A Hydrodynamic Modei for Slug Frequency in Horizontal Gas-Liquid Two-Phase Flow

The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the modei was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30m long and its inner diameter is 24 mm. It is observed experimentally that the interfacial wave frequency at the inlet is about l to 3 times the frequency of stable slug. The slug frequencies predicted by the modei fit well with Tronconi (1990) modei and the experimental data. The combination of the hydrodynamic modei and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the miniraum frequency of interfacial wave.

Experimental Investigation of Slug Development on Horizontal Two-phase Flow

Slug initiation and subsequem evolution along a 5.0 cm ID, 16m long horizomal pipe are experimentally studied. The transient characteristics of interfacial structures are described by using simultaneous measuremeres of the liquid height at multiple locations along the pipe. Various effects of superficial gas and liquid velocities and pressure oscillation on the slug initiation and evolution along the pipe are illustrated. It is found that the slug is initiated by a deterministic orocess with reolenishmem and deoletion of liquid near the inlet for the superficial gas velocity USG〈3.0m·s^-1 and by a stochastic process with wave coalescence along the pipe for USG〉3.0m·s^-1.The evolution of the slugs is strongly attected by superhclal gas and liquid veloclties for USG〈3.0m·s^-1 but weakly affected by the superficial gas velocity for USG〉3.0 m·s . The suppression of pressure oscillation at the pipe inlet significantly delays the onset of slugging, with slugs forming postponed further downstream. The slug frequency at the outlet is, however, not affected by the variation in the pressure oscillation.

Characterizations of gas-liquid interface distribution and slug evolution in a vertical pipe

Large vertical pipes are key structures connecting subsea wells to offshore platforms.However,existing studies mainly focus on small vertical pipes.In a vertical acrylic pipe with 80 mm inner diameter and 11 m height,a high-speed camera was used to visually research the influences of pipe diameters,liquid properties and inlet effect on air-water co-flow characteristic.Different flow regime maps of vertical pipes(diameters are in the range of 50e189 mm)were compared and the critical gas velocity of the transition boundary from bubble to slug flow tended to increase with the increase of diameters at D≥80 mm.Drift-flux models were established in different flow regimes and liquid properties have a significant effect on drift coefficients of bubble flow and slug flow(void fraction a≤0.4).The influence of inlet turbulent effect on the gas-liquid interface distribution gradually weakened and disappeared from the pipe base to 85D,where the flow was fully developed.Slug frequency has a trend of increase first and then decrease with the gas Weber numbers increasing at low liquid superficial velocities(J_(L)≤0.31 m/s).And on the basis of this law,a new slug frequency correlation was proposed.It was found that there was an exponential relationship between the ratio of lengths of Taylor bubble to slug and the void fraction.

Numerical study on two-phase flow in horizontal pipe

Two-phase flow in a horizontal pipe was investigated by using numerical and experimental visualization methods.A horizontal pipe was built for qualitative and quantitative flow visualization.The length of horizontal pipe flow system was 9.5 m and the inner diameter was 51 mm.High-speed video method was used for the qualitative visualization and PIV method was applied for the quantitative visua-lization.The same geometry model was used for the numerical study.Three flow regimes including stratified flow,elongated bubble and slug flow field were generated and visualized by using numerical and experimental methods.The results show that the numerical simulation results are qualitatively si-milar to that of the experimental results.In addition,more quantitative results can be analyzed by numerical method.Development and decay process of slug flow was investigated,showing that the decay of slug heavily depends on the magnitude of nose velocity and its lasting time.It can also be found that the liquid superficial velocity plays a significant role in affecting the slug frequency.When keeping the gas superficial velocity constant,the frequency will increase with the liquid superficial velocity.