Effects of concentration gradient on pulsating and cellular detonations

In the field of explosion accidents and the combustion chamber of propulsion systems, gaseous mixtures are more likely to be highly non-uniform and a detonation usually propagates in a non-homogeneous medium. In this paper, one-dimensional (1D) pulsating detonations propagating in non-homogeneous medium with concentration gradient are studied by direct numerical simulation with a detailed chemistry. It is found that a periodically pulsating detonation can adjust to adapt to the environment with concentration gradient. The superficial concentration gradient can improve survivability of 1D detonation under highly unstable case, widening detonability limit corresponding to equivalence ratio; while the steep concentration gradient will quickly extinguish the detonation. The extend of detonability limit led by the inhomogeneity is reinforced by the presence of transverse wave in 2D detonations. The 2D detonation in the gradient has better viability compared with the 1D due to the coupling interaction of leading shock and transverse wave with the gradient and the transportation of H₂ and H along the gradient. This study also demonstrates that the simulations of detonations in the gradient requires detailed chemical mechanism.