Simulation-driven aftertreatment optimization and emissions characterization of a high-efficiency methanol DI engine

Abstract

This study presents an integrated calibration and aftertreatment optimization framework for a 1.5L direct-injection methanol-fueled spark-ignition engine targeting compliance with China 6b emission regulations. Methanol’s unique physicochemical properties, high latent heat of vaporization, fast flame speed, and elevated octane rating, enabled advanced ignition phasing at high loads and significantly reduced CO, HC, NO_x, and PM/PN emissions relative to gasoline. Furthermore, the methanol engine displays unique emission behaviors in response to the aftertreatment system, in contrast to those observed in the gasoline engine. A simulation-driven approach was applied to develop a tailored aftertreatment system, leveraging a validated catalyst performance model to define platinum group metal (PGM) loadings and washcoat architecture. Experimental validation under WLTC conditions demonstrated strong agreement with simulated midbed temperatures and tailpipe emissions, confirming predictive model fidelity. Although calibrated under fresh conditions, a thermal aging sub-model incorporating Arrhenius-based degradation was used to extrapolate full useful life (FUL) catalyst performance over 240,000 km. The results highlight methanol’s heightened sensitivity to catalyst aging due to its oxygen-rich and chemically reactive exhaust composition. To address this, a Design of Experiments (DOE) methodology was employed to optimize catalyst volume and PGM distribution across close-coupled and underfloor positions. The finalized configuration, consisting of dual TWC bricks and an underfloor uGPF, achieved regulatory compliance with reduced PGM usage and packaging feasibility, offering a cost-effective solution for low-emission methanol engine applications.