基于气泡动力学的液压气穴发光机理及气穴噪声研究

When the partial pressure of the hydraulic oil is lower than the saturated vapor pressure, gas nuclei grows into steam bubble existing in the liquid, and expands until bubble collapse, forms cavitation. Occurrence of cavitation accompanied by strong thermal imbalance, especially in the steam bubble collapse, due to strong thermal imbalance, the instantaneous high temperature and high pressure occurs at the center of the steam bubble, which produces complex cavitation luminescence and cavitation noise. According to the phenomenon of cavitation luminescence in hydraulic system, and multidisciplinary interdisciplinary theory based on bubble dynamics, thermodynamics, optics and hydrodynamics, this project carries out research on the formation mechanism and key influencing factors of the hydraulic cavitation luminescence. The dynamic modeling of bubble dynamics based on the Rayleigh-Plesset equation and the analysis of the mechanism of cavitation luminescence based on optics and hydrodynamics are emphatically studied in this project. A bubble dynamic equation that can correctly describe the bubble movement under the condition of hydraulic cavitation luminescence and thermodynamic mathematical model of cavitation luminescence are obtained in this project. At the same time, this project studies on the change of bubble shape under the condition of cavitation luminescence. Changing the law of bubble shape under the condition of cavitation luminescence is obtained in this project. Based on the research of bubble shape, this project studies the cavitation noise under the condition of cavitation and luminescence, and gets the relationship between cavitation noise, cavitation luminescence intensity and cavitation intensity.

当液压油的局部压力低于其饱和蒸汽压时，液体中存在的气核会生长成蒸汽泡，并膨胀直至溃灭，形成气穴现象。气穴的产生过程伴随着强烈的热力不平衡性，特别是在蒸汽泡溃灭时，由于热力的强烈不平衡，使得蒸汽泡的中心出现瞬时的高温高压，产生复杂的气穴发光以及气穴噪声等现象。针对液压系统气穴发光现象，基于气泡动力学、热力学、光学、流体力学等多学科交叉理论，开展液压气穴发光形成机理及关键影响因素的研究，重点开展基于Rayleigh-Plesset方程的气泡动力学建模以及基于光学、流体力学的气穴发光机理分析等研究，得到能够正确描述液压气穴发光条件下气泡运动的气泡动力学方程和气穴发光的热力学数学模型。同时展开在气穴发光条件下气泡形态变化规律研究，得到气穴发光条件下气泡形态变化规律，并以气泡形态研究为基础研究气穴发光条件下的气穴噪声问题，得到气穴噪声与气穴发光强度以及气穴强度之间的关系。

由于结构的原因，液压系统不可避免会产生气穴现象，其是液压系统典型缺陷，会对液压元件造成诸多不利影响，因此开展液压气穴研究工作十分必要。目前对于液压气穴发光问题的研究还鲜有公开研究成果，本课题围绕气穴产生的影响进行研究，重点进行液压气穴发光问题产生及发展规律研究、液压气穴形态变化规律研究、液压气穴噪声问题研究以及气穴对典型阀类元件影响研究。本课题结合已有研究成果对气穴气泡动力学方程进行了推导，引入特征系数获得了改进的温度效应影响下的气穴气泡动力学方程；采用有限体积法对锥型节流阀和双喷嘴挡板压力伺服阀前置级气穴进行了仿真研究，从理论上获得了两类阀内部流场气穴分布情况，并搭建了实验台对仿真结果进行了验证；采用可视化实验方法观察了气穴的发展变化过程，并测量了气穴噪声，获得了气穴噪声影响因素。本课题的研究成果可为液压气穴机理研究提供理论和数据支撑。