| Using modern laser diagnostic technique to visualize and analyze the spray characteristics of the modern high-pressure diesel injection systems is the main theme of this study. The goal is to provide injection and spray characteristic information of the injection systems to enhance and optimize their applications to future internal combustion engine, meanwhile, to provide experimental data for correlating and validating with related models used in numerical calculation. The injection systems used in the study are Hydraulic Electronic Unit Injector, Electronic Unit Injector, and Common Rail systems. The scope of work includes characterization of high-pressure injection on test rig, macroscopic and microscopic characterization of non-evaporative sprays in pressurized chamber or atmosphere ambient, and direct visualization of spray and combustion processes using Optically Accessible Engine.; The effects of design parameters and operating conditions on injection characteristics, such as injector response time, needle lift, pressure, rate, and quantity have been identified and discussed. The near-field spray behavior is shown to be highly transient and strongly depends on injector design, nozzle configuration, needle lift and oscillation, and injection pressure. Significant hole-to-hole penetration variation and spray cone angle oscillation are observed on the sprays of the CR systems, which is closed related to its needle lift pattern. Increase of charge air density and temperature and application of pilot injection significantly reduce ignition delay and heat release of pre-mixed combustion. With high-pressure injection and swirl air, the ignition and start of combustion most likely occur at the downwind sides of sprays. |
