000265907 001__ 265907
000265907 005__ 20190617200543.0
000265907 0247_ $$a10.5075/epfl-thesis-7115$$2doi
000265907 037__ $$aTHESIS 000265907 041__$$aeng
000265907 088__ $$a7115 000265907 245__$$aMultiscale Modeling and Simulation of Erosive Wear in Pelton Turbines
000265907 260__ $$bEPFL$$aLausanne$$c2019 000265907 269__$$a2019
000265907 300__ $$a253 000265907 336__$$aTheses
000265907 502__ $$aProf. Sophia Haussener (présidente) ; Prof. François Avellan (directeur de thèse) ; Prof. Jean-François Molinari, Prof. Gianandrea Vittorio Messa, Dr Stéphane Fréchinet (rapporteurs) 000265907 520__$$aHydropower has been identified as a key technology to mitigate climate change due to its very low lifecycle greenhouse gas emission intensity and its capacity to integrate intermittent renewable energy sources such as wind and solar into the electrical grid. One of the problems that limits a wider adoption of hydropower is the erosive wear that hydraulic turbines are subject to when operated under sediment-laden water. The technical capacity to predict the erosion process of prototype-scale machines is instrumental to the optimization of the runner designs and the operation strategies of hydroelectric plants. However, this technical capacity is lacking: neither laboratory experiments nor traditional numerical simulations are capable of delivering quantitative predictions.

The difficulty of simulating the erosion process is explained by its multiscale character: it is a very gradual modification of large surfaces, yet it is the consequence of trillions of ephemeral impacts by microscopic sediments. This thesis presents a novel multiscale model of erosion that bypasses the need for erosion correlations by explicitly simulating the sediment impacts, without sacrificing the scope to simulate the long-term erosion process of an industrial-scale component. The proposed model is composed of two sequentially coupled submodels: the microscale model describes the particle impacts with all the detail required to accurately capture the high strain rate thermomechanical process involved; the macroscale model describes the turbulent sediment transport and the accumulation of erosion on the domain of interest. A projective integration scheme is used together with the multiscale model to simulate the long-term transformation of the surface and its effects on the hydrodynamics and subsequently on the erosion rate.

After introducing the model formulation, a detailed discussion of the simplifications inherent to the multiscale approach and the modeling assumptions is presented. The finite volume particle method used to discretize the governing equations is introduced next, followed by the experimental characterization of the runner material.

Four case studies are used to assess, verify and validate the proposed multiscale model. The first case study deals with the erosion of a flat plate by an impinging jet; convergence, parametric and sensitivity analyses of the microscale and macroscale models are presented, as well as a first satisfactory validation. The second case study demonstrates the use of projective integration to predict the long-term surface transformation of a 2D bucket and its effects on the outlet angle and reaction force; a feedback whereby the surface alteration increases the erosion rate is evidenced. The third case study deals with the erosion of a static prototype-scale Pelton bucket whereas the fourth case study involves a rotating prototype-scale Pelton runner; satisfactory validations of the erosion distribution results are presented for both cases.

The results obtained, namely quantitative predictions of the erosion of industrial-scale components, have no precedent in the literature. Furthermore, the model is shown to provide physically sound descriptions of the underlying impact condition distributions that explain the erosion distributions obtained. Overall, it can be said that the multiscale model is a significant improvement over the state-of-the-art models in regard to accuracy and transferability.
000265907 592__ $$b2019 000265907 6531_$$amultiscale modeling
000265907 6531_ $$aerosion 000265907 6531_$$awear
000265907 6531_ $$ahydraulic turbine 000265907 6531_$$aPelton turbine
000265907 6531_ $$anumerical simulation 000265907 6531_$$aparticle-based method
000265907 6531_ $$afinite volume particle method 000265907 6531_$$aprojective integration
000265907 700__ $$aLeguizamón Sarmiento, Sebastián Camilo$$g222271
000265907 720_2 $$g104417$$edir.$$aAvellan, François 000265907 8564_$$uhttps://infoscience.epfl.ch/record/265907/files/EPFL_TH7115.pdf$$s99791886 000265907 909C0$$pLMH
000265907 909CO $$pthesis$$pSTI$$pDOI$$ooai:infoscience.epfl.ch:265907$$qthesis-public 000265907 918__$$aSTI$$cIGM$$dEDEY
000265907 919__ $$aLMH 000265907 920__$$a2019-06-07$$b2019 000265907 970__$$a7115/THESES
000265907 973__ $$sPUBLISHED$$aEPFL
000265907 980__ aTHESIS