HYDRAULIC TURBINES Hydraulic machines - PowerPoint Presentation

Slide1

HYDRAULIC TURBINESSlide2

Hydraulic machines

Machines which convert hydraulic energy(energy possessed by water) into mechanical

energy: turbine

Machines which convert mechanical energy into hydraulic energy-

PumpsSlide3

H

ydro-electric power plant

Hydraulic

Turbines convert hydraulic energy of water into mechanical energy which is further converted into electrical energy. This energy obtained is know as hydro-electric power which is one of the cheapest forms of energy generation.Slide4

Layout of a Hydro-Electric Power PlantSlide5

Efficiencies of a turbine

Hydraulic efficiency

η

Mechanical efficiency

η

Volumetric efficiency

ηOverall efficiency η

h

m

v

oSlide6

Classification of turbines

Based on :

A

ction of fluid on turbine blades

Impulse turbine, Reaction turbine

Direction of flow through the runner Tangential flow , Radial flow, Axial flow, Mixed flow

Head of the turbine

High head , Medium head , Low head

Specific speed

High speed , Medium speed, Low speed Slide7

PELTON WHEEL (1889

) Slide8

Pelton Wheel

In a Pelton Wheel or Pelton Turbine water strikes the vanes along the tangent of the runner and the energy available at the inlet of the turbine is only kinetic energy, therefore it is a

tangential flow impulse turbine

.

This turbine is used for high heads and named after L.A Pelton, an American engineer.Slide9

Working Principle

The high speed water coming out of the nozzle strikes the splitter which divides the jet into two equal streams. These stream flow along the inner curve of the bucket and leave it in the direction opposite to that of incoming jet. The high pressure water can be obtained from any water body situated at some height or streams of water flowing down the hills.

The change in momentum (direction as well as speed) of water stream produces an impulse on the blades of the wheel of Pelton Turbine. This impulse generates the torque and rotation in the shaft of Pelton Turbine.

9Slide10

Main Parts of a Pelton Wheel

Nozzle

: It controls the amount of water striking the vanes of the runner.

Casing

: It is used to prevent splashing of water and plays no part in power generation.

Runner with buckets

:

Runner is a circular disc on the periphery of which a number of evenly spaced buckets are fixed.

Breaking Jet

: To stop the runner in short time breaking jet is used.Slide11
Slide12

Runner of a Pelton Turbine

SPLITTER

BUCKETS OR VANES

RUNNER

12Slide13

Pelton

wheel

Rotation

v

1

(jet velocity)=

v

w1

u

1

R

1

u

2

= u

1

v

2

v

r2

R

2

= R

1



2

α

2Slide14

Pelton

turbine working proportionsSlide15

Bucket design StandardsSlide16

Turbines

: Pelton

wheel Slide17

Radial flow impulse turbineSlide18

Turbines

: Francis (1849)Slide19

Francis Turbine

Francis Turbine is the first hydraulic turbine with radial inflow. It was designed by an American scientist James Francis

.

If the water flows radially through the runner , from outwards to inwards

then it

is known as an

inward radial flow turbine

.

Francis turbine

is a reaction turbine as the energy available at the inlet of the turbine is a combination of kinetic and pressure

energy.

19Slide20

Main parts of a Francis

Turbine

CASING

: The runner is completely enclosed in an air-tight spiral casing. The casing and runner are always full of water.

GUIDE MECHANISM

: It consists of a stationary circular wheel on which stationary guide vanes are fixed. The guide vanes allow the water to strike the vanes of the runner without shock at inlet

RUNNER

: It is a circular wheel on which a series of curved radial guide vanes are fixed.

DRAFT TUBE

: It is used for discharging water from the outlet of the runner to the tail race.

20Slide21
Slide22

B2.2.4

Hydropower system design Turbines: Francis Slide23

RUNNER

GUIDE WHEEL

MOVABLE VANES

STATIONARY GUIDE

VANES

23Slide24

K

aplan

T

urbine

Kaplan turbine is an axial flow reaction

turbine.The

water flows through the runner of the turbine in an axial direction and the energy at the inlet of the turbine is the sum of kinetic and pressure energy .

In an axial flow reaction turbine the shaft is vertical. The lower end of the shaft is larger and is known as ‘

hub

’ or ‘

boss

’. It is on this hub that the vanes are attached. If the vanes are adjustable then it is known as

kaplan Turbine

and if the vanes are non adjustable then it is known as

Propeller Turbine

.

24Slide25

Kaplan turbine is best suited where large quantity of low head water is available.

The main parts of a kaplan Turbine are:

Scroll Casing

Guide vane Mechanism

Hub with Vanes

Draft Tube

25Slide26

Kaplan

Turbine

Runner

HUBB OR

BOSS

VANES

SHAFT

26Slide27

Working Principle

The water enters the turbine through the guide vanes which are aligned such as to give the flow a suitable degree of swirl. The flow from guide vanes pass through the curved passage which forces the radial flow to axial direction.

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 for production of hydroelectricity by Kaplan Turbine is same as that for Francis Turbine.

27Slide28

Schematic View

GUIDE VANES

MOVABLE

VANES

SHAFT

HUBB OR BOSS

28Slide29

Draft Tube

The draft tube is a pipe of gradually increasing area which connects the outlet of the runner with the tailrace. One end of the draft tube is connected to the outlet of the runner while the other end is submerged below the level of water in the tail race.

It creates a negative head at the outlet of the runner thereby increasing the net head on the turbine.

It converts a large proportion of rejected kinetic energy into useful pressure energy

29Slide30

Elbow-Type Draft Tube

30Slide31

31Slide32

Specific Speed and selection of turbinesSlide33
Slide34
Slide35

Governing of Turbines

It is the operation by which the speed of the turbine is kept constant under all conditions of working load. This is done automatically by a governor which regulates the rate flow through the turbines according to the changing load conditions on the turbine.

Governing of a turbine is absolutely necessary if the turbine is coupled to an electric generator which is required to run at constant speed under all fluctuating load conditions.

35Slide36

36Slide37

37Slide38

38Slide39
Slide40

B2.2.4

Hydropower system design

Turbines: Characterising turbines: Specific speed: Dimensional specific speedSlide41

B2.2.4

Hydropower system design Turbines: Characterising turbines Slide42

B2.2.4

Hydropower system design Turbines: Characterising turbines Slide43

B2.2.4

Hydropower system design Turbines: Cavitation Slide44

B2.2.4

Hydropower system design Turbines: Cavitation Slide45

B2.2.4

Hydropower system design Turbines: Cavitation