A Numerical Study on the Influence of Hole Depth on the Static and Dynamic Performance of Hole-Pattern Seals

Abstract

Annular seals serve an important role in the dynamics of turbomachinery by reducing leakage of a process fluid while also contributing potentially destabilizing forces to the rotor system. Hole-pattern seals have been the focus of many investigations, but recent experimental studies have shown that there are still many phenomena that require exploration. One such phenomenon is the influence of hole depth on the static and dynamic characteristics of the seal. In this paper, a hybrid computational fluid dynamics (CFD)/bulk-flow method is employed to investigate the nonmonotonic relationship between hole depth and leakage shown in experimental measurements of a hole-pattern seal by Childs et al. (2014, “The Impact of Hole Depth on the Rotordynamic and Leakage Characteristics of Hole-Pattern-Stator Gas Annular Seals,” ASME J. Eng. Gas Turbines Power, 136(4), p. 042501). Three hole depths (1.905 mm, 3.302 mm, and 6.604 mm) and three running speeds (10,200 rpm, 15,350 rpm, and 20,200 rpm) are considered. For the steady-state flow, the 3D Reynolds-Averaged-Navier-Stokes (RANS) equations are solved with the k-ϵ turbulence model for a circumferentially periodic sector of the full seal geometry. The steady-state results are input into the first-order equations of a bulk-flow model to predict rotordynamic coefficients. Results of the hybrid method are compared to experimental data. CFD predicted leakage showed good agreement (within 5%) for the 3.302 mm and 6.604 mm hole depth configurations. For the 1.905 mm hole depth seal, agreement was within 17%. An additional set of calculations performed with the shear stress transport (SST) turbulence model produced worse agreement. Examination of streamlines along the seal show that the hole depth controls the shape of the vortex that forms in the hole, driving the resistance experienced by the jet flow in the clearance region. For the rotordynamic coefficients, good agreement is shown between predictions and experiment for most excitation frequencies.

Impact of damper seal coefficients uncertainties in rotor dynamics

“…Migliorini et al [19] proposes a hybrid method where CFD is applied to solve the base state flow, and a bulk-flow perturbation method is used to solve for the fluid forces acting on an eccentric, whirling rotor. In the current work, friction factors given by Migliorini et al [18] for a similar seal will be used.…”

Influence of new surface micro-structures on the performance behaviours of fluid film tilting pad thrust bearings

“…In the recent past, researchers are studying and improving bearing performance by modifying the mating surface topographies. The use of profiling 7–10 and textures 11–64 on mating surfaces have yielded a significant reduction in power loss and improvement in oil film thickness. Tribo-performance explorations in the existence of surface textures have attracted the wide attention of researchers in recent years.…”

Numerical Investigation on Static and Rotor-Dynamic Characteristics of Convergent-Tapered and Divergent-Tapered Hole-Pattern Gas Damper Seals

“…Annular gas seals in turbomachinery are widely used to minimize the leakage rate through clearance involved with rotating and stationary parts [1]. The advanced seal design can improve the efficiency of turbomachinery and the stability of the rotor system [2]. However, currently, the design of advanced turbomachinery requires higher speed, tighter clearance, and higher thrust to weight ratio.…”