Pre-ignition characterization of partially-stratified natural gas injection

The partially stratified charge (PSC) injection ignition strategy aims to improve thermal efficiency and reduce emissions of lean-burn spark-ignited internal combustion engines by extending the lean limit of operation. The object of the current study is to characterize the pre-ignition formation of the fuel plume in the vicinity of the PSC spark plug, using a complementary experimental and numerical approach. Visualization of the PSC plume was conducted using Schlieren motion photography in a constant volume pressure chamber at various injection pressures and signal durations. Inlet conditions were determined with 1-D and 2-D numerical models derived from experimental conditions. Subsequently, the 3-D numerical study was carried out with FLUENT using the SST k-ω turbulence model. It was found that the simulation results were adequate in representing the experimental data in terms of injection angle and jet penetration. As local fuel concentration of the spark region is vital to the stability of the combustion event, the result of this study will be instrumental in predicting the combustion quality under the PSC regime, leading to an optimized PSC system designs.