Comprehensive Investigation on the Effect of the EGR Components on n-heptane HCCI Combustion

The main aim of the current study is a comprehensive investigation of the different effects of EGR on n-heptane lean homogeneous combustion. Achieving the goal, a thermodynamic multi-zone model coupled to a semi-detailed chemical kinetics mechanism is utilized. A single-zone model is used for the simulation of the gas exchange process. Due to lean combustion, N2, O2, H2O, and CO2 are considered as the main products of combustion, and their thermal, chemical and dilution effects are studied using the artificial inert species method. An HCCI engine is considered as the combustion chamber and n-heptane is the used fuel. At first, the model is validated against the experimental data and then different values of EGR are added to the in-cylinder mixture, and its thermal, dilution and chemical effects are discussed. The results show that for lean low-temperature combustion the dilution effect of EGR is more significant than its chemical and thermal effects. N2 and H2O have more significant thermal effects on HCCI combustion of a very lean mixture and lean mixture. The dilution effects of O2 is different from other species because it participates in chemical reactions.