Assessing the influence of real releases on explosions : motivation and previous work

Gas explosions represent a severe hazard in industry - a majority of the 100 largest property losses in the hydrocarbon industries from 1974 to 2017 involved fires and explosions (Marsh, 2018). Most accidental gas explosions entail a chain of events that include loss of containment of gaseous or liquid fuel, dispersion and mixing to form a flammable fuel-air cloud, ignition, turbulent combustion, local pressure build-up and propagation of blast waves in the surroundings. The positive feedback between expansion of combustion products, generation of turbulence in the unreacted mixture, especially in wakes behind obstacles, and enhanced rate of turbulent combustion causes flame acceleration in congested geometries (Bjerketvedt et al., 1997). However, it is also clear that pre-ignition turbulence and various instability phenomena can play a significant role in explosion scenarios, and that deflagrations may undergo transition to detonations (DDT) under certain conditions (Moen, 1993). Safe design of industrial facilities and optimal implementation of risk-reducing measures require validated models that can simulate the consequences of gas explosions in complex geometries with sufficient accuracy (Skjold et al., 2018). The research activities in the project Assessing the Influence of Real Releases on Explosions (AIRRE) include a unique series of large-scale explosion experiments with ignited high-momentum jet releases directed into congested geometries. The project also includes validation of the computational fluid dynamics (CFD) code FLACS and systematic studies to validate and improve the current state-of-the-art methodologies for quantitative risk assessment (QRA). As such, the primary objective for the AIRRE project is to gain improved understanding of the effect realistic releases and turbulent flow conditions have on the course and consequences of accidental gas explosions in the petroleum industry, and thereby develop and commercialize technology and methodology that can facilitate safe and optimal design of process facilities. This paper outlines the motivation for the AIRRE project and summarises results from previous work on ignited jet releases