Relations between global recirculation ratio and area ratio in combustors fired with jets

This paper deals with the conception of burners aiming at a desired value of recirculation ratio, K_V. This is particularly important to flameless oxidation, a combustion technique relevant for heat processing applications. First, from physical reasoning, it is established that K_V does not depend on injection velocity and is governed by the chamber-to-nozzles area ratio, α. Next, two fundamental configurations are studied with a numerical tool, to obtain curves that allow the estimation of the area ratio necessary to obtain a determined K_V. In the particular case of the design of flameless oxidation jet-fired burners, values of α>40 should be sought. The results, presented in non-dimensional form, can be exploited in the design of systems based on jet entrainment to achieve dilution of the incoming fluid, whether in the combustion field or others.