【摘要】 空化射流在地面低环境压力下已经获得了广泛的应用,但是在地下高环境压力下的应用却遇到了一定的困难。为此,阐述了空化现象和空化射流研究简史、空化形成的机理、检验空化生成的方法和影响空化的因素;讨论了传统上用于判断射流是否空化及空化程度的空化数的合理性,结果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。针对空化射流比普通射流破岩能力强的问题,分析了Rayleigh空穴湮灭冲击压强计算公式存在的问题,给出了空化射流中的流体质量脉动引发作用在岩石表面上的压强脉动是导致岩石破坏的主要原因的理论解释。应用自振射流喷嘴能提高油气井钻进速度的原因不是射流空化,而是脉动的射流在岩石表面产生的脉动压力。在分析深井钻井的高温、高围压等特殊环境和空化形成机理后,认为空化射流应用于深井钻井很难。更多还原

【Abstract】 Research history of cavitating jet, mechanism of cavitation, methods for inspecting cavitation and factors affecting cavitation are introduced. The judgment of jet cavitation, and the rationality of cavitating number which is used to describe cavitating jet are discussed. It is found that cavitating status cannot be judged from cavitating number. Problems of Rayleigh equation for calculating impact pressure under annihilation of cavity are analyzed. And it is found that cavitating jet is of greater power to break rock than common jet, the pulsate pressures exerted on rock surface resulting from density changes of cavitating jet can break rocks more effectively. Based upon analyzing the high temperature and high ambient pressure environment at well bottom of deep wells and the mechanism of cavitation, it is recognized that it is difficult to apply cavitating jet in deep well drilling.更多还原