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  • 101.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Cervantes, Michel J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Phasor Extremum Seeking and its Application in Kaplan Turbine Control2014In: 2014 IEEE International Conference on Control Applications (CCA 2014): Juan Les Antibes, France, 8 -10 October 2014, Piscataway, NJ: IEEE Communications Society, 2014, p. 298-303Conference paper (Refereed)
    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.

  • 102.
    Trivedi, Chiragkumar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Bhupendrakumar, Gandhi
    Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee.
    Dahlhaug, Ole G.
    Department of Energy and Process Engineering, Water Power Laboratory, Norwegian University of Science and Technology, Trondheim.
    Pressure measurements on a high-head Francis turbine during load acceptance and rejection2014In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 52, no 2, p. 283-297Article in journal (Refereed)
    Abstract [en]

    Hydraulic turbines are frequently used to maintain electrical grid parameters. An angular movement of the guide vanes (GVs) during transients such as load acceptance and rejection within short time raised significant concerns for increased wear and instabilities. The present work focuses on the pressure variations in a high-head Francis turbine during the transients. Six transient conditions were investigated including time-domain rotor–stator interaction. The measurements in the vaneless space and runner indicated the presence of unsteady vortical flow during transients. The vortices travelled to the runner and affected the flow in the blade channels. The GVs angular movement increases the pressure difference between the pressure and suction sides of the blade. The largest pressure variation was observed during the partial load rejection at the trailing edge of the blade. Preliminary results indicated that an appropriate closure of the GVs may minimize large pressure fluctuations in the runner

  • 103.
    Bucur, Diana
    et al.
    POLITEHNICA University of Bucharest.
    Dunca, Georgiana
    POLITEHNICA University of Bucharest.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    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 scheme2014In: 27th IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2014: Montreal, Canada, 22 - 26 September 2014 / [ed] C. Deschenes, IOP Publishing Ltd , 2014, article id 42015Conference paper (Refereed)
    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.

  • 104. Simmons, Gregory F
    et al.
    Cha, Matthew
    Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Glavatskih, Sergei
    Steady state and dynamic characteristics for guide bearings of a hydro-electric unit2014In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 228, no 8, p. 836-848Article in journal (Refereed)
    Abstract [en]

    Experiments are conducted using a 10-MW Kaplan hydropower machine which is outfitted with an extensive array of sensors to determine oil film thickness, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all journal bearings are compared to a commercial rotor dynamics model and results for the central journal bearing are compared to a multi-physics model to provide insight into the machine's steady state and dynamic characteristics and their variations during normal operation.

  • 105.
    Safari, Alaleh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Ginebra, Maria Pau
    Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgy, Technical University of Catalonia.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Studying Water Based Lubricant Behavior in Mini-Channel2014Conference paper (Refereed)
    Abstract [en]

    One of the most common causes of failures in total joint replacements is the generation of wear particles within the joint that leads to the micro separation at the implant-bone interface. This contributes to bone lost aseptic loosening of the implant, requiring eventually its replacement.Many studies have been carried out to improve the wear characteristics of bearing surfaces in total joint replacement (TJR). From lubrication point of view the friction behavior of surfaces and rheology of the joint lubricant (Synovial fluid) were extensively studied. However, not much attention was paid to the interaction between the lubricant and the bearing surfaces. The aim of this study is to develop a methodology for studying the behavior of water based lubricant in a micro-channel. For this purpose, Micro-PIV (Particle Image velocimetry) was used in order to characterize the lubricant behavior. Experimental models made of relevant materials such as ultra high molecular weight polyethylene, Cobalt-Chromium-Molybdenum alloy and Titanium-Aluminum-Vanadium alloy with 1 and 1.5 mm width, 45 mm length and 2 mm depth experimentally investigated.

  • 106. Cupillard, Samuel
    et al.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Glavatskih, Sergei
    Thermohydrodynamic analysis of a journal bearing with a microgroove on the shaft2014In: Computational Thermal Sciences, ISSN 1940-2503, E-ISSN 1940-2554, Vol. 6, no 1, p. 47-57Article in journal (Refereed)
    Abstract [en]

    In this study, thermohydrodynamic performance of a journal bearing with a microgroove created on the shaft is analyzed. A plain journal bearing is modeled using a computational fluid dynamics (CFD) software package. Navier-Stokes and energy equations are solved. The rotor-stator interaction is treated by using a computational grid deformation technique. The goal is to examine the pressure/temperature distribution in the bearing film. Results are presented in terms of typical bearing parameters as well as flow patterns. Results are also compared to the bearing with a smooth shaft. The effect induced by a microgroove on pressure distribution is explained for different bearing configurations, eccentricities, and microgroove depths. It is shown that the microgroove produces a local drop in pressure which, averaged over one revolution, decreases the load carrying capacity. The load carrying capacity is further decreased by using deeper microgrooves. With thermal effects considered, the microgroove carries more cold lubricant into the warmest regions of the bearing. This effect, more pronounced with deeper microgrooves, is due to a global flow recirculation inside the microgroove, which improves mixing

  • 107.
    Trivedi, Chirag
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Bhupendrakumar, Gandhi
    Department of Mechanical and Industrial Engineering, Indian Institute of Technology Roorkee.
    Dahlhaug, Ole Gunnar
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Transient pressure measurements on a high head model Francis turbine during emergency shutdown, total load rejection, and runaway2014In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 136, no 12, article id 121107-1Article in journal (Refereed)
    Abstract [en]

    The penetration of intermittent wind and solar power to the grid network above manageable limits disrupts electrical power grids. Consequently, hydraulic turbines synchronized to the grid experience total load rejection and are forced to shut down immediately. The turbine runner accelerates to runaway speeds in a few seconds, inducing high-amplitude, unsteady pressure loading on the blades. This sometimes results in a failure of the turbine components. Moreover, the unsteady pressure loading significantly affects the operating life of the turbine runner. Transient measurements were carried out on a scale model of a Francis turbine prototype (specific speed = 0.27) during an emergency shutdown with a transition into total load rejection. A detailed analysis of variables such as the head, discharge, pressure at different locations including the runner blades, shafttorque, and the guide vane angular movements are performed. The maximum amplitudes of the unsteady pressure fluctuations in the turbine were observed under a runaway condition. The amplitudes were 2.1 and 2.6 times that of the pressure loading at the best efficiency point in the vaneless space and runner, respectively. Such high-amplitude, unsteady pressure pulsations can affectthe operating life of the turbine.

  • 108.
    Sundström, Joel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mulu, Berhanu
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Wall friction and velocity measurements in multiple frequencies pulsating flow2014Conference paper (Refereed)
    Abstract [en]

    Turbulent pulsating flow in a 100 mm diameter pipe has been studied experimentally at a Reynolds number of 14,500. The work covers four different flow conditions; steady, pulsating flow at oscillation frequencies 0.08 and 0.4 Hz, and pulsating flow with simultaneous imposition of both frequencies. The amplitudes of the pulsations were 10 and 7.5% of the bulk flow at 0.08 and 0.4 Hz, respectively. Laser Doppler anemometry, hot-film and pressure measurements show that the mean values of velocity, wall shear stress and pressure gradient are unaffected by the imposed pulsations. In agreement with previous studies of pulsating flow, the phase averaged pressure gradient leads both the velocity and wall shear stress when a single pulsation is imposed on the mean flow. These phase leads remain virtually unchanged when the two frequencies are imposed simultaneously. The amplitude responses of the velocity, wall shear stress and pressure gradient in the combined pulsating flow is shown to be superpositions of the amplitudes from the cases of separate pulsations. There are no signs of non-linear interactions between the harmonics.

  • 109.
    Jonsson, Pontus
    et al.
    Pöyry.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Development of the pressure-time method as a relative and absolute method for low-head hydraulic machines2013Conference paper (Refereed)
    Abstract [en]

    The pressure-time method is an absolute method common for flow measurements in power plants. The method determines the flow rate by measuring the pressure and estimating the losses between two sections in the penstock during a closure of the guide vanes. The method has limitations according to the IEC41 standard, which makes it difficult to use at Swedish plants where the head is generally low. This means that there is limited experience/knowledge in Sweden on this method, where the Winter-Kennedy is usually used. The present work presents pressure-time measurements (with L=5 m) performed on a 10 MW Kaplan turbine compared to transit-time flow measurements. A new formulation taking into account the unsteady losses allows a better estimation of the flow rate, up to 0.3%, in the performed experiments. As an alternative to the Winter-Kennedy widely used in Sweden, the pressure-time method was tested as a relative method by measuring the pressure between the free surface and a section in the penstock without knowing the exact geometry, i.e., pipe factor. Such measurements may be simple to perform as most of the inlet spiral casings have pressure taps. Furthermore, the viscous losses do not need to be accurately determined as long as they are handled similarly between the measurements. The pressure-time method may thus become an alternative to the Winter-Kennedy.

  • 110.
    Jonsson, Pontus
    et al.
    Pöyry.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Development of the pressure-time method as a relative and absolute method for low-head hydraulic machines2013Report (Other academic)
    Abstract [en]

    The pressure-time method is an absolute method common for flow measurements in power plants. The method determines the flow rate by measuring the pressure and estimating the losses between two sections in the penstock during a closure of the guide vanes. The method has limitations according to the IEC41 standard, which makes it difficult to use at Swedish plants where the head is generally low. This means that there is limited experience/knowledge in Sweden on this method, where the Winter-Kennedy is usually used. Since several years, Luleå University of Technology works actively in the development of the pressure-time method for low-head hydraulic machines with encouraging results. Focus has been in decreasing the distance between both measuring sections and evaluation of the viscous losses. Measurements were performed on a pipe test rig (D=0.3 m) in a laboratory under well controlled conditions with 7

  • 111.
    Dunca, Gerogiana
    et al.
    POLITEHNICA University of Bucharest.
    Bucur, Diana Maria
    POLITEHNICA University of Bucharest.
    Jonsson, Pontus
    Pöyry.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Discharge measurements using the Pressure-Time Method: Different evaluation procedures2013Conference paper (Refereed)
    Abstract [en]

    This paper analyzes the pressure-time method and its developments. The pressure-time method used to determine the discharge in hydraulic turbines is described and applied in a generic test case in well controlled laboratory conditions. Developments of the method are presented: a time dependent friction factor (proposed by Jonsson) and a different upper integration limit (proposed by Adamkowski). Laboratory experiments are used to compute the discharge using the pressure-time method in the standard and modified versions and the results are compared. The precision of the methods is verified by comparing the computed discharge values to the values measured with a magnetic flowmeter.

  • 112.
    Trivedi, Chiragkumar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gandhi, Bhupendra
    Indian Institute of Technology, Roorkee.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effect of transients on Francis turbine runner life: a review2013In: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 51, no 2, p. 121-132Article in journal (Refereed)
    Abstract [en]

    The present electricity market and the injection of power generated using intermittent energy sources have brought instability in the operation of the power grid. This has resulted in frequent load variations, emergency shut-down and restart, total load rejections, and off-design operation of grid connected hydraulic turbines. The present paper reviews the available literature summarizing the effects of transients on Francis turbine investigated experimentally, numerically, and analytically. Transients create both steady and unsteady pressure loading on the runner blade, resulting in cyclic stresses and fatigue development in the runner. These effects shorten the runner life, increase cost of plant operation, and loss of power generation. The reviewed literature has shown that one start–stop cycle can shorten predefined refurbishment time up to 15 hours. Turbine start–stop cannot be avoided, but runner life may be improved by minimizing the unfavourable pressure loading on the blades during transients through strategic movement of guide vanes.

  • 113.
    Sundström, Joel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Evaluation of the volumetric methods with application to low head hydraulic machines2013In: 16th International Flow Measurement Conference 2013: Flomeko 2013 ; Paris, France, September 24 - 26, Red Hook, NY: Curran Associates, Inc., 2013, p. 278-281Conference paper (Refereed)
    Abstract [en]

    The introduction of electricity certificates has increased the interest in development of flow measuring techniques to verify efficiency improvements after refurbishments in Swedish low head hydraulic machines. At Luleå Univeristy of Technology Jonsson [1] and Lövgren [2] have been working with development of the pressure-time method. The present work presents an evaluation of a flow measuring method known as the volumetric method. The method consists in running a turbine at a constant load during an extended period of time which depends upon the reservoir geometry. The flow rate through the turbine is determined from the volume change in the reservoir(s) by measuring the water level change. Through a pilot study in a full scale machine it is shown that the method reproduces reasonable results. The measured flow rate deviates by less than 3% from the value reported in the hydropower plant. The accuracy of the reported flow rate and the one measured in here is however difficult to determine and left unconsidered in this work. For future studies of the method it is recommended to more thoroughly investigate how accurately the rate of change of water level along with the reservoir area can be determined.

  • 114.
    Trivedi, Chiragkumar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Gandhi, B. K.
    Indian Institute of Technology, Roorkee.
    Dahlhaug, Ole G.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Experimental and numerical studies for a high head Francis turbine at several operating points2013In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 135, no 11Article in journal (Refereed)
    Abstract [en]

    Experimental and numerical studies on a high head model Francis turbine were carried out over the entire range of turbine operation. A complete Hill diagram was constructed and pressure-time measurements were performed at several operating conditions over the entire range of power generation by installing pressure sensors in the rotating and stationary domains of the turbine. Unsteady numerical simulations were performed at five operating conditions using two turbulent models, shear stress transport (SST) k-x and standard k-e and two advection schemes, high resolution and second order upwind. There was a very small difference (0.85%) between the experimental and numerical hydraulic efficiencies at the best efficiency point (BEP); the maximum difference (14%) between the experimental and numerical efficiencies was found at lower discharge turbine operation. Investigation of both the numerical and experimental pressure-time signals showed that the complex interaction between the rotor and stator caused an output torque oscillation over a particular power generation range. The pressure oscillations that developed due to guide vanes and runner blades interaction propagate up to the trailing edge of the blades. Fourier analysis of the signals revealed the presence of a vortex rope in the draft tube during turbine operation away from the BEP.

  • 115.
    Amiri, Kaveh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mulu, Berhanu
    Vattenfall Research & Development.
    Raisee, Mehrdad
    Mechanical Engineering Department, University of Tehran.
    Experimental study of fluid structure interaction in a Kaplan turbine runner blade2013Conference paper (Refereed)
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  • 116.
    Dunca, Georgiana
    et al.
    POLITEHNICA University of Bucharest.
    Bucur, Diana
    POLITEHNICA University of Bucharest.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Proulx, Gilles
    Hydro-Québec Research’s Institute.
    Dostie, Matheiu Bouchard
    Hydro-Québec Research’s Institute.
    Investigation of the pressure-time method with an unsteady friction2013In: Hydro 2013: International Conference and Exhebition : Promoting the Versalite Role of Hydro, 2013Conference paper (Refereed)
    Abstract [en]

    The pressure-time method is used to determine the flow rate in hydraulic turbines. Over the years, developments of the method to improve its accuracy have been proposed, such as a time dependent friction (Jonsson) or a different upper integration limit (Adamkowski). The present work investigates these developments on measurements performed on a full-scale machine for different flow rates. The discharge computed values using pressure measurements are compared to ultrasound transit time measurements performed simultaneously. The results point out the significance of the developments on the final results; variations of 0.5% are obtained when combining Jonsson friction formulation and Adamkowski upper integration limit.

  • 117. Simmons, Gregory F
    et al.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Glavatskih, Sergei
    Operational transients in the guide bearings of a 10 MW Kaplan turbine2013In: International journal on hydropower and dams, ISSN 1352-2523, Vol. 20, no 5, p. 94-100Article in journal (Refereed)
    Abstract [en]

    Experiments are conducted using a 10 MW Kaplan hydropower machine with a PowerFormerT M generator, the Porjus U9 research machine. This machine is outfitted with an extensive array of sensors to determine oil film thickness, pad tilting, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all three guide bearings are examined during both steady state and transient operation.

  • 118.
    Cervantes, Michel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Amiri, Kaveh
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Rotor-Stator interaction in Kaplan turbines during steady and transient operations2013Conference paper (Refereed)
  • 119.
    Lövgren, Magnus
    et al.
    Vattenfall Research & Development.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Some limitations of the Winter-Kennedy flow measuring method2013Conference paper (Refereed)
    Abstract [en]

    The Winter-Kennedy flow measuring method has been investigated on a test rig with a low head Kaplan model equipped with a semi-spiral casing. The effect of the runner and pressure taps positions on the method were the object of the investigation. The Winter-Kennedy constant was different for the old and new runner, inducing a difference as much as 2% on the estimation of the flow rate, when using the constant of the old runner. The results point also out different results function of the pressure taps position, indicating an optimal position specific for the present type of spiral casing. In summary, the Winter-Kennedy is inadequate to estimate the efficiency step-up of the following turbine after refurbishment with enough accuracy.

  • 120.
    Gonzalez, Sergio Galvan
    et al.
    Mechanical Engineering Department, Universidad Michoacana de San Nicolas de Hidalgo.
    Ibarra-Bracamontes, Laura
    Mechanical Engineering Department, Universidad Michoacana de San Nicolas de Hidalgo.
    Diaz, Gildardo Solorio
    Mechanical Engineering Department, Universidad Michoacana de San Nicolas de Hidalgo.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Assement study of the RNG turbulence model for steady state swirling flow analysis in a draft tube2012In: Avances en Simulacion Computacional y Modelado Numerico: memorias del XI congreso internacional de métodos numéricos en ingeniería y ciencias aplicadas CIMENICS'2012, Isla de Margarita, Venezuela, 26 al 28 de marzo de 2012 / [ed] E. Dávila; G. Uzcátegui; M. Cerrolaza, Facultad de Ingeniería , Universidad Central de Venezuela , 2012Conference paper (Refereed)
    Abstract [en]

    The flow in a hydraulic turbine draft tube is a challenging industrial application for CFD because is characterized by a turbulent flow with different flow phenomena, e.g. unsteadiness, flow separation, swirling flow and strong adverse pressure gradient. Thus, its simulation is complex and time-consuming high computational capacities are required Additionally, adequate turbulence modeling is needed to predict such flows accurately. The objective of the present work is to investigate the accuracy of the Renormalization Group Theory (RNG) k-c turbulence model on the draft tube flow close to the best efficiency of the turbine. The effect of the discerization schemes on these models has been studied As the flow is significantlyaffected by the walls, two different grid concentrations near to the wall (y + I and y + 50) were evaluated The numerical results are compared to detailed experimental results at different section and discussed.

  • 121.
    Westerlund, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Hermansson, Roger
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Computational fluid dynamics optimisation of a pellet burner2012In: Thermal Science, ISSN 0354-9836, E-ISSN 2334-7163, Vol. 16, no 4, p. 1275-1286Article in journal (Refereed)
    Abstract [en]

    Increased capacity of computers has made the computational fluid dynamics technology attractive for the design of different apparatuses. Optimisation of a pellet burner using the computational fluid dynamics was investigated in this paper. To make the design tool work fast, an approach with only mixing of gases was simulated. Other important phenomena such as chemical reactions were omitted in order to speed up the design process. The original design of the burner gave unsatisfactory performance. The optimised design achieved from simulation was validated and the results show a significant improvement. The power output increased and the emission of unburned species decreased but could be further reduced. The contact time between combustion gases and secondary air was probably too short. An increased contact time in high temperature conditions would possibly improve the design further.

  • 122. Jonsson, Pontus
    et al.
    Ramdal, J.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Development of the Gibson method – unsteady friction2012In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 23, no 1, p. 19-25Article in journal (Refereed)
    Abstract [en]

    The Gibson method is commonly used for discharge measurements at hydropower plants to estimate turbine efficiency. This paper presents a detailed numerical study of this method in order to estimate the physical quantities of importance in the method. Additionally, a modification of the Gibson method is proposed that adds temporal acceleration to the calculation procedure. The modification is numerically and experimentally validated for Reynolds numbers ranging from ≈0.6×106 to 1.7×106. Using both simulations and experimental data, it is shown that the modified method, the unsteady Gibson method, can reduce the flow estimation error by as much as 0.4% compared to the standard Gibson method. Depending on the conditions, the unsteady Gibson method corrects, or partly corrects, both under- and overestimations of the flow rate that are calculated when using the standard Gibson method.

  • 123.
    Neopane, Hari Prasad
    et al.
    Kathmandu University, Nepal.
    Dahlhaug, Ole Gunnar
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effect of sediment characteristics for predicting erosion on Francis turbines blades2012In: International journal on hydropower and dams, ISSN 1352-2523, Vol. 19, no 1, p. 79-83Article in journal (Refereed)
    Abstract [en]

    Sediment erosion not only reduces efficiency and life of hydropower turbines but also causes problems in operation and maintenance. Several factors are responsible for this erosion in hydro turbine components. Numerical simulations of a prototype Francis turbine are carried out to investigate the influence of sediment characteristics on erosion prediction. Results from prototype inspection allow a qualitative validation of the simulations. The numerical predictions of erosion are based on Lagrangian calculation of particle paths in a turbulent viscous flow. The relationships between sediment movement and erosion inside the turbine are investigated. It is found that the erosion process is strongly dependent on the particle size, shape, and concentration. Furthermore, the variation of relative erosion rate density is different for different guide vane openings. The results may be used for sediment erosion prediction and prevention.

  • 124.
    Amiri, Kaveh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Raisee, M.
    School of Mechanical Engineering, University of Tehran.
    Effects of flow unsteadiness on the wall shear stress2012In: 26th IAHR Symposium on Hydraulic Machinery and Systems: 19–23 August 2012, Beijing, China, IOP Publishing Ltd , 2012, p. 62033-Conference paper (Refereed)
    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.

  • 125.
    Nilsson, H.
    et al.
    Chalmers University of Technology.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effects of inlet boundary conditions, on the computed flow in the Turbine-99 draft tube, using OpenFOAM and CFX2012In: 26th IAHR Symposium on Hydraulic Machinery and Systems: 19–23 August 2012, Beijing, China, IOP Publishing Ltd , 2012, p. 32002-Conference paper (Refereed)
    Abstract [en]

    The flow in the Turbine-99 Kaplan draft tube was thoroughly investigated at three workshops (1999, 2001, 2005), which aimed at determining the state of the art of draft tube simulations. The flow is challenging due to the different flow phenomena appearing simultaneously such as unsteadiness, separation, swirl, turbulence, and a strong adverse pressure gradient. The geometry and the experimentally determined inlet boundary conditions were provided to the Turbine-99 workshop participants. At the final workshop, angular resolved inlet velocity boundary conditions were provided. The rotating non-axi-symmetry of the inlet flow due to the runner blades was thus included. The effect of the rotating angular resolution was however not fully investigated at that workshop. The first purpose of this work is to further investigate this effect. Several different inlet boundary conditions are applied – the angular resolved experimental data distributed at the Turbine-99 workshop, the angular resolved results of a runner simulation with interpolated values using different resolution in the tangential and radial directions, and an axi-symmetric variant of the same numerical data. The second purpose of this work is to compare the results from the OpenFOAM and CFX CFD codes, using as similar settings as possible. The present results suggest that the experimental angular inlet boundary conditions proposed to the workshop are not adequate to simulate accurately the flow in the T-99 draft tube. The reason for this is that the experimental phase-averaged data has some important differences compared to the previously measured time-averaged data. Using the interpolated data from the runner simulation as inlet boundary condition however gives good results as long as the resolution of that data is sufficient. It is shown that the difference between the results using the angular-resolved and the corresponding symmetric inlet data is very small, suggesting that the importance of the angular resolution is small. The results from OpenFOAM and CFX are very similar as long as the inlet data resolution is fine enough. CFX seems to be more sensitive to that resolution.

  • 126.
    Mulu, Berhanu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Jonsson, Pontus
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Experimental investigation of a Kaplan draft tube: Part I: best efficiency point2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 93, p. 695-706Article in journal (Refereed)
    Abstract [en]

    Hydropower, originally designed as a base electrical power, is now used to balance grid fluctuations that are primarily produced by market deregulation and the introduction of other renewable energy resources. New turbine designs must account for such constraints while also achieving high efficiency. Computational fluid dynamics, now an integrated tool in the hydraulic industry, requires accurate and detailed experimental data for validation purposes.The present work presents the investigation of a modern Kaplan turbine model combined with laser Doppler anemometry and flush-mounted pressure sensors, with a focus on the draft tube at the best turbine efficiency. Mean and phase-resolved quantities are presented for the velocity and pressure at several locations. The results demonstrate the strong influence of the swirl leaving the runner for a well-functioning draft tube as well as the negative impact of the draft tube cone. The blade-hub clearance is also found to have an impact on the flow beneath the runner cone.

  • 127. Jonsson, Pontus
    et al.
    Mulu, Berhanu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Experimental investigation of a Kaplan draft tube: Part II: Off-design conditions2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 94, no 2, p. 71-83Article in journal (Refereed)
    Abstract [en]

    Off-design conditions of hydropower turbines are becoming more frequent with the deregulation of electricity markets and the introduction of renewable energy resources. Originally, turbines were not built to operate under such conditions. It is evident that there is a need to develop turbines that can operate under off-design conditions while attaining high efficiency. This may be achieved with computational fluid dynamics (CFD). However, the complexity of Kaplan turbine flows is challenging to treat using CFD. Therefore, detailed experimental investigations are necessary to validate and develop CFD. This paper presents an investigation of a modern design Kaplan turbine model. The measurements were performed in the draft tube with laser Doppler anemometry and flush-mounted pressure sensors, with a focus on the part load and high load operation of the turbine. Mean and phase-averaged quantities are presented for the velocity and pressure along several sections. A contra-rotating flow region was observed under high load operation. Under part load operation, a rotating vortex rope (RVR) develops due to vortex breakdown. The presence of the RVR significantly reduces the draft tube performance.

  • 128.
    Cervantes, Michel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andrée, Gunilla
    Vattenfall.
    Klason, Peter
    Sundström, Joel
    Elforsk.
    Flow measurements in low-head hydro power plants2012Report (Other academic)
    Abstract [en]

    Hydropower stands for a large part of the energy production portfolio in Sweden and provides about 50% of the electricity needs. Most of the turbines were built some decades ago and are in a need of refurbishment. An important refurbishment period started some years ago and will be continuous. Substantial production gains and adaptation to new market demands may be achieved with such refurbishments. Refurbishments are also stimulated by the government through the electricity certificate system. Efficiency step-ups are thus of importance but challenging due to the presence of mainly low head (H<50 m) machines in Sweden. During the last decades, the Winter-Kennedy method has been used to verify improvements of the efficiency by measuring before and after a refurbishment. The results have for a number of cases shown unpredictable results. There is a need of development to measure accurately the efficiency in order to evaluate the outcome of different refurbishment projects. A workgroup within the Swedish Hydropower Centre (Svenskt Vattenkraftcentrum, SVC) has been formed together with representatives from the majority of the hydro turbine industry in Sweden to address the challenge of flow measurements in low head hydraulic turbines. The present report presents the different methods available with their actual development status and potential to meet low head hydraulic machines constraints. The working group suggests several actions for the development of flow measurements in low head machines. They are divided in 2 categories: long term and short term. The long term actions are typical SVC projects for PhD or/and senior researcher while short term actions are projects for consultant or/and senior researcher. The following actions are suggested in a hierarchical order:Long term projects1. Development of the pressure-time method as an absolute and relative method2. Evaluation of scale-up formula and influence of the parameters differing between model and prototype such spiral inlet boundary conditionsShort term projects1. Procedure/road book for implementation, evaluation and reporting of the Winter-Kennedy method. Continue working on the common guideline drafted in SEK-TK4.2. Systematic error analysis of the Winter-Kennedy method3. Testing of the volumetric method on a full-scale unit to investigate capabilities and evaluate necessary development for low head hydro power plants4. Testing of the tracer dilution method on a full-scale unit to investigate capabilities and evaluate necessary development for low head hydro power plants

  • 129.
    Jonsson, Pontus
    et al.
    Pöyry SwedPower AB.
    Ramdal, Jorgen
    Gauldal Consult AS.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nielsen, Torbjørn Kristian
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Implementing unsteady friction in pressure-time measurements2012Conference paper (Refereed)
    Abstract [en]

    Laboratory measurements using the pressure‐time method showed a velocity or Reynolds number dependent error of the flow estimate. It was suspected that the quasi steady friction formulation of the method was the cause. This was investigated, and it was proved that implementing a model for unsteady friction into the calculations improved the result. This paper presents the process of this investigation, and proposes a new method for treatment of the friction term in the pressure‐time method.

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  • 130.
    Muntean, S.
    et al.
    Center for Advanced Research in Engineering Science, Romanian Academy, Timişoara Branch.
    Ciocan, T.
    Hydraulic Machinery Department, Politehnica University of Timişoara.
    Susan-Resiga, R F
    Hydraulic Machinery Department, Politehnica University of Timişoara.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nilsson, H.
    Chalmers University of Technology.
    Mathematical, numerical and experimental analysis of the swirling flow at a Kaplan runner outlet2012In: 26th IAHR Symposium on Hydraulic Machinery and Systems: 19–23 August 2012, Beijing, China, IOP Publishing Ltd , 2012, p. 32001-Conference paper (Refereed)
    Abstract [en]

    The paper presents a novel mathematical model for a-priori computation of the swirling flow at Kaplan runners outlet. The model is an extension of the initial version developed by Susan-Resiga et al [1], to include the contributions of non-negligible radial velocity and of the variable rothalpy. Simple analytical expressions are derived for these additional data from three-dimensional numerical simulations of the Kaplan turbine. The final results, i.e. velocity components profiles, are validated against experimental data at two operating points, with the same Kaplan runner blades opening, but variable discharge

  • 131.
    Cervantes, Michel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    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 dimples2012In: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 6, no 12, p. 1599-1607Article in journal (Refereed)
    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.

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  • 132.
    Neopane, Hari Prasad
    et al.
    Kathmandu University, Nepal.
    Dahlhaug, Ole gunnar
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effect of operating conditions of Francis turbines for predicting sediment erosion2011In: HYDRO 2011 Proceedings: Prague, Czech Republic, 2011Conference paper (Refereed)
  • 133.
    Mulu, Berhanu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Vu, Thi
    Andritz.
    Devals, Christophe
    Andritz.
    Guibault, Francois
    Polytechnique Montréal.
    Effects of inlet boundary conditions on Kaplan draft tube simulation accuracy2011In: HYDRO 2011 Proceedings: Prague, Czech Republic, 2011Conference paper (Refereed)
  • 134.
    Seibert, Philipp
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Flow and losses in Kaplan draft tubes2011Conference paper (Refereed)
    Abstract [en]

    Low head machines of type Kaplan are composed of several elements to ensure a large efficiency. The flow enters a spiral casing and is distributed to an axial runner through stay and guide vanes. Downstream the runner, a draft tube is essential to ensure high efficiency by increasing the cross-section. Modern draft tubes are mainly composed of a conical diffuser followed by an elbow and a straight diffuser. The runner cone, attached to the runner, is included in the conical diffuser. By a gradual area increase it allows strong pressure recovery, so flow separation may occur. Furthermore, the runner cone rotates and thus counteracts the function of the draft tube. An ongoing work focuses on the flow around the runner cone by means of CFD and experiments with special interest on the boundary layer. The objectives are to quantify the effects of the runner cone on the draft tube large scale flow. Special attention will be given to runner cone angular velocity and swirl intensity. Preliminary, calculations on a Kaplan model test case at different operating points will give an overview over boundary layer thicknesses and separations points. Different meshes will be combined for the time dependent calculations, which include the runner and the draft tube.

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  • 135.
    Mulu, Berhanu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Phase resolved velocity measurements in a Kaplan draft tube model2011Conference paper (Refereed)
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  • 136.
    Mulu, Berhanu
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Phase-resolved velocity measurements in a Kaplan draft tube model2011In: 4-th International Meeting on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems,: October, 26-28, 2011, Belgrade, Serbia / [ed] M. Nedeljkovic.; M. Benisek; A. Gajic, Belgrade: IAHR , 2011Conference paper (Refereed)
  • 137.
    Seibert, Philipp
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Runner cone separation in Kaplan turbines2011In: 4-th International Meeting on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems,: October, 26-28, 2011, Belgrade, Serbia / [ed] A. Gajic; M. Benisek; M. Nedeljkovic., Belgrade: IAHR , 2011, p. 265-271Conference paper (Refereed)
    Abstract [en]

    Low head machines of the Kaplan type are composed of several components to ensure high efficiency. Downstream the runner, a draft tube ensures pressure recovery of the flow leaving the runner. Modern draft tubes are mainly composed of a conical diffuser followed by an elbow and a straight diffuser. The runner cone, attached to the runner, is included in the conical diffuser and thus counter-acts the function of the draft tube since adding angular momentum to the fluid. Variation of the runner cone angular velocity may increase draft tube pressure recovery by delaying eventual separation. While previous research focused only on the draft tube flow, this work presents calculations including runner and draft tube in order to point out possible joint effects. The initial calculations with ω*=1 are validated by comparison of mean and angular resolved axial and tangential velocity with LDA measurements. Two runner cone angular velocities are simulated: ω*=-1 (counter-rotating) and ω*=0 (stationary). A significant efficiency increase is obtained for a stationary runner cone.

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  • 138.
    Neopane, Hari Prasad
    et al.
    Kathmandu University, Nepal.
    Dahlhaug, Ole gunnar
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sediment erosion in hydraulic turbines2011In: Global Journal of Research Engineering, ISSN 0975-5861, Vol. 11, no 6Article in journal (Refereed)
    Abstract [en]

    Sediment erosion not only reduces efficiency and life of hydropower turbines but also causes problems in operation and maintenance. Several factors are responsible for this erosion in hydro turbine components. This paper presents the sediment erosion types in hydraulic turbines and their components based upon an extensive literature review and the field observation at Cahua hydropower plant, Peru. It includes some recommended methods to minimize the effect of sediment erosion in the turbine components. An alternative design of a Francis turbine in sediment-laden water is also briefly discussed.

  • 139.
    Cervantes, Michel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cupillard, Samuel
    Hydro-Québec Research’s Institute.
    Kokkolaras, Michael
    University of Michigan.
    Shape optimisation of a 3D slider with a dimple2011Conference paper (Refereed)
    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.

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  • 140.
    Cupillard, Samuel
    et al.
    Hydro-Québec Research’s Institute.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Glavatskih, Sergei
    Kungliga tekniska högskolan, KTH.
    Thermohydrodynamic analysis of a journal bearing with a microgroove on the shaft2011Conference paper (Refereed)
    Abstract [en]

    In this study, thermohydrodynamic performance of a journal bearing with a microgroove created on the shaft is analysed. A plain journal bearing is modelled using a computational fluid dynamics (CFD) software package. Navier-Stokes and energy equations are solved. The rotor-stator interaction is treated by using a computational grid deformation technique. Results are presented in terms of typical bearing parameters as well as flow patterns. Results are also compared to the bearing with a smooth shaft. The effect induced by a microgroove on pressure distribution is explained for different bearing configurations, eccentricities and microgroove depths. It is shown that the microgroove produces a local drop in pressure which, averaged over one revolution, decreases the load carrying capacity. The load carrying capacity is further decreased by using deeper microgrooves. With thermal effects considered, the microgroove carries more cold lubricant into the warmest regions of the bearing. This effect, more pronounced with deeper microgrooves, is due to a global flow recirculation inside the microgroove, which improve mixing

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  • 141.
    Jonsson, Pontus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Utveckling av Gibsons metod med transient friktion2011Conference paper (Refereed)
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  • 142.
    Cervantes, Michel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cupillard, Samuel
    Hydro-Québec Research’s Institute.
    3D thermodynamic analysis of a turbulent textured slider2010Conference paper (Refereed)
    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.

  • 143.
    Mill, O.
    et al.
    Svenska Kraftnät.
    Dahlbäck, N.
    Vattenfall.
    Worman, A
    Kungliga tekniska högskolan, KTH.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, F.
    Kungliga tekniska högskolan, KTH.
    Andreasson, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Yang, J.
    Kungliga tekniska högskolan, KTH.
    Lundin, U.
    UU.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Nilsson, H.
    CTH.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Glavatskih, Sergei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Analysis and development of hydro power research: synthesis within Swedish Hydro Power Centre2010Report (Other academic)
    Abstract [en]

    The market for hydropower re-investments in Sweden is approx 2.5 billion SEK/yr the coming decade. Large investments will also be carried out in Swedish tailing dams. This will result in challenging projects and need of experts. A crucial factor for a successful management of these challenges is the supply of engineers and researchers with hydro power and dam skills and knowledge. Swedish Hydro Power Centre (Svenskt vattenkraftcentrum, SVC) is a competence centre for university education and research environments within hydro power and mining dams. SVC comprises of two knowledge areas: Hydraulic Engineering and Hydro Turbines and Generators, respectively. SVC builds high-quality and long term sustainable knowledge at selected universities...

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  • 144.
    Petit, Olivier
    et al.
    Chalmers University of Technology.
    Mulu, Berhanu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nilsson, Håkan
    Chalmers University of Technology.
    Cervantes, Michel
    Comparison of numerical and experimental results of the flow in the U9 Kaplan turbine model2010In: 25th IAHR Symposium on Hydraulic Machinery and Systems: 20-24 September 2010 'Politehnica' University of Timişoara, Timişoara, Romania, London: IOP Publishing Ltd , 2010, p. 12024-Conference paper (Refereed)
    Abstract [en]

    The present work compares simulations made using the OpenFOAM CFD code with experimental measurements of the flow in the U9 Kaplan turbine model. Comparisons of the velocity profiles in the spiral casing and in the draft tube are presented. The U9 Kaplan turbine prototype located in Porjus and its model, located in Älvkarleby, Sweden, have curved inlet pipes that lead the flow to the spiral casing. Nowadays, this curved pipe and its effect on the flow in the turbine is not taken into account when numerical simulations are performed at design stage. To study the impact of the inlet pipe curvature on the flow in the turbine, and to get a better overview of the flow of the whole system, measurements were made on the 1:3.1 model of the U9 turbine. Previously published measurements were taken at the inlet of the spiral casing and just before the guide vanes, using the laser Doppler anemometry (LDA) technique. In the draft tube, a number of velocity profiles were measured using the LDA techniques. The present work extends the experimental investigation with a horizontal section at the inlet of the draft tube. The experimental results are used to specify the inlet boundary condition for the numerical simulations in the draft tube, and to validate the computational results in both the spiral casing and the draft tube. The numerical simulations were realized using the standard k-e model and a block-structured hexahedral wall function mesh.

  • 145.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effect of surface roughness on a counter rotating runner cone2010Conference paper (Refereed)
  • 146. Cupillard, Samuel
    et al.
    Glavatskih, Sergei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Inertia effects in textured hydrodynamic contacts2010In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 224, no 8, p. 751-756Article in journal (Refereed)
    Abstract [en]

    A flow analysis is carried out for a parallel textured slider to investigate the role of fluid inertia. Numerical simulations are performed for a laminar, two-dimensional, steady and isothermal flow. Stokes solutions are compared with Navier-Stokes solutions at the same Reynolds number. A range of texture depths is analysed. It is shown that there is an optimum value of texture depth that provides maximum load-carrying capacity. It is also shown that there is a critical depth value. Inertia has a negative effect on the load-carrying capacity for depths higher than the critical value, whereas it has a positive effect for lower depths. For a given texture depth, these effects are amplified as the Reynolds number increases. The global effect of inertia is positive when a realistic configuration of a parallel textured slider with a fore-region is considered.

  • 147. Gererkiden, Berhanu Mulu
    et al.
    Cervantes, Michel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    LDA measurements in a Kaplan spiral casing model2010In: 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery 2010 (ISROMAC-13): Honolulu, Hawaii, USA, 4 - 7 April 2010, Red Hook, NY: Curran Associates, Inc., 2010, p. 85-92Conference paper (Refereed)
    Abstract [en]

    This paper presents an experimental investigation of a Kaplan spiral casing turbine model. A two-component laser Doppler anemometry (LDA) apparatus was used to measure the velocity profiles at different locations in the turbine. To improve the signal quality and measurement accuracy, a refractive index matching optical box was mounted on the circular pipe of the spiral casing inlet. The investigations were carried out with a constant runner- blade angle and at three different loads: the best operating point of the turbine and two off-design operating points (left and right side of the propeller curve) with the presence of a vortex breakdown. The mean velocity profiles and corresponding RMS at the spiral casing before the guide vanes and at inlet of the spiral casing are presented for the different loads investigated.

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  • 148.
    Jonsson, Pontus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Cervantes, Michel
    Pressure measurements in the spiral casing of a Kaplan turbine model2010In: 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery 2010 (ISROMAC-13): Honolulu, Hawaii, USA, 4 - 7 April 2010, Red Hook, NY: Curran Associates, Inc., 2010, p. 79-84Conference paper (Refereed)
    Abstract [en]

    This paper presents an investigation of time-dependent pressure measurements in the spiral casing of a Kaplan turbine model. The work is part of a project with the purpose of investigating unsteady flow phenomena in hydro-power turbines. Three different loads were investigated: part load, best efficiency point, and high load. Several locations on the spiral casing were investigated. The results are compared with measurements in the draft tube cone. The mean values of the pressure around the spiral casing outlet indicates a nearly uniform distribution of the pressure to the runner. The runner frequency is one of the dominating frequencies. The corresponding amplitude is similar for all loads and decreases on the outer part of the spiral casing. At part load, a rotating vortex rope with precessional movement occurs in the draft tube. The rope generates an acoustic propagation upstream of the runner, which amplitude is ∼1/5 of the amplitude in the draft tube.

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  • 149.
    Jonsson, Pontus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ramdal, Jørgen
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Cervantes, Michel
    Dahlhaug, Ole Gunnar
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Nielsen, Torbjørn
    Norwegian University of Science and Technology (NTNU), Trondheim.
    The pressure-time measurements project at LTU and NTNU2010In: The 8th International Conference on Hydraulic Efficiency Measurement, 2010Conference paper (Other academic)
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  • 150.
    Cervantes, Michel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Andersson, Uban
    Vattenfall Research & Development.
    Lövgren, Magnus
    Vattenfall Research & Development.
    Turbine-99 unsteady simulations: validation2010In: 25th IAHR Symposium on Hydraulic Machinery and Systems: 20-24 September 2010 'Politehnica' University of Timişoara, Timişoara, Romania, London: IOP Publishing Ltd , 2010, p. 12014-Conference paper (Refereed)
    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

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