Evaluation of the non-gray weighted sum of gray gases models for radiative heat transfer in realistic non-isothermal and non-homogeneous flames using decoupled and coupled calculations

Abstract

Radiative heat transfer plays an important role in combustion systems. Good compromise between the accuracy and computational requirements of the weighted sum of gray gases (WSGG) model makes it widely used in CFD simulations. In this paper, the accuracy of various WSGG models is assessed by the comparison with the results of radiative heat source and heat flux calculated by line by line (LBL) approach in a realistic non-isothermal and non-homogeneous flame using decoupled calculations. Then these models are implemented to CFD code to investigate the radiative heat transfer for a 600 kW furnace using coupled calculations. The experimental data from the furnace has been used to evaluate the computational applicability and reliability of WSGG models. Results show that the non-gray formulation of WSGG model is more accurate than gray modelling approach, compared with LBL results. The non-gray WSGG models of Krishnamoorthy et al. (2013), Bordbar et al. (2014) and Shan et al. (2018) provide the minimal overall errors compared with the measured temperature fields. The results demonstrate that using the non-gray approach instead of gray approach for global CFD simulation improves the simulation accuracy of thermal radiation transfer. The computing time of non-gray models is larger, approximately 3–4 times that of gray WSGG models.