Aeropropulsion for Commercial Aviation in the Twenty-First Century and Research Directions Needed

Two driving imperatives of 21st century commercial aviation are improving fuel consumption and reducing environmental impact. The research important to aeropropulsion’s advancing these goals is shaped both by physics of the design space and by design choice. As fuel becomes increasingly more expensive, engine architectures and design details evolve to reflect the new balance between engine fuel consumption, weight, and manufacturing and maintenance costs. The evolution of engine architectures changes the relative value of specific technologies. The engines of the future will be advanced gas turbines due to their superior fuel burn at the aircraft level. They will be fueled by sustainable liquid hydrocarbons. Both the thermal and propulsive efficiency of the gas turbine can be significantly improved. The need to improve propulsive efficiency has driven engine bypass ratio up, to 12 recently, and higher in the future. This is a different, less familiar design space than the 5 to 8 bypass ratio, which characterized the last 40 years of engine experience. Realignment of research priorities is required to address 21st century challenges, such as the knowledge needed to realize efficient engines at very small core sizes. The new challenges open up new opportunities for both designers and researchers.