An Alternate Air System Concept for Application in a High Pressure Turbine

Abstract : In 1995, the German government initiated an aerospace research program in order to support the capabilities of german companies in the more and more challenging environment of aerospace business. Engine 3E is the research part of this overall program concentrating on jet engines. It's aim was to develop technologies to reduce the impact of turbojet engines onto the environment, where 3E stands for Efficiency, Economy and Environment. In this research framework, one of the subprojects concerned the development of a new high pressure turbine (HPT) air system concept, which is presented in this paper. Main objective of the air system itself is provision of sufficient cooling air for the turbine blades on the one hand and sealing of the rim between stator and rotor in the hub area against hot gas ingestion from the annul us on the other hand. The conventional BR700 family HPT air system relies on high pressure compressor (HPC) exit stage bleed air as feed for blade cooling of both HPT stages and rim sealing. An optimized HPT rotor air system has been developed, which uses bleed air of three different HPC stages as feed for blade cooling and rim sealing. This system has the advantage to provide adequate feed pressures for the respective turbine locations. According to the required pressure level HPC exit stage bleed air is used for blade cooling of the first HPT rotor and rim sealing in front of rotor 1. Lower stage bleed air is fed through external pipes through the HPT stage 2 vanes for rim sealing in front of and behind the HPT stage 2 vanes. Bleed air of an even lower HPC stage is used for ventilation of the inner interstage cavity and blade cooling of the second stage rotor blades. The optimized HPT air system concept additionally features a new secondary preswirl system with a brush seal and a mini disc in the interstage cavity. The mini disc is introduced to separate bleed air of different stages inside the interstage cavity. The whole concept