Aerothermal Performance of a Cooled Winglet at Engine Representative Mach and Reynolds Numbers

Abstract

This paper presents an experimental investigation of the aerothermal performance of a cooled winglet tip under transonic conditions (exit Mach number of 1.0, and an exit Reynolds number of 1.27 × 106, based on axial chord). Spatially resolved heat transfer data and film cooling effectiveness data are obtained using the transient infrared thermography technique in the Oxford High-Speed Linear Cascade test facility. Aerodynamic loss data are obtained by traversing a specially made and calibrated three-hole pressure probe and a single-hole probe one axial chord downstream of the blade. Detailed contours of Nusselt number show that for an increase in tip clearance, with and without film cooling, and for coolant injection, for both tip clearances, the Nusselt number increases. Also the smaller tip clearance observes higher film cooling effectiveness overall. Detailed distributions of kinetic energy losses as well as pitch-wise averaged loss coefficients and loss coefficients at a mixed-out plane indicate that the size of the loss core associated with the over-tip leakage vortex decreases with cooling injection.

Control of Tip Leakage in a High-Pressure Turbine Cascade Using Tip Blowing

“…Squealer tips (e.g., see Booth et al [1] and Ameri et al [3]) are commonly used to both reduce leakage and reduce the contact area if rubbing occurs. Winglets as described by Coull et al [4], Zhou et al [5], and O'Dowd et al [6] provide another means to reduce leakage and can be used in combination with squealer cavities. Shrouded airfoils are another alternative.…”

Heat/mass transfer over the plane tip equipped with a full coverage winglet in a turbine cascade: Part 1 – Winglet bottom surface data

“…O'Dowd et al [31] concluded that the turbine blade tip heat transfer is greatly influenced by the shock wave structure inside the tip gap. O'Dowd et al [32] showed that tip Nusselt number increases with coolant injection, and it also increases with increase tip clearance. Coull et al [33] investigated the design of winglet tips for an unshrouded high pressure turbine blade, considering aerodynamic and thermal performance simultaneously.…”

“…Only the suction-side squealer with constant width winglet showed heat transfer reduction by 5.5%. O'Dowd et al [31,32] reported transonic heat transfer over a winglet tip without and with cooling, respectively. It has a centerline gutter and a small recessed cavity on the pressure-side overhang.…”

Heat/mass transfer over the plane tip equipped with a full coverage winglet in a turbine cascade: Part 2 – Tip surface data

“…O'Dowd et al [17] concluded that the turbine blade tip heat transfer is greatly influenced by the shock wave structure inside the tip gap. O'Dowd et al [18] showed that tip Nusselt number increases with coolant injection, and it also increases with increase tip clearance. Coull et al [19] investigated the designs of winglet tips for unshrouded high pressure turbine blade, considering aerodynamic and thermal performance simultaneously.…”

“…Saha et al [16] carried out numerical simulations to explore the effect of a pressure-side winglet on flow and heat transfer over a plane, cavity squealer, and suction-side squealer tips. O'Dowd et al [17,18] reported transonic heat transfer over a winglet tip without and with cooling, respectively. It has not only a centerline gutter but also a small recessed cavity on its pressure-side overhang.…”