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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.