Fuel cell electric drivetrains, battery electric drivetrains and drivetrains with hydrogen-fueled combustion engines are subject to scientific and political debate. They all have in common that they operate without emitting tank-to-wheel greenhouse gases. The extent to which the use of a specific solution is sensible depends heavily on the application context. In this work, a series production 1.0 L passenger car gasoline engine was converted to hydrogen operation through minor modifications. A lean-burn concept was applied to increase efficiency and mitigate the engine’s nitrogen oxide output. Comparing the combustion process of the gasoline to the hydrogen engine, similar levels of burn velocity, rate of pressure rise, and cyclic variations were observed. However, the series charging system could not meet the air demand of the hydrogen engine. Especially in the low speed range, the exhaust gas enthalpy in lean-burn hydrogen operation is significantly lower than in stoichiometric gasoline operation. As a result, the maximum low speed engine load was limited due to the rapid approach to close-to-stoichiometric operation and the resulting exponentially high NOx emissions. To improve the full load operation in terms of torque output and emissions, the intake and exhaust camshaft phasing was optimized, albeit with slight losses in efficiency.
Kastler et al. (Thu,) studied this question.