Abstract: Based on the working model of a diesel engine, the influences of two Miller cycle strategies, Early Intake Valve Closure (EIVC) and Late Intake Valve Closure (LIVC) on the combustion and emissions of diesel engine were analyzed by 1-Dimensional simulation. Then, the working condition of each Miller cycle strategy on the engine under the rated speed was optimized through the adjust of the valve timing, the boost pressure and the injection timing. It was found that both delaying and advancing the closure timing of the intake valve can decrease the pressure and temperature during compression stroke, prolonging the ignition delay. However, due to the decrease of the working media inside the cylinder, the average in-cylinder temperature and soot emission increase, which can be alleviated by raising the boost pressure and the resulting compensation of the intake air loss. The study also found that together with increasing boost pressure and delaying injection timing, both EIVC and LIVC can reduce NO_x and soot emission simultaneously. The simulation results show that while keeping the peak firing pressure the same as the original engine, M-50 together with constant peak firing pressure boosting and a 6 °CA injection delay can decrease the Fuel Consumption (FC) by 1.21%, and NO_x emission by 22%, and soot emission by 58.1%, while M100 together with constant peak firing pressure boosting and a 4 °CA injection delay can reduce the FC by 1.56%, and NO_x emission by 12.96%, and soot emission by 54.75%.

Key words: internal-combustion engine engineering, Miller cycle, diesel engine, 1-Dimensional simulation, emission