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  • 1.
    Baidar, Binaya
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A sensitivity analysis of the Winter-Kennedy method2018Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Hydropower is among the lowest-cost electrical energy sources due to its long lifespan and lower operation and maintenance cost. The hydro-mechanical components of hydropower plants generally last about four to five decades, then they are either overhauled or replaced. The major upgrades and refurbishments of the hydropower plants that are ongoing have also been motivated by the introduction of new rules and regulations, safety or environmentally friendly and improved turbine designs. Whatever are the drivers, the refurbishments are usually expected to increase efficiency, flexibility and more power from the plant.

    Efficiency measurement is usually performed after refurbishments. While it is relatively straightforward to measure efficiency in high head machines due to the availability of several code-accepted methods, similar measurements in low head plants remain a challenge. The main difficulty lies in the discharge/flow rate measurement. The reason is due to the continuously varying cross-section and short intake, as a result, the flow profile or parallel streamlines cannot be established. Among several relative methods, the Winter-Kennedy (WK) method is widely used to determine the step-up efficiency before and after refurbishment. The WK method is an index testing approach allowing to determine the on-cam relationship between blade and guide vane angles for Kaplan turbine as well. The method utilizes features of the flow physics in a curvilinear motion. A pair of pressure taps is placed at an inner and outer section of the spiral case (SC). The method relates discharge (Q) as Q=K(dP)^n, where K is usually called as the WK constant and n is the exponent whose value varies from 0.48 to 0.52. dP is the differential pressure from the pair of pressure taps placed on the SC.  

    Although the method has very high repeatability, some discrepancies were noticed in previous studies. The reasons are often attributed to the change in local flow conditions due to the change in inflow conditions, corrosions, or change in geometry. Paper A is a review of the WK method, which includes the possible factors that can influence the WK method. Considering the possible factors, the aim of this thesis is to study the change in flow behavior and its impact on the coefficients. Therefore, a numerical model of a Kaplan turbine has been developed. The turbine model of Hölleforsen hydropower plant in Sweden was used in the study. The plant is considered as a low head with 27-m head and a discharge of 230 m3/s. The 1:11 scale model of the prototype is used as the numerical model in this study, which has 0.5 m runner diameter, 4.5 m head, 0.522 m3/s discharge and 595 rpm at its best efficiency point. A sensitivity analysis of the WK method has been performed with the help of CFD simulations. The numerical results are compared with the previously conducted experiment on the model. The study considers four different WK configurations at seven locations along the azimuthal direction. The simulations have been performed with different inlet boundary conditions (Paper B and Paper C) and different runner blade angles (Paper C). The CFD results show that the WK coefficients are sensitive to inlet conditions. The study also concludes that to limit the impact of a change in inflow conditions, runner blade angle on the coefficients, the more suitable WK locations are at the beginning of the SC with the inner pressure tap placed between stay vanes on the top wall.

  • 2.
    Baidar, Binaya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Numerical Study of Wall Shear and Velocities Using a Commercial CFD Code: Some Crucial Aspects to Consider2017Inngår i: Hydro Nepal: Journal of Water, Energy and Environment, ISSN 1998-5452, Vol. 21, s. 45-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the numerical prediction of wall shear and velocities in steady and superposed pulsatile turbulent flow in a pipe, the phenomena that can be observed in hydropower. The previously conducted experiment is a base for this study and some crucial aspects of CFD while using a commercial code have been emphasized. The widely-accepted grid convergence index approach is adopted to quantify the discretization uncertainty and the results are validated against the experiment. The influence of the wall functions applied in the code is also studied with two turbulence models: standard k-ε and kω based SST model. The time-averaged results of superposed flow with small amplitude unsteadiness are equivalent to results from the steady flow. The results and the method used in this paper may be useful for the CFD simulations in hydropower applications like penstock and bifurcations designs.

  • 3.
    Baidar, Binaya
    et al.
    Department of Mechanical Engineering, Kathmandu University.
    Chitrakar, Sailesh
    Department of Mechanical Engineering, Kathmandu University.
    Koirala, Ravi
    Department of Mechanical Engineering, Kathmandu University.
    Neopane, Hari Prasad
    Department of Mechanical Engineering, Kathmandu University.
    Selection of Optimal Number of Francis Runner Blades for a Sediment Laden Micro Hydropower Plant in Nepal2015Inngår i: International Journal of Fluid Machinery and Systems, ISSN 1882-9554, E-ISSN 1882-9554, Vol. 8, nr 4, s. 294-303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study is conducted to identify a better design and optimal number of Francis runner blades for sediment laden high head micro hydropower site, Tara Khola in the Baglung district of Nepal. The runner is designed with in-house code and Computational Fluid Dynamics (CFD) analysis is performed to evaluate the performance with three configurations; 11, 13 and 17 numbers of runner blades. The three sets of runners were also investigated for the sediment erosion tendency. The runner with 13 blades shows better performance at design as well as in variable discharge conditions. 96.2% efficiency is obtained from the runner with 13 blades at the design point, and the runners with 17 and 11 blades have 88.25% and 76.63% efficiencies respectively. Further, the runner with 13 blades has better manufacturability than the runner with 17 blades as it has long and highly curved blade with small gaps between the blades, but it comes with 65% more erosion tendency than in the runner with 17 blades.

  • 4.
    Baidar, Binaya
    et al.
    Department of Mechanical Engineering, Kathmandu University.
    Koirala, Ravi
    Department of Mechanical Engineering, Kathmandu University.
    Neopane, Hari P.
    Department of Mechanical Engineering, Kathmandu University.
    Shrestha, Mahabharat V.
    Resource Management and Rural Empowerment Centre (REMREC), National Rural and Renewable Energy Programme/Alternative Energy Promotion Centre (AEPC).
    Thapa, Bhola
    Department of Mechanical Engineering, Kathmandu University.
    Strategic rehabilitation of the earthquake affected microhydropower plants in Nepal2016Inngår i: IOP Conference Series: Earth and Environment, ISSN 1755-1307, E-ISSN 1755-1315, Vol. 49, nr 10, artikkel-id 102003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Most people in the rural areas of Nepal rely on Micro-hydro Power Plants (MHPs) for their energy sources. With around four decade experiences in design and development of MHPs, Nepalese techno-entrepreneurs have gained wider reputation in the South Asian region and the beyond. However with the lack of competences in developing Francis turbines, majority of the MHPs are equipped with either Pelton of Cross Flow turbine, even though Francis units are suitable. With the devastating earthquake of a 7.6 magnitude that struck in the Gorkha district on Saturday, 25 April 2015, about 76 km northwest of the capital city Kathmandu, and the aftershocks followed claimed more than 8000 lives. It did not leave hydropower plants either. Many big plants have been affected and hundreds of MHPs were damaged, needing short to long term rehabilitation. The preliminary assessment of the 61 affected MHPs in the 6 earthquake affected districts shows more than 50% sites are suitable for Francis turbine. Hence the strategic rehabilitation plan has been developed in the present paper for the affected plants considering issues like geographical shift, dislocation of people and also with the focus on replacing the old turbine with Francis turbine in the suitable sites. The similar strategy can also be implemented in other developing countries with such situations.

  • 5.
    Baidar, Binaya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nicolle, Jonathan
    Institut de recherche d’Hydro-Québec, Varennes, QC, Canada.
    Gandhi, Bhupendra K.
    Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee, India.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sensitivity of the Winter-Kennedy method to different guide vane openings on an axial machine2019Inngår i: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 68, artikkel-id 101585Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work studies the effects of guide vane openings (GVOs) on the Winter-Kennedy (WK) flow measurement method using CFD. The dependence of the WK coefficient with GVOs and its physical mechanism are presented. Although the WK method is reported to be sensitive to different factors including GVO, it is still unclear to which extent the GVO can be changed without modifying the WK coefficient significantly and the mechanism leading to such modification, if any. A numerical model of a Kaplan model turbine with a semi-spiral casing is developed and used to such purpose. Previously conducted experiments on the model turbine are used to validate the numerical results. The magnitude and behavior of the secondary flow are investigated together with the WK coefficients. The GVO is found to have an impact on the WK method, and the impact increases with the GVOs as the flow structure change. A suitable location to minimize the impact of the GVO is suggested. Furthermore, the theoretical WK constant with a suitable location and configuration are also presented; this can be useful in the absence of the measured WK coefficient.

  • 6.
    Baidar, Binaya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nicolle, Jonathan
    Institut de recherche d'Hydro-Québec.
    Gandhi, Bhupendra K.
    Indian Institute of Technology Roorkee.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sensitivity of the Winter-Kennedy method to inlet and runner blade angle change on a Kaplan turbine2019Inngår i: IOP Conference Series: Earth and Environmental Science, Institute of Physics (IOP), 2019, Vol. 240, artikkel-id 022038Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Winter-Kennedy (WK) method is a widely used index testing approach, which provides a relative or index value of the discharge that can allow to determine the on-cam relationship between blade and guide vane angles for Kaplan turbines. However, some discrepancies were noticed in previous studies using the WK approach. In this paper, a numerical model of a Kaplan model turbine is used to study the effects of upstream and downstream flow conditions on the WK coefficients. Experiment on the model turbine is used to validate unsteady CFD calculations. The CFD results show that the inflow condition affects the pressure distribution inside the spiral case and hence the WK results. The WK coefficients fluctuate with high amplitude - suggesting to use a larger sampling time for on-site measurement as well. The study also concludes that to limit the impact of a change in runner blade angle on the coefficients, the more suitable WK locations are at the beginning of the spiral case with the inner pressure tap placed between stay vanes on the top wall.

  • 7.
    Baidar, Binaya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nicolle, Jonathan
    Institut de recherche d'Hydro-Québec, Canada.
    Trivedi, Chirag
    Norwegian University of Science and Technology, NTNU, Norway.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Numerical study of the Winter-Kennedy method: a sensitivity analysis2018Inngår i: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 140, nr 5, artikkel-id 051103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Winter-Kennedy (WK) method is commonly used in relative discharge measurement and to quantify efficiency step-up in hydropower refurbishment projects. The method utilizes the differential pressure between two taps located at a radial section of a spiral case, which is related to the discharge with the help of a coefficient and an exponent. Nearly a century old and widely used, the method has shown some discrepancies when the same coefficient is used after a plant upgrade. The reasons are often attributed to local flow changes. To study the change in flow behavior and its impact on the coefficient, a numerical model of a semi-spiral case (SC) has been developed and the numerical results are compared with experimental results. The simulations of the SC have been performed with different inlet boundary conditions. Comparison between an analytical formulation with the computational fluid dynamics (CFD) results shows that the flow inside an SC is highly three-dimensional (3D). The magnitude of the secondary flow is a function of the inlet boundary conditions. The secondary flow affects the vortex flow distribution and hence the coefficients. For the SC considered in this study, the most stable WK configurations are located toward the bottom from θ =30deg to 45deg after the curve of the SC begins, and on the top between two stay vanes.

  • 8.
    Baidar, Binaya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nicolle, Jonathan
    Institut de recherche d’Hydro-Québec.
    Trivedi, Chirag
    Norwegian University of Science and Technology.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Winter-Kennedy method in hydraulic discharge measurement: Problems and Challenges2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Winter Kennedy (WK) method is a popular way to measure the relative discharge and thus efficiency in Swedish hydropower plants. This is largely motivated by the numerous low head turbines and low cost of the method. WK is an index testing method that provides relative values of hydraulic efficiency by measuring differential pressures in one or two pairs of pressure taps in radial planes of the spiral casing. The method is described in the IEC41 standard. Despite several limitations, it is generally used to verify the increment in efficiency for refurbishment projects and sometimes for the continuous flow rate monitoring. Uncertainties in the results reaching up to 5% have been reported in different researches. Those are often attributed to a change in flow conditions after the refurbishment or in the course of time. However, a proper error analysis has not been performed yet. This paper includes a review of the available literature related to the topic to understand its problems and possible ways to investigate its limitations systematically.

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