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Handbook of Turbomachinery Second Edition Revised - Ventech!

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Figure 7 Development process for cooled turbine airfoil.<br />

current engineering using a three-dimensional (3D) database for solid<br />

modeling, flow, heat transfer, and mechanical analyses. Solid modeling gives<br />

a comprehensive graphical representation <strong>of</strong> the most intricate component<br />

geometry.<br />

The calculation <strong>of</strong> the local component heat-transfer coefficients is<br />

based on defined boundary conditions around external and internal surfaces<br />

<strong>of</strong> the airfoil. Existing computational fluid dynamic codes for the mainstream<br />

flow (<strong>of</strong>ten 3D), correlations and flow codes (<strong>of</strong>ten 1D or pseudo-<br />

3D) for the internal flows through the cooling passages establish these<br />

boundary conditions. Iterative thermal analyses <strong>of</strong> the airfoil are usually<br />

performed, combining the heat-transfer data, physical properties <strong>of</strong> the<br />

alloy, and thermodynamic parameters <strong>of</strong> the main-stream and cooling flows,<br />

until the required metal temperatures are satisfied. Effects <strong>of</strong> free-stream<br />

turbulence, secondary flows, and rotation (for the blades) are essential for<br />

meaningful results <strong>of</strong> the thermal analyses.<br />

The expected radial temperature pr<strong>of</strong>ile <strong>of</strong> the main-stream flow is<br />

applied as input for the turbine blade analysis. The circumferential peak<br />

temperature (hot-spot) in a nonuniform combustor temperature pattern<br />

factor is used as the boundary condition for the nozzle vane temperature<br />

prediction. Analytically predicted airfoil temperatures are interpolated<br />

within the computer solid model and applied as input for mechanical<br />

analysis.<br />

Copyright © 2003 Marcel Dekker, Inc.

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