管道压力对天然气射流火热辐射灾害的影响

Impact of the pipeline pressure on the thermal radiation hazards of the natural gas jet flame

天然气管道时常受到破坏,并诱发巨大的射流火焰,可能引燃周围建构物体。系统地分析了管道压力对天然气射流火热辐射灾害的影响,以建立天然气射流火热辐射灾害的系统定量分析方法。基于压力管道小孔泄漏模型和权重-多点源热辐射计算模型,建立了目标物体最大入射热辐射通量、管道压力和目标物与泄漏小孔水平距离的定量关系式。进而选定10 k W/m^2和31.5 k W/m^2作为城镇建筑物遭受引燃和机械破坏的热辐射通量阈值,得到了不同管道压力下天然气射流火热辐射灾害范围。计算结果表明,GB 50028—2006《城镇燃气设计规范》依据管道压力所规定的燃气管道与建筑物的安全间距不能完全满足天然气管道破坏时射流火焰的安全要求,与某武汉天然气管道射流火事故后果一致。

This paper presents a systematic quantitative method to predict the thermal radiation hazard likely to be caused by serious natural gas jet flames. As is known,accidents have often been reported due to the urban pipeline burst or explosion. The reason or the cause that may account for such hazards can be of a great variety. The first of such accidents may attribute to the gas leakage. To solve the problem of leakage,it is necessary to calculate and determine the flame length,lift-off distance,radiant fraction,heat release rate of the natural gas jet flame and its mass flowing rate. With the above mentioned four physical parameters,it is of great importance to pay ever closer attention to the weighted multipoint source radiation and predict the thermal radiation from the jet flames under different pipeline pressures. And,the third kind of problems involves the correlation between the maximum thermal radiation flux and the pipeline pressure while the gas is moving in the horizontal distance away from the jet flame. And,the fourth problem seems to be with the maximum thermal heating flux that is linearly proportional to the pipeline pressure. To deal with the problem,the engineers have to choose carefully the 10 kW / m^2 and 31. 5 kW / m^2 as the thermal radiation threshold value of the building ignition and mechanical structure damage,respectively.By using the maximum thermal heat flux correlation and the thermal radiation threshold values,the engineers responsible for the pipeline construction have to determine finally the scopes of the thermal radiation hazard due to the jet flames under different pipeline pressures. In particular,the safety distance between the city gas pipeline and the construction site in Code for Design of City Gas Engineering GB 50025—2006 should be carefully checked in hoping to prevent the thermal hazard damage of the jet flames on the building by using the systematical method. Thus,the calculation results show a perfect account for the consequence of the recent natural gas jet fire accidents in Wuhan city. The systematically quantitative method proposed in this paper can thus be thought qualitative enough to experience the likely hazardous risks＇ assessment of the potential accident release scenarios in the said industrial systems.