建筑群外空间城市燃气泄漏扩散浓度场模拟

Simulation on the concentration field of gas diffusion resulted from gas leakage in a group of urban buildings

由于城市建筑群区域人口密集且扩散气象条件不利,燃气一旦泄漏,极易造成人员伤亡和财产损失,因而对建筑物群外空间燃气泄漏的扩散浓度场及其变化规律进行分析十分必要。为此,通过对城市燃气管道及泄漏过程进行合理的假设和简化分析,以三维湍流模型为基础,采用CFD软件对建筑物群外空间天然气连续泄漏源的扩散进行了数值模拟,对比分析了环境温度、湿度对天然气扩散的影响及浓度场的变化规律。案例分析的结果表明:天然气泄漏后在竖直方向的扩散速率明显大于在水平方向上的扩散速率;随着环境温度的增加,在竖直方向和水平方向上,天然气扩散的速率均呈现出增加的趋势;随着环境相对湿度的增加,天然气在竖直方向扩散速率逐渐减缓,但在水平方向扩散速率却逐渐增加,在竖直面上扩散面积有所降低,而在水平面的影响面积逐渐增加。该研究结果可为控制和降低天然气在建筑群空间泄漏所造成的危险性提供参考。

Personal casualties and property loss will be easily caused once gas leakage occurs in a group of buildings in a city, where there is a dense population and bad condition for gas diffusion. Thus, it is quite necessary to analyze the concentration field of gas diffusion and its changing rule in an accident of gas leakage in such a case. In view of this, reasonable assumption and simplified anal ysis were first made of a city gas pipeline network and the leakage process. Then, based on the κ-ε （K- epsilon） turbulence model ing, the CFD software was adopted to simulate the diffusion of continuous gas leakage source in a group of buildings. On this basis, a comparative analysis was performed of the impact of ambient temperature and humidity on gas diffusion as well as the changing rule of the concentration field. The following findings were achieved by case analysis. As soon as gas leakage occurs, the diffusion rate is obviously bigger vertically than that horizontally; with the rise of ambient temperature, the diffusion rate is increasing in both direc tions; with the increase of relative humidity, the diffusion rate is gradually slowing down vertically but is increasing horizontally by degrees, as a result, the diffusion area is reducing in the vertical level but is increasing in the horizontal level. This study will provide a reference to mitigating the risk in gas leakage occurring in a group of buildings.