Preliminary empirical and modeling analyses for model based diesel engine control

Previous work indicates that low temperature combustion (LTC) modes, including homogeneous charge compression ignition (HCCI) cycles, are capable of reducing nitrogen oxides and soot simultaneously in diesel engines. However, such combustion modes are less robust than the conventional diesel combustion and have a narrower range of stable engine operation. In addition, in cases of diesel HCCI cycles, the combustion process may even occur before the piston completes the compression stroke, which may cause excessive efficiency reduction and combustion roughness. To improve the diesel low temperature combustion engine performance, preliminary analyses have been made to identify the major parameters that affect engine thermal efficiency. The impact of heat release phasing, duration, shaping, and splitting on the thermal efficiency has been analyzed with zero-dimensional (zero-D) engine cycle simulations. The correlations between the cylinder pressure and the heat release curves have been characterized to facilitate model based control. Additionally, independent and high precision controls on the rate of exhaust gas recirculation (EGR) flow and the fuel injection pressure of the common-rail system have been implemented and tested in this research. A variety of algorithms have been proposed and programmed to improve the response and precision of the EGR valve and the rail pressure in both manual and automatic modes. The present work targets to develop cylinder pressure based adaptive fuel-injection control strategies that will be used to stabilize the engine operation during the low-temperature combustion modes.