On recirculating flow in an opposed jet flame holder

Abstract

The analysis of ducted jets with recirculation has received much attention in recent yearsle4 because of its potential application in high speed combustion systems to obtain enhanced mixing and stable flame. In an opposed-jet Same stabilization system, a small jet of high velocity gas flows in a direction opposite to the confined mainstream of premixed combustible mixture. The stagnation zone created by the interaction of the jet and the mainstream provides the required locally decelerated region and the recirculation of the hot products of combustion is effected due to the jet entrainment in the confined mainstream. Since its inception as a potential flame holder,’ experimental workrU7 has been reported on the opposed-jet system which reveal some gross-behaviour of the flow pattern, but theoretical research on such a flow system for predicting the flow parameters is, however, meagre. A complete analysis of the flow-field demands the simultaneous solution of the relevant differential equations governing the conservation of mass, momentum and energy using the appropriate mathematical model for the different physical and chemical processes involved. The simple ‘integral methods’ proposed by a group of Soviet research workersse7 for the prediction of the flow field for isothermal and also the reacting situation for the opposed-jet system are seriously limited by the boundary layer assumptions which are not strictly valid in recirculating flows. It is only recently that a general numerical method has been available for solving the elliptic partial differential equations for turbulent, recirculating flows. Here, a simplified mathematical model of the flow of a non-reacting turbulent jet spreading into a ducted, uniform, counterflowing stream is proposed. The numerical method of Gosman et ~1.~ is applied to predict the flow parameters in the isothermal situation of an opposed-jet flame holder. Experimental investigations are also carried out for comparison of experimental results with the prediction to validate the prediction procedure.