Modeling and simulation of titania formation and growth in temporal mixing layers

Wang, G.; Garrick, Sean C.

doi:10.1016/j.jaerosci.2005.04.007

Cited by 18 publications

(7 citation statements)

References 55 publications

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“…285 Garrick and co-workers applied DNS to describe the growth of TiO 2 nanoparticles from gaseous TiCl 4 via a one-step mixing-limited oxidation in a methane-fed diffusion flame 332,333 and via a onestep hydrolysis reaction at isothermal room-temperature conditions in two co-flowing jets of nitrogen each carrying the respective chemical reactants. 334,335 Their results reveal that the smallest TiO 2 particles appear near the reactor nozzle and grow into larger particles along the flow downstream, while the mean particle diameters and geometric standard deviation both increase with an increasing initial reactant concentration. 332,334 The spatiotemporal DNS also suggests a non-uniform evolution of the geometric standard deviations as a result of the complex mixing of reactants and product particles inside the eddies 334 but becomes more uniform inside the core of a turbulent reacting jet than in the jet periphery.…”

Section: Principles In Process Design and Computational Reactor Modelingmentioning

confidence: 99%

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Meierhofer

Fritsching

2021

Energy Fuels

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The gas synthesis of nanoparticles has gained major interest by different industries and research groups for the development of new materials and their subsequent implementation in numerous devices and applications. Actually, there are numerous research and application activities in flame-based nanoparticle production, mainly focusing on the process and its development, the in situ and ex situ analyses in experiments and simulations and new material and material combination developments. This review provides an overview on the flame synthesis of metal oxide nanoparticles and focuses in particular on the process design of flame spray pyrolysis (FSP). The first part of this review describes the historical background of flame-based particle production and further summarizes the emerging developments, achievements, and trends during the past 2 decades. The second part covers a general process overview of the flame aerosol-based manufacturing by explaining the key aspects of synthesis (chemical raw materials, metal precursors, solvents, and reactor configurations), in situ conditioning approaches, and powder and byproduct collection, along with additional post-processing steps (storage, handling, and modification). Applications of flame-made nanoparticles involve catalysts, gas sensors, energy storage materials, and nanotoxicity studies, among others, which will not be discussed in detail but are overviewed by listing the latest reviews of the respective field. The third part focuses on the growth mechanisms of solid particle products in liquid droplet/spray pyrolysis (liquid-to-particle and gas-to-particle conversion). The concept of characteristic process times is then exemplified for a lab-scaled FSP reactor, while afterward, particle dynamics and continuum models for reactor simulation are reviewed. The fourth part is a survey of more than 20 different diagnostic techniques that are commonly employed for characterization of reactive sprays and flame-made powders. We briefly explain the metrology basics of each method, indicate advantages and limitations, and present exemplary measurement results that have been acquired on flame reactor facilities for particle synthesis. Finally, we summarize the review and address some current challenges that might potentially shape the near future of nanoparticle synthesis in flame sprays.

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Section: Principles In Process Design and Computational Reactor Modelingmentioning

confidence: 99%

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Meierhofer

Fritsching

2021

Energy Fuels

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“…. , [27]. Monomers of size 0.5 nm in diameter populate bin 1 while bins 2 and 3 are populated by clusters of molecules.…”

Section: Particle Fieldmentioning

confidence: 99%

“…Researchers have also considered the effects of turbulence on particle growth. Strakey et al [15] studied the role of turbulence on the characteristics of TiO 2 powder made by TiCl 4 oxidation and they found that the increased turbulence intensity narrowed the size distribution of the product powder indicating that the particle growth may be dominated by reactant mixing rather than by particleparticle collisions. These computations are quite compute intensive as they resolve all of the appropriate length and time scales.…”

Section: Introductionmentioning

confidence: 99%

Growth Mechanisms of Nanostructured Titania in Turbulent Reacting Flows

Garrick

2015

Journal of Nanotechnology

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Titanium dioxide (titania) is used in chemical sensors, pigments, and paints and holds promise as an antimicrobial agent. This is due to its photoinduced activity and, in nanostructured form, its high specific surface area. Particle size and surface area result from the interplay of fluid, chemical, and thermal dynamics as well as nucleation, condensation and coagulation. After nucleation, condensation, and coagulation are the dominant phenomena affecting the particle size distribution. Manufacture of nanostructured titania via gas-phase synthesis often occurs under turbulent flow conditions. This study examines the competition between coagulation and condensation in the growth of nanostructured titania. Direct numerical simulation is utilized in simulating the hydrolysis of titanium tetrachloride to produce titania in a turbulent, planar jet. The fluid, chemical, and particle fields are resolved as a function of space and time. As a result, knowledge of titania is available as a function of space, time, and phase (vapor or particle), facilitating the analysis of the particle dynamics by mechanism. Results show that in the proximal region of the jet nucleation and condensation are the dominant mechanisms. However once the jet potential core collapses and turbulent mixing begins, coagulation is the dominant mechanism. The data also shows that the coagulation growth-rate is as much as twice the condensation growth-rate.

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“…When the PBE is coupled with the Navier-Stokes equation, modelling is required for the multiscale, non-linear interactions of the particlulate dynamics and the turbulent flow. In the context of large eddy simulations (LES), Loeffler et al (2011) and Wang and Garrick (2006) investigated the formation and growth of titanium dioxide nanoparticulates, but neglected particulate-turbulence interactions. Neuber et al (2017) used the sectional method and showed that the error associated with omission of sub-grid turbulence interactions can be large for the highly non-linear nucleation and surface growth processes.…”

Section: Introductionmentioning

confidence: 99%

Sparse-Lagrangian PDF Modelling of Silica Synthesis from Silane Jets in Vitiated Co-flows with Varying Inflow Conditions

Neuber

Kronenburg

Stein

et al. 2020

Flow Turbulence Combust

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This paper presents a comparison of experimental and numerical results for a series of turbulent reacting jets where silica nanoparticles are formed and grow due to surface growth and agglomeration. We use large-eddy simulation coupled with a multiple mapping conditioning approach for the solution of the transport equation for the joint probability density function of scalar composition and particulate size distribution. The model considers inception based on finite-rate chemistry, volumetric surface growth and agglomeration. The sub-models adopted for these particulate processes are the standard ones used by the community. Validation follows the "paradigm shift" approach where elastic light scattering signals (that depend on particulate number and size), OH-and SiO-LIF signals are computed from the simulation results and compared with "raw signals" from laser diagnostics. The sensitivity towards variable boundary conditions such as co-flow temperature, Reynolds number and precursor doping of the jet is investigated. Agreement between simulation and experiments is very good for a reference case which is used to calibrate the signals. While keeping the model parameters constant, the sensitivity of the particulate size distribution on co-flow temperature is predicted satisfactorily upstream although quantitative differences with the data exist downstream for the lowest coflow temperature case that is considered. When the precursor concentration is varied, the model predicts the correct direction of the change in signal but notable qualitative and quantitative differences with the data are observed. In particular, the measured signals show a highly non-linear variation while the predictions exhibit a square dependence on precursor doping at best. So, while the results for the reference case appear to be very good, shortcomings in the standard submodels are revealed through variation of the boundary conditions. This demonstrates the importance of testing complex nanoparticle synthesis models on a flame series to ensure that the physical trends are correctly accounted for.

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Modeling and simulation of titania formation and growth in temporal mixing layers

Cited by 18 publications

References 55 publications

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Synthesis of Metal Oxide Nanoparticles in Flame Sprays: Review on Process Technology, Modeling, and Diagnostics

Growth Mechanisms of Nanostructured Titania in Turbulent Reacting Flows

Sparse-Lagrangian PDF Modelling of Silica Synthesis from Silane Jets in Vitiated Co-flows with Varying Inflow Conditions

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