含沙水流中空化促进磨损破坏机理

Mechanism of silt abrasion enhanced by cavitation in silt laden water flow

在对翼型试件进行空蚀、磨损及联合作用破坏研究的基础上,结合空化流场的测试及处理,研究含沙水流中水力机械过流表面空化行为促进磨损破坏的机理.对翼型表面不同位置空蚀、磨损及联合作用破坏微观形貌进行对比分析,得到了3种试验条件下微观形貌的破坏模式,确定了造成破坏模式的流场作用因素.对空化场图像进行了分析和处理,获得了翼型表面空化行为变化规律及特征.结合翼型表面破坏方式和空化场的分析,提出了在空化过程的空穴结构生长和空泡云溃灭两个阶段中,空化行为促进泥沙颗粒磨损破坏翼型试件的不同机理.在空穴结构生长阶段中,空穴结构推动颗粒加速;而在空泡云溃灭阶段,压力波或微射流则显著增大泥沙颗粒的运动速度.在两个阶段各自对颗粒速度的影响增大了联合作用的破坏能力.对翼型表面磨损及联合作用时破坏深度测量的试验结果验证了该观点.

On the basis of experimental study of cavitation erosion,silt abrasion and their synergetic erosion on hydrofoil,the mechanism of silt abrasion enhanced by cavitation in hydraulic machinery was analyzed combined with the testing and processing of cavitation structure in silt laden water flow.The erosion patterns were obtained by the contrastive analysis of microscopic appearance in different positions of the hydrofoil surface on three testing conditions and the flow factors which cause different erosion patterns were determined.The characteristics and law of behaviors of cavitation structure on hydrofoil were obtained by analysis and processing of cavitation structure images.The different mechanisms of silt abrasion enhanced by cavitation at the two stages of development of cavitation cavity and collapse of cavitation cloud are put forward by the analysis of erosion patterns and cavitation behaviors on hydrofoil.During the cavitation development stage,the silt particles are accelerated by cavitation cavity.During the cavitation cloud collapse stage,the silt particles are accelerated heavily by pressure wave or micro-jet.The synergetic erosion ability is strengthened by the actions on particles during the two stages.The viewpoints were verified by the experimental results of erosion depth of silt abrasion and their synergetic erosion on hydrofoil.