Modelling and Optimization of SCR-Exhaust Aftertreatment Systems

Chen, Ming; Williams, Shazam

doi:10.4271/2005-01-0969

Cited by 45 publications

(26 citation statements)

References 6 publications

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“…The conversion factor model does not provide enough information about UWS spray and decomposition processes to optimize the UWS dosing system, because it neglects the effects of UWS injection angle and location on ammonia conversion efficiency and the uniformity of the concentration distribution at the catalyst entrance. For design optimization purposes, Chen and Williams23 proposed the use of Eddy‐dissipation model to simulate urea thermolysis. However, neglecting of chemical kinetic data may lead to ambiguous results.…”

Section: Introductionmentioning

confidence: 99%

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Modeling the depleting mechanism of urea‐water‐solution droplet for automotive selective catalytic reduction systems

Abu-Ramadan

Saha

2011

AIChE Journal

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in Wiley Online Library (wileyonlinelibrary.com).The current work aims to develop a reliable theoretical model capable of simulating the depletion process of urea-water-solution (UWS) droplets injected in a hot exhaust stream as experienced in an automotive urea-based selective catalytic reduction system. A modified multicomponent vaporization model is presented and implemented in the current study to simulate the behavior of UWS droplet in heated environment. Although water depletion is modeled as a vaporization process, urea depletion is modeled using two different approaches: (i) vaporization and (ii) direct thermal decomposition. The suitability of both depletion approaches is assessed in the current study by comparison with experimental data of the decay of a single UWS droplet in a quiescent heated environment. The decay rate of UWS droplet is accurately predicted with the multicomponent vaporization model. The possibility of internal gasification is demonstrated. Based on the complex decomposition behavior of urea, the current study proposes a decomposition mechanism for UWS droplet. The suitability of implementing the rapid mixing approach is assessed through comparison with the diffusion limit approach at various operating conditions and initial UWS droplet sizes. V V C 2011 American Institute of Chemical Engineers AIChE J, 57: 3210-3225, 2011

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Section: Introductionmentioning

confidence: 99%

“…Urea droplets are required to heat up to a critical temperature, T l ≥ 425 K, before effective thermolysis occurs 20. This criterion of critical temperature and also the water vaporization process seem to be missing in the model proposed by Chen and Williams 23…”

Section: Introductionmentioning

confidence: 99%

Modeling the depleting mechanism of urea‐water‐solution droplet for automotive selective catalytic reduction systems

Abu-Ramadan

Saha

2011

AIChE Journal

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“…[2], [5], [6], and [7]. To the best of our knowledge there are no studies published on the effects of spray impact on surfaces and wall film formation at the injection of UWS.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Injection of Urea-Water-Solution for Automotive SCR DeNOx-Systems: Modeling of Two-Phase Flow and Spray/Wall-Interaction

Birkhold¹,

Meingast²,

Wassermann³

et al. 2006

SAE Technical Paper Series

169

109

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The selective catalytic reduction (SCR) based on ureawater-solution is an effective technique to reduce nitrogen oxides (NO x ) emitted from diesel engines. A 3D numerical computer model of the injection of urea-water-solution and their interaction with the exhaust gas flow and exhaust tubing is developed to evaluate different configurations during the development process of such a DeNOxsystem. The model accounts for all relevant processes appearing from the injection point to the entrance of the SCR-catalyst:• momentum interaction between gas phase and droplets• evaporation and thermolysis of droplets• hydrolysis of isocyanic acid in gas phase• heat transfer between wall and droplets• spray/wall-interaction• two-component wall film including interaction with gas phase and exhaust tubeThe single modeling steps are verified with visualizations, patternator measurements, phase-doppler-anemometer results and temperature measurements. CFD simulations of a SCR DeNOx-system are compared to experimental data to determine the decomposition parameters for ureawater-solution droplets. Numerical results for an injection including all processes addressed above are discussed.

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“…Basically the descriptions of the liquid‐to‐vapor mass transfer can be classified into the following types: evaporation models that regard both stages of UWS decomposition as a vaporization process , , , , chemical kinetics models that describe the urea decomposition in an Arrhenius‐type expression , , and more sophisticated models including detailed chemistry, solidification and the internal formation of by‐products . More simplified approaches took a heat transfer limited urea decomposition or a turbulent mixing controlled mass transfer into account.…”

Section: From Liquid To Vapor – Dehydration and Thermolysismentioning

confidence: 99%

Preparation of Ammonia from Liquid AdBlue – Modeling Approaches and Future Challenges

Lauer

2018

Chemie Ingenieur Technik

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Sustainable mobility is a legal and public demand. An important measure to clean the exhaust gas of diesel engines is the conversion of nitric oxides with selective catalytic reduction (SCR). The development of SCR systems can be strongly supported by numerical methods. This review article is to document the status of the CFD-simulation method with respect to the preparation of the injected urea-water solution, the turbulent transport of ammonia and the assessment of solid deposits coming from liquid film. Comparisons with measurements for realistic sprays and mixing sections are given.

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Modelling and Optimization of SCR-Exhaust Aftertreatment Systems

Cited by 45 publications

References 6 publications

Modeling the depleting mechanism of urea‐water‐solution droplet for automotive selective catalytic reduction systems

Modeling the depleting mechanism of urea‐water‐solution droplet for automotive selective catalytic reduction systems

Analysis of the Injection of Urea-Water-Solution for Automotive SCR DeNOx-Systems: Modeling of Two-Phase Flow and Spray/Wall-Interaction

Preparation of Ammonia from Liquid AdBlue – Modeling Approaches and Future Challenges

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