Influence of a Streamwise 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 enginenstructures and to manage heat transfer between hot, reacting gases and cooler structural components. Previousnexperimental work has shown that streamwise pressure gradients strongly influence the performance of the film.nThis paper extends semi-empirical modeling ideas for wall-jet film cooling to include the effects of adverse andnfavorable pressure gradients. The extended model shows that a pressure gradient’s effect on cooling performancendepends on whether the velocity of the film is greater than the core flow (a wall-jet film) or less than the core (a core-ndriven film). In wall-jet films, a favorable pressure gradient improves cooling performance by increasing thenthickness and persistence of the film. Conversely, in core-driven films, a favorable pressure gradient reduces thenpersistence and thickness of the filmleading to reduced cooling performance.Under isobaric conditions, the extendednmodel results match experimental measurements within 2.5%in the near-slot region.When pressure gradients arenpresent, the extendedmodelmatches experimental data to within 15%in the near-slot region and correctly predictsnexperimentally observed trends.