Integral Method Solution of Time-Dependent Strained Diffusion-Reaction Layers with Multistep Kinetics

Multiple coupled chemical reactions occurring within strained diffusion layers are key to a wide range of reactive flow problems. An integral approach is presented here to allow calculations of global properties of such reactive layers for complex multistep chemical kinetics and time-varying strain rates. The infinite-degree-of-freedom partial differential equations (PDEs) governing the dynamics of the species concentration profiles for reactants, intermediates, and products as well as the temperature are projected onto a set of ordinary differential equations having just a few degrees of freedom for the evolution of integral moments of these profiles. The presence of multistep reaction kinetics leads to a set of highly coupled nonlinear moment equations. Numerical solutions are presented for four-step methane-air kinetics coupled with thermal nitric oxide kinetics and are compared with direct solutions of the original PDEs. Some properties and numerical illustrations of key features of the internal layer...