Experimental And Numerical Simulation Study Of Droplet Coalescence In Gas-liquid Flow In Pressure Pipeline

Demand for the development and utilization of marine resources is increasing,and offshore platforms are developing rapidly.Pressure-air is the source of control and driving power for various major equipment,and the stability of its pipeline system is particularly important.Most of the high-pressure air from offshore platform equipment enters the compressed gas pipeline system through an air compressor,but the marine atmosphere has the characteristics of high humidity and high salt,and salt-containing liquid droplets in the air will cause damage to the gas pipeline.In order to protect the key pneumatic equipment,the cleanliness of the gas in such high-pressure pipeline system must be paid attention to.At present,most scholars have studied the droplet coalescence phenomenon under atmospheric pressure.In this thesis,the droplet coalescence phenomenon in gas-liquid flow of pressure pipeline was studied by numerical simulation and verified by experiments.Firstly,based on the theory of force and coalescence of particles in the flow field,this thesis simplifies the particle group balance model and establishes the mathematical equations for the numerical simulation of droplet coalescence.Based on the simplified force in the air flow field,the theory of droplet coalescence is analyzed and discussed,combined with the population balance modeling（PBM）,established the droplet aggregation kernel function equation used in the numerical simulation.Secondly,the FLUENT software is used in this thesis to conduct numerical modeling for the droplet coalescence of gas-liquid flow in the pressure pipeline.An experimental platform for the droplet coalescence of gas-liquid flow in the pressure pipeline is built.The droplet size distribution is used as an indicator to verify the numerical model.By discussing the theoretical mathematical model,using the Two-Fluid model and PBM,to calculate.The CFD models of three typical pipelines in the gas pressure pipeline system is constructed.According to the conditions and the numerical simulation models,the boundary conditions are set.Then this thesis uses the gas-liquid flow droplet coalescence and monitoring experimental platform in the pressure pipeline to verify the numerical simulation models of the droplet coalescence.Firstly,this thesis studies the particle size measurement methods,and at the same time,according to industry actual situation designed the bench.Then,this thesis selects experimental instrument according to the experiment method and testing principles,and builds an experiment platform.The droplet coalescence experiment is carried out,and the model of the numerical simulation is compared and verified,and the experimental results are roughly consistent with the numerical simulation results.Finally,by using the validated models,the droplet coalescence in three typical pipes under different droplet mass concentrations and different pressures is calculated.The results show that the droplet coalescence increases with the increase of droplet mass concentration and pressure,and the pipe corner structure has an enhanced effect on droplet coalescence.This thesis provides theoretical and experimental basis for air purification and anticorrosion treatment of pressure-air pipelines on offshore platforms.It is very important for the gas pipelines design.