Spatially-resolved measurements of heat transfer in turbomachinery applications.

摘要

Most turbomachinery environments are characterized by high temperatures and highly complex flow conditions. Spatially-resolved data are necessary for the design of turbomachinery components, to identify regions of high heat loads and thermal stresses so that coolant resources can be distributed effectively. This research is dedicated toward improving experimental techniques used in the design of engine hardware.; The first phase of the research quantifies how a sharp, short step in wall temperature impacts the local convective heat transfer. The problem has implications for improving data interpretation for button-type heat flux gages, commonly used in transonic blowdown facilities. Experiments with appropriately-scaled one- and two-dimensional calorimeters were conducted in a low speed wind tunnel facility. Low and high freestream turbulence conditions were studied. The results indicate that spanwise diffusion is not significant and that the heat transfer is largely two-dimensional. A 2-D boundary layer code, STAN7, was validated by the experimental results and employed in numerical simulations of button-type gage heat transfer. The calorimeter results also led to the development of a new heat transfer correlation that provides greatly improved accuracy near the wall temperature step, relative to existing closed-form solutions.; The second part of this work shifts from single-point to full-field measurements. Adiabatic film cooling effectiveness (η) and heat transfer coefficient (h) data were obtained in a two-dimensional model of a single passage of a turbine cascade, under subsonic conditions. Wideband thermochromic liquid crystal paint was used for full-field imaging. The η data were acquired over a range of injection, or blowing, conditions, using a single row of simple-angle round holes. Full-field h data were acquired with a uniform heat flux boundary condition. Significant heat transfer augmentation was observed in the near-injection region for situations with blowing.; The Discrete Green's Functions (DGF) methodology was extended to the single passage model, incorporating significant curvature in a realistic geometry. The DGF concept is superposition-based and provides a general description of heat transfer that is independent of the thermal boundary conditions. The agreement between one-dimensional DGF predictions and the uniform heat flux data was very good. The DGF approach shows promise as a technique for measuring heat transfer in turbomachinery applications.