Laminar flame calculations using simplified chemical kinetics based on intrinsic low-dimensional manifolds

Abstract

During the last 10 years, a great success has been achieved in the field of detailed mathematical modeling of combustion processes. However, most detailed models are restricted to the simulation of simple one-dimensional laminar flames and the extension of detailed kinetic models to general reacting flows of practical importance (e.g., turbulent flow in internal combustion engines) is computationally prohibitive. Thus, simplified kinetic models have to be used. Recently, we presented a mathematical model, the method of intrinsic low-dimensional manifolds (ILDM), which reduces the chemical kinetics automatically. The only inputs to the procedure are the detailed reaction mechanism and the desired number of degrees of freedom. The reduction of the kinetics is performed using the assumption that the fastest timescales are in local equilibrium and can be decoupled. This paper discusses the implementation of the method in reacting flow calculations. The procedure is developed for general three-dimensional reacting flows, which are governed by the system of conservation equations, and the coupling of the reduced chemical kinetics with molecular transport processes and convection is discussed. Then, the mathematical model is verified by sample calculations of structures of laminar premixed flat flames, which provide a simple, but realistic test case. Examples, which verify the approach, are shown for H2−O2 and syngas-air flames. Even for these simple examples, a considerable speedup of the computations is observed. However, the method can also be used for other fuels and, thus, will allow an efficient treatment of combustion systems of practical importance.