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

Abstract

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 Particle 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 , where D is the hydraulic diameter of the entire annulus ( m). 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 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 , , andThe comparison between the heat transfer results for the different Reynolds numbers reveals a relatively constant position for the peak heat transfer at 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 ReynoldsAveraged Navier-Stokes (RANS) model was used in the simulation, qualitatively reproducing the overall characteristics observed in the experiment. Nomenclature A = Surface area of the thin heater or = Hydraulic diameter of the combustor = Axial flux of axial momentum = Axial flux of tangential momentum = Heat transfer coefficient = Thermal conductivity of air = Nusselt number = Reference Nusselt number, from Dittus-Boelter correlation for internal turbulent flow 2 = Electric power provided to the thin heater = Prandtl number = Conduction loss heat transfer rate = Heat transfer rate provided by the thin heater = Radial distance from the center of the swirler = Electric resistance of the thin heater = Outer radius of the swirler hub = Reynolds number = Swirl number = Turbulent kinetic energy = Liner wall temperature = Mainstream temperature (temperature of the air inside the combustor model) = Voltage applied to the thin heater = Air velocity at the inlet of the combustor = Tangential velocity (from the center of the swirler) = Radial velocity (from the center of the swirler) = Air velocity component along X = Air velocity component along Y = Velocity vector in the X-Y plane = Kinematic viscosity of air = Distance along the combustor (axial) = Dist...

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