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Injection Velocity (injection + velocity)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Profiling of injection velocity for uniform mold filling

ADVANCES IN POLYMER TECHNOLOGY, Issue 1 2006
Xi Chen
Abstract Uniform melt front velocity is recommended for injection mold filling to minimize the part nonuniformity. A method of profiling the injection velocity for such a uniform mold filling is presented in this paper. Based on a neural network model developed for estimating the melt flow length from online measurable variables, the profiling problem is transformed into an optimization to minimize the difference between the predicted melt flow length and a given ramp. The rate of the ramp determines the rate of the melt front velocity traveling in the cavity during filling. Experiments with different molds show that the proposed method is effective in profiling the screw injection velocity to achieve a uniform mold filling. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 13,21, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20054 [source]

Two-scale continuum model for simulation of wormholes in carbonate acidization

AICHE JOURNAL, Issue 12 2005
Mohan K. R. Panga
Abstract A two-scale continuum model is developed to describe transport and reaction mechanisms in reactive dissolution of a porous medium, and used to study wormhole formation during acid stimulation of carbonate cores. The model accounts for pore level physics by coupling local pore-scale phenomena to macroscopic variables (Darcy velocity, pressure and reactant cup-mixing concentration) through structure-property relationships (permeability-porosity, average pore size-porosity, and so on), and the dependence of mass transfer and dispersion coefficients on evolving pore scale variables (average pore size and local Reynolds and Schmidt numbers). The gradients in concentration at the pore level caused by flow, species diffusion and chemical reaction are described using two concentration variables and a local mass-transfer coefficient. Numerical simulations of the model on a two-dimensional (2-D) domain show that the model captures the different types of dissolution patterns observed in the experiments. A qualitative criterion for wormhole formation is developed and it is given by , , O(1), where , = . Here, keff is the effective volumetric dissolution rate constant, DeT is the transverse dispersion coefficient, and uo is the injection velocity. The model is used to examine the influence of the level of dispersion, the heterogeneities present in the core, reaction kinetics and mass transfer on wormhole formation. The model predictions are favorably compared to laboratory data. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]