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An experimental study was carried out on visualization of liquid phase temperature distributions in high-pressure diesel sprays impinging on a heated wall. Naphthalene/TMPD-exciplex fluorescence method and pyrene-excimer fluorescence method were utilized for the thermometry. The sprays were injected into a high-pressure and high-temperature gaseous environment. The nozzle hole diameter was 0.100 mm or 0.139 mm. The results showed that cool pockets were formed at the tip and in the impinging part of the sprays. The spray for the nozzle with 0.100 mm hole was heated up faster near the nozzle than for the nozzle with 0.139 mm hole.

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.

An experimental study was made to investigate in-cylinder flow field in a natural gas fueled spark ignition engine and the effects of engine specifications on in-cylinder flow field. The instantaneous two-dimentional flow fields in a single-cylinder visualization engine, which has 75mm bore and 62mm stroke, were measured in various cross sections perpendicular to the cylinder axis by using the laser light sheet PTV method at various crank angles during intake, compression, and expansion strokes over the wide range of piston combustion chamber configuration, top clearance, and nominal swirl ratio. Flow fields during compression and expansion strokes were also calculated using KIVA2 simulation code for better understanding of the measured results. The results showed that induction-generated swirl is getting concentric to the cylinder center in compression stroke, and is shifted in the radial direction in expansion stroke.

An experimental study was made to investigate the effect of combustion chamber configuration, top clearance, nominal swirl ratio, and spark plug position on in-cylinder combustion in a spark-ignited natural gas engine, which is converted from a direct injection diesel engine. Flame propagation in a single-cylinder visualization engine was measured from the cylinder axis direction by the high speed schlieren method, over the wide range of combustion chamber configuration, top clearance, nominal swirl ratio, and spark plug position. The results showed that flame does not propagate concentrically to the spark plug, but is shifted by swirl, which is the main flow in this engine. Smaller piston cavity diameter led to more rapid flame propagation, resulting in larger heat release rate and larger cylinder pressure. Piston cavity diameter does not affect the initial combustion until TDC.

For the final goal of developing the natural gas fueled spark ignition engine with high thermal efficiency and low pollutant emission, the effects of the fluid flow inside a combustion chamber on the combustion process of a homogeneous lean mixture of natural gas and air were examined using a rapid compression combustor. The rapid compression combustor was designed to simulate the combustion process in a spark ignition engine involving the rapid compression of a mixture and the heal release during flame propagation. The main advantage of using this combustor is that experiments can be made under the idealized and well-controlled conditions. The time history of pressure in the combustion cylinder was measured with a pressure transducer. The fluid flow in the combustion cylinder was varied using two kinds of experimental technique. First, compression ratio, piston speed and the configuration of the piston head were changed.

The authors have observed diesel spray structures by laser sheet Miescattering methods at room temperature under several ambient pressures(from 0.0 KPa to 2.1 MPa), and measured spray penetrations, spray-anglesand spray inner structures of light diesel oil. The results of spray-anglemeasurements showed that the spray-angle increased with an increase in theambient pressure near a nozzle tip. The spray-angle far from the nozzletip had the minimum value of spray angle at about 0.6 MPa ambientpressure. The spray structure had periodic high density portions occurringat a constant frequency (about 80 KHz). The frequency was time invariantand independent of ambient pressure. These results suggested that theperiodic portions were caused by the inner structure of the injector orthe structure of the nozzle.

An experimental study was made to assess and to identify the role of the properties of various kinds of liquid fuels in the combustion processes and the exhaust emission of nitric oxide in a spark ignition engine. Attention was focused primarily on the chemical aspects of the fuel properties while the influence of physical parameter was kept minimized. The liquid fuels were vaporized and mixed well with fresh air prior to the spark discharge and subsequent flame propagation inside the combustion chamber. The physical state of the mixture charged inside the combustion chamber was observed by using a laser light scattering technique. The measurements were done of the cylinder pressure, the rate of heat release, the ignition delay, the combustion duration, the brake thermal efficiency and the exhaust NO emission. The influence of the fuel properties was also assessed through theoretical analysis based on the mathematical model to predict the thermal efficiency and NO formation.

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 measurements of the temporal and cyclic fluctuation of the fuel vapor concentration were made close to the spark plug in the combustion chamber of a motored SI engine via laser Rayleigh scattering. The effects of several engine operating parameters on the concentration fluctuation were also examined. The experimental results showed that the concentration fluctuation was composed of the temporal concentration fluctuation in a specific cycle and the cyclic variation of the temporal mean concentration over many cycles, which could be separated and measured accurately with the present developed technique. It was noted that the concentration fluctuation increased during the intake stroke and reached a peak after which it decreased simply during the intake and compression strokes.

A three dimensional numerical analysis is made of in-cylinder process in a typical four-cycle reciprocating spark ignition engine with an off-center intake valve. The conservation equations of mass, momentum and energy are solved on the basis of the finite volume method. The ordinary two-equation model is employed as the turbulence model. Fuel is injected into the intake port, and fuel vapor, fuel droplets and air flow into the cylinder through the valve clearance during the intake stroke. As the inlet boundary condition, the inflow velocity distribution, mass fractions of fuel vapor and droplets are given around the intake valve periphery. For simplicity, it is assumed that fuel droplets move with the gas and have the rates of evaporation which are estimated by the classical quasi-steady theory of a single droplet evaporation. Calculation is made from TDC of intake stroke to TDC of compression stroke at every 10 degrees crank angle.

Laser Rayleigh scattering was applied for the remote, nonintrusive measurements of fuel vapor concentration in the combustion chamber of an automotive SI engine with the multipoint fuel injection. The fuel was simulated by Freon-12, which was injected intermittently or continuously into the flow of dust-free dry air through an intake port. The measurements were made of the time histories of instantaneous fuel vapor concentration at a location in the vicinity of a spark plug in the combustion chamber of the engine motored at 650 rpm for various air fuel ratios, fuel injection durations and fuel injection timings. The measured results were analyzed to derive an ensemble-averaged mean concentration, a cyclic variation of the temporal mean concentration and a temporal concentration fluctuation in a specific cycle.

Exciplex-based fluorescence was employed for the remote, nonintrusive, instantaneous and point measurements of fuel droplet temperature. A hydrocarbon droplet doped with naphthalene and TMPD was allowed to evaporate in a heated gaseous mixture of oxygen, nitrogen, carbon dioxide and water. The fluorescence emission spectra from a droplet subjected to nitrogen laser excitation were measured with an optical multichannel analyzer. Photographic observation showed that a droplet fluoresced with a green color at room temperature. As the temperature was raised, fluorescence became purple. The ratio of fluorescence emission intensities at two different wavelengths was an appropriate criterion for in situ determination of droplet temperature. Oxygen in the ambient gas was found to be a major quencher for the fluorescence. Droplet velocity relative to the ambient gas did not have an appreciable influence on the fluorescence emission spectra.

Laser Rayleigh scattering was applied for the remote, nonintrusive measurements of the time history of the transient fuel vapor concentration in the combustion chamber which was caused by the timed injection of unleaded regular gasoline, n-Pentane and n-Hexane into the intake port of a motored automotive spark ignition engine. The results denonstrated that the fuel vapor concentration increased with the time elapsed from the start of the fuel injection and reached a peak after which it decreased during the intake stroke. It showed a very slight increase during the compression stroke. It was also revealed that the fuel vapor concentration increased with an increase in the quantity of fuel injected, the engine speed and the fuel injection pressure. It showed a maximum as a function of the fuel injection timing.

An experimental study was made of the time and space resolved measurements of the diameter of the fuel droplets inside the combustion chamber which were resultant from the timed injection of liquid fuel into the intake port of a motored automotive spark ignition engine. The determination of the individual droplet diameter during the intake and the compression strokes was based on the intensity of the light scattered from the droplet which was subjected to the monochromatic irradiation of He-Ne laser with uniform intensity profile. A theoretical analysis was also done to simulate the evaporation history of a fuel droplet subjected to the highly transient environments in the combustion chamber of the engine. The results showed that the droplets survived at the last stage of the compression stroke while their diameters decreased with crank angle elapsed due to evaporation. The effects of engine parameters on the droplet diameter were extensively discussed.

A theoretical analysis supplemented by an experimental work was conducted of the behavior of liquid fuel droplets subjected to a pulsative air flow in a T-branched duct of a square cross section for a better understanding of fuel transport process in an intake manifold of an automotive spark ignition engine. The analysis includes the formulation of the simultaneous equations of momentum, heat and mass transfer for computing the locations, temperatures and diameters of moving droplets as a function of spatial coordinates. The results were expressed primarily in terms of the location at the impact deposition of droplets relevant to the formation of liquid film on the bottom wall of the duct. It was revealed that the calculated results agreed well with the empirical data.

An experimental study was made of the fundamental aspect of the mixture formation in the combustion chamber of automotive spark ignition engine with the multipoint fuel injection. The mixture formation during intake stroke of an engine was simulated by the timed or continuous injection of Freon-113 or Freon-12 into the steady flow of dust-free dry air through an intake port. The vapor concentration in the transparent combustion cylinder was determined with the application of the laser Rayleigh scattering. The results showed that the present optical system was useful for the time and space resolved measurements of vapor concentration in the combustion chamber in the case of liquid and gaseous fuel injections. The spatial distributions of the time averaged vapor concentration were highly heterogeneous. It was also found that the vapor concentration profile was largely affected by the place for fuel injection and the intake valve lift.