NUMERICAL INVESTIGATIONS OF FLOW STRUCTURES IN RADIAL RIM SEAL AND A MODIFICATION OF THE ORIFICE MODEL

Under the increasing turbine temperature of gas turbine, the thermal bearing capacity of rotor and stator of turbine is increasingly limited, which poses a more severe challenge to the protection means such as rim seal, and requires more detailed estimation of flow and heat transfer of rim seal. One of the most important parameters in the estimation is the sealing efficiency. The Orifice Model is widely used to simplify the prediction of sealing efficiency of various sealing structures. Its advantage is that different structures can be described by the same model. However, further work is needed in the prediction of sealing efficiency for more complex structures or the high radius of the locations such as the interface between the disc cavity and the main flow. In this paper, steady numerical simulation is carried out for a radial rim seal structure, and the numerical results are verified by the experimental results in the disk cavity. The flow phenomenon and the mechanism of ingress flow near the rim seal structure is further studied. It is found that the ingress flow has axial and circumferential inhomogeneity, According to the tangential velocity, the ingress flow presents two distinct and "antagonistic" fluids respectively. On this basis, this paper proposes a modification to the Orifice Model, which determine whether the flow is egress or ingress by the tangential velocity. In addition, according to this method, the two-dimensional distribution of the egress and ingress at the interface near the main flow can be seen, and it can be fitted with a simple multisegment linear function.