Experimental Validation of a Model-Based Water Injection Combustion Control System for On-Board Application
Water Injection (WI) has become a key technology for increasing combustion efficiency in modern GDI turbocharged engines. In fact, the addition of water mitigates significantly the occurrence of knock, reduces exhaust gas temperatures, and opens the possibility to reach optimum heat release phasing even at high load. This work presents the latest development of a model-based WI controller, and its experimental validation on a GDI TC engine. The controller is based on a novel approach that involves an analytic combustion model to define the SA required to reach a combustion phase target, considering injected water mass effects. The model has been expanded to directly consider air-to-fuel ratio variation effects on combustion phasing, and the same controller structure could integrate other variables that influence 50 percent of Mass Fraction Burned angular position (MFB50), such as EGR.