Experimental and numerical investigation of a swirl-stabilized premixed methane/air flame

Abstract

Purpose – The purpose of this paper is to assess the validity of Weller's b-ω flamelet model for practical swirl-stabilized combustion applications. Design/methodology/approach – Swirl-stabilized premixed flame behavior is investigated utilizing an atmospheric combustor test rig. Swirl number of the flow is 0.74 with a cold flow Reynolds number of 19,400 based on the hydraulic diameter at the inlet pipe. Operating condition corresponds to an equivalence ratio of 0.7 at a thermal load of 20.4 kW. Reacting flow was seeded with TiO2 particles, and velocity distribution at the center plane was measured utilizing particle image velocimetry. These results serve as a validation dataset for numerical simulations. An open-source computational fluid dynamics (CFD) code library (OpenFOAM) is used for numerical computations. These unsteady Reynolds averaged Navier Stokes (RANS) computations were performed at the same load condition corresponding to experimental data. Parallel numerical simulations were carried out on 128 processor cores. To resolve turbulence, Menter's k-ω shear stress transport model was utilized; flame behavior, on the other hand, was described by Weller's b-ω flamelet model. A block-structured all-hexahedral mesh was used. Findings – It is observed that two counter-rotating vortices in the main recirculation zone are responsible for flame stabilization. Weak secondary recirculation zones are also present at the sides above the dump plane. Flame front location was inferred from Mie scattering images. Experimental findings show that the flame anchors both on the tip of the center body and also at the rim of the outlet pipe. Numerical simulations capture the complex interactions between the flame and the turbulent flow. These results qualitatively agree with the flame structure observed experimentally. Practical implications – Swirl-stabilized combustion systems are used in many practical applications ranging from aeroengines to land-based power generation systems. There are implications regarding the understanding of these combustion systems. Social implications – Better understanding of combustion systems contributes to better performing turbine engines and reduced emissions with implications for the entire society. Originality/value – The paper provides experimental insight into the application of a combustion model for a flame configuration of practical interest.