Optimizing thermal performance and exergy efficiency in hydrogen-fueled meso-combustors by applying a bluff-body

Abstract

Recognizing the importance of a bluff-body on the flow separation and its role in enhancing the fuel mixing, the effect of applying a bluff-body on the thermal performance and exergy efficiency in hydrogen-fueled meso-scale combustors are discussed using 3D numerical simulations involving a detailed kinetics mechanism. Key parameters including the bluff-body dimensionless axial location l and combustor configuration are evaluated to obtain the optimal geometry. It is found that the bottom wall mean temperature (BWMT) and its uniformity are significantly enhanced with a bluff-body applied, generally accompanied with a high average Nusselt number. This is mainly due to the fact that the bluff-body can create longitudinal vortices and disrupts the growth of the thermal boundary layer, leading to intensified heat transfer. There is a non-monotonic relationship between BWMT and l with the optimum position being l = 2/5. Further, the proposed Combustor A is involved with a higher and more uniform BWMT. Finally, the exergy efficiency in the bluff-body combustor is found to be higher compared to the conventional combustor, although the elevated pressure loss. This work demonstrates the feasibility of implementing a bluff-body to enhance the thermal performance, and some of the interesting findings can be also applied to power and propulsion systems utilizing the combustor wall temperature.