An Experimental and Modeling Study of HCCI Combustion Using n-Heptane

Homogeneous Charge Compression Ignition (HCCI) is an advanced combustion technology being considered for internal combustion engines due to the potential for high fuel conversion efficiency and extremely low PM and NO_x emissions. In principle, HCCI involves the auto-ignition of a homogeneous mixture of fuel, air and diluents at low to moderate temperatures and high pressure. Previous research has indicated that fuel chemistry has a strong impact on HCCI combustion. This paper reports the preliminary results of an experimental and modeling study of HCCI engine operation using n-heptane, which has a well known fuel chemistry. The experiments were designed to explore the effects of intake temperature, compression ratio, air/fuel ratio, engine speed and turbo-charging on HCCI combustion. A numerical model with detailed fuel chemistry was developed to simulate the combustion process in HCCI engines and predict engine performance. The model captured the main combustion stage and its variation in phasing with critical engine parameters.