Vapour cloud explosion, a threat in refineries and chemical plant Some basics, some critical points, some trends, some wishes

A brief historical overview will be given how the threat of vapour cloud explosion manifested itself in the late sixties and some early investigations will be sketched. Various types of gas and aerosol explosions can be distinguished. To predict the theoretical maximum explosion potential is easy but a prediction of what is a realistic blast menace in practice turned out to be difficult. A brief survey will be given of the 15 -20 years of European research on flame acceleration and blast output of vapour cloud. Also the rather simple but for practical purposes quite adequate approach of the multi-energy method for predicting the blast given a maximum release of fuel, will be described. Such prediction will be needed for the purpose of calculating safe distance to vulnerable structures, control room and office buildings. The development of computational fluid dynamics codes for more refined prediction has started also some decennia ago, but although with the development of computer power the codes output becomes more colourful the predictive reliability still leaves something to be desired. The reasons for this will be explained. Flame propagation with all its possible instabilities is a science in itself and it was recently still possible to find a new mechanism of sudden enhancement of the energy release rate. So, quite a few more years of research will be required before a full quantitative grip on propagation of a flame in a cloud, the interaction with the build-up environment via turbulence generation in partial confinement, and the effects of pressure waves can be obtained.