Flow mechanisms of primary vortex structures in a novel high-throughflow fan concept with a partial-span tandem rotor

Due to the constraints faced in enhancing modern aero-engine throughflow capacity, a novel concept of a high-throughflow fan has emerged. This study applies the Ω vortex identification criterion to systematically investigate the vortex structure and evolution mechanisms in a partial-span tandem rotor comprising a partial-span booster rotor and a fan rotor. The horseshoe vortex and passage vortex are identified at the hub of both rotors. Due to the Kutta condition, the trailing edge of the fan rotor experiences strong unloading, generating a corner vortex, a tornado-like vortex, and a reattachment vortex in the corner region. At the tip of the partial blade height booster rotor, a unique open-leakage flow is generated due to pressure differences. This flow entrains the radial vortex and some of the mainstream fluid along its path, resulting in the formation of the tip vortex. In addition to the blade tip leakage vortex at higher blade heights of the fan rotor, radially migrating fluid exists behind the strong passage shock wave, leading to the formation of a radial vortex. This, in turn, causes a shock wave along the flow direction at the blade tip of the fan rotor. The shock wave further induces the intertwining of the leakage fluid near the trailing edge with the mainstream, forming an induced vortex. Based on the formation and development mechanisms of these vortex structures, this paper constructs the corresponding vortex model, which lays a theoretical foundation for the subsequent fine flow control of the new high-throughflow fan configuration.