On the Potential to Eliminate Turbine Cooling in High-Efficiency Gas Turbine Engines through the Application of Wave Rotor Technology

This research investigates the application of wave rotors to gas turbines, specifically with regards to their potential to remove or reduce requirements for turbine cooling. This concept is conceivable because, while the wave rotor functions as a dedicated high-pressure spool itself, it is internally self-cooled and operates at approximately the average temperature of the two gas streams entering it. Since the expansion of the hot gases in the wave rotor directly drives the compression of the air received from the compressor, the gases leaving the combustor are cooled by doing useful work within the device. The hot gases leaving the wave rotor can then be expanded conventionally to produce either shaft power or thrust. This paper shows that for large, highly-efficient gas turbines, despite wave rotors exhibiting lower isentropic efficiency than aerodynamic turbomachinery, any potential disadvantages can be offset through the removal of the losses associated with turbine cooling. Five different high-bypass ratio turbofan engines were modelled: a baseline and four incorporating wave rotors in various configurations. The results show that, for a combustor outlet temperature of 1500 K, a single stage of wave rotor can replace a conventional turbine stage and thus remove the associated cooling requirements. This arrangement is also capable of producing more thrust. Furthermore, for two stages of wave rotor in a “cascaded” arrangement, two turbine stages can be removed and thus most of cooling requirement can be completely eliminated, with obvious potential benefits in terms of turbine cost. Depending on the efficiency of the devices employed, this embodiment can also produce the most thrust of all the architectures investigated. It is concluded that cascaded wave rotor technology provides an avenue for gas turbine engine development which could simultaneously increase efficiency, reduce fuel burn and CO2 emissions, and reduce the capital and operating cost of aero engines.