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Abstract This paper reports on the evolution of fan aerodynamics starting with turbofan engines featuring moderate by-pass ratios (between 4 and 6) up to Ultra-High-By-pass-Ratio (UHBR) configurations which are currently being developed. The implementation of key enabling technologies for fan blades are discussed from a historical perspective, spanning from high-aspect ratio fan blades with part span shrouds (or snubber) to wide chord fan blades, from un-ducted (UDF) and propfan open rotors to highly swept blades. With continuous requirements for higher thrust and lower fuel consumption, bypass ratio demand has also increased leading to UHBR configurations (by-pass ratios higher than 13). Almost all engine companies have responded to these challenges by reducing the number of fan blades. To meet future performance and stability requirements of lower fan pressure ratios, new fan architectures are discussed.
Benini et al. (Mon,) studied this question.