Predicting hydrogen engine performance with water addition using a two-zone thermodynamic model

Abstract

Hydrogen is an alternative fuel for internal combustion engines, with potential to reduce emissions and improve engine efficiency through boosted lean burn operation. The injection of water into hydrogen-fuelled internal combustion engines could offer the benefit of reducing combustion abnormalities and controlling emissions through in-cylinder thermo-physical property changes. A two-zone combustion model was developed and validated to predict the performance of a boosted lean-burn hydrogen spark ignition engine with water addition. This new thermodynamic model incorporates a water-diluted hydrogen laminar flame speed correlation, an extended Zeldovich mechanism for nitric oxide emissions prediction, and the Livengood-Wu integral model for evaluating knocking characteristics based on advanced chemical kinetics. The study offers a comprehensive analysis of a hydrogen-fuelled internal combustion engine operated at various manifold air pressures, equivalence ratios, and quantity of water addition. The study indicated that addition of water significantly reduces combustion abnormalities and emissions. A 1 % water addition, at an equivalence ratio of 0.9 and manifold absolute pressure of 120 kPa, reduces the knock integral by 2 % and nitric oxide emissions by 5 %. Finally, the study underlines the importance of optimizing the water injection amount to balance the trade-offs between engine performance, fuel consumption, emission reduction, and knocking regions. The model is a tool to develop advanced combustion strategies in hydrogen-fuelled internal combustion engines.