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This paper presents a prospective combustion study about dilution effects on turbocharged SI engine at full load. It proposes a comparative analysis between lean burn and cooled exhaust gas recirculation (EGR) operation as knock improvement artifice in substitute of enrichment. The study was led on a four cylinder 2L engine on stationary test bench. A specific EGR circuit was designed in order to achieve high control of the temperature and mass flow of the recirculated gas. Thanks to instantaneous pressure cylinder transducers, a combustion analysis was carried out using an home-made code. 1-D simulations (WAVE code) were used to complete the analysis on volumetric efficiency and turbocharger behaviour. A real advantage of cooled EGR was observed in the study compared to lean burn or enrichment in terms of performance, heat exchange and specific fuel consumption.

The pollution levels recorded in large urban areas are rising concerns for public health and substantial reductions in pollutant emissions have become an important issue. In this context, engine manufacturers have developed a number of techniques to reduce emission vehicle levels and in particular are turning their attention to the use of clean fuels. One example is the Liquid Petroleum Gas, roughly a mixture of propane and butane, which gives a benefit in terms of toxic hydrocarbons emissions and ozone formation due to its composition (mainly alcanes and olefines from C2 to C5) and CO2 emission levels. The aim of this study was to provide a quick and low cost solution for downtown emissions of motor vehicle. In order to maintain a good autonomy, the development work was focused on a dual fuel vehicle using LPG as well as gasoline.