Gas temperature above a porous radiant burner: Comparison of measurements and model predictions

Radiant burner modeling can help clarify issues related to burner development, design and performance. This paper describes a one-dimensional model that simulates bilayered reticulated ceramic radiant burner operation. We represent combustion in a porous medium with a model that includes multistep chemistry, radiative heat transfer in the porous medium, and separate gas and solid energy equations. Species predictions show that almost all of the methane is consumed within the porous medium, the concentration peaks of most radicals are inside the porous medium, and nearly all of the NO is formed in the porous medium. As part of a program to develop a comprehensive radiant burner model, temperature measurements are made above a reticulated ceramic radiant burner. Uncoated fine-wire thermocouples are used to measure gas temperature. A radiation correction that includes radiant flux from the burner is used to adjust the thermocouple measurements. Corrections of 200-300 K are calculated, owing to a relatively large bead (460 μm) and high bead emissivity. OH laser-induced fluorescence (LIF) and laser absorption are also used to determine the gas temperature. The LIF-determined temperatures are corrected for trapping, partial rotational relaxation, and rotational-dependent quantum yields. OH-LIF temperature measurements are slightly higher than thermocouple measurements. Compared to experimental results, the model overpredicts the gas temperature above the burner. Several factors could account for the deviation, including uncertainty in the porous medium properties and the possibility that the chemistry is affected by the solid surface in the porous medium.