Soy-Biodiesel Impact on NOxEmissions and Fuel Economy for Diffusion-Dominated Combustion in a Turbo−Diesel Engine Incorporating Exhaust Gas Recirculation and Common Rail Fuel Injection

Abstract

Alternative fuels are gaining importance as a means of reducing petroleum dependence and greenhouse gas emissions. Biodiesel is an attractive renewable fuel; however, it typically results in increased emissions of nitrogen oxides (NOx) relative to petroleum diesel. In order to develop hypotheses for the cause of increased NOx emissions during diffusion-dominated combustion in a modern diesel engine, an effort incorporating both experimental and modeling tasks was conducted. Experiments using a 2007 Cummins diesel engine showed NOx and fuel consumption increases of up to 38% and 13%, respectively, and torque decreases up to 12% for soy-biodiesel. Fuel properties and ignition delay characteristics were implemented in a previously validated engine model to reflect soy-biodiesel. Model predictions are within 3.5%, 7%, and 9.5%, respectively, of experimental engine gas exchange (airflow, charge flow, and exhaust gas recirculation (EGR) fraction), performance (work output, torque, and fuel consumption), and NOx...