This study presents the conceptual design of a hydroelectric
power plant, as a part of a large scale rehabilitation project for an
existing power plant in Antalya, Turkey. The aim of the
rehabilitation project is to increase the power and efficiency of
the plant and its scope includes CFD aided turbine design, model
production and tests, the design, production and implementation
of the turbine, generator and the SCADA system. This study is
the first attempt, as a preliminary study, to handle the problem
and perform a conceptual design of the hydroelectric power
plant. The existing plant is modeled to estimate the head and flow
rate characteristics at various sections of the system. The net
head and flow rate of the turbine are estimated. Transient
analyses of the system are also performed to evaluate water
hammer characteristics. The results of the transient analyses
provide the inputs for the design of by-pass pipeline and pressure
relief valve. The estimated net head and flow rate from the
simulations are used as inputs for the preliminary design. The
dimensions of the spiral case, the diameter of the stay vanes and
guide vanes, wicket gate heights, runner diameter and rotational
speed, runaway characteristics and preliminary output power are
determined. The best efficiency point and the design point of the
turbine are also obtained as the net head versus the flow rate.
These results provide an idea on the feasibility of the increase in
power.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Aradag, S.

Celebioglu, K.

Cetinturk, H.

Karadeniz, C.

Ozkan, S.Y.

Sepetci, G.

Tascioglu, Y.

Yuksel, S.O.

Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.This study presents the conceptual design of a hydroelectric
power plant, as a part of a large scale rehabilitation project for an
existing power plant in Antalya, Turkey. The aim of the
rehabilitation project is to increase the power and efficiency of
the plant and its scope includes CFD aided turbine design, model
production and tests, the design, production and implementation
of the turbine, generator and the SCADA system. This study is
the first attempt, as a preliminary study, to handle the problem
and perform a conceptual design of the hydroelectric power
plant. The existing plant is modeled to estimate the head and flow
rate characteristics at various sections of the system. The net
head and flow rate of the turbine are estimated. Transient
analyses of the system are also performed to evaluate water
hammer characteristics. The results of the transient analyses
provide the inputs for the design of by-pass pipeline and pressure
relief valve. The estimated net head and flow rate from the
simulations are used as inputs for the preliminary design. The
dimensions of the spiral case, the diameter of the stay vanes and
guide vanes, wicket gate heights, runner diameter and rotational
speed, runaway characteristics and preliminary output power are
determined. The best efficiency point and the design point of the
turbine are also obtained as the net head versus the flow rate.
These results provide an idea on the feasibility of the increase in
power

UPSpace at the University of Pretoria

1  CONCEPTUAL DESIGN OF A HYDROELECTRIC POWER PLANT FOR A REHABILITATION PROJECT  Sepetci, G*., Cetinturk, H., Ozkan, S. Y.,Yuksel, S. O., Karadeniz, C., Celebioglu, K., Tascioglu, Y., Aradag, S. Department of Mechanical Engineering, TOBB University of Economics and Technology Sogutozu, Ankara, 06560, Turkey E-mail: gsepetci@etu.edu.tr   ABSTRACT  This study presents the conceptual design of a hydroelectric power plant, as a part of a large scale rehabilitation project for an existing power plant in Antalya, Turkey. The aim of the rehabilitation project is to increase the power and efficiency of the plant and its scope includes CFD aided turbine design, model production and tests, the design, production and implementation of the turbine, generator and the SCADA system. This study is the first attempt, as a preliminary study, to handle the problem and perform a conceptual design of the hydroelectric power plant. The existing plant is modeled to estimate the head and flow rate characteristics at various sections of the system. The net head and flow rate of the turbine are estimated. Transient analyses of the system are also performed to evaluate water hammer characteristics. The results of the transient analyses provide the inputs for the design of by-pass pipeline and pressure relief valve. The estimated net head and flow rate from the simulations are used as inputs for the preliminary design. The dimensions of the spiral case, the diameter of the stay vanes and guide vanes, wicket gate heights, runner diameter and rotational speed, runaway characteristics and preliminary output power are determined. The best efficiency point and the design point of the turbine are also obtained as the net head versus the flow rate. These results provide an idea on the feasibility of the increase in power.   INTRODUCTION  Hydroelectric power is one of the renewable energy sources for electricity generation. Hydroelectric power plants produce approximately 20% of the total electricity in the world [1]. Francis et al. developed the reaction turbine in 1848 [2]. Although the design methodology changed significantly, working principle of a Francis turbine is the same as in the past. Design of turbines was solely based on experimental research using scaled turbines or model tests in the past [3]. This design method was of course expensive and it was restricted. It mostly depended on the experience of the engineers and researchers [4]. In the last decades, the improvement of computational power led to use it for turbine design. The first application of Computational Fluid Dynamics (CFD) for turbine design was in two dimensions in 1970’s [5]. The development of numerical methods allowed the 3D Reynolds averaged Navier-Stokes (RANS) equations for hydraulic turbines to be solved [6]. Nowadays, the improvement of computational power and numerical methods let CFD results predict the turbine performance accurately. CFD methods are also used in rehabilitation projects because of high accuracy level of results [7].   Kepez-I Hydroelectric Power Plant that is located in Antalya, Turkey was set into operation in 1962. Water goes to Kepez from a water source through a conveyance channel. The water is carried to the power plant by the penstock that consists of two parts. The first part of the penstock is made of concrete and has a length of 650 m. The second part that has a length of 770 m and it is made of steel. A surge tank is located between the concrete and the steel penstock. Three vertical Francis type turbines are used to operate the power plant. Each turbine produces 8.8 MW power; therefore the power plant has a power capacity of 26.4 MW. A general view of the power plant and elevations of water source, surge tank, power plant and tail water are shown in Figure 1.   Figure 1.General view of the hydroelectric power plant Penstock is used to connect the power plant to the water source. The thickness and diameter of the penstock are determined according to the water pressure. The surge tank regulates the pressure fluctuations so it allows the penstock to remain in compact sizes and allows the turbine to work efficiently. The effect of these pressure fluctuations which constitute an unsteady hydraulic problem is called water hammer [8]. Water hammer can occur in different situations such as load acceptance, load rejection and instant load rejection conditions. The pressure drops in the penstock in load acceptance condition when the guide vanes open suddenly. On the other hand, pressure increases in the penstock in load rejection condition when the guide vanes close suddenly. Water hammer can cause major 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics592  damage to the turbines, valves or the penstock. The surge tank is sufficient to protect the penstock that is between the water source and itself. However the penstock that is between the surge tank and the power plant should also be protected; therefore a pressure relief valve (PRV) can be used in these conditions [8]. PRV is a valve that opens in a defined pressure. It opens when the pressure exceeds the limit value in the pipeline and high pressure values are avoided in the system.  This study presents the conceptual design of Kepez 1 HEPP as a part of a large scale rehabilitation project. The aim of the rehabilitation project is to increase the power and efficiency of the plant and its scope includes CFD aided turbine design, model production and tests, the design, production and implementation of the turbine, generator and the SCADA system. This study is the first attempt, as a preliminary study, to handle the problem and perform a conceptual design of the hydroelectric power plant that is going to be rehabilitated.  NOMENCLATURE  A C g H   [m2] - [m/s2] [m] Flow Area Hazen-Williams Roughness Coefficient Gravitational acceleration constant Head hL hm hT I k Km [m] [m] [m] [kgm2] - - Head loss Minor loss Turbine loss Moment of Inertia Hazen-Williams Eqn. Constant Minor loss coefficient n - Safety Factor P R S [Pa] [m] [m/m] Pressure Hydraulic radius Friction slope rin [m] Inlet radius of the pipe t Q V z [m] [m3/s] [m/s] [m] Thickness of the pipe Flow rate Velocity Elevation  Special characters ω [rpm] Rotational speed of the turbine runner σallow 𝛾 [Pa] [N/m3] Allowable yield strength Specific weight  Subscripts in  inlet    METHODOLOGY  The existing plant is modeled using WaterCAD software [9] to estimate the head and flow rate characteristics at various sections of the system. The water network is controlled by two fundamental physical laws, Conservation of Mass and Energy principle. This software solves for the distributions of flows and hydraulic grades using the Gradient Algorithm. This algorithm is used for analysis of pipe flows. The model includes the water source and tail water as reservoir, the penstock, surge tank, junctions and turbines. The dimensions and elevations of the components are defined according to the technical drawings of the actual plant. The model is simulated to obtain the major and minor losses of the pipes and junctions, pressure losses and head losses. These changes in head values, based on friction (major losses) and specific shape of the fitting (minor losses), obtained with the energy equation [9];  𝑃1𝛾+ 𝑧1 +𝑉122𝑔=𝑃2𝛾+ 𝑧2 +𝑉222𝑔+ ℎ𝑇 + ℎ𝐿                                  (1)  The major losses of the system is calculated as;  𝑄 = 𝑘 ∗ 𝐶 ∗ 𝐴 ∗ 𝑅0.63 ∗ 𝑆0.54                                                   (2)  The minor losses of the system is calculated as;  ℎ𝑚 = 𝐾𝑚 ∗𝑉22 ∗ 𝑔                                                                             (3)  Consequently, the net head and flow rate of the turbine are estimated. The dimensions of the components that are used in the model, are given in Table 1 and the details of the turbines are given in Table 2.  Table 1. Dimensions of the components Part  Diameter (mm) Material  Length (m) Concrete Penstock-1 2500 Concrete 340 Concrete Penstock-2 2500 Concrete 320 Penstock-1 2400 Steel 73.2 Penstock-2 2400 Steel 158 Penstock-3 2400 Steel 95.1 Penstock-4 2130 Steel 121 Penstock-5 2130 Steel 64.7 Penstock-6 2130 Steel 149 Penstock-7 2130 Steel 98 Penstock-8,9 1800 Steel 7.5 Branch 1,2,3 1100 Steel 9.12 Tailwater 1,2,3 1500 Concrete 5 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics603   Table 2. Details of the turbines  Turbine  Elevation (m) Efficiency (%) Rotational Speed - ω (rpm) Moment of Inertia - I (kgm2) Turbine 1, 2, 3 111.05 92 750 190.345  Several parts of the model of the power plant are given in Figure 2, Figure 3 and Figure 4. The full model is given in Annex A.   Figure 2. Water source and the concrete part of the penstock  Figure 3. Steel part of the penstock  Figure 4. Branches, turbines and the tail water The results of the steady-state analyses show the minor and major losses of the pipes and junctions, pressure losses and head losses. Therefore, the net head and flow rate of the turbine are estimated and these values determine the design point of the turbine.  The same model is also used in the transient analyses of the system to evaluate water hammer characteristics. The results of the transient analyses provide the inputs for the design of by-pass pipeline and pressure relief valve.   Water hammer can occur in load acceptance, load rejection or instant load rejection conditions. The higher pressure values occur in the load rejection condition among the other cases so the load rejection case is studied in this study. To illustrate, the guide vanes should be closed in a short time that could be called emergency shut-down time, without causing damage to the penstock and the pipeline in case of power cut-off. Different from the steady-state analyses, the wave speed is determined.   The maximum allowable pressure in the pipeline should be determined according to Hoop stress and longitudinal stress [10]. The Hoop stress for a cylindrical vessel is calculated as;  𝜎𝑎𝑙𝑙𝑜𝑤 =𝑃 ∗ 𝑟𝑖𝑛𝑡                                                                               (4)  The longitudinal stress for a cylindrical vessel is calculated as; 𝜎𝑎𝑙𝑙𝑜𝑤 =𝑃 ∗ 𝑟𝑖𝑛2𝑡                                                                               (5)  This pressure value is the limit of the pipeline that the resulting maximum pressure of the transient analysis should not exceed. The shut-down time of guide vanes is given randomly as a starting point and the pressure value is checked in order to determine whether the pipeline has enough strength. If the pipeline does not have enough strength, the time is increased and iterative process is repeated.   Preliminary design of the turbine components are based on the statistical data of the existing hydraulic turbines in the literature [11]. Maximum, minimum and gross head values, the flow rate, water temperature and system frequency are the inputs for the preliminary design. Different sizes of runner diameters are obtained due to their specific speed and rotational speed. The most convenient size of the turbine runner is chosen due to the settlement plan of the power plant and the dimensions of the other components such as the diameters of stay vanes and guide vanes, wicket gate height, spiral case size and draft tube size are determined. These dimensions are the starting point of the CFD aided design. The working range of the turbine is also determined for various flow rate values.   12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics614  RESULTS AND DISCUSSION  As a result of the steady-state analyses the major and minor losses of the pipes and junctions, pressure losses and head losses; therefore the net head and flow rates are estimated. The minor, head and pressure losses of components are given in Table 3. The total pressure loss is calculated as 85.3 kPa and total head loss is calculated as 7.88 m. The flow rate of the system is calculated as 18.03 m3/s. The turbine properties are given in the Table 4.  Table 3. The results of the steady-state analyses Part  Minor Loss (m) Head Loss (m) Pressure Loss (kPa) Concrete Penstock-1 0.34 1.28  12.5 Concrete Penstock-2 0 0.88 8.6 Penstock-1 0.02 0.27 2.6 Penstock-2 0 0.53 5.2 Penstock-3 0 0.32 3.1 Penstock-4 0.09 0.82 8 Penstock-5 0 0.39 3.8 Penstock-6 0 0.9 8.8 Penstock-7 0.78 1.37 13.4 Penstock-8 0.77 0.82 8 Penstock-9 0.27 0.34 3.3 Branch-1 0.63 0.81 8 Branch-2 0.51 0.69 6.7 Branch-3 0.2 0.38 3.7 Tailwater 1,2,3 0 0.03  0.3  Table 4. Turbine properties Turbine  Rotational Speed - ω (rpm) Head loss (m) Flow rate (m3/s) Turbine-1 750 160.1 6.03 Turbine-2 750 159.3 6.00 Turbine-3 750 159.2 6.00  Guide vane closing time is decided by the strength of the pipeline. The critical value is obtained on the branch pipe so the highest pressure occurs before the turbine. Hoop stress is calculated as 1.90 MPa and the longitudinal stress is calculated as 3.80 MPa. The yield strength of St50 steel is 295 MPa. Allowable yield strength is calculated as 147.5 MPa for a safety factor of 2. The inner radius of the branch is 543 mm and the thickness is 7 mm.  Allowable pressure equals to 1.90 MPa and guide vane closing time is calculated using this pressure. Firstly, the guide vanes are fully open for the first period that is for 10 seconds. The guide vanes start to close in the second period for 10-40 seconds. They are fully closed after 40 seconds. The time schedule of the guide vane closing is shown in Figure 5.   Figure 5.First scenario for guide vane closure As a result of this scenario, the maximum pressure occurs on the branch and equals to 2.007 MPa that exceeds the allowable pressure of the pipeline so a second scenario is developed. The guide vanes are open for 10 seconds in the first period. They start to close in the second period that is for 10 – 55 seconds. The second scenario is shown in Figure 6.   Figure 6. Second scenario for guide vane closure As a result of this scenario, the maximum pressure occurs on the branch and it is equal to 1.864 MPa that does not exceed the allowable pressure of the pipeline. The maximum pressure values of the pipeline is given in Table 5. Consequently, the guide vane closing time is calculated as 45 seconds so that water hammer does not damage the penstock and the pipeline.  0204060801001200 10 20 30 40Guide Vane Opening (%)Time (s)0204060801001200 10 20 30 40 50Guide Vane Opening (%)Time (s)12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics625  Table 5. The maximum pressure values on the branch pipe for the second scenario End Point Max Pres. (MPa) Branch 1 1.881 Branch 2 1.882 Branch 3 1.884  The results of the steady-state analysis are the inputs of the preliminary design. The head losses and pressure losses are calculated so the net head and flow rate are estimated with the help of steady-state analysis. The final specifications of the power plant are given in Table 6.  Table 6. Specifications of the power plant Rated discharge (m3/s) 6.1 Net head (m)  162 Site gross head (m) 170 Site elevation (m) 111.05 Water temperature 200 C Minimum net head (m) 155.05 Maximum net head (m) 167.75  CONCLUSION  It is decided based on the preliminary design that, the guide vanes, turbine runner and conical part of the draft tube have to be redesigned. The diameter of the new turbine runner must be the same as the old one because the spiral case and the stay vanes are under concrete and cannot be changed. Preliminary design results provide an idea on the feasibility of the increase in power. According to the results, new turbine runner can produce 8.9 MW of power with an efficiency of 93% These dimensions will also be the starting point of the CFD aided design that will be used to increase the efficiency of the power plant.  ACKNOWLEDGMENTS   This project is financially supported by Turkish Scientific and Research Council (TUBITAK) under grant 113G109. The facilities of TOBB ETU Hydro Energy Research Laboratory are used for the computations.   REFERENCES  [1] World Energy Council Turkish National Committee Energy Report, 2006. [2] Francis J. B., Lowell Hydraulic Experiments, 5th edition, Van Nostrand, Princeton, New Jersey, 1909. [3] Ardizzon G., Cavazzani G., and Pavesi G., A new generation of small hydro and pumped-hydro power plants: Advances and future challenges, Renewable Sustainable Energy Reviews,vol. 31, 2014, pp. 746-761. [4] Carija Z., Mrsa Z., and Fucak S., Validation of Francis water turbine CFD simulations, Strojarstvo, vol. 50,2008, pp. 5-14. [5] Roache P. J., Computational Fluid Dynamics,Hermosa Publishers, Albuquerque, 1972, New Mexico. [6] Keck H., and Sick M., Thirty years of numerical flow simulation in hydraulic turbomachines, Acta Mechanica, vol. 201, 2009, pp. 21-229. [7] Muntean S., - Numerical Analysis of the flow in the old Francis runner in order to define the refurbishment strategy, U.P.B. Scientific Bulletin, Series D,2010, pp.117-124. [8] Calamak M., and Bozkus Z., , Protective measures against waterhammer in run-of-river hydropower plants, 10th International Congress on Advances in Civil engineering, Ankara.,2012. [9] Bentley WaterCAD Getting Started Guide, 2010 [10] Hibbeler, R.C. Strength of Materials 8th Edition, Prentice Hall, New Jersey., 2008. [11] Siervo, F, Leva, F, Modern trends in selecting and designing Francis turbines, Water Power & Dam Construction 28(8),1976, pp. 28-35.  12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics636  ANNEX A MODEL OF THE POWER PLANT   12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics64

Conceptual design of a hydroelectric power plant for a rehabilitation project

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Conceptual design of a hydroelectric power plant for a rehabilitation project

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