Aero-Thermal Performance of a Winglet at Engine Representative Mach and Reynolds Numbers

Abstract

This paper presents an experimental and numerical investigation of the aero-thermal 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. 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 Performance of Shroudless Turbine Blade Tips with Relative Casing Movement Effects

“…[28]. Further high-speed work led to similar findings on a flat tip by Zhang et al [29], and a winglet tip by O'Dowd et al [30]. Zhang and He [31] further illustrated a tip-shaping technique that would locally accelerate flow to reduce the local heat transfer, based on a concept instigated by He et al [32].…”

“…This observation also holds when the moving casing is applied. This suggests that with respect to heat transfer, the squealer is thermally advantageous over the flat tip, and based on previous research [30], the winglet.…”

“…A common limit to the previous moving casing studies is that they were mainly at low speed conditions. Although there are some preliminary indications of the relative moving casing effects in some recent publications of the authors' group [29], [30], there is a clear lack of analyses for systematic identification and understanding of the impact of relative casing movement and underlined mechanisms.…”

Tip leakage aerodynamics over the cavity squealer tip equipped with full coverage winglets in a turbine cascade

“…They concluded that the mass-averaged loss reductions by installing the winglets are only marginal. Zhou et al (2013) investigated effects of winglet geometry for the winglet tested by O'Dowd et al (2011) on the aerodynamic performance of tip leakage flow in a turbine cascade. They showed that with increasing the radius of the pressure-side edge, the tip leakage mass flow rate and the loss increase.…”

Overtip Choking and Its Implications on Turbine Blade-Tip Aerodynamic Performance

“…Backed up by the experimental results, their virtual Schlieren visualizations in a CFD analysis clearly demonstrated that the stripe variations of heat flux correspond to those flow features associated with the over-tip shock system. Most recently, the over tip choking and shock structure were reported for a shroudless flat tip (Zhang et al [26]), and even a modern winglet tip design (O'Dowd et al [27]). Similar results have also been reported by Shyam et al [28,29] in their numerical study for a highly The present computational analysis using an extensively developed CFD code which has been recently validated for transonic blade tip configurations [25], [26], [31] should shed some light on this primary issue.…”