Effects of the Location of the Pocket Cavity on Heat Transfer and Flow Characteristics of the Endwall With a Symmetrical Vane

A pocket cavity is generated at the junction position of the Low Pressure Turbine (LPT) and the Outlet Guide Vane (OGV) in the rear part of a gas turbine engine. The OGV mainly controls the exhaust flow exiting and provides structural strength of the main engine frame. In the present work, the effect the location of the pocket on the heat transfer of the endwall with a symmetrical vane is investigated. A triangular pocket cavity is built in a rectangular channel and a symmetric vane is put on the endwall downstream of the pocket cavity. Heat transfer and turbulent flow characteristics over the endwall are investigated experimentally and numerically. The distance between the pocket cavity and the symmetrical vane is varied from 10 cm, 15 cm, and 20 cm. Liquid Crystal Thermography (LCT) is employed to measure the heat transfer over the endwall at Reynolds number ranging from 87,600 to 219,000. The turbulent flow details are presented by numerical calculations with the turbulence models, i.e., the k-ω SST model. From this study, high heat transfer regions are usually found at where flow impingement appears, i.e., the pocket boundary edge region and the vane head region. Compared with the case of the smooth channel, the heat transfer is decreased when a pocket cavity is placed upstream of the vane. With the distance between the pocket cavity and the vane becoming larger, the effect of the pocket cavity is weakened and the heat transfer is approaching the smooth channel case, i.e., case 0. The pocket cavity strengthens the flow shedding and separates the flow away from the endwall. The pushed upward flow weakens the flow impingement on the vane and then leads to the decreased heat transfer around the vane.