The effect of sweep on flowfields of a highly loaded transonic rotor

A new view of internal blade loading match is employed in this paper to reveal the essential relationship between sweep and complicated flow phenomenon in compressors. A forward swept rotor named as SF and an aft swept rotor named as SA, are designed originating from NASA Rotor 37. The numerical results indicate the isentropic efficiency and total pressure ratio of the new rotor with forward sweep are a little larger than rotor Baseline at peak efficiency point, and its stall margin has an over 10% increase as well. By contrast, the opposite change appears in the aft swept rotor SA. In addition, the choking massflow of swept rotors changes clearly as a result of the spatial change of aerodynamic throat and the forward sweep produces a larger throat area and choking massflow. A noted phenomenon is shown that both forward and aft sweep benefit a certain range of blade span for flow characteristic improvement, and the sweep also affects the inflow condition, 3-D shock structure and internal loading distributions of swept rotors. Both the new radial equilibrium in flowfield and transportation of low-energy fluids in boundary layer induced by sweep appear conductive to reduce shock wave and flow blockage in tip region of forward swept rotor SF. Meanwhile, the strength of leakage flow is also suppressed in the forward swept rotor SF because of the decreased blade loading near leading edge in tip region. In fact, all the change in swept rotors tends to be a new characteristic match of blade airfoil at different span, and the re-matching of flow characteristic for blade airfoil determines the stable operation range and the overall performance of swept rotors at design point directly.