Research On Aerosol Propagation Characteristics And Optimization Of Ventilation Scheme In Elevator Car

In recent years,with the outbreak of respiratory infectious diseases such as swine flu and novel coronavirus pneumonia,aerosol transmission has become a common way of virus transmission.As a relatively closed public space,the elevator car has a high risk of cross infection caused by aerosol transmission among people.Therefore,the study of efficient ventilation scheme has important practical significance for controlling the transmission of viral aerosol in the elevator.The specific work content of this thesis is as follows:Based on the gas-particle two-phase flow principle of computational fluid dynamics,the RNG k-ε turbulence model based on RANS equation is used to calculate the continuous phase,the Lagrange method is used to track the particle phase,and the SIMPLE algorithm is combined to simulate the diffusion of human exhaled aerosol in the elevator car.Based on the single passenger model,the aerosol diffusion distribution generated by human body talking under four ventilation schemes: natural ventilation hole air supply,rear air supply at the top,two-sided air supply at the top and central air supply at the top was simulated.On this basis,the ventilation efficiency under different ventilation schemes was evaluated.The results show that the aerosol particles stay in the front area of the top of the elevator for more than 36 s under the scheme of natural ventilation hole.In the top rear air supply scheme,the aerosol particles first spread in an arc of "C" and then gather in the rear side of the human body.In the top two-sided air supply scheme,the aerosol mostly sticks to the wall.In the top center air supply scheme,aerosol diffusion performance is strong and aerosol suspension amount in elevator space is small.When the aerosol diffusion reaches 36 s,the ventilation efficiency of the top rear air supply scheme is 41.2%,that of the top two sides air supply scheme is 45.1%,that of the top center air supply scheme is 73.9%,and that of the natural ventilation hole air supply scheme is the worst.Based on the two-person passenger model,two typical working conditions of human body standing face to face and human body standing side by side were set up.The diffusion and propagation of aerosol emitted by human cough under two ventilation modes of top side air supply and top center air supply were simulated.Aerosol exposure risk and inhalation risk were assessed by comparing the number of aerosol suspended particles in the elevator with the number of particles inhaled orally by healthy people.The results showed that the aerosol exposure and oral particle inhalation of healthy people were significantly reduced in the top-centered ventilation scheme compared with the top-sided ventilation scheme under the two conditions of standing face to face and standing side by side.When human body is standing face to face in the elevator,the initial inhalation time of aerosols in the top-centered ventilation scheme is delayed from 6s to 18 s in the top-sided air supply scheme.Based on the above studies,it can be seen that the top-centered ventilation scheme can effectively reduce the residence and disturbance time of aerosol in the airtight elevator environment,and reduce the possibility of aerosol exposure risk and inhalation risk.Based on the multi-passenger model,two ventilation schemes,top center air supply and top side air supply,were selected to simulate the diffusion and propagation of aerosol produced by human cough.Based on the analysis of aerosol particle residues,aerosol particle catches contacted by passengers at different locations and aerosol concentration levels,the following conclusions are drawn: air supply outlets at different locations will produce different airflow disturbances,and local barrier areas will appear,which can block or reduce the direct contact between aerosol and passengers in a short time.In the top-centered air supply scheme,the central air supply scheme meets the backward diffused aerosol,and the air supply scheme can change the direction of aerosol movement.The aerosol exposure risk and aerosol contact risk of the rear passenger are significantly reduced compared with the top-sided ventilation scheme.