Evaluation of two-stage advanced turbocharging systems for medium duty hydrogen engine conversion: A comprehensive 1D engine modelling approach

• A 2-stage turbocharging system Diesel engine is selected for hydrogen conversion. • 2 VGTs in 2-stage are needed for the required lean hydrogen-air mixtures. • A highly validated 1D engine model is used for hydrogen performance analysis. • Port injection is less energy efficient than direct injection independently on Lamba. This paper explores the potential of retrofitting traditional fuel engines to hydrogen operation, leveraging their advantage for greenhouse gas emission reduction. Specifically, the work focuses on a 3-litre diesel automotive application engine equipped with a two-stage turbocharging system. Such architecture is particularly interesting for hydrogen applications since it can potentially maintain the lean mixtures typically used on hydrogen engines with a reduced deterioration in performance. First, an extensive experimental campaign on the original diesel engine is used to develop and validate a comprehensive one-dimensional engine model. Subsequently, the developed model is adapted from the computational point of view to evaluate hydrogen operation, including combustion profiles extrapolated from existing literature combined with a predictive sub-model to evaluate knocking limitations as a function of the boost pressure level. Then, the turbocharging system management is optimised under different assumptions. Afterwards, the full-load performance is compared for direct and indirect injection and different dilution levels. According to the simulation results, the hydrogen engine can achieve over 80% of the original diesel engine’s torque output, successfully meeting the target boost pressure, thanks to the versatility of the dual-stage turbocharging system. This research advances hydrogen engine conversion technology, paving the way for cleaner and more efficient transportation systems.