Desensitization of Axial Compressor Performance and Stability to Tip Clearance Size

This paper presents a computational and analytical study to identify and elucidate fundamental flow features associated with the desensitization of performance and aerodynamic stability of an axial compressor rotor to tip clearance change. Parametric studies of various design changes to a baseline double circular arc airfoil axial rotor led to the identification of two flow features associated with reducing sensitivity to tip clearance, namely, high incoming meridional momentum in the tip region and reduction/elimination of double tip leakage. Numerical experiments were subsequently performed on the baseline rotor geometry to validate these two flow features and explain the associated flow physics by variations in incoming meridional momentum and pitch size. Finally, two designs were proposed, namely, a full forward chordwise sweep (FFCS) rotor and a rotor with gradual stagger angle reduction in the outer span, to exploit these flow features. The results indicated that both designs produce the intended flow effects and exhibit lower sensitivity of performance and aerodynamic stability to tip clearance.