热氨融霜过程多相相变流动液击形成机理研究

热氨融霜多相流动液锤诱发的回气总管频现爆管和穿孔腐蚀事故的预防仍是一项技术挑战。基于进口速度突变和瞬态冷凝与汽化相变直接驱动力，建立了描述多相相变流动液击形成过程的理论模型及其数值模拟算法，研究了回气总管热氨蒸汽与深冷液氨多相分层流动液击的形成机理，研究结果表明:在进口流速突变条件下，瞬态冷凝与汽化相变多相流动诱发的液击压强是无相变多相流动液击压强4倍左右，考虑相变驱动是准确预测多相流动液击的理论前提，多相流动液锤压力显多波型大幅脉动波动变化，且随着氨液剩余填充量增加而增大，而深冷液氨区局部液击压力降至液氨的饱和蒸汽压所诱发的空泡溃灭是导致回气总管频现穿孔腐蚀的直接原因。

Study on formation mechanism of liquid hammer by multiphase phase change flow in the process of hot ammonia defrosting

The prevention of tube bursting and perforation corrosion accidents which have frequently occurred in gas return manifold induced by multiphase flow liquid hammer in hot ammonia defrosting process is still a technical challenge. Based on the direct driving forces of inlet velocity mutation, transient condensation and vaporization phase change, a theoretical model and numerical simulation algorithm describing the formatting process of liquid hammer by multiphase phase change flow were established, and the formatting mechanism of liquid hammer by multiphase stratified flow of heat ammonia steam and cryogenic liquid ammonia in the gas return manifold were studied by the numerical simulation. The results showed that the liquid hammer pressure induced by multiphase flow of transient condensation and vaporization phase change was four times more than that induced by multiphase flow without phase change under the condition of inlet velocity mutation. Considering the phase change driving was the theoretical premise of accurately predicting the liquid hammer by multiphase flow. The pressure of liquid hammer by multiphase flow presented multi-wave large amplitude pulsating fluctuating variation, and it increased with the increasing residual filling volume of ammonia liquid. The cavitation collapse caused by the reduction of local liquid hammer pressure at cryogenic liquid ammonia zone to the saturated vapor pressure of liquid ammonia was the direct reason of perforation corrosion frequently occurred in gas return manifold.