The effect of exhaust gas recirculation and premixed fuel ratio on combustion and emissions in a partial homogeneous charge compression ignition-direct injection engine fueled with bioethanol and diesel

Abstract

This paper presents investigations on the effect of exhaust gas recirculation (EGR) and premixed fuel ratio (PFR) of ethanol and on ignition delay, in-cylinder pressure, net heat release rate (NHRR), premixed phase combustion duration, mass fraction burned (MFB), smoke, NOx, unburned hydrocarbon emission (UHC), CO emissions and performance evaluation of partial homogeneous charge compression ignition (HCCI)-direct injection (DI) engine. The single-cylinder diesel engine was modified to operate on partial HCCI mode. Experiments were performed at brake mean effective pressure of 4.2 bar and constant engine speed of 1500 rpm under various premixed fuel ratio (PFR) (0%, 13%, 20%) and EGR (0%, 10% and 20%). An electronically controlled manifold fuel injection mechanism was used to create a homogeneous mixture of ethanol and air. To adjust the quantity and timing of the diesel fuel being injected into the cylinder an in-line fuel injection pump extracted from a tractor engine was used. UHC and CO emissions increase significantly whereas the ignition delay period increases with PFR and EGR. However, it was found that 20% premixed ethanol with 20% EGR ratio results into 56% and 88% reductions in smoke and NOx emissions, respectively, when compared to pure diesel.