Numerical Investigation on Unsteady Characteristics in Different Rim Seal Geometries: Part A
Gas turbines, as a power generating machine, are widely used in the world today. The overall thermal efficiency of gas turbine is strongly dependent on the inlet temperature of the turbine. As the turbine inlet temperature increases, the problem of hot mainstream gas ingestion arises. Hot gas ingestion refers to the phenomenon of the mainstream hot gas ingests into the wheel space composed of the turbine disc and its adjacent casing due to the pressure difference between the main stream annulus and the wheel space. Once the hot mainstream gas flows into the wheel space, serious problems like creep, oxidation or thermal fatigue maybe caused, resulting in a shortened lifespan of the turbine components. To diminish the possibility of hot gas ingestion, a stream of cooling air is introduced from the compressor to the wheel space. Insufficient cooling air may result in an excessive thermal load on the turbine components, while a superfluous amount of cooling air would reduce the overall thermal efficiency. Therefore, a compromise must be made to satisfy the cooling demand while at the same time maintain a maximum thermal efficiency. To determine a minimum amount of cooling air, the flow characteristic of the rim seal should be investigated.Numerical simulation is carried out to investigate the flow field near the rim seal region. Both RANS and URANS numerical simulation methods are used in the commercial CFD code ANSYS CFX to analyze axial and radial type of rim seal structures. A 1/33 sector is selected as computing region to simulate the flow field. In the simulation, the SST turbulent model is used. The CFD results are validated using the experiment data published by Sangan in University of Bath. The CFD results are analyzed using several analytical methods including Fast Fourier Transform (FFT). The computed results show that the seal efficiency of radial rim seal is always higher than axial rim seal in all operating conditions. Comparing to steady results using the RANS method; unsteady simulation, which is carried out using URANS method, can capture the pressure difference and seal efficiency fluctuation at the disk rim more efficiently. The results show that unsteady phenomena are observed in both axial and radial type of rim seals. Rim seal with radial sealing lip can easily suppress the Kelvin-Helmholtz instability so as to increase seal efficiency. The results obtained in the current paper is useful to the investigation and design of turbine rim seals.
Numerical Investigation on Unsteady Characteristics in Different Rim Seal Geometries: Part A
Category
Technical Paper Publication
Description
Session: 12-00 Heat Transfer: Internal Air Systems & Seals (Joint with Turbomachinery) On-Demand Session
ASME Paper Number: GT2020-14832
Start Time: ,
Presenting Author: XieLei
Authors: Lei Xie Institute for Engineering Thermophysics, Chinese Academy of Sciences; University of Chinese Academy of Sciences
Ruonan Wang Institute for Engineering Thermophysics, Chinese Academy of Sciences; University of Chinese Academy of Sciences
Guang Liu Institute for Engineering Thermophysics, Chinese Academy of Sciences; University of Chinese Academy of Sciences
Qiang Du Institute for Engineering Thermophysics, Chinese Academy of Sciences; University of Chinese Academy of Sciences
Zengyan LianInstitute for Engineering Thermophysics, Chinese Academy of Sciences; University of Chinese Academy of Sciences