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In a direct injection diesel engine, liquid fuel was injected through a multi-hole injection nozzle to a combustion cavity. The spray impingement on the cavity wall made the quick mixing of sprayed fuel and air. Then the spray impingement process was considered as the key process of the mixture formation, and this process was widely investigated. Since the cavity had too small space for free movement of plural sprays injected by a multi-hole injection nozzle, sprays after impingement were interacted together on the cavity wall. This movement was generally recognized but the detail behavior was not yet clarified. In this study, single shot diesel spray injected into a high-pressure test vessel, in which the impingement plate was mounted, was used to investigate the above movement.

In a direct injection diesel engine, fuel spray was auto-ignited by an elevated temperature and pressure atmosphere in a combustion chamber. Since an ignition might appear in which a suitable mixture for exothermic reaction was prepared and flame might be developing to a combustible mixture, a settlement of ignition in time and space could control the entire combustion. The ignition position was usually investigated with photometric observations such as high-speed video systems. However plane observations could not inform the exact position of the ignition because spray had the 3D structure. In this paper, a new trial for the measurement of the ignition position was reported. A single shot diesel spray injected into a test chamber was ignited by elevated temperature and pressure atmosphere in the chamber. The chamber had an impingement plate so as to measure an ignition delay of a wall impingement diesel spray.

A six-stroke DI diesel engine proposed by the authors had second compression and combustion processes which were added on a conventional four-stroke diesel engine. This engine had the first and second power strokes before the exhaust stroke. Numerical predictions and experiments previously carried out had shown that this six-stroke diesel engine could reduce NO exhaust emission. Further, the ignition delay of the second combustion process could be shortened by a high temperature effect in the second compression stroke. This advantage of short ignition delay could be utilized for an ignition improvement of a fuel with low cetane number. In the engine system reported here, a conventional diesel fuel was supplied as the fuel of first combustion process, and in the second combustion process, methanol was supplied.

Multi-stage injection diesel spray was investigated to understand the internal flow of a diesel spray. This multi-stage spray consisted of two sprays (we called them the first and second sprays) which were formed by a split injection with a short dwell time. In this paper, we discussed the dynamic behavior of a two-stage injection diesel spray. Especially, we focused on the characteristics of internal velocity and the decay of spray density fluctuation. When the injection rate of a conventional spray increased within an injection period, a spray tip of initially injected fuel was caught up and overtaken by the spray of a following injection. Then the internal structure of a conventional spray greatly depended on the internal spray velocity controlled by the injection rate. Since the second spray penetrated into the first spray, the spray tip motion of the second spray could be considered to be similar to the behavior of an internal spray motion in a conventional spray.

The behavior of diesel spray impinging on an inclined wall was experimentally investigated in a pressurized vessel. To clarify the wall effect on a diesel spray, a relative angle of the inclined wall to a spray axis was varied. Spray penetration along the wall was observed optically and it was compared with that of a free spray. To evaluate various spray motion quantitatively, a spray path penetration which described a development of a spray tip along the wall was newly introduced. To observe an internal structure of the spray, it was visualized by a YAG laser sheet light and its tomographic image was captured on a film. The photo-image on a film was taken into an image analyzing computer using a high resolved image scanner. A high density zone in the tomographic image was extracted to clarify the internal structure of an impinging spray. The main parameter of the relative position of the wall was its inclined angle which was defined as the angle between the spray axis and wall.

In this paper, a new concept of an attitude control of a diesel spray was proposed. The Coanda effect known in the fields of the fluidics was applied to control a penetrating direction of a diesel spray injected into a combustion chamber of a D.I. diesel engine. In general, a jet moving along a wall was deviated by the Coanda effect. So if the shape of a cavity crown of the combustion chamber would be suitably designed and a diesel spray behavior would be similar to a gaseous jet, the spray might penetrate along the cavity wall. Furthermore, the switching effect of the penetrating direction might appear with a piston movement. To establish this method for an attitude control of a diesel spray, behavior of a diesel spray that was affected by a fixed interference plate located near the spray axis was experimentally investigated.

In this report, a new six-stroke diesel engine is proposed and the thermodynamic performances of this engine are numerically and experimentally analyzed. Since the six-stroke diesel engine introduced here has two combustion processes in one cycle, it offers new methods of combustion control which can't be attained in an ordinary four-stroke diesel engine. In the analysis, we use a simple single zone thermodynamic model with considering the Wiebe's function for heat release rate and the Woschni's equation for heat transfer coefficient. As a results, it was confirmed when the heat release of 1st combustion stroke and 2nd combustion stroke were equivalent, the maximum in-cylinder gas temperature was the lowest, and further it was lower than that of the four stroke diesel engine.