Session: 15-05 Rotating Heat Transfer 2

Paper Number: 79846

79846 - Comparison of Experimental and Numerical Local Rotational Heat Transfer Effects in a Two-Pass Cooling Channel Configuration 

Future more efficient aero engines inevitably demand a reduction in turbine blade cooling air consumption. As a consequence of this cooling air saving, however, the contribution of rotation to the overall heat transfer level within the cooling channel gains importance. Therefore, a better understanding of the driving rotational forces and their inherent effects on heat transfer is desired and will result in more room for optimization and increase of the aero engine efficiency.

Rotational effects result in an alteration of the secondary flow field inside the cooling channel. This comprises, on the one side, the Coriolis force, which drives the relatively cold air from the core flow to the hot wall and transports it back along the side walls. On the other side, the density gradient close to the wall is responsible for the hot fluid experiencing a centripetal force known as rotational buoyancy force. Both effects locally induce enhancement or reduction of heat transfer rates.

The subject of the present study is a generic two-pass cooling channel which aims to reproduce the classical flow phenomena in a turbine blade leading edge configuration. It consists of a trapezoidal first pass, a 180-degree bend and a second pass with a rectangular cross-section. Suction side and pressure side are equipped with 60º ribs.

On the experimental side, the transient thermochromic liquid crystal (TLC) technique is utilized in order to evaluate local heat transfer distributions. The evaluation method builds upon the measurement of TLC indication times and fluid reference temperatures after a sudden fluid temperature change in the model is applied. On the numerical side, steady-state simulations (RANS) are performed with the commercial Computational Fluid Dynamics (CFD) software package ANSYS CFX. Temperature, velocity and pressure boundary conditions are derived from the experimental data. A selection of experimental data illustrates the impact of different rotational speeds (Ro) on heat transfer and allows for validation of the numerical model against the experimental results.

Heat transfer results are presented in the form of contour plots of the normalized Nusselt number ratios (rotating to non-rotating case). Moreover, data reduction is performed by means of pixel-histograms and line-averaging of the normalized Nusselt number ratios along the channel walls.

Presenting Author: David Gutiérrez de Arcos Institute of Aerospace Thermodynamics (ITLR)

Presenting Author Biography: Research assistant at the Institute of Aerospace Thermodynamics, Uni Stuttgart

Authors:

David Gutiérrez de Arcos Institute of Aerospace Thermodynamics (ITLR)
Christian Waidmann Institute of Aerospace Thermodynamics (ITLR)
Rico Poser Institute of Aerospace Thermodynamics (ITLR)
Jens von Wolfersdorf Institute of Aerospace Thermodynamics (ITLR)
Bernhard Jäppelt MTU Aero Engines AG