Optimizing Hydrogen Engine Performance a Comparative Study of Lean & Stoichiometric Calibration Approach

Hydrogen combustion in internal combustion engines offers numerous advantages, such as zero CO2 emissions and high flame speed, which make it a promising alternative fuel for green vehicle solutions. In order to maximize the engine performance with hydrogen, however, meticulous calibration of the air-fuel mixture must be performed, particularly when lean and stoichiometric combustion conditions are considered. Lean burning, i.e., excess air, offers better thermal efficiency and lower NOx emissions but can cause lower engine power and combustion instability. Stoichiometric combustion, however, ensures complete combustion of the fuel-air mixture, but at the cost of higher combustion temperatures and consequently, high NOx emissions. Calibration strategies for hydrogen engines are presented in this paper by comparing the lean and stoichiometric strategies and their implications on engine power output, efficiency, and emissions. Test data from several hydrogen engine configurations demonstrate that lean burn with EGR addition can be employed to minimize NOx emissions at the expense of tight engine stability and power control. On the other hand, stoichiometric operation yields more power but with the requirement for complex emission control systems. The compromises between these calibration strategies are presented in the paper and recommendations are provided on optimizing the performance of hydrogen engines for different operating conditions.