Influence of EGR compounds on the oxidation of an HCCI-diesel surrogate

Abstract : This paper presents an experimental and numerical study of the impact of various additives on the oxidation of a typical automotive surrogate fuel blend, i.e. n heptane and toluene. It examines the impact of engine re cycled exhaust gas compounds on the control of a Homogeneous Charge Compression Ignition (HCCI) engine. A series of experiments were performed in a highly diluted Jet Stirred Reactor (JSR) at pressures of 1 and 10atm (1atm = 101325Pa). The chosen thermo chemical conditions were close to those characteristic of the pre ignition period in an HCCI engine. The influence of various additives, namely nitric oxide (NO), ethylene (C2H4) and methanol (CH3OH), on the oxidation of a n heptane/toluene blend was studied over a wide range of temperatures (550 1100K), including the zone of the Negative Temperature Coefficient (NTC). A new detailed chemical kinetic reaction mechanism is proposed for the oxidation of the surrogate fuel. It includes reactions of NO, methanol (CH3OH) and ethylene (C2H4) and is used to explain the obtained experimental data. The mechanism is further used to theoretically study the impact of other Exhaust Gas Recirculation (EGR) compounds on the hydrocarbon oxidation, namely ethane (C2H6), formaldehyde (HCHO) and carbon monoxide (CO).