Research On Propagation Law And Countermeasures Of Respiratory Particles In Public Buses

With the continuous growth of the domestic public buses production and external output,how to improve the indoor air quality of buses has become the focus of attention in the context of the COVID-19 epidemic.Because of their convenience and economy,the buses have a large audience and have become an integral part of people’s daily life.However,their indoor space provides a way for the spread of respiratory infectious diseases due to their limitations,randomness of passenger identity and crowd aggregation,which leads to the risk of clustered infection in the public transportation system.Therefore,it is urgent to study the diffusion and prevention of respiratory particles in public buses.By summarizing the research status of domestic and foreign experts on particle diffusion,the main research content of this paper was determined.A numerical simulation method for indoor propagation of respiratory particles in the public buses was established.Through laboratory experiment and numerical simulation,the most harmful respiratory conditions to human health were obtained.On the basis of the above,this paper took a certain type of bus as the research object,observed the diffusion law of respiratory particles produced by passengers in different regions of the bus by means of numerical simulation,optimized and improved the parameters of the air conditioning system of the bus based on the response surface method,so as to reduce the risk of infection of passengers in the bus.The results showed that:(1)The Realizable k-εmodel was adopted to simulate the turbulent flow of gas in the bus,the motion state of respiratory particles in the flow field was described based on the discrete phase model,and Coupled algorithm was adopted to realize the coupling of pressure and velocity in the fluid domain.Therefore,a numerical simulation method suitable for the propagation of respiratory particles in the public bus was established.(2)Through the combination of numerical simulation and experimental verification,it could be known that sneezing condition was the most harmful condition to human health,the respiratory particles generated by sneezing condition could spread 3 meters,and the dangerous area was distributed in a fan shape with an area of 0.58905m~2.(3)In the initial bus model under working condition 1,the distance between the source of respiratory particles and the return air outlet was the furthest,leaded to a long particle migration path,and the residual number of respiratory particles in the front and middle areas of the bus was large.The indoor air quality under this working condition was the worst.The breathing particles in the bus could be quickly and effectively removed under condition 3.(4)Based on Box-Behnken experimental design method,a mathematical model reflected the relationship between three experimental design factors and particle removal efficiency of passenger air conditioning system was established.The optimal parameters of the bus air conditioning system were obtained:the length of the air outlet was600mm,the air supply Angle was 25°and the air supply speed was 5m/s.The numerical simulation results showed that the improved air conditioning system could enhance the removal effect of respiratory particles,and reduce the residual quantity and concentration of respiratory particles.It was most beneficial to reduce the risk of infection of passengers in the bus by dividing and evaluating the area in the bus room and placed suspected pathogenic passengers in the A7 and A8 area.