hydraulic machines-turbines - copy

8/12/2019 Hydraulic Machines-Turbines - Copy

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Hydraulic MachinesTurbinesFLUID MECHANICS-II

Himani Jain 66) Damera Avinash 67)Kamlesh Gupta 68) Anjali Shrivastava 69)Sumit Bhadoriya 70) Gaurav Ladoia 71)Saket Rusia 72) Susheel Chimnani 73)Amit Sharma 74) Aditya Kusray 75)Sashidhar Vadlamani 76) Atish Sharma 77)Shupriya Singh 78) Mandeep Arya 79)Nemani Venkata Deepak 80)


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Elements of hydroelectric power plants


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Production of electricity with the help of aturbine


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In general a water turbine consists of a wheel calledrunner (or rotor)having a number of speciallydesigned vanesor bladesor buckets.

The water possessing a large amount of hydraulicenergy when strikes the runner, it does work on therunner and causes it to rotate.

The mechanical energy so developed is supplied to thegenerator coupled to the runner , which then generateselectrical energy.


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I n t r o d u c t i o n


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Heads and efficiencies of a Turbine

Heads: Gross head- Diff between head race leveland the

tail race level when no water is flowing . Itis also known as static head or total head and is

represented as HgNet or Effective Head-It is the head available at the

entrance of the turbine. It is obtained bysubtracting from the gross head all the

losses of the water that may occur aswater flows from the head race to theentrance of the turbine.

Hnet= Hg hf (where hf is losses due to friction or majorlosses)


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Heads Hydroelectric power plants are usually classified

according to the heads under which they work as:

Hydroelectric Plant

High Head Plant Medium HeadPlant

Low HeadPlant

Heads greaterthan 250m

Headsbetween 60mto 250m

Heads less than 60 m


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1. Hydraulic Efficiency( nh)

But delQ is negligibly small , so the equation becomes:

nh= {Power developed by the runner/wQH}

The unit of power is expressed in Kilowattin SI unitsamd metric horse powerin metric units.

The power supplied at the turbine entrance is termedas Water Horse Power (W.H.P).


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2. Mechanical Efficiency(nm)

It is defined as the ratio of the power available to theturbine shaft to the power developed by the runner.

These two differ in their amount by the mechanicallosses(Bearing friction).

Formulae:nm={Power available at the turbine shaft/power

developed by the runner} The power available at the turbine shaft is known as

Shaft Horse Power , S.H.P or Brake Horse Power ,B.H.P.


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3. Volumetric Efficiency

The volumetric efficiency is the ratio of the quantity ofwater actually striking the runner and the quantity ofwater supplied to the turbine.

The two quantities differ by the amount of water thatslips directly to the tail race without striking therunner.

nv = {Q/(Q+delQ)}


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4. Overall Efficiency

The overall efficiency of the turbine is the ratio of thepower available at the turbine shaft to the powersupplied by the water at the entrance to the turbine.

no = Power available at the turbine shaft/Net Powersupplied at the turbine entrance.

no= P .[w(Q+delQ)H]

Overall Efficiency= Hydraulic efficiency + Mechanicalefficiency + Volumetric efficiency.


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Classifications of Turbines The Hydraulic turbines are classified as follows:

1. According to the type of energy at the inlet:(a) Impulse turbine (b) Reaction Turbine

2.According to the direction of flow through the runner:

(a) Tangential flow turbine (b) Radial f low turbine(c) Axial flow turbine (d) Mixed flow turbine

3. According to the head at the inlet of turbine:(a) High head turbine (b) Medium head turbine(c) Low head turbine

4.According to the speed of the turbine:(a) Low specific speed turbine (b) medium specificspeed

turbine(c) High specific speed turbine


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1. According to the type of energy at the inlet:

Impulse Turbine: In this type of turbine all theavailable energy of water is converted into kineticenergy by passing it through a contracting nozzleprovided at the end of the penstock. Example Peltonwheel.

Reaction Turbine:In this type of turbine only a part ofthe total available energy is converted into kineticenergy and the rest remains in the form of pressureenergy. Example Francis Turbine.


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2.According to the direction of flow through the runner: Tangential f low:In this the water flows along the tangent to the

path of the rotation of the runner. Example Pelton wheel. Radial flow:In this the water flows along the radial direction and

remains wholly and mainly in the plane normal to the axis ofrotation, as it passes through the runner. Example- old francisturbine.

Axial flow:In this the flow of water is wholly and mainly alongthe direction parallel to the axis of the rotation of the runner.Example Kaplan turbine.

Mixed flow:In this water enters the runner at the outer peripheryin the radial direction and leaves it at the centre in the directionparallel to the axis of the rotation of the runner. Example-Modern Francis turbine.


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4.According to the specific speed of the turbine:

Low specific speed turbine:In these turbines thespecific speed varies from 8.5 to 30 for pelton wheelwith single jet and 43to 50 for pelton wheel with

double jet.

Medium specific speed turbine:In these turbines thespecific speed varies from 50 to 340----Francis turbine.

High specific speed turbine:In these turbines thespecific speed varies from 255 to 860 ---- Kaplan andother propeller turbines.


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TURGO WATER TURBINE

Similar in operation to the

pelton wheel only with half

cups arranged around the

runner

Water from the jets can

enter and exit from the cups,more easily and in greater

quantities giving this turbine

an efficiency of 90%


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BANKI TURBINE (MICHELL CROSSFLOW OR

OSSBERGER TURBINE) Numerous trough-shapedblades arranged radially

lengthwise around a

cylindrical runner

The crossflow turbine has

two independent nozzles

which are set at an angle of

45 projecting the water at

the optimum angle to the

blade


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Jonval Turbine

It is an axial or parallel-flow turbine, the waterpassing through themotor in directions

parallel with the centralshaft

A new feature providedby Henschel was thesuction pipe in theoutlet.


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FRANCIS SPIRAL TURBINE This turbine was the first with aninlet spiral. The water admission canbe regulated only with the slide valveat the inlet of the spiral because theguide blades of the turbine areimmovable. Today they are usually

made from concrete to withstand thehigh pressure.

Head: 17.4 mSpeed: 263 min-1

Water flow: 0.21 ms-1


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FOURNEYRON TURBINE It is a simple design as the

blades are bent only in one

plane unlike most modern

turbines which twist their

blades

It is easy to size the

Fourneyron Turbine to the

exact needs of the individual

site where it is to be

employed.


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PROPELLER AND KAPLAN TURBINES


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elton TurbineAlso called afree-jet turbineor Peltonwheel

Named after L. A. Pelton who invented it in 1880

Suited for high head,

low flow sites. The

largest units can be up

to 200MW. Can

operate with heads as

small as 15 meters and

as high as 1,800meters.


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In a Typical Pelton Turbine, the water from the reservoir flows

through the penstock at the outlet of which a nozzle is fitted. The nozzle

increases the kinetic energy of the water. At the outlet of the nozzle the

water strikes spoon-shaped buckets or cups arranged on the periphery

of a runner, or wheel, which causes the runner to rotate, producing

mechanical energy. The runner is fixed on a shaft, and the rotational

motion of the turbine is transmitted by the shaft to a generator.


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Main parts of Pelton turbine

1.Nozzle and flow regulating arrangement

2.Runner with buckets

3.Casing

4.Breaking jet


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1.Nozzle and flow regulating arrangement

The amount of water striking the buckets (vanes) of the runner

is controlled by providing a spear in the nozzle. The spear is a conical needle

which is operated either by a hand wheel or automatically in an axial direction

depending upon the size of unit.


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2.Runner with buckets

It consists of a circular disc on the periphery of which

number of buckets evenly spaced are fixed. The shape of the buckets is of adouble hemispherical cup or bowl. Each bucket is divided into two

symmetrical parts by a dividing wall which is known as splitter.


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3.Casing The function of the casing is to prevent the splashing of

water and to discharge water to tail race. It also acts as safe guards againstaccidents. It is made of cast iron or fabricated steel plates. The casing of the

pelton wheel does not perform any hydraulic function.

4.Breaking jet When the nozzle is completely closed by moving the

spear in the forward direction, the amount of water striking the runner reduces

to zero. But the runner due to inertia goes on revolving for a long time. To stop

the runner in a short time, a small nozzle is provided which directs the jet of

water on the back of vanes. This jet of water is called breaking jet.


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Video Showing The Details Of a Pelton Turbine


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Velocity diagram of Pelton Turbine


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Work done per unit wt of water striking per sec

=

Hydraulic Efficiency of Pelton Turbine

=


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DESIGN OF PELTON WHEELDesign of Pelton wheel means the following data is to

be determined:

1. Diameter of the jet (d),2. Diameter of wheel (D),

3. Width of the buckets which is =5*d,

4. Depth of the buckets which is =1.2*d,

5. Number of buckets on the wheel.

Size of the buckets mean the width and depth of thebuckets.


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DESIGN OF PELTON TURBINE RUNNERA Pelton turbine runner is designed to develop a known power P, when running at

a known speed N r.p.m. under a known head H. The various steps involved inthe design are :

1.Determine the required discharge QP = n ( WH ) = n ( wQH )

2.Calculate velocity V of the jet.3.Calculate total area of the jets by a = ( Q/V)4.Calculate pitch circle diameter D.5.Obtain the number of jets required by dividing total area of jets by area of each

jet.6.The fractional number of jets is rounded upto the appropriate integral number

and the corresponding diameter of each jet is calculated.7.Calculate the number of buckets to be provided and the bucket dimensions.


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DESIGN RULESSpecific speed The specific speed nsof a turbine dictates the turbine's

shape in a way that is not related to its size. This allows a

new turbine design to be scaled from an existing design ofknown performance. The specific speed is also the maincriterion for matching a specific hydro-electric site with thecorrect turbine type.

The formula suggests that the Pelton turbine is most

suitable for applications with relatively high hydraulichead, due to the 5/4 exponent being greater than unity, andgiven the characteristically low specific speed of the Pelton.


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TURBINE PHYSICS Energy and initial jet velocity In the ideal (frictionless) case, all of the hydraulic

potential energy(P.E= mgh) is converted into

kinetic energy(K.E = mv2/2). Equating these twoequations and solving for the initial jet velocity(Vi) indicates that the theoretical (maximum) jet

velocity is Vi= (2gh) . For simplicity, assume thatall of the velocity vectors are parallel to each other.

Defining the velocity of the wheel runner as: (u),then as the jet approaches the runner, the initial

jet velocity relative to the runner is: (Viu).
http://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Friction


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Optimal wheel speed

We know that the ideal runner speed will cause all ofthe kinetic energy in the jet to be transferred to thewheel. In this case the final jet velocity must be zero. Ifwe let Vi+ 2u= 0, then the optimal runner speed willbe u= Vi/2, or half the initial jet velocity.


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Power The power P= Fu= T, where is the angular

velocity of the wheel. Substituting for F, we haveP= 2Q(Vi u)u. To find the runner speed atmaximum power, take the derivative of Pwith

respect to uand set it equal to zero, [dP/du=2Q(Vi 2u)]. Maximum power occurs when u=Vi/2. Pmax =QVi2/2. Substituting the initial jetpower Vi= (2gh), this simplifies to Pmax =ghQ.This quantity exactly equals the kinetic power of

the jet, so in this ideal case, the efficiency is 100%,since all the energy in the jet is converted to shaftoutput


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TYPES OF TURBINE The Turbine is a Prime Mover in which a Rotary Motion isobtained by Centrifugal Force brought into action

by changing the Direction of Jet of a Fluid escaping from a

Nozzle at High Velocity. This Turbines are classified by several ways.The most

important and common division being with respect to theaction of the Steam and they are as,

01)Impulse Turbine

02)Reaction Turbine

03)Combination of Impulse and Reaction Turbine
http://hubpages.com/hub/What-is-the-difference-between-Impulse-and-Reaction-Turbinehttp://hubpages.com/hub/What-is-the-difference-between-Impulse-and-Reaction-Turbine


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IMPULSE TURBINE Impulse turbines change thevelocityof a water jet. The jet pushes on the

turbine's curved blades which changes the direction of the flow. The resultingchange in momentum (impulse) causes a force on the turbine blades. Sincethe turbine is spinning, the force acts through a distance (work) and thediverted water flow is left with diminished energy.

Prior to hitting the turbine blades, the water's pressure (potential energy) isconverted to kinetic energyby a nozzleand focused on the turbine. Nopressure change occurs at the turbine blades, and the turbine doesn't require

a housing for operation. Impulse turbines are most often used in very high (>300m/984 ft) head

applications
http://en.wikipedia.org/wiki/Velocityhttp://en.wikipedia.org/wiki/Impulse_(physics)http://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Nozzlehttp://en.wikipedia.org/wiki/Nozzlehttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Impulse_(physics)http://en.wikipedia.org/wiki/Velocity


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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 actingthrough a distance is the definition ofwork). In this way,energy is transferred from the water flow to the turbine

Water turbines are divided into two groups; reactionturbines and impulseturbines.

The precise shape of water turbine blades is a function ofthe supply pressure of water, and the type of impellerselected.
http://en.wikipedia.org/wiki/Mechanical_workhttp://en.wikipedia.org/wiki/Reaction_(physics)http://en.wikipedia.org/wiki/Impulse_(physics)http://en.wikipedia.org/wiki/Impulse_(physics)http://en.wikipedia.org/wiki/Reaction_(physics)http://en.wikipedia.org/wiki/Mechanical_work


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REACTION TURBINE 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 waterpressure (or suction), or they must be fully submerged inthe water flow.

Newton's third lawdescribes the transfer of energy forreaction turbines.

Most water turbines in use are reaction turbines and areused in low (


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REACTION TURBINE


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RADIAL FLOW TURBINE


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RADIAL FLOW TURBINE


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STEAM TURBINE
http://en.wikipedia.org/wiki/File:Dampfturbine_Laeufer01.jpghttp://en.wikipedia.org/wiki/File:Dampfturbine_Laeufer01.jpg


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STEAM TURBINE A steam turbineis a mechanical device that extracts thermal energyfrom pressurized steam, and converts it into rotarymotion. Its modernmanifestation was invented by Sir Charles Parsonsin 1884.[1]

It has almost completely replaced the reciprocatingpiston steamengineprimarily because of its greater thermal efficiency and higherpower-to-weight ratio. Because the turbine generates rotary motion, itis particularly suited to be used to drive an electrical generator about80% of all electricity generation in the world is by use of steamturbines. The steam turbine is a form of heat enginethat derives muchof its improvement in thermodynamic efficiencythrough the use ofmultiple stages in theexpansion of the steam, which results in a closer

approach to the ideal reversible process.
http://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Thermal_energyhttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Charles_Algernon_Parsonshttp://en.wikipedia.org/wiki/Charles_Algernon_Parsonshttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Reciprocating_enginehttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Rotational_motionhttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Rotational_motionhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Reversible_process_(thermodynamics)http://en.wikipedia.org/wiki/Reversible_process_(thermodynamics)http://en.wikipedia.org/wiki/Reversible_process_(thermodynamics)http://en.wikipedia.org/wiki/Thermodynamic_efficiencyhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Rotational_motionhttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Power-to-weight_ratiohttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Steam_enginehttp://en.wikipedia.org/wiki/Reciprocating_enginehttp://en.wikipedia.org/wiki/Charles_Algernon_Parsonshttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Thermal_energy


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FRANCIS TURBINE

James B Francis

Reaction turbine

Previously Radial now is Mixed Flow


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PARTS OF FRANCIS TURBINE Casing

Guide Mechanism

Runner

Draft Tube


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SECTIONAL VIEW OF FRANCIS TURBINE


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ORK DONE

weight of water per second the runner.

acceleration due to gravity.

Velocity of flow at inlet

velocity of flow at outlet

velocity of vane at inlet

velocity of vane at outlet


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HYDRAULIC EFFICIENCY

It is defined as the ratio of power available to RUNNERto power provided at inlet.

Net head available at inlet to runner.


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MECHANICAL EFFIFCIENCY

It is defined as the ratio of SHAFT POWER to poweravailable to the RUNNER.

Shaft power

IMPACT OF WATER STRIKING RUNNER


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IMPACT OF WATER STRIKING RUNNER

BLADES


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WORKING OF FRANCIS TURBINE

WORKING PROPORTIONS IN FRANCIS


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WORKING PROPORTIONS IN FRANCIS

TURBINE.

It is the ratio of width of runner to the diameter of runner

FLOW RATIOIt is the ratio of f low velocity to spouting velocity.

SPEED RATIOIt is the ratio ofvelocity of vane to spouting velocity.


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WORKING OF FRANCIS TURBINE

It is a reaction turbine in which water enters the runnerradiallyAt its outer periphery and leaves axially at its centre.


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The water from penstock enters a scroll casing.

From the scroll casing the water passes through speed ring.

From the speed ring water passes through a series of guide

vanes.


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The change in direction of flow from radial to axial, as it passes

th h th d i f ti l f th


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through the runner, produces a circumferential force on the

runner, which make the runner to rotate.

The torque produced by the runner is transmitted to the

generator through the shaft which is connected to the generator

shaft.


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POWER GENERATION For power generation using francis turbine the turbine issupplied with high pressure which enter the turbine

radially inflow and leaves axially throughout draft tube.

The energyfrom water flow is transferred to the shaft ofthe turbine in form of torque and rotation.

The turbine shaft is coupled with dynamos or alternators

for power generation.

Francis Turbine Power Plant : A Continuous Hydraulic
http://www.brighthub.com/guides/energy.aspxhttp://www.brighthub.com/guides/energy.aspx


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y

System


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WORKING PROPERTIES The ratio of the width B to the diameter D of the runnerrepresented by n, that is

n = (B/D)

The value of n ranges from 0.10 to 0.45

The ratio of velocity of flow at inlet tip of the vane to the

spouting velocity is known as flow ratio which value

ranges from 0.15 to 0.3.

DRAFTING TUBE


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DRAFTING TUBE

The piping system for a reaction-type hydraulic turbine that allows the turbine tobe set safely above tail water and yet utilize the full head of the site from head

race to tail race.

The HydroTurbineOutput

Draft Tube

Example of a conical draft tube coupled to ahorizontal shaft turbine with a cast iron

quarter turn (90 degree) elbow


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THE PURPOSE OF DRAFT TUBE IN HYDRAULICTURBINES

Draft tube has following purpose It makes possible the installation of the turbine above the tail race levelwithout the loss of head.

The velocity of water at the runner outlet is very high. By employing a draft

tube of increasing cross sectional area, the discharge takes place at a muchlower velocity and thus, a part of the kinetic energy that was going as a waste isrecovered as a gain in the pressure head, and this increases the efficiency of theturbine.

The draft tube prevents the splashing of water coming out of the runner and

guides the water to the tail race.


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DRAFT TUBEINSTALL, TechnicalAnimation


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DIFFERENT TYPE OF DRAFT TUBES


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DRAFT TUBE THEORY AND EFFICIENCY

Out let of draft tube

Inleto

fdraft

tu

be

Hs

y

Turbine casing

Tale race

11

22


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Efficiency Of the Draft Tube :

The efficiency of draft tube is defined as the ratio of actual conversion ofkinetic head into pressure head in the draft tube to the kinetic energy headAt the inlet of the draft tube . It is denoted by d .


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Kaplan turbine The Kaplan turbine is a propeller-type water turbine which has

adjustable blades. It was developed in 1913 by the Austrianprofessor Viktor Kaplan, who combined automatically-adjustedpropeller blades with automatically-adjusted wicket gates toachieve efficiency over a wide range of f low and water level.

The Kaplan turbine was an evolution of the Francis turbine. Itsinvention allowed efficient power production in low-headapplications that was not possible with Francis turbines.

Kaplan turbines are now widely used throughout the world inhigh-flow, low-head power production.


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A Bonneville Dam Kaplan turbine after 61 years

of service


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DESIGN OF KAPLAN TURBINE To generate substantial amount of power

from small heads of water using KaplanTurbine it is necessary to have large flow ratesthrough the turbine. Kaplan Turbine is

designed to accommodate the required largeflow rates. Except the alignment of the bladesthe construction of the Kaplan Turbine is verymuch similar to that of the Francis Turbine.The overall path of f low of water through theKaplan Turbine is from radial at the entranceto axial at the exit. Similar to the FrancisTurbine, Kaplan Turbine also has a ring offixed guide vanes at the inlet to the turbine.

Theory of operation


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Theory of operation The Kaplan turbine is an inward flow reaction turbine, which

means that the working fluid changes pressure as it movesthrough the turbine and gives up its energy. The design combinesradial and axial features.

The inlet is a scroll-shaped tube that wraps around the turbine'swicket gate. Water is directed tangentially through the wicket gateand spirals on to a propeller shaped runner, causing it to spin.

The outlet is a specially shaped draft tube that helps decelerate the

water and recover kinetic energy . The turbine does not need to be at the lowest point of water flow,

as long as the draft tube remains full of water. A higher turbinelocation, however, increases the suction that is imparted on theturbine blades by the draft tube. The resulting pressure drop maylead to cavitation.


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Variable geometry of the wicket gate and turbine bladesallow efficient operation for a range of flow conditions.

Kaplan turbine efficiencies are typically over 90%, but maybe lower in very low head applications.

Current areas of research include CFD driven efficiency

improvements and new designs that raise survival rates offish passing through.

Because the propeller blades are rotated by high-pressure

hydraulic oil, a critical element of Kaplan design is tomaintain a positive seal to prevent emission of oil into the

waterway. Discharge of oil into rivers is not permitted


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Vertical Kaplan Turbine (courtesy Voith-

Siemens).


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WORKING OF KAPLAN TURBINE The working head of water is low so large flow rates areallowed in the Kaplan Turbine. The water enters theturbine through the guide vanes which are aligned such asto give the flow a suitable degree of swirl determinedaccording to the rotor of the turbine. The f low from guide

vanes pass through the curved passage which forces theradial flow to axial direction with the initial swirl impartedby the inlet guide vanes which is now in the form of free

vortex. The axial flow of water with a component of swirl applies

force on the blades of the rotor and looses its momentum,

both linear and angular, producing torque and rotation(their product is power) in the shaft. The scheme forproduction of hydroelectricity by Kaplan Turbine is same asthat for Francis Turbine.


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Applications


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Applications

Kaplan turbines are widely used throughout the worldfor electrical power production. They cover the lowesthead hydro sites and are especially suited for high flow

conditions. Inexpensive micro turbines are manufactured for

individual power production with as little as two feetof head.Kaplan turbine is low head turbine.

Large Kaplan turbines are individually designed foreach site to operate at the highest possible efficiency,typically over 90%. They are very expensive to design,manufacture and install, but operate for decades.


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Variations The Kaplan turbine is the most widely used of the

propeller-type turbines, but several other variations exist:

Propeller turbines have non-adjustable propeller vanes.They are used in where the range of head is not large.

Commercial products exist for producing several hundredwatts from only a few feet of head. Larger propeller turbinesproduce more than 100 MW.

Bulb or Tubular turbines are designed into the water

delivery tube. A large bulb is centered in the water pipewhich holds the generator, wicket gate and runner. Tubularturbines are a fully axial design, whereas Kaplan turbineshave a radial wicket gate.


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Pit turbines are bulb turbines with a gear box. This

allows for a smaller generator and bulb. Straflo turbines are axial turbines with the generator

outside of the water channel, connected to theperiphery of the runner.

S- turbines eliminate the need for a bulb housing byplacing the generator outside of the water channel.This is accomplished with a jog in the water channeland a shaft connecting the runner and generator.


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KAPLAN TURBINE It is axial flow reaction turbine. In it fraction of available hydraulic energy is converted into kinetic

energy before fluid enters the runner.

Both pressure and velocity changes as the fluid passes through the

runner, at inlet much higher than the outlet. Runner must be enclosed with water tight casing.

Water is admitted over entire circumference.

Water completely fills the passage between blades and while flowingbetween the inlet and outlet section does not work on the blades.

The turbine connects the tail race through draft tube, it maybeinstalled above or below the tail race.

The flow regulation is carried out by means of guide vane assembly.Other component parts are scroll casing, stay ring, runner and drafttube.

Kaplan Turbine


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Kaplan Turbine


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PELTON TURBINE It is an Impulse turbine. The water flows in through a nozzle and it is the jet so produced

which strikes the runner. In it velocity rate changes and the pressure remains constant

(atmospheric). It is not necessary to enclose runner water tight, it just prevents

splashing and guides water to tail. Water is admitted in form of jets. The turbine does not run full and air has a free access to bucket.

The turbine is installed above the tail race and there is no drafttube used. The flow regulation is done by means of needle valve fitted into

the nozzle.

P lt n Turbin


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Pelton Turbine


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In order to predict the behavior of a turbineworking under varying conditions of head,speed, output and gate opening, the results areexpressed in terms of quantities which may beobtained when the head on the turbine is

reduced to unity.The following are three important unitquantities which must be studied under unithead.

1.Unit speed

2.Unit power3.Unit discharge

Unit Speed :


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Unit Speed :It is defined as speed of the turbine working under a unit head.It is denoted by Nu. The expression for unit speed is obtainedas.

N=speed of a turbine under a head H,H=Head under which turbine is working,

U=Tangential velocityThe tangential velocity absolute velocity of water and head onturbine are related as

uvHAlso u=DN/60

So nHN=K1H

here K1

is constant of proportionalityIf Head on turbine becomes unity or H=1,N=NUSubstituting we get NU =K11=K1

So N=NUH

Unit discharge :


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It is defined as the discharge passing through theturbine. It is denoted by the symbol QU. The expression

for unit discharge is given as

Let H=head of water on turbineQ= discharge passing through turbine when head is H

on turbinea= area of flow of water

The discharge passing through a given turbine under ahead H Is given by Q= area of f low *velocity

But for a turbine area of flow is constant and velocity isproportional to H

So Q=K2HK2being the constant of proportionality

If H=1 Q=QU

Substituting these values we getQ=K21=K2

Substituting the value of K2Q=QUH

Unit Power :It is defined as power developed by a turbine working under a unit head . Itis denoted by the symbol Pu The expression for unit power is obtained as


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is denoted by the symbol Pu. The expression for unit power is obtained asLet H= Head of water on the turbine

P=Power developed by turbine under a head of HQ=Discharge through turbine under a head H

The overall efficiency o=power developed/water power=P/(*g*H*Q/1000)

P=o**g*Q*H/1000 Q*H

(H*H)H^3/2SO,P=K3H^3/2

K3being the constant of proportionalityWhen H=1, P=Pu

So, Pu=K3Substituting the value of K3,

P=PuH^3/2

Use of unit quantities:

If a turbine is working under different heads the behavior of the


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If a turbine is working under different heads, the behavior of theturbine can be easily known from the values of the unit quantities,i.e., from the values of unit speed, unit discharge and unit power.

H1,H2,are the heads under which a turbine works,N1,N2,are the corresponding speeds,

Q1,Q2,are the discharge, andP1,P2,are the power developed by the turbine.

Using the above equations

Nu= N1/(H1)=N2/(H2)Qu= Q1/(H1)= Q2/(H2)

Pu= P1/(H1^3/2)= P2/(H2^3/2)

Hence, if the speed discharged and power developed by a turbineunder a head are known, then by using above equations, the speed,

discharge and power developed by the same turbine under adifferent head can be obtained easily.


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Cavitation Cavitation is formation of vapour bubbles in the liquid

flowing through any Hydraulic Turbine. Cavitationoccurs when the static pressure of the liquid falls

below its vapour pressure. Cavitation is most likely tooccur near the fast moving blades of the turbines andin the exit region of the turbines


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Cavitation in Francis turbine

C f C it ti
http://en.wikipedia.org/wiki/File:Turbine_Francis_Worn.JPG


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Causes of Cavitation

The liquid enters hydraulic turbines at high pressure; this pressure is acombination of static and dynamic components.

Dynamic pressure of the liquid is by the virtue of f low velocity and theother component, static pressure, is the actual fluid pressure which thefluid applies and which is acted upon it.

Static pressure governs the process of vapour bubble formation orboiling.

Cavitation can occur near the fast moving blades of the turbine wherelocal dynamic head increases due to action of blades which causesstatic 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 willlead to fall in static pressure causing Cavitation.

D i l Eff f C i i


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Detrimental Effects of Cavitation

The bubbles collapsing near the machine surfaceare more damaging and cause erosion on thesurfaces called as cavitation erosion.

The collapses of smaller bubbles create higherfrequency waves than larger bubbles. So, smallerbubbles are more detrimental tothe hydraulic machines.


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CHARACTERISTIC


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CURVES OF HYDRAULIC

TURBINE

six parameters varied during a test on turbine are speed (N), head (H), discharge (Q),

power (P), overall efficiency (0) and gate opening. variations of dependent parameters wrt independent parameters (N, H, Q) are plotted to

obtain characteristic curves. To determine the exact behaviour of turbines under varying conditions.

TYPES OF


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TYPES OF

CHARACTERISTIC CURVES

Main characteristic curves or Constant head curve

Operating characteristic curves or Constant speedcurve

Muschel curves or Constant efficiency curve

MAIN CHARACTERISTIC


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MAIN CHARACTERISTIC

CURVES

Maintaining a constant head at particular gate openingthe speed of the turbine is varied by admittingdifferent rates of flow and power P is measured

mechanically.From each test the unit power Pu, the unit speedNu,

the unit discharge Quand the overall efficiency oaredetermined.

Curves plotted between Nu(as abscissa) and Qu, Puor0 ,head(H) and gate opening kept constant

Also called Constant Head Curves

onstant ea aracter st csfor Pelton Wheel


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for Pelton Wheel

100% GO

75% GO

50% GO

25% GO

Nu

o

100% GO

75% GO

50% GO

25% GO

Nu

Pu

N is constant

Constant Head Characteristicsfor Francis Turbine


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for Francis Turbine

Constant Head Characteristicsfor Kaplan Turbine


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for Kaplan Turbine

OPERATINGCHARACTERISTIC CURVES


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CHARACTERISTIC CURVES

Tests are conducted at a constant speed varying the headHand suitably adjusting the discharge Q. The powerdeveloped Pis measured mechanically.

The curves drawn areP vs Q

o vs Q

o vs Pu

o maxvs % Full load

Curves plotted between discharge (Q) and power (P) orefficiency (0) , speed is kept constant

Also called Constant Speed Curves

Constant Speed Curves


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Constant Speed Curves


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ISO-EFFICIENCY CURVES


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ISO EFFICIENCY CURVESPlotted from data which can be obtained from the constant

head and constant speed curves.

To determine the zone of constant efficiency so that we canalways run the turbine with maximum efficiency.

Gives a good idea about the performance of the turbine atvarious efficiencies

These are curves obtained between speed (N) versus

discharge (Q) and speed versus efficiency (0) for differentgate openings.

Also called Muschel Curves.


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Iso-efficiency Curves

Constant Efficiency

C


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Curves


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Governing of hydraulic turbinesRegulation of discharge with a view to maintain a

synchronous speed of the turbine runner is calledgoverning of turbine.

Done automatically by means of a governor


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Components of A Governor1. Pendulum or actuator

2. Servo motor.

3. Relay valve

4. Oil Pump

5. Oil Supply Pipes


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Governing of Impulse TurbineSudden drop in load

Speed increases

the deflector is broughtbetween nozzle andbuckets

Spear and deflector are

operated automaticallyby means of a centrifugalgoverner

Load increases Speed decreases

The piston of servomotormoves spear to the left

This causes increase inannular area i.e.

increases discharge


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Governing Of Reaction TurbineThe Guide vanes are pivoted and connected by levers and

links to the regulating ring.

The motion of the servo motor piston is transmitted tothe regulating ring which causes all the guide vanes to

turn simultaneously in one direction through the sameangle

Thus the area of f low passage is increased or reducedaccording to the load on the turbine.

URGE TANKS


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Surge tank is an additional storage spaceor reservoir

fitted between the main storage reservoir and the powerhouse

Usually provided in high or medium-head plants whenthere is a considerable distance between the water source

and the power unit

The main functionsof the surge tank are 1)To control the pressure variations , due to rapid changes

in the pipeline flow , thus eliminating water hammerpossibilities.

2)To regulate the f low of water to the turbine byproviding necessary retarding head of Water.


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Surge tank


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TYPES OF SURGE TANKS1)Simple Surge Tank

2)Restricted Orifice type Surge Tank

3)Differential Surge Tank.


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NEW TYPES OF TURBINES

DERIAZ / DIAGONAL TURBINE

TUBULAR TURBINE

BULB TURBINE

DERIAZ TURBINE Is named after its inventor Paul Deriaz, a hydraulic designer


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y g

Water passes through the runner at angle of 45 to the axis, hencealso called diagonal turbine

Similar to a Kaplan turbine as the blades are adjustable but hasinclined blades to make it more suitable for heads between 20m to150m

Advantages:(1) smooth and efficient operation over a wide range of head andload

(2) uniform distribution of pressure and load across the blade(3) freedom from development of cavitation across the entireoperating range.

Major Deriaz turbine system are installed at plants on both the

Canadian and U S sides of Nia ara Falls

Vertical Deriaz turbine


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Takami Power Station

TURBINE


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A TURBINE is a rotary engine thatExtracts energy from a fluid flow andConverts it into useful work

TYPES OF TURBINES

1. REACTION TURBINE2. IMPULSE TURBINE


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PELTON TURBINE


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FRANCIS TURBINE


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FRANCIS TURBINE

TYPES OF TURBINES


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TYPES OF TURBINES

1. Tangential flow turbine2. Radial flow turbine3. Axial flow turbine

4. Mixed flow turbine

USES OF TURBINES


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1. Most get engines rely on turbines2. In generation of electricity3. In space shuttles as turbo pumps

4. As turbo charger in aircraft engines5. In turbo expanders


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THANK YOU

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