Study On The Flow And Distribution Characteristics Of Liquid Film In The Helical Channel Of Single Screw Expander

Energy and environmental pressure will accompany the development of my country’s society and economy for a long time,and improving energy efficiency is an important technical guarantee for my country’s sustainable development.Choosing efficient energy utilization equipment and reasonable renewable energy utilization methods is an inevitable choice for optimizing energy structure and ensuring sustainable economic and social development.Single screw expander is a new type of expansion power equipment,which has the characteristics of both speed type and volume type expander,and has very good development potential.The working process of the single-screw expander is very complicated.The multiphase and multicomponent fluid composed of working fluid/lubricating oil interacts and affects each other in the complex three-dimensional flow channel.However,there is currently a lack of related basic research work.The distribution characteristics of the liquid film flow in the leakage gap of the helical channel of the expander are the key factors affecting the performance and efficiency of the expander.This paper proposes to study the flow characteristics of the liquid film in the helical channel of the single-screw expander,which provides the necessary research basis for finding effective ways to reduce the gap leakage of the expander and improve the operating efficiency of the expander.Firstly,a visualization experiment platform for the flow characteristics of the gas-liquid two-phase liquid film in the helical channel is built.Using a high-speed camera,the gas-liquid two-phase flow characteristics in a vertically placed helical channel are visualized,and the influence of different structural parameters and two-phase flow on the change of liquid film thickness at different angles in the helical channel is explored.Based on the helical channel structure of the screw in a single-screw expander,a numerical calculation model for the oil/gas two-phase flow process in the helical channel is established.The fluctuating characteristics of the two-phase liquid film flow in the helical channel are numerically simulated,and the distribution of the liquid phase,the thickness of the liquid film,and the liquid holdup in the helical channel are studied under different fluctuation amplitudes and frequencies of the gas phase at the inlet.Secondly,the visualization reveals the change law of the instantaneous liquid film thickness under different two-phase flow conditions,explores the distribution law of the instantaneous and average liquid film thickness at different angle positions,and theoretically analyzes the influence of the comprehensive force at different circumferential angle positions on the liquid film thickness.The mechanism of action of the distribution.The effect of dimensionless curvature and dimensionless pitch on the average and instantaneous liquid film thickness at different angles is given under different two-phase flow rates.The results show that when Re_l is the same,increasing Re_g will reduce the instantaneous liquid film thickness,and under the condition of smaller Re_g,the instantaneous liquid film thickness will increase significantly when increasing Re_l.Due to the entrance effect,the liquid film thickness is larger at the 90°angle position,but at the 180°and 270°angle positions,the liquid film thickness decreases,and the difference is obviously weakened.Increasing the dimensionless curvature and dimensionless pitch will decrease the average liquid film thickness and the instantaneous liquid film thickness.Finally,numerically analyzed the periodic characteristics of the velocity of different angular positions and liquid phase distribution of the helical channel under different inlet gas phase fluctuation conditions,and obtained the average and instantaneous changes of liquid film thickness and liquid content at different fluctuation conditions and angular positions law.The results show that under the same fluctuating conditions,the velocity time distribution in the helical channel exhibits periodic variation characteristics.Increasing the amplitude of gas phase fluctuations makes the thickness of the liquid film on the outer wall of the channel at different angles decrease.Increasing the frequency of gas phase velocity fluctuations helps to improve the distribution of liquid phases at both ends of different cross-sections,making the distribution of liquid phases more uniform along the radial direction of the helical channel.