet pump head, but increasing liquid energy depends on rotating shell wall friction and reduces the efficiency of the pump. The lower rotating speed of the rotating shell within a certain range is beneficial to improve the pump efficiency. Optimal rotating speed ratio between rotating shell and impeller is 0.75.The results are helpful for differential operation of roto-jet pump in the future.