Operating Range Expansion in a HCCI Natural Gas Engine Using Charge and Thermal Stratification in Combustion Chamber

HCCI operating window has two distinct boundaries of knock at higher load region and misfiring/partial burning at lower load region. Moreover, there is no conventional direct way of controlling combustion timing in an HCCI engine. In this research, experimental study were carried out to investigate the effect of thermal and charge stratification on expansion of the operating range of a natural gas HCCI engine. To achieve this aim, a single-cylinder natural gas HCCI engine was used to characterize the effect of key operating conditions, including λ/EGR combination, reformer gas and glow plug tip temperature. The results reveal that increasing EGR ratio because of diluent effect on mixture; move the operation region towards rich boundary. So, it allows for more power. Reformer gas expands operating range toward lean mixtures and increases acceptable points in these region. The glow plug due to the disruption of homogeneous temperature inside the combustion chamber advances the start of combustion and increases the ignition duration.