Cantilevered stator hub leakage flow control and loss reduction using non-uniform clearances

Hub leakage flow between the cantilevered stator and the hub wall is responsible for the deficit of stator aerodynamic performance, and the interaction between the leakage and main flows leads to leakage vortex and flow blockages in the hub region, thus deteriorating the stator or even the compressor performance. The paper conducts a numerical investigation on the influence of non-uniform clearances on the stator aerodynamic performance in a 1.5-stage axial-flow compressor. The main purpose is to find an aerodynamically preferable clearance shape to control the leakage flow and the associated aerodynamic losses. The clearance shapes considered include uniform, expanding and shrinking clearances from blade leading edge to trailing edge. The computed results show that, compared with the uniform clearance, the expanding clearance has powerful effect on weakening the leakage flow near the leading edge and also has better inhibition of the leakage vortex, thus achieving aerodynamic benefits gain in the hub region. But the shrinking clearance has the opposite effect on the leakage flow and leads to more losses than the uniform clearance. In addition, the overall aerodynamic loss of the stator with the expanding clearance is reduced with the increment of the clearance expansion ratio.