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- Conventional Hydro
Increasing Operational Flexibility of Francis Turbines at Low Head Sites, Through Analytical and Empirical Solutions [HydroWIRES]
Lead Companies
GE Global Research
Lead Researcher (s)
- Miaolei Shao, Miaolei.shao@ge.com
As operation of turbines outside the operational range recommended by the original manufacturer is more demanding for the machine, significant operational ranges are not included in typical operations planning. Enabling a broader operational range (even temporarily, for a few minutes or hours) offers an opportunity to upgrade dispatch strategy, increase flexibility, and increase support for the grid reliability and resilience. The overall goal of this project is to demonstrate the potential to increase the operational flexibility of installed low head Francis turbine driven hydropower-plants. Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
ongoing
Completion Date
TBD
- Conventional Hydro
- Conventional Hydro
Modifications to the Runner Blade to Improve Off-Design Efficiencies of Hydraulic Turbines
Lead Companies
The Pennsylvania State University
Lead Researcher (s)
- Matthew Erdman
Hydroturbines are known to have very high efficiency at their best efficiency point (BEP). However, it has become increasing beneficial to run some hydroturbines at conditions that are significantly different than BEP. This is a direct result of volatile price fluctuations on the electric market, limited storage capabilities, and environmental rules and regulations. Running the hydroturbine at off-design conditions can result in a significant amount of residual swirl in the draft tube. The presence of this residual swirl is particularly detrimental to the performance of Francis hydroturbines since they rely on a pressure head to generate power. Previous research at The Pennsylvania State University numerically discovered that injecting water through the trailing edge of the wicket gates could change the bulk flow direction upstream of the runner blades. In this manner, the flow rate and swirl angle entering the runner blade could be altered to limit residual swirl in the draft tube. The research determined that properly tuned jets could result in a significant improvement in turbine efficiency when the hydroturbine was operating at low flow. However, this required pumping water through channels into a region of relatively high pressure. This pump requirement lessened the effectiveness of the wicket gate trailing edge injection. The concept of water jet injection was further explored in the present work. However, instead of injecting water into a region of relatively high pressure, water jets were placed at the trailing edge of the runner blades where there is a region of relatively low pressure. It was determined that, although this water jet injection improved the off-design efficiency of a low flow case by 0.8%, the hydroturbine now required a larger head in order to maintain the flow rate. The present work found no increase in efficiency for the high flow case with the added water jet injection technique.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2016
- Conventional Hydro
Pilot Scale Tests Alden/Concepts NREC Turbine
Lead Companies
Department of Energy and Alden Research Laboratory
Lead Researcher (s)
- Thomas Cooke, George Hecker, Steve Amaral, Philip Stacy
Alden Research Laboratory, Inc. (Alden) has completed pilot scale testing of the new Alden/Concepts NREC turbine that was designed to minimize fish injury at hydropower projects. The test program was part of the U.S. Department of Energy’s (DOE) Advanced Hydropower Turbine Systems Program. The prototype turbine operating point was 1,000 cfs at 80 ft head and 100 rpm. The turbine was designed to: 1) limit peripheral runner speed; 2)have a high minimum pressure; 3) limit pressure change rates; 4) limit the maximum flow shear; 5) minimize the number and total length of leading blade edges; 6) maximize the distance between the runner inlet and the wicket gates and minimize clearances (i.e., gaps) between other components; 7)maximize the size of flow passages. A pilot scale facility was designed and constructed to test a 1:3.25 reduced scale turbine with and without wicket gates. The test loop was operated at flows ranging between 50-95 cfs and 35-85 ft heads and the pilot scale turbine was operated at speeds ranging between 200-375 rpm to determine the Best Efficiency Point (BEP) over the range of wicket gate positions. Engineering tests were conducted to define the turbine BEP speed and head/flow combinations without and with wicket gates. Biological testing was conducted to evaluate turbine passage survival relative to: 1) fish injection location at the turbine inlet; 2) size of fish; 3) species; 4) high and low turbine speed/head/flow conditions; 5) BEP with and without wicket gates, and; 6) off-BEP wicket gate positions. A final CFD analysis was completed as part of the pilot scale study to investigate the turbine flow patterns at off-BEP wicket gate positions for comparison to the flow patterns at the BEP gate position and observed fish injury at the different gate settings. The pilot scale test results indicate that the Alden/Concepts NREC turbine has the potential to pass fish at hydroelectric projects with minimal injury and mortality.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2003
- Marine Energy
Scale up, Field Testing, and Optimization of Nontoxic, Durable, Economical Coatings for Control of Biofouling and Corrosion on Marine Energy Devices and Facilities
Lead Companies
Pacific Northwest National Laboratory
Lead Researcher (s)
- Shane Addleman
The objective of this project is to mature and demonstrate durable, economical, and nontoxic coatings that will prevent fouling organisms from growing on MHK structures. A novel foul-release coating recently developed (initial patents filed in 2016 and 2017) at PNNL, Superhydrophobic Lubricant Infused Composite (SLIC) technology, will be adapted to provide the durability necessary for >5 year protection in the marine environment.
Technology Application
Marine Energy
Research Category
Technology
Research Sub-Category
Turbine
Status
ongoing
Completion Date
TBD
- Conventional Hydro
Simulation, Analysis and Mitigation of Vortex Rope Formation in the Draft Tube of Hydraulic Turbines
Lead Companies
The Pennsylvania State University
Lead Researcher (s)
- Hosein Foroutan
Flow in the draft tube of a hydraulic turbine operating under off-design conditions is very complex. The instability of the swirling flow may lead to the formation of a helical precessing vortex called the “vortex rope”. The vortex rope causes efficiency reduction, severe pressure fluctuation, and even structural vibration. The primary objectives of the present study are to model and analyze the vortex rope formation using high fidelity numerical simulations. In particular, this work aims to understand the fundamental physical processes governing the formation of the vortex rope, and to investigate the capability of turbulence models to simulate this complex flow. Furthermore, mitigation of the vortex rope formation is addressed. Specifically, a vortex rope control technique, which includes injection of water from the runner crown tip to the inlet of the draft tube, is numerically studied. A systematic approach is considered in this study starting from the simplest and advancing towards the most complicated test case. First, steady simulations are carried out for axisymmetric and three-dimensional grids in a simplified axisymmetric geometry. It is shown that steady simulations with Reynolds-averaged Navier-Stokes (RANS) models cannot resolve the vortex rope, and give identical symmetric results for both the axisymmetric and three-dimensional flow geometries. These RANS simulations underpredict the axial velocity by at least 14%, and turbulent kinetic energy (TKE) by at least 40%, near the center of the draft tube even quite close to the design condition. Moving farther from the design point, models fail in giving the correct levels of the axial velocity in the draft tube. This is attributed to the underprediction of TKE production and diffusion near the center of the draft tube where the vortex rope forms. Hence, a new RANS model taking into account the extra production and diffusion of TKE due to vortex rope formation is developed, which can successfully predict the mean flow velocity with as much as 37% improvements in comparison with the realizable k-ε model. Then, unsteady simulations are performed, where it is concluded that Unsteady RANS (URANS) models cannot capture the self-induced unsteadiness of the vortex rope, but instead give steady solutions. The hybrid URANS/large eddy simulation (LES) models are proposed to be used in unsteady simulations of the vortex rope. Specifically, a new hybrid URANS/LES model in the framework of partially-averaged Navier-Stokes (PANS) modeling is developed. This new model is one of the main contributions of the present study. The newly developed PANS model is used in unsteady numerical simulations of two turbulent swirling flows containing vortex rope formation and breakdown, namely swirling flow through an abrupt expansion and the flow in the FLINDT draft tube, a model-scale draft tube of a Francis turbine. The present PANS model accurately predicts time-averaged and root-mean-square (rms) velocities in the case of the abrupt expansion, while it is shown to be superior to the delayed detached eddy simulation (DDES) and shear stress transport (SST) k-ω models. Predictions of the reattachment length using the present model shows 14% and 23% improvements compared to the DDES and the SST k-ω models, respectively. For the case of the FLINDT draft tube, four test cases covering a wide range of operating conditions from 70% to 110% of the flow rate at the best efficiency point (BEP) are considered, and numerical results of PANS simulations are compared with those from RANS/URANS simulations and experimental data. It is shown that RANS and PANS both can predict the flow behavior close to the BEP operating condition. However, RANS results deviate considerably from the experimental data as the operating condition moves away from the BEP. The pressure recovery factor predicted by the RANS model shows more than 13% and 58% overprediction when the flow rate decreases to 91% and 70% of the flow rate at BEP respectively. Predictions can be improved dramatically using the present unsteady PANS simulations. Specifically, the pressure recovery factor is predicted by less than 4% and 6% deviation for these two operating conditions. Furthermore, transient features of the flow that cannot be resolved using RANS/URANS simulations, e.g., vortex rope formation and precession, is well captured using PANS simulations. The frequency of the vortex rope precession, which causes severe fluctuations and vibrations, is well predicted by only about 2.7% deviation from the experimental data. Finally, the physical mechanism behind the formation of the vortex rope is analyzed, and it is confirmed that the development of the vortex rope is associated with formation of a stagnant region at the center of the draft tube. Based on this observation, a vortex rope elimination method consisting of water jet injection to the draft tube is introduced and numerically assessed. It is shown that a small fraction of water (a few percent of the total flow rate) centrally injected to the inlet of the draft tube can eliminate the stagnant region and mitigate the formation of the vortex rope. This results in improvement of the draft tube performance and reduction of hydraulic losses. Specifically in the case of the simplified FLINDT draft tube, the loss coefficient can be reduced by as much as 50% and 14% when the turbine operates with 91% and 70% of the BEP flow rate, respectively. In addition, reduction (by about 1/3 in the case with 70% of BEP flow rate) of strong pressure fluctuations leads to more reliable operation of the turbine.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2015
- Conventional Hydro
Study of Mass Transfer across Hydrofoils for Use in Aerating Turbines
Lead Companies
University of Minnesota
Lead Researcher (s)
- Garrett Monson
Hydroelectric projects often have a low tailwater dissolved oxygen (DO) concentration. Low DO levels negatively impact the biota of the water body and are often regulated. Auto-Vented Turbines (AVTs) are one form of DO mitigation that is typically successful and cost-effective. Saint Anthony Falls Laboratory (SAFL) at the University of Minnesota (UMN) is partnering with the Department of Energy (DoE) and Alstom Engineering to conduct research developing a conventional hydropower turbine aeration test-bed for computational routines and a software tool for predicting the DO uptake of AVTs. The focus of this thesis is on the development of the testbed through the conduct of physical experiments focused on measuring mass transfer across bubbles in various flow conditions. This test-bed will be a valuable database for verification of numerical models of DO uptake. Numerical models can simulate the parameters of the water tunnel and experimental set-up, then verify their accuracy by simulating the air entrainment rate, bubble size and mass transfer of the test-bed. The findings presented herein can lead to further optimization of AVTs, as well as reduce cost and regulatory uncertainty prior to hydropower relicensing or development.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2013
- Conventional Hydro
Surface-Reconditioning Additives Based on Solid Inorganic Nanoparticles for Environment-Friendly Industrial Lubricating Compositions
Lead Companies
Washington State University
Lead Researcher (s)
- Pavlo Rudenko
Our research is aimed at the application of lamellar ceramic solid nanoparticles as surface reconditioning additives to industrial lubricating oils to achieve self-repair and improve lubricity. According to a NERC, lubrication failures are among the top causes of outages and deratings of hydroelectric turbines. This problem represents a tremendous opportunity to improve the reliability and availability of hydroelectric turbines by improving their lubricating technologies. The majority of the environmental toxicity of these lubricating compositions is from the additives, where few alternative options are being explored. Today, the ability to formulate lubricating compositions that are safe for the environment greatly depends on additives. There has been a steadily growing interest toward solid, inorganic nanopowders of natural minerals such as Magnesium Hydro-Silicates(MHS) as antiwear and friction modifying additives in lubricating oils. Such powders can reduce wear and promote the formation of thick (up to 30 microns) tribofilms on the rubbing surfaces with great lubricating properties. Self-regulating mechanism of a film formation, and the ability to compensate for wear, allows for the self-repair effect to be achieved. This research is directed at expanding our understanding of the industrial applications for this technology and not only improve current lubricating compositions, but also note additional effects: such as superlubricity and reconditioning worn surfaces. We evaluated the influence of temperature, pressure, and concentration on friction properties. The optimal concentration of nanoparticles was obtained for steel-on-steel friction pairs. Our additives can be applied toward regular and preventative maintenance in the power generating industries as well as emergency surface treatment after lubrication failure has occured to compensate for wear.
Technology Application
Conventional Hydro
Research Category
Powerhouse Equipment
Research Sub-Category
Turbine
Status
complete
Completion Date
2013
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Contact Marla Barnes at: marla@hydro.org