Effect of non-uniform inlet profile on the combustion performance of an afterburner with bluff body

Abstract

The quenching problem caused by the inlet distortion of the combustor during emergency attitude adjustment of an aircraft has not been adequately solved by a lack of experimental evidence in non-uniform inflow. Six non-uniform inlet velocity profiles with different velocity peak positions and values were built by perforated plates to explore the combustion performance of a bluff body. The results indicate that the velocity profile with a peak and off-center can produce the asymmetry of the dual-vortex structure downstream of the bluff body. The significant phenomenon is that the fluid flows from one vortex to another. More asymmetrical fluid-structure is facilitated by larger peak values or further off-center positions. Then, the asymmetrical flow field leads to non-uniform fuel distribution, which results in an asymmetrical flame and outlet temperature profile. Interestingly, the non-uniformity of outlet temperature increases first and then decreases with the rise of velocity peak position, while it just increases with the growth of the velocity peak value. Compare to uniform inflow, the non-uniform inlet velocity profile will destroy the ignition performance and combustion efficiency in most cases. However, the partial fuel accumulation may occur in the asymmetric fluid structure, which can widen the lean blowout limit. Overall, the flame stability limits and combustion efficiency under the non-uniform inflow in this study are beneficial to the design and application of combustor.