摘要
为了研究液力透平变工况时的瞬态特性,基于雷诺时均Navier-Stokes方程和标准k-ε湍流模型,对液力透平内部流场进行全三维非定常数值模拟,获得了变工况下液力透平内部流场的瞬时压力脉动、轴向力和径向力的变化规律.结果表明:变工况条件下,液力透平内部的瞬时压力脉动更为明显,小流量工况时静压力虽小,但压力脉动幅度最大,大流量工况的压力脉动幅度次之,最优工况时的压力脉动幅度最小;转轮进口动静耦合面处各个位置的压力脉动幅度与所处的位置有关,蜗壳环形出口位置的压力脉动较大,隔舌处压力脉动较小,压力脉动幅度随着流量的增大而增大;转轮进口动静耦合面和进出口的压力脉动主频等于叶频(转动频率与叶片数的乘积);液力透平在各个工况下均有径向力和轴向力存在,变工况下瞬时径向力的矢量分布近似圆形,瞬时轴向力在一个周期内变化趋势为先减小后增大,且存在最小值区域;流量越大,径向力和轴向力越大.
In order to study the transient characteristics of hydraulic turbine under variable working conditions, an unsteady three-dimensional simulation of internal flow field in a hydraulic turbine is performed based on the Reynolds time-averaged governing equations and standard k - ε turbulence model, the characteristics of transient pressure pulsation of internal flow field, radial and axial forces acting on the impeller are presented. The results show that the transient pressure pulsation is more obvious under variable conditions, though static pressure is smaller under low flow conditions, the pressure pulsation amplitude is the largest. The pressure pulsation amplitude is the smallest at best efficiency point, while the amplitude is following under high flow conditions. The pressure pulsation amplitude in the interface between the impeller and the volute depends on monitoring positions, also a more violent amplitude is found at the volute discharge, a smaller one occurs in the tongue. The pressure pulsation amplitude rises with increasing flow rate. The dominant frequencies of pressure pulsation in the interface, at the inlet and outlet are equal to the blade passing frequency. There are radial and axial thrusts under various operating conditions. The distribution of transient radial force vector is approximately circular, but the transient axial force declines with reducing flow rate or vice versa and exhibits a nearly periodic vibration pattern with a minimum value. ：
出处
《排灌机械工程学报》
EI
CSCD
北大核心
2017年第3期200-206,共7页
Journal of Drainage and Irrigation Machinery Engineering
基金
国家自然科学基金资助项目(51569013)
甘肃省青年科技基金资助项目(145RJYA312)
关键词
液力透平
变工况
瞬态特性
内部流场
数值模拟
hydraulic turbine
variable working conditions
transient characteristics
internal flow field
numerical simulation
