Air Distribution Analysis And Air Quality Evaluation Inside High-speed Train

With the rapid development of social economy,people’s living standards have been gradually improved.High-speed trains have become an essential means of transportation for people to travel,and people’s requirements for comfort have also improved.However,the comfort of people traveling by train is affected by the wind speed,temperature and air quality inside the carriage,so it is necessary to analyze the air distribution and air quality inside the carriage of the high-speed train.In this thesis,one carriage of the high-speed train has been taken as an example to be investigated.The corresponding three-dimensional CAD model has been established and the numerical simulation of its internal air distribution(velocity field,temperature field)is carried out by using the Fluent software to obtain an appropriate air supply mode.The thermal comfort of passengers and air quality of in the carriage are also studied under the proposed air supply mode to verify the validity of the air supply mode.The main contents are as follows:By studying the influence of different air supply positions on the air distribution in the carriage,the reasonable air supply mode that makes the temperature and velocity distribution of the air inside the carriage more uniform is obtained,that is,the air supplies from three air outlets(i.e.at the roof,under the window and at the ankle offered)are simultaneously offered.Considering the temperature requirements for summer and winter are different,the effects of different air supply ratios on the airflow distribution in the carriage in summer and winter are studied.It is concluded that the most suitable air supply ratio is 70%of the roof,10%of the window and 20%of the ankle in summer and the most suitable air supply ratio is 20%of the roof,20%of the window and 60%of the ankle in winter.Considering the obvious impact of the solar radiation in summer on passengers’ thermal comfort,the proposed air supply mode in summer is further discussed.It is concluded that the average temperature inside the carriage is 26.6℃ with the solar radiation and the average temperature is 26.2℃ without the solar radiation,which satisfy the thermal comfort requirement of passengers.Finally,the evaluation of the air quality inside the carriage with the proposed air supply mode is carried out involving the analysis of the CO2 concentration,DR(Draft Rate),PMV(Predicted Mean Vote)and PPD(Predicted Percentage of Dissatisfied)in the carriage.It is concluded that the CO2 concentration in the carriage is around 0.23%near the passengers’breathing port and the one elsewhere is controlled below 0.15%,which meets the requirements of passenger comfort for CO2.The level of DR,PMV and PPD in the carriage reaches the specified standards,which indicates that the air flow generated by the proposed air supply mode inside the carriage is moderate to passengers.The result shows that the air quality in the carriage is good and the proposed air supply mode is reasonable.