Comparison of flutter characteristics of forward/ backward swept fan blades

The effects of mode shape and inter blade phase angle(IBPA) on aeroelasticity stability of forward and backward swept blades were investigated through numerical flutter analysis and comparison based on the energy method. Results show that, for the first three vibration modes, aerodynamic modal damping ratio(AMDR) of forward swept blades corresponding to the coupling mode has the highest value of 0.801%, and that of backward swept blades corresponding to the coupling mode has the lowest value of 0.248%. IBPA has significant effects on AMDR for two kinds of swept blades. AMDR corresponding to forward travelling wave is lower than that corresponding to backward travelling wave for forward swept blades vibration in the 1st flapping mode at the same IBPA, while it is contrary for the backward swept blades; forward swept blades have better aeroelasticity than backward swept ones at arbitrary IBPA when blades vibrate in the 1st flapping mode.