Numerical Simulation And Detection Of Pollutant Diffusion In Underground Garage

With the continuous development of economy,the number of cars in our country is showing a rapid growth trend.The increasingly congested overground space and the gap of a large number of parking spaces make underground garages an essential facility for urban construction.However,the underground garage is in a closed state for a long time and is basically isolated from outdoor natural air and sunlight,so the pollution situation gets serious,thus affecting human health.The composition of CO in the main pollutants in the underground garage is much higher than that of other pollutants,which is also the most harmful to human body.Therefore,in order to improve the air quality of underground garages,it is necessary to find an appropriate ventilation scheme to limit the CO concentration within the specified range.In this paper,the distribution of temperature and CO concentration in the underground garage of Jiacheng Square in Beijing is studied by means of on-site detection and numerical simulation,and the accuracy of numerical simulation is verified.Through numerical simulation and comparison of different ventilation schemes,the ventilation scheme with the best performance is found.The main work and conclusions of this paper are as follows:(1)Comparing the ventilation design standards of underground garages at home and abroad,it is found that there is no clear stipulation on CO concentration limit in China and the current ventilation design regulations are unreasonable.After comparing different ventilation design methods,it is considered that the ventilation design should be based on the CO concentration limit and the comprehensive ventilation model should be used,and the ventilation of the underground garage in this paper is calculated by this method.(2)The underground garage of Jiacheng Square was measured on the spot to determine the influence of different time periods,temperatures and the rules of car entry and exit on carbon monoxide concentration distribution.After analyzing the measurement results,it is found that the concentration distribution in the horizontal direction of CO is closely related to the underground garage layout,lane distribution and the frequency of vehicles entering and leaving.The concentration distribution in the vertical direction is characterized by "high and low".(3)Establish the mathematical model of the underground garage according to computational fluid dynamics,and select Fluent as the numerical simulation software to carry out numerical simulation on the underground garage.After comparing the simulation results with the measured results,it is found that the errors of the two are small and the change trend is the same,which verifies the accuracy of the numerical simulation.(4)Numerical simulation is carried out on several common ventilation schemes at present,and appropriate evaluation indexes are selected to evaluate and compare them.It is found that compared with the traditional ventilation system,the induced ventilation system not only has better ventilation effect,but also has wider airflow coverage,which can effectively avoid the generation of airflow dead corners and pollutant vortex areas.The scheme also has the advantages of flexible arrangement,economy and practicality,and is the best ventilation scheme.