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

Abstract

This paper presents an experimental and numerical investigation of the aerothermal performance of an uncooled winglet tip, under transonic conditions. Spatially resolved heat transfer data, including winglet tip surface and near-tip side-walls, are obtained using the transient infrared thermography technique within the Oxford high speed linear cascade test facility. Computational fluid dynamics (CFD) predictions are also conducted using the Rolls-Royce HYDRA suite. Most of the spatial heat transfer variations on the tip surface are well-captured by the CFD solver. The transonic flow pattern and its influence on heat transfer are analyzed, which shows that the turbine blade tip heat transfer is greatly influenced by the shock wave structure inside the tip gap. The effect of the casing relative motion is also numerically investigated. The CFD results indicate that the local heat transfer distribution on the tip is affected by the relative casing motion but the tip flow choking and shock wave structure within the tip gap still exist in the aft region of the blade.

Aerothermal characteristics of a transonic tip flow in a turbine cascade with tip clearance variations

“…Zhang et al [10] reported the detailed experimental evidences of the heat transfer stripe distributions caused by the shock wave structures over the blade tips. Most recently, the overtip choking and shock structures [11] as well as its effects on tip heat transfer [12] were reported by Zhang et al and for even a modern winglet-tip design by O'Dowd et al [13].…”

“…However, for cases with strong shock waves, the convergence level becomes worse, but still better than 1×10 -3 . All the 13 results have been checked for convergence by using blade tip surface average heat transfer coefficient monitoring, and the solution is said to be converged when the average heat transfer coefficient is not changed more than 0.05% during 100 successive iterations.…”

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

“…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

“…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.…”

“…It has not only a centerline gutter but also a small recessed cavity on its pressure-side overhang. 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.…”