Since computer performance has drastically increased, numerical simulation is a powerful means for simulation of fluid flow. However, combustion simulation is still challenging and it is difficult to simulate combustion field with both turbulence and detailed chemistry, because it takes much time to solve 2D or 3D governing equations such as conservation equations of mass and momentum. Recently, Lattice Gas Automata (LGA) has been proposed as an alternative approach for simulating fluids. It describes the fluid at more microscopic level by assuming that it is composed by mesoscopic particles. The space and time are all discrete, and the physical quantities take only a finite set of values. Macroscopic quantities such as density and velocity are determined by the collective behavior of particles. The scheme of this discrete model is simple and easy for parallel computing. In this work, we simulate combustion filed by LGA, coupled with a Laminar Flamelet model to determine the temperature and concentration of the mixture by fast-chemistry assumption. Two particles of fuel and oxidizer are used for simulating diffusion combustion. We focus on the so-called counter flow diffusion flame. Some results including flow, temperature, and concentration fields are shown.
The effects of adopted reaction mechanism on Nitrogen Oxide (NO) formation processes in methane-air counterflow diffusion and double flames were studied numerically. Miller and Bowman (M&B) kinetics had widely been used in the past to predict NO formation in methane-air flames. GRI-Mech. 2.11 (GRI), on the other hand, have been more popular recently in the studies of methane-air flames. The objective of present study is to make clear the difference of NO emission characteristics predicted by these two kinetics, and then to find out the cause of observed difference. The analytical methods applied were those developed by the present authors. They are 1. Separation of contribution of respective four NO formation mechanisms, 2. Quantitative reaction pass diagram, and 3. Sensitivity analysis of each elementally reaction. It was found that GRI predicts more NO production than M&B through Fenimore mechanism, whereas the production behavior through thermal mechanism remains the same for the both kinetics. The increase is partly because that in GRI a new formation reaction NNH + O ⇔ NH + NO is included, and the contribution of this reaction is appreciable. Another reason is that the rate constants of HCNO + H ⇔ HCN + OH are smaller and the contribution of NO destruction route is smaller in GRI.