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Diverse techniques have been developed for spray investigations, especially high speed cinematography and microphotography. Recently, the progresses obtained in the application of laser techniques to simultaneous measurement of droplet size and velocity have opened new perspectives for in situ investigations of Diesel fuel jets. In this study, a laser measuring system, based on the Phase Doppler Anemometry method (PDA), is applied to examine the dynamic behaviour of the fuel jet in an experimental direct injection Diesel engine fitted with large optical accesses. The local measurements have been performed for two cases: with combustion and without combustion.

The instantaneous soot formation in a Diesel combustion chamber is generally measured using an auxiliary light source, typically a laser, which leads to use experimental engines with simplified geometries and reduced compression ratio. The proposed optical method use thermal radiations of soot particulates inside the flame to investigate their concentration and temperature. This method, based on the diffraction theory for small particles, is applicable to industrial Diesel engines without major modifications of their main characteristics. Measurements are performed at two locations inside the combustion chamber of an industrial D.I. Diesel engine. The presented results show a radial stratification of the soot concentration, soot particles beeing present primarily in the bowl location. With heavy loads, a second stage of soot generation and oxidization is observed.

A parametric study of SI engine efficiency was carried out using a two-zone cycle simulation. The simulation models are first validated and then used to study the effects of different engine function parameters on the engine efficiency and on energy and availability losses. The following parameters are considered in this study: combustion duration, spark timing, spark plug position, combustion chamber heat isolation and compression ratio. The availability balance has been developed with the purpose of recovering the energy lost. It indicates the percentage of energy that could be recovered out of the total energy lost (in the exhaust system, for instance). This study requires detailed information on the gas state (temperature, pressure) and on the temperatures of the combustion chamber walls and of the cylinder head. Some of these temperatures are almost impossible to measure experimentally with the material available at this time. That is why we resort to cycle simulation.