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Front Position (front + position)

Distribution by Scientific Domains
Engineering33%

Selected Abstracts

Reactor performance with primary/secondary swirl intensity and direction in coal gasification process

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2001
Han Chang Cho
Abstract In order to evaluate the effect of swirl direction and intensity of primary/secondary stream on pulverized coal gasification performance, a numerical study was conducted. Eulerian and Lagrangian approaches are used for the gas and solid phase, respectively. The computation code was formulated with PSI-cell method, k,, model for turbulence flow, Monte-Carlo method for radiative heat transfer, and eddy dissipation model for gas-phase reaction rate. A one-step two-reaction model is employed for the devolatilization of Kideco coal. Flow and reactor performance are varied by primary/secondary swirl intensity and direction. For weak primary swirl, the WSF region is minimized at the secondary vane angle beginning generation of internal recirculation zone and having peak coal burnout. The flame stability is improved at counterswirl rather than coswirl due to its intense shear. Meanwhile, for strong primary swirl, flow distribution and coal burnout are the reverse trend with those of weak swirl and the flame stability is somewhat enhanced at coswirl rather than counterswirl. To improve coal burnout and flame stability, it is confirmed that the swirl condition be proposed for moving the flame front position toward upstream. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Fountain flow revisited: The effect of various fluid mechanics parameters

AICHE JOURNAL, Issue 5 2010
Evan Mitsoulis
Abstract Numerical simulations have been undertaken for the benchmark problem of fountain flow present in injection-mold filling. The finite element method (FEM) is used to provide numerical results for both cases of planar and axisymmetric domains under laminar, isothermal, steady-state conditions for Newtonian fluids. The effects of inertia, gravity, surface tension, compressibility, slip at the wall, and pressure dependence of the viscosity are all considered individually in parametric studies covering a wide range of the relevant parameters. These results extend previous ones regarding the shape of the front, and in particular the centerline front position, as a function of the dimensionless parameters. The pressures from the simulations have been used to compute the excess pressure losses in the system (front pressure correction or exit correction). Inertia leads to highly extended front positions relative to the inertialess Newtonian values, which are 0.895 for the planar case and 0.835 for the axisymmetric one. Gravity acting in the direction of flow shows the same effect, while gravity opposing the flow gives a reduced bulge of the fountain. Surface tension, slip at the wall, and compressibility, all decrease the shape of the front. Pressure-dependence of the viscosity leads to increased front position as a corresponding dimensionless parameter goes from zero (no effect) to higher values of the pressure-shift factor. The exit correction increases monotonically with inertia, compressibility, and gravity, while it decreases monotonically with slip and pressure-dependence of the viscosity. Contour plots of the primary variables (velocity-pressure) show interesting trends compared with the base case (zero values of the dimensionless parameters and of surface tension). © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

A simulation of the non-isothermal resin transfer molding process

POLYMER ENGINEERING & SCIENCE, Issue 12 2000
Vincenza Antonucci
A simulation of the non-isothermal resin transfer molding manufacturing process accounting for both the filling and the consolidation stage has been developed. The flow of an exothermally reactive resin through a porous medium has been analyzed with reference to the Darcy law, allowing for the chemorheological properties of the reacting resin. Thermal profile calculations have been extended to a three phase domain, namely the mold, the dry preform and the filled preform. The mold has been included in order to evaluate the thermal inertial effects. The energy balance equation includes the reaction term together with the conductive and convective terms, and particular attention has been devoted to setting the thermal boundary condition at the flow front surface. The moving boundary condition has been derived by a jump equation. The simulation performance has been tested by comparing the predicted temperature profiles with experimental data from literature. Further numerical analysis assessed the relevance of using the jump equation at the flow front position for both filling time and thermal profile determination. [source]

RANS-simulation of premixed turbulent combustion using the level set approach

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
A. Kurenkov
A model for premixed turbulent combustion is investigated using a RANS-approach. The evolution of the flame front is described with the help of the level set approach [1] which is used for tracking of propagating interfaces in free-surface flows, geodesics, grid generation and combustion. The fluid properties are conditioned on the flame front position using a burntunburnt probability function across the flame front. Computations are performed using the code FASTEST-3D which is a flow solver for a non-orthogonal, block-structured grid. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Fountain flow revisited: The effect of various fluid mechanics parameters

AICHE JOURNAL, Issue 5 2010
Evan Mitsoulis
Abstract Numerical simulations have been undertaken for the benchmark problem of fountain flow present in injection-mold filling. The finite element method (FEM) is used to provide numerical results for both cases of planar and axisymmetric domains under laminar, isothermal, steady-state conditions for Newtonian fluids. The effects of inertia, gravity, surface tension, compressibility, slip at the wall, and pressure dependence of the viscosity are all considered individually in parametric studies covering a wide range of the relevant parameters. These results extend previous ones regarding the shape of the front, and in particular the centerline front position, as a function of the dimensionless parameters. The pressures from the simulations have been used to compute the excess pressure losses in the system (front pressure correction or exit correction). Inertia leads to highly extended front positions relative to the inertialess Newtonian values, which are 0.895 for the planar case and 0.835 for the axisymmetric one. Gravity acting in the direction of flow shows the same effect, while gravity opposing the flow gives a reduced bulge of the fountain. Surface tension, slip at the wall, and compressibility, all decrease the shape of the front. Pressure-dependence of the viscosity leads to increased front position as a corresponding dimensionless parameter goes from zero (no effect) to higher values of the pressure-shift factor. The exit correction increases monotonically with inertia, compressibility, and gravity, while it decreases monotonically with slip and pressure-dependence of the viscosity. Contour plots of the primary variables (velocity-pressure) show interesting trends compared with the base case (zero values of the dimensionless parameters and of surface tension). © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]