Progress in probability density function methods for turbulent reacting flows

http://web.engr.oregonstate.edu/~sva/archive/apte_ijmf_plf03.pdf

Large-eddy simulation of swirling particle-laden flows in a coaxial-jet combustor

Numerical simulation of the interaction between turbulence and radiation in reactive flows

Oxy-coal combustion is one of the leading technologies for carbon capture and storage. This paper presents a review of the opportunities and challenges surrounding the development of oxy-coal combustion models and discusses historical and recent advances in specific areas related to computational fluid dynamics (CFD), including char oxidation, radiation, pollutant formation and removal (Hg, NO x and SO x ), and the impact of turbulence. CFD can be used to assess and optimise full-scale retrofit designs and to provide data on matching air-fired heat duties. In addition, CFD can also be used to improve combustion efficiency and identify potential reductions in corrosion, slagging, fouling and trace pollutant emissions. Transient simulations are becoming more computationally affordable for coal combustion, providing opportunities for model development. High concentrations of CO 2 and H 2 O in oxy-coal can influence chemical kinetic rates, burnout and ash properties. The modelling can be improved by incorporating detailed kinetic mechanisms of gasification reactions. In addition, pollutant formation and removal mechanisms must be understood during oxy-coal firing to aid the selection of flue-gas cleaning strategies. Radiative heat transfer using spectral models for gaseous properties may be necessary in oxy-coal modelling because CO 2 and H 2 O molecules have strong emission bands. Finally this review provides a coherent near-term and long-term oxy-coal specific CFD sub-models development strategy to simulate the complex oxy-coal combustion processes, heat transfer and pollutant emissions in power generation systems.

Combustion modelling opportunities and challenges for oxy-coal carbon capture technology

Traditional modeling of radiative transfer in reacting flows has ignored turbulence-radiation interactions (TRI). Radiative fluxes, flux divergences and radiative properties have been based on mean temperature and concentration fields. However, both experimental and theoretical work have suggested that mean radiative quantities may differ significantly from those predictions based on the mean parameters because of their strongly nonlinear dependence on the temperature and concentration fields. The composition PDF method is able to consider many nonlinear interactions rigorously, and the method is used here to study turbulence-radiation interactions. This paper tries to answer two basic questions: (1) whether turbulence-radiation interactions are important in turbulent flames or not; and (2) if they are important, then what correlations need to be considered in the simulation to capture them. After conducting many flame simulations, it was observed that, on average, TRI effects account for about 1/3 of the total drop in flame peak temperature caused by radiative heat losses. In addition, this study shows that consideration of the temperature self correlation alone is not sufficient to capture TRI, but that the complete absorption coefficient-Planck function correlation must be considered.

/pdf/importance-of-turbulence-radiation-interactions-in-turbulent-gvndb7o5ja.pdf

Importance of turbulence-radiation interactions in turbulent diffusion jet flames

The composition probability density function (PDF) method is used to study radiating reactive flows. The method is able to treat turbulence–radiation interactions (TRI) in a rigorous way: many unclosed terms due to TRI in the traditional Reynolds-averaging process can be calculated exactly and all others can be accurately modeled by using the optically thin eddy approximation. The application of the method is demonstrated by considering a simplified methane/air diffusion flame, which shows enhancement of the radiative fluxes as a result of TRI. The importance of considering different TRI terms is investigated, indicating that the absorption coefficient–Plank function correlation is the most important.

Application of composition PDF methods in the investigation of turbulence–radiation interactions

An effective particle tracing scheme on structured/unstructured grids in hybrid finite volume/PDF Monte Carlo methods

Traditional modeling of radiative transfer in reacting flows has ignored turbulence-radiation interactions (TRI). Radiative fluxes, flux divergences and radiative properties have been based on mean temperature and concentration fields. However, both experimental and theoretical work have suggested that mean radiative quantities may di er significantly from those predictions based on the mean parameters because of their strongly nonlinear dependence on the temperature and concentration fields. The composition PDF method is able to consider many nonlinear interactions rigorously, and the method is used here to study turbulence-radiation interactions. This paper tries to answer two basic questions: (1) whether turbulence-radiation interactions are important in turbulent flames or not; (2) if they are important, then what correlations need to be considered in the simulation to capture them. After conducting many flame simulations, it was observed that, on average, TRI e ects account for about 1/3 of the total drop in flame peak temperature caused by radiative heat losses. In addition, this study shows that consideration of the temperature self correlation alone is not su cient to capture TRI, but that the complete absorption coe cient‐Planck function correlation must be considered.

/pdf/importance-of-turbulence-radiation-interactions-in-turbulent-1vijj9yurr.pdf

Importance of Turbulence-Radiation Interactions in Turbulent Reacting Flows

An acceleration method is proposed particularly for the P 1 equation. The radiative energy balance is used as a constraint to correct iterative solutions. The method not only accelerates convergence but also preserves the radiative energy balance, the latter being of great importance when radiation calculations are coupled with flow calculations. This acceleration method can be applied to other elliptical problems with boundary conditions of the second and/or the third kind

Genong Li

Papers

Importance of turbulence-radiation interactions in turbulent diffusion jet flames

Application of composition PDF methods in the investigation of turbulence–radiation interactions

An effective particle tracing scheme on structured/unstructured grids in hybrid finite volume/PDF Monte Carlo methods

Importance of Turbulence-Radiation Interactions in Turbulent Reacting Flows

A Method to Accelerate Convergence and to Preserve Radiative Energy Balance in Solving the P1 Equation by Iterative Methods