Numerical Simulation of Detonation Waves

Abstract

A one dimensional numerical study on the build-up and propagation of planar detonation waves in H2 and Air combustibles mixtures is presented. To describe the motion of a traveling detonation the unsteady Euler equations coupled with source terms to account for a finite rate chemical activity, are used. The algorithm for computing the numerical hyperbolic fluxes is based on the Harten-Yee TVD scheme. Since the source terms lead to stiff differential equations, an implicit treatement of these terms is implemented. The computer solver works with 13 chemical species and 33 different one step reactions of a H2 - O2 - N2 combustion mechanism. The detonation process is initiated via the energy provided by an igniter made of hot and high pressure helium (the He is considered an inert species). The helium remains confined within a small region (no greater than a few centimeters), while the detonation continues until much bigger distances determined only by computing times. It is shown that for each equivalence ratio of the combustible mixture, the detonation can only be triggered if the igniter energy
deposition is equal or exceeds a computed minimum value. When the igniter energy deposition is less than this minimum, the combustion zone decouples from the blast (or shock) wave. This shock, as it travels downstream becomes weaker and no longer induces chemical reactions across it, however, a chemical activity still remains being now started by a reaction front located at some distance from the leading wave.