管内螺旋导流板引发的气液两相旋流场

用数值模拟的方法研究某种螺旋导流板结构引发的管内气液两相旋流的流动特点。空气为主相，水为次相，入口为雾状流。研究旋转给流型转变、气液相分布、速度分布及旋流衰减带来的影响。发现雾状流在螺旋导流板的作用下，转变为环状流。螺旋导流板内有二次涡的生成，且二次涡结构不断发展变化，离心力分布不均匀而形成沿管壁周向不连续的液膜；流出螺旋导流板后，二次涡会衰减消失，流体做螺旋向前运动，液膜沿圆管周向逐渐分布均匀。管中心处气相切向速度小，气相切向速度较大的区域远离旋流中心区，旋流中心与圆管中心存在小的偏心距；与直管及螺旋纽带相比，螺旋导流板引发的气液两相旋流在圆管中心的气相轴向流速远高于光管和螺旋纽带；与螺旋纽带相比，螺旋导流板引发的旋流强度更大且衰减减慢。

Gas-liquid Swirling Flow Induced by Helical Tape with Core-rod inside Circular Pipe

To classify the flow features of gas-liquid flow induced by the helical tape, swirling flow of gas and liquid induced by a helical tape in a circular pipe is numerically simulated, air is the primary phase and water is the secondary phase, the flow pattern is mist flow. The effects of swirl on transition of flow pattern, distribution of gas and liquid phases, velocity field and swirl decay are investigated. The results show that mist flow is transformed to annular flow under the effect of helical tape. Secondary vortices appear in the helical tape region, these vortices develop and their structures change, the liquid film is not continuous along circumferential direction of the pipe due to non-uniform centrifugal force. Away from the helical tape, fluid flows helically without secondary vortices, droplets and liquid film distribution become uniform. Gas tangential velocity value is high away from the swirling center and low near the pipe center, there is an offset between swirling center and pipe center. Compared with twisted tape and smooth pipe, the extent of gas axial velocity enhancement near the pipe center induced by a helical tape is significantly larger than twisted tape which is larger than smooth pipe. Swirl number of the swirling flow induced by helical tape increases and decays slowly compared with twisted tape.