Comparative study of pollutant emissions from engine starting with animal fat biodiesel and GTL fuels

Starting is a special transient process of engine operation. Due to its relevance on the overall emissions, it was included in the New European Driving Cycle (NEDC) for certification of light duty vehicles. In this work, a turbocharged, direct injection (DI), diesel engine equipped with common rail injection system and exhaust gas recirculation (EGR) strategy was tested during the starting at thermal conditions specified by NEDC, cold and warm conditions. In order to evaluate the effect of fuel composition on main pollutant emissions (nitrogen oxides, total unburned hydrocarbons, carbon monoxide, smoke opacity and number of particles) produced during this transient process, three different fuels were tested: an animal fat biodiesel, a Gas-To-Liquid (GTL) fuel from natural gas and a conventional diesel fuel with 5.83% of biodiesel, which was used as reference. Results showed that, independently of the fuel used, higher emissions were obtained at cold start. However, depending on the fuel composition pollutant emissions presented different trends.