As part of a multi-technology approach to decarbonizing the transportation sector, hydrogen internal combustion engines (H₂ICEs) present both opportunities and challenges. The lambda leap (λ leap) strategy addresses key implementation barriers by enabling the adaptation of modern commercialized engine designs to hydrogen with minimal hardware modifications. This control approach manages combustion stability, improves efficiency, and reduces NOx emissions.
The λ leap strategy operates by switching between stoichiometric and ultra-lean (λ ³ 2.5) air-fuel ratios, thereby avoiding the high-engine-out-NOx regime. It leverages the high brake thermal efficiency and ultra-low engine-out NOx emissions of lean combustion, while preserving full-load performance under stoichiometric conditions.
This study applies the strategy to the Volvo VEP4 2.0 L GDI turbocharged engine platform. A transient evaluation was conducted using a coupled simulation environment that integrates a vehicle model in MATLAB/Simulink with a detailed 1D engine model in GT-Power. The strategy was assessed across multiple vehicle configurations and driving cycles, including the WLTC, to evaluate its dynamic feasibility. Engine-out NOx emissions and aftertreatment requirements were analyzed in the context of future Euro VII targets. The results provide insight into the transient behavior, emissions control challenges, and system-level trade-offs necessary for the practical deployment of the λ leap strategy in H₂ICE applications.