Takuo Yoshizaki

Imaging of droplets and vapor distributions in a Diesel fuel spray by means of a laser absorption–scattering technique

The droplets and vapor distributions in a fuel spray were imaged by a dual-wavelength laser absorption-scattering technique. 1,3-dimethylnaphthalene, which has physical properties similar to those of Diesel fuel, strongly absorbs the ultraviolet light near the fourth harmonic (266 nm) of a Nd:YAG laser but is nearly transparent to the visible light near the second harmonic (532 nm) of a Nd:YAG laser. Therefore, droplets and vapor distributions in a Diesel spray can be visualized by an imaging system that uses a Nd:YAG laser as the incident light and 1,3-dimethylnaphthalene as the test fuel. For a quantitative application consideration, the absorption coefficients of dimethylnapthalene vapor at different temperatures and pressures were examined with an optical spectrometer. The findings of this study suggest that this imaging technique has great promise for simultaneously obtaining quantitative information of droplet density and vapor concentration in Diesel fuel spray.

Three-Dimensional Spray Distributions in a Direct Injection Diesel Engine

Experiments and modeling of a spray impinged onto a cavity wall of a simulated piston were performed under simulated diesel engine conditons (pressure and density) at an ambient temperature. The diesel fuel was delivered from a Bosch-type injection pump to a single-hole nozzle, the hole being drilled in the same direction as the original five-hole nozzle. The fuel was injected into a high-pressure bomb in which an engine combustion chamber, composed of a piston, a cylinder head and a cylinder liner, was installed. Distributions of the spray impinging on the simulated combustion chamber were observed from various directions while changing some of the experimental parameters, such as combustion chamber shape, nozzle projection and top-clearance. High-speed photography was used in the constant volume bomb to examine the effect of these parameters on the spray distributions. The spray distributions obtained in the simulated combustion chamber are compared to the distributions calculated by a spray model based on a multi-package, spray model 3 refs., 13 figs., 1 tab.

Evaporating spray and flame distributions in the combustion chamber of a direct injection diesel engine

Abstract The characteristics of an evaporating diesel spray and the flame distribution in a combustion chamber of a D.I. diesel engine were investigated by using the laser light technique. The technique used was based on the extinctions of two wavelengths of ultraviolet and visible laser light. The transmitted laser light absorbed and scattered by the vapor, drops, soot and combustion products in the spray flame were separated into two wavelengths and captured. Further, the light radiated from the flame was imaged using the same measuring system by modifying the optical filters and the timing of the camera shutter.

Ignition and Combustion of a Solid-Particle Mixed Fuel Drop in a Microgravity Environment.

Mixing solid particles has been recognized as a effective means of getting highly promoting combustion ability of hydrocarbons, which has been attempted to be used for aviation and space vehicle engines. In this study, ignition and combus-tion characteristics of a solid paritcle mixed fuel drop have been measured under normal gravity and microgravity conditions in order to get a fundamental understanding on com-bustion processes of a solid particle mixed fuel spray. The experiments were conducted in a drop tower, which has a fall of 710 m and a duration of 10 seconds of the microgravi-ty condition. A mixture of magnesium or pure carbon powder and n-Dodecane or n-Hexadecane were used for solid particle mixed fuel which has a 40‰ mixing ratio. Comparison of the experimental results between under the microgravity condition and under the normal gravity condition clarifies differences in combustion characteristics between the two. The minimum ignition temperature of the fuel droplet under micro-gravity was lower than that of under normal gravity, and the flame expansion ratio of the carbon slurry under microgravity in high ambient temperatures more than 1000K was larger than that in lower ambient temperatures.