Modelagem fenomenologica e simulação bidimensional de ciclones por tecnicas da fluidodinamica computacional

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

This work presents a mathematical modeling based on the principIes of mass and momentum conservation with the volumetric average point of view, and generalized to represent the multiphase flow in cyclones. It also discusses the hypotheses necessary for flutuating properties treatment, due to Reynolds decomposition applied as statistical treatment of the turbulence. The general model is particularized from additional hypotheses resulting in three different models. The first, dedicated to the gas flow in cyclones - Two-Dimensional Eulerian Model for Gas (EMB)-,the solid phase has not influence on the gas phase, and it is adapted to dealing phenomena such as high vorticity preservation, reversion of the flow, circulation zones, anisotropic behavior of the Reynolds stress and effects of dust collection system on the gas flow. The second, assumes spherical particles with an average diameter, and the agglomerate of particles behaves such as an inviscicid fluid in the Eulerian reference - Two-Dimensional and Two-phase Model for Gas-Solid Flow (EEBB) -, the model permits the attribution of solid phase effects on the gas phase, as the attenuation of the vortex flow, and the pressure drop reduction. With this model it is possible to predict the pressure drop in cyclones. And, finally, the third version couples the model EEBB with a Lagrangian model- Eulerian-Eulerian-Lagrangean Two-Dimensional Model (EELB) -, and it permits the prediction of the particle trajectories as a function of its diameter, and initial position in the entrance of the cyclone, from a field of the gas flow obtained with the EEBB model. With the knowledge of the trajectories for each particle diameter it is possible to predict the collection efficiency curve, and the global efficiency in cyclones. A computational code was developed based on the application of the finite volume method with pressure-velocity coupling like SIMPLE method and staggered grids, with a numerical procedure for the segregated solution of the algebraic equations of the three models. The program was initially submitted to a battery of tests to obtain numeric experience, and to avoid the introduction of programming mistakes. Starting from there, it was chosen the numeric experiments as attempt to validate the models and to analyze the main phenomena in the multiphase flow in cyclones. The main results show that the methodology proposed based in the computational fluid dynamics techniques, is a good tool for studies of improvement of cyclones performance, quantified mainly by reduced pressure drop and high collection efficiency

ASSUNTO(S)

escoamento multifasico dinamica dos fluidos escoamento turbulento ciclones

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