气瓶内部淬火过程的流动换热特性

 大直径厚壁气瓶内部淬火时的流动换热过程极其复杂，受到多种因素的影响，而研究气瓶内部压强和温度的变化规律对改善流动换热效果、提高产品组织性能具有重要的理论指导意义。以914 mm厚壁气瓶和瓶内流体为研究对象，建立了二维等效流 固耦合模型；采用多喷嘴系统对气瓶内外进行喷水淬火，研究了气瓶总长、喷水流速及淬火时间对瓶内压强及内壁温度的影响，通过间歇淬火试验验证了数学模型的正确性。结果发现，气瓶长度对瓶内压强和瓶壁温度的影响显著，喷水流速次之，当喷水流速大于8 m/s后，水量对瓶壁的冷却效果大大降低；气瓶内壁长度方向的温度梯度分别随气瓶总长的增加和淬火时间的延长而减小，但基本不受喷水量的影响。

Flow and heat transfer characteristics inside gas cylinder #br# during quenching process

The flow and heat transfer process of large diameter thick walled cylinders during internal quenching are extremely complicated，which is affected by many factors. And it is of great theoretical significance to study the variation law of internal pressure and temperature of gas cylinders for improving the flow and heat transfer effect and improving the microstructure and performance of the product. The thick walled gas cylinder with a diameter 914 mm and its internal fluid were taken as the research object，and a two dimensional equivalent fluid solid coupling model was established. The multi nozzle system was used to spray water quenching on the inner and outer wall surfaces of the cylinder. The effects of the cylinder length，water spray velocity and quenching time on the pressure inside the cylinder and temperature on the inner wall were studied. The correctness of the mathematical model was verified by intermittent quenching test. The results show that，the influence of cylinder lengths on the pressure and temperature is significant，followed by the spray velocity. When the spray velocity is greater than 8 m/s，the cooling effect of spray volume on the inner wall is greatly reduced. The temperature gradient on the inner wall along the length direction of the cylinder decreases with the increasing of the total length of the cylinder and the extension of quenching time，respectively，but basically not affected by the amount of water spraying.