Experimental And Numerical Simulation Research On Two-phase Flow Characteristics Of An Internal-mixing Air-assisted Atomizer

Although the traditional pressure nozzle has a simple structure and is easy to process,it needs a higher pressure to have a good atomization,so the requirements for the equipment are relatively high.With the development of science and technology,internal mixing air atomizing nozzles have been widely used in various fields because of their high atomization quality,high viscosity liquids,and resistance to clogging.The principle of internal mixing air atomization is that the two phases of gas and liquid interact inside the nozzle and then break and atomize outside the nozzle.Therefore,the flow pattern inside the nozzle has a very important influence on the atomization effect of the external liquid.In this paper,the internal flow characteristics of the internal mixing air atomizing nozzle are studied by the methods of experiment and numerical simulation.The test uses water and air as the medium,and changes the nozzle operating conditions by adjusting the liquid flow rate and the air-liquid mass flow ratio(ALR),so as to study the internal flow characteristics of the nozzle.By observing the inside of the nozzle,it is found that most of the liquid is directly ejected from the nozzle hole,a small part is cut from the liquid column by the gas,and some of this part of the liquid adheres to the inner wall of the mixing chamber,and some exists on the inner wall of the mixing chamber.And the liquid column.By studying the inside of the nozzle,it is found that under the same liquid flow rate,when the ALR changes from small to large,the volatility of the liquid column in the mixing chamber becomes smaller and smaller,and the turbulence of the liquid film on the wall becomes smaller and smaller.Under the same ALR,when the liquid flow rate is small,the gas in the mixing chamber plays a leading role,and when the liquid flow rate is large,the liquid has a greater influence on the stability of the mixing chamber.Numerical simulation selected the VOF multiphase flow model and the SST k-ωturbulence model for simulation research,which were studied from the three aspects of the nozzle internal cloud image,central axis and different cross sections.Through the study of the cloud diagram inside the nozzle,it is found that the liquid flow rate remains unchanged.With the increase of ALR,the outflow area of the liquid in the nozzle hole is continuously reduced,and the pressure,velocity,turbulent kinetic energy and turbulent viscosity gradient range inside the nozzle increase.The ALR remains unchanged.The larger the liquid flow rate,the larger the outlet area,pressure gradient range and turbulent viscosity of the outlet section of the liquid in the nozzle hole.Through research on the center axis of the nozzle,it is found that the liquid flow is constant,and the greater the ALR,the greater the pressure and velocity on the axis.The ALR remains unchanged,the greater the velocity on the axis in the mixing chamber;the greater the liquid flow rate in the nozzle hole,the greater the velocity on the axis under small ALR,the greater the velocity on the axis under large ALR,the greater the velocity on the axis Small;the greater the liquid flow,the greater the pressure on the axis.Through the study of each section of the nozzle,it is found that the liquid flow rate remains unchanged.As the ALR increases,the pressure,gas volume fraction,pressure,velocity and turbulent kinetic energy on the section increase.The ALR is unchanged,the larger the liquid flow rate,the larger the gas volume fraction,pressure and turbulent viscosity on the interface.At the outlet of the nozzle,the pressure reaches a minimum,but it does not become atmospheric pressure,but slightly higher than atmospheric pressure.In addition,the gas flow rate is the main factor affecting the velocity and turbulent kinetic energy inside the nozzle.