煤直接液化减压进料阀组数值模拟与优化

Numerical simulation and optimization on coal liquefaction hypobaric charge-in valve

以煤液化减压塔进料前的角阀、球阀及相联管道(简称"减压进料阀组")的冲蚀磨损失效为研究对象,采用RNG k-ε湍流模型、蒸发-凝结模型、随机轨道模型,结合高温冲蚀磨损实验修正建立的冲蚀磨损模型,数值计算分析了角阀典型开度下流速、相分率和壁面磨损率等参数的分布规律,并结合实际损伤形貌验证了冲蚀磨损数值方法的正确性。研究结果表明:角阀流道为缩放结构,阀芯头部流速增加,压力降低,发生汽-液转换形成局部空化;空化引起阀组流道内有效传输面积减小,流体介质速度提高,对固相颗粒的拖曳加速效应显著,高速的颗粒碰撞壁面是造成球阀端面及出口管道冲蚀磨损的主要原因。基于等磨损速率对比分析角阀不同入口角度与球阀位置的对应关系,提出优化方法。

Angle valve, ball valve and connecting pipe (called as “hypobaric charge-in valve group”) in the front of coal liquefaction hypobaric tower were investigated in this study. RNGk-Εturbulent model, evaporation-condensation model, stochastic trajectory model and erosion model, which was corrected by high temperature erosion-wear experiment, were used to calculate the distribution of velocity, phase fraction and erosion rate in the typical opening of angle valve; then the accuracy of numerical calculation was proved by actual damage morphology. The study shows that: the angle valve port, which is a reducing structure, leads to the increase of velocity in valve core, the decrease of pressure, and the transition of liquid-vapor; the velocity of particle was accelerated by the increase of flow velocity on valve core head, the decrease of pressure, the high rate of gasification; the cavitation causes the decrease of effective transmission area of valve group, the increase of flow velocity, then the towing speed of solid increased significantly, so high-speed solid which impacts wall is the main reason for erosion wear. The relationship between the different inlet angles of angle valve and the position of ball valve was compared and analyzed to determine the optimization method of reducing wall erosion rate. © 2015, China Coal Society. All right reserved.