Effect of EGR Chemical Components and Intake Temperature on HCCI Combustion Development

Abstract

<div class="htmlview paragraph">In an optical Homogeneous Charge Compression Ignition (HCCI) engine, experiments were performed to study the combustion of different surrogate fuels (n-heptane, 75%n-heptane/25%isooctane, 80%n-heptane/20%toluene). The effect of laboratory simulated EGR rates, inlet temperatures and the presence of different chemical species in the EGR on the ignition combustion timings were analyzed at a fixed equivalence ratio (0.3). The mixture homogeneity was verified by Laser-Induced-Fluorescence on the toluene. The experimental results affirm that the EGR delays the combustion unlike the inlet temperature. Intake CO and CH<sub>4</sub> addition has no effect on ignition timings whereas a promoting effect of NO is checked. A zero-dimensional model was developed and offered encouraging tendencies by comparison with the experiments.</div>