With growing environmental concern, automobile energy consumption has become a key element in the current debate on global warming. Over the last two decades, significant research effort has been directed towards developing advanced engine technologies such as HCCI (Homogeneous Charge Compression Ignition) that not only lower the exhaust emissions from an automobile, but also offers reprieve from conventional gasoline/diesel usage by promising fuel-flexibility. HCCI offers better engine performance and reduced emissions by emulating the best features of both CI (compression-ignition) and SI (spark-ignition) engines. However, accurate and reliable combustion control of an HCCI engine is an inherently challenging task. Many single-zone control-oriented HCCI models reported in literature fail to accurately estimate the peak pressures, ignition timings, and especially cylinder temperatures. Although certain multi-zone models of HCCI engines based on detail chemical kinetics and fluid mechanics have been developed, such models are too complex for the synthesis of fast and reliable control laws. Thus, considerable research effort has been directed in the present work to develop a physics-based two-zone model of a single-cylinder HCCI engine accounting for temperature and concentration inhomogeneities within the cylinder for better prediction of peak pressures, combustion timings, and exhaust temperatures. The results obtained were in consonance with the computationally intensive multi-zone models. The nonlinear model for peak pressure, ignition timing and exhaust temperature was linearized about an operating point to facilitate the development of an effective LQR (linear quadratic regulator). The model inputs include variable valve timings to effectively control peak pressures, exhaust temperatures and ignition timings.
A thermo-kinetic model base study on natural gas HCCI engine response to different initial conditions