Modeling and control of SI and SI-HCCI hybrid combustion engines

As a special combustion mode of internal combustion (IC) engines, homogeneous charge compression ignition (HCCI) combustion has the potential to meet the increasingly stringent emissions regulations with improved fuel economy. In order to take advantage of this combustion mode, the traditional spark ignition (SI) engine needs to operate in both SI and HCCI modes, and the combustion mode transition between the SI and HCCI combustions is inevitable. It is fairly challenging to operate the engine in the two distinct combustion modes, and it is even more difficult to have smooth combustion mode transition between the two modes due to the distinct engine operational parameters over the two combustion modes and the cycle-to-cycle residual gas dynamics. In this research, the modeling and control of the combustion mode transition problem were studied for a multi-cylinder engine with dual-stage valve lift and electrical variable valve timing (VVT) systems.;In order to describe engine continuous time and event-based dynamics a mixed time-based and crank-based engine model was developed. The continuous dynamics of engine air-handling system and crankshaft were modeled by traditional time-based mean value models; and the engine combustion process was modeled as a function of crank angle (crank-based) using the two-zone combustion modeling approach. The developed combustion model is capable of simulating the SI, HCCI, and SI-HCCI hybrid combustion modes. This unique modeling approach made it possible for the engine model to be simulated in real-time in a dSPACE based hardware-in-the-loop (HIL) system, due to its low computational throughput. The developed engine model was calibrated and validated using the simulation results from the corresponding one-dimensional GT-Power engine model in the dSPACE based HIL engine simulation environment.;Through HIL simulations using the developed engine model, a multistep SI to HCCI combustion mode transition strategy was incrementally developed. It takes several engine cycles (typically five) to complete the combustion mode transition. During the combustion mode transition, a model based linear quadratic (LQ) engine MAP (intake manifold absolute pressure) tracking controller was used to maintain the air-to-fuel ratio in the desired range by regulating the engine throttle; the DI (direct injection) fuel quantity of individual cylinder was controlled via iterative learning control (ILC); and spark ignitions were maintained to enable the SI-HCCI hybrid combustions; The other engine parameters, such as the intake/exhaust valve timing and lift, external EGR (exhaust gas recirculation) valve opening were controlled in an open loop. The entire control strategy was validated in the developed HIL simulation environment. The simulation results demonstrated the effectiveness of the proposed control strategy under both constant and transient engine operating conditions. It can be concluded that smooth combustion mode transition is achievable for IC engines using dual-stage valve lift and electrical VVT systems as the valve actuation systems.