Prediction of High-Pressure Turbine Main-/Secondary-Air System Flow Interaction

The results from a steady, viscous flow simulation of the main flowpath of a modern jet engine transonic highpressure turbine, transition duct, and first vane of the low-pressure turbine, coupled with the secondary-air system under the high-pressure turbine, is presented. The secondary-air system configuration includes the lower cavity near the centerline, the mid-cavity with the tangential onboard injection nozzle and pump, and the upper rim cavity. In addition, the flow through the inner tangential onboard injection seal and labyrinth seals that separate the cavities is included. The purpose of this investigation is to determine the feasibility of the use of computational procedures to predict the steady-flow interaction effects between the mainand secondary-air system flow, the ability to predict flow splits in the secondary-air system, and the numerical issues associated with such a computation. A description of the numerical procedure, along with technical details of the initial and boundary conditions and convergence of the numerical procedure are presented. Details of the predicted flow physics in the secondaryair system flowpath, including the rim-cavity and inner tangential onboard injection/labyrinth seals, the main flowpath, and the interaction region at the junction between the two flowpaths are presented. The effect of the secondary-air system flow on the aerodynamic performance and hub endwall temperature distribution of the main flowpath blade rows is also discussed.