Numerical Simulation Research Of Underground Garage Ventilation And Pollutant Diffusion

In recent years, along with the rapid development of economic construction in our country, the ownership of motor vehicles increases rapidly. The demand for parking space also increases rapidly. But in real cases, parking space is limited. Drivers usually can not find parking space.This phenomenon has become a common problem that troubles city dwellers. At present, based on the problems of parking and urban land tension,to build garages underground has become one of the principal methods to solve parking problem. Compared with the ground buildings, underground garages, generally in the closed or semi-closed state, has less channels with the outside world. So it is difficult to ventilate with the outside world adequately. For cold start and idle speed, vehicles will produce large number of harmful gas, of which carbon monoxide contents highest. The carbon monoxide do great harm to staff of the garages and drivers. In order to improve the air quality of garages underground, we usually utilize mechanical ventilation to realize the air exchange of outside world to the garages underground.However, energy demand of mechanical ventilation is large. In consideration of the air quality of underground garages, we must choose the correct methods of ventilation to reduce the energy consumption and to achieve the goal of energy saving. The ventilation rate affects the underground garage air quality and energy consumption of ventilation system directly. So the set of ventilation rate is particularly important. The main work as follows of this paper is:(1) Analyzed the different design and empirical formula of the ventilation rate, we found that the ventilation rate method and index method of single car was unreasonable. The design of ventilation rate should be based on CO concentration limitation and comprehensive ventilation dilution method should be adopted.(2) In view of the mechanical ventilation way, studied the underground garage ventilation conditions of different schemes through the method of numerical simulation,analyzed the velocity field, CO concentration field and temperature field distribution characteristics. In view of pollutant concentration, discussed tree different pedestrian routes from garage to store entrance.On this basis, discussed the relationship between the different ventilation rates and pollutant load. According to the simulation analysis,we know that under part of pollution load condition, air volume percentage demand is less than the pollution load percentage. And the trend is more obvious when the pollution load percentage is higher.(3) Preliminary discussed the application of natural ventilation in the underground garage. And the thermal pressure natural ventilation condition was studied. According to simulation calculation, it can be found when we met the conditions of thermal natural ventilation better, thermal pressure ventilation rate is bigger, which can satisfy the requirement of the underground garage ventilation basicly.