A Numerical Study on the Optimum Fuel Split-Injection Scheme Configuration in a Constant-Volume Chamber

The effects of diesel fuel split-injection on the fuel-air ratio and the gas velocity distribution inside the combustion chamber are numerically investigated using a modified KIVA-3V code that incorporates an Enhanced Taylor Analogy Breakup (ETAB) model into the calculation of spray droplet breakup. The second injection in the split-injection scheme can generate a sudden increase in the flammable mixture area inside the chamber. Among the schemes evaluated, the split-injection configuration in which 75% of the fuel mass is injected during the first injection and the remaining fuel mass is injected after a 1.0-ms dwell is preferred as the optimum configuration with respect to particulate emission reduction. The configuration tends to produce the widest flammable area inside the chamber during the mixing-controlled combustion phase. The dwell duration in split-injection schemes does not have a linear correlation with the area of the flammable mixture. The gas velocity distributions do not change significantly when the fuel injection mass ratio and dwell duration are varied.