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At the initial stage of injection, the inject flow has not yet broken up and in a range of small atmosphere pressure (16∼500KPa), the tip of the inject flow always forms a shape of mushroom. And the umbrella of the mushroom is always very big and the root of it is always very thin, especially when the atmosphere pressure is relatively low (88KPa, or 100mmHg) (1)(2). These phenomena are not known popularly and the reason of mushroom formation is not clear. In this paper, with MARS (Multi-interfaces Advection and Reconstruction Solver) method (3)(4)(5)for simulating free surface, analysis of inject flow is practiced. The phenomena are reproduced and the reason is cleared that the formation of the mushroom is induced by the momentum exchange between the very high speed fuel flow and the very complex air flow.

The initial breakup process from liquid fuel to spray droplets in the vicinity of the nozzle tip under high-pressure ambience is analyzed for the isothermal diesel spray injected into the optically accessible high-pressure vessel. The spray was observed both by the use of planar laser light and also by using diffused shadow light. The results obtained in the present study are summarized as follows. The initial breakup of the developing diesel spray could be photographed more clearly in the vicinity of the nozzle tip. The initial liquid jet from nozzle hole is divided into two zones; the intact liquid pillar zone and the umbrella-like thin liquid protrusion zone. The breakup happens mainly in the periphery of the thin liquid umbrella protruding from the tip of the intact liquid pillar. The high pressure ambience break-up mechanism can be analyzed from observation of the internal flow of the liquid pillar and it's protrusive umbrella.

Exciplex-based planar fluorescence technique was applied for two-dimensional visualization of the fuel spray including the region close to the nozzle tip. A spray doped with small amount of naphthalene and TMPD was discharged from a diesel nozzle into a pressurized gaseous nitrogen inside the test chamber installed with glass windows. The fuel spray was also allowed to evaporate in high temperature gaseous environments produced by combustion of the homogeneous mixture of methane and air in the test chamber. Photographs of the temporally frozen two dimensional image of the fuel spray were processed using an image analyzer. The image in the longitudinal cross section passing through the center axis of the spray demonstrated that the high density portion of liquid fuel appeared almost periodically downstream and that the axial distance between the neighboring high density portion increased with an increase in the downstream distance.

One method is the pilot injection in order to clear up the urgent subjects imposed on a DI diesel engine for the exhaust emissions without falling its high thermal efficiency. The pilot injection method can be expected to bring forth a shorter ignition delay, a low peak pressure and a low pressure rise, that is, a slow heat release. The possibility to apply the pilot injection to a DI diesel engine is discussed in this paper. The effectiveness of the pilot injection is estimated by the temperature and the heat release rate calculated from the pressure histories in cylinder.

The authors of the present paper report the measured physiological phenomena of a driver falling into the lowered alertness level and they evaluate the effectiveness of vibration stimulus added to a driver in the low alertness level as a means to keep the driver awake. From the survey test for 21 subjects, it was found the awakening whole-body vibration by the addition of which the alertness level of a driver could be heightened effectively, and it existed in the range between the amplitude of 1 to 15 mm and the frequency of 1 to 4 Hz.

In districts of Japan and other Asian countries where roads are not well developed, densely mixed automobile - bicycle traffic on old narrow roads is usual. According to Japanese statistics 1980, the number o£ fatalities in traffic accidents between bicycles and automobiles surpasses 10 percent of the total and certain measures to decrease this count are requested. In the present report, the authors paid attention to automobiles approaching bicycles from behind and passing by. At first, actual traffic states on narrow roads were recorded by VTR and many dangerous scenes were observed. Then simulative experiments were performed as follows; A narrow road was set with various obstacles e.g. power pole on one side. Several types of bicycles were operated there by subjects under various conditions e.g. passing automobile on the other side.