Search Results

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.

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.

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.