气液两相流流量变化瞬态特性

在气液混输管线中常发生流量变化引发的瞬态过程，在大型多相流实验环道上进行了流量变化的瞬态实验.气量突增产生压力过增量，它的产生与流型有关：分层流的过增量是由于气体的惯性；在气团流和段塞流下则是由于气体压缩性和液体惯性的联合作用.气量突降时，膨胀波沿程传播.气量变化的瞬态过程可能出现对应准稳态变化没有出现的流型.与气量突变相比，液量突变引起的压力和流型变化较平缓，瞬态效应小.流量变化后产生沿线传播的压力波和空隙波，二者与流型相关，决定瞬态过程的发展.压力变化的传播速度在气量变化时等于声速，在液量变化时等于空隙波波速.

CHARACTERISTICS OF FLOW RATE TRANSIENTS IN GAS-LIQUID FLOW

Transient flow induced by the change of fluid flow rate occurs frequently in two-phase pipelines. Many transient experiments are conducted on the authors' big multiphase flow loop. Increasing gas flow rate causes pressure overshoots arising from gas inertia in stratified flow and from gas compressibility and liquid inertia in plug and slug flow. Decreasing the gas flow rate leads to pressure undershoot. In gas transients, flow patterns may appear which are not observed in corresponding quasi-steady state. By contrast, in liquid transients, pressures and flow pattern undergo smooth transitions and transient effects are small. In addition, the pressure waves and void fraction waves propagating downstream depend heavily on flow pattern and evolution of them determines the transient process. In gas transient flow, the speed of pressure change equals to sound velocity while in liquid transient flow it equals to the void fraction wave velocity.