(412e) Mathematical Modeling of Gasoline Combustion in a Spark Ignited Internal Combustion Engine

A fundamentals based low-dimensional model for the in-cylinder combustion of gasoline in a spark ignited internal combustion engine is developed. The low-dimensional model is obtained by reducing the detailed 3-dimensional convection-diffusion-reaction (CDR) model using Lyapunov averaging technique. The reduced order model thus obtained captures the relevant physics and chemistry occurring at different length and time scale of the system and at the same time is efficient enough for parametric studies and real-time implementation. The model is based on two dimensionless mixing times that capture the fuel and air mixing limitations. The first mixing time captures the reactant diffusional limitations inside the cylinder, while the second one accounts for the mixing limitations caused by the reactant input and exit stream distribution. Gasoline is modeled as a multi-hydrocarbon lump with fast and slow burn components and has been shown to capture the key trends correctly. Global reaction kinetics available in the literature is used to model the combustion. For a given fuel inlet conditions, the model predicts exhaust composition of regulated gases (total unburned HCs, CO and NOx) as well as computes the in-cylinder pressure and temperature of the combustion chamber. The model is validated with available experimental results in literature for the range of operating conditions like change in fuel composition (gasoline and ethanol blending), air/fuel ratio, spark timing, speed and engine load.