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- Pumped Storage
Analysis of the Effects of Pre-whirl on the Efficiency and Operating Range of Hydro Pumps used in Pumped Storage Facilities
Lead Companies
The Pennsylvania State University
Lead Researcher (s)
- Keith Martin
This paper discusses the application of computational fluid dynamics (CFD) to a case study of a hydraulic pump turbine operating in pumping mode. Emphasis is on the effects of induced pre-whirl on flow patterns through the impeller and on pump performance. ANSYS R Fluent, Academic Research, Release 14.0, software is used to model three-dimensional (3D) Reynolds-averaged Navier-Stokes (RANS) equations with a k − ω SST turbulence model. Full-wheel fixed rotor simulations are used to identify operating parameters that are used in more computationally intensive full-wheel moving mesh simulations.
Technology Application
Pumped Storage
Research Category
Powerhouse Pump
Research Sub-Category
Turbine
Status
complete
Completion Date
2015
- Conventional Hydro
Cold Spray
Lead Companies
PNNL
Lead Researcher (s)
- Chris Smith
Technology for cavitation repair, cold spray repairs involve the impact of high-velocity particulates with the subject material, which strike with such a high speed that they bond with the chemical structure of the substrate. This has the promise of improved performance and ease of repair over other conventional applications.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
ongoing
Completion Date
TBD
- Conventional Hydro
Cold Spray Process Development in -situ Repair of Hydroturbines
Lead Companies
PNNL
Lead Researcher (s)
- Chris Smith
The first goal of this project is to produce an optimized cold spray process for cavitation resistance that represents an additional 50% improvement over cold spray processes tested in PNNL’s current cavitation repair program. The second goal is to include the optimized cold spray process, developed as part of this TCF project, in field testing that is being developed as part of a Bonneville Power Administration (BPA) Technology Innovation (TI) project.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
ongoing
Completion Date
TBD
- Conventional Hydro
Computation and Analysis of Cavitating Flow in Francis-Class Hydraulic Turbines
Lead Companies
The Pennsylvania State University
Lead Researcher (s)
- Daniel Leonard
Hydropower is the most proven renewable energy technology, supplying the worldwith16%of its electricity. Conventional hydropower generates a vast majority of that percentage. Although a mature technology, hydroelectric generation shows great promise for expansion through new dams and plants in developing hydro countries. Moreover, in developed hydro countries, such as the United States, installing generating units in existing dams and the modern refurbishment of existing plants can greatly expand generating capabilities with little to no further impact on the environment. In addition, modern computational technology and fluid dynamics expertise has led to substantial improvements in modern turbine design and performance.Cavitation has always presented a problem in hydroturbines, causing performance breakdown, erosion, damage, vibration, and noise. While modern turbines are usually designed to be cavitation-free at their best efficiency point, due to the variable demand of the energy market it is fairly common to operate at off-design conditions. Here, cavitation and its deleterious effects are unavoidable, and hence, cavitation is a limiting factor on the design and operation of these turbines. Multiphase Computational Fluid Dynamics (CFD) has been used in recent years to model cavitating flow for a large range of problems, including turbomachinery. However, CFD of cavitating flow in hydro turbines is still in its infancy.This dissertation presents steady-periodic Reynolds-averaged Navier-Stokessimulations of a cavitating Francis-class hydro turbine at model and prototype scales. Computational results of the reduced-scale model and full-scale prototype, undergoing performance breakdown, are compared with empirical model data and prototype performance estimations based on standard industry scalings from the model data. Mesh convergence of the simulations is also displayed. Comparisons are made between the scales to display that cavitation performance breakdown can occur more abruptly in the model than the prototype, due to lack of Froude similitude between the two. When severe cavitation occurs, clear differences are observed in vapor content between the scales. A stage-by-stage performance decomposition is conducted to analyze the losses within individual components of each scale of the machine. As cavitation becomes more severe, the losses in the draft tube account for an increasing amount of the total losses in the machine. More losses occur in the model draft tube as cavitation formation in the prototype draft tube is prevented by the larger hydrostatic pressure gradient across the machine.Additionally, unsteady Detached Eddy Simulations of the fully-coupled cavitating hydro turbine are performed for both scales. Both mesh and temporal convergence studies are provided. The temporal and spectral content of fluctuations in torque and pressure are monitored and compared between single-phase, cavitating, model, and prototype cases. A shallow draft tube induced runner imbalance results in an asymmetric vapor distribution about the runner, leading to more extensive growth and collapse of vapor on any individual blade as it undergoes a revolution. Unique frequency components manifest and persist through the entire machine only when cavitation is present in the hub vortex. Large maximum pressure spikes, which result from vapor collapse, are observed on the blade surfaces in the multiphase simulations, and these may be a potential source of cavitation damage and erosion.Multiphase CFD is shown to be an accurate and effective technique for simulating and analyzing cavitating flow in Francis-class hydraulic turbines. It is recommended that it be used as an industrial tool to supplement model cavitation experiments for all types of hydraulic turbines. Moreover, multiphase CFD can be equally effective as a research tool, to investigate mechanisms of cavitating hydraulic turbines that are not understood, and to uncover unique new phenomena which are currently unknown.Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2015
- Pumped Storage
Cost Effective Small Scale Pumped Storage Configuration [HydroWIRES]
Lead Companies
Obermeyer Hydro
Lead Researcher (s)
- Greg Stark, greg.stark@nrel.gov
Since 2000 only one new pumped storage hydropower project has been constructed in the United States. In order to increase the future opportunity for pumped storage development, reductions in cost and scale are necessary. Historically, pumped storage projects have required large capacity to overcome the fixed costs associated with custom engineering of complex underground structures with associated geological risk. The Obermeyer Hydro submersible pump-turbine offers a standard, scalable solution which reduces underground construction and risk. Technology Application
Pumped Storage
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
ongoing
Completion Date
TBD
- Conventional Hydro
Design and Manufacturing Study of Hydroelectric Turbines Using Recycled and Natural Fiber Composites
Lead Companies
Oregon State University
Lead Researcher (s)
- Marc Whitehead
The objective of this project is to demonstrate the feasibility fiber-reinforced turbine components through a design and manufacturing study. The motivation for using composites is to reduce weight and simplify manufacturing especially at high production volumes. In addition, natural fiber composites are implemented for applicable components to reduce environmental impact. Existing steel designs provided by major manufacturers are used as models. These are re-designed using composite materials, maintaining original geometry as much as possible. The components selected for composite design are the turbine penstock, scroll case, guide vanes, runner (impeller) and draft tube. In addition, the design of a composite fish ladder is presented to show the application of composites to other elements of hydroelectric power. Once the structural and mechanical design was complete, material and manufacturing costs were analyzed. The choice of materials was based upon loading requirements, the runner required a high strength random reinforcement carbon fiber sheet molding compound (SMC) while a glass fabric and rovings provided adequate strength for the guide vanes, scroll case, penstock and outer walls of the fish ladder while minimizing the cost. A flax fabric was selected for the design of the draft tube additionally using a bio-based PLA resin. The inner sections of the fish ladder use a flax fabric and polypropylene pultrusion. Manufacturing methods for each were selected based on geometry and cost. The complex shape of the runner was most easily formed using compression molding, which also reduced the cost as compared to hand lay up. A comparison between hand lay up and vacuum infusion was completed for the guide vanes and scroll case. Hand lay up was chosen for the draft tube as it is the most commercially proven method for the manufacture of components using natural fibers. Filament winding, the method used for the penstock would be the ideal method of manufacture but it has yet to be completed in a commercial setting with natural fibers. Results show the cost of most parts is dominated by tooling (molds) for the components as the research focused on a small run of ten parts, assumed to be for research and testing purposes. However, the contribution of tooling can be cut in half if the run size is doubled. The design and manufacturing analysis does support the use of composite materials in hydroelectric turbines and the costs associated with their manufacture are within reasonable parameters for industry.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2013
- Conventional Hydro
Development of a Numerical Tool to Predict Hydrodynamics, Temperature and TDG in Hydropower Flows
Lead Companies
University of Iowa
Lead Researcher (s)
- Yushi Wang
Hydropower is the most important renewable energy source on the planet. Though it provides abundant benefits to society, it also has environmental and ecological consequences. Dam construction significantly alters natural flow conditions. Fish numbers decline and other aquatic life may be adversely affected, especially during migration and reproduction cycles, due to degradation of their natural habitat. High summer water temperatures in hydropower reservoirs and elevated total dissolved gas (TDG) concentrations in downstream tailrace regions can increase mortality rates of fish passing through the dam. This study proposes to develop a numerical model to improve the prediction of hydrodynamics and water-quality parameters in hydropower flows. The main focus is to simulate temperature dynamics and TDG distribution in the McNary Dam forebay and tailrace. Existing numerical temperature and TDG models, developed by Politano et al. (2008, 2009c), were improved and implemented into the open-source CFD code OpenFOAM. These newly developed models can be used to evaluate the efficiency of operational changes or structural modifications to reduce the negative environmental impacts of hydropower facilities. The forebay temperature model was based on the incompressible ReynoldsAveraged Navier-Stokes (RANS) equations with the Boussinesq approximation. Turbulence was modeled with an improved realizable k model taking into account wind turbulence generation at the free surface. A thermal model incorporating solar radiation and convective heat transfer at the free surface was employed. The model was validated against field data collected on August 18th, 2004 at McNary Dam. Observed vertical and lateral temperature distributions and dynamics in the forebay were captured by the model. The incorporation of the atmospheric heat flux, solar radiation, and windinduced turbulence improved the temperature predictions near the free surface. The multi-phase TDG model utilized the Volume of Fluid (VOF) method combined with a Detached Eddy Simulation (DES) approach to calculate hydrodynamics. A one-way coupling approach was used to incorporate a TDG model, which includes the transport and dissolution of bubbles entrained in the spillway and takes into account bubble size change caused by dissolution and compression. The capability of the present model to predict spillway flow regimes was evaluated against observations in a reduced scale laboratory model. Simulation results demonstrated that flow regimes downstream of a spillway can be adequately reproduced by the numerical model. The capability of the model to quantify dissolved gas exchanges and TDG distribution was evaluated using a tailrace sectional model. The model captured TDG production and observed longitudinal TDG reduction under different flow regimes. Disparities between predicted and measured average TDG values fell within 4%. The model developed in this study is an effective predictive numerical tool to identify flow regimes and quantify TDG production under various flow conditions in near dam regions when lateral flows are not important.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2013
- Conventional Hydro
Development of Hydro Plant Bushings and Seals Best Practices
Lead Companies
CEATI International
Lead Researcher (s)
- 03/107
The report will present an in-depth analysis of the current best practices and case studies of non-lubricated bushings and seals in use by the hydro industry.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
ongoing
Completion Date
Expected 2022
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Have questions about WaRP?
Contact Marla Barnes at: marla@hydro.org