An experimental and numerical study of the hydrodynamics and surface heat transfer associated with short film cooling holes fed by a narrow plenum
Abstract
To achieve a better understanding of discrete short-hole film cooling performance with counter-flow and co-flow narrow plenums an experimental apparatus was utilized to perform flow visualization studies, surface streak experiments, and quantitative velocity field and surface heat transfer measurements. Complementary 3-D computational fluid dynamics and heat transfer predictions were performed on the same configurations. A better understanding of the role of coherent flow structures in the flow field was achieved by analyzing the experimental results and the numerical predictions. The parameters investigated (blowing ratio, injection angle, and hole length) had significant effects on the film cooling effectiveness and convective heat transfer coefficients realized in the near-hole downstream region of the jets. In many instances systematic trends with the variation of a single parameter in different configurations were not found, indicating that the relative performance of the different film cooling configurations is dependent on a combination of the parameters studied. The film cooling effectiveness and convective heat transfer was related to the effect of the parameter variation on the coherent structures in the flow field. When the combination of parameters causes the jet to lift off the wall, the jet fluid less effectively covers the downstream wall. The crossflow fluid sweeps underneath the jet enhancing the heat transfer coefficient values in the aft region of the jet, and results in poorer net heat flux reduction. In contrast, when the parameters combine to effectively cover the downstream wall (i.e. large spanwise spreading with low trajectory) the effectiveness is increased and the low speed separation region in the downstream region of the jet results in improved film cooling performance. Comparison of the numerically predicted film cooling effectiveness and surface convective heat transfer coefficient with the experimental data indicates that the computational model is still inadequate for making detailed predictions of the convective heat transfer coefficients in the region downstream of the jet. However, the model does a good job of predicting the centerline effectiveness and provides substantial physical insight regarding the mechanisms that lead to the measured results.
Degree
Ph.D.
Advisors
Plesniak, Purdue University.
Subject Area
Mechanical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.