Um estudo numérico da influência da radiação sobre a turbulência em uma chama turbulenta 2D axissimétrica

Felipe Roman Centeno,Elizaldo Domingues Dos Santos,Cristiano Vitorino Da Silva,Francis Henrique Ramos França

doi:10.4013/ete.2015.112.01

Abstract

This paper presents a study of the influence of thermal radiation on turbulence in the simulation of a turbulent, non-premixed methane-air flame. In such a problem, two aspects need to be considered for a precise evaluation of the thermal radiation: the turbulence-radiation interactions (TRI), and the radiative properties of the participating species, which are treated here with the weighted-sum-of-gray-gases (WSGG) model based on recently obtained correlations from HITEMP2010 database. The chemical reactions rates were considered as the minimum values between the Arrhenius and Eddy Break-Up rates. A twostep global reaction mechanism was employed, while the turbulence modeling was considered via standard k–e model. The source terms of the energy equation consisted of the heat generated in the chemical reaction rates as well as in the radiation exchanges. The discrete ordinates method (DOM) was employed to solve the radiative transfer equation (RTE), including the TRI. Comparisons of simulations with/without radiation demonstrated that radiation influenced turbulent-properties (root mean square of velocity and temperature fluctuations, and turbulent kinetic energy of the velocity fluctuations). Radiation smoothed turbulent-properties fields. The influence of radiation was more important on the temperature fluctuations than on the velocity fluctuations. Keywords: thermal radiation, turbulence, TRI, CFD, non-premixed flame.

Highlights

Combustion problems involve a number of coupled phenomena, such as fluid mechanics, heat transfer, and chemical kinetics of gaseous species and soot, in which thermal radiation can be the dominant heat transfer mode
The numerical accuracy was checked through the grid convergence index (GCI) method (Roache, 1994; Celik et al, 2008) comparing predicted results calculated using this grid with results obtained using coarser grids
This study presented an analysis of the influence of thermal radiation on the turbulence in a turbulent non-premixed methane–air flame in a cylindrical combustion chamber

Summary

Introduction

Combustion problems involve a number of coupled phenomena, such as fluid mechanics, heat transfer, and chemical kinetics of gaseous species and soot, in which thermal radiation can be the dominant heat transfer mode. As one advance to the GG model, the weighted-sum-of-gray-gases (WSGG) (Hottel and Sarofim, 1967) makes perhaps the best compromise between accuracy and computation demand, especially in global simulation of combustion processes in which the RTE is solved together with fluid flow, chemical kinetics and energy equation.

Results

Conclusion