Rotationally-induced unstable flow characteristics and structural optimization of rim seals

Abstract

In view of rotationally-induced unsteady rim sealing flow issues in the absence of mainflow nonuniform pressure fields, the large eddy simulation method validated by the enclosed rotating cavity flow measurement was adopted to investigate the instability of the flow in the enclosed rim seal cavity. On this basis, the unsteady Reynolds-averaged numerical calculation was carried out for three structures: typical axial and radial rim seals as well as the chute seal that is visible in actual engines. The unsteady sealing flow characteristics for typical rim seal structures are investigated. The dynamic characteristics of the large-scale vortex structures in the rim seal region are revealed by fast Fourier transform and cross-correlation analysis methods. Finally, the rotationally-induced sealing characteristics for different rim seal structures and the enlightenment of the seal structure optimization are given. The results show that the rotationally-induced rim sealing flow has inherent instability characteristics; a series of large-scale vortex structures are generated in the rim clearance region, which propagate in the circumferential direction at a speed lower than the rotor, and the vortex frequency, number of revolutions and number of vortices depend on the rim seal type; overall, the chute rim seal has the highest rotationally-induced sealing effectiveness.