This thesis describes the application of Large-Eddy Simulation (LES) to the internal flows within turbomachines. In particular, the work sought to investigate whether LES could give an improved predictive tool for flows through a turbine rim seal where other methods of modelling turbulence give disappointing results for the simulation of hot annulus gas ingestion into the rim seal cavity. The applicability of LES to flow regimes within a rotor-stator cavity were investigated with reference to two experimental studies, those of Daily & Nece [1] and of Itoh et al. [2]. LES simulations were run using the commercial Computational Fluid Dynamics (CFD) code FLUENT and the Rolls-Royce CFD code HYDRA. Both gave good agreement for the velocity field even when the boundary layer was not fully resolved. HYDRA was then used to simulate a turbine rim seal cavity with external flow through an annulus with NGV and rotor blades, modelled using a small sector with periodic boundary conditions in the circumferential direction. LES was found to predict higher levels of ingestion than Unsteady Reynolds- Averaged Navier-Stokes (URANS) simulations at a number of different values of cavity throughflow. This resulted in better, but not close, agreement with the experiments of Gentilhomme [3]. The sensitivity of the LES to changes in the size of the sector and to the resolution of the CFD grid were investigated. A larger sector simulation, corresponding to 40°, gave almost identical results to those on the smaller sector, 13.3°. Refinement to the CFD grid did lead to different results, particularly in the annulus flow, though critically the prediction of ingestion in the stator boundary layer was largely unaffected.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553681 |
| Date | January 2011 |
| Creators | O'Mahoney, T. S. D. |
| Publisher | University of Surrey |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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