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International Journal of Mechanical Engineering and Technology (IJMET)

Volume 9, Issue 2, February 2018, pp. 663–669, Article ID: IJMET_09_02_068

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=2

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© 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. 663–669.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=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

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. 0-760mm 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.



3.1. Observations

The following observations noted down: Vane position, Speed „N‟ RPM, Delivery pressure

„P‟ N/mm2, discharge „Q‟ LPS.

3.2. Calculation for Francis Turbine

The following formulas are involved in calculating all the parameters:

1. Indicated Power (in KW)

IP=

Where, H=Net Head in Meters

d=density of water in kg/m3

Q=discharge of water in m3/sec

2. Shaft Power

SHP=

Where, BP= Wattmeter reading

t=Transmission efficiency of generator=0.8u

3. Turbine Efficiency

% turbine=

4. % full load =

Where, Max load Capacity=1.6kw

5. Specific Speed

Ns=

Where,

n= speed in rpm

p= power at that instant

H=total head at that point

6. Unit speed

Nu=

Where,

N= speed in rpm

H= total head at that point

7. Unit Power

Pu=

Where,

P= power at that instant

H= total head

8. Unit Discharge

Qu=

Where,

Q= discharge

H= total head




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



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.




[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.

31–40.

[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. 91–100.

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