Comparisons between Numerical Simulations and Experimental Measurements of Radiative Heat Flux for a Series of CH₄/N₂ Diluted Laminar Non-Premixed Flames

Abstract

This study presents comparisons between experimental measurements and numerical computations of the radiative heat flux along a control line of measurement for a series of six constant power CH4-N2 air flames in laminar regime. The numerical computations are carried out through ANSYS/Fluent v. 19.0 with user-defined functions to compute the radiative transfer. The numerical model includes the skm-DRM19 chemical mechanism with 21 species and 82 reactions. Thermal and transport properties are taken from CHEMKIN database. The spectral integration of the radiative heat transfer is carried with the weighted-sum-of-gray-gases (WSGG) model, and considering three different approaches. The first one (CR-WSGG model) makes use of coefficients obtained for H2O-CO2 mixtures having constant ratio between their mole fractions. The second approach (NCR-WSGG) is based on the superposition of coefficients obtained separately for H2O and CO2, allowing for local variations in the ratio between the mole fractions. The third approach is Fluent’s standard WSGG-based gray formulation (FLT-WSGG). To distinguish the deviations introduced by the gas models from the other models involved in the global simulation of a flame, a direct spectral integration (DSI) of the radiative transfer using HITEMP2010 data was carried out for one of the flames. Based on comparisons with the direct numerical integration, the CR-WSGG proved to be the most accurate model, while still retaining computational efficiency.