Towards H ₂ High-Performance IC Engines: Strategies for Control and Abatement of Pollutant Emissions

In future decarbonized scenarios, hydrogen is widely considered as one of the best alternative fuels for internal combustion engines, allowing to achieve zero CO₂ emissions at the tailpipe. However, NO_x emissions represent the predominant pollutants and their production has to be controlled. In this work different strategies for the control and abatement of pollutant emissions on a H₂-fueled high-performance V8 twin turbo 3.9L IC engine are tested. The characterization of pollutant production on a single-cylinder configuration is carried out by means of the 1D code Gasdyn, considering lean and homogeneous conditions. The NO_x are extremely low in lean conditions with respect to the emissions legislation limits, while the maximum mass flow rate remains below the turbocharger technical constraint limit at λ=1 only. To find a trade-off between the two mixture conditions, three different engine control strategies are simulated, imposing a variation of air-to-fuel ratio from λ=2.3 at low load to λ=1 at high load. Different strategies were considered for the transition between minimum and maximum values, including continuous sweep and instantaneous discontinuity. A maximum in the NO_x emissions is detected at λ around 1.1 - 1.2, while they remain low in ultra-lean conditions. However, poor drivability is obtained in correspondence of λ discontinuity. Different ATS configurations are proposed and evaluated on the basis of the state-of-the-art technologies and their possible development for the particular H₂ engine application. The analysis is carried out by means of numerical simulations performed with the 1D code Axisuite, considering the different emission scenarios associated to the particular engine control strategies and the selected driving cycles (WLTP and RDE). In particular, three different ATS lines are designed, namely TWC-based, SCR-based and LNT-based, exploiting catalytic devices commonly applied on the current Gasoline/Diesel engines. Potential and drawbacks of each configuration are analyzed, considering the requirements in terms of engine control strategies, complexity of the solution, operative temperature, technological challenges and limitation in particular phases of the driving cycle (e.g. cold start or sudden accelerations).