Combustion aerodynamics of a gas-fired furnace with peripheral fuel injection

As part of a research program to study the combustion characteristics of swirling flames in furnace systems, studies are aimed at improving combustion performance with reduced pollutant emissions. In addition to providing more insight into the processes involved—aerodynamics, combustion, heat transfer, and formation of pollutants—results of these studies are also needed for the validation of furnace prediction models. Measured flow and combustion patterns carried out on a semiindustrial-scale natural-gas-fired furnace are presented. The burner uses a nonconventional fuel injection scheme with the fuel injected around the periphery of the swirling air jet. The furnace is a water-cooled cylindrical combustion chamber of 1-m diameter and 3-m height, fired by natural gas through a variable swirl burner and a quarl. Measurements of the flow and combustion patterns were carried out for two air swirl intensities, swirl numbers 0.9 and 2.25, through radial traverses at 13 axial planes along the furnace. The flow patterns are defined by the radial distributions of the three time-averaged velocity components and static pressure. Also presented are the combustion patterns in the form of measured contours of temperatures and species concentrations of O2, CO2, CO, HC, and NOx. The results demonstrate that peripheral fuel injection produces high rates of mixing, leading to better combustion efficiency and heat transfer. The axial velocity profiles define the main shear areas and the forward- and reverse-flow zones. The temperature and concentration fields illustrate the progress of combustion reactions to completion and the formation of pollutants. The data obtained by the detailed measurements are being used for the validation and development of mathematical models for prediction of furnace flows.