Understanding casing flow in Pelton turbines by numerical simulation

Rentschler, Martin; Neuhauser, Magdalena; Marongiu, Jean-Christophe; Parkinson, Étienne

doi:10.1088/1755-1315/49/2/022004

Cited by 8 publications

(7 citation statements)

References 10 publications

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“…Both Smooth Particle Hydrodynamic method [ 37 ] and Eulerian CFD methods (Petley et al. works) have been carried out, but more numerical and computational efforts should be done to reduce computational costs of these methods, since they involve complex 3D, unsteady and turbulent phenomena, with air inclusion, free surface thin jets and droplets.…”

Section: Discussionmentioning

confidence: 99%

“…Droplets are difficult to be captured. The influence of the unpredictable flow patterns on the overall efficiency of the machine is expected to be in the range of the other numerical and physical errors that are introduced into the simulation [ 37 ]. These limitations pose the light on the need of better improving the research in this context and of better understanding the available literature results.…”

Section: Hydrodynamics and Fluid Dynamic Optimizationmentioning

confidence: 99%

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The state-of-art of design and research for Pelton turbine casing, weight estimation, counterpressure operation and scientific challenges

Quaranta¹,

Trivedi²

2021

Heliyon

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The Pelton turbine is the most widespread and efficient impulse hydropower turbine. The Pelton casing is a static, but key component: the internal hydrodynamic phenomena affect the performance of the hydropower plant, the vibration of the equipment and water quality (dissolved oxygen downstream). However, the literature information is very fragmented and not well organized, so that the design is generally based on empirical rules and on proper know-how of hydropower companies. In this paper, the state-of-the-art of the Pelton casing is reviewed and organized under three macro areas: hydraulics, mechanics (vibrations and weight) and aeration. The preliminary design procedure is described and discussed in light of recent scientific results, and the open questions and research challenges are highlighted. Innovative case studies are described (including counterpressure operation) and a dataset of installed casings (not available in literature) is elaborated to derive an empirical equation to estimate the casing weight. The efficiency can be improved by 3% by an optimal fluid dynamic design and a better understanding of the internal hydrodynamics. Proper inserts can improve the hydraulic efficiency by 2%, reduce the weight (by about 12%) and better bear the vibrations. Several scientific questions are still open, and a better understanding of the fluid structure interaction is needed to improve efficiency, operation and water quality.

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Section: Discussionmentioning

confidence: 99%

Section: Hydrodynamics and Fluid Dynamic Optimizationmentioning

confidence: 99%

The state-of-art of design and research for Pelton turbine casing, weight estimation, counterpressure operation and scientific challenges

Quaranta¹,

Trivedi²

2021

Heliyon

View full text Add to dashboard Cite

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“…CFD simulation of the flow in Pelton turbines has become an industrial standard in the last decade [4,5], including the simulation of all components of the machine including penstock bifurcation, distributor, nozzle, jet, runner, casing and tailrace [6,7]. The focus of most of these CFD investigations is on the increase of the hydraulic performances with the target to increase the overall efficiency of the hydro power plant.…”

Section: Introductionmentioning

confidence: 99%

Comparison of mechanical stress in Pelton Buckets between simulation and measurement

Rentschler¹,

Weibel

Isler

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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Thinner structures, lead to higher efficiencies, but also to higher mechanical stresses. The increase of the hydraulic performances of Pelton runners is hence limited by mechanical stress constraints. The design process of Pelton runner therefore includes stress and hydraulic assessment during profile development phase. This assessment is based on the combination of Finite Element Method (FEM) for the mechanical stress and computational fluid dynamics (CFD) for the hydraulic behavior of the machine. This combined approach enables the generation of hydraulic profiles with high efficiency while respecting defined limits for the stress. The validation of the combined simulation is achieved by comparison with prototype measurements. For several projects the runners have been equipped with strain gauges in the root and close to the cut-out to record the deformation for different operating points. The comparison with numerical simulation results shows some limitations of the approach but concludes with a satisfying agreement between numerical simulation and measurement.

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“…The characterization of flow through hydraulic turbines has been facilitated by the development of computational fluid dynamics (CFD) simulation codes [3][4][5]. Several areas of flow analysis in the Pelton turbine can be distinguished: flow in the injector, influenced by the geometry of the injector nozzle and spear, flow in the free jet (between the exit surface of the injector and the entry surface on the runner buckets), flow on the runner buckets, flow in the volume created by the runner and the turbine casing [6][7][8]. An analysis of the entire flow path requires high computational power, therefore several studies have focused on specific flow areas.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Nozzle Jet Flow in a Pelton Microturbine

2021

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The characterization of flow through Pelton hydro turbines allows the optimization of their operation and maximization of energy performance. The flow in the injector of Pelton turbines and in the free jet area (the area from the injector outlet surface to the runner bucket inlet surface) is influenced by several parameters: the geometry of injector components (nozzle and injector spear), the injector opening, and the turbine head. The parameters of the free jet flow (velocity distribution, pressure distribution, and jet spread) are reflected in the turbine efficiency. The research presented in this paper focuses on the numerical characterization of flow in the injector and the free jet of a Pelton microturbine. Three injector geometries were considered, with different nozzle diameters: 13.3 mm, 14.4 mm, and 16.3 mm. For each of these geometries, the flow was analyzed for five values of turbine head (H = 15 m, H = 20 m, H = 25 m, H = 30 m, H = 35 m) and six values of injector opening (S = 3 mm, S = 6 mm, S = 9 mm, S = 12 mm, S = 15 mm, S = 18 mm). The results of numerical simulations were used to plot injector flow-rate characteristics and injector force characteristics (the resultant force on the injector spear and the resultant force on the injector nozzle). The highest influence on the flow rate variation is given by the variation of turbine head, followed by the variation of the injector opening and the variation of the nozzle diameter. Increasing the nozzle diameter accentuates the variation of the flow rate versus the turbine head. The variation of axial velocity and pressure in the free jet is presented for four sections parallel to the outlet section of the injector. The injector openings that generate the highest values of velocity/pressure on the runner inlet surface are highlighted. The results allow optimization of functional parameters for increasing turbine efficiency and optimizing the design process of Pelton microturbines.

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Understanding casing flow in Pelton turbines by numerical simulation

Cited by 8 publications

References 10 publications

The state-of-art of design and research for Pelton turbine casing, weight estimation, counterpressure operation and scientific challenges

The state-of-art of design and research for Pelton turbine casing, weight estimation, counterpressure operation and scientific challenges

Comparison of mechanical stress in Pelton Buckets between simulation and measurement

Numerical Investigation of Nozzle Jet Flow in a Pelton Microturbine

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