An experimental study on the impact of biodiesel origin on the regulated and PAH emissions from a Euro 4 light-duty vehicle

Abstract

This study investigates the impact of mid-high biodiesel blends on the criteria and PAH emissions from a pick-up diesel vehicle. The vehicle was a Euro 4 (category N1, subclass III) compliant common rail light duty vehicle fitted with a diesel oxidation catalyst. Emission and fuel consumption measurements were performed on a chassis dynamometer using constant volume sampling (CVS) technique, following the European regulations. All measurements were conducted over the NEDC and Artemis driving cycles. Aiming to evaluate the fuel impact on emissions, a soy-based biodiesel, a palm-based biodiesel, and an oxidized biodiesel obtained from used frying oils were blended with an ultra low sulfur diesel at proportions of 30%, 50% and 80% by volume. CO2 emissions and fuel consumption exhibited increases with biodiesel over all driving conditions which ranged up to 5%. NOx emissions were found to be above the Euro 4 limit and increased with biodiesel between 5% and 10% except for the blends prepared with the palm-based methyl ester. The emissions of PM, HC, and CO decreased with the addition of biodiesel reaching maximum reductions in the order of 10%, 30% and 20% respectively; however, some increases were observed over the NEDC which may be attributed to cold-start. Sharp increases in most PAH, nitro-PAH and oxy-PAH compounds were observed with the application of biodiesel. These increases were particularly noticeable with the use of the oxidized blends, a phenomenon that it is related with the type and quality of this fuel. The emissions were also affected by the operating conditions of the engine. It was found that most PAH compounds were decreased as the mean speed and load of the driving cycle increased.