Boundary Layer Control of an Annular Turbine Cascade

Abstract

Blade Reynolds numbers for the turbine stage of small and micro gas turbine engines can drop below 10^5. At these low Reynolds number conditions, the boundary layer is dominated by laminar flow and is susceptible to flow separation, which is associated with increased loss and reduced performance. This paper describes the effect of boundary layer trip on an annular turbine cascade under very low Reynolds number conditions, Re_<out>= 4.4×10^4〜22.8×10^4. The free-stream turbulence intensity was varied between 0.5% and 8.9%. The velocity and turbulence intensity at the exit of the turbine cascade were measured using a single-element hot-wire anemometry for both "with trip" and "no trip" blades. Effect of the trip was concentrated at the blade hub region because of the three-dimensional flow fields. The effect of trip gradually decreased with increasing turbulence intensity.