输气管道气体置换混合长度变化规律研究

Study on the Length of Mixed Region during Purging of Gas Pipeline

分析了管内二元气体的混合机理,对不同流速影响混合长度规律的三维数值模拟进行了研究。结果表明,在置换初始阶段,混合长度增长速率加大,随着置换距离的增加,增长速率减小;混合区浓度在轴向上为非对称分布,呈"头短尾长"特征;流速是置换的重要控制参数,湍流时的混合长度小于层流,但是进入湍流状态后,提高流速对减少混合长度的作用逐渐减弱。

The mixing mechanism of dual-species gas in pipe is analyzed,and the effect of the purging velocity on the length of mixed region is numerically studied. The result indicates that the mixture length increases very fast in initial purging state and then changes slowly with the increasing of length of the pipe purged. The concentration in the mixed region appears asymmetric in distribution profile along axial direction, which has a characteristic of short head and long tail. Purging velocity is one of the key parameters during purging process. The length of mixed region is shorter during turbulent flow than that of laminar flow. Velocity increase has less effect on reducing the length of mixed region.