Flow field and Liner Heat Transfer for a Model Annular Combustor Equipped with Radial Swirlers

摘要

Swirling flows for combustion stabilization, flame confinement, and proper fuel mixing and recirculation are prevalent in gas turbine combustor applications. Modern gas turbines use swirlers to induce strong rotating vortices and recirculation of the combustion gases to enhance combustion efficiency and stability. This study presents an experimental investigation of the flow field and wall heat transfer characteristics inside a model annular combustor equipped with radial swirlers. 2D Pwarticle Image Velocimetry (2D-PIV) was used to characterize the flow field inside the combustor model. PIV measurements were taken for a single Reynolds number of 70000. To study the recirculation zone, data along the axial direction of the combustor were captured. The data show a slightly asymmetric flow, with the recirculation zone extending up to 0.45D - 0.7D, where D is the hydraulic diameter of the entire annulus (D = 0.7m). To study the evolution of the rotating vortex and the flow velocity close to the liner walls, PIV data was also captured at six cross-sections of the annular combustor. The vortex center was observed to be ～0.02D below the center of the swirler, consistent with the asymmetry observed in the axial measurements. Infrared (IR) thermography was used to measure the steady state heat transfer coefficients along the outer and inner liner walls for Reynolds numbers of 70000, 130000, and 170000. The comparison between the heat transfer results for the different Reynolds numbers reveals a relatively constant position for the peak heat transfer at 0.15 - 0.180 from the swirler exit for both walls. Computational Fluid Dynamics (CFD) calculations were also performed to better understand the characteristics of the flow inside the model combustor. The CFD model reproduces the experimental setup with a mesh of 25 million cells. A Reynolds-Averaged Navier-Stokes (RANS) model was used in the simulation, qualitatively reproducing the overall characteristics observed in the experiment.