复杂地形高含硫天然气风洞扩散实验及安全防护距离

Wind tunnel dispersion experiments and safety protection distances of high sulfur natural gas in complex terrains

为了探究高含硫天然气在复杂山地条件下的扩散规律、分布特征和外部安全防护距离,建立了泄漏源周边半径3 km范围的山区地形模型,分别测试了8个典型风向、3个来流风速共24种工况下的气体浓度,采用基于风险的方法研究了各类防护目标的安全防护距离。研究结果表明:①高含硫天然气的扩散过程可归纳为“顺坡扩散”和“切坡扩散”两种模式,风速、风向、地形及其相互作用是影响扩散过程和危害范围的重要因素,扩散过程表现出非均匀、非定常特征,并且分布各异;②复杂地形影响下的危险区域会沿多个方向扩展,并且形状很不规则,Ⅲ~Ⅱ级危险区域的最大影响距离是东北方向1500 m,Ⅰ级危险区域的最大影响距离是东北方向1200 m;③与平坦地形显著不同的是,复杂地形下的风向对扩散危害范围有显著影响,风速为1 m/s、2 m/s和4 m/s时,W风向最大浓度分别是N风向最大浓度的18.2倍、26.8倍和22.9倍;④在地形和风向共同作用下,不同防护目标在不同方向的安全防护距离为60.5~727.8 m,同一类防护目标在不同方向的安全距离相差约2倍。结论认为,采用风洞实验与定量风险评估相结合的方法,可以全面、有效地研究高含硫天然气扩散特征和安全防护距离。

In order to investigate the dispersion laws, distribution characteristics and external safety protection distances of high-sulfur natural gas in complex terrains, this paper established a mountainous terrain model with a radius of 3 km around the leakage source. Then, the gas concentration was tested in 24 working conditions of 8 typical wind directions and 3 wind velocities. Finally, the safety protection distances of different protection targets was studied using the risk based method. And the following research results were obtained. First, the dispersion process of high-sulfur natural gas can be divided into two modes, i.e., "down-slope dispersion" and "slope-tangent dispersion", and wind velocity, wind direction, terrain and their interaction are the main factors influencing dispersion process and hazard scope. In the process of dispersion, it presents the characteristics of heterogeneity, unsteady state and nonuniform distribution. Second, under the influence of complex terrain, the hazardous area extends in several directions and its shape is quite irregular. The maximum influence distance is NE 1 500 m in level Ⅲ-Ⅱ hazardous areas and NE 1 200 m in level Ⅰ hazardous areas. Third, obviously different from that in a flat terrain, the wind direction in a complex terrain has significant influence on the hazard scope of dispersion. At a wind velocity of 1 m/s, 2 m/s and 4 m/s, the maximum concentration of W wind direction is 18.2, 26.8 and 22.9 times that of N wind direction. Fourth, under the joint action of terrain and a wind direction, the safety protection distances of different protection targets in different directions are in a range of 60.5–727.8 m, and the safety distances of the same kind of protection targets in different directions are about 2 times different. In conclusion, the combination method of wind tunnel experiments and quantitative risk assessment can be used to comprehensively and effectively study the dispersion characteristics and safety protection distances of high-sulfur natural gas.