Alan Epstein, VP of Technology & Environment at Pratt & Whitney talks about Aeropropulsion for Commercial Aviation in the 21st Century and Research Directions Needed Two driving imperatives of 21st century commercial aviation are and will be 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 will change 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 improved. The need to improve propulsive efficiency has driven fan pressure ratio down and therefore bypass ratio (BPR) up, to 12 BPR recently, and this need will drive BPR higher in the future. This is a different, less familiar design space than the 58 BPR which characterized the last 40 years of engine experience, with different needs and constraints. Realignment of research priorities is required to address 21st century challenges, dropping some topics and introducing new ones. One imperative is the research to extend the design space for narrowbody aircraft engines to what are now considered very small core sizes. The new challenges open up new opportunities for both designers and researchers.