Modeling and experimental study of an HCCI engine for combustion timing control

Homogeneous Charge Compression Ignition (HCCI) is a promising method for combustion engines to provide a substantial reduction in fuel consumption and formation of both nitrogen oxides and soot pollutants in automotive and stationary engines. Control of HCCI combustion timing is essential for the successful integration of the HCCI concept in real applications. This thesis concentrates on control oriented modeling and experimental study of HCCI combustion for control of ignition timing in HCCI engines.

A detailed experimental study of HCCI with over 600 operating points on two different engines is done to characterize the complex relationship among the engine variables, the ignition timing and the exhaust temperature. This leads to identifying regions with distinct patterns of cyclic variation for HCCI ignition timing. In addition, main influential factors on the variations of ignition timing and exhaust temperature in HCCI engines are determined. A dynamic full-cycle physics based Control Oriented Model (COM) is derived from using the experimental data and simulations from an HCCI thermo-kinetic model. The COM is validated with a large number of transient and steady-state experimental points. The validation results show that the COM captures the key HCCI dynamics with a high degree of accuracy for control applications. The COM is computationally efficient and all inputs of the model can be readily measured or estimated on a real engine. This makes the COM simple and fast enough for use as an off-line simulation bed to design and evaluate different strategies for physics-based control of combustion timing in HCCI engines.