Phenomenological Combustion Models

Abstract

For the calculation of engine combustion processes, various model categories can be employed, which are quite diverse in their level of detail, but also in their calculation time requirements, see Stiesch (2003). Calculation models are customarily designated as phenomenological models that can calculate combustion and pollutant formation contingent upon important physical and chemical phenomena like spray dispersion, mixture formation, ignition, reaction kinetics, etc. Because a spatial subdivision of the combustion space into zones of varying temperature and composition is often necessary, the models are also referred to as quasidimensional models. Phenomenological (or quasidimensional) models differ on the one hand from zero-dimensional (or simplified thermodynamic) models, which simplify the combustion chamber as being ideally mixed at every point in time and are based on empirical approaches for the combustion rate. On the other hand, phenomenological combustion models differ from the CFD codes (CFD = computational fluid dynamics, see Chap. 12 ff.), in that we consciously do without an explicit solution of the turbulent three-dimensional flow field, which reduce the calculation time considerably (Fig. 11.1). The calculation time for one engine revolution lies in the region of seconds in phenomenological models, while in CFD codes it takes hours (Fig. 11.2).