An aerodynamic design method was proposed for core driven fan stages on balances of the single and double bypass modes. Combining the S2 stream surface through-flow calculation with a genetic algorithm

the optimal inlet guide vane (IGV) outlet angle

closed angle and pressure ratio distributions in the two modes along the blade spans were found

achieving the balance on the rotor aerodynamic design. The key geometric parameters of the variable IGV were determined according to the study on the influences of the IGV profile camber and installation angle on flow losses in the two modes

achieving the balance on the IGV design. The stator blade design was conducted by using multi-point optimization method

achieving the balance on the stator aerodynamic design. Three-dimensional flow fields of a designed core driven fan stage were numerically simulated

and the results showed that the isentropy efficiency at the design point reached 88.05% and 87.17% in single and double bypass mode

respectively under the premise of satisfying the total pressure ratio and mass flow rate in two modes

and the stability margins in the two modes reached 15.65% and 16.28%

respectively.