基于截面气含率的文丘里湿气压降模型

运用两相流理论对湿气中的气相与液相流动进行分析,在分层流与环雾状流的条件下推导了两相流通过水平标准文丘里流量计的理论模型.通过分别考虑截面气含率、相间摩擦以及液滴夹带等因素,在文丘里轴向对湿气流动中的气相动量方程进行求解.通过对水平直管中的截面气含率公式进行修正,建立了适用于收缩管道的截面气含率模型,并在此基础上模拟了湿气流经标准文丘里时其两个取压孔之间的轴向静压分布.实验证实,使用修正后的截面气含率公式将使模型对文丘里压降的预测准确度明显提升,其相对误差在15%以内.该模型以湿气两相流在水平文丘里中的流动形态为依据,具有较充分的物理背景,而且在推导过程中较少依赖特定实验装置与数据,为建立具有一定普适性的文丘里湿气计量模型奠定了基础.

Modeling of wet-gas flow through horizontal Venturi based on void fraction

In this study, by using the two-phase hydrokinetic theory, a theoretical model for gas-liquid annular and stratified flows through a horizontal Venturi meter was developed. The momentum equation for the gas phase was solved in the axial direction, by considering the factors including void fraction, friction between two phases and entrainment of droplets in the gas core. By modifying the void fraction model proposed by Lockhart and Martinelli, a void fraction model for the convergent tube was developed. Using the modified void fraction model, the distribution of wet gas static pressure between two pressure tappings of the venture meter was simulated. For the sake of checking the validity of this model, wet gas flow experiments were performed by using the standard venture meters with diameter ratio of 0.55 and 0.4 in the flow laboratory of Tianjin University. The predicted points of the modified model were within error band of ±15%. As the model was developed more based on dynamics characteristics of wet gas flow, it could form the basis for further establishing a general flow measurement model of wet gas.