青藏铁路羊八井一号隧道空气污染数值模拟

Numerical Simulation of Air Pollution for Yangbajing No. 1 Tunnel of Qinghai-Tibet Railway

内燃机车排放的大气污染物是铁路隧道空气污染的主要来源,其污染特性受到排放源强、隧道内风速、扩散系数、初始浓度、边界浓度等诸多因素的影响。文章根据大气扩散方程建立了描述铁路隧道内空气污染物浓度分布的数学模式,提出了用有限体积法求解铁路隧道内空气质量方程的方法,并对影响隧道内空气污染物浓度分布的因数进行了灵敏度分析。结果显示内燃机车污染物排放源强和隧道内风速是影响铁路隧道内空气污染物浓度分布的关键因素,初始浓度和边界浓度的影响也较为显著,扩散系数的影响很小,在有风的情况下可以忽略。将模式应用于青藏铁路羊八井一号隧道内NOX污染规律的数值分析,模拟表明隧道内NOX浓度最大值出现在机车车头所在的位置,最大浓度为15.02 mg/m3。

Pollutants emitted by diesel locomotive are main sources of air pollution inside railway tunnel, and characteristics of air pollution inside railway tunnel are affected by emission rates of pollutants from diesel locomotive, wind speed along tunnel, atmospheric diffusion coefficient, initial concentration and boundary concentration of the pollutants. A numerical model for the concentration distribution of air pollutants inside railway tunnel was established based on equation of atmospheric diffusion, and concentration equation was solved using finite-volume model, and the effects of input parameters on pollutant concentrations inside tunnel were discussed using sensitivity analysis. Results of sensitivity analysis showed the wind speed along tunnel and emission rates of the pollutants from diesel locomotive are the most important factors that affect the ＇Concentration distribution of pollutants inside railway tunnel, the effects of initial concentration and boundary concentration are also obvious, and effect of atmospheric diffusion coefficient which is very small can be ignored in the windy conditions. As an example, the numerical solution of concentration distribution of NOx for Yangbajing No. 1 Tunnel of Qinghai-Tibet Railway was given. Results indicated that the maximum concentration of NOx inside the Tunnel appeared in the locomotive location, with the maximum concentration of NOx as 15.02 mg/m3.