Thermodynamic based modeling for nonlinear control of combustion phasing in HCCI engines

Low temperature combustion modes, such as Homogeneous Charge Compression Ignition (HCCI), represent a promising means to increase the efficiency and significantly reduce the emissions of internal combustion engines. Implementation and control are difficult, however, due to the lack of an external combustion trigger. This thesis outlines a nonlinear control-oriented model of a single cylinder HCCI engine, which is physically based on a five state thermodynamic cycle. This model is aimed at capturing the behavior of an engine which utilizes fully vaporized gasoline-type fuels, exhaust gas recirculation and intake air heating in order to achieve HCCI operation. The onset of combustion, which is vital for control, is modeled using an Arrhenius Reaction Rate expression which relates the combustion timing to both charge dilution and temperature. To account for a finite HCCI combustion event, the point of constant volume combustion is shifted for SOC to a point of high energy release based on experimental heat release data. The model is validated against experimental data form a single cylinder CI engine operating under HCCI conditions at two different fueling rates. Parameters relevant to control such as combustion timing agree very well with the experiment at both operating conditions. The extension of the model to other fuels is also investigated via the Octane Index (OI) of several different gasoline-type fuels. Since this nonlinear model is developed from a controls perspective, both the output and state update equations are formulated such that they are functions of only the control inputs and state variables, therefore making them directly applicable to state space methods for control. The result is a discrete-time nonlinear control model which provides a platform for developing and validating various nonlinear control strategies --Abstract, page iv