Influence of a Stream wise Pressure Gradient on Film-Cooling Effectiveness

摘要

Film cooling is widely used in conventional gas turbine and rocket engines to minimize thermal loading of engine structures and to manage heat transfer between hot, reacting gases and cooler structural components. Previous experimental work has shown that streamwise pressure gradients strongly influence the performance of the film. This paper extends semi-empirical modeling ideas for wall-jet film cooling to include the effects of adverse and favorable pressure gradients. The extended model shows that a pressure gradient's effect on cooling performance depends on whether the velocity of the film is greater than the core flow (a wall-jet film) or less than the core (a core-driven film). In wall-jet films, a favorable pressure gradient improves cooling performance by increasing the thickness and persistence of the film. Conversely, in core-driven films, a favorable pressure gradient reduces the persistence and thickness of the film leading to reduced cooling performance. Under isobaric conditions, the extended model results match experimental measurements within 2.5% in the near-slot region. When pressure gradients are present, the extended model matches experimental data to within 15 % in the near-slot region and correctly predicts experimentally observed trends.