Effects of Precooling Turbine Cooling Air on Engine Performance

Abstract

Approaches to improving gas turbine cycle efficiency by cooling the compressor discharge air used for turbine cooling are explored. From a turbine cycle standpoint, cooling the coolant air can improve cycle efficiency. A significant improvement in specific fuel consumption is achieved by raising the turbine rotor inlet temperature, and engine pressure ratio. Precooling compressor discharge air can enable rotor inlet temperature to increase up to 100 K at the same rotor cooling flow rate ratio. The efficiency gains from a 100 K rise in rotor inlet temperature translated into a fuel savings of 400 kg for a mission length of 5450 km. This fuel savings means about a 1200 kg savings in CO2 production. Compressor discharge air that passes through a heat exchanger may not have enough pressure to prevent hot gas ingestion through the cooling holes of the high pressure turbine stator. A stator analysis assuming a mixture of precooled and uncooled compressor discharge air showed only a 50 K rise in rotor inlet temperature due to precooling at the same cooling flow rate ratio.