空化射流形成的判据和冲蚀机理

CRITERION AND EROSION MECHANISM OF CAVITATING JET

阐述了空化射流研究简况和空化形成机理。讨论了用于描述空化是否发生和空化程度的空化数的合理性,认为用空化数不能判断射流的空化状态;流场中具有绝对压强小于或等于汽化压强的区域是射流空化的必要条件;在高环境压强下,必须采取特殊的减压措施才有可能实现空化。针对空化射流比普通射流冲蚀能力强的事实,分析了Rayleigh空穴湮灭冲击压强计算公式存在的问题,给出了空化射流的射流质量脉动引发作用在靶体表面上的压强脉动是导致靶体容易破坏的主要原因。

Mechanism of cavitation is introduced. Rationality of cavitating number which is used to judge cavitation and describe cavitating degree of jet is discussed, and it is found that cavitating condition cannot be obtained from cavitating number. The prerequisite for cavitation is that there exists an area in which absolute pressure is lower than or equal to vaporization pressure. To cavitate jet in high pressure environment, special decompression measure must be undertaken. Problems of Rayleigh equations for calculating impulsion pressure under annihilation of cavity to explain the fact that cavitating jet is of greater power to break target object than common jet are analyzed. A new explanation is given that target surface pressure pulse from density changes of cavitating jet which contain cavity is the main factor for breaking target more effectively.