Comparative analysis of knock intensity in spark ignition engines using gasoline and hydrogen–Gasoline blends

• Hydrogen-gasoline knock resulted in higher pressure rise and heat release rate. • Hydrogen-associated combustion knock showed large vibration and higher SPL. • COV was low for hydrogen blends, but single-cycle pressure fluctuations were high. • An intensified knock severity was observed through MAPF and KI analyses. Knock remains a limiting factor for engine performance in spark ignition engines. Understanding knock helps in its identification, management, and prevention, ultimately improving engine efficiency and increasing torque output. This paper investigates knock characteristics associated with gasoline and hydrogen–gasoline combustion. Hydrogen was introduced into the intake manifold of a gasoline direct injection engine, with the hydrogen energy fraction varied up to 25% in increments of 12.5%. Engine speed and output power were kept constant throughout the tests to ensure uniformity and reliable comparisons. The results showed that hydrogen–gasoline blends exhibited higher knock intensity, with increased pressure fluctuations, sound pressure levels, and engine block vibrations during the combustion cycle. However, the cycle-to-cycle variation was reduced for hydrogen blends. Emission-based knock analysis also indicated a worsened scenario for hydrogen–gasoline combustion compared to pure gasoline combustion.