Study On The Characteristics Of The Effect Of Air Disturbance On Particles Flow In A Finite Space

In the pharmaceutical field,the powder needs to be sterilized by light waves in a sterilization tank,but when the powder particles are less diffused in the range of light wave irradiation,the sterilization effect is affected.When the powder particles falling in the limited space of the sterilization tank,they scatter around continuously during the falling process.At the same time,the flow air in the tank is susceptible to be sucked into the particles flow field to form a particle plume.Therefore,it is one of the applied research works in gas-solid two-phase flow to shorten the falling distance when particles reach full diffusion in a finite space.In this paper,numerical simulation and experimental analysis were used to study the influence of air disturbance on the particles flow in a limited space.In numerical simulation,FLUENT software was used to calculate the particles flow in the model,and DPM model was used to track the discrete phase.In the experimental research,the experimental platform for the study of the falling motion characteristics of the particles flow in a limited space was designed and built,and the accuracy and feasibility of the numerical simulation were verified by experiments.Using the?theorem and the multiple linear regression method,the empirical formula was established by fitting the variables such as the falling distance of adhering to the wall with the particle density,the discharge outlet diameter and the particle size.Through numerical simulation analysis and experimental research,the following conclusions are drawn:?1?When there is no air outlet,the particle density increases from 471.88kg/m³ to727.28kg/m³ under the conditions that the particle size and the discharge outlet diameter remain unchanged,the initial drop concentration value increases from 0.9589kg/m³ to 1.2432kg/m³,the maximum particle velocity increases from 1.4511m/s to 1.8595m/s,and the dropping distance increases from 0.600m to 0.935m.When the particle size remains unchanged,four kinds of density particles are numerically simulated.When the discharge outlet diameter increases from 20mm to 35mm,the initial dropping concentration,maximum velocity and the dropping distance decrease with the increasing of the outlet diameter.When the particle size increases from 139.12?m to 234.63?m,the initial dropping concentration value increases from 1.1270kg/m³ to 1.3685kg/m³,the maximum dropping velocity increases from 1.7634m/s to 2.0401m/s,and the dropping distance from increases 0.830m to 1.210m.?2?During the bilateral single tuyere operation,due to the effect of air disturbance,six vortex zones are generated inside the model,and as the blowing wind speed increaseing,a direction-up air flow field is formed inside the model.When the particle parameters remain unchanged,there is no adhere to the wall in the range of 20cm below the air outlet at different wind speeds,but the particles flow does not reach the state of complete diffusion when the wind speed is 4m/s and 6m/s.At the wind speed of 8 m/s and 10m/s,the particle reaches a state of complete diffusion,but the required distance to reach a fully diffused state is greater than 20cm.?3?Under the conditions of double tuuyeres on both sides,when the particle density,discharge outlet diameter and particle size changed with any variable,the particles flow cann't adhere to the wall within 20cm below the tuyere under the suitable inside and outside wind speed,and under the action of air disturbance,it can adhere to the wall at the 20cm standard line.When the particle size and the discharge outlet diameter remain unchanged,the particle density increases from 471.88kg/m³ to 727.28kg/m³,the air velocity of the inside tuyere increases from 6.70m/s to 7.75m/s,the air velocity of the outside tuyere increases from3.80m/s to 4.70m/s,and the air velocity difference between the inside and outside tuyere ranges from 2.90m/s to 3.22m/s.When the particle size remains unchanged,the numerical simulation of four kinds of density particles is carried out.When the diameter of the discharge outlet increases from 20mm to 35mm,the air velocity of the inside and outside air outlet decreases with the increase of the outlet diameter,and the air velocity of the inside air outlet is higher than that of the outside air outlet.When the parameters of particle density and discharge outlet diameter remain unchanged,the particle size increases from 139.12?m to234.63?m,the air velocity of inside tuyere increases from 7.60m/s to 8.10m/s,the air velocity of outside tuyere increases from 4.50m/s to 5.13m/s,and the difference of air velocity between inside and outside tuyere ranges from 2.97m/s to 3.10m/s.?4?During the experiment,when the particle density increases from 471.88kg/m³ to727.28 kg/m³,the falling distance of particles adhering to the wall increases from 0.577m to0.907m,with the particle size and the diameter of the discharge outlet unchanged.Compared with the numerical simulation results,the error values of the falling distances of the four different density particles are 3.83%,-3.69%,-4.91%,and 2.99%,respectively,all within±5%.When the parameters of particle density and particle size remain unchanged,the falling distance of particles adhering to the wall decreases with the increase of the discharge outlet diameter.Compared with the numerical simulation results,the falling distance of particles adhering to the wall errors of the four materials are within±5%.When the parameters of particle density and the diameter of discharge outlet remain unchanged,the particle size increases from 139.12?m to 234.63?m,and the falling distance of particles adhering to the wall increases from 0.850m to 1.253m.Compared with the numerical simulation results,the error values of the falling distance of the particle adheres to the wall of four different particle sizes are 2.41%,2.99%,4.91%and-3.55%,respectively,which are within±5%.?5?Through the?theorem and multiple linear regression fitting method,the experience of the falling distance of particles adhering to the wall with the particle density,the particle size and the diameter of the discharge outlet are obtained.The formula is:H=0.11262×r_P^1.02996×d_P^0.75330×D^-0.55984...