Study On Ultrahigh Pressure Supercritical Impinging Stream Technology

Ultrahigh impinging stream is a technology widely used in material crush.At present,the main problem is that when the pressure in the impinging stream is higher than a certain value,the diffusion rate and viscosity of the liquid are reduced and the impinging energy is reduced,which will have bad effects on material crush.In this paper,supercritical CO₂ fluid is introduced as a carrier to improve crushing effect.A new method,which combines ultrahigh pressure impinging stream technology,microsize pipe flow technology and supercritical fluid technology,is proposed to prepare micronano liquid particles.In this paper,the mechanism of the micro jet device is studied.First,the mechanism of droplet breakage is theoretically studied.The effect of the thickness of the boundary layer on the droplet fragmentation is analyzed.The effect of the impinging energy on the droplet breaking and refining is analyzed,and the collision Weber number is used to judge the state of the droplet after the collision.It is found that the impinging velocity and the pressure of the droplet are the key factors affecting the droplet crush,and the connection between the impinging velocity and the impinging energy,the impinging energy and the droplet crush degree is established.Secondly,the thermodynamic properties of supercritical CO₂ fluid are studied,and the influence of temperature and pressure changes on the density,viscosity and specific heat capacity of the supercritical CO₂ fluid and the impact on the impinging are studied.It is found that there is a competitive relationship between temperature and pressure.Under ultrahigh pressure,the influence of pressure on supercritical CO₂ fluid is dominant.Then,the influence of the size change of micro jet device on impinging velocity,turbulence intensity and impinging kinetic energy is studied through simulation.By comparing and analyzing the simulation results,the size of the device suitable for the impinging stream is found.The impinging distance is 2mm and the nozzle diameter is 0.2mm.Finally,the experiments were carried out through water oil emulsification and carotene oil based comminution experiment.The experimental results show that the refinement of liquid materials reaches the micro nano scale.It is verified that the addition of supercritical CO2fluid can help improve the kinetic energy of impinging and the simulation results are reliable.