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A new liquid-liquid injection technique with a rigid swirling water flow and a single shot photograph was developed to make observation of a fuel-air mixing process, and then to understand its characteristic quantitatively. In this technique, a liquid fuel was injected into an other liquid to simulate the process of diffusion in a piston cavity of an actual engine. This experiment has been made employing four different configurations of plastic piston cavities; dish, troidal, bowl and square type. These cavities were filled with water and rotated to generate the rigid swirling water flow. Observations from the bottom and side view indicated that the mixing process in the square configuration markedly depends on the orientation of the spray, due to both effects of the swirl and the impingement of the spray on the side wall. The technique is a potential to visually understand the mixing process.

The application of emulsified fuel for diesel engines is expected to reduce NOx and soot simultaneously. The purpose of this study is to clarify the influence of water content in emulsified fuel and fuel injection timing on diesel engine performance. The engine performance of emulsified fuel was compared with the water injection method. In the water injection test, water was injected to intake manifold and diesel fuel was directly injected into combustion chamber. Two emulsified fuels of which mixing ratio of water and emulsifier to diesel fuel were 15 and 30 vol.% were tested. Engine performance and exhaust gas emission of water injection method were almost similar to those of diesel fuel, so that water presented in combustion chamber had almost no influence on engine performance. Therefore, it can be considered that the micro explosion of fuel droplet enhanced the fuel atomization and mixing of fuel and air.

The purpose of this study is to explore an effect of cooled-EGR on the diesel engine performance fueled with coconut-oil methyl ester (CME). The exhaust gas was cooled by the water at room temperature and was fed to the intake manifold, and the EGR rate was changed from 0 % to 30 % at every 10 %. The engine performances were measured at several EGR rates, fuel injection pressures and timings. Test fuels were CME and commercial diesel fuel. In the case of high EGR rate at which the compression ignition was deteriorated, the ignition timing of CME was always earlier than that of diesel fuel, therefore CME had good ignitability as compared with diesel fuel under EGR application. When the fuel injection pressure was increased at high EGR rate, the ignition delay was improved by the fuel atomization and air-fuel mixing effect.