Aerodynamics of a Covered Trailing Edge Vane: Effects of Blowing Rate, Reynolds Number, and External Turbulence

Abstract

A covered trailing edge vane was developed by opening a fully loaded incompressible vane to accept an internal flow passage. The internal passage was filled with a high solidity internal cooling scheme. Exit survey measurements were acquired downstream from a large scale low speed linear cascade test section using a 5-hole cone probe at 1/4 axial chord downstream from the vane trailing edge. Exit survey measurements detailed total pressure loss, turning angle and secondary velocities. Exit survey measurements were conducted across a range of blowing rates (25% to 150% design), Reynolds numbers (500,000, 1,000,000 and 2,000,000) and turbulence levels [low (0.7%), grid (8.5%) and aero-combustor (13.5%)]. Losses for a thickened baseline vane (no blowing, same profile) were also acquired across the Reynolds number range and turbulence conditions. Vane midspan pressure and heat transfer distributions were acquired to help document the state of the boundary layers developing on the vane surface. Measurements are presented in terms of total pressure loss contours with secondary velocities and spanwise distributions of circumferentially averaged losses and turning angles. Overall loss values have been compared with measurements taken using the original base vane and a conventional gill slot vane. Comparisons between the base vane and the covered base vane show an incremental increase in total pressure losses of about 0.95% due the thicker trailing edge. Comparisons between the gill slot (pressure side cutback) and the covered trailing edge vane at comparable flow conditions show a much smaller loss penalty. Loss data for the gill slot vane suggest that both separation off the gill slot lip and the discharge of low momentum fluid are responsible for significant incremental losses above the base vane. The covered trailing edge vane has no additional surface with separation losses which penalizes the aerodynamics. Heat transfer rates for the internal cooling scheme are documented in a separate paper [1].