The Analysis And Optimal Research On Air Distribution In EMU Air Conditioning Duct And Carriage

With the wide spread of COVID-19 in the world,people put forward higher and higher requirements for indoor air quality.For the relatively closed space of EMU carriage,it is not only necessary to ensure that the parameters such as air velocity and ambient temperature in the passenger compartment are in the area with high human comfort,but also to effectively inhibit the spread of virus in the special space.Based on the RNG k-ε turbulence model,numerical simulation of air distribution in the air supply duct and compartment of EMU is conducted in this paper.In the simulation calculation,the influence of air supply duct optimization,solar radiation and human body heat load on the air distribution in the carriage are considered,and the droplet diffusion process in the carriage is simulated.Firstly,the numerical simulation method is used to study and optimize the air outlet uniformity of air supply duct of EMU.In the original scheme of air supply duct,the non-uniformity coefficient of air duct outlets on both sides is large,and there is an obvious stratification phenomenon in the velocity field at the orifice at the bottom of the middle air duct.After initial optimization,the non-uniformity coefficient of one side air duct outlet is reduced from 0.202 to 0.085,and the non-uniformity coefficient at the outlet of the secondary side air duct is reduced from 0.207 to 0.087,but there is still obvious stratification in the velocity field at the orifice.After the final optimization,the phenomenon of velocity stratification at the orifice plate is alleviated.In the final scheme,the non-uniformity coefficient at the outlet of the air duct on one side is reduced to 0.053,and the non-uniformity coefficient at the outlet of the air duct at the second position side is reduced to 0.057.Then,the influence of air supply duct optimization on the velocity field in the passenger compartment is studied,and the air distribution in the passenger compartment of EMU under different passenger conditions is analyzed based on the optimized air supply duct data.In the no-load carriage,the speed distribution of passenger area is relatively uniform,and the air velocity is roughly in the range of 0-0.25m/s.under the influence of solar radiation,the temperature difference at the seats on both sides of the no-load carriage does not exceed 2℃.After loading the human body heat on the seat,the temperature in the passenger area is about24℃,and the temperature difference basically does not exceed 3℃.Finally,the discrete phase model is used to simulate the diffusion process of droplet particles produced by passenger coughing in EMU carriage.By analyzing the movement track and concentration distribution of droplet particles in the passenger compartment,it is found that under the influence of the air supply flow in the passenger compartment,the droplet particles blocked by the seat back in front of the passenger diffuse rapidly in the plane perpendicular to the spraying direction,basically completing the diffusion in the plane in 5S,and then start to diffuse in the spraying direction.Moreover,it has the greatest impact on the two rows of seat areas before and after the jet source.The droplet concentration in the passenger sitting breathing height plane is basically greater than that in the passenger standing breathing height plane.