Characterization of solid deposits from urea water solution injected into a hot gas test rig

Börnhorst, Marion; Langheck, S.; Weickenmeier, H.; Dem, C.; Suntz, Rainer; Deutschmann, Olaf

doi:10.1016/j.cej.2018.09.016

Cited by 37 publications

(31 citation statements)

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“…At transient operating conditions, the spray will inevitably impinge on the exhaust gas pipe. Liquid films will be formed on the wall leading to undesired formation of solid deposits [8][9][10][11][12][13][14]. As a result, NO x conversion decreases while backpressure increases, affecting both pollutant emissions and engine performance.…”

Section: Introductionmentioning

confidence: 99%

Maximum Spreading of Urea Water Solution during Drop Impingement

et al. 2019

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Droplet impingement of urea water solution (UWS) is a common source for liquid film and solid deposits formed in the tailpipe of diesel engines. In order to better understand and predict wetting phenomena on the tailpipe wall, this study focuses on droplet spreading dynamics of urea water solution. Impingement of single droplets is investigated under defined conditions by high‐speed imaging using shadowgraphy technique. The experimental studies are complemented by numerical simulations with a phase‐field method. Computational results are in good agreement with experimental data for the advancing phase of spreading and the maximum and terminal spreading radius, whereas for the receding phase notable differences occur. For the maximum spreading radius, an empirical correlation derived for glycerol‐water‐ethanol mixtures is found to be valid for millimeter‐sized UWS droplets as well. A numerical simulation for a much smaller droplet however indicates that this correlation is not valid for the tiny droplets of UWS sprays in technical applications.

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Section: Introductionmentioning

confidence: 99%

Maximum Spreading of Urea Water Solution during Drop Impingement

et al. 2019

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“…Results show a residual mass of the sample of about 10 wt.-%, which is not decomposed up to temperature of 600°C. This suggests the presence of temperature resistant species that are not included in current mechanisms of urea decomposition [8]. The deviations of the remaining mass in the TGA analysis of deposit from the experiment 1 and 2 may relate to the slightly different initial composition of investigated samples.…”

Section: Resultsmentioning

confidence: 97%

“…α c denotes an accumulation factor, M i the specific molar mass and h the Henry constant given by Eq. (8).…”

Section: Implementation Of Chemical Kineticsmentioning

confidence: 99%

“…As a result, liquid films are formed on mixer blades or tailpipe walls [1][2][3][4][5][6]. Subsequent evaporation and urea reactions induce the formation of solid deposits [4,5,7,8]. Apart from ammonia, which is the desired product for SCR, solid byproducts like biuret, cyanuric acid or ammelide can be formed from the liquid film [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

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Deposit Formation from Urea Injection: a Comprehensive Modeling Approach

Budziankou

Börnhorst

Kuntz

et al. 2020

Emiss. Control Sci. Technol.

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Long-term reliability is one of the major requirements for automotive exhaust aftertreatment systems with selective catalytic reduction (SCR) using urea water solution (UWS) as NH 3 carrier fluid. A high injection rate of UWS or unfavorable operating conditions may lead to formation of solid deposits, which decrease system efficiency by increasing backpressure and impairing ammonia uniformity. A reliable numerical prediction of deposit formation in urea SCR systems is desired for optimization of system design. However, comprehensive modeling of physical and chemical processes in the tailpipe as well as different time scale phenomena represents a challenging task. This study presents a comprehensive approach for modeling UWS injection, droplet impingement, liquid film and deposit formation based on CFD-simulation. An existing kinetic model for urea decomposition is integrated into the CFD code to predict solid by-product formation from wall films. Physical simulation time is extensively increased by substituting the Lagrange-particles with source terms of mass, momentum and energy reducing simulation time by a factor of 20. The comparison of measured and simulated results shows the capability of the presented modeling approach to predict position and chemical composition of solid deposits.

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“…36) Systematische Analysen der Ablagerungen in einem optisch zugänglichen Modellabgasstrang zeigen, welche thermisch stabilen Produkte entstehen. 37) Darüber hinaus wurde die Fluiddynamik bei der HWL-Aufbe-reitung numerisch simuliert. 38) Wegen der Komplexität dieser HWL-Aufbereitung wurden alternative Verfahren der NH 3 -Bereitstellung im Fahrzeug diskutiert, die auch bei geringen Abgastemperaturen funktionieren könnten, etwa die Zersetzung der HWL in einem zusätzlichen Reaktor im Fahrzeug und anschließender Eindüsung des NH 3 in den Abgasstrang.…”

Section: Prozessanalyseunclassified