不同旋流器作用下气液螺旋环状流动特性研究

Study on characteristics of gas-liquid spiral annular flow under action by different swirlers

管内气液螺旋环状流动可以通过设置固定叶片的旋流器形成,旋流器的结构极大地影响了形成的螺旋环状流动的稳定性。对此,选取了四种典型旋流器结构开展三个典型来流工况下螺旋环状流形成的实验研究。通过图像处理结合概率密度函数(probability density function,PDF)拟合的方法分析了形成螺旋环状流的稳定性,同时结合液膜波动特性与旋流器内部作用过程分析发现:平板式及平板有中心柱式旋流器在不同来流工况下产生的液膜相较于螺旋叶片式A/B旋流器都更加稳定,相同工况下的失稳距离也更长,而螺旋叶片式A/B旋流器产生的螺旋环状流的稳定性较差,在更短的距离内即发生了螺旋环状流失稳现象;不同工况下液相折算速度的上升有助于提高液膜稳定性与螺旋环状流失稳距离,从而形成更稳定的螺旋环状流;叶片作用下流体内部压力梯度和气液相分布规律高度相关,压力梯度和周向速度是形成螺旋环状流动的主要因素,并且压力梯度和周向速度的大小一定程度决定了螺旋环状流动气液交界面的稳定性。

The gas-liquid spiral annular flow in the tube can be formed by setting a cyclone with fixed blades.The structure of the cyclone greatly affects the stability of the spiral annular flow.To investigate this,four typical swirler structures were selected for experimental research under three typical inflow conditions.The stability of the formed spiral annular flow was analyzed by using image processing combined with the probability density function(PDF)fitting method.Additionally,the fluctuation characteristics of the liquid film and the internal action process of the swirler were analyzed.It was found that the liquid film generated by flat plate swirlers with central cylinder cyclone under different inflow conditions is more stable than that of the spiral blade A/B cyclone,and the instability distance under the same working conditions is also longer.However,the stability of the spiral annular flow generated by spiral vane type A/B swirlers is poorer,with instability occurring over a shorter distance.The increase in the equivalent liquid phase velocity under different conditions contributes to improving the stability of the liquid film and the instability distance of the spiral annular flow,thus forming a more stable spiral annular flow.The pressure gradient and the radial velocity within the fluid under the action of the vanes are highly correlated,where the pressure gradient and the radial velocity are the main factors in the formation of spiral annular flow,and their magnitudes determine to some extent the stability of the gas-liquid interface of the spiral annular flow.