Aerodynamic and heat transfer characteristics of a transonic turbine blade tip with pressure-side film cooling
Date of Award
Master of Science in Engineering (MSE)
Mechanical and Aerospace Engineering
Turbomachines--Blades--Aerodynamics., Turbomachines--Blades--Fluid dynamics.
Currently, there is a deficit of experimental data for surface heat transfer characteristics and thermal transport processes associated with tip gap flows, and a lack of understanding of performance and behavior of film cooling as applied to blade tip surfaces. As a result, many avenues of opportunity exist for development of creative tip configurations with innovative external cooling arrangements. Described is the development of experimental facilities, including a Supersonic/Transonic Wind Tunnel and a linear cascade for investigations of aerodynamics and surface heat transfer characteristics of a transonic turbine blade tip with a unique squealer geometry and an innovative film cooling arrangement. Of interest is development of a two-dimensional linear cascade with appropriate cascade airfoil flow periodicity. Included are boundary layer flow bleed devices, downstream tailboards, and augmented cascade inlet turbulence intensity. The present linear cascade approach allows experimental configuration parameters to be readily varied. Tip gap magnitudes are scaled so that ratios of tip gap to inlet boundary layer thickness, ratios of tip gap to blade axial chord length, and ratios of tip gap magnitudes to blade true chord length match engine hardware configurations. Ratios of inlet boundary layer thickness to tip gap range from 3 to 5. An innovative, compound angle film cooling configuration is utilized for one blade tip configuration. With these experimental components, results are presented for engine representative transonic Mach numbers, Reynolds numbers, and film cooling parameters, including density ratios, which are achieved using foreign gas injection with carbon dioxide. Transient, infrared thermography approaches are employed to measure spatially-resolved distributions of surface heat transfer coefficients, adiabatic surface temperature, and adiabatic film cooling effectiveness. Presented are experimental measurements and spatially resolved surface distributions of dimensional heat transfer coefficient, heat transfer coefficient ratio, and different types of adiabatic film cooling effectiveness. These results show differing behaviour depending on the film cooling flow condition, including film cooling blowing ratios which are varied from 0.49 to 3.85. These data also show significant variations spatially along the surface including along the suction side squealer rim, along the pressure side squealer rim, and within the squealer recess region. Film cooling effectiveness data at these locations increase to values as high as 0.08 for blowing ratios of 2.01, 3.18, and 3.85. With a blowing ratio of 3.18, the heat transfer coefficient data varied as much as 30 percent relative to the baseline data with no film cooling.
Sampson, Michael, "Aerodynamic and heat transfer characteristics of a transonic turbine blade tip with pressure-side film cooling" (2020). Theses. 365.