Research on the evolution and venting characteristics of gasoline–air mixture explosions in confined pipeline trench spaces

In recent years, international energy cooperation has become more extensive, and the safe and reliable transportation of oil and gas resources has become increasingly important. However, storage and transportation sites can have confined spaces in engineering practice, which can lead to safety problems. There is a risk of gasoline–air mixture explosions in confined spaces such as pump rooms, valve operation rooms, and inspection wells, particularly in Class B and Class C pipeline trench areas that utilize non-sand-filled trenches or where the local depth exceeds 2.0 m. These locations are equipped with doors, manholes, or ventilation openings for personnel access within oil storage zones. To investigate the combustion characteristics of gasoline–air mixture explosions in such confined spaces, experimental research was conducted on a simulation platform (L/D = 15, V = 0.015 m3). The findings reveal the following: (1) the most hazardous initial gasoline–air mixture volume fraction for ignition at the upper ignition point is 1.7%; (2) the morphology of the internal flame evolves through four distinct stages, with the post-explosion flame shapes resembling “brush-like” and “mushroom cloud” formations; (3) low YCH = 1.1%, medium YCH = 1.7%, and high YCH = 2.3% volume fractions of hydrocarbons were selected to analyze the progression of the explosion development process; (4) the external overpressure distribution during venting explosions, with varying initial gasoline–air mixture volume fractions, conforms to the function y = ae−bx as the distance L varies, with venting pressure waves exhibiting a trend of exponential decay.