Abstract
Gas explosions in homogeneous reactive mixtures have been widely studied both experimentally and numerically. However, in practice and industrial applications, combustible mixtures are usually inhomogeneous and subject to vertical concentration gradients. Limited studies have been conducted in such context which resulted in limited understanding of the explosion characteristics in such situations. The present numerical investigation aims to study the dynamics of Deflagration to Detonation Transition (DDT) in inhomogeneous hydrogen/air mixtures and examine the effects of obstacle blockage ratio in DDT. VCEFoam, a reactive density-based solver recently assembled by the authors within the frame of OpenFOAM CFD toolbox has been used. VCEFoam uses the Harten–Lax–van Leer–Contact (HLLC) scheme fr the convective fluxes contribution and shock capturing. The solver has been verified by comparing its predictions with the analytical solutions of two classical test cases. For validation, the experimental data of Boeck et al. (1) is used. The experiments were conducted in a rectangular channel the three different blockage ratios and hydrogen concentrations. Comparison is presented between the predicted and measured flame tip velocities. The shaded contours of the predicted temperature and numerical Schlieren (magnitude of density gradient) will be analysed to examine the effects of the blockage ratio on flame acceleration and DDT.
Highlights
Fire and explosion in combustible mixtures have been widely studied both experimentally and numerically
The present study aims to provide an appropriate numerical method to provide the dynamics of Deflagration to Detonation Transition (DDT) in inhomogeneous hydrogen-air mixtures and examine the effects of obstacle blockage ratio in DDT phenomena
These results demonstrate that the newly assembled VCEFoam can provide accurate shock capturing
Summary
Fire and explosion in combustible mixtures have been widely studied both experimentally and numerically. Most of the gas explosions studies inside tubes have been carried out for industrial safety applications with the aim to describe general mechanisms of flame acceleration (FA) and transition from deflagration to detonation (DDT) [2]. Explosion studies in uniform reactive mixtures have been widely carried out both experimentally and numerically. The large-scale macroscopic DDT includes the process from accelerating deflagration followed by detonation propagation. Thomas [3] studied weak DDT, which was not onset by a strong reflected shock wave He identified the importance of non-isotropic and non-equilibrium turbulence to accelerate a deflagration and some hot spots which generate transverse waves, which merged to strong pressure waves capable of forming the required shock interaction complex known as the detonation
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