Computational Fluid Dynamics Analysis of Aerodynamics and Impingement Heat Transfer From Hexagonal Arrays of Multiple Dual-Swirling Impinging Flame Jets

Radiative furnaces pose significant thermal inertia and single impinging flames have been observed to cause occurrence of hotspots on the target surface. Multiple burners arranged in suitable array configuration represent one of the plausible solutions for more uniform heat transfer. In this study, computational fluid dynamics (CFD) simulations have been carried out for multiple swirling impinging flames arranged in a hexagonal array configuration. The turbulence chemistry interactions in the flame field are solved numerically using renormalization group (RNG) based k–ε/eddy dissipation model (EDM) framework. Comparison of co-and-counter-swirling configurations has been studied for interactions and spent gas release mechanism. Multiple swirling impinging flames undergo strong interactions resulting in distortions of recirculation zones (RCZ) for all the surrounding except central flame. Co-swirling flames result in development of higher turbulence in the interaction regions as compared to counter-swirl case. Results indicate that some flames in counter-swirl case are underutilized due to the fluid dynamics developed in the system and co-swirling hexagonal array configuration is a better arrangement for effective heating of target surface. Effect of interjet spacing (S/Dh = 5, 7, and 9) and separation distance (H/Dh = 3, 5, 7, and 9) studied for co-swirl case revealed that peak heat fluxes decreased with increasing interjet spacing and separation distance. Central flame represented a region of low heat flux and this region has been noticed to expand in size for increasing interjet spacings. Suppression of central flame has been observed to be maximum for minimum separation distance.

A Numerical Investigation on Fluid Dynamics and Heating Characteristics of Co-and-Counterrotating Multiple Swirling Impinging Flames Arranged in 3 × 3 Inline Array

Swirling impinging flame jets possess the potential of uniformly heating the target surface. Numerical simulations have been carried out for multiple reacting swirling flows arranged in square 3 × 3 array. The turbulence chemistry interactions in the flow field are modeled using RNG based k-ε/ eddy dissipation model (EDM) framework. Co-and-counterrotating configurations have been compared for interactions and spent gas release mechanism at fixed inter-jet spacing and separation distance. Multiple swirling impinging flames undergo strong interactions resulting in distortions of recirculation zones (RCZs) for all the surrounding but central flame. Co-swirling flames result in development of higher turbulence in the interaction regions as compared with counter-swirl case. Tilted heat flux contours have been noticed for co-swirling impinging flames, whereas heat flux impressions are straight for counter-swirl case. Effect of inter-jet spacing (C/Dh = 5, 7, and 9) and separation distance (H/Dh = 3, 5, 7, and 9) studied for co-swirl case revealed that peak heat fluxes decreased with increasing inter-jet spacing and separation distance. With increase in inter-jet spacing, the width of central flame increased due to increased suppression effect induced by the recirculating gases. Increase in separation distance resulted in decrease of width of central flame and thermal dilution taking place led to decrease in heat flux magnitudes.