A study on the effects of porous structure on the environmental and radiative characteristics of cylindrical Ni-Al burners

A promising type of radiation burners are hollow cylindrical burners made of materials with high thermal conductivity. In such burners, an internal combustion mode is possible when the combustion takes place in the cavity space of the burner, which allows obtaining radiation efficiency of up to 60%. The aim of the present work is to experimentally define the impact of the cylindrical burner porous structure on NOX/CO emission values and radiation efficiency with respect to equivalence ratio and firing rate. It has been found that NOx emission is <15 ppm if the equivalence ratio is <0.7. The findings indicate that the lower the firing rate and the smaller the size of the structural elements of the burner, the higher the radiation efficiency and emission of CO is. To gain a further understanding of the combustion conditions influence on the radiation efficiency, the analysis of possible efficiency with the assumption of equality the temperatures of flue gases and the burner surface has been carried out. The results suggest that effective heat exchange processes between combustion products and emitter are realized in cylindrical burners, which allows to achieve radiation efficiency close to the maximum possible in all considering operating conditions.