Abstract
Using the hydrodynamic software Fluidyn, a numerical model comprising a top‐sealed vertical inspection well and a horizontal well with openings at both ends was built based on symmetry, to study the explosion propagation of flammable gases in typical municipal sewage pipelines. The vertical well had a diameter of 0.7 m and different depths (2 m, 4 m, and 6 m), and the horizontal well had a diameter of 0.8 m and a length of 20 m at both sides. The effects of different ignition positions, well depths, and gas compositions and concentrations on the explosion characteristics and rules governing the propagation of flammable gases in a municipal sewage pipeline were investigated. The findings suggest that different ignition positions (at the top, middle, and bottom of the inspection well) did not lead to a significant difference between peak explosion pressure and temperatures but had a substantial influence on the propagation velocity of the explosion flame near the corner of the junction between the vertical inspection well and the horizontal well. Different inspection well depths had no significant impact on the peak explosion pressure or temperature but had a substantial effect on the propagation velocity of the explosion flame at the bottom of the well. Compared with a methane (CH4) explosion at a concentration of 6%, the peak explosion pressure, peak explosion temperature, and flame propagation velocity of a CH4 and oil‐gas mixture at a concentration ratio of 6% : 1% were found to be significantly higher. With increasing oil‐gas concentrations (2%, 4%, and 6%), the peak pressure, temperature, and flame propagation velocity continued to decrease. The findings of this study can help prevent explosion accidents in municipal sewage pipelines and provide a reference to support the establishment of related standards.
Highlights
As an essential part of urban public infrastructure, municipal sewage pipelines are highly vulnerable to gas explosion accidents leading to heavy casualties and property losses because flammable gases often accumulate due to the massive scale of the sewer system, its numerous branches, and its airtightness
A volatile oil-gas mixture accumulated within a closed municipal sewage conduit and exploded because of a spark during the Sinopec Donghuang underground oil pipeline leakage and explosion accident in Qingdao, Shandong Province, China, on November 22, 2013. is accident resulted in 62 deaths, 136 injuries, and a direct economic loss of nearly RMB 752 million
Considering that a large number of structures with complex geometry, such as L and T shapes, exist within sewage pipelines, a comparative experiment was conducted by Li et al [1] to study the influence of T-shaped branch pipes on the overpressure and flame propagation velocity of an oil-gas explosion within the airtight pipeline. e results indicated that the maximum overpressure of a T-shaped pipe increased with the distance of ignition, and oscillation was observed
Summary
As an essential part of urban public infrastructure, municipal sewage pipelines are highly vulnerable to gas explosion accidents leading to heavy casualties and property losses because flammable gases often accumulate due to the massive scale of the sewer system, its numerous branches, and its airtightness. Considering that a large number of structures with complex geometry, such as L and T shapes, exist within sewage pipelines, a comparative experiment was conducted by Li et al [1] to study the influence of T-shaped branch pipes on the overpressure and flame propagation velocity of an oil-gas explosion within the airtight pipeline. Is lack of available research has restricted the identification of the mechanisms of explosion disasters within municipal sewage pipelines and the development of techniques to prevent and control them To this end, the flammable gas explosion properties within a municipal sewage pipeline, including pressure, temperature, and flame propagation velocity, were investigated by considering factors including ignition position, inspection well depths, and gas compositions and concentrations. The flammable gas explosion properties within a municipal sewage pipeline, including pressure, temperature, and flame propagation velocity, were investigated by considering factors including ignition position, inspection well depths, and gas compositions and concentrations. e results provide a reference for the prevention of explosion accidents in municipal sewage pipelines and the development of safety management standards
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