Investigation into the Mechanisms and Consequences of Explosions of Premixed Gaseous Combustibles with Detailed Chemical Kinetics

Abstract

Detonation is a self-sustaining combustion wave with a rapid reaction process and a propagation speed. It is a central topic in combustion and serves a significant role in the theory and the application of combustion. The volatility of petroleum products and crude oil in the downstream and upstream sectors of the oil and gas industry constitutes a high degree of fire explosion risks and disasters thereby leading to losses of over 528 lives, more than 1,289 persons injured, over 1,280 nearby homes burnt, and numerous workshops destroyed, large quantities of barrels of crude oil spilled into the environment and billion dollar projects burnt down. The aim of this project is to explore the effects and influences of chemical kinetics and geometric configurations to the wave behaviours using computational fluid dynamics (CFD) approach. Mathematical models and numerical methods will be employed in solving the problems in this research work. This project report focused on numerical investigation of indirect initiation of detonation using direct numerical simulations (DNS). In this simulation, the chemical combustion reactions are ignited in a shock tube and then the processes of transition of deflagration to detonation (DDT) were explored. The DNS database provides a source to investigate the influences and effects of chemical kinetics of explosions on hydrogen-oxygen and propane oxygen combustion reaction processes were explored. For this work, the CFD programme employed is an Adaptive Mesh Refinement in object-oriented C++ (AMROC) tools which can be executed in parallel processes to obtain an accurate DNS database on the chemical kinetics of the elements.
From the simulation results, the influences, and the effects of chemical kinetics of explosions on hydrogen-oxygen and propane oxygen combustion reaction combustion reactions were investigated; and slow flame (called laminar flow), fast flame, DDT and Detonation data were obtained. When the concentration was low, the reaction rate was very slow, no DDT and no detonation were achieved, but when the concentration was high/large, the reaction rate was very fast, and thus DDT and detonation would be formed and consequently explosion occurred. Exploring the influence of free radical H on flame propagation, it was found that in each case study, as the concentration of the reacting species increases, the flame speed increases for each propagation for certain limited duration. The results showed that as the flame moves through more volume, more fuel is thereby being burnt and so, less free radical, H around that is being burnt.
Moreover, in this research work, the influences and effects of geometric configurations on explosion of hydrogen-oxygen and propane -oxygen mixtures using numerical simulation method were equally investigated. Hence, when vent is created in the tube, DDT will occur and consequently detonation is achieved, and vent explosion took place. Moreover, for closed end tube such as that of case study with one Block, the block constituted an artificial obstacle, hence, FD, DDT, and detonation were formed, and explosion would consequently occur. Therefore, the main significance of this work showed that chemical kinetics and geometric configurations have influences and effects on explosion of hydrogen-oxygen and propane -oxygen reaction mixtures.