高压氢燃料气瓶加压惰化排气陡降机制

Mechanism of sharp drop in pressurized inert exhaust from high-pressure hydrogen fuel cylinders

为了提高惰化效率并确保高压氢燃料气瓶的安全应用,采用数值模拟方法评估加压惰化过程中的氧气体积分数变化特征。在加压注气过程中最大氧气体积分数位于氢燃料气瓶的底部区域,而在排气过程开始阶段发现最大氧气体积分数的陡降现象,设计不同的模拟方案分析陡降现象的原因。结果表明:速度-压力耦合效应是排气过程开始阶段氧气体积分数陡降的根本原因,其中瓶内速度场的影响占主导地位,速度场的影响在未静置和静置方案中分别为91.4%和86.7%,而压力场的影响仅为8.6%和13.3%;排气反向冲量及排气低压向瓶内传递诱导流场,叠加加注形成流场共同促使气瓶底部区域内的流动再循环,使得瓶底区域的流动速度增加且速度场与氧气体积分数场协同效应加强,强化了对流传质形成陡降现象。

To improve the inerting efficiency and ensure the safe application of high-pressure hydrogen fuel cylinders,numerical simulations were applied to evaluate the oxygen volume fraction variation characteristic of the pressurized inerting process.The maximum oxygen volume fraction was located at the bottom zone of the cylinder during the charging process.A sharp drop phenomenon of maximum oxygen volume fraction at the beginning stage of the exhaust process was detected,and different simulation strategies were designed to analyze the reason of the phenomenon.The results show that,the velocity-pressure coupling effect has a particularly substantial influence on the sharp drop of oxygen volume fraction at the beginning stage of the exhaust process,and the effect of the velocity distribution of the charging process is predominant.The effect of velocity on the oxygen volume fraction is 91.4%for the non-static option,and it is 86.7%for the static option.The effect of pressure on the oxygen volume fraction is 8.6%for the non-static option,and it is 13.3%for the static option.The reverse impulse of exhaust gas,the flow field induced by transmission in the exhaust low-pressure bottle,and the flow field formed by superposition filling jointly promote the flow recirculation in the bottom zone of the bottle,which increases the flow velocity in the bottom zone of the bottle and strengthens the synergistic effect between the velocity field and the oxygen volume fraction field,thus strengthening the phenomenon of sharp drop of convective mass transfer.