Steam turbine and its types

APPLIED MECHANICAL ENGINEERING

STEAM TURBINESH ighly Mechanized!

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TABLE OF CONTENTS

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INTRODUCTION

We’ll learn in this presentation:

WORKING PRINCIPLE

CLASSIFICATION

WORK DONE & EFFICIENCY


INTRODUCTION

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Under this head, we’ll discuss:

DEFINATION1

ACTION OF STEAM2

ADVANTAGES OF STAM TURBINES OVER R. STEAM ENGINES

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DEFINATION

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A prime mover in which rotatory motion is obtained by the gradual change of momentum of the steam

‘‘ ’

’

A machine that transforms energy from thermal, electrical or pressure form to mechanical

form


ADVANTAGES OF STEAM TURBINE OVER R. STEAM ENGINE

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SPEED STEAM RANGE

EFFICIE-NCY

STEAM CONSU-MPTION

SAFETY

FRICTIONAL

LOSSAPPLIED TORQUE

REPAIR

COSTSPACE REQUIRED


ADVANTAGES OF STEAM TURBINES OVER R. STEAM ENGINES

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


WORKING PRINCIPLE

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Under this head, we’ll discuss:

GENERAL PARTS1

PRINCIPLE OF ACTION2


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SAFETY


GENERAL PARTS OF STEAM TURBINE

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NOZZLE

Heat energy of the high pressure steam is converted into kinetic energy

BLADES

Change direction of steam issuing from the nozzle


The generation of high velocity steam jet by the expansion of high pressure steam and then conversion of kinetic energy, so obtained into mechanical work on rotor blades.

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’’

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PRINCIPLE OF ACTION

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


CLASSIFICATION

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BLADE FLOW PASSAGE

The steam turbine are classified on the basis of:

CYLINDER FLOW ARRANGMENT

DIRECTION OF FLOW

NUMBER OF STAGES

APPLICATION OF TURBINE

SPEED OF TURBINE

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


ON BASIS OF BLADE FLOW PASSAGE

IMPULSE TURBINE

REACTION TURBINE

*THESE TYPES ARE DISCUSSED IN DETAIL IN LATER SLIDES

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


ON BASIS OF CYLINDER FLOW ARRANGMENT

Single cylinder turbines are the one which have all the stages enclosed in one cylinder while in multi cylinder turbines the stages are accommodated in morethan one cylinders, say two or three. Flow in these can be single flow, double flow, cross flow or reversed flow.

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


ON BASIS OF DIRECTION OF FLOW

RADIAL FLOW TURBINE

TANGENTIAL FLOW TURBINE

AXIAL FLOW TURBINE

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


RADIAL FLOW TURBINE

Radial flow turbine incorporates two shafts end to end and can be

of suitably small sizes.

Radial flow turbines can be started quickly and so well suited for

peak load and used as stand by turbine or peak load turbines.

These are also termed as LJUGSTROM TURBINE.

Radial flow turbines were developed by B.F. Ljungstorm of Sweden

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


RADIAL FLOW TURBINE In radial flow turbines the steam is injected in middle near shaft and steam flows radially outwards through the successive moving blades placed concentrically. In radial flow turbines there are no stationary blades so pressure drop occurs in moving blade passage. Concentric moving blades rings are designed to move in opposite directions. 15



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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


TANGENTIAL FLOW TURBINE The steam is the nozzle directs steam

tangentially into buckets at the

periphery of single wheel and steam

reverses back and re-enters other

bucket at its’ periphery.

This is repeated several times as steam

follows the helical path.

Tangential flow turbines are very robust

but less efficient. 16



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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


AXIAL FLOW TURBINE

Steam flows along the axis of turbine

over blades. These axial flow turbines are well suited

for large turbo generators and very

commonly used presently.

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


ON BASIS OF NUMBER OF STAGES

SINGLE STAGE TURBINE

MULTI STAGE TURBINE

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


ON BASIS OF APPLICATION OF STEAM

CONDENSING TURBINE

PASS OUT TURBINE

NON- CONDENSING TURBINE

BACK PRESSURE TURBINE

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SPEED & STEAM RANGE

EFFICIE-NCY

STEAM CONSUM

-PTIONSAFETY

FRICTION-AL LOSS

APPLIED TORQUE

ATTENTION & REPAIR

COST


ON BASIS OF SPEED OF TURBINE

LOW SPEED TURBINE

NORMAL SPEED TURBINE

HIGH SPEED TURBINE

>3000 RPM

= 3000 RPM

<3000 RPM 20


IMPULSE TURBINE

A turbine which runs by the impulse of steam jet‘

‘ ’’

The force because of change in tangential component of velocity of fluid which may be due to change in direction or magnitude.

The steam is first made to flow through nozzle. Then the steam impinges on the turbine blades. After impinging, steam glides over the concave

surface of the blades and finally, leave the turbine. 21


DE-LEVEL IMPULSE TURBINEThe simplest type of impulse turbine & most commonly used.

MAIN COMPONENTS:

1. NOZZLE

2. RUNNER AND BLADES

3. CASING 22


MAIN COMPONENTS

NOZZLE

It is a circular guide mechanism. It regulates the flow of steam. It is kept close to the blades, in

order to minimize the losses due

to windage.

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MAIN COMPONENTS

RUNNER & BLADES:

These consist of a circular disc fixed

to a horizontal shaft. The steam jet impinges on the buckets,

which move in the direction of the jet. This movement of the blades makes the

runner to rotate. 24


MAIN COMPONENTS

CASING:

It is air-tight metallic case, which

contains the turbine runner and blades. It controls the movement of steam

from the blades to the condenser. It is essential to safegaurd the runner

against any accident. 25


DE-LEVEL IMPULSE TURBINE

PRESSURE & VELOCITY OF STEAM IN AN IMPULSE TURBINE

The pressure of steam jet is reduced in the nozzle and

remain constant while passing through the moving

blades. The velocity of steam is increased in the nozzle, and is

reduced while passing through the moving blades.

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DE-LEVEL IMPULSE TURBINE


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REACTION TURBINE

MECHANISM

The steam enters through a section

of curved blades in a fixed position. The steam then enters the set of

moving blades and creates enough

reactive force to rotate them. The steam exits the section of

rotating blades. The direction of rotation.

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REACTION TURBINE

The water enters the guide case of the turbine with high

potential energy and relatively low kinetic energy.

The potential energy, which is a function of the pressure

difference between the runner inlet and exit, causes the fluid

to flow through the runner buckets.

As the fluid flows over the curved surface of the runner

buckets, the fluid velocity on one side of the bucket is higher

than on the opposite side. 29


REACTION TURBINE

This difference in velocity on the surfaces of the bucket causes a

pressure differential across the bucket which exerts a force on

the bucket. This force at its respective radius in the runner, the revolving

part, then causes the runner to restore and impart mechanical

energy to the turbine shaft. 30


PARSON’S REACTION TURBINEThe simplest type of reaction turbine & most commonly used.

MAIN COMPONENTS:

1. CASING

2. GUIDE MECHANISM

3. TURBINE RUNNER

4. DRAFT TUBE 31


MAIN COMPONENTS

CASING

It is an air-tight metallic case, in which

the steam from the boiler, under high

pressure & temperature. This casing is designed in such a way

that steam enters the fixed blades

with a uniform velocity. 32


MAIN COMPONENTS

GUIDE MECHANISM

It is mechanism, made up with the

help of guide blades, in the form of a

wheel. This wheel is, generally fixed to casing;

that is why these guide blades are

called FIXED BLADES. 33


MAIN COMPONENTS

GUIDE BLADES

Allow the steam to enter the runner

without shock.

Allow the required quantity of steam

to enter the turbine.

They are properly designed in order to:

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MAIN COMPONENTS

TURBINE RUNNER

The turbine runners consists of runner

blades fixed to a shaft or rings.

The surface of the turbine runner is

made smooth to minimize the

frictional looses. 35


MAIN COMPONENTS

DRAFT TUBE

The steam, after passing through

runner, flow into the condenser

through a tube called DRAFT TUBE

In case of its absence, steam eddies

are caused. 36


PARSON’S REACTION TURBINE

PRESSURE & VELOCITY OF STEAM IN REACTION TURBINE

The pressure in a reaction turbine is reduced in fixed

blades as well as in moving blades. The velocity of steam is increased in the fixed blades

and is reduced while passing through the moving

blades.37


PARSON’S REACTION TURBINE


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COMPARISON

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2

3

4

5

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WORK DONE & EFFICIENCY

In order to determine the work done and efficiencyof steam turbine, we’ll consider:

RANKINE CYCLE

Rankine cycle is a thermodynamic cycle derived from Carnot vapour power cycle for overcoming itslimitations.

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RANKINE CYCLE

1 - 2ISOBARIC HEAT

SUPPLY 3 - 4ISOBARIC HEAT

REJECTION

2 - 3ADIABATIC EXPANSION 4 - 1

ADIABATIC PUMPING

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UNDERSTANDING THE ARRANGMENT

1 - 2High pressure water supplied by feed pump is heated and transformed into steam with or without superheat as per requirement. This high pressure and temperature steam is sent for expansion in steam turbine. Heat added in boiler, for unit mass of steam.

QSUPPLY = (h2 – h1)

Steam available from boiler is sent to steam turbine, where it's adiabatic expansion takes place and positive work is available. Expanded steam is generally found to lie in wet region.

Wturbine = (h2 – h3)

2 - 3

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UNDERSTANDING THE ARRANGMENT

Heat rejection process occurs in condenser at constant pressure causing expanded steam to get condensed into saturated liquid at state 4.

Qrejected = (h3 – h4)

Condensate available as saturated liquid at state 4 is sent to feed pump for being pumped back to boiler at state 1.

Wpump = (h1 – h4)

3- 4

4 - 1

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ANALYTICAL ANALAYSIS

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IMPROVEMENT IN ITS EFFICIENCY

REDUCING HEAT ADDITION IN

BIOLER

REDUCING FEED PUMP WORK

INCREASING STEAM TURBINE

EXPANSION WORK

USING HEAT REJECTED AT CONDENSOR

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Design

Steam turbine and its types