EXPERIMENTAL STUDY ON TRANSIENTS CHARACTERISTICS OF GAS FLOW RATE IN GAS-LIQUID PIPELINES

The transient behaviors of gas flow initiated by quick change of gas flow rate were tested on a big multiphase flow loop. The results demonstrate that the sudden change of gas flow rate leads to downstream propagation of pressure wave at a speed varying with flow pattern. For various flow patterns, the pressure evolution has the same tendency. However, the transient mechanism of pressure for different flow patterns is various. The transient process of pressure in stratified flow relies on the inertia and compressibility of gas, and that in slug flow relies on the compressibility of gas in liquid film zone and the inertia of liquid slug. In addition, there will appear certain temporary flow patterns different from the flow patterns of quasi-steady change. In up-gas transient state, unsteady slugs were found even though the initial and final states are in stratified flow. In the transient process of slug flow, intensified slugging with high frequency was found. When gas flow rate quickly decreases, there will appear a short period of stratified flow in the transient process of the slug flow.