Surface heat transfer characteristics of a transfer turbine blade with pressure side film cooling and different tip gaps
Date of Award
Master of Science in Engineering (MSE)
Mechanical and Aerospace Engineering
Turbomachines--Blades--Aerodynamics, Turbomachines--Blades--Fluid dynamics
Investigated are spatially-resolved distributions of surface adiabatic film cooling effectiveness and surface heat transfer coefficients for a transonic turbine blade tip. The tip contains a squealer rim, and a single row of film cooling holes is located on the pressure-side of the blade very near to the blade tip. As such, a unique pressure side film cooling arrangement is tested to provide a better understanding of thermal protection of turbine blade tips, as they are exposed to a complex and challenging flow environment. A two-dimensional linear cascade, with four flow passages and five complete blades, is employed, which is designed to provide geometric similarity to components with an operating gas turbine engine. Also measured are surface static pressure distributions, and associated isentropic Mach numbers, around the blade surface at the 50 percent airfoil span location, around the blade surface at the 90 percent airfoil span location, and along the surface of the blade tip. Spatially resolved heat transfer coefficient distributions are presented for a baseline blade without film cooling for tip gaps of 0.8 mm and 1.4 mm. Spatially-resolved distributions of surface adiabatic film cooling effectiveness and surface heat transfer coefficients are also provided for different film cooling flow conditions for two different tip gaps of 1.4 mm and 0.8 mm. Significant variations in surface thermal protection and film cooling coverage are present along the transonic turbine blade, as the blowing ratio varies, as surface location changes, and with changes in tip gap. Experimentally- measured, spatially-resolved surface heat transfer coefficient data and adiabatic film cooling effectiveness data demonstrate that improved surface thermal protection on the squealer tip surface is provided with a smaller tip gap. Comparing smaller tip gap data, relative to values associated with the larger tip gap, such a conclusion is illustrated by heat transfer coefficient values at each surface location which are generally lower, and by adiabatic film cooling effectiveness magnitudes which are substantially larger. Significant variations of heat transfer coefficient with blowing ratio are also present, especially for locations near to film cooling hole locations, where evidence of a horse-shoe shaped vortex structure is provided around each film cooling jet, regardless of tip gap magnitude.
Collopy, Hallie, "Surface heat transfer characteristics of a transfer turbine blade with pressure side film cooling and different tip gaps" (2020). Theses. 401.
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