Pollutant Emissions from Starting a Common Rail Diesel Engine Fueled with Different Biodiesel Fuels

Abstract

Engine start is a critical process of diesel engine operation with respect to the stability of the combustion process, specific fuel consumption, and pollutant emissions among others. Additionally, the starting is a transient process included into the New European Driving Cycle (NEDC) established for the certification of light-duty vehicles. In this work, a turbocharged, direct injection (DI), diesel engine equipped with a common rail injection system and an exhaust gas recirculation (EGR) strategy has been tested during the starting. The engine was tested at two different starting modes: NEDC cold start mode (temperature of cooling water and lube oil were approximately ambient temperature ∼20°C) and warm start (the engine was previously warmed up). Regulated pollutant emissions and operating parameters such as engine speed, air and fuel mass flow rates, EGR valve position, etc. were registered during the tests. The engine was fueled with a low sulfur fossil diesel fuel and with three different biodiesel fuels derived from rapeseed, sunflower, and soybean oils. Biodiesel fuels were tested pure and blended with fossil diesel fuel. Results showed that biodiesel fuels led to a reduction of smoke opacity, hydrocarbons, and carbon monoxide during both NEDC cold and warm engine start with similar nitrogen oxide emissions. This work demonstrates that emissions from engine start strongly depend on the injection and exhaust gas recirculation control strategies.