Quasi-steady state mechanism study of a three bypass variable cycle engine fan based on variable outlet guide vane and variable area bypass injector

During high Mach number flight missions, the corrected rotational speed and throughflow capability of aero engines significantly decreases, resulting in insufficient thrust generation. The maintenance of preferable performance across a wide range of rotational speeds presents a challenge for conventional aviation power equipment. To address this issue and achieve wide speed range flight, three-dimensional model of the highthroughflow front and rear fans of a three external bypass variable cycle engine is established, and static pressure is applied at the bypass stream outlet to simulate the rear variable area bypass injector (RVABI) valve opening. The influence mechanism of different stator stagger angles and the RVABI opening on the performance and flow field of the front and rear fans is investigated. The results show that the fan total pressure ratio, isentropic efficiency, and mass flow rate at 58 % corrected rotational speed can be significantly improved by adjusting the stagger angle of the front fan second-stage stator (S2). Notably, the mass flow rate increases by 15.74 % when adjusted by 28 degrees. Furthermore, noticeable variations are observed in the flow field at first stage rotors (R1) and S2. Quantitative analysis shows that the incidence angle in R1 can be effectively decreased by adjusting the S2 stagger angle, which causes a notable decrease in the blade tip load and the mitigation of the leakage flow losses. The S2 blockage is a crucial factor limiting the flow capacity of the turbojet mode, and the blockage and wake losses significantly decrease when S2 is opened. This study elucidates the influence of different stagger angles of S2, combined with variations in RVABI opening, on the aerodynamic performance of the fan, providing valuable insights for selecting key adjusting parameters.