The effect of particle size and volumetric loading on the gas temperature distributions in a particle-laden flow heated with high-flux radiation

Abstract The instantaneous, spatially resolved gas-phase temperature distribution within a particle-laden flow heated using high-flux radiation has been measured for a series of heating fluxes, particle volumetric loadings and particle diameters using two-colour laser induced fluorescence of toluene. The temperature of the gas downstream from the start of the heating region was found to increase with an increase in heat flux, an increase in particle loading and a decrease in particle diameter. Coherent regions of high and low temperature in the instantaneous flow associated with spatial variations in the particle distribution were identified for all particle diameters investigated. The time-averaged gas-phase temperature on the jet axis was found to increase approximately linearly with distance in the region downstream from the heating beam to the edge of the measurement region investigated, indicating near-constant convective heat transfer due to the large temperature difference between the gas and radiatively heated particles throughout this region. The axial gradient of gas-phase temperature with distance was also calculated using a simplified, one-dimensional heat transfer model. The difference between the model and measurements was, on average, less than 20%, with the magnitude of this difference found to increase with a decrease in particle diameter and an increase in particle loading.