Effect of blade angle design selection on wave-turbine engine performance
Wave rotors have been investigated over several decades in part due to their potential for increasing the maximum cycle temperature in gas turbine engines via their self-cooling mechanism. Recent activities in this field have centered on the experiments and CFD design tools developed at NASA Lewis Research Center. Because of the fundamental objectives of that program, the work to date has concentrated on wave rotors rather than wave turbines. Wave turbines differ from wave rotors in that the flow passages are curved, similar to conventional turbines, so that the unit produces net shaft power. The purpose of this paper is to present an analysis technique which is used to quantify the substantial impact which blade curvature has on the maximum gas expansion ratio, and hence on the maximum cycle temperature. Limited optimization of the overall pressure ratio allows the maximum specific power and the corresponding efficiency to be found as a function of wave turbine inlet and exit blade angles and Mach number. A potential increase in specific power of 69% and a 6.8 percentage point increase in thermal efficiency over a conventional gas-turbine engine can be achieved through the use of a wave turbine.