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In this study, a new method is proposed to evaluate the amount of adhered fuel when fuel spray impinges on a wall surface, by considering the normal and tangential droplet impact velocities. To verify this method, how the amount of fuel adhering to a flat plate varies with the spray's angle of incidence is examined. Our experimental results show that less fuel adheres to the wall when spray is oriented obliquely. To verify our method, the concentration of the air-fuel mixture and the fuel film thickness formed in an engine intake port model are also examined. By comparing these experimental results with our calculated results, it is shown that the proposed method can evaluate the behavior of adhered fuel, which conventional methods cannot evaluate.

Spray guided DISI, a next-generation DISI system, is now under development as a gasoline engine which will contribute to improving fuel consumption. The authors have carried out a study to improve fuel consumption and exhaust emissions resulting from a spray guided DISI system with a center injection structure, which is being developed as a system with superior combustion stability. The primary issue for the center injection structure is to reduce changes in the fuel spray characteristics resulting from carbon deposits near the injector nozzle holes. The secondary issue for this structure is to improve the mixture formation.

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.

A Spray Guided DISI (Direct Injection Spark Ignition) is being proposed as a next-generation DISI and is expected to reduce the fuel consumption and the emissions than a Wall Guided DISI that is currently in the mainstream. With the aim of developing a Spray Guided DISI, the evaluation technologies for the spray behavior and the combustion characteristics in a single cylinder transparent engine, the measurement technologies for the mixture formation by LIEF (Laser Induced Exciplex Fluorescence) method and using a Fast Response FID (Flame Ionization Detector), and the analysis technologies for the spray behavior and the mixture formation with CFD (Computational Fluid Dynamics) technology were established. Based on these evaluation techniques, the behavior of spray and mixture formation by a Swirl Injector and a Multi Hole Injector were evaluated.

In a gasoline-direct injection (DI) engine, the formation of the air-fuel mixture, which is governed by the fuel spray geometry, the air motion, and the interaction among the spray, air motion, and wall, directly influences the engine performance. The fuel injected into the cylinder involves air and evaporates to form the air-fuel mixture. The mixture is forced near a spark plug by the spray penetration, air motion, and/or wall reflection. In this paper, we investigated the spray wall impingement and the interaction between the spray, air motion, and wall using an experiment and a numerical simulation. A high-pressure swirl injector simulation model was developed and applied to calculate the spray characteristics and spray wall impingement. The simulation results of the spray shapes under atmospheric and pressurized ambient pressure agreed with the experimental results.