Improving Catalytic Conversion Efficiency by Controlling Exhaust Pulsations

Takashi Esaki･Chie Honda･Shinya Sugihara (Sango)

When the engine operates under high load, the large exhaust flow causes high gas velocities within the catalyst, reducing its purification performance. In this study, the pulsation of the engine exhaust was investigated, and purification was improved by reducing fluctuations in flow velocity. Control of the velocity fluctuations within the catalyst was achieved by altering the internal structure of the muffler mounted downstream of the catalyst.

Modal Emission Modeling Using a Data-Driven Approach

Kohei Sakai･Takashi Araki･Takaaki Nagano･Michiharu Kawano (Mazda)

In automotive development, increasingly stringent emission (EM) regulations require effective allocation of functions at the vehicle level, driving the need for fast and accurate model-based emission prediction technologies. To address this challenge, this study proposes a data-driven model that combines steady-state performance maps with AI-based transient correction. Using this approach, a modal emission prediction method applicable to new vehicle configurations with specification changes is developed. The proposed method enables efficient and reliable emission prediction, supporting model-based development in early-stage vehicle design.

Numerical Computational Fluid Dynamics Analysis of Pd-based Three-way Catalysts Considering Detailed Surface Reactions
-Effects of Mass Transport in the Catalyst Layer-

Keita Inoue (Waseda University)･Soichiro Oda (Sapporo Breweries)･Sota Aoyama (Toyota Motor)

To advance exhaust purification efficiency, this study quantitatively evaluates mass transport phenomena within Pd three-way catalysts. CO-O₂ light-off tests were conducted using catalysts coated with an inert alumina top layer to isolate diffusion effects. A comprehensive 1+1D simulation model was developed, integrating physical parameters directly derived from mercury porosimetry and SEM observations. The proposed model successfully reproduced experimental light-off behaviors. Subsequent detailed internal analyses elucidated that under high-temperature conditions, catalytic reactions become strongly diffusion-limited, heavily concentrating near the washcoat surface.

Analysis of Molecular Diffusion in TWC Aggregated Particles with Interconnecting Pores and Evaluation of Reaction Rates in Their Layered Structures

Ryuta Chimoto･Mariko Watanabe (Sophia University)･Katsunori Hanamura (Japan Science and Technology Agency)

We calculated diffusion coefficients for porous ternary catalysts composed of nanoscale particle aggregates featuring submicron-scale interconnected pores using diffusion simulations. These coefficients were subsequently incorporated into a particle-layer model as a simplified representation of the porous structure. By conducting a comprehensive analysis integrating flow, diffusion, and reaction processes, we elucidated the combined effects of the interconnected pore network and particle stacking structure on the overall reaction rate.