Carbon nanotube reactor: Ferrocene decomposition, iron particle growth, nanotube aggregation and scale-up

Conroy, Devin; Moisala, Anna; Cardoso, Silvana S. S.; Windle, Alan H.; Davidson, John

doi:10.1016/j.ces.2010.01.019

Cited by 114 publications

(90 citation statements)

References 29 publications

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“…Secondly, hydrodynamic oscillations can couple with acoustic perturbations to enhance or alter thermoacoustic oscillations Hansford et al 2015), which can cause structural damage. At low to moderate Reynolds numbers, similar flows and nozzle geometries are found in the production of carbon nanotubes (Conroy et al 2010).…”

Section: Introductionmentioning

confidence: 72%

Coherent structures in a swirl injector at Re = 4800 by nonlinear simulations and linear global modes

2016

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The large-scale coherent motions in a realistic swirl fuel injector geometry are analysed by direct numerical simulations (DNS), proper orthogonal decomposition (POD), and linear global modes. The aim is to identify the origin of instability in this turbulent flow in a complex internal geometry.The flow field in the nonlinear simulation is highly turbulent, but with a distinguishable coherent structure: the precessing vortex core (a spiraling mode).The most energetic POD mode pair is identified as the precessing vortex core. By analysing the FFT of the time coefficients of the POD modes, we conclude that the first four POD modes contain the coherent fluctuations. The remaining POD modes (incoherent fluctuations) are used to form a turbulent viscosity field, using the Newtonian eddy model.The turbulence sets in from convective shear layer instabilities even before the nonlinear flow reaches the other end of the domain, indicating that equilibrium solutions of the Navier-Stokes are never observed. Linear global modes are computed around the mean flow from DNS, applying the turbulent viscosity extracted from POD modes. A slightly stable discrete m = 1 eigenmode is found, well separated from the continuous spectrum, in very good agreement with the POD mode shape and frequency. The structural sensitivity of the precessing vortex core is located upstream of the central recirculation zone, identifying it as a spiral vortex breakdown instability in the nozzle. Furthermore, the structural sensitivity indicates that the dominant instability mechanism is the KelvinHelmholtz instability at the inflection point forming near vortex breakdown. Adjoint modes are strong in the shear layer along the whole extent of the nozzle, showing that the optimal initial condition for the global mode is localized in the shear layer.We analyse the qualitative influence of turbulent dissipation in the stability problem (eddy viscosity) on the eigenmodes by comparing them to eigenmodes computed without eddy viscosity. The results show that the eddy viscosity improves the complex frequency and shape of global modes around the fuel injector mean flow, while a qualitative wavemaker position can be obtained with or without turbulent dissipation, in agreement with previous studies.This study shows how sensitivity analysis can identify which parts of the flow in a complex geometry need to be altered in order to change its hydrodynamic stability characteristics.Key Words: † Email address for correspondence: outi-leena.tammisola@nottingham.ac.uk , and the exit velocity from the swirler (U E ). The coordinate system is also defined: the origin is at the centerline at the swirler exit location. The relative dimensions of the geometry are the same as in the numerical simulation, except that the numerical domain is longer in the downstream direction.

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Section: Introductionmentioning

confidence: 72%

Coherent structures in a swirl injector at Re = 4800 by nonlinear simulations and linear global modes

2016

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“…There are several studies of the sock formation mechanism for example, (i) it was believed that the sock forms possibly due to thermophoresis or inertial migration, and the CNT may accumulate at a certain distance away from the wall [22]. The thermophoretic force is a result of temperature gradients and responsible for keeping CNTs from bonding on the reactor tube.…”

Section: Sock Formation By the Convection Vortexmentioning

confidence: 99%

“…Similar as other researchers [22,27], a three-dimensional, steady and compressible flow model has been used for the computational fluid dynamics (CFD) simulation. Using governing equaitons [30,31] for fluid dynamics and heat transfer listed below, the flow field and temperature field in the reactor were computed using ANSYS software [32], ignoring the influence of CNTs in the reactor.…”

Section: Modeling and Simulationmentioning

confidence: 99%

“…Motta et al [16] studied the effect of carrier gas and feedstock injection rate on the sock "spinnability" in a vertical furnace. Some mechanisms have been proposed for the sock formation, including thermophoresis or inertial migration [22], van der Waals attraction [7,28] and electrostatic attraction [29]. However, there is still significant ambiguity surrounding the understanding of how transport issues affecting the sock formation process.…”

Section: Introductionmentioning

confidence: 99%

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The effect of a convection vortex on sock formation in the floating catalyst method for carbon nanotube synthesis

Hou

Wang

et al. 2016

Carbon

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“…Ethanol is attractive fuel because a low percentage of ethanol in fuel does not require any modification in a conventional diesel system. Furthermore, ethanol has been used as a feedstock for CNT growth in CVD methods (Maruyama et al, 2002;Hu et al, 2004;Conroy et al, 2010;Hou et al, 2011) and high-purity SWNT were successfully synthesized on substrates. These facts offer that ethanol is a strong candidate as a carbon source.…”

Section: Introductionmentioning

confidence: 99%

Flame Synthesis of Carbon Nanotube through a Diesel Engine Using Normal Dodecane/Ethanol Mixing Fuel as a Feedstock

Suzuki

Mori

2017

J. Chem. Eng. Japan / JCEJ

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Multi-walled carbon nanotube (MWNT) was synthesized through ame in a diesel engine, in which normal dodecane/ ethanol mixing fuel was employed as carbon and heat sources instead of gas oil. Ferrocene was used as a oating catalyst for MWNT formation and additives such as sulfur and molybdenum were employed as a promoter of MWNT formation. Mean adiabatic combustion temperatures of various experimental conditions were evaluated by measuring CO and CO 2 amounts in the exhaust gas and carrying out a mass and heat balance at the inlet and outlet of an engine. These measurements revealed that not only a mean adiabatic combustion temperature but also CO amount during combustion may play a signi cant role in synthesizing CNT in a diesel engine.

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Carbon nanotube reactor: Ferrocene decomposition, iron particle growth, nanotube aggregation and scale-up

Cited by 114 publications

References 29 publications

Coherent structures in a swirl injector at Re = 4800 by nonlinear simulations and linear global modes

Coherent structures in a swirl injector at Re = 4800 by nonlinear simulations and linear global modes

The effect of a convection vortex on sock formation in the floating catalyst method for carbon nanotube synthesis

Flame Synthesis of Carbon Nanotube through a Diesel Engine Using Normal Dodecane/Ethanol Mixing Fuel as a Feedstock

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