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The accumulation of particulate matter in lubricant oil can become an important issue in Diesel engines where large amounts of Exhaust Gas Recirculation (EGR) are used at medium to high load operating conditions. Indeed, the transport and subsequent accumulation of particulate matter in the engine oil can negatively impact the oil lubricant properties which is critical to ensure mechanical durability and limit the vehicle Total Cost of Ownership (TCO) by reducing the servicing intervals. The objective of this investigation was to gain an improved understanding of the underlying mechanisms that are responsible for the accumulation of particulate matter in the lubricating oil, and ultimately provide design guidelines to help limit this phenomenon. The present study presents the development and validation of experimental and numerical tools used to investigate this phenomenon.

For several years, the development of combustion and injection systems has been focused on drastically reducing pollutant emissions while preserving the high fuel efficiency which characterizes Diesel engines. In the mean time, the industrial robustness and the customer reliability had to be secured for worldwide applications. Within this working frame, project investigations have shown the importance of injector nozzle characteristics as a potential to greatly improve the fuel spray quality and thereby reduce engine-out emissions. Design parameters like hole diameter, hydro grinding, conicity or inlet hole radius have shown a direct influence on the internal hydraulic flow, allowing a better trade off between high performances and emissions; at the same time, induced cavitation has been identified not only for its well known influence on the discharge coefficient but also for its key role versus coking phenomena which especially appear with small hole diameters.

This experimental work is linked to the recent development of Gasoline Direct Injection engines and is dedicated to the study of the airflow entrained by the hollow cone spray issued from an injector for Gasoline Direct Injection engines. This spray is a dense unstationary two-phase flow that interacts with the surrounding air. The mechanism of air entrainment, due to the momentum exchange between the spray drops and the gaseous phase is an important phenomenon responsible for droplets vaporisation and mixture formation. The latter are directly linked to the reduction of fuel consumption and pollutant emissions. By application of the PIV technique, measurements of air velocity near the spray edge have been performed and used to compute the mixing rate q in the spray, by mass conservation through a cylindrical control surface (q is defined as the ratio between the mass flow rate of entrained air and the liquid mass flow rate injected). The influence of two parameters on q is studied.