Consequences of ignition timing on a hydrogen-fueled engine at various equivalence ratio

The energy crisis in the transportation sector directs researchers to look for renewable alternative energy sources. Among all available, hydrogen is one of the prominent contenders that can be renewed and available on a large scale and is carbon-free. The study suggests hydrogen is a better fuel for SI engines than CI engines. However, its feasibility still needs to be investigated. In the present experimental study, a hydrogen-fueled SI engine is tested for various equivalence ratios (ϕ) and ignition timing (IT) at a compression ratio (CR) of 14:1. The outcomes show that the brake thermal efficiency (BTE) increases by 1.07% with increasing ϕ, while a slightly retarded IT exhibits the best figure. There is an average 1.42% increase per ϕ from gasoline noticed at ϕ 0.6, which increased to 2.12% at ϕ 0.8. The cylinder pressure and net heat release rate improve and advance with retarding IT and increasing ϕ. The flame development period (CA10) continuously reduces with increasing ϕ by an average 1.93%/ϕ change and retarding IT by 2.17%/2°CA ignition retard, due to increased mass of hydrogen and increased cylinder temperature. While flame propagation period (CA10-90) reduces with increasing ϕ and reduces to a minimum with retarding IT and then increase. The maximum cylinder temperature (T_max) and exhaust gas temperature (EGT) increase with increasing ϕ by 3.28% and 3.62%, respectively, while T_max reduces with retarding IT, resulting in a reduction in NO_x emission. The EGT increases with retarding IT. The NO_x emissions increase with ϕ by an average of 4.72%; however, at higher ϕ = 0.8, the NO_x emissions are 2.51% lower than gasoline for most of the retarded IT. At a retarded IT, hydrogen performs similarly to gasoline at moderate NO_x emissions. The high CR helps reduce volumetric losses reflected in BTE, found above gasoline despite less fuel energy supplied than gasoline. Although NO_x emissions are controlled by retarding IT, an efficiently controlling IT resulted in a severe drop in BTE.