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The structure of dense sprays was investigated using 2-D imaging techniques. To investigate the mechanism of atomization, the liquid phase in a non-evaporating spray was visualized by a thin laser sheet formed by a single pulse from a Nd:YAG laser at the distance from 4 to 19 mm from the nozzle orifice with the injection pressure and the surrounding gas density as parameters. A new technique for the visualization of vapor phase in an evaporating spray, the SSI (Silicone particle Scattering Imaging) method, was proposed to investigate the structure of the vapor phase regions of the spray.

Soot concentration is very high in the periphery near the head of an unsteady spray flame which is achieved in a quiescent atmosphere in a rapid compression machine. To reduce soot concentration in this region, it was intended to improve fuel-air mixing by letting the flame impinge on a turbulence-generating plate. Two types of turbulence-generating plates, one donut-type, the other cross-type, were tested. Soot concentration in the flame was imaged using the laser shadow technique. The effect of injection pressure on soot reduction by the flame impingement was also investigated. The overall soot concentration is reduced significantly in the case when the flame impinges on the cross-type turbulence-generating plate at 50 mm (333 nozzle diameters) from the nozzle exit. The flame impingement on the cross-type turbulence-generating plate at 333 nozzle diameters makes soot reduction little dependent on injection pressures.

In this study, the authors show their analytical model of the fuel injection system in a diesel engine, which is constructed to be as accurate but as simple as possible and to have good application in the development of new fuel injection systems. In the first part, the authors initially describe the model assumptions, classification of injection phenomena, and fundamental equations considering the compressibility, inertia and viscocity of hydraulics and the movements of valves and other components to improve the accuracy of the systems. Secondly, regarding the experimental constants and physical properties of the fuel, the authors show the method of selection they used to simplify the analytical model and to get good agreement as a result but without losing physical meanings.

In the past we developed an injection-rate detector, however, it becomes no more applicable to modern high-pressure piezoelectric injection systems having functions of multi-stage injection due to the following problems: High-pressure injection generates shockwaves that induce pressure fluctuation, whose amplitudes of high-frequency components could be not effectively attenuated with a low-pass filter, in the detector. High-pressure injection also causes heterogeneous distribution of temperature in the detector, because the pattern of fuel flow from the injection nozzle to the discharge valve at fuel-discharging process is inappropriate. Accordingly, fuel temperature, which is necessary for identifying bulk modulus of fuel, in the detector could not be precisely obtained, thereby causing an unacceptable level of scattering for determining injection quantity. Hence, we developed a new detector in modifying its constructive design to solve the problems.