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Gasoline engines employ various mechanisms for improvement of fuel consumption and reduction of exhaust emissions to deal with environmental problems. Direct fuel injection is one such technology. This paper presents a new quasi-dimensional combustion model applicable to direct injection gasoline engine. The Model consists of author's original in-cylinder turbulence and mixture homogeneity sub model suitable for direct fuel injection conditions. Model validation results exhibit good agreement with experimental and 3D CFD data at steady state and transient operating conditions.

Premixed diesel combustion was performed and various characteristics examined with fuel injection timing near top dead center (TDC). A lean and uniform fuel-air mixture was found to during 25° C.A. with a narrow injection angle (27.5° with respect to horizontal), shallow dish combustion chamber, and low cetane number fuel (CN=19). These conditions enabled low NOx combustion in no exhaust gas re-circulation (EGR), despite fuel injection timing around 25° BTDC. Furthermore, HC emissions were lower than with premixed diesel combustion of the early injection type. Because fuel injection timing was near TDC, the volume of the mixture dispersed to a squish area was decreased. This combustion mode was also achieved with a high-cetane fuel (conventional diesel fuel) and high EGR rate conditions. However, in this case, it was difficult to adjust the ignition timing near top dead center. This combustion system also showed good performance in conventional diesel combustion mode.

This paper introduced a very simple method to measure the liquid phase of spray in an optically accessible DI diesel engine. Particular attention was paid to easy usage and maintaining the compression ratio of the real engine. As a result, a less-expensive 4 W argon laser was used as the beam source and an E-10 high-speed camera was used for continuously observing the elastic-scatter liquid phase image. Meanwhile, the compression ratio can be kept as the real engines by this method. Through this method, the effects such as injection pressure, nozzle specification, intake air boost and temperature on liquid phase penetration before ignition were investigated. Reducing nozzle hole diameter decreased the length of the liquid phase. Increasing injection pressure hastened the evolution of liquid phase, while the liquid phase length varied complexly. Increasing intake air boost considerably shortened the liquid phase penetration and ignition delay.