Influence of Secondary Sealing Flow on Performance of Turbine Axial Rim Seals

Purge flow is of great importance in cooling turbine disks and sealing rotor-stator disc cavity to reduce hot gas ingestion in gas turbines.The amount of cooling air extracted from the compressor is crucial to engine efficiency.Excessive sealing air will cause not only a reduction in work transfer but also an increase in aerodynamic losses caused by the mixing of main and sealing flow.In order to simplify rim seal structure while ensuring high sealing efficiency,the current paper optimizes the flow path of the secondary air system and presents a new rim seal structure with auxiliary sealing holes transporting a certain amount of secondary sealing flow.The new structure was compared with the conventional counterpart using validated CFD methods,showing that the additional secondary sealing flow is possible to improve sealing efficiency in disk cavity.The current paper investigates the secondary sealing flow with and without swirl(the angle of auxiliary sealing hole inclination is 0°and 45°respectively),while maintaining the total amount of the sealing flow,flowrate ratio of sealing air(main sealing flow rate versus secondary sealing flow rate=1:1,2:1,3:1,4:1),found that both two parameters have essential impacts on sealing efficiency.The relationship between these two parameters and sealing efficiency was obtained,and it provides a new philosophy for the design of rim seal in gas turbines.

Influence Analysis of Secondary O-ring Seals in Dynamic Behavior of Spiral Groove Gas Face Seals

The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior（steady-state performance and transient performance） of face seals. A numerical finite element method（FEM） model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.