Hydrogen Heavy Duty ICE: Study of some control and calibration solutions to improve performances

Considering the trend of legislative frameworks regarding transport sector and, specifically, Internal Combustion Engine (ICE) emissions; it was of interest to study Hydrogen as an alternative fuel since its peculiarity of being a fuel with no carbon atoms and thus not producing carbon mono/dioxide as combustion products. An inline 6 cylinders 13 liters Hydrogen Internal Combustion Engine is studied as an example of typical ICE adopted for on-road heavy duty vehicles. A mono dimensional thermo-fluid dynamic model is adopted to simulate the impact of Variable Valve Actuation (VVA) and Cylinder Deactivation (CDA) on engine performances with a focus on Brake Thermal Efficiency (BTE). Numerical tool used for these computations was GT-Power®. At first, baseline engine performances have been evaluated evidencing the difficulty of such engine to achieve target full load torque at low rpm. To address this problem, a preliminary turbocharger size investigation has been carried out in to verify whether baseline turbocharger replacement would allow to achieve target torque at Low End Torque (LET) engine operating point. The results of this investigation suggested that, if a specifically sized turbocharger for LET is selected it is possible to increase performances at low engine speeds; however, when approaching higher rpms, a general worsening of performances in terms of BTE, Volumetric Efficiency and Pumping losses is experienced. With the aim to increase LET torque and BTE, Variable Valve Actuation (VVA) is introduced into the model. A series of full factorial Design of Experiments (DOEs) is performed inside a predetermined exploration window to find the optimal combination of valve lift and timing. The obtained results are than used to produce, thanks to interpolation, a series of maps representing intake or exhaust valve lift and timing as function of engine load and speed. Such maps have been used as lookup tables into the 1D engine model to simulate the complete engine map which is than compared to baseline engine configuration evidencing a general improvement of BTE with best results obtained for low loads points. Starting again from baseline engine configuration, the possibility to adopt Cylinder Deactivation is explored with the goal to improve BTE at low loads moving engine working points in a higher efficiency region. Exhaust trapping, Air trapping and Residual trapping strategies are implemented and compared thanks to the introduction of a controller into the model allowing to select which cylinders to deactivate together with deactivation timing of intake and exhaust valves and that of fuel injector. Obtained results show a net advantage in the use of the latter strategy which led to the increase in BTE for low loads points. All three strategies suggested that mid load points where not suitable for CDA implementation since disadvantages in terms of lower turbocharger efficiency outmatched the advantages given by full throttle operation. As last step, thanks to a series of engine maps exported from the three engine models (Baseline, VVA and CDA), a Simulink® model is adopted to simulate engine performances in transient conditions along different driving cycles generated with the use of VECTO® software representative of typical long haul, regional or urban driving conditions. Focus was put mainly on fuel consumption but also exhaust gasses mass flow, temperature and enthalpy are computed which could be of interest for a possible after treatment system. Simulation results showed an