冲蚀与空蚀交互磨损三相流场仿真与试验研究

基于计算流体力学方法,数值研究在模拟水轮机工况下,冲蚀与空蚀交互作用时,试件表面上汽液固三相流场的动力学特性(压力场、速度场、汽相体积比分布),然后在转盘式磨损装置上,进行汽液固三相冲蚀与空蚀交互磨损试验,并对试件微观形貌进行分析。结果表明:数值分析得到试件表面最小和最大压力值、气泡速度最大值和汽相比例最大值均出现在空化孔附近,其他位置基本不变,说明空化孔附近交互磨损比单一空蚀磨损严重。就某一空化孔而言,顺着转盘旋转方向的孔边某一夹角展开区域汽相比例较大,并且出现最小和最大压力;从试件微观磨痕分析,其上存在短程犁沟和空蚀孔,磨痕呈现规律性。仿真的气泡轨迹和试件磨痕基本一致,数值计算结果和试验结果吻合得较好,从而证明了数值分析的正确性和合理性。上述数值仿真为揭示流体机械过流部件冲蚀与空蚀交互作用磨损机理奠定了基础。

Flow Field Simulation and Experimental Research on Interactive Erosion and Cavitation Wears in Three Phases

Based on the computational fluid dynamics method,simulating the working conditions of hydraulic turbine,the dynamic characteristics of the vapor,liquid and solid phase flow fields(pressure field,velocity field of air bubbles and volume fraction of vapor phase) on the specimen surface is numerically calculated under the interactive erosion and cavitation wears.On the rotating wearing experimental device,the interactive erosion and cavitation wear experiment of three phases is done,and the micro-morphology wear scars on the specimen surface is analyzed.The results show that minimal and maximal pressure values,maximal velocity of air bubbles and maximal volume fractions of vapor phase on the specimen surface all appear on the neighboring region of the cavitation hole by means of numerical analysis,and on the other regions they basically remain unchanged.It is indicated that interactive wears are more severe than single cavitation wears on the neighboring region of the cavitation hole.As far as a certain cavitation hole is concerned,the region of maximal volume fraction of vapor phase expands at a certain angle around the hole edge along rotational direction,and its pressure is minimal or maximal.Through the analysis of the micro-morphology wear scars on the specimen surface,there exist short-range ploughings and cavitation holes,and the wear scars are presented regularity.Simulative air-bubble tracks are in agreement with the wear scars,and the experimental results and theoretical results coincide better,which proves the theoretical analysis is reasonable.The above numerical simulation provides an important basis for revealing the interactive erosion and cavitation wear mechanism of fluid machinery transition parts.