PRESENTATION REPORT ON

Hydraulic Turbines

Submitted By:

Anand Kumar (ME/13/710)

Department of Mechanical Engineering

SHRI BALWANT INSTITUTE OF TECHNOLOGYApproved by AICTE, Min of HRD, Govt of India & DTE, Govt of HaryanaAffiliated to DCR University of Science and Technology, Murthal, Sonepat

Meerut Road (Pallri), Near DPS, Sonepat-131001, Haryana

PRESENTATION REPORT ON HYDRAULIC TURBINES

Abstract

My report focuses on the topic Hydraulic Turbines and its operations. In the following report

I have studied about the basics of Hydraulic Turbines, their operations and their uses. As well

as the report covers the inside view of the Hydraulic Turbines and its operations. Hydraulic

Turbines transfer the energy from a flowing fluid to a rotating shaft. A turbine is something

that rotates or spins. Hydraulic Turbines have a row of blades fitted to the rotating shaft or a

rotating plate. Flowing liquid, mostly water, when pass through the Hydraulic Turbine it strikes

the blades of turbine and makes the shaft rotate. While flowing through the Hydraulic Turbine

the velocity and pressure of the liquid reduce, these result in the development of torque and

rotation of the turbine shaft. There are different forms of Hydraulic Turbines in use depending

on the operational requirements. For every specific use a particular type of Hydraulic Turbine

provides the optimum output.

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PRESENTATION REPORT ON HYDRAULIC TURBINES

CERTIFICATE

This is certify that the seminar Topic entitled as Hydraulic Turbines and submitted by ANAND KUMAR having Roll No ME/13/710, embodies the bonafide work done by him under my supervision.

Signature of Supervisor:

Place:

Date:

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PRESENTATION REPORT ON HYDRAULIC TURBINES

TABLE OF CONTENTS

1. INTRODUCTION………….……………………………………...…...….……....5

2. HISTORY…………….……………………....…………………...………...….....7

3. THEORY OF OPERATION……………………………………………………..10

4. CLASSIFICATION OF TURBINE……………………………………………...11

4.1 PELTON TURBINE…………………………………………………............11

4.2 FRANCIS TURBINE……………………………………….………………..13

4.3 KAPLAN TURBINE……………………...…………………………………14

5. TYPES OF EFFICIENCY….……………….…………………………………...16

6. DRAFT TUBE…………………………..…………………………………….…17

7. CAVITATION IN TURBINE……………………………………………………18

8. REFERENCES……………………………………………………….……….….19

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PRESENTATION REPORT ON HYDRAULIC TURBINES

1. INTRODUCTION

A hydraulic turbine, also known as a hydro turbine or water turbine, is a turbine that converts

the energy from flowing water into mechanical energy by way of a rotating shaft connected

to a generator for the purpose of producing hydroelectricity in a dam. The use of modern

hydraulic turbines can be traced back to the use of waterwheels that used the weight effect of

water to produce energy for work. Today, modern hydraulic turbines are considered a form of

fluid dynamic machinery, featuring jets, nozzles, and vanes that operate on impulse or

reaction principles. The three most common types of hydraulic turbines that have been

developed are the Kaplan turbine, the Francis turbine and the Pelton turbine. The device

which converts hydraulic energy into mechanical energy or vice versa is known as Hydraulic

Machines. The hydraulic machines which convert hydraulic energy into mechanical energy

are known as Turbines and that convert mechanical energy into hydraulic energy is known as

Pumps.

It consists of the following:-

1. A Dam constructed across a river or a channel to store water. The reservoir is also known

as Headrace.

2. Pipes of large diameter called Penstocks which carry water under pressure from storage

reservoir to the turbines. These pipes are usually made of steel or reinforced concrete.

3. Turbines having different types of vanes or buckets or blades mounted on a wheel called

runner. 4. Tailrace which is a channel carrying water away from the turbine after the water

has worked on the turbines. The water surface in the tailrace is also referred to as tailrace.

Important Terms:

Gross Head (Hg): It is the vertical difference between headrace and tailrace.

Net Head (H): Net head or effective head is the actual head available at the inlet of the to

work on the turbine.

H = Hg – hf

Where hf is the total head loss during the transit of water from the headrace to tailrace

which is mainly head loss due to friction, and is given by

hf= 4fLV2 / 2gd

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Where f is the coefficient of friction of penstock depending on the type

of material of penstock,

L is the total length of penstock,

V is the mean flow velocity of water through the penstock,

D is the diameter of penstock and

g is the acceleration due to gravity.

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2. HISTORYEarly Hydraulic Turbine Development

The leap from the use of waterwheels to modern hydraulic turbines was a lengthy, extended

process that started during the Renaissance when engineers began to study the operational

characteristics of waterwheels with greater scrutiny. They soon realized that more power

could be harnessed if the waterwheel was actually enclosed in some type of a chamber or

encasement and that only a small amount of falling water actually struck the wheel paddle or

blade, leading to the loss of energy from the onrush of water not being captured. This

discovery did not immediately translate into a new type of hydraulic machine however. A

lack of hydraulic knowledge and the specialized tools needed to build such a machine

hampered such progress well until the late 18th century.

Both problems were somewhat resolved with

what is considered one of the earliest reaction turbines and the precursor to today’s modern

hydraulic water turbine invented by German mathematician and naturalist Johann Andres von

Segner in 1750. Segner’s archaic reaction turbine involved capturing flowing water on a

horizontal axis inside a cylindrical box that contained a shaft on a runner or rotor and then

flowed out through tangential openings, while the weight of the water acted upon the wheel’s

inclined vanes.

In 1828, Claude Bourdin, a French engineer, coined the term “turbine” from the Latin

derivative ‘turbo’ which means whirling or a vortex. The term reflected the primary

difference between waterwheels and the new turbines that would soon come into

development that featured a swirling motion of water by passing energy to a spinning rotor. A

turbine would prove to process more water, spin faster, and harness bigger heads. Another

distinguishing feature of early turbines from waterwheels was they were built on a vertical

axis opposite of a basic waterwheel’s horizontal axis connected to a vertical shaft

configuration. The blades also resembled spoons or shovels, therefore, early turbines were

sometimes called “spoon wheels.”

Around the same time, a student of Claude

Bourdin by the name of Benoit Fourneyron invented the first modern hydraulic turbine. His

first turbine was not very powerful at only six horsepower.

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Another drawback was that the radial outflow of water that passed through it created a

problem if the water flow was reduced or load removed. Eventually, he did master the

building of larger sized turbines that could withstand higher pressures and delivered

greater horsepower. For example, his most powerful water turbine achieved a speed of 2,300

revolutions per minute at 60 horsepower, translating into an efficiency of about 80 percent.

The Francis Turbine

In 1849, an American by the name of James Francis built a hydraulic reaction turbine that

was to be an improvement of other hydraulic turbines already operating at the time. Most of

these hydraulic turbines were produced with the water entering into the runners at the

machine’s center and then flowed radially outward. His design changed the shape of the

runner blades so they curved and the water flow turned from a radial to an axial path. The

Francis turbine became widely used in rivers or waterways where with water pressures or

heads equivalent to 33 to 328 feet (10 to 100 m).

The Pelton Turbine

In the mid 1800s, another American by the name of Lester Allen Pelton invented a hydraulic

turbine for use in water heads of 295 to 2,953 feet (90 to 900 m). [20] With the Pelton turbine

the water could be channeled from a high level reservoir through a long duct or penstock to a

nozzle.

The energy of the flowing water was then converted into kinetic energy through a high-speed

jet. The jet spray of water was concentrated directly onto curved buckets affixed around the

parameter of a wheel. These curved buckets turned the flow of water at 180 degrees and

extracted momentum. Since the action of the wheel was contingent on the impulse created by

the jet on the wheel rather than the reaction of expanding water, the Pelton turbine is

considered to be an example of an impulse turbine.

The Turgo Turbine

The Turgo turbine, also called a “Half Pelton” turbine was invented shortly after the Pelton

Wheel in 1920 by Eric Crewdson. With a Turgo turbine, the water entered on one side and

then was channeled through the runner blades at a 145-degree angle before exiting out the

other end.

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The Turgo turbine operated most effectively in water heads similar to a Pelton turbine and

also sometimes featured multiple jets. Another difference between the two was that a Turgo

turbine was smaller than a Pelton turbine and also proved cheaper to produce.

 The Kaplan Turbine

The growing demand for hydroelectric power in the 20th century spearheaded the

development for a turbine that could work in small water heads of 10 to 30 feet (3 to 9 m). In

1913, an Austrian engineer named Viktor Kaplan proposed a propeller type turbine. His

turbine, called the Kaplan turbine, operated very similar to a boat propeller but in reverse. He

also eventually changed the blade design to swivel on an axis.

Advancements in Hydraulic Turbines

The trend in the use of hydraulic turbines today has been toward higher water heads and

larger sized units. For example, Kaplan turbines are now typically used in heads of about 200

feet (60 m). Francis turbines are used in water heads of up to 2,000 feet (610 m) and the

Pelton turbine is used in water head installations of up to 5,800 feet (1,700 m).

The Francis turbine exists today as a

hydropower reaction turbine that contains a runner and has water passages and anywhere

from nine to 19 curved non-adjustable blades or vanes. When the water passes through the

runner, it strikes the curved blades causing them to rotate and the shaft, connected to

a generator, immediately transmits this into rotational movement.

Kaplan turbines have retained a design like a

marine propeller but may also contain gates to control the angle of fluid flow through the

blades. Recent developments have also sparked an increase in the number of application

Kaplan turbines are being used for.

Hydro sources once abandoned due to economic and environmental fallout are now applying

Kaplan turbines. Interestingly enough, Kaplan turbines have even been used as wind turbines.

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3. THEORY OF OPERATION

Flowing water is directed on to the blades of a turbine runner, creating a force on the blades.

Since the runner is spinning, the force acts through a distance (force acting through a distance

is the definition of work). In this way, energy is transferred from the water flow to the turbine

Water turbines are divided into two groups; reaction turbines and impulse turbines. The

precise shape of water turbine blades is a function of the supply pressure of water, and the

type of impeller selected.

Reaction turbines

Reaction turbines are acted on by water, which changes pressure as it moves through the

turbine and gives up its energy. They must be encased to contain the water pressure (or

suction), or they must be fully submerged in the water flow.

Newton's third law describes the transfer of energy for reaction turbines.

Most water turbines in use are reaction turbines and are used in low (<30 m or 100 ft) and

medium (30–300 m or 100–1,000 ft) head applications. In reaction turbine pressure drop

occurs in both fixed and moving blades. It is largely used in dam and large power plants.

Impulse turbines

Impulse turbines change the velocity of a water jet. The jet pushes on the turbine's curved

blades which changes the direction of the flow. The resulting change in momentum (impulse)

causes a force on the turbine blades. Since the turbine is spinning, the force acts through a

distance (work) and the diverted water flow is left with diminished energy. An impulse

turbine is one which the pressure of the fluid flowing over the rotor blades is constant and all

the work output is due to the change in kinetic energy of the fluid.

Prior to hitting the turbine blades, the water's pressure (potential energy) is converted

to kinetic energy by a nozzle and focused on the turbine. No pressure change occurs at the

turbine blades, and the turbine doesn't require a housing for operation.

Newton's second law describes the transfer of energy for impulse turbines.

Impulse turbines are often used in very high (>300m/1000 ft) head applications.

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4. CLASSIFICATION OF TURBINES

4.1 Pelton Turbine

The Pelton wheel is an impulse type water turbine. It was invented by Lester Allan Pelton in

the 1870s. The Pelton wheel extracts energy from the impulse of moving water, as opposed to

water's dead weight like the traditional overshot water wheel. Many variations of impulse

turbines existed prior to Pelton's design, but they were less efficient than Pelton's design.

Water leaving those wheels typically still had high speed, carrying away much of the

dynamic energy brought to the wheels. Pelton's paddle geometry was designed so that when

the rim ran at half the speed of the water jet, the water left the wheel with very little speed;

thus his design extracted almost all of the water's impulse energy which allowed for a very

efficient turbine.

The main components of a Pelton turbine are:

(i) Nozzle and flow regulating arrangement: - Water is brought to the hydroelectric plant site

through large penstocks at the end of which there will be a nozzle, which converts the

pressure energy completely into kinetic energy. This will convert the liquid flow into a high-

speed jet, which strikes the buckets or vanes mounted on the runner, which in-turn rotates the

runner of the turbine.

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The amount of water striking the vanes is controlled by the forward and backward motion of

the spear. As the water is flowing in the annular area between the annular area between the

nozzle opening and the spear, the flow gets reduced as the spear moves forward and vice-

versa.

(ii) Runner with buckets:- Runner is a circular disk mounted on a shaft on the periphery of

which a number of buckets are fixed equally spaced as shown in Fig. The buckets are made

of cast-iron cast-steel, bronze or stainless steel depending upon the head at the inlet of the

turbine. The water jet strikes the bucket on the splitter of the bucket and gets deflected

through () 160-1700.

(iii) Casing: It is made of cast-iron or fabricated steel plates. The main function of the casing

is to prevent splashing of water and to discharge the water into tailrace.

(iv) Breaking jet: Even after the amount of water striking the buckets is completely stopped,

the runner goes on rotating for a very long time due to inertia. To stop the runner in a short

time, a small nozzle is provided which directs the jet of water on the back of bucket with

which the rotation of the runner is reversed. This jet is called as breaking jet.

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The Francis turbine is a type of water turbine that was developed by James B.

Francis in Lowell, Massachusetts. It is an inward-flow reaction that combines radial and axial

flow concepts. Francis turbines are the most common water turbine in use today. They

operate in a water head from 40 to 600 m (130 to 2,000 ft) and are primarily used for

electrical power production. The generators which most often use this type of turbine have a

power output which generally ranges just a few kilowatts up to 800 MW, though mini-

hydro installations may be lower. Penstock (input pipes) diameters are between 3 and 33 feet

(0.91 and 10.06 meters). The speed range of the turbine is from 83 to 1000 rpm. Wicket gates

around the outside of the turbine's rotating runner control the rate of water flow through the

turbine for different power production rates. Francis turbines are almost always mounted with

the shaft vertical to keep water away from the attached generator and to facilitate installation

and maintenance access to it and the turbine.

A Francis turbine consists of the following main parts:

Spiral casing: The spiral casing around the runner of the turbine is known as the volute

casing or scroll case. All throughout its length, it has numerous openings at regular intervals

to allow the working fluid to impound on the blades of the runner. These openings convert

the pressure energy of the fluid into momentum energy just before the fluid impound on the

blades to maintain a constant flow rate despite the fact that numerous openings have been

provided for the fluid to gain entry to the blades, the cross-sectional area of this casing

decreases uniformly along the circumference.

Guide or stay vanes: The primary functions of the guide or stay vanes is to convert the

pressure energy of the fluid into the momentum energy. It also serves to direct the flow at

design angles to the runner blades.

Runner blades: Runner blades are the heart of any turbine as these are the centers where the

fluid strikes and the tangential force of the impact causes the shaft of the turbine to rotate and

hence electricity is produced. In this part one has to be very careful about the blade angles at

inlet and outlet as these are the major parameters affecting the power production.

Draft tube: The draft tube is a conduit which connects the runner exit to the tail race where

the water is being finally discharged from the turbine. The primary function of the draft tube

is to reduce the velocity of the discharged water to minimize the loss of kinetic energy at the

outlet.

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4.3 Kaplan Turbine

The Kaplan turbine is a propeller-type water turbine which has adjustable blades. It was

developed in 1913 by the Austrian professor Viktor Kaplan, who combined automatically

adjusted propeller blades with automatically adjusted wicket gates to achieve efficiency over

a wide range of flow and water level.

The Kaplan turbine was an evolution of the Francis turbine. Its invention allowed efficient

power production in low-head applications that was not possible with Francis turbines. The

head ranges from 10–70 meters and the output from 5 to 200 MW. Runner diameters are

between 2 and 11 meters. The range of the turbine rotation is from 79 to 429 rpm.

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The Kaplan turbine installation believed to generate the most power from its nominal head of

34.65m is as of 2013 the Tocoma Power Plant (Venezuela) Kaplan turbine generating

235MW with each of ten 4.8m diameter runners.

Kaplan turbines are now widely used throughout the world in high-flow, low-head power

production.

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5.TYPES OF EFFICIENCIES

Depending on the considerations of input and output, the efficiencies can be classified as

(i) Hydraulic Efficiency

(ii) Mechanical Efficiency

(iii) Overall efficiency

(i) Hydraulic Efficiency (h): It is the ratio of the power developed by the runner of a

turbine to the power supplied at the inlet of a turbine. Since the power supplied is hydraulic,

and the probable loss is between the striking jet and vane it is rightly called hydraulic

efficiency. If R.P. is the Runner Power and W.P. is the Water Power

h=R.P/W.P

(ii) Mechanical Efficiency (m): It is the ratio of the power available at the shaft to the

power developed by the runner of a turbine. This depends on the slips and other mechanical

problems that will create a loss of energy between the runner in the annular area between the

nozzle and spear, the amount of water reduces as the spear is pushed forward and vice-versa.

And shaft which is purely mechanical and hence mechanical efficiency. If S.P. is the Shaft

Power.

m= S.P/R.P

(iii) Overall Efficiency (): It is the ratio of the power available at the shaft to the power

supplied at the inlet of a turbine. As this covers overall problems of losses in energy, it is

known as overall efficiency. This depends on both the hydraulic losses and the slips and other

mechanical problems that will create a loss of energy between the jet power supplied and the

power generated at the shaft available for coupling of the generator.

= S.P/W.P

From Eqs (i), (ii), (iii), we have

= h * m

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6. DRAFT TUBE

In a Reaction turbine such as a Francis turbine or Kaplan turbine, a diffuser tube is installed

at the exit of the runner known as Draft Tube. In an Impulse turbine the available head is

considerably high and there is no significant effect on the efficiency if the turbine is placed a

couple of meters above the Tail Race. But in case of Reaction turbines, available head is low

and if turbine is installed above the tail race, there can be appreciable loss in available head.

By placing a diffusing pipe at the exit of the runner, both, overall efficiency and output of the

turbine can be improved. If the pressure path the exit of the turbine is lower than the pressure

of fluid in tail race it will cause a back flow of liquid into the turbine thus damaging it.

A draft tube at the end of the turbine increases the pressure of the exiting fluid at the expense

of its velocity. This means that the turbine can reduce pressure to a higher extent without fear

of back flow from tail race. The Draft tube gives an advantage of placing the turbine above

the tail race so that any required inspections can be made easily.

Types of Draft Tube:

1. Conical diffuser or straight divergent tube-This type of draft tube consists of a conical

diffuser with half angle generally less than equal to 10° to prevent flow separation. It is

usually employed for low specific speed, vertical shaft Francis turbine. Efficiency of this type

of draft tube is 90%

2. Simple elbow type draft Tube-It consists of an extended elbow type tube. Generally, used

when turbine has to be placed close to the tail-race. It helps to cut down the cost of

excavation and the exit diameter should be as large as possible to recover kinetic energy at

the outlet of runner. Efficiency of this kind of draft tube is less almost 60%

3. Elbow with varying cross section-It is similar to the Bent Draft tube except the bent part is

of varying cross section with rectangular outlet. The horizontal portion of draft tube is

generally inclined upwards to prevent entry of air from the exit end.

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7. CAVITATION IN TURBINECavitation is formation of vapor bubbles in the liquid flowing through any Hydraulic Turbine.

Cavitation occurs when the static pressure of the liquid falls below its vapor pressure.

Cavitation is most likely to occur near the fast moving blades of the turbines and in the exit

region of the turbines.

7.1 Causes of Cavitation

The liquid enters hydraulic turbines at high pressure; this pressure is a combination of static

and dynamic components. Dynamic pressure of the liquid is by the virtue of flow velocity

and the other component, static pressure, is the actual fluid pressure which the fluid applies

and which is acted upon it. Static pressure governs the process of vapor bubble formation or

boiling. Thus, Cavitation can occur near the fast moving blades of the turbine where local

dynamic head increases due to action of blades which causes static pressure to fall. Cavitation

also occurs at the exit of the turbine as the liquid has lost major part of its pressure heads and

any increase in dynamic head will lead to fall in static pressure causing Cavitation.

7.2 Detrimental Effects of Cavitation

The formation of vapor bubbles in cavitation is not a major problem in itself but the collapse

of these bubbles generates pressure waves, which can be of very high frequencies, causing

damage to the machinery. The bubbles collapsing near the machine surface are more

damaging and cause erosion on the surfaces called as cavitation erosion. The collapses of

smaller bubbles create higher frequency waves than larger bubbles. So, smaller bubbles are

more detrimental to the hydraulic machines.

Smaller bubbles may be more detrimental to the hydraulic machine body but they do not

cause any significant reduction in the efficiency of the machine. With further decrease in

static pressure more number of bubbles is formed and their size also increases. These bubbles

coalesce with each other to form larger bubbles and eventually pockets of vapor. This

disturbs the liquid flow and causes flow separation which reduces the machine performance

sharply. Cavitation is an important factor to be considered while designing Hydraulic

Turbines.

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7. REFERENCES

http://en.wikipedia.org/wiki/Water_turbine

http://en.wikipedia.org/wiki/Pelton_wheel

http://en.wikipedia.org/wiki/Francis_turbine

http://en.wikipedia.org/wiki/Kaplan_turbine

http://en.wikipedia.org/wiki/Draft_tube

http://www.brighthubengineering.com/fluid-mechanics-hydraulics

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