Session: 14-05: Turbine Rim Seal and Rotor-Stator Cavity 2

Paper Number: 153723

Investigations on Unsteady Gas Ingestion Characteristics of Turbine Full Circumference Radial Rim Seal 

To prevent ingestion of high-temperature gas, the rim seal is designed into the secondary air system and high-pressure coolant fluid is filled into the disk cavity. The high-pressure coolant may partly be ejected into the mainstream through the rim seal and significantly effects turbine aerothermal performance. In order to reduce the computational complexity and meet the storage requirements, most numerical studies have adopted periodic boundary conditions. The structure simplification by ignoring the interaction between the stator and rotor, will lead to a failure in capturing unsteady flow characteristics, and this behavior directly related to the turbine aerothermal performance. Thus, it is very important to capture the unsteady flow characteristics in the cavity completely and accurately while keeping the computational domain size as small as possible. This paper focuses on a new model which combines a periodic cascade with a full circumference disk cavity.

To accurately predict the unsteady gas ingestion characteristics of the radial rim seal in the turbine disk cavity on the basis of minimizing the number of grids and saving computational resources, the combined model of the periodic cascade and the full circumference disk cavity was designed and constructed in this paper. The sealing effectiveness and large-scale vortex structure in the cavity were numerically investigated using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations coupled with a fully developed shear stress transport (SST) turbulent model. The validity of the numerical calculation method was verified by the published experimental model and working condition of the rim seal of a 1.5-stage axial gas turbine in Bath University. By comparing the unsteady gas ingestion characteristics of the radial rim seal of the periodic model and the combined model, the gas ingestion mechanism of the model which combines a periodic cascade with a full circumference disk cavity was expounded.

The results indicated that the periodicity has an effect on both the sealing effectiveness distribution and the large-scale vortex structure. The periodicity can affect the circumferential pressure fluctuation caused by the interference between rotor and stator, so it is impossible to accurately capture the sealing effectiveness and the circumferential non-uniform of pressure distribution. The combined model of the periodic cascade and the full circumference disk cavity can fully capture all kinds of large-scale vortex structures caused by the non-uniform circumferential pressure in the cavity while reducing the computational domain of the cascade. The characteristics of gas ingestion and unsteady flow in the disk cavity can be improved. And the influences of periodic setting on the sealing effectiveness distribution and large-scale vortex structure in the disk cavity were discussed.

Presenting Author: Can Guo Xi'an Jiaotong University

Presenting Author Biography: Ms. Can Guo is a Ph. D. candidate of Institute of Turbomachinery of Xi'an Jiaotong University in China. His research topics focus on the aerodynamic and heat transfer of gas turbines.

Authors:

Can Guo Xi'an Jiaotong University
Bo Bai Xi'an Jiaotong University
Zhigang Li Xi'an Jiaotong University
Jun Li Xi'an Jiaotong University