Impact of Rotor-Casing Effusion Cooling on Turbine Performance and Operating Point: An Experimental, Computational, and Theoretical Study

Abstract It is known that a secondary effect of rotor-casing effusion cooling to modify and potentially spoil the rotor over-tip leakage flow. Studies have shown both positive negative impacts on high-pressure (HP) stage aerodynamic performance heat transfer, although there remains no consensus whether net beneficial when thermal effects are accounted for simultaneously. An has not been extensively discussed in literature change operating point arises due mass introduction midway through machine. This complicates analysis true impact turbine must be an assessment overall benefit such system. In this paper, we develop low-order (“mean-line”) attempt bring clarity issue. We then present results from experiments conducted Oxford Turbine Research Facility, 1.5-stage transonic rotating facility capable matching non-dimensional engine conditions. experiments, was implemented over sector casing spanning 24 degrees or four rotor-blade pitches. Rotor-exit radial traverse HP vane loading measurements were locally cooled sector. Results compared baseline tests without cooling. To assess degree which experimental with only annulus would provide accurate indication changes (when measured local annulus) annular (engine-like) environment, unsteady Reynolds-averaged Navier–Stokes (URANS) simulations performed. particular, full effusion-cooled periodic simulation fully The results—perhaps surprisingly—suggest sufficient infer system, provided performed Experiments fixed boundary conditions showed increases mid-stage static pressure stage-exit total mean-line model URANS predictions good agreement data also increase reaction reduction turbine-inlet (mainstream) flowrate Finally, used show cooling, (changes tip-leakage flow structures) globally bulk-flow velocity triangles). absolute efficiency 0.7% predicted coolant-to-mainstream ratio 2.2%. By running number different conditions, steady RANS estimate relative contributions improvement aerodynamics blade-tip region. For configuration, contribute positively efficiency.