Combustion Process Analysis of Secondary Jet-Guided Combustion in Hydrogen Direct-Injection Engines

This study investigates the effects of secondary jet-guided combustion on the combustion and emissions of a hydrogen direct-injection engine through numerical simulations. The results show that secondary jet-guided combustion, which involves injecting and igniting the hydrogen jet at the end of the compression stroke, significantly shortens the delay period, improves combustion stability, and brings the combustion center closer to the top dead center (TDC), achieving a maximum indicative thermal efficiency (ITE) of 46.55% (λ = 2.4). However, this strategy results in higher NOx emissions due to high-temperature combustion. In contrast, single and double injections lead to worsened combustion and reduced thermal efficiency under lean-burn conditions, but with relatively lower NOx emissions. This study demonstrates that secondary jet-guided combustion can effectively enhance hydrogen engine performance by optimizing mixture stratification and flame propagation, providing theoretical support for clean and efficient combustion.