Severe Slugging Elimination Technology Based On PID Automatic Control Of Throttle Valve

In the process of gas-liquid mixed transportation,there are complicated flow states in the mixed pipeline due to the interference of interface effect and two-phase turbulence.Due to the fluctuation of submarine topography,the flow type —severe slugging will often occur,which will seriously threaten the normal operation of the mixed pipeline and the corresponding equipment downstream of the pipeline.The characteristics of severe slugging and the PID automatic control of throttle valve are studied by using simulation software and indoor multiphase flow experimental system.In the indoor experiment of severe slugging characteristics,the pressure fluctuation,cycle period and eruption time changes of severe slugging were deeply analyzed.The results found that the maximum pressure with the increase of the converted gas velocity and show the trend of stability after decline,with the increase of the converted liquid velocity and show the increase of the stable trend;The fluctuation amplitude of the pressure of the typical severe slugging increases with the rise of the gas velocity,and decreases with the rise of the liquid velocity;The fluctuation amplitude of pressure of the transition flow decreases with the rise of gas velocity and increases with the rise of the liquid velocity.The cycle period of the severe slugging will decrease as the converted gas and liquid velocity increase.The gas-liquid ejection time of severe slugging-T* decreases with the increase of converted gas velocity,but the converted liquid velocity has little effect on gas-liquid ejection time-T*.During the study of PID automatic control of throttle valve,the results show that the method can control the fluctuation of pressure in the middle of vertical riser in the mixed pipeline system in the expected range,thus successfully inhibiting the severe slugging.Due to the influence of PID automatic control of throttle valve,the pressure in the middle of the riser and the period length and fluctuation range of the liquid holding rate at the bottom of the riser are obviously reduced.With the decrease of valve opening of throttle valve,the back pressure of mixed pipeline system increases,and the hydrostatic pressure in vertical riser to prevent liquid plug from moving upward becomes larger,which exacerbates the slip phenomenon between mixed fluid.The liquid phase quickly falls back to the bottom after reaching a certain riser height,and the gas phase penetrates the slug and flows downstream at low speed.The control method is related to the relative and absolute velocity of converted gas and liquid phase,and is sensitive to liquid phase velocity.Finally,we verify that it still plays an important role in guidance and correction in the feasibility research and engineering practice design of oil and gas equipment and pipeline.It can help the researcher greatly shorten the research time,and improve the research efficiency of pure experiment.