Optical study on the effects of the hydrogen injection timing on lean combustion characteristics using a natural gas/hydrogen dual-fuel injected spark-ignition engine

Lean combustion has the potential to achieve higher thermal efficiency for internal (IC) engines. However, natural gas engines often suffer from slow burning rate and large cyclic variations when adopting lean combustion. In this study, using a dual-fuel optical engine with high compression ratio, effects of direct-injected hydrogen on characteristics was investigated, emphasizing role injection timing. Synchronization measurement in-cylinder pressure high-speed photography performed analysis. The results show that exhibits great improvement in instability power capability Visual images phasing analysis indicate underlying reasons are ascribed fast flame propagation addition. Regarding direct timings, it is found late can efficiency, manifesting advanced phasing, increased heat release rate. Specifically, speed elevated by approximately 50% at −100 CAD than −250 CAD. Further indicates performance volumetric turbulence intensity, distinct centroid pathways different timings. current study provides insights into optimization under conditions.