The influence of the enrichment injection angle on the performance of a pre-chamber spark ignition natural-gas engine

Using an enriched pre-chamber is an effective way to extend the lean limit, to reduce the nitrogen oxide emissions and to avoid abnormal combustion in spark ignition natural-gas engines. Enrichment injection in the pre-chamber of a spark ignition natural-gas engine determines the flow field and the fuel–air mixture formation quality in the pre-chamber and has a profound influence on the combustion performance of the engine. In order to study the characteristics of enrichment injection in the pre-chamber of a natural-gas engine, two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics calculations were carried out. The influence of the enrichment injection angle on the engine performance was investigated with the aid of a computational fluid dynamics simulation tool. The results indicate that a change in the enrichment injection angle directly affects the gas motion, the fuel–air mixture formation, the flame propagation and the formation of nitrogen oxides in the pre-chamber and further influences the penetration of the flame jets, the combustion temperature distribution and the formation of nitrogen oxides in the main chamber. There is an optimal injection angle for this research engine. Of the four injection angles that were investigated, an injection angle of 14° results in the lowest nitrogen oxide emissions.