Fan Stability Enhancement With Partial Casing Treatments

Abstract Casing treatments are used to extend the stability margin of fans or compressors. These typically have an axisymmetric arrangement, but for a fan exposed non-axisymmetric distortion, casing treatment applied fraction annulus is interest target particular distortion feature. In this paper, partial has been designed with axial-skewed slots, and experimental investigation carried out determine effects extent position. Three inlet conditions were tested each treatment: clean, radial tip-low half-annulus distortion. For conditions, stall efficiency penalty increased approximately linearly extent. However, there was strong dependence between position relative distorted sector improvement. If positioned where rotor enters sector, unsteady disturbances in tip flow minimized. if meets later able grow, leading earlier inception. Overall, shows that can give disproportionately positive impact compared full treatment. example, it found 72 deg could be achieve over 50% improvement only 20% penalty.