Adaptive Combustion Control to Improve Diesel HCCI Cycle Fuel Efficiency

Previous work indicates that the lowered combustion temperature in diesel engines is capable of reducing nitrogen oxides and soot simultaneously, which can be implemented by the heavy use of exhaust gas recirculation or the homogeneous charge compression ignition (HCCI) type of combustion. However, the fuel efficiency of the low temperature combustion cycles is commonly compromised with high levels of hydrocarbon and carbon monoxide emissions. Additionally, 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. Adaptive control strategies are applied to precisely navigate and stabilize the engine cycles and to better phase and complete the combustion process. The impact of heat release phasing, duration, shaping, and splitting on the thermal efficiency has also been analyzed with zero-dimensional engine cycle simulations. The correlations between the cylinder pressure and the heat release curves have been characterized to facilitate model based control. The empirical set-up and cases of applications are provided.