Model based Combustion Phase Optimization in SI Engines: Variational Analysis and Spark Advance Determination*

In internal combustion engines, one of the most important factors influencing performance is the combustion phase. In order to optimize the performance, the optimal combustion phase corresponding to the maximum performance indicator should be estimated. In this paper, based on a thermodynamic model of the engine cycle, combustion phase optimization is formulated as two kinds of problems under some different levels of hypotheses. One is a functional optimization problem, which comes from the perspective of variational analysis with hypothesis of adiabatic engine. The other one is a univariate function optimization problem, i.e., spark advance (SA) determination problem, in which the heat release is assumed to satisfy Wiebe function and the heat transfer to chamber walls is considered. Pontryagin’s maximum principle and golden section search method are adopted to deal with these two problems, respectively. Finally, simulations are conducted at a steady condition.