| With the rapid economic development,haze phenomenon becomes more and more serious all over the world.Haze of PM2.5 and PM10 particles has serious harmfulness to human body,so it is necessary to detect the concentration of PM2.5 and PM10 particles in the air.On the basis of quartz crystal micro balances principle and dielectrophoresis principle,PM2.5 and PM 10 concentration monitoring system was put forward for haze phenomena.In order to improve the accuracy of the system and implement the system detect PM2.5 and PM10 particles concentration detection respectively,the paper adopts the DPM discrete phase method and VOF volume of fluid method coupled way to complete the numerical simulation about micro-particle movement characteristics in the multiphase flow system.To facilitate the description of micro-particle movement characteristics,the paper call the position where particles move the closest to the pool bottom "settlement" position of particles.About micro-particle trajectory simulation in solid-liquid two-phase flow model,the paper study the influence of factors on the micro particle trajectories respectively like the liquid viscosity,the liquid density and inlet velocity,it was found that when the liquid viscosity reduce from 0.01Pa·s to 1×10-4Pa·s,the "settlement" position of particles will decrease with the decrease of the liquid viscosity,but if the liquid viscosity continue to reduce from 1×10-4Pa·s to 1×10-6Pa·s,the "settlement" position of particles will rise slightly with the decrease of the liquid viscosity.When the liquid density increases from 500kg/m3 to 2500kg/m3,the "settlement" position of particles will decrease slightly with the decrease of the liquid density.When the inlet velocity rise from 0.2 m/s to 10 m/s,the trajectories of different diameter particles separation degree increasing and the "settlement" position of particles will rise slightly.On the basis of solid-liquid two-phase flow,the paper used the VOF + DPM coupled model to study the impact of the inlet velocity,the liquid viscosity,the liquid density and the gas-liquid two phase surface tension,the micro-particle trajectory in gas-liquid-solid three-phase flow,it was found that with the increase of the inlet velocity,the trajectories of different diameter particles separation degree increase.As the inlet velocity increasing,the "settlement" position of PM 2.5 rising.As for PM10,when the speed rise from 0.2 m/s to 1 m/s,the "settlement" position decline,but if the speed continue to increase,the "settlement" position will begin to rise.When the liquid viscosity reduce from 0.01Pa s to 1×10-6Pa·s,the "settlement" position of particles will decrease with the decrease of the liquid viscosity.When the liquid density increases from 500kg/m3 to 2500kg/m3,the "settlement" position of particles will decrease slightly after rising some time,and if the liquid density is 1500kg/m3,the "settlement" position of the particles is the lowest.At the same time,the change of the surface tension movement regularity will have effects on micro-particles movement regularity,when the surface tension is 0.065N/m,the micro-particles'"settlement" position is the lowest.So in order to improve the accuracy of the system and implement the system detect PM2.5 and PM10 particles concentration detection respectively,setting the inlet velocity as around 1 m/s is most appropriate,and it can use some kinds of macromolecule drag reducer to make the liquid viscosity be adjusted to 1×10-5Pa·s,make the liquid density to be 1500kg/m3 and the surface tension to be 0.065N/m. |
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