Ethanol in a Light-Duty Dual Fuel Compression Ignition Engine: 3-D Analysis of the Combustion Process

A wider use of biofuels in internal combustion engines could reduce the emissions of pollutants and greenhouse gases from the transport sector. In particular, due to stringent emission regulatory programs, compression ignition engine requires interventions aimed at reducing their polluting emissions. Ethanol, a low carbon fuel generally produced from biomass, is a promising alternative fuel applicable in compression ignition engines to reduce CO2 and soot emissions. In this paper, the application of a dual fuel diesel-ethanol configuration in a light-duty compression ignition engine has been numerically investigated. Ethanol is injected into the intake port, while diesel fuel is directly injected into the combustion chamber of the analyzed engine. CFD simulations have been carried out by means of the AVL Fire 3-D code. The operation at given engine load and speed has been simulated considering different diesel injection timings. Numerical results of both the diesel spray development and the dual fuel combustion process have been validated against available experimental data. 3-D analysis allowed to deeply investigate the evolution of the combustion process, particularly the transition between premixed and diffusive phase. The influence of diesel fuel direct injection timing, combustion chamber geometry, and EGR on the combustion process development, hence on engine performance and emission levels, have been highlighted. One of the main results of the use of dual fuel, diesel-ethanol configuration, is a significant reduction of soot and carbon dioxide emissions with respect to diesel-only operation.