Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic Reactors
Highly transient engine-out emissions imply significant challenges for the optimization and control of automotive aftertreatment systems, motivating studies of the effects of flow pulsations on the system behavior. In this work, an axisymmetric aftertreatment system with a first-order reaction in th...
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| Format: | Article |
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MDPI AG
2022-06-01
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| Series: | Catalysts |
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| Online Access: | https://www.mdpi.com/2073-4344/12/6/613 |
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| author | Pratheeba Chanda Nagarajan Henrik Ström Jonas Sjöblom |
| author_facet | Pratheeba Chanda Nagarajan Henrik Ström Jonas Sjöblom |
| author_sort | Pratheeba Chanda Nagarajan |
| collection | DOAJ |
| description | Highly transient engine-out emissions imply significant challenges for the optimization and control of automotive aftertreatment systems, motivating studies of the effects of flow pulsations on the system behavior. In this work, an axisymmetric aftertreatment system with a first-order reaction in the monolith section is chosen to demonstrate the role of pulsations on the time-averaged conversion at the exit. Reactive computational fluid dynamics simulations under transient conditions are performed by applying the SST <i>k</i>-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> turbulence model along with a reactant species balance equation and a porous medium description of the catalyst. Four different types of temporal velocity variations (constant, step-like, sawtooth and sinusoidal) are applied at the inlet. Additionally, the corresponding fluctuations driven by a prescribed inlet pressure are also investigated. It was found that the fluctuations in the incoming flow affect the transient response of the monolith, the time-averaged conversion, the evolution of the flow uniformity index and the dispersion downstream of the catalyst. It is also shown that the retention time distribution is modulated by the pulsations and that the mixed-cup conversion span is different for geometrically identical systems having the same velocity span if the fluctuation characteristics are different. In conclusion, simulations of phenomena that depend on time-resolved boundary conditions from experiments require proper characterization of fluctuations present in the real-world systems; otherwise, the method of recreating the signal at the boundary may influence the obtained results. |
| first_indexed | 2024-03-10T00:11:31Z |
| format | Article |
| id | doaj.art-d669f8c29b224dc492431892ebcd182b |
| institution | Directory Open Access Journal |
| issn | 2073-4344 |
| language | English |
| last_indexed | 2024-03-10T00:11:31Z |
| publishDate | 2022-06-01 |
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| spelling | doaj.art-d669f8c29b224dc492431892ebcd182b2023-11-23T15:59:20ZengMDPI AGCatalysts2073-43442022-06-0112661310.3390/catal12060613Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic ReactorsPratheeba Chanda Nagarajan0Henrik Ström1Jonas Sjöblom2Division of Combustion and Propulsion Systems, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, SE-412 96 Gothenburg, SwedenDivision of Fluid Dynamics, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, SE-412 96 Gothenburg, SwedenDivision of Combustion and Propulsion Systems, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, SE-412 96 Gothenburg, SwedenHighly transient engine-out emissions imply significant challenges for the optimization and control of automotive aftertreatment systems, motivating studies of the effects of flow pulsations on the system behavior. In this work, an axisymmetric aftertreatment system with a first-order reaction in the monolith section is chosen to demonstrate the role of pulsations on the time-averaged conversion at the exit. Reactive computational fluid dynamics simulations under transient conditions are performed by applying the SST <i>k</i>-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula> turbulence model along with a reactant species balance equation and a porous medium description of the catalyst. Four different types of temporal velocity variations (constant, step-like, sawtooth and sinusoidal) are applied at the inlet. Additionally, the corresponding fluctuations driven by a prescribed inlet pressure are also investigated. It was found that the fluctuations in the incoming flow affect the transient response of the monolith, the time-averaged conversion, the evolution of the flow uniformity index and the dispersion downstream of the catalyst. It is also shown that the retention time distribution is modulated by the pulsations and that the mixed-cup conversion span is different for geometrically identical systems having the same velocity span if the fluctuation characteristics are different. In conclusion, simulations of phenomena that depend on time-resolved boundary conditions from experiments require proper characterization of fluctuations present in the real-world systems; otherwise, the method of recreating the signal at the boundary may influence the obtained results.https://www.mdpi.com/2073-4344/12/6/613computational fluid dynamics (CFD)flow pulsationsreactive flowinlet boundary conditionuniformity |
| spellingShingle | Pratheeba Chanda Nagarajan Henrik Ström Jonas Sjöblom Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic Reactors Catalysts computational fluid dynamics (CFD) flow pulsations reactive flow inlet boundary condition uniformity |
| title | Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic Reactors |
| title_full | Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic Reactors |
| title_fullStr | Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic Reactors |
| title_full_unstemmed | Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic Reactors |
| title_short | Numerical Assessment of Flow Pulsation Effects on Reactant Conversion in Automotive Monolithic Reactors |
| title_sort | numerical assessment of flow pulsation effects on reactant conversion in automotive monolithic reactors |
| topic | computational fluid dynamics (CFD) flow pulsations reactive flow inlet boundary condition uniformity |
| url | https://www.mdpi.com/2073-4344/12/6/613 |
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