Ethanol as a Diesel base fuel: an engine evaluation and optimization

摘要

The main objective of this work is to study the potential of ethanol as a blending component for Diesel fuel and validate its impact on engine behavior. The addition of ethanol to Diesel fuel affects the blend stability. In this study, a Fatty Acid Methyl Ester (FAME) is successfully used to stabilize the ethanol/Diesel blend. After a focus on physical and chemical properties of several Diesel-FAME-ethanol blends, their potential in combustion on a multi-cylinder DI Diesel engine has been evaluated. The engine used on purpose is a commercial direct injected EURO 4 1.6 litre engine, equipped with a second generation common rail injection system and an EGR (Exhaust Gas Recirculation) device. The weak ignitability of the ethanol blends results in an unstable and incomplete combustion at the lower loads, especially for blends presenting low cetane number. From simple to more complex, the combustion settings have been optimized: adjusting the timing, the number and the duration of the injections solves the above problem and improves the noise level. Furthermore, the weak sooting tendency of the ethanol blends allows the use of high EGR rates for a significant NO{sub}x reduction. These results indicate that low levels of PM and NO{sub}x emissions, with a contained fuel consumption penalty and with an acceptable noise level, are achievable when the Diesel-ethanol blends are used in combination with an optimized combustion control.