Investigation into mechanisms of deflagration-to-detonation using Direct Numerical Simulations

Abstract

Detonation, a combustion phenomenon is a supersonic combustion wave which plays critical role in the theory and application of combustion. This work presents numerical investigation into indirect initiation of detonation using direct numerical simulations (DNS). The Adaptive Mesh Refinement in object-oriented C++ (AMROC) tool for parallel computations is applied in DNS. The combustion reactions take place in a shock tube and an enclosure with a tube respectively and are controlled by detailed chemical kinetics. The database produced by DNS accurately simulates the process of transition of deflagration to detonation (DDT), and investigates the influence of overpressure and kinetics on flame propagations during combustion processes. The numerical simulations showed the influence of pressure and kinetics to the transition of slow and fast flames and DDT during flame propagations. When the reaction rate is fast, DDT is achieved, but when slow, DDT will not occur and therefore, there will be no detonation and consequently no strong explosion. Exploring the influence of free radical H on flame propagation showed that the concentration of the reacting species decreased with flame speed increase for each propagation. Hence, the heat generated was very fast with a greater chance of DDT being triggered because flame speed increased.