EXPERIMENTAL ANALYSIS ON FRANCIS TURBINE AT FULL LOAD TO DETERMINE THE PERFORMANCE CHARACTERISTICS CURVES

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 2, February 2018, pp , Article ID: IJMET_09_02_068 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EXPERIMENTAL ANALYSIS ON FRANCIS TURBINE AT FULL LOAD TO DETERMINE THE PERFORMANCE CHARACTERISTICS CURVES T. Teressa Assistant Professor, Department of Mechanical engineering, Koneru Lakshmaih Education Foundation, India G G Visal, P Sai Ram, M Srimani Kumar B. Tech Students Mechanical Engineering, Koneru Lakshmaih Education Foundation, India ABSTRACT Turbines are machines that convert Kinetic energy of fluids (e.g, water, steam, air, etc) into mechanical energy by causing a bladed rotor to rotate. The turbines are designed for a particular value of speed, head, efficiency, power or discharge. But operation of turbines under similar conditions do not yield a new concept. So, it is necessary to operate turbine under new conditions from these they have been designed. Here test is conducted on Francis turbine to know their dead-on behavior under varying conditions in Fluid Mechanics and Hydraulics Machines Laboratory. The results obtained were graphically plotted and the curves obtained are known as Constant head or Constant speed characteristics curve. The results obtained are the outcome of precise measurement and careful observation. This paper focuses mainly on the experimental analysis to get actual performance characteristics curves. The entire experimentation is carried out in the Fluid Mechanics and Hydraulics Laboratory. Head and gate opening are maintained constant. The speed is fluctuated by permitting a varying quantity of water to flow through the inlet openings. The Brake Horse Power is measured automatically by eddy dynamometer. After the completion of the experiment, a curve is plotted between unit discharge and unit speed for Francis turbine. The curves between unit discharge and unit speed are rising curves. The discharge increases with the increase in speed. Finally the overall efficiency of turbine was calculated along with percentage of full load. Key words: efficiency, Francis Turbine, head, speed, Power Cite this Article: T. Teressa, G G Visal, P Sai Ram, M Srimani Kumar, Experimental Analysis on Francis Turbine at Full Load to Determine the Performance Characteristics Curves, International Journal of Mechanical Engineering and Technology 9(2), 2018, pp editor@iaeme.com

2 T. Teressa, G G Visal, P Sai Ram, M Srimani Kumar 1. INTRODUCTION The Francis Turbine is a mixed flow reaction turbine used for medium heads with medium discharge. If water enters the runner and flows towards the centre of the wheel in the radial direction and leaves being parallel to the axis of the turbine, the turbine is known as mixed flow turbine (i.e. both radial and axial).the Francis turbine is a reaction turbine, which means that the working fluid changes pressure as it moves through the turbine, giving up energy. Basically, when the head at inlet of the turbine is the sum of pressure energy and kinetic energy and during the flow of water through runner a part of pressure energy is converted into kinetic energy, the turbine is a reaction turbine. The shaft of the Francis turbine can be either horizontal or vertical. The shaft is made of steel and of the is forged, it is provided with a collar for transmitting the axial thrust. Horizontal shafts are more compact for smaller sizes and allow easier access to the turbine.on the other hand, Vertical shaft occupy less space than horizontal shafts and permits greater inundate of the runner with a minimum excavation and the generators are easily accessible for maintenance. The vanes are fixed on the hub. The guide vanes are fixed between the two rings. This arrangement in the Francis turbine is in the form of wheel and called guide wheel. Each vane can be rotated about its centre. Th opening between the vanes can be increased or decreased by adjusting the guide wheel. The Guide wheel is adjusted by regulating shaft which is operated by governor. The guide mechanism provides the required quantity of water. Runner Blades, also called, roto, are the centers where the fluid strikes and the tangential force of the impact causes the shaft of the turbine to rotate producing torque. The flow in the runner is partly axial and party radial. The runners can be mainly classified as (i) Slow Runner, (ii) Medium Runner, and (iii) Fast Runner. The Runner blades need very precise finishing with high degree of accuracy. The runner is made up of Cast Iron foe small output and Cast Steel or Bronze for large output. The Francis turbine operates in a head range of ten meters to several hundred meters and are basically used for electrical power production. The number of blades in the turbine can vary from Seven to Nineteen. Figure 1 General view of Francis Turbine 2. DESCRIPTION OF EXPERIMENTAL SET-UP Francis Turbine consists of main components such as Runner(rotor), Volute casing (spirals scroll casing), guide vanes (stay vanes or stator), Venturi-meter draft tube and sump tank, arranged in a way that the whole unit works on recirculating water system. The water reaches editor@iaeme.com

Experimental Analysis on Francis Turbine at Full Load to Determine the Performance Characteristics Curves the guide blade through penstock.

3 Experimental Analysis on Francis Turbine at Full Load to Determine the Performance Characteristics Curves the guide blade through penstock. The guide blade acts as a medium and transports water to the runner blade. The water enters the runner with a low velocity but with a considerable amount of pressure. As the water flows over the vanes the pressure head is gradually converted into velocity head. This kinetic energy is utilized in rotating the wheel and thus the hydraulic energy is converted into Mechanical energy. The outgoing water enters the tail race after passing through the water enters the tail race after passing through the draft tube. The draft tube enlarges gradually which decreases the velocity but increases the pressure energy carried by the water. The enlarged end is submerged deeply in the tail race water. The water finally flow back to the sump tank through the venturimeter for the measurement of flow rate. The loading of the turbine is obtained by the electrical AC generator connected to the water tank. The stipulation for measurement of electrical energy by AC voltmeter and ammeter turbine speed by digital RPM indicator, head on the turbine by pressure gauge are in built to the control panel the whole experiment setup is shown in fig. 2. Figure 2 View of Experimental setup with control panel 2.1. Specifications of Francis Turbine 150 mm diameter, 4 blades, cast iron, volute casing: cast iron, Loading: Eddy current dynamometer with spring balance, Operating head: 20-50m, Kirloskar make:10 HP, Tank (SS):sump tank-880 ltrs capacity, Starter: Siemens make with MCB console switch and red indicator, Digital speed indicator: with proximity sensor for rpm measurement, Discharge measurement: Venturi-meter, Pressure gauge: 2 Nos., Vacuum gauge: 1 No mm hg, Controlling valves: 6 Butter fly Valves, Provision for supply: 1ph, 230 V,, 13 AMPS and all these are mounted on a frame. 3. EXPERIMENTATION METHODOLOGY The trials were conducted on Francis Turbine test set up to evaluate the performance and to obtain the constant head and constant speed characteristic curves at different load conditions. The guide vane angle position was selected. The gate was closed before starting the pump. The guide vane is kept for the required position by adjustable wheel. The gate was opened slowly so that turbine rotor picks up the speed and attains maximum at opening of the gate and set pressure on the gauge. For different electrical loads, rotor pitch position changed and maintains the constant head and speed editor@iaeme.com

4 T. Teressa, G G Visal, P Sai Ram, M Srimani Kumar 3.1. Observations The following observations noted down: Vane position, Speed N RPM, Delivery pressure P N/mm2, discharge Q LPS Calculation for Francis Turbine The following formulas are involved in calculating all the parameters: 1. Indicated Power (in KW) IP= H=Net Head in Meters d=density of water in kg/m3 Q=discharge of water in m3/sec 2. Shaft Power SHP= BP= Wattmeter reading t=transmission efficiency of generator=0.8u 3. Turbine Efficiency % turbine = 4. % full load = Max load Capacity=1.6kw 5. Specific Speed Ns= n= speed in rpm p= power at that instant H=total head at that point 6. Unit speed Nu= N= speed in rpm H= total head at that point 7. Unit Power Pu= P= power at that instant H= total head 8. Unit Discharge Qu= Q= discharge H= total head editor@iaeme.com

5 Experimental Analysis on Francis Turbine at Full Load to Determine the Performance Characteristics Curves 4. CHARACTERISTICS CURVES The curve is plotted between overall efficiency and Unit Speed and Overall efficiency with Percent of full load. The curves are shown in fig. 3 and fig. 4 Figure 3 unit speed (Nu) Vs unit power (Pu) Figure 4 Efficiency Vs Percent of full load 5. TABLES Table 1 Reading of Francis Turbine at Constant Speed editor@iaeme.com

6 T. Teressa, G G Visal, P Sai Ram, M Srimani Kumar Table 1 Reading of Francis Turbine at Constant Head 6. CONCLUSIONS Experimental analysis was carried out to determine the main characteristics curve at part load conditions. It was done for both constant pressure and constant speed. High efficiency cannot be obtained when a low discharge is flowing through the runner. This is because the runner blades in Francis Turbine are fixed and integral with hub. The loading of the turbine is obtained by the Eddy Current Dynamometer. For different electrical loads, rotor pitch position is changed, and constant head and constant pressure are maintained. The following observations were made from control panels: Voltmeter reading, Ammeter reading, Speed, Delivery pressure, The venturi-meter readings and different vane positions calculations were made and also the various performance characteristics curves plotted. REFERENCES [1] R.K. Rajput, Fluid Mechanics and Hydraulic Machines, Laxmi Publications (P) Ltd. New Delhi (India). [2] R. K. Bansal, Fluid Mechanics and Hydraulic Machines, Laxmi Publications (P) Ltd. New Delhi (India). [3] D. S. Kumar, Fluid Mechanics and Hydraulic Machines, Laxmi Publications (P) Ltd. New Delhi (India). [4] Yunus A. Cengel and John M. Cimbala, Fluid Mechanics Fundamentals and Applications McGraw Hill. [5] D. S. Kumar, Fluid Mechanics & Fluid Power Engineering S.K. Kataria Publications. [6] C.P. Kothandaraman & R. Rudramoorthy Basic Fluid Mechanics New Age Publications editor@iaeme.com

7 Experimental Analysis on Francis Turbine at Full Load to Determine the Performance Characteristics Curves [7] J.F. Douglas, J.M. Gasiorek & J.A. Swaffieid, Fluid Mechanics, ELBS Publications. [8] A. K. Mohanty, Fluid Mechanics Prentice Hall Publications. [9] A. K. Jain, Fluid Mechanics, Khanna Publications.) [10] Harikrishnan R, Resolution For Parameteric Discrepancies In The Flow of Francis Turbine. International Journal of Mechanical Engineering and Technology, 7(6), 2016, pp [11] Giridhara Babu Y, Ashok Babu T.P, Anbalagan M. and Meena R, Experimental and Numerical Investigation of Adiabatic Film Cooling Effectiveness Over The Compound Angled Gas Turbine Blade Leading Edge Model. International Journal of Mechanical Engineering and Technology, 5(9), 2014, pp

Experiment No.2 STUDY & TRIAL ON A FRANCIS TURBINE & PLOTTING OF MAIN /OPERATING CHARACTERISTICS.

Experiment No.2 STUDY & TRIAL ON A FRANCIS TURBINE & PLOTTING OF MAIN /OPERATING CHARACTERISTICS. Name of the student: Roll No: Date of Performance : Date of Submission Marks Scored: Signature of Staff