Heat Transfer in High-Speed Rotating Trapezoidal Duct With Rib-Roughened Surfaces and Air Bleeds From the Wall on the Apical Side

Abstract

An experimental study of heat transfer in a radially rotating trapezoidal duct with two opposite walls roughened by 45deg staggered ribs and bleed from the apical side wall is performed. Centerline heat transfer variations on two rib-roughened surfaces are measured for radially outward flows with and without bleeds at test conditions of Reynolds number (Re), rotation number (Ro), and density ratio (Δρ∕ρ) in the ranges of 15,000–30,000, 0–0.8, and 0.04–0.31, respectively. Geometrical configurations and rotation numbers tested have considerably extended the previous experiences that offer practical applications to the trailing edge cooling of a gas turbine rotor blade. A selection of experimental data illustrates the individual and interactive influences of Re, Ro, and buoyancy number (Bu) on local heat transfer with and without bleeds. Local heat transfer results are generated with the influences of bleeds on the apical side examined to establish heat transfer correlations with Re, Ro, and Bu as the controlling flow parameters for design applications. The rotation of present trapezoidal duct with rib-roughened surfaces and air bleeds on the apical side worsens the impairing heat transfer impacts due to bleeds. Within the Ro range of 0.1–0.8, bleeds on the apical side of the rotating channel respectively produce 25–50% and 25–40% of heat transfer reductions from the rotational no-bleed references along the leading and trailing centerlines. Such heat transfer reductions due to the combined bleeds and Ro-Bu impacts need design precautions for turbine rotor blades.