A Comparison of Single and Double Lip Rim Seal Geometries

Abstract

The effect of the purge flow, engine-like blade pressure field, and mainstream flow coefficient are studied experimentally for a single and double lip rim seal. Compared to the single lip, the double lip seal requires less purge flow for similar levels of cavity seal effectiveness. Unlike the double lip seal, the single lip seal is sensitive to overall Reynolds number, the addition of a simulated blade pressure field, and large-scale nonuniform ingestion. In the case of both seals, unsteady pressure variations attributed to shear layer interaction between the mainstream and rim seal flows appear to be important for ingestion at off-design flow coefficients. The double lip seal has both a weaker vane pressure field in the rim seal cavity and a smaller difference in seal effectiveness across the lower lip than the single lip seal. As a result, the double lip seal is less sensitive in the rotor–stator cavity to changes in shear layer interaction and the effects of large-scale circumferentially nonuniform ingestion. However, the reduced flow rate through the double lip seal means that the outer lip has increased sensitivity to shear layer interactions. Overall, it is shown that seal performance is driven by both the vane/blade pressure field and the gradient in seal effectiveness across the inner lip. This implies that accurate representation of both, the pressure field and the mixing due to shear layer interaction, would be necessary for more reliable modeling.

Flow mechanisms in axial turbine rim sealing

“…[33], Savov et al [34], Schädler et al [35], Jakoby et al [24] and Town et.al. [36] have all indicated unsteady rim seal cavity flow features which are unrelated to blade passing.…”

“…Radial rim seals were studied experimentally by Roy et al [32], Savov et al [34], and Town et al [36], as shown in figure 5 and table 2. The seal and cavity geometries were quite different in these cases, but all tests were conducted with a highly swirling annulus flow.…”

“…A low-peak energy harmonic detected at ~22Ω (1090 Hz), which is about 78% of the rotor blade passing frequency, can be identified. Furthermore it is noteworthy that the energy content of these harmonics decreases as the dimensionless coolant mass flow rate Savov et al [34] studied the performance of two rim seal geometries varying the dimensionless seal purge flow rate, for both bladed and unbladed configurations. Fast response pressure transducers were fitted to the stator in the main disc cavity, the outer rim seal cavity or trench (radially outboard of the minimum clearance), and in the cavity feeding the purge flow.…”

Inertial waves in turbine rim seal flows

“…The first published experimental observation of these large-scale unsteady flow modes was reported by Cao et al [16] the T-C instability include Boudet et al [17], O'Mahoney [18] and Gao et al [19], and those proposing the K-H instability include Rabs et al [20], Chilla et al [21], Savov et al [22] and Horwood et al [15]. Another possible source of unsteadiness, suggested by Berg et al [23], are the Helmholtz and shallow cavity modes.…”

The Sealing Efficiency and Interaction between Purge Flow and Mainstream Flow for Novel Rim Seal Configurations

“…Schuler et al [1] found that axial overlapping compound geometry can more effectively prevent mainstream ingestion and reduce the height of the boundary layer lifted by the purge flow. Savov et al [2] compared the single and double lip rim seal geometries and found that the double lip rim seal requires less flow to achieve the same sealing efficiency. Erickson et al [3] proposed and compared the effects of "shark nose" and "dolphin nose" structures of the lip.…”