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  • 1.
    Amiri, Kaveh
    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.
    Mulu, Berhanu
    Vattenfall Research and Development, Älvkarleby.
    Experimental investigation of the hydraulic loads on the runner of a Kaplan turbine model and the corresponding prototype2015Ingår i: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 53, nr 4, s. 452-465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper reports on unsteady pressure measurements on the runner blades of a Kaplan turbine model as well as torque and radial load bearing measurements on the corresponding prototype at several operating points to investigate the sources of periodic loads exerted on the runner when operating at the best efficiency point and off design. Pressure measurements on the model runner blades indicated that the spiral casing delivers a poorly conditioned flow to the guide vanes close to the lip-entrance junction, resulting in flow separation on the guide vanes. The asymmetric flow delivered to the runner induces large oscillations with respect to the guide vane passing frequency, runner frequency and its harmonics to the runner blades. The torque measurements on the prototype also revealed an asymmetric flow at the distributor outlet. The bearing radial load measurements performed on the prototype support the torque measurement results. The asymmetric hydraulic loads on the runner result in shaft wobbling, and the oscillatory forces exerted on the blades are transferred to the main shaft and bearings. Another source of oscillating forces exerted on the runner blades is the rotating vortex rope (RVR) formation that occurs at part-load operation of the turbine and induces pressure fluctuations at two sub-synchronous frequencies to the runner.Keywords: Bearing load; blade pressure measurement; flow-induced vibration; Kaplan turbine; prototype measurement; spiral casingperformance

  • 2.
    Amiri, Kaveh
    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.
    Mulu, Berhanu
    Vattenfall Research & Development.
    Raisee, Mehrdad
    Mechanical Engineering Department, University of Tehran.
    Experimental study of fluid structure interaction in a Kaplan turbine runner blade2013Konferensbidrag (Refereegranskat)
  • 3.
    Amiri, Kaveh
    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.
    Raisee, M.
    School of Mechanical Engineering, University of Tehran.
    Effects of flow unsteadiness on the wall shear stress2012Ingår i: 26th IAHR Symposium on Hydraulic Machinery and Systems: 19–23 August 2012, Beijing, China, IOP Publishing Ltd , 2012, s. 62033-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Measurements were performed on pulsating fully turbulent flows in a pipe test rig with a diameter of 100 mm. Sinusoidal oscillatory flow at different frequencies was superimposed on a mean flow of averaged Reynolds number Re=20000 based on the pipe diameter. The measurements have been performed at different forcing frequencies (0.001 < ω+ < 0.08) covering all the oscillatory regimes; quasi-steady, relaxation, quasi laminar and high frequency. The amplitude of the flow oscillation was small enough to allow a linear response in the measurements, i.e., all flow parameters showed an oscillatory behavior at the frequency of the flow. The amplitude of the oscillatory flow was about 10% of the mean velocity in all cases. The results include mean and phase averaged values of different parameters. The centerline velocity was measured by a 2D LDA system. Hot film and constant temperature anemometry system was used to determine the wall shear stress. Bulk velocity and pressure gradient along the pipe were also acquired. The results showed a good agreement with the previous analytical, experimental and numerical results available in the literature.

  • 4.
    Amiri, Kaveh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Mulu, Berhanu
    Vattenfall Research and Development, Älvkarleby.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Experimental Investigation of the Interblade Flow in a Kaplan Runner at Several Operating Points Using Laser Doppler Anemometry2016Ingår i: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 138, nr 2, artikel-id 21106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents laser Doppler anemometry (LDA) measurements within the runner blade channels and at the runner outlet of a Kaplan turbine model. The model was investigated at six operating points located on two propeller curves of the turbine to study the flow condition during on-cam and off-cam operations. Main and secondary flows within and after the runner were analyzed, and the effects of the hub and tip clearances on the velocity fields within and after the runner were evaluated. Operation of the turbine at flow rates that are lower than the designed rate for the corresponding propeller curve resulted in vortex breakdown and the formation of a rotating vortex rope (RVR). The RVR formation produced an asymmetrical velocity distribution within and after the runner. The results demonstrated the occurrence of an oscillating flow with the same frequency as the vortex rope within the blade channels located upstream of the RVR. This results in an asymmetric flow through the runner and oscillating forces on the runner blades. The measured velocities indicated that the geometrical asymmetries in the runner manufacturing process resulted in various flow asymmetries at the measured sections. The asymmetries were up to 3% within the runner and 7% at the runner outlet

  • 5.
    Amiri, Kaveh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Mulu, Berhanu
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Raisee, Mehrdad
    School of Mechanical Engineering, University of Tehran, Mechanical Engineering Department, University of Tehran.
    Effects of load variation on a Kaplan turbine runner2016Ingår i: International Journal of Fluid Machinery and Systems, ISSN 1882-9554, E-ISSN 1882-9554, Vol. 9, nr 2, s. 182-193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Introduction of intermittent electricity production systems like wind and solar power to electricity market together with the deregulation of electricity markets resulted in numerous start/stops, load variations and off-design operation of water turbines. Hydraulic turbines suffer from the varying loads exerted on their stationary and rotating parts during load variations they are not designed for such operating conditions. Investigations on part load operation of single regulated turbines, i.e., Francis and propeller, proved the formation of a rotating vortex rope (RVR) in the draft tube. The RVR induces pressure pulsations in the axial and rotating direction called plunging and rotating modes, respectively. This results in oscillating forces with two different frequencies on the runner blades, bearings and other rotating parts of the turbine. This study investigates the effect of transient operations on the pressure fluctuations exerted on the runner and mechanism of the RVR formation/mitigation. Draft tube and runner blades of the Porjus U9 model, a Kaplan turbine, were equipped with pressure sensors for this purpose. The model was run in off-cam mode during different load variations. The results showed that the transients between the best efficiency point and the high load occurs in a smooth way. However, during transitions to the part load a RVR forms in the draft tube which induces high level of fluctuations with two frequencies on the runner; plunging and rotating mode. Formation of the RVR during the load rejections coincides with sudden pressure change on the runner while its mitigation occurs in a smooth way.

  • 6.
    Amiri, Kaveh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Mulu, Berhanu G.
    Vattenfall Research and Development, Älvkarleby.
    Raisee, Mehrdad
    Mechanical Engineering Department, University of Tehran.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Effects of upstream flow conditions on runner pressure fluctuations2017Ingår i: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 10, nr 4, s. 1045-1059Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rotor-stator interaction and the corresponding pressure fluctuations represent one of the sources of pressure and load fluctuations on the rotating parts of rotating machineries. The high-Reynolds flow is subject to rotation in the comparably large vaneless space of axial turbines, causing wake interaction and wake dissipation in this region. This increases the level of flow complexity in this region. This study examined the effect of the flow condition entering the spiral casing on the flow condition within the distributor and the runner and the physical source of pressure fluctuations exerted on the runner of a Kaplan turbine model. Simulations were performed within the water supply system, including the upstream tank, penstock, and the Francis turbines, the level of entering the spiral casing; the results were compared with laser Doppler anemometry (LDA) results. The results were considered as the inlet boundary condition for simulation of the turbine model from the spiral inlet to the draft tube outlet to investigate the flow condition within the distributor and the runner. The CFD simulations showed that the water supply system induces inhomogeneity to the velocity distribution at the spiral inlet. However, the flow condition does not affect the pressure fluctuations exerted on the runner blades due to the rotor-stator interactions. Moreover, the dominant frequencies exerted on the runner blades were accurately approximated although the amplitudes of the fluctuations were underestimated.

  • 7.
    Amiri, Kaveh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Mulu, Berhanu
    Raisee, Mehrdad
    School of Mechanical Engineering, University of Tehran, Mechanical Engineering Department, University of Tehran.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Experimental study on flow asymmetry after the draft tube bend of a Kaplan turbine2016Ingår i: Advances and Applications in Fluid Mechanics, ISSN 0973-4686, Vol. 19, nr 2, s. 441-472Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Flow condition in a Kaplan turbine draft tube is investigated using laser Doppler anemometry (LDA) and particle image velocimetry(PIV). The investigated draft tube is composed of a cone followed by an elbow and a straight diffuser. The three velocity components were measured after the elbow at two different locations across the straight diffuser to quantify the flow asymmetry as well as the secondary flows formed in this region. The velocity profiles at the draft tube inlet are measured using a 2D LDA system allowing estimation of the draft tube inlet swirl. The results are presented at three operating points of the turbine. The flow condition after the draft tube bend was shown to be highly dependent on the vortex structures within the straight draft tube; namely Dean vortices and the swirl leaving the runner. At operating points with high flow rates and low swirl, Dean vortices dominate the upstream swirl; a symmetric but inhomogeneous flow resembling flow after a pipe bend forms within the straight diffuser. At part load operating points with high swirl and low flow rate, the flow after the bend is dominated by the upstream swirl resulting in asymmetric flow after the draft tube bend. The flow asymmetry is shown to be a 2nd order function of the swirl-to-Dean ratio.

  • 8.
    Amiri, Kaveh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Mulu, Berhanu
    Vattenfall Research & Development.
    Raisee, Mehrdad
    School of Mechanical Engineering, University of Tehran, Mechanical Engineering Department, University of Tehran.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Load variation effects on the pressure fluctuations exerted on a Kaplan turbine runner2014Ingår i: 27th IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2014: Montreal, Canada, 22- 26 September 2014 / [ed] A-M Giroux, IOP Publishing Ltd , 2014, artikel-id 32005Konferensbidrag (Refereegranskat)
    Abstract [en]

    Introduction of intermittent electricity production systems like wind power and solar systems to electricity market together with the consumption-based electricity production resulted in numerous start/stops, load variations and off-design operation of water turbines. The hydropower systems suffer from the varying loads exerted on the stationary and rotating parts of the turbines during load variations which they are not designed for. On the other hand, investigations on part load operation of single regulated turbines, i.e., Francis and propeller, proved the formation of rotating vortex rope (RVR) in the draft tube. The RVR induces oscillating flow both in plunging and rotating modes which results in oscillating force with two different frequencies on the runner blades, bearings and other rotating parts of the turbine. The purpose of this study is to investigate the effect of transient operations on the pressure fluctuations on the runner and mechanism of the RVR formation/mitigation. Draft tube and runner blades of the Porjus U9 model, a Kaplan turbine, were equipped with pressure sensors. The model was run in off-cam mode during different load variation conditions to check the runner performance under unsteady condition. The results showed that the transients between the best efficiency point and the high load happens in a smooth way while transitions to/from the part load, where rotating vortex rope (RVR) forms in the draft tube induces high level of fluctuations with two frequencies on the runner; plunging and rotating mode of the RVR.

  • 9.
    Amiri, Kaveh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Mulu, Berhanu
    Vattenfall Research and Development, Älvkarleby.
    Raisee, Mehrdad
    School of Mechanical Engineering, University of Tehran, Mechanical Engineering Department, University of Tehran.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Unsteady pressure measurements on the runner of a Kaplan turbine during load acceptance and load rejection2016Ingår i: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 54, nr 1, s. 56-73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper addresses unsteady pressure measurements on the blades and stationary parts of a Kaplan turbine model (Porjus U9) during load variation. The turbine was studied in various load acceptance and load rejection scenarios in off-cam mode to investigate the effect of the transients on the turbine performance. The formation and mitigation processes for the rotating vortex ropes and their effects on the forces exerted on the runner were also investigated. The results show a smooth transition during load variations between high load and the best efficiency point, at which no rotating vortex ropes form in the draft tube. However, load variation to part load resulted in a draft tube surge and the formation of a rotating vortex rope with two fluctuating components: rotating and plunging. The rotating vortex ropes began to form at the end of the draft tube cone during the closure of the guide vanes and travelled upstream with further guide vane closure. The plunging mode induced flow oscillation throughout the entire turbine conduit, whereas the rotating mode resulted in local pressure fluctuations. The rotating vortex ropes induced wide-band pressure fluctuations on the suction side of the runner close to the hub section. The formation of the rotating vortex ropes near the runner resulted in a sudden change in the pressure exerted on the suction side of the blades, whereas the rotating vortex rope mitigation process proceeded in a smooth manner.

  • 10.
    Andersson, Urban
    et al.
    Vattenfall Research & Development.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Phase resolved velocity measurements at the draft tube cone of the turbine-99 test case2008Ingår i: Hydro technology and the evironment for the new century: 24th IAHR Symposium on Hydraulic Machinery and Systems, October 27 - 31, 2008, Foz do Iguassu, Brazil, Foz do Iguassu, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Turbine-99 test case, a Kaplan draft tube, has been studied extensively both experimentally and numerically. To further complete the experimental data of this test case, phase resolved velocity profiles in the draft tube cone are presented in this paper. The phase resolved velocity profiles have been measured with a 2-component LDA equipment measuring both the tangential and the axial velocity components of the flow. The measurements were synchronised with a pulse from the runner shaft that gives the angular position/phase of each velocity measurement. The result shows a clear impact of the runner blade wakes on the flow distribution in the draft tube cone. Further down in the cone the blade wakes are still visible, even if noticeable weaker, and they have increased their extent in the tangential direction.

  • 11.
    Andersson, Urban
    et al.
    Vattenfall Research & Development.
    Jungstedt, J.
    Vattenfall Research & Development.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A model experiment of dynamic loads on a draft tube pier2008Ingår i: Hydro technology and the evironment for the new century: 24th IAHR Symposium on Hydraulic Machinery and Systems, October 27 - 31, 2008, Foz do Iguassu, Brazil, Foz do Iguassu, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cracks on the pier of large draft tubes have occurred causing stand-still and repair of two large twin stations Porjus G11 and G12. In order to understand the mechanism behind the formation of the cracks, a research programme was initiated at Vattenfall. Measurements were performed on a prototype as well structural analysis (FEM). In order to corroborate some findings, get detailed information of the load on the pier and identify critical operating conditions, model tests were performed at the Hydraulic Machinery Laboratory of Vattenfall Research and Development, Älvkarleby, Sweden. An adjustable draft tube pier with several pressure holes was used to estimate the load acting on the pier. The tests did not indicate any operating point that would cause direct braking, but possible fatigue problems. At part load the pressure was considerably higher on one side of the pier. The pressure difference decreases with increased flow, and change high-pressure side at full load. Efficiency measurements and visualization did not show any impact of the angle bars installed in the year 2000 to strength the structure.

  • 12.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Cervantes, Michel J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Maximum power point tracking for micro hydro power plants using extremum seeking control2015Ingår i: 2015 IEEE International Conference on Control Applications (CCA 2015): Sydney, Australia, September 21-23 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 1874-1879, artikel-id 7320883Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we propose using extremum seeking control (ESC) as a tool for maximum power point tracking in micro hydro power plants. The phasor ESC, which is based on estimating the phasor of the plant output at the perturbation frequency, was modified by stimating the phasors of multiple harmonics of this frequency. This modification will improve the performance of ESC by reducing the luctuations in control variables that may appear in noisy environments as a result of high-amplitude perturbation signals. A test rig was used to experimentally verify the proposed approach and to demonstrate the usability of ESC in hydro power plants.

  • 13.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Cervantes, Michel J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Phasor Extremum Seeking and its Application in Kaplan Turbine Control2014Ingår i: 2014 IEEE International Conference on Control Applications (CCA 2014): Juan Les Antibes, France, 8 -10 October 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 298-303Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Combinator is an important part in Kaplan turbine control. It ensures that the turbine will operate in an optimum way, in terms of maximum efficiency of the plant. This work suggests a new sinusoidal perturbation based extremum seeking algorithm based on the phasor of the output. We propose to use this algorithm for generating the required data to build and correct the combinator. Simulations are presented showing the applicability of the proposed methods.

  • 14.
    Backman, Gunnar
    et al.
    Rainpower Norway AS.
    Billdal, J.T.
    Rainpower Norway AS.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Farhat, Mohamed
    EPFL LMH Laboratory, Switzerland.
    Zobeiri, A.R.
    EPFL LMH Laboratory, Switzerland.
    Increased need for hydro pumped-storage plants to guarantee the stability of the power grids2008Ingår i: HYDRO 2008, Progressing World Hydro Development: Ljubljana, Slovenina, 6-8 October 2008, 2008Konferensbidrag (Refereegranskat)
  • 15.
    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 Consider2017Ingår i: Hydro Nepal: Journal of Water, Energy and Environment, ISSN 1998-5452, Vol. 21, s. 45-49Artikel i tidskrift (Refereegranskat)
    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.

  • 16.
    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 machine2019Ingår i: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 68, artikel-id 101585Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    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 turbine2019Ingår i: IOP Conference Series: Earth and Environmental Science, Institute of Physics (IOP), 2019, Vol. 240, artikel-id 022038Konferensbidrag (Refereegranskat)
    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.

  • 18.
    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 analysis2018Ingår i: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 140, nr 5, artikel-id 051103Artikel i tidskrift (Refereegranskat)
    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.

  • 19.
    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 Challenges2016Konferensbidrag (Refereegranskat)
    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.

  • 20.
    Bergan, Carl
    et al.
    Department of Energy and Process Engineering, Water Power Laboratory, Norwegian University of Science and Technology, Trondheim.
    Amiri, Kaveh
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. Department of Engineering Sciences and Mathematics, Luleå University of Technology.
    Cervantes, Michel J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. Department of Energy and Process Engineering, Water Power Laboratory, Norwegian University of Science and Technology, Trondheim.
    Dahlhaug, Ole G.
    Department of Energy and Process Engineering, Water Power Laboratory, Norwegian University of Science and Technology, Trondheim.
    Preliminary measurements of the radial velocity in the Francis-99 draft tube cone2015Ingår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 579, nr 1, artikel-id 12014Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two-dimensional particle image velocimetry (PIV) measurements in the draft tube cone of the Francis-99 model have been performed to complete the actual experimental data set with radial velocity data. The velocity profiles obtained presented some variation, which reason has not yet been identified. The presented results are therefore presented as preliminary until the reason is assessed. The axial velocity profiles corroborate well with the ones previously measured with laser Doppler velocimetry (LDV) for all operating points investigated. The radial velocity measured is small in magnitude for all operating points compared to the axial velocity. A gyroscopic effect induced by the swirl leaving the runner and the draft tube bend seems to induce an asymmetry in the draft tube cone.

  • 21.
    Bergan, Carl
    et al.
    Waterpower Laboratory, Norwegian University of Science and Technology.
    Goyal, Rahul
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. Indian Institute of Technology Roorkee.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dalhaug, Ole Gunnar
    Waterpower Laboratory, Norwegian University of Science and Technology.
    Experimental Investigation of a High Head Model Francis Turbine During Steady-State Operation at Off-Design Conditions2016Ingår i: IOP Conference Series: Earth and Environment, ISSN 1755-1307, E-ISSN 1755-1315, Vol. 49, nr 8, artikel-id 062018Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francis-99 is a set of workshops aiming to determine the state of the art of high head Francis turbine simulations (flow and structure) under steady and transient operating conditions as well as promote their development and knowledge dissemination openly. The first workshop (Trondheim, 2014) focused on steady state conditions. Some concerns were raised regarding uncertainty in the measurements, mainly that there was no clear vortex rope at the Part Load (PL) condition, and that the flow exhibited relatively large asymmetry. The present paper addresses these concerns in order to ensure the quality of the data presented in further workshops. To answer some of these questions, a new set of measurements were performed on the Francis 99 model at Waterpower Laboratory at the Norwegian University of Science and Technology (NTNU). In addition to PL, two other operating conditions were considered, for further use in transient measurements, Best Efficiency (BEP) and High Load (HL). The experiments were carried out at a head of 12 m, with a runner rotational speed of 333 revolutions per minute (rpm). The guide vane opening angle were 6.72 degrees, 9.84 degrees and 12.43 degrees for PL, BEP and HL, respectively. The part load condition has been changed from the first workshop, to ensure a fully developed Rotating Vortex Rope (RVR). The velocity and pressure measurements were carried out in the draft tube cone using 2D PIV and six pressure sensors, respectively. The new PL condition shows a fully developed rotating vortex rope (RVR) in both the frequency analysis and in the phase resolved data. In addition, the measurements confirm an asymmetric flow leaving the runner, as was a concern in the first Francis-99 workshop. This asymmetry was detected at both design and off-design conditions, with a stronger effect during off design.

  • 22.
    Bucur, Diana
    et al.
    POLITEHNICA University of Bucharest.
    Dunca, Georgiana
    POLITEHNICA University of Bucharest.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Clinoiu, C.
    POLITEHNICA University of Bucharest.
    Isbşoiu, E.C.
    POLITEHNICA University of Bucharest.
    Simultaneous transient operation of a high head hydro power plant and a storage pumping station in the same hydraulic scheme2014Ingår i: 27th IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2014: Montreal, Canada, 22 - 26 September 2014 / [ed] C. Deschenes, IOP Publishing Ltd , 2014, artikel-id 42015Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an on-site experimental analysis of a high head hydro power plant and a storage pumping station, in an interconnected complex hydraulic scheme during simultaneous transient operation. The investigated hydropower site has a unique structure as the pumping station discharges the water into the hydropower plant penstock. The operation regimes were chosen for critical scenarios such as sudden load rejections of the turbines as well as start-ups and stops with different combinations of the hydraulic turbines and pumps operation. Several parameters were simultaneously measured such as the pumped water discharge, the pressure at the inlet pump section, at the outlet of the pumps and at the vane house of the hydraulic power plant surge tank. The results showed the dependence of the turbines and the pumps operation. Simultaneous operation of the turbines and the pumps is possible in safe conditions, without endangering the machines or the structures. Furthermore, simultaneous operation of the pumping station together with the hydropower plant increases the overall hydraulic efficiency of the site since shortening the discharge circuit of the pumps.

  • 23.
    Bucur, Diana Maria
    et al.
    University POLITEHNICA of Bucharest.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dunca, Georgiana
    University POLITEHNICA of Bucharest.
    Maximum pressure evaluation during expulsion of entrapped air from pressurized pipelines2017Ingår i: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 10, nr 1, s. 11-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressurized pipeline systems may have a wide operating regime. This paper presents the experimental analysis of the transient flow in a horizontal pipe containing an air pocket, which allows the ventilation of the air after the pressurization of the hydraulic system, through an orifice placed at the downstream end. The measurements are made on a laboratory set-up, for different supply pressures and various geometries of water column length, air pocket and expulsion orifice diameter. Dimensional analysis is carried out in order to determine a relation between the parameters influencing the maximum pressure value. A two equations model is obtained and a criterion is established for their use. The equations are validated with experimental data from the present laboratory set-up and with other data available in the literature. The results presented as nondimensional quantities variations show a good agreement with the previous experimental and analytical researches.

  • 24.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A reaction probe for flow measurements in liquid steel1998Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 25.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Counter rotating runner cone in a Kaplan elbow draft tube for increased efficiency2009Ingår i: Proceedings of the 3rd IAHR International Meeting of the WorkGroup on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems / [ed] Pavel Rudolf, Brno: Brno University of Technology , 2009, s. 133-142Konferensbidrag (Refereegranskat)
  • 26.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Effect of surface roughness on a counter rotating runner cone2010Konferensbidrag (Refereegranskat)
  • 27.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Effects of boundary conditions and unsteadiness on draft tube flow2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The present research focuses on flow properties of the elbow draft tube. This element has a major function in low head turbines, since up to half of the losses may arise there at part load. The use of computational fluid dynamic (CFD) to redisign a draft tube necessitates detailed knowledged of the boundary conditions. They are generally not available and qualified guesses must be made. This applies in particular to the radial velocity at the inlet. A method to estimate this component in swirling flow from experimental values of the axial and tangential velocities is derived. The method uses a two dimensional non- viscous description of the flow, the Squire-Long formulation. It is tested against swirling flow in a diffuser and applied to the Turbine-99 draft tube flow. As several other boundary conditions are difficult to estimate and many input parameters are available to perform a simulation, the use of factorial design is proposed as an alternative to design simulations in a systematic, objective and quantitative way. The method allows the deternmination of the main and joint effects of input parameters on the numerical simulation. The input parameters may be experimental uncertainty on boundary conditions, unknown boundary conditions, grid and turbulence models. The method is applied to the Turbine-99 test case, where the radial velocity, the surface roughness, the turbulence length scale and the grid were the factors investigated. The inlet radial velocity is found to have a major effect on the pressure recovery. The flow in water turbines is highly unsteady due to the runner blade rotation, guide vanes and stay vanes. Unsteady pressure measurements on a Kaplan prototype point out unsteadiness in the high and low pressure regions of the turbine. Since model and prototype are not running in dynamically similar conditions, the influence of unsteadiness on the losses is of interest. The derivation of the variation of the mechanical energy for the mean, oscillating and turbulent fields point out the contribution of unsteadiness to the losses and the turbulent production. Application to turbulent channel flow reveals that the contribution is a function of the amplitude of the oscillation, the frequency and the friction velocity. Turbulent pulsating flow in a generic model of the rectangular diffuser found at the end of elbow draft tube is studied in detail with laser Doppler anemometry (LDA). Three frequencies, corresponding to the quasi-steady, relaxation and quasi-laminar regimes with an amplitude of about 10% are investigated. The results indicate no alteration of the mean flow by the excitation of a single frequency. Furthermore. the existence of the different regimes, as found in turbulent pulsating turbulent pipe and channel flows, is confirmed.

  • 28.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hydropower engineering2005Ingår i: Proceedings of the International Green Energy Conference: IGEC-1, Waterloo, Ontario: University of Waterloo , Dept. of Mechnical Engineering , 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    Hydropower, one of the corner stones of sustainable energy development, is the largest renewable source of energy. There is a large demand worldwide for people trained to design, operate, maintain and optimise hydropower systems. Hydro Power University, a name which encompasses both education, research and development within hydropower in Sweden, offers a unique and broad international masters programme within hydropower engineering including civil, mechanical and electrical engineering. The programme is the result of a close collaboration between Lulea University of Technology and Uppsala University, at the research and education level. This master programme, Hydropower Engineering, is open to both Swedish and foreign students free of charge. It aims to provide students with state of the art knowledge and experience on parts of the hydropower system such as turbine technology, generator design, rotor dynamics, tribology, dams/dam safety, maintenance and operation and environmental aspects. World unique laboratory experiments are offered to the students at Porjus and Alvkarleby, Sweden. The Porjus Hydropower Centre offers world unique facilities: two full scale turbines of 10 MW each, one with the latest generator technology - Powerformer. The turbines are exclusively dedicated for use in education, research and development. State of the art in measurement technology is available. Both units are at the centre of each education programme offered by the Hydro Power University. In Alvkarleby, spillways, discharge capacity and turbines model testing can be undertaken at the Vattenfall laboratory also with state of the art experimental material and highly qualified staff. The large number of applications from developing countries indicates a need of scholarships, which needs to be resolved for the development of hydropower

  • 29.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hydropower Engineering: an International Master Programme at Luleå University of Technology2005Ingår i: International Water Power and Dam Construction, ISSN 0306-400X, E-ISSN 1538-6414, Vol. 57, nr 8, s. 42-44Artikel i tidskrift (Övrigt vetenskapligt)
  • 30.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Runner cone boundary layer control2007Ingår i: Proceedings of the 2nd IAHR International Meeting of the Workgroup on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Timisoara,Romania, October 24-26, 2007 / [ed] R. Susan-Resiga; S. Bernad; S. Muntean, Timişoara, 2007, s. 153-158Konferensbidrag (Refereegranskat)
    Abstract [en]

    The runner cone plays an essential role in the performance of elbow draft tube and de facto of low head machines. An earlier separation on the runner cone deteriorates the pressure recovery and thus the overall efficiency of the machine. Control of the separation point on the runner cone is therefore of interest to improve efficiency at any regime. Onealternative to control the separation on the runner cone may be to rotate the runner cone with a different angular velocity than the runner blades. In the present work, the effect of runner cone angular rotation on elbow draft tube, typical in Kaplan turbine, is investigated using numerical simulations. The Turbine-99 test case (T-99) is used as benchmark at the top of the propeller curve. Simulations are performed for 4 different angular rotations: -595(stipulated in T-99), 0, +600 and +1200 rpm. The results indicate a delay of the separation on the cone at 0, +600 and +1200 rpm. The mean pressure recovery increases in all cases. The improvement reaches 6.6 % for the mean pressure recovery for an angular velocity of +600 rpm where separation disappear, while the loss factor decreases with 23.6 %.

  • 31.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    To a higher degree: power engineering education2005Ingår i: International Water Power and Dam Construction, ISSN 0306-400X, E-ISSN 1538-6414, Vol. 57, nr 8, s. 42-44Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This paper describes how the need for more skilled professionals in the hydroelectric sector led to the formation of the Hydro Power Engineering Masters Programme at Lulea University of Technology, Sweden. The goal of the Masters program is to allow students to obtain an overall picture of the field, to answer the need of the industry without neglecting the content. Such a program aims to give the student a choice between a position as a specialist within a specific area and a management position where discussions with specialists are required

  • 32.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Turbine-99 III, 3rd IAHR workshop on draft tube flow2006Ingår i: ERCOFTAC bulletin, Vol. 69, s. 9-19Artikel i tidskrift (Övrigt vetenskapligt)
  • 33.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Velocity measurement in liquid steel1998Ingår i: Journées Sidérurgiques Internationales ATS 98: [Paris, 1er et 2 décembre 1998 ; résumés des communications/summaries of papers], 1998Konferensbidrag (Refereegranskat)
  • 34.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Aidanpää, Jan-Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Glavatskih, Sergei
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Karlsson, Thommy
    Interdisciplinary research in full-scale hydropower machines at Porjus, Jokkmokk, Sweden2005Ingår i: International Water Power and Dam Construction, ISSN 0306-400X, E-ISSN 1538-6414, Vol. 57, nr 12, s. 40-44Artikel i tidskrift (Övrigt vetenskapligt)
  • 35.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Aidanpää, Jan-Olov
    Glavatskikh, Sergei
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Karlsson, Thommy
    Group dynamics [hydro power equipment]2005Ingår i: International Water Power and Dam Construction, ISSN 0306-400X, E-ISSN 1538-6414, Vol. 57, nr 12, s. 40-45Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    An interdisciplinary research group was created at the Lulea University of Technology in Sweden to help develop world leading competencies and knowledge for cutting-edge technologies in hydro power generation. Based on the studies of this Swedish research group, this paper provides a description of the power system from a dynamic point of view to obtain an overall picture, and is completed with a detailed description of the bearings and turbines. The state-of-the-art in each field is presented, together with suggestions for further development

  • 36.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Amiri, Kaveh
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Rotor-Stator interaction in Kaplan turbines during steady and transient operations2013Konferensbidrag (Refereegranskat)
  • 37.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, Uban
    Vattenfall Research & Development.
    Lövgren, Magnus
    Vattenfall Research & Development.
    Turbine-99 unsteady simulations: validation2010Ingår i: 25th IAHR Symposium on Hydraulic Machinery and Systems: 20-24 September 2010 'Politehnica' University of Timişoara, Timişoara, Romania, London: IOP Publishing Ltd , 2010, s. 12014-Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Turbine-99 test case, a Kaplan draft tube model, aimed to determine the state of the art within draft tube simulation. Three workshops were organized on the matter in 1999, 2001 and 2005 where the geometry and experimental data were provided as boundary conditions to the participants. Since the last workshop, computational power and flow modelling have been developed and the available data completed with unsteady pressure measurements and phase resolved velocity measurements in the cone. Such new set of data together with the corresponding phase resolved velocity boundary conditions offer new possibilities to validate unsteady numerical simulations in Kaplan draft tube. The present work presents simulation of the Turbine-99 test case with time dependent angular resolved inlet velocity boundary conditions. Different grids and time steps are investigated. The results are compared to experimental time dependent pressure and velocity measurements

  • 38.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andrée, Gunilla
    Vattenfall.
    Klason, Peter
    Sundström, Joel
    Elforsk.
    Flow measurements in low-head hydro power plants2012Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Vattenkraft står för ca 50% av elproduktionen i Sverige. De flesta av verken byggdes för flera årtionden sedan och kommer successivt att behöva förnyas. Förnyelsen har påbörjats och kommer kontinuerligt att fortsätta. Betydande produktionsvinster och anpassning till nya marknadskrav kan uppnås i förnyelsen och den stimuleras också av staten genom elcertifikatsystemet. Verkningsgradhöjningar är således av vikt, men utgör en utmaning i de lågfallhöjdsmaskiner (H <50 m) som dominerar i Sverige. Under de senaste decennierna har Winter-Kennedy metoden använts för att kontrollera förbättringar av verkningsgrad genom att mäta före och efter en renovering. Resultaten har i ett antal fall visat oförutsägbara resultat. Det finns ett behov av utveckling för att noggrant mäta verkningsgrad för att utvärdera resultatet av olika förnyelseprojekt.En arbetsgrupp har därför bildats inom Svenskt VattenkraftCentrum med representanter från vattenkraft- och turbinbranschen i Sverige för att identifiera insatser för att utveckla flödesmätning i lågfallhöjdsturbiner. I denna rapport presenteras olika flödesmätningsmetoder som finns med deras utvecklingsstatus och potential att möta behoven för lågfallhöjdsmaskiner.Arbetsgruppen föreslår flera insatser för att utveckla flödesmätning i lågfallhöjdsmaskiner. De är indelade i två kategorier: lång och kort sikt. De långsiktiga insatserna är typiska SVC-projekt för doktorander och/eller seniora forskare, medan de kortsiktiga insatserna är projekt för konsult och/eller seniora forskare. Följande insatser föreslås i prioritetsordning:Långsiktiga projekt1. Utveckling av ”pressure-time”-metoden som en absolut och relativ metod2. Utvärdering av skallagar och inflytande av parametrarna som skiljer sig mellan modell och prototyp, såsom spiralens inloppsrandvillkorKortsiktiga projekt1. Vägledning för genomförande, utvärdering och rapportering av flödesmätningar med Winter-Kennedy metoden. Fortsätta arbetet med de gemensamma riktlinjer som utarbetats i SEK-TK4.2. Systematisk felanalys av flödesmätningar med Winter-Kennedy metoden3. Test av den volymetriska metoden på en fullskalig turbin för att undersöka möjligheter och utvärdera nödvändig utvecklingsbehov för lågfallhöjdsmaskiner4. Test av ”dilution” metoden på en fullskalig turbin för att undersöka möjligheter och utvärdera nödvändig utvecklingsbehov för lågfallhöjdsmaskinerArbetet som presenteras i rapporten har bedrivits inom "Svenskt VattenkraftCentrum – SVC”. SVC har etablerats av Energimyndigheten, Elforsk och Svenska Kraftnät tillsammans med Luleå Tekniska Universitet, Kungliga Tekniska Högskolan, Chalmers Tekniska Högskola och Uppsala Universitet.Medverkande vattenkraftföretag är Alstom, Andritz Hydro, E.ON Vattenkraft Sverige, Fortum Generation, Holmen Energi, Jämtkraft, Karlstads Energi, Linde Energi, Mälarenergi, Skellefteå Kraft, Sollefteåforsens, Statkraft Sverige, Statoil Lubricants, Sweco Infrastructure, Sweco Energuide, SveMin, Umeå Energi, Vattenfall Research and Development, Vattenfall Vattenkraft, VG Power och WSP.

  • 39.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Cupillard, Samuel
    Hydro-Québec Research’s Institute.
    3D thermodynamic analysis of a turbulent textured slider2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sliding contacts under laminar regime have been extensively investigated under the last years. The results indicate the possibility to increase load carrying capacity in a slider bearing with more than 10%. The effect of dimples on a slider bearing under a turbulent regime has not yet been investigated. It is the object of the present study. The numerical analysis of a 3D textured slider bearing with fore-region and extended channels at the outlet and on the sides of a pad is considered with a temperature dependent fluid, 2 different types of dimple shape and different operating conditions. The simulations are carried out for a turbulent flow (Re=4.4•10^3- 15•10^3) using Detached Eddy Simulation. The results indicate no gain on the load carrying capacity with the dimple shapes (rectangular and oblique) investigated. A higher operating temperature is found in the presence of dimples.

  • 40.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Cupillard, Samuel
    Hydro-Québec Research’s Institute.
    Bance, Kevin
    National Institute for Applied Science.
    Kokkolaras, Michael
    McGill University.
    Shape optimization of a 3D slider with dimples2012Ingår i: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 6, nr 12, s. 1599-1607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sliding contacts in laminar flow regimes have been investigated extensively in recent years. The results indicate the possibility to increase load carrying capacity in a slider bearing for more than 10% with the addition of dimples. Parametric studies have been performed to determine optimal size and position, with emphasis in the optimal shape and position of the dimple for an operating condition. In this article, the numerical analysis of a 2D textured slider bearing with a dimple is initially considered with an isothermal laminar fluid. Position, depth, width and convergence ratio are optimized, the results demonstrate the importance of the width and convergence ratio to increase load. Then, the numerical analysis of a 3D textured slider bearing with fore-region and extended channels at the outlet and on the sides of a pad is considered. The simulations are also carried out for a laminar isothermal flow. Three dimples are considered and their depth is optimized.

  • 41.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Cupillard, Samuel
    Hydro-Québec Research’s Institute.
    Kokkolaras, Michael
    University of Michigan.
    Shape optimisation of a 3D slider with a dimple2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sliding contacts under laminar regime have been extensively investigated under the last years. The results indicate the possibility to increase load carrying capacity in a slider bearing with more than 10% with the addition of dimples. Parametric studies have been performed on size and position, while an optimisation to determine the true potential have not yet been examined. Of interest is the optimal shape of the dimple function of the operating condition and position. In the present work, the numerical analysis of a 2D textured slider bearing with fore-region is initially considered with an isothermal laminar fluid. One dimple is considered and the shape optimized for different operating conditions and positions. Then, the numerical analysis of a 3D textured slider bearing with fore-region and extended channels at the outlet and on the sides of a pad is considered with a temper-ature dependent fluid. The simulations are also carried out for a laminar flow. One dimple is considered and the shape optimized for different operating conditions and positions.

  • 42.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Eddy viscosity turbulence models and steady draft tube simulations2005Ingår i: Turbine-99 III: Proceedings of the third IAHR/ERCOFTAC workshop on draft tube flow, Luleå: Luleå tekniska universitet, 2005, s. 37-44Konferensbidrag (Refereegranskat)
    Abstract [en]

    Computations of the Turbine-99 benchmark have been performed for two dimensional steady inlet boundary conditions. Three different turbulence models were used: zero equation model, k-ε and shear stress model (SST). The results from the engineering quantities indicate small differences on the mean pressure recovery and the loss factor, while larger differences appear for the wall pressure recovery.

  • 43.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. Luleå tekniska universitet.
    Factorial design applied to CFD2004Ingår i: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 126, nr 5, s. 791-798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Factorial design, a statistical method widely used for experiments, and its application to CFD are discussed. The aim is to propose a systematic, objective, and quantitative method for engineers to design a set of simulations in order to evaluate main and joint effects of input parameters on the numerical solution. The input parameters may be experimental uncertainty on boundary conditions, unknown boundary conditions, grid, differencing schemes, and turbulence models. The complex flow of the Turbine-99 test case, a hydropower draft tube flow, is used to illustrate the method, where four factors are chosen to perform a 24 factorial design. The radial velocity at the inlet (not measured) is shown to have an important influence on the pressure recovery (7%) and the energy loss factor (49%).

  • 44.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Engström, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik. Vattenfall Power Consultant.
    Pulsating turbulent flow in a straight asymmetric diffuser2008Ingår i: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 46, nr Suppl. 1, s. 112-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pulsating turbulent flow is studied for four regimes: steady, quasi-steady, relaxation, and quasi-laminar in a rectangular straight asymmetric diffuser, a generic model of the diffuser found at the end of most Kaplan and Francis type hydropower turbines. The flow entering the diffuser is a developing duct flow at Reynolds number 20 000, based on mean streamwise velocity and hydraulic diameter. The time averaged velocity and turbulent quantities are not affected by the forced oscillation. The regimes prevail in the diffuser, but are shifted due to the decreasing friction velocity. The oscillating quantities are affected by the adverse pressure gradient in the same way as the time averaged quantities, but with a decreasing effect for higher forcing frequencies. The amplitude of the oscillating wall shear stress is found to be signicantly lower than the Stokes solution in the quasi-laminar regime. The regime is confirmed by the behaviour of several other quantities. The pressure recovery is found to be 30 % higher in the relaxation regime than in the other regimes. Results are compared with experiments in channels and turbulent boundary layers, with and without an adverse pressure gradient, and with large-eddy simulations.

  • 45.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Engström, FredrikLuleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.Gustavsson, Håkan
    Turbine-99 III: Proceedings of the third IAHR/ERCOFTAC workshop on draft tube flow2005Samlingsverk (redaktörskap) (Övrigt vetenskapligt)
    Abstract [en]

    The third IAHR/ERCOFTAC workshop on draft tube flows, Turbine-99 III, is based on the experience gained during the first two workshops and the development of the computational capacities. It is expected to be a step towards better understanding of draft tube flow simulation capabilities. Three cases based on the Turbine-99 benchmark were proposed to the participants: steady calculation, unsteady calculation, optimization of the draft tube performance. More than 30 simulations have been performed by the participants with several turbulence models, near wall treatment, grids and boundary conditions. The complexity of the turbulence models ranges from zero equation model to large eddy simulations. The contribution of the different participants, the protocol of their simulations and a comprehensive comparison of experimental data with the simulations are included in the present document.

  • 46.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Engström, T. Fredrik
    Luleå tekniska universitet.
    Influence of boundary conditions using factorial design2001Ingår i: Proceedings of the Turbine-99 II: Workshop on Draft Tube Flow, 2001Konferensbidrag (Refereegranskat)
  • 47.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Enström, Christer
    MPC Metal Process Control AB.
    Kelvesjö, Håkan
    MPC Metal Process Control AB.
    Ohlsson, Willy
    MPC Metal Process Control AB.
    Method and apparatus for non-contact measuring of metal bed parametersPatent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    In a method and device for measuring at least one parameter of a metal bed, measuring is obtained by a magnetic field being generated from one side of the metal bed so that eddy currents are generated in the metal bed as the metal bed moves relative to the magnetic field. The metal bed and the magnetic field are made to move relative to one another. A force related to the eddy currents affects a body and the action of the force on the body is detected by a detecting device, the detected force being a function of a desired parameter of the metal bed.

  • 48.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gustavsson, Håkan
    Development of a reaction probe for flow measurements in continuous casting of steel1998Ingår i: Proceedings - The 9th International Conference on Flow Measurement: FLOMEKO, Kista: ITF , 1998Konferensbidrag (Refereegranskat)
  • 49.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gustavsson, Håkan
    Estimation of the Radial Velocity from the Squire-Long Equation and Experimental Data2005Ingår i: Waterpower XIV: conference ; advancing technology for sustainable energy ; July 18 - 22, 2005, Austin, Texas, USA ; technical papers, Kansas City: HCI , 2005Konferensbidrag (Refereegranskat)
  • 50.
    Cervantes, Michel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gustavsson, Håkan
    Natural wave frequencies in continuous casting moulds1998Ingår i: Proceedings of the 3rd European Conference on Continuous Casting, 1998Konferensbidrag (Refereegranskat)
12345 1 - 50 av 211
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