A Study of Center and Side Injection in Spray Guided DISI Concept

In-cylinder direct fuel injection technology is effective in improving fuel consumption and reducing emissions for gasoline engines. A number of systems based on this technology are currently being developed, and one such system, the wall guided DISI, has already been put to commercial use. As the development of the DISI engines pushes forward, spray guided DISI has been proposed as a new possibility which can offer further improvements. The authors of this paper recognize the advantages of spray guided DISI in terms of fuel consumption and emissions reduction, and have conducted research for the purpose of creating an injector that is optimized for spray guided combustion. A spray guided DISI engine requires a fuel injection system that is little affected by changes in airflow, pressure, and temperature inside the cylinder. This requirement is satisfied by the recently-developed multiple hole injector.

This paper describes the combustion characteristics of both a side injection system and a center injection system using this developed injector, and compares the combustion characteristics of the two systems. The comparative study of the two systems shows that the center injection system, when combined with an incylinder swirl airflow system, provides better combustion stability than the side injection system. However, because in a center injection system the fuel injection point is located near to the ignition point, rapid formation of the mixture is essential. This study identified accelerated fuel vaporization and more efficient air-entrainment as key issues for improving the mixture formation.