Heat transfer and turbulent flow characteristics over pocket cavity in the junction part of an outlet guide vane in a gas turbine

A pocket cavity is generated when the Low Pressure Turbine (LPT) is connected to the Outlet Guide Vane (OGV) in the rear part of a gas turbine engine due to the different conjugate diameters. This kind of pocket cavities, due to the high Reynolds number and the specific shapes, are hardly investigated in previous researches. The heat transfer distribution and fluid flow over the pocket cavity have significant effects on the incoming flow of the OGV in the downstream distribution. In the present work, the specified triangular pocket cavities are built in a high aspect ratio channel and heat transfer and fluid flow over the pocket surface are investigated experimentally and numerically. These pocket cavities are built with different radii to find out optimized heat transfer distributions and flow patterns. Liquid Crystal Thermography (LCT) is employed to measure heat transfer over the pocket surfaces at Reynolds number ranging from 87,600 to 219,000. Flow details are provided by numerical calculations with a suitable turbulence model. In this study, the largest heat transfer regions over a pocket cavity are found to be at the downstream edge where strong flow impingement occurs. The peak values are influenced by the size of the fillet radius. The smaller fillet radius provides a higher heat transfer peak value with a stronger recirculating flow inside the pocket cavity. However, the pocket cavity with the larger fillet radius can reduce the peak heat transfer values but increase the overall averaged heat transfer value of the pocket surface with weakened strength of the recirculating flows. Accordingly, the larger fillet radius is recommended for the design of the pocket cavity in the rear part of a gas turbine engine.