Effects of Upstream Step Geometries on Endwall Film Cooling and Phantom Cooling Performances of a Transonic Turbine Vane

Abstract

This paper presents a detailed experimental and numerical study on endwall film cooling and vane pressure side surface phantom cooling at simulated realistic gas turbine operating conditions (high inlet freestream turbulence level of 16%, exit Mach number of 0.85 and exit Reynolds number of 1.7×106). The experiment measurements were conducted at Virginia Tech's transonic blowdown wind tunnel for two configurations: baseline cascade (HR = 0 mm) and forward-facing step geometry (HR = -5 mm). The numerical predictions were performed by solving the steady-state Reynolds Averaged Navier Stokes (RANS) with Realizable k-e turbulence model. Based on a double coolant temperature model, a novel numerical method for the predictions of adiabatic wall film cooling effectiveness was proposed. The qualitative and quantitative comparisons between the numerical prediction results and experiment data are provided in this paper. The results indicate that this method can reliably predict endwall film cooling distributions and vane pressure side surface phantom cooling distributions, and significantly reduce (more than 50%) numerical prediction errors. The effects of upstream step geometries were numerically studied at the design flow conditions (BR = 2.5, DR=1.2), by quantizing the endwall film cooling effectiveness, vane pressure side surface phantom cooling effectiveness and total pressure loss coefficients (TPLC) for various upstream step heights: three forward-facing step heights (HR = −8, −5, −3 mm), a baseline cascade (HR = 0 mm), and four backward-facing step heights (HR = 3, 5, 6.78, 10 mm).