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  • 1.
    Amiri, Kaveh
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    An experimental investigation of flow in a Kaplan runner: steady-state and transient2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Water turbines are since some years widely used for grid stabilization purposes according to their exceptional load variation capability which gives them the ability to compensate grid fluctuations initiated by the customer’s consumption or intermittent electricity production systems such as wind and solar power. Different renewable power generation technologies can be combined in mini-grids to electrify isolated villages and extend existing grid networks. In these occasions, small hydro units are also a good option to reduce the overall variability of supply to low levels and provide low‑cost, local electrification solutions. Hence, initially designed hydropower turbines for steady operation at on-design operating condition experience many off-design, start/stop and load variations during their life time according to the nowadays on-demand energy market and introduction of intermittent power generation systems to the electricity market.Start/stop and load variations can be harsh for the turbines due to the time dependent forces exerted on different parts of the turbines, especially rotating parts. Off-design performance of hydropower systems may also result in unfavorable and harmful periodic forces on the rotating parts. Therefore, investigations are required to study these working conditions and consider them in design of new hydropower plants and refurbished turbines. This was the motivation for the experimental investigation of a Kaplan turbine during on-design, off-design and transient operations with focus on the turbine’s rotor. The test case was a 1:3.1 scaled model of Porjus U9; a Kaplan turbine. The first paper deals with pressure measurements on the runner blades of the model under steady state operating conditions to find and quantify the sources of pressure fluctuations exerted on the runner at different operating points. The goal was to investigate the turbine’s performance at the best efficiency point with concentration on the performance of the water supply system and compare it to operations at high load and part load for a constant blades angle. The model results are compared with prototype measurements to corroborate the findings. The second paper presents the model investigations during load acceptance and load rejection. The model was investigated with pressure measurement on the stationary and rotating parts of the turbine under different load variations between part load, high load and best efficiency point. The third paper focuses on velocity measurements in the runner blade channels and at the runner outlet under on-design and off-design operating conditions. The velocity measurements are performed with a laser Doppler anemometry (LDA) system. The results of the model investigations along two propeller curves are presented to investigate the runner blade angle effects on the turbine’s performance.

  • 2.
    Amiri, Kaveh
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Experimental investigation of a Kaplan runner under steady-state and transient operations2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Hydropower is a key part in electricity production nowadays. Hydropower electricity production rose to 3579.5 TWh in 2013, ranked as the second source of electricity production in the world after fossil fuels. It is the principle source of renewable electricity production, producing 16.2% of the electricity in 2013, accounting for 78% of the renewable electricity production in the world. Specifically in Sweden, hydropower is the main source of electricity production producing 47.5% of the required electricity. Nuclear, biomass, and wind placed in the following positions in the ranking in 2013 with 38.4%, 6.5%, and 4.3%, respectively.Besides meeting electricity demand with an environmental-friendly method, hydropower has a unique and important role which is grid regulation: balancing electricity production and consumption. Gas turbines and hydraulic turbines called “Primary reserves” are the only electricity production systems that can be used for fast regulations due to their short start-up time from 1 to 60 s. The obvious environmental problems, air pollution, and costs associated with gas turbines make hydropower a prime alternative whenever applicable. In Sweden, the share of fossil fuels in electricity production is small; 2.8% in 2012 with an average annual growth of -0.7% in the period 2002-2012. Hence, hydropower is practically the only available source used to regulate the grid fluctuations resulting from deregulated market and fast growth of intermittent power generation systems, i.e., solar and wind energy. Hydraulic turbines are subject to frequent off-design and transient operations because of their grid regulation responsibility. Such operating conditions decrease turbine’s efficiency and affect its lifetime significantly. Off-design and transient operation of hydraulic turbines may induce unpredicted pressure fluctuations on the stationary and rotating parts of the turbine. Special attention should be dedicated to the effects of such phenomena on the runner blades because of their importance on the efficiency of the turbine, and their vulnerability to the pressure fluctuations.This thesis presents an experimental investigation on the effects of off-design and transient operation of an axial hydraulic turbine on velocity fields and pressure fluctuations exerted on the runner and the draft tube of a turbine. The investigation was performed on a 1:3.1 scaled model of a Kaplan turbine known as Porjus U9. The main objective was to investigate the effect of operating point on pressure and velocity fluctuations in the runner and the draft tube. Another objective was to study the effect of transient operation on pressure fluctuations exerted on the runner and the draft tube, to investigate the formation and mitigation process of a rotating vortex rope (RVR) within the draft tube. Finally, the effect of the swirl leaving the runner and the draft tube bend on the performance of the turbine was investigated. The study involves pressure measurements on the runner blades and draft tube walls of the turbine, laser Doppler anemometry (LDA) measurements within and after the runner, and particle image velocimetry (PIV) measurements within the draft tube.The pressure and LDA results acquired during steady state operation of the turbine showed different sources of fluctuations on the runner at different operating points resulting in symmetric and asymmetric fluctuating forces on the runner. The pressure measurements during transient operating conditions exhibited pressure fluctuations exerted on the runner during load variations and elucidated some aspects of formation and mitigation process of RVR within the draft tube. The PIV measurements performed after the draft tube bend of the turbine focuses on the physical phenomena resulting in flow asymmetry after the draft tube bend of hydraulic turbines affecting their efficiency.

  • 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.
    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

  • 4.
    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)
  • 5.
    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.

  • 6.
    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

  • 7.
    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.

  • 8.
    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.

  • 9.
    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.

  • 10.
    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.

  • 11.
    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.

  • 12. Amiri, Kaveh
    et al.
    Safari, Alaleh
    Soltani, Mohammad Reza
    Department of Aerospace, Sharif University of Technology, Tehran.
    Investigation on the effect of canard angle of attack and position on the pressure distribution of a wing in a delta canard-wing-body configuration with PSW Software Pocket2009Konferensbidrag (Refereegranskat)
  • 13. Amiri, Kaveh
    et al.
    Soltani, Mohammad Reza
    Department of Aerospace, Sharif University of Technology, Tehran.
    An Investigation on the Effects of Wall Porosity and Side Suction in Transonic Tests2009Ingår i: Journal of Aerospace Science and Technology, ISSN 1735-2134, Vol. 6, nr 2, s. 63-70Artikel i tidskrift (Refereegranskat)
  • 14. Amiri, Kaveh
    et al.
    Soltani, Mohammad Reza
    Department of Aerospace, Sharif University of Technology, Tehran.
    Experimental Investigation of Effects of Suction and Wall Porosity on Flow Quality in a Transonic Wind Tunnel2009Konferensbidrag (Refereegranskat)
  • 15. Amiri, Kaveh
    et al.
    Soltani, Mohammad Reza
    Department of Aerospace, Sharif University of Technology, Tehran.
    Haghiri, Ali
    Amirkabir University of Technology.
    Steady flow quality assessment of a modified transonic wind tunnel2013Ingår i: Scientia Iranica, ISSN 1026-3098, Vol. 20, nr 3, s. 500-507Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An existing operational trisonic wind tunnel is upgraded to improve its performance criterion in the transonic regime. In this research, the test section is modified according to the operational requirements of the various existing transonic wind tunnels. Several perforated walls are designed, manufactured, and installed on the top and bottom sides of the test section. The flow in the test section of the wind tunnel is surveyed for the empty condition prior to testing models. Once satisfactory results regarding the flow quality requirements in the test section under various conditions were achieved, a 2D model, NACA 0012, and a 3D standard model for the transonic wind tunnels, AGARD-B, are manufactured and tested under various conditions for the purpose of integral calibration and validation of the tunnel data. Surface pressure distribution as well as the force and moment data compare well with the existing data from other tunnels for similar models tested under the same conditions.

  • 16.
    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.

  • 17.
    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)
  • 18.
    Dehkharqani, Arash Soltani
    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.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Steady and transient pressure measurements on the runner blades of a Kaplan turbine model2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The development of renewable energy sources has increased the need for power regulation. Power system regulation is mainly performed by hydropower plants through load variations. Additional forces are exerted on the runner blades during these load variations. This paper deals with pressure measurement performed on the blades of a Kaplan turbine model under steady state and load variation conditions. Flow behavior and frequency content of the pressure are investigated and compared to find critical condition in terms of pressure fluctuation. The results show that at various operating points and conditions, different regions of the blade are important. During load rejection, a considerable amount of pressure fluctuations are exerted on the runner blades. These results will be used to define experiments to be performed on the corresponding prototype. On the prototype, the loads acting on the runner blades will be investigated at various operation points similar to the model. In addition, the relation between the frequency content on the blades and loads on the main shaft will be investigated. Comparing results from model and prototype eventually would be valuable to explore the flow characteristics in prototype since CFD simulation of prototype is challenging.

  • 19.
    Sundström, Joel
    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.
    Bergan, Carl
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dahlhaug, Ole Gunnar
    Department of Energy and Process Engineering, Water Power Laboratory, Norwegian University of Science and Technology, Trondheim, Norwegian University of Science and Technology (NTNU), Trondheim.
    LDA measurements in the Francis-99 draft tube cone2014Ingår i: 27th IAHR Symposium on Hydraulic Machinery and Systems, IAHR:: Montreal, Canada, 22-26 September 2014, IOP Publishing Ltd , 2014, artikel-id 22012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Velocity measurements were performed in the draft tube cone of a 1:5.1 scaled model of the Tokke hydropower plant, Norway; also known as the Francis-99 model. Results from the laser Doppler anemometry measurements undertaken at three operating points will be used as validation data for an upcoming workshop on the state of the art of Francis turbine numerical simulation. With the turbine operating at the best efficiency point, a sensitivity analysis of the flow parameters head, flow rate and runner rotational speed shows that the effects on the dimensionless velocity profiles are small as long as nED and QED are held constant. The results indicate a well-functioning turbine at the best efficiency point and high load. At the part load operating point, a vortex breakdown occurs which distorts the velocity profiles and significantly lowers the turbine’s hydraulic efficiency. Frequency spectrums of each LDA signal at part load reveals a peak which is asynchronous to that of the runner angular speed. The peaks might be related to the precession of a rotating vortex rope but the characteristics of the LDA signals are different compared to previous studies involving rotating vortex ropes.

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