螺旋离心泵叶片变螺距型线方程

Variable-pitch profile equation of screw centrifugal pump

根据螺旋离心泵的结构特点,基于叶片式流体机械内固液两相双流体模型的流速比理论,分析了螺旋离心泵叶片型线的螺距变化规律,推导出固液两相流螺旋离心泵叶片变螺距型线的参数方程.依据给定的设计参数和固相体积分数,采用推导出的叶片型线方程设计出叶片型线,并生成叶片三维模型,叶片表面光滑平整.对该叶片形成的水力模型进行了外特性清水试验,并用该三维模型对固相体积分数分别为5%,10%和15%时的固液两相流动进行了数值分析.结果表明:介质为固液两相流时泵的效率较输送清水介质时有所提高,特别是在设计工况,当固相体积分数等于设计给定值时,泵的效率可提高8.5%;当偏离给定的固相体积分数值时,效率有所降低;在输送固液两相流介质时泵的扬程较输送清水时的扬程有所降低,且随着固相体积分数的增大扬程逐渐降低.

According to the structure characteristics of impeller of a screw centrifugal pump, the streamwise evolutionary pattern of blade pitch was analyzed by applying the theory of relative velocity ratio of liquid-solid two-phase flow model for an impeller pump, and then a parametric equation for variablepitch was deduced. For the given hydraulic performance parameters and a volume fraction of the solid phase at the design point, a smooth, three-dimensional blade profile could be established through the parametric equations. The water performance of a screw centrifugal pump whose blades were designed in that way was measured, and accordingly its performances of liquid-solid two-phase flow were estimated numerically at three volume fractions of 5% , 15% and 25% with a CFD code, respectively. The results show that the pump efficiency for transporting solid-liquid two-phase medium is better than for transporting water. At the design point, for a given volume fraction of solid phase, the pump efficiency is increased by 8.5 % ; however, when the volume fraction is different from that given value, the pump efficiency is reduced. Compared with water single phase flow, the pump head of liquid-solid two-phase flow is not only decreased, and but also lowered gradually with increasing solid-phase concentration.