基于交通风条件多点进出城市地下道路CO污染物浓度分布特性预测模型

多点进出城市地下道路结构形式复杂且位于城市人员密集区，机动车在行驶过程中排放的污染物(CO、NO_<i>x等)不仅将对隧道内驾驶人员的健康产生影响，同时还会给隧道洞口附近民众的居住环境及健康带来影响。为此，以机动车流排放污染物CO浓度分布规律为重点研究对象，依据质量守恒定律、并联风路理论，并结合上海和长沙4条隧道现场实测以及1∶8缩尺模型试验研究方法，开展了关于多点进出城市地下道路交通风以及机动车流排放污染物扩散特性的研究；基于研究结果，提出了交通风条件下多点进出城市地下道路机动车流排放污染物CO浓度分布特性预测模型构建方法，包括交通风速V_r、对流传质系数h_m和扩散特征系数K等关键参数的确定方法；长沙市营盘路湘江隧道实测结果验证了该模型的有效性，交通风以及污染物浓度预测模型计算值与实测值的误差评估值I_A分别为0.992和0.916。当已知隧道结构特征和交通特征时，利用该计算模型即可预测评估多点进出城市地下道路内沿机动车行驶方向各断面的平均交通风速、机动车流排放污染物CO平均浓度；同时可定量评价各分(合)流匝道对主隧道CO浓度分布特性的影响规律。研究结果可为多点进出城市地下道路科学选址及其通风系统优化设计与节能运行提供参考依据。

A Prediction Model for Distribution of CO Pollutant Concentration in Urban Bifurcated Tunnel Based on Traffic Wind Conditions

Multipoint access urban underground roads structure form complex and located in the city densely populated areas. Pollutants, such as CO and NO_<i>x, discharged by motor vehicles in the process of running not only threaten the health of drivers in the tunnel but also affect the living environment and health of the people near the tunnel entrance. In this study, the distribution of CO concentration produced by motor vehicle emissions was investigated using the law of conservation of mass, theory of parallel wind paths, and field measurements for four tunnels in Shanghai and Changsha. In addition, experiments were conducted using a 1:8 scale model. The diffusion characteristics of traffic wind and vehicle emissions from multipoint access urban underground roads were studied. A prediction model for distribution characteristics of the CO concentration produced by vehicles flowing in and out of urban underground roads under traffic wind conditions was proposed. The proposed model included the determination of key parameters, such as the traffic wind speed V_r, convective mass transfer coefficient h_m, and diffusion characteristic coefficient K. The measured results of the Xiangjiang tunnel at Yingpan Road in Changsha City verified the effectiveness of the proposed model. The error evaluation values Index of Agreement (I_A) of the traffic wind and pollutant concentration prediction model were 0.992 and 0.916, respectively. When the tunnel structure and traffic characteristics are known, the calculation model can be used to predict and evaluate the average traffic wind speed and average concentration of CO emitted by motor vehicles in each section along the direction of motor vehicles on the multipoint access urban underground road, and to quantitatively evaluate the influence of each off-ramp (combined ramp) on the distribution characteristics of the CO concentration in the main tunnel. The obtained results can provide a reference for scientific site selection, optimized design of ventilation system, and energy-saving operation of multipoint access urban underground roads.