垂直管道内油-水两相环状流的流动特征

Investigation on the performance of oil-water two-phase core annular flow in vertical pipes

该文通过实验研究了垂直上升和垂直下降管道内油水两相混合液的流动特征。实验段管道的内径为25 mm,垂直段长度为1500 mm。为了得到油水两相环状流流型,分别在垂直管道的入口和出口处安装有收缩和扩张管道。实验中的油相为白油(97 mPa·s,860 kg/m3),水为普通生活用水(1 mPa·s,998 kg/m3),含油率范围为0–100%,混合速度为0.28 m/s–4.65 m/s。研究中,分别采用压力传感器、高速摄像机和快关阀对管道中两相流动的压降、流型和含油率等特征进行了测量和记录,并采用两流体理论模型对流动中的摩擦压降进行预测。研究结果显示:流动中形成的水包裹油的广义环状流型,可以很好的降低摩擦压降,并可以将摩擦压降分为壁面摩擦和界面摩擦两部分,采用两流体理论对压降梯度进行预测,误差小于20%;由于油水两相间的密度差和截面相分布特征,使两相之间存在速度滑移,可以看出垂直上升和下降管道内的油相的相速度值均高于水相,在含油率为60%–80%时其差值达到最大。

The performance of oil-water two-phase flow in downward and upward vertical pipes is investigated by experiment. In the present study, a U-tube with the 25 mm inner diameter, 1 500 mm vertical length and two reductions from 50 mm inner diameter to 25 mm inner diameter are designed to obtain the generalized annular flow regime. And, the white oil is used as the oil phase （97 mPa-s, 860 kg/m3）, the oil volume fraction is from 0 to 100% and the mixture velocity is in the range of0.28 m/s-4.65 m/s. In the research, pressure sensors, high speed camera and the quick closing valve system are used to measure the pressure drop, flow regimes and in-situ oil volume fraction respectively. The frictional pressure drop in flow is predicted by two-fluid model. The results show that, the generalized annular flow can decrease the frictional pressure drop greatly, and the frictional pressure drop should be divided into wall friction and interfacial friction which can be predicted by two-fluid model in the accuracy of 20%. Also, the quantitative description of velocity-slip is given that the oil phase velocity in downward and upward vertical pipes is greater than water and the difference becomes greatest in the oil volume fraction of 60%-80%.