Cristiano Vitorino da Silva

ANALYSIS OF THE TURBULENT, NON-PREMIXED COMBUSTION OF NATURAL GAS IN A CYLINDRICAL CHAMBER WITH AND WITHOUT THERMAL RADIATION

Abstract This work presents a numerical simulation of the non-premixed combustion of natural gas in atmospheric air in an axis-symmetric cylindrical chamber, focusing on the effect of thermal radiation on the temperature and chemical species concentration fields and the heat transfer. The simulation is based on the solution of the mass, energy, momentum and the chemical species conservation equations. Thermal radiation exchanges in the combustion chamber is computed through the zonal method, and the gas absorption coefficient dependence on the wavelength is resolved by the weighted-sum-of-gray-gases model. The turbulence is modeled by the standard k − ϵ model, and the chemical reactions are described by the E–A (Eddy Breakup–Arrhenius model). The finite volume method is employed to treat the differential equations. Among other results, the solution of the governing equations allows the determination of the region where combustion takes place, the distribution of the chemical species, the velocity fields and the heat transfer rate by convection and radiation. The results indicate that while thermal radiation has a strong effect on the temperature field and heat transfer, its effect on the chemical reactions rates is of less importance. The numerical results are compared to experimental results obtained by Garréton and Simonin (1994).

CFD analysis of the pulverized coal combustion processes in a 160 MWe tangentially-fired-boiler of a thermal power plant

The strategic role of energy and the current concern with greenhouse effects, energetic and exergetic efficiency of fossil fuel combustion greatly enhance the importance of the studies of complex physical and chemical processes occurring inside boilers of thermalpower plants. The state of the art in computational fluid dynamics and the availability of commercial codes encourage numeric studies of the combustion processes. In the presentwork the commercial software CFX

Assessment of combustion models for numerical simulations of a turbulent non-premixed natural gas flame inside a cylindrical chamber

ABSTRACT This work presents a Computational Fluid Dynamics (CFD) study of the non-premixed combustion of natural gas with air in an axisymmetric cylindrical chamber, focusing on the contribution of the chemical reaction modeling on the temperature and the chemical species concentration fields. Simulations are based on the solution of mass, momentum, energy and chemical species conservation equations. Thermal radiation heat transfer in the combustion chamber is computed through the Discrete Transfer Radiation Method, and the Weighted-Sum-of-Gray-Gases model solves the dependence of gas absorption coefficient on the wavelength. Turbulence is modeled by the standard k-ε model. Regarding the combustion modeling, it is performed a comparison of solutions obtained with the combined Eddy Break-Up/Arrhenius (EBU/Arrhenius) and the Steady Laminar Diffusion Flamelet (SLDF) models. The finite volume method is employed to treat the differential equations. Among other results, the solution of the governing equations allows for the determination of the region where combustion takes place, the distribution of the chemical species and the velocity fields. The numerical results are compared to experimental measurements, showing varied agreements. Results indicate that, in this case, the EBU/Arrhenius model can predict the flame temperature and the concentration of the most important species with better accuracy than the more sophisticated SLDF model.