EXPERIMENTAL AND APPLICATIVE STUDIES ON CAVITATION BUBBLE DYNAMICS IN CRYOGENIC LIQUID HYDROGEN

对包括液氢在内的低温液体中空化汽泡的动力学进行了实验和分析研究。随着航天技术和液化天然气装置等低温工程的快速发展，研究低温流体中的空化现象变得十分必要。激光诱导的空化气泡已经被许多研究者研究过。通过应用激光诱导气泡的产生，气泡本身在时间和空间上都得到了精确的控制。这项技术不会对周围的液体造成任何大的干扰。在这项研究中，气泡是通过将调Q红宝石激光器的巨大脉冲聚焦到低温液体(液氮、氢气和Ar)中在低温恒温器中产生的。用高速摄影的方法研究了低温液体中激光诱导气泡的动力学，成帧速率高达1000000帧/S的IMACON-790型相机。用PCB型压电式…测量了冲击压力更多的电磁场换能器。对低温液体中气泡的物理行为进行了数值分析。该数学公式考虑了液体惯性、蒸汽的非平衡凝结以及气泡壁上的换热等因素的影响。将数值解与低温液体中单个气泡运动的实验结果进行了比较。主要结果如下：(1)为了在低温恒温器中产生高度球形的气泡，必须去除聚焦透镜的像差。利用虹膜对低温液体中的气泡行为进行了观察。(2)对液氮、氢气和氩气中的气泡动力学进行了数值模拟。在气泡壁上包含换热的情况下，气泡表现出剧烈的行为。蒸发系数和冷凝系数(非平衡参数)对气泡运动有很大影响。将数值计算结果与实验结果进行了比较。较少

The experimental and analytical investigations have been conducted on the dynamics of cavitation vapor bubbles in cryogenic liquids including liquid hydrogen. With the rapid progress of cryogenic engineerings such as aerospace technology and LNG plants, it becomes necessary to study cavitation phenomena in cryogenic fluids. Laser-induced cavitation bubbles have been investigated by many researchers. By applying the laser-induced bubble generation, the bubble itself is precisely controlled both temporally and spatially. This technique does not cause any large disturbances in the surrounding liquids.In this research, bubbles are produced by focusing a giant pulse of a Q-switched ruby laser into cryogenic liquid (liquid nitrogen, hydrogen, and Ar) in a cryostat. The dynamics of the laser-induced bubbles in cryogenic liquids were studied by means of high-speed photography using a Imacon-790 camera with framing rates of up to 100000frames/s. The impact pressure was measured by PCB piezoelec … More tric transducer. A numerical analysis was also developed for the physical behavior of the bubble in cryogenic liquids. The mathematical formulation takes into account the effects of liquid inertia, the none-equilibrium condensation of vapor, and the heat transfer at the bubble wall. The numerical solutions were compared to the experimental results on single bubble motion in cryogenic liquid. The main results are summarized as follows: (1) The aberration of the focusing lens must be removed, in order to produce a highly spherical bubble in the cryostat. An iris has been used, and the bubble behaviors in cryogenic liquids were observed. (2) Bubble dynamics in liquid nitrogen, hydrogen, and argon were simulated numerically. In the case of including heat transfer at the bubble wall, the bubble indicates a violent behavior. The bubble motion received a very strong influence by the coefficient for evaporation and condensation (non-equilibrium parameters). The numerical results were compared with experimental results. Less