Gas and solid phase temperature measurements of porous media combustion

Abstract

This work introduces a novel method to determine gas and solid phase temperature profiles in a packed bed porous media combustor. Bare and coated thermocouple junctions were installed in the centerline of the porous combustor and the temperatures of solid phase and bare junctions were recorded simultaneously. Gas phase temperature was obtained considering the influence of flow velocity around the hot junction and the average solid temperature of the hot junction surroundings using the empirical formula for the Nusselt number based on the energy balance for the hot junction. Results show that the junction placement has a lot of influence on hot junction temperature measurement, which leads to a large uncertainty of gas temperature correction. The preheating procedure is used to reduce the effect of the junction placement. It is found that the flow velocity over junction, average solid temperature of the junction surroundings and empirical formula for the Nu number have limited influence on the gas phase temperature correction due to opposite compensating effects of these factors. The temperature profiles measured by thermocouples provide a complete temperature distribution in porous combustor, while a time-based method offers detail gas and solid temperature distributions near the reaction zone. Temperature profiles recorded for solid and gas phases vary for combustion waves propagating upstream and downstream. For all recorded regimes, the temperature gap between gas and solid has maximum and minimum points in the reaction and preheating zones, respectively.