Study On The Influence Of The Form Of Subway Ventilation Pavilion And Shaft On Tunnel Ventilation Effect

This paper focuses on finding the best methods to design subway ventilation pavilion(surface facility) for Xi'an city subway.The pavilion caps the ventilation shaft (underground facility) that leads down and into the main subway structure.Special attention is paid to the density of population in the area and the use of varied ventilation pavilion schematics in the construction of Xi'an city subway.The field data collection includes the use of questionaires,measurements,and photographs from subway ventilation pavilions in other cities of China.The paper also reviews measuring methodology for Guangzhou,Shanghai and Nanjing cities subway ventilation pavilions in terms of shape,structure and ventilation effects.The subway ventilation pavilion is a very important facility.It connects surface and underground structures.The established design practice not only decides on the ventilation effect with changes in the quality of atmosphere,but also effects the architectural appearance of the pavilion with strong influence on the city landscape.Research findings provide suggestions as to how harmonize with the landscape and reduce the technologinic impact on the environment from Xi'an subway operations.All suggestions are given to designers and managers for reference.This paper introduces CFD software simulations for different forms of piston effects occured in the ventilation shafts.It also describes changes in the air volume at the pavilion discharge outlet with different forms of ventilation shafts,as well as at the exhaust air chambers above and below while the train in the tunnel slowing down to stop.The methodology of dynamic meshes was used to simulate air flow alterations during subway operation.The ventilation effect in the straight shaft proved to be better than that the inclined one,however the inclined shaft provides better flexibility in solving certain engineering layout design problems.