Simulation Analysis Of PM2.5 Diffusion In Railway Vehicles

As a kind of underground rail transportation,subway has become the most important means of transportation for urban people.It is of great significance to study the movement law and emission characteristics of PM2.5 in subway cars,analyze the relevant factors affecting the air quality in subway cars,and explore feasible improvement measures,so as to improve the air quality of subway cars and create a comfortable and healthy transportation environment for passengers.Based on a subway car type B air duct and the car as the research object,the numerical research methods,simulation and optimization of subway car duct,and then research under different supply air pollution degree of the distribution of PM2.5 in the car and the car key cross section,the influence of contrast supply Angle,temperature,humidity,particle density,particle size distribution of PM2.5 diffusion effect,The paper analyzes the influence of the platform on the carriage’s thermal environment and air quality in summer and winter,and takes cigarette smoke as an example to analyze the influence of endogenous pollution on the carriage’s air.The results show that:(1)The distribution and deposition of PM2.5 in subway cars in air supply are as follows: escape amount > standing passenger > roof > side wall > door > sitting passenger > window > floor > seat.The cleanliness of carriage walls is as follows: seat > floor >side wall > door > roof > window.Subway staff should clean up in different degrees according to this.Passengers sitting under the reentry are more polluted than those in the middle,while passengers standing at the end are more polluted than those in the middle and under the reentry.(2)The fresh air filter and supply air filter of subway cars should be replaced with Z1 +M5 or G3 +Z3.(3)PM2.5 elimination ability and the pollution degree of sitting passengers in the middle of the carriage are negatively correlated with the opposite air supply Angle,while the pollution degree of standing passengers and sitting passengers under the return air outlet are positively correlated with them.When air supply temperature rises 2℃,particle deposition increases by 2%.When air supply humidity increases by 10%,particle deposition increases by about 1%.Considering the minimum pollution to human respiration section,air supply mode with large Angle,high temperature and low humidity should be selected as far as possible.(4)The maximum regional pollution caused by platform in summer is 6 times higher than that in winter.In summer,standing passengers should choose side rear area or middle rear area;sitting passengers should choose middle rear area;In winter,passengers should choose the front seat area or the middle front seat area for standing posture,and passengers should choose the middle front seat area for sitting posture.(5)The existence time of PM2.5 released from point sources is usually less than 50 s,and the free combustion of a single cigarette can cause the overall PM2.5 concentration of the carriage to reach 1.9μg/m~3.Locally,it can lead to mild pollution in the sphere basin with a radius of 0.4m for a long time,and the air quality in the sphere basin with a radius of 0.7m is good.