Redistribution of Purged Cavity Air Inside a Turbine Exit Vane Frame due to the Interaction With the Main Airflow

As a consequence of enhanced pressure ratios and combustion exit temperatures for higher jet engine efficiencies, the exit temperature of the Low Pressure Turbine (LPT) increases, too. To prevent hot gas from entering the rim seal cavity between the LPT's last stage rotor and the Turbine Exit Vane Frame (TEVF), purge air is needed. The present work investigates the spatial redistribution of purged cavity air inside an annular Turbine Exit Vane cascade due to its interaction with the main airflow. For this purpose, experimental investigations have been conducted using aerodynamic 5-hole pressure probes and the CO2 trace gas technique. Furthermore, numeric results yield better insights into the flow's characteristics. Three operating conditions are investigated, representing the aircraft's states: take-off, maximum climb, and cruise. It is shown that the interaction between the purge fluid and main airflow is mainly dominated by the ingress upstream of the vane's leading edge and the egress at locations of lower static pressure. Inside the vane passage, the cross-flow pressure gradient mainly determines the cavity fluid's pathway. At off-design conditions, purge fluid does not contribute significantly to the cascade's total pressure loss.