Aeroelastic analysis of a contra-rotating fan for a high bypass ratio engine

Abstract

Engine design for modern civil transport aircraft is required to achieve noise reduction coupled with high fuel efficiency. The use of contra-rotating fan in high bypass ratio turbofan engines is aimed at providing significant improvement in the reduction of carbon dioxide emissions and noise levels in addition to the increase in propulsive efficiency and wider stall-free operation. In the present work, the flutter characteristics of a contrarotating fan blisk for a high bypass ratio engine have been computationally investigated. Unsteady time domain simulations have been performed for each blisk separately for two different operating speeds to get the flutter predictions. The predicted aerodynamic damping for different interblade phase angles shows that the fan configuration is stable for the speeds investigated. The presence of shock does not have an adverse effect on the unsteady surface pressure. It is the phase rather than the amplitude of the first harmonic unsteady surface pressure that influences the damping behaviour.