In opposed-piston, opposed-cylinder (OPOC) two-stroke diesel engines, the relative movement rules of opposed-pistons, combustion chamber components and injector position are different from those of conventional diesel engines. In this study, the combustion and emission characteristics of the OPOC which is equipped with a common-rail injection system are investigated by experimental and numerical simulation. Different split injection strategies involving different pilot injection/fuel mass ratios and injection intervals were compared with a single injection strategy. The numerical simulation was applied to calculate and analyze the effect of split injection strategies on the combustion and emission after validation with the same experimental result (single injection strategy). Results showed that using split injection had a significant beneficial effect on the combustion process, because of the acceleration effect that enhances the air-fuel mixture. Additionally, the temperature of the split injection strategies was higher than that of single strategy, leading to the nitrogen oxides (NO_x) increasing and soot decreasing. In addition, it has been found that the split injection condition with a smaller pilot injection/fuel mass ratio and a medium injection interval performed better than the single injection condition in terms of the thermo-atmosphere utilization and space utilization.

The sensitivity of key structural parameters to the hydraulic response characteristics in an electronic fuel injector is investigated. First, the hydraulic response characteristic is defined in detail (the opening/closing delay and the opening/closing time). Second, the key structural parameters influencing the hydraulic response characteristics are derived. Finally, the importance and effects of key structural parameters on hydraulic response characteristics are examined, by using the design of experiments method and the range analysis. Results show that the fuel inlet passage diameter is the primary influencing factor to the opening delay and closing delay, while the control piston diameter has the dominant effect on opening time and closing time. A small opening delay and a small opening time prefer a little fuel inlet passage diameter and control piston diameter; however, they contribute to a large closing time and closing delay. The fuel outlet passage diameter is the secondary influencing factor in opening delay, but the second factor that affects the opening time is the diameter of needle.