Simulations of Radiative Transfer in Combustion Systems and Developments of High-Order Spectral Harmonics Methods
Speaker: Wenjun Ge, University of California, Merced
Presentation
Abstract
Computational studies of the effects of radiative transfer in combustion have been hindered for a long time by the lack of relatively accurate and computationally affordable radiation models. The reasons are: (i) the radiative properties of gaseous products from combustion of hydro-carbons varies dramatically across the entire spectrum; (ii) the radiative transfer equation (RTE) is an integro-differential equation in five independent variables (three in space and two in direction), which is difficult to solve. The photon Monte Carlo (PMC) method with line-by-line (LBL) database is very accurate but can be quite expensive if a large number of photon bundles are to be traced. One possible alternative is to use high-order spherical harmonics (PN ) methods for solutions of the RTE combined with the full-spectrum k-distribution (FSK) method for combustion problems. The recently developed high-order PN methods have been implemented within the open-source libraries OpenFOAM R and further developed for axisymmetric geometries and special boundary conditions. The performances of high-order PN methods are demonstrated by solving a number of examples covering a wide range of different geometries and varying radiative properties including coupled simulations of an artificial turbulent jet flame, Sandia Flame D×4, which is scaled up from the well-studied Sandia Flame D.
My efforts aim to develop and identify RTE solvers as well as nongray spectral models for predict-ing radiative transfer in combustion or related high-temperature applications. I will first discuss the physical nature of radiative transfer in combustion processes, which explains why it is challenging to design or identify appropriate radiation solvers for any specific size or type of flames. Second, I will describe the nongray treatment of combustion products by FSK spectral method and a recent implementation of a customized FSK look-up table. Finally, I will present the recent developments and performances of high-order spherical harmonics methods showing their strengths and limitations.
Biography
Wenjun Ge's research focuses on developing spherical harmonics-based radiative transfer equation (RTE) solvers and nongray spectral models for radiative transfer in participating and particulate media, particularly in combustion related environment. He just defended his dissertation and is about to receive his Ph.D. degree in Mechanical Engineering from the University of California, Merced. His research is funded by DOE, NSF, and several fellowships from UC Merced. He has published several articles in refereed journals and proceedings of international conferences. He also holds a master's degree in Engineering Thermo-Physics from Sun-Yat Sen University. .