Study of Relationship between Cavitation Light Emission and Erosion in an Orifice Flows

研究了孔板空化流的光发射与空化侵蚀的关系。在空化流中可以发现非常微弱的光发射。为了实现流场光发射模式的可视化，采用了改进了阿贝尔变换的CT技术。通过改变上游压力和节流孔直径的条件，系统地进行了实验。得到了空化发射强度的经验公式。采用一种新型实验系统，通过孔孔将铜棒置于管轴上，测量了空化侵蚀的破坏速率。发现空化损伤位置与发光位置有轻微偏差。最大空化损伤率与最大发射强度密切相关。为了在更复杂的流动中验证上述结果，本文还对圆孔周围产生的空化现象进行了类似的研究。圆孔内的光发射容易发生空化，但受流型和气泡分布的影响。为此，提出了一种独特的水锤实验方法。该装置可产生约100 atm的高压水锤，气泡瞬间被压力压缩。然后，一个相当强的光发射发生在一个管。阐明了光发射随水锤冲击面精确推进的规律。该结果有望用于管道系统中水柱分离的检测。对单个气泡的行为进行了理论计算，以估计发射强度。利用平衡辐射理论，考虑原子的电离和复合，建立了辐射强度的理论预测。计算结果表明，光发射不仅受热导率的影响，还受电离能的影响。少

A relationship between the light emission of an orifice cavitation flow and the caviation erosion is investigated. A very weak light emission can be found in the cavitation flow. For the visualization of the light emission pattern in the flow, CT technique in which Abel transformation is modified is applied. The experiment is systematically performed by changing the conditions of the upstream pressures and orifice diameters. Empirical formula for the cavitation emission intensity is obtained. The damage rate of the cavitation erosion is also measured by a new experiment system, where a copper rod is placed on the axis of the tube through an orifice hole. It is found that the position of cavitation damage slightly deviates from the position of light emission. But the maximum cavitation damage rate strongly relates to the maximum emission intensity. In order to verify the above results in the more complex flow, a similar research is also advanced for the cavitation generated around the c … More ylindrical column on the flat plateThe light emission in the orifice cavitation occurs easily, but it is influenced by the flow pattern and bubble distributions. Hence, a unique experimental method using a water hammer is proposed. The device can generate very high pressure of a water hammer of about 100 atm, The bubbles are instantaneously compressed by the pressure. Then a fairly strong light emission occurs in a tube. It is clarified that the light emission accurately progresses with the shock front of the water hammer. This result is expected to be utilized for the detection of a water column separation in a piping system. Theoretical calculation of a single bubble behavior is performed for the estimation of emission intensity. A theoretical prediction of emission intensity is constructed by using the equilibrium radiation theory considering the ionization and recombination of the atom. Calculation result shows that the light emission is strongly effected not only by the thermal conductivity but also by the ionization energy. Less