Modelling three-way catalytic converter oriented to engine cold-start conditions

Abstract

This article introduces a physical model of a three-way catalytic converter oriented to engine cold-start conditions. Computational cost is an important factor, particularly when the modelling is oriented to the development of engine control strategies. That is why a one-dimensional one-channel real-time capable model is proposed. The present model accounts for two phases, gas and solid, respectively, considering not only the heat transfer by convection between both, but also the water vapour condensation and evaporation in the catalyst brick, which plays a key role during engine cold-start. Moreover, the model addresses the conductive heat flow, heat losses to the environment and exothermic reactions in the solid phase, as well as the convective heat flow in the gas phase. Regarding the chemical model, the oxidation of hydrocarbons and carbon monoxide is considered by means of the Langmuir–Hinshelwood mechanism. Three layers make up the model structure from a kinetic point of view, bulk gas, washcoat pores and noble metal in the catalyst surface. The model takes fuel-to-air ratio, exhaust gas mass flow, temperature, pressure and gas composition as inputs, providing the thermal distribution as well as the species concentration along the converter.

Cold-Start Modeling and On-Line Optimal Control of the Three-Way Catalyst

“…Several authors [2,5,21,25,26,28,33] model the TWC with the single channel approximation, and depending on the number of modeled chemical phenomenon and the level of spatial resolution some models can approach realtime simulation speeds on powerful PC's (i.e. where generating 1 s worth of data requires 1 s of computation time).…”

Cold-Start Modeling and On-Line Optimal Control of the Three-Way Catalyst

“…Several authors [13,14,15,16,17,18,19] model the TWC with the single channel approximation, and depending on the number of modeled chemical phenomenon and the level of spatial resolution some models can approach realtime simulation speeds on powerful PC's (i.e. where generating one second's worth of data requires one second of computation time).…”

Modeling the Catalytic Performance of Coated Gasoline Particulate Filters under Various Operating Conditions

“…5−7 Because of the high computational effort and the broad parameter space, these approaches are not suitable for the simulation of transient driving cycles. 8 The second group of modeling approaches aims to assist in the system engineering of the exhaust gas aftertreatment. 9−12 Hereby, macrokinetic approaches utilizing global Langmuir− Hinshelwood kinetics capture the chemical behavior of the monolith.…”

“…Detailed microkinetic approaches aim to assist in the development of new materials or new structures, for example, the addition of NO storage components . Pore-scale simulations of a coated GPF (cGPF) analyze the washcoat deposition and the influence of the coating on the diffusion. , The kinetics of these models are usually calibrated by synthetic gas test benches with simplified inlet feeds or via density functional theory (DFT) calculations. − Because of the high computational effort and the broad parameter space, these approaches are not suitable for the simulation of transient driving cycles …”