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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.

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.