Role of tip leakage flow in an ultra-highly loaded transonic rotor aerodynamics

Tip clearance size is a very critical design parameter for the modern transonic rotor. This investigation attempts to reveal the role of tip leakage flow in an ultra-highly loaded low reaction transonic rotor (loading coefficient equals to 0.782) aerodynamics. Flow fields in the rotor with varied tip clearance sizes, ranging from 0 to 3 times of the datum case, are discussed at length. Both performance variation and stall mechanisms involved are elaborated. As a result, the rotor performance presents a continuous decline with the increased tip clearance size as a result of the additional secondary flow loss induced by the tip leakage flow. While for stall margin, an optimal tip clearance size exists, and it happens to be the datum case. The tip leakage flow is found to have the ability to blow away the low-energy flow accumulated in the rotor tip suction side. Specially, the forward portion of tip leakage flow plays the dominate role in extending the rotor stall margin. However, as the tip clearance size exceeds the datum case, the shock-tip leakage vortex interaction causes the tip leakage vortex breakdown and the stall margin is hence narrowed.