轴流泵失速工况下非定常流动特性研究

Analysis on Unsteady Stall Flow Characteristics of Axial-flow Pump

为了研究轴流泵在失速工况下的流动特性,对某原型立式轴流泵进行非定常数值计算,对比分析了设计工况以及失速工况下泵内部典型流动结构与压力脉动特性,揭示了失速工况下低频压力脉动的产生机理,利用真机压力脉动测试验证了数值计算方法的可靠性。研究表明:失速工况下叶片背面的前缘靠近轮缘一侧以及尾缘靠近轮毂一侧存在回流区;设计工况下叶轮进口处以及导叶体中段压力脉动主频为叶片通过频率,叶轮出口部位由于受到动静干涉作用,主频为导叶通过频率,导叶体出口部位由于远离旋转叶轮,叶频主导作用减弱;深度失速工况下泵内部压力脉动系数幅值显著增加,其中导叶体出口处G6点在深度失速工况下压力脉动系数幅值为设计工况的16倍;深度失速工况下叶轮出口处监测点P6、导叶体中段监测点G2以及导叶体出口监测点G6出现频率为0.83 Hz的低频压力脉动;失速工况下导叶体内涡核心区域与导叶流线图中存在的漩涡的发展、演化规律基本一致,两者的频率均为0.86 Hz,与低频压力脉动的频率(0.83 Hz)较为接近,因此可以证明低频压力脉动由导叶内漩涡诱导所致。

In order to study the rotating stall eharaeteristics of axial-flow punip, the unsteady internal flow field in a large axial-flow pump was numerically simulated. The Pro/E softtware was used to build tile pump model, which mainly consisted of inlet pipe, impeller, guide vane and outlet pipe. The unsteady flow was numerically simulated based on RANS solver and SST k-co turbulenee model. The real pump pressure pulsation was tested by high frequency dynamic pressure sensor. The streamlines and pressure pulsation in pump at different flow rates were explored. The experimental pressure pulsation results and the numerical results were close to each other, which illuminated the reliability of the numerical calculation method. The results showed that there were two reversed flow field areas in the leading edge elosely to shroud and trailing edge closely to hub of blade suction surface under rotating stall condition. The dominant frequency under designed condition in the impeller inlet and the middle of gt, ide vane was blade passing frequency. The dominant frequency under designed condition in the impeller outlet was guide passing frequency because of rotor- stator interaetion. The pressure pulsation coefficient amplitude was markedly increased under deep rotating stall condition. The pressure pulsation coefficient amplitude of monitoring point G6 at guide vane outlet under deep rotating stall condition was 16 times larger than that under designed condition. Low frequency pressure pulsation at 0. 83 Hz disappeared under deep rotating stall condition which was caused by a vortex in guide vane. The research had reference value for tile safe and steady operation of pump unit in large pumping station.