Quantitative Analysis of Mixture Preparation Processes in New Direct-Injection Spark Ignition Engines

Visualization plays an effective role in the establishment of a new combustion concept by helping to find the optimal results quickly among many different parameters and contributing to a shorter development period. Laser-induced fluorescence, Raman scattering and infrared absorption were used to measure the air/fuel ratio quantitatively in a third-generation direct-injection gasoline (DIG) engine with a spray-guided mixture formation process and comparisons were made with the mixture formation concepts of the first- and second-generation DIG engines. The optimum combination of fuel spray, gas flow and combustion chamber configuration was found to be different for the three generations of DIG engines. The characteristics of the stable combustion region for obtaining higher thermal efficiency and cleaner exhaust emissions differed among the three mixture formation concepts.