Effects of different injection timing on the performance, combustion and emission characteristics of diesel/ethanol/n-butanol blended diesel engine based on multi-objective optimization theory

In this work, a three-dimensional model of an engine cylinder was devolved by the commercial simulation software AVL-Fire. The model was combined with a chemical reaction mechanism containing 377 reactions and 81 species to simulate the in-cylinder combustion. The purpose of this work was to study the effects of different diesel/ethanol/n-butanol blend percentages and injection timings on the combustion and emission characteristics of a diesel engine and to optimize the results with multiple objectives. The results showed that suitable injection timing provided the engine with better combustion and fuel economy. In addition, the advanced injection timing significantly reduced CO and soot emissions but increased NOx emissions. Moreover, the increased percentage of ethanol and n-butanol in the fuel mix reduces cylinder pressure and temperature, and increases fuel consumption. However, it improves the brake thermal efficiency and effectively reduces NOx, CO and soot emissions. Finally, the multi-objective parameter optimization of each parameter was performed by the orthogonal experimental design method in Design-Expert software. The results showed that the optimal match was achieved at a diesel blending rate of 88.49% and an injection timing of 12.43°CA BTDC.