A New Semi-Empirical Temperature Model for the Three Way Catalytic Converter

The effect of back pressure on the light-off of a modern spark ignition engine three-way catalyst has been assessed by measuring the hydrocarbon conversion efficiency in a hot flow bench and in the cold-idle period in an engine. In the flow bench experiment, a small amount of propane/air mixture is used as a surrogate for the hydrocarbon mixture. The conversion efficiency is found to be only a function of temperature. The efficiency is independent of pressure, space velocity, and the equivalence ratio of the hydrocarbon mixture for λ ≥ 1. In the engine test, while the engine-out exhaust gas temperature is higher at a higher back pressure, there is little difference between the gas temperatures at the catalyst entrance for different back pressures at retarded spark timing. This observation is attributed to the larger amount of exhaust hydrocarbon conversion oxidation between the engine exit and the catalyst entrance with the lower back pressure. The heat release from this oxidation compensates for the lower engine-out exhaust temperature at the lower back pressure. The catalyst temperature increases modestly and light-off time shortens correspondingly at the higher back pressure. This observation is attributed solely to the increase in mass flow rate (and thus exhaust sensible enthalpy flow rate) of the engine needed to overcome the additional pumping loss due to the throttling of the exhaust. These results have been confirmed with a simple one-dimensional catalyst model.

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“…An energy balance approach for both the solid and gas phases is used. 5 The gas temperature is given as…”

Section: Modeling Resultsmentioning

confidence: 99%

Back pressure effect on three-way catalyst light-off

Baron

Cheng

2018

International Journal of Engine Research

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“…Another factor influencing heat transfer is the heat transfer coefficient , which can individually be determined by the geometric boundary conditions and fluid properties. With an internally flowed square-channeled geometry, the heat transfer coefficient can be calculated using the Nusselt number ( ), the heat conductivity of the involved gas and the hydraulic diameter ( ) (see Equation (3) and Equation (8)) [47]:…”

Section: Thermodynamic Analysismentioning

confidence: 99%

“…Furthermore, cerium can act as an oxygen buffer. Light-off temperatures of TWCs are reported to be typically in a range between 548 K, e.g., [2,3] and 573 K, [4]. In stationary engines, the TWC technology is also known as non-selective catalytic reduction (NSCR).…”

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confidence: 99%

Heat-Up Performance of Catalyst Carriers—A Parameter Study and Thermodynamic Analysis

et al. 2021

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This study investigates geometric parameters of commercially available or recently published models of catalyst substrates for passenger vehicles and provides a numerical evaluation of their influence on heat-up behavior. Parameters considered to have a significant impact on the thermal economy of a monolith are: internal surface area, heat transfer coefficient, and mass of the converter, as well as its heat capacity. During simulation experiments, it could be determined that the primary role is played by the mass of the monolith and its internal surface area, while the heat transfer coefficient only has a secondary role. Furthermore, an optimization loop was implemented, whereby the internal surface area of a commonly used substrate was chosen as a reference. The lengths of the thin wall and high cell density monoliths investigated were adapted consecutively to obtain the reference internal surface area. The results obtained by this optimization process contribute to improving the heat-up performance while simultaneously reducing the valuable installation space required.

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“…The partial differential equation (PDE) based TWC temperature model presented in Sabatini et al 29 is used in this work to capture the gas and solid phase temperature dynamics inside the catalyst:…”

Section: Twc Physics-based Modelmentioning

confidence: 99%

Physics-based linear model predictive control strategy for three-way catalyst air/fuel ratio control

Mamun

Zhu

Hoffman

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part D:

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The Current practice of air-fuel ratio control relies on empirical models and traditional PID controllers, which require extensive calibration to maintain the post-catalyst air-fuel ratio close to stoichiometry. In contrast, this work utilizes a physics-based Three-Way Catalyst (TWC) model to develop a model predictive control (MPC) strategy for air-fuel ratio control based on internal TWC oxygen storage dynamics. In this paper, parameters of the physics-based temperature and oxygen storage models of the TWC are identified using vehicle test data for a catalyst aged to 150,000 miles. A linearized oxygen storage model is then developed from the identified nonlinear model, which is shown via simulation to follow the nonlinear model with minimal error during nominal operation. This motivates the development of a Linear MPC (LMPC) framework using the linearized TWC oxygen storage model, reducing the requisite computational effort relative to a nonlinear MPC strategy. In this work, the LMPC utilizing a linearized physics-based TWC model is proven suitable for tracking a desired oxygen storage level by controlling the commanded engine air-fuel ratio, which is also a novel contribution. The offline simulation results show successful tracking performance of the developed LMPC framework.

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A New Semi-Empirical Temperature Model for the Three Way Catalytic Converter

Cited by 24 publications

References 9 publications

Back pressure effect on three-way catalyst light-off

Back pressure effect on three-way catalyst light-off

Heat-Up Performance of Catalyst Carriers—A Parameter Study and Thermodynamic Analysis

Physics-based linear model predictive control strategy for three-way catalyst air/fuel ratio control

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