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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 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.

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 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.

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.