Given the spread of natural gas engines in low-term toward decarbonization and the growing interest in gaseous mixtures as well as the use of hydrogen in Heavy-Duty (HD) engines, appropriate strategies are needed to maximize thermal efficiency and achieve near-zero emissions from these propulsor systems.
In this context, some phenomena related to real-world driving operations, such as engine cut-off or misfire, can lead to inadequate control of the Air-to-Fuel ratio, key factor for Three-Way Catalyst (TWC) efficiency.
Goal of the present research activity is to investigate the performance of a bio-methane-fueled HD engine and its Aftertreatment System (ATS), consisting of a Three-Way Catalyst, at different Air-to-Fuel ratio. An experimental test bench characterization, in different operating conditions of the engine workplan, was carried out to evaluate the catalyst reactivity to a defined pattern of the Air-to-Fuel ratio. Through the detection of key performance parameters and indicated signals, numerous insights into the combustion process and the amount of chemical species in the upstream and downstream TWC gas flow are provided.
The experimental test campaign has provided an in-depth analysis of the engine behavior in such operating conditions together with a consistent dataset for a subsequent validation of a “quasi-steady” 1D model of the reactor.
A surface reactions kinetic mechanism to simulate the main transport and chemical phenomena inside the catalyst has been set-up in 1D simulation platform. To reproduce the dynamics of oxygen storage and release, reactions involving Cerium are included in the kinetic reaction scheme.
As a final step, a dedicated experimental campaign in two very lean conditions, maintaining the same operating condition and fuel composition, proving to be an evaluable tool to assess the catalyst performance in reproducing the main pollutants formation and conversion.