Simulation And Optimization Of Air-conditioning Airflow In Subway Compartment

With the vigorous development of metro,the comfort problem in subway carriages has been paid more and more attention.Because the subway compartment is confined space,the passenger capacity is large,the personnel is dense and the air circulation is not good,the comfort of the air conditioning environment is very important.The comfort of passengers is closely related to the distribution of airflow in subway carriages.Good airflow organization not only requires reasonable temperature distribution in the compartment,wind speed meets the standard,but also requires uniform distribution of temperature field and velocity field in the compartment.Therefore,it is necessary to use the combination of Subway car field measurement,questionnaire investigation and numerical simulation to study the air conditioning parameters and airflow organization in subway carriages,so as to provide a theoretical basis for the improvement of metro compartment environment in the future.In this paper,the air low organization simulation of a section of the middle compartment on Shenyang metro line Line 2 is carried out in winter and summer.In the first part,the air return parameters of the subway compartment from December 2017 to October 2018 and the parameters of each measuring point are measured in the field for 90 days,and the temperature value and wind speed value of each measuring point are obtained.At the same time,the questionnaire was distributed to the passengers in the carriage,and the current problems of the airflow organization of the carriage were understood subjectively and objectively.Based on the measured results of a certain day,gambit software is used to draw the model diagram of manned subway compartment which is consistent with the measured situation,and the mathematical model of metro compartment coupled by standard κ-ε heat transfer transmission based on Reynolds average equation is established and numerically simulated by Ansys software.The simulated temperature value and wind speed value of each measuring point are compared with the measured results,which verifies the feasibility of the simulation.In the second part,the model of metro compartment with 228 passengers is established,and the different air supply conditions in winter and summer are simulated,and the influence of human heat dissipation on the surrounding environment is considered in the simulation process.By studying the influence of different air supply temperature and air supply speed on the airflow organization in the compartment,the optimum air supply parameters of metro compartment under full load in winter and summer are obtained.In the third part,on the basis of the original air flow organization scheme,the position of the vents is changed to the compartment floor under the same section seat under the original outlet,and the optimized metro compartment model is simulated numerically to verify the feasibility of the optimization scheme.The research in this paper shows that changing the air supply temperature has less effect on the velocity field in the compartment.And the change of air supply speed has a great influence on the temperature field in the compartment.Winter air supply speed 1.6m/s,air supply temperature of 24℃,the car comfort is better,summer air supply speed 1.7m/s,air supply temperature 19℃ car comfort is better.The optimized air flow organization form of metro compartment can effectively reduce the short circuit phenomenon of air supply and the problem of high wind speed of passenger head under the back vent,so that the temperature field and velocity field in the compartment are evenly distributed and the passengers feel more comfortable.