Optimization Methodology of Fuel Injection Timing for Reactivity Controlled Compression Ignition Multi-Fuel Engine

This study presents the methodology of optimization of fuel injection timing for reactivity controlled combustion ignition engine with port fuel injection of n-butanol and direct injection of biodiesel. Injection timing is crucial for compression ignition engine, since it dramatically modifies the ignition delay and proportion of pre-mixed and diffusion combustion, both of which have effect on efficiency and emission. Common rail system offers the possibility to precisely control the fuel injection timing with various algorithms. However, the optimum timing still remains to be found for RCCI engine application. This study includes: 1) a detailed 1-D, multi-zone predictive simulation models for both n-butanol and biodiesel; 2) optimization of fuel injection timing based on simulation. The objective function is a weighted index of brake specific fuel consumption, and emission. Considering computation cost, several variables are regarded as constants, e.g. port fuel injection timing, port fuel injection proportion, and the fuel injecting in one cycle only includes one pulse in port fuel injection and one in direct injection. Both the modeling and optimization in this study is at a constant load and speed. The results of the study are: the optimum injection timing for low specific fuel consumption combined with ultra-low emissions. The model shows the applicability of a multi-zone predictive combustion model with low CPU consumption and robust results across the engine map