Calculation Method And Its Application Study On Pollutant Concentration Of Operating Subway

With the continually advancing of national urbanization process and downtown traffic pressure increasing, the metro traffic increases year by year, is showing gradually a trend towards high-speed. The traffic and train speed increase will inevitably cause the air quality decline in the subway, and in fact, the passengers had been fallen unconscious repeatedly in the compartment of subway during themselves traveling. The calculation method and its application study of pollutant concentration in operating subway will not only provide a reliable reference for the improvement of the MTR operating efficiency, but also has important practical significance for the enhancing the air quality and riding environmental comfort inside compartment of subway. In the dissertation, according to the flow process of air from external atmosphere to subway inside, using such methods as theoretical analysis, field testing and numerical simulation etc., the evolution process and its distribution discipline of pollutant concentration had been studied on the station hall, platform, running tunnel and compartment of subway. The evolutionary process and influencing factors of the subway train barometric pressure, vehicles ventilation and pollutant concentration had been farther investigated, combined the pressure diversification during train traveling inside the running tunnel of subway. The calculation method of pollutant concentration in operating subway had been summarized, and achieved the engineering application. The main research contents completed in this dissertation are followed:(1) By theoretical analysis and field testing, the computational model of pollutant concentration in subway had been established, which took into account the pollutants changes process of the external atmosphere, station hall, subway platform, running tunnel and carriage of subway. Taking the CO2 as a tracer gas, the field sync test was accomplished on the pollutant concentration in the external atmosphere, station hall, subway platform, running tunnel and carriage of subway. The evolutionary process and its distribution discipline had been analyzed. Results shows that the CO2 concentration inside the MTR is directly related to the number of passengers, and the concentration of pollutants in carriage as well as internals is higher than others region of passengers stayed during passenger flow peak. (2) The numerical simulation model had been established, which could imitate the relative motion between the train and running tunnel, and the train traveling course in tunnel had been simulated really. The characteristic and change mechanism of the carriage surface pressure had been analyzed during train traveling in interval. According to the trait of the MTR, such influence factors to the carriage surface pressure as running tunnel ventilation, subsidiary structure of subway, the speed and type of train, etc. had been discussed. Meanwhile the relevant empirical formula had been put forward.The results show that:1) the blockage ratio of subway, between 0.48～0.56, typically larger than high-speed mountain tunnel, easily leads to the piston effect during train traveling inside intervals.2) The length of subway, between 1000～3000m, is not conducive to reducing the train pressure.3) Reducing the area, increasing the volume and open the air valve of shaft helps reduce the pressure of wagon. Interval tunnel ventilation can also change the maximum and minimum body pressure, peak pressure, the magnitude of the pressure on the body less affected.(3) Taking the train compartments as the research object, and putting the barometric pressure, carriage ventilation and pollutant concentration as a system, combined the seal condition, fan performance curve and pipe network characteristic curve of compartment, the uniform calculation model integrated barometric pressure and ventilation of carriage, as well as pollutant concentration of compartment had been established, which considered the evolution of carriage surface pressure during train traveling inside subway tunnel.(4) Based on MATLAB software, the application program for calculating the pollutant concentration in subway was explored, which could input parameterized, and has both lumped parameter analysis and modular call function. The application of the program in calculation pollutant concentration of 2 stations and 1 interval of Guangzhou Metro Line 2, as well as 4 stations and 2 intervals of Guangzhou Metro Line 3. The calculator results are consistent with the field values, which proved the reliability of the uniform calculation model.(5) The evolution process of pressure difference, leakage, fan air flow and pollutant concentration of carriage had been analyzed, which considered the difference air-tightness and the evolution of train barometric pressure during its traveling in interval.(6) Took the pollutant concentration inside the compartment as a reference standard, such effect factors had been discussed as train speed, the air-tightness of carriage, interval ventilation, subsidiary structure of subway and the maximum output air pressure of fan, etc. which features the difference between high-speed railway and subway. The results will provide a reliable reference in improving the operating efficiency of the existing MTR lines and the design of subway in future.The results show that:1) Conditioned lower train speed, the cumulative effects of pollutants concentration inside carriage are not significant, and the concentration of pollutants can be regarded as constant.2) The total air volume from internals into sealed carriage is least than the unsealed, and it is necessary to pay much attention to the sealed carriage when the train speed increased.3) Open the air valve and the selection of vehicles, whose fan output pressure is relatively higher than others help to improve air supply, meanwhile to reduce the concentration of pollutants inside compartment.