Impact of Ethylene and NO Addition on Fuel Oxidation Under Simulated HCCI Conditions

Abstract

We present an investigation on the chemical influence of some exhaust gas recirculation (EGR) compounds on fuel oxidation, especially the effects of NO and ethylene. Two experimental setups were used: a homogeneous charge compression ignition (HCCI) engine and a jet-stirred reactor (JSR). The first one was chosen for its representativeness and the second one for its well-controlled operating conditions. NO and ethylene were selected because NO is known for its high reactivity and ethylene has a high concentration in the EGR gases. A complex impact of NO and little influence of C₂H₄ on the fuel oxidation kinetics were observed, in accordance with the literature. However, a synergistic effect on fuel oxidation was observed by coupling between NO and ethylene chemistry. For the fuel oxidation, a considerable inhibition at low temperatures and a significant promotion at higher temperatures were observed. These results tend to demonstrate the importance of taking into account the complexity of EGR composition.

Keywords:

• Diesel fuel oxidation
• EGR
• HCCI engine tests
• JSR experiments
• N-heptane/toluene
• NO and C₂H₄ effect