NUMERICAL INVESTIGATIONS ON STATIC AND ROTORDYNAMIC CHARACTERISTICS FOR TWO TYPES OF LIQUID HOLE-PATTERN SEALS WITH TILTED CAVITIES

Abstract

Two types of liquid hole-pattern seals with axially-oblique (A-HPS) or circumferentially-oblique (C-HPS) hole cavities are designed. To evaluate the leakage and rotordynamic characteristics of the liquid hole-pattern seals, a 3D transient perturbation method is employed, which based on the multi-frequency one-dimensional rotor whirling model and the mesh deformation technique. The accuracy and reliability of the proposed numerical approach is demonstrated based on the published experimental data of the leakage and rotordynamic force coefficients for a hole-pattern seal (HPS). Seal leakage and force coefficients are presented and compared for the A-HPS (axially-oblique angle α = −30° −30°), C-HPS (circumferentially-oblique angle β = −30° − 30°), and HPS (α = 0, β = 0) at various rotational speeds (n=0.05, 2.0, 4.0, and 6.0 krpm). Results reveal that the tilted hole cavity with positive α or β can reduce the seal effective clearance and strengthen the kinetic dissipation in hole cavities, yielding less leakage by 5%-10%, especially at higher rotational speeds. The tilted hole cavity with a positive oblique angle (α = 30°, β = 30°) results in a moderate growth (by ~6% for the A-HPS, by ~15% for C-HPS) in the effective stiffness. Further, the tilted hole cavity shows a very weak influence (< 4.0%) on the effective damping, particularly for higher rotational speeds and vibration frequencies. Considering the decreasing leakage and non-worse rotordynamic characteristics, a tilted hole cavity with suitable positive oblique angles (10°~30°) is beneficial for the liquid hole-pattern seal.