Effect of Internal Exhaust Gas Recycling on n-Heptane HCCI Combustion

Abstract

Homogeneous Charge Compression Ignition (HCCI) combustion is currently limited in application due to several key issues such as a narrow operating range, high hydrocarbon and carbon monoxide emissions and lack of control over the onset of combustion. Exhaust gas recycling (EGR) has the potential to 1) provide reasonable control over the HCCI combustion process and 2) extend its operating range. In this paper, the effect of hot internal EGR on ignition timing and heat release rate of HCCI combustion fuelled with n-heptane has been investigated using the CHEMKIN 0-D closed combustion engine simulation package. An attempt has been made to study the effect of individual components of EGR on cylinder-temperature history and the rate of chemical reaction. The results indicate that combustion initiation is directly linked to the thermal energy contained in the hot EGR but the particular chemical species contained in the EGR have different influences towards ignition timing and heat release rate. This theoretical study would be substantiated by experimental work in the near future.