Assessment of Rim Seal Performance under Rotor Axial Displacement

Computational fluid dynamics (CFD) simulations were performed to assess rim seal performance under rotor axial displacement. A single radial clearance rim seal geometry was employed, and the predictive capability of the CFD methodology was evaluated against experimental data obtained from a 1.5-stage turbine rim seal test. The Reynolds-averaged Navier–Stokes (RANS) approach exhibited a slight overprediction of sealing effectiveness relative to the measurements; nevertheless, the level of agreement was considered sufficient to validate the methodology, and the use of more computationally demanding transient simulations was deemed unnecessary. The analysis confirmed a strong association between the swirl component of the main flow and hot gas ingestion. Rotor axial displacement was shown to modify both overlap length and axial clearance. In the upstream cavity, the reduction of overlap length in combination with increased axial clearance resulted in decreased sealing effectiveness, whereas the downstream cavity exhibited improved effectiveness under the same conditions. These results demonstrate that rim seal performance is sensitive to variations in overlap and axial clearance even when radial clearance is held constant. Furthermore, a pronounced decline in sealing effectiveness was observed when overlap length was reduced beyond a critical threshold, indicating the necessity of establishing design criteria with respect to seal overlap.