Modelling of the flow at the last stage blade tenon in a geothermal turbine using renormalization group theory turbulence model
✍ Scribed by F.Z. Sierra; Z. Mazur; J. Kubiak; G. Urquiza; R. Zúñiga; C. Mariño; A. Hernández
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 524 KB
- Volume
- 20
- Category
- Article
- ISSN
- 1359-4311
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✦ Synopsis
A bi-dimensional modelling investigation of the ¯ow in the last stage of a 110 MW geothermal turbine has been conducted. The study was based upon a Renormalization Group Theory turbulence model. The results con®rmed the existence of ¯ow conditions which may play a main role in the erosion of the L-0 stage blade tenon, which had been detected in periodic overhauls. According to predicted results the relationship between erosion and ¯ow patterns might exist due to: (1) a vapour jet hitting directly on tenon surface at velocities around 65 m/s; (2) a low-pressure region identi®ed with recirculating ¯ow, which may be causing cavitation on the damaged surface. Afterwards, the ¯ow was simulated with changes on the geometry and grid. These changes are, indeed, practically feasible of being implemented. The simulations showed that it is possible to reduce the erosion process by enlarging a ¯at region close to the L-0 rotor stage. Namely, this change of geometry produces a ¯ow pattern that diminishes the strength of recirculation ¯ow making it possible to reduce both the ¯ow rate through tenon region and its velocity on tenon surface. The pressure drop diminishes as well, clearly reducing a risk of cavitation.