This document provides a detailed introduction to steam turbines, covering their working principles, classification, and different operating cycles. It explains the components and functioning of steam turbine systems within thermal power plants, including the concepts of multi-staging and compounding. Additionally, it outlines various types and specific designs of steam turbines used in nuclear and fossil fuel applications.

1. GE-Confidential
STEAM TURBINE FUNDAMENTALS-
I
28th
September 2007
B.V.Subbarao

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INTRODUCTION
Material compiled in the subsequent pages is meant for
educational purpose. Some of the pictures and contents
taken and presented here are from the articles read from
net with the courtesy of the respective authors.
This PPT is only meant for the internal use within GEDC -
ST Engineering.
Fore-word

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SCOPE OF THE MODULE
1
 Introduction to Steam Turbines
 Working Principle - Change of State Across Stage
 Classification based on Applications
Utility Size Operating principles
 Explanation of thermal power plant
Boiler Turbine Condenser Condensate pumps
 Steam turbine operating cycles
Simple Rankine Cycle - Modified cycles advantages
Reheat Cycles - Regenerative cycle
Combined cycles - Co-generative cycle
 Compounding of steam turbines
Pressure - Velocity & Pressure Velocity Compounding
Cross compounding - Tandem Compounding

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INTRODUCTION
 Steam Turbines are rotating equipments used to produce
Mechanical Power from Thermal Energy of steam
 Steam turbines are mostly 'axial flow' types. (Steam flows
over the blades in a direction parallel to the axis of the
wheel.)
WHAT IS A STEAM TURBINE !!

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WORKING PRINCIPLE
 The steam is expanded in nozzles, resulting in the formation of a
high velocity jet. This impinges on the moving blades, mounted on a
shaft.
 Here it undergoes a change of direction of motion which gives rise
to a change in momentum
 The shaft power in a turbine is obtained by the rate of change in
momentum of a high velocity jet of steam impinging on a curved
blade which is free to rotate.
HOW DOES IT WORK !!

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CLASSIFICATION
Application - Utility , Captive & Mechanical drives
Size - Small < 15 MW
- Medium > 15 MW
- Large > 300 MW
Type - Condensing & Back Pressure
Principle - Impulse & Reaction
VARIOUS TYPES !!!

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Impulse : Most of the
pressure drop for the
stage takes place in
nozzle
Reaction : Pressure drop
in a stage takes place
approximately 50% in
Nozzle and 50% in
Buckets
WORKING PRINCIPLE
contd.
Basically Steam
Turbines are 2 types

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Impulse
WORKING PRINCIPLE
contd.
Reaction

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WORKING PRINCIPLE
contd.

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ABOUT THE FLUID
Fluid - Superheated Steam
Inlet pressure* - 2400 – 4500 PSIG
Inlet Temp* - 1000 – 1100 Deg F
*Sub Critical >= 2400 Psig -1000F (165 bar / 538 C)
*Super Critical >= 3500 Psig -1050F (240 bar / 565 C)
Ultra Supercritical >= 4500 Psig -1112F (310 bar / 600 C)
Improvements in power plant performance are achieved by raising
inlet steam conditions to Supercritical and Ultra supercritical levels

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OPERATING PRINCIPLE
 The high-temperature, high-pressure steam enters the inlet control
valves, which control the steam flow into the turbine.
 The steam then travels through the first-stage nozzles, and strikes the
first row of buckets. At this point the pressure decreases as the steam
passes through the nozzles.
 As the steam passes through each stage in a Turbine, the steam
conditions vary (i.e. Pressure and Temperatures reduce and specific
Volume and entropy increases.)
 The expanding steam continues to flow through the rows of nozzles and
buckets, each time striking the next row of buckets with a high velocity
and causes the shaft to rotate to produce power.
 Each row of nozzles and buckets designed for the conditions of steam
from previous stage.
 By the time the steam is ready to leave the turbine, almost all of its
usable energy has been removed ..

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ELEMENTS OF A POWER
PLANT
1.Boiler
2.Steam Turbine
3.Condenser
4.Feed Pump

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STEAM TURBINE OPERATING
CYCLE
Simple Rankine
4 to 1: Isobaric heat supply (Boiler) 1 to 2: Isentropic expansion (Steam turbine),
2 to 3: Isobaric heat rejection (Condenser), 3 to 4: Isentropic compression (Pump),
Critical point
Water line
Steam line ( saturated )
Wet steam zone
SIMPLE RANKINE CYCLE

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 Reheat cycles
 Regenerative cycle
 Combined Cycle
 Cogeneration Cycle
MODIFIED RANKINE
CYCLE
STEAM TURBINE OPERATING
CYCLE

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Reheat cycle one reheat Reheat cycle two reheats
STEAM TURBINE OPERATING
CYCLE

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Reheat cycle one reheat
STEAM TURBINE OPERATING
CYCLE

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STEAM TURBINE OPERATING
CYCLE

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Regenerative Cycle
STEAM TURBINE OPERATING
CYCLE

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CONCEPT OF MULTI STAGING
Stage : It is a combination of stationary nozzles and row of buckets. A
multi-stage turbine is one that has many sets of these nozzles and
buckets in series.
Multi-stage turbine : After the steam leaves the first set of nozzles, it
enters subsequent stages. Steam discharged from the buckets of the
upstream high-pressure stage becomes inlet to next stage.
Therefore, each consecutive stage operates at a lower pressure and the
total energy conversion of steam from the highest to the lowest pressure
is broken up in a series of stages which allow for better efficiency.

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CONCEPT OF MULTI STAGING
The specific volume increases due to expansion of steam in nozzles.
The steam passages are gradually widened to accommodate the
increasing volumetric flow rate, i.e., blade heights and wheel
diameters are increased.
Due to expansion of steam, the temperature drops down at every
stage. Each stage contributes a proportionate share of power to the
turbine shaft.
What happens to the steam
When it passes from one stage to the other !!

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COMPOUNDING OF STEAM
TURBINE
 Pressure Compounding
 Velocity Compounding
 Pressure Velocity Compounding
 Cross Compounding if all of the machines
are parallel
 Tandem Compounding if all the machines
are connected in series
What is compounding in steam turbines !!

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PRESSURE COMPOUNDING

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VELOCITY
COMPOUNDING

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PRESSURE – VELOCITY
COMPOUNDING

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COMPOUNDING CONTD/

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Steam Turbine Power Plants
Steam power plant cycles are characterized by the
pressure level they are operated
 Sub-critical cycles use steam pressures below the
critical pressure
 Super-critical cycles operate above the critical
pressure providing higher efficiency.

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Type of Steam Turbine is decided based on
 Steam parameters and Process Needs like Extraction
 Availability of cooling water for Condenser, Condensing
load and Back pressure
 Other Techno-economic considerations by the client
Steam Turbine Power Plants

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Customers Choice results in type of Plant
 Combined Cycle Power Plants Vs. Simple cycle
Power Plants
 Cogeneration Plants
 Regeneration and reheating for cycle efficiency
improvements
Steam Turbine Power Plants

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Steam turbine Models
Single / Multi casings , Tandem / Cross Compounded
Fossil Fuel Fired / Nuclear Steam turbines
Condensing Steam turbine
Back Pressure Steam turbine
Reheat and regeneration cycles
Cogeneration Steam turbine

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SIZING CRITEREA
Typical Ratios, # of stages for each size of turbines
 Number of stages in a turbine are fixed from the Enthalpy
drop required in each stage and length of rotor from rotor-
dynamic stand point.
 Stage diameter, Nozzle / Bucket heights are decided by
the volume flow rate
 Machine configuration is dictated by the Enthalpy drop
and steam Flow Rate
i.e., HP , IP , LP ( 2stage or 3 Stage )

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GE - Steam Turbine Nomenclature
 Section I, Reheat and Multi-Casing Non-Reheat Turbines includes
the more complex configurations in accordance with the traditional
practice of the Schenectady code system.
 Section II, Single-Casing, Non-Reheat Turbines, relatively simple
design

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SECTION I
REHEAT AND MULTIPLE-CASING, NON-REHEAT STEAM TURBINES
FULL-SPEED, REHEAT, SINGLE-FLOW CONDENSING TURBINES A
FULL-SPEED, NON-REHEAT, DOUBLE-FLOW CONDENSING TURBINES
C
FULL-SPEED, REHEAT, DOUBLE-FLOW CONDENSING TURBINES D
FULL-SPEED, TANDEM-COMPOUND, DOUBLE-FLOW, PRIMARY (DP) AND
DP /DS
SECONDARY (DS) CONDENSING ELEMENTS FOR CROSS-COMPOUND,FOUR-
FLOW, REHEAT TURBINES
FULL-SPEED, REHEAT, TRIPLE-FLOW CONDENSING TURBINES F
FULL-SPEED, TANDEM-COMPOUND, TRIPLE-FLOW, PRIMARY (FP) AND
FP/FS
SECONDARY (FS) CONDENSING ELEMENTS FOR CROSS-COMPOUND, SIX –
FLOW REHEAT TURBINES
FULL-SPEED, REHEAT, FOUR-FLOW CONDENSING TURBINES
G
FULL-SPEED, NON-CONDENSING ELEMENTS OF CROSS-COMPOUND TURBINES
H
HALF-SPEED, SINGLE-FLOW CONDENSING TURBINES J
HALF-SPEED, DOUBLE-FLOW CONDENSING TURBINES K
HALF-SPEED, TANDEM-COMPOUND DOUBLE-FLOW CONDENSING TURBINES
L
HALF-SPEED, TANDEM-COMPOUND FOUR-FLOW CONDENSING TURBINES
M
HALF-SPEED, TANDEM-COMPOUND SIX-FLOW CONDENSING TURBINES N

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SECTION II
SECTION II
SINGLE-CASING, NON-REHEAT STEAM TURBINES
CONDENSING TURBINES WITH NO CONTROLLED EXTRACTIONS OR ADMISSIONS
SC
NON-CONDENSING TURBINES WITH NO CONTROLLED EXTRACTIONS OR ADMISSIONS
SNC
CONDENSING TURBINES WITH A SINGLE CONTROLLED EXTRACTION OR ADMISSION
SAC
NON-CONDENSING TURBINES WITH A SINGLE CONTROLLED EXTRACTION OR
ADMISSION SANC
CONDENSINGTURBINES WITH TWO CONTROLLED EXTRACTIONS OR ADMISSIONS
DAC
NON-CONDENSING TURBINES WITH TWO CONTROLLED EXTRACTIONS OR ADMISSIONS
DANC

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Summary : Machines commonly used
Type Current
m/c
Description
A A14-A15 FULL-SPEED, REHEAT, SINGLE-FLOW CONDENSING
D D10–D11 FULL-SPEED, REHEAT, DOUBLE-FLOW
CONDENSING
G G1–G12 FULL-SPEED, REHEAT, FOUR-FLOW CONDENSING
Dense packs are used for the retrofits of these
machines
N N1 – N2 HALF-SPEED, TANDEM-COMPOUND SIX-FLOW
CONDENSING (only for Nuclear Application)
SC SC4-SC5 CONDENSING TURBINES
WITH NO CONTROLLED EXTRACTIONS OR
ADMISSIONS
REHEAT AND MULTIPLE-CASING, NON-REHEAT STEAM TURBINES A to N
SC Single casing Non reheat Steam Turbines

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Nuclear Vs Fossil Steam Turbines
Parameter Nuclear Fossil
Steam
parameters
Low pressure and saturated steam used
(60 -70 bar 250 to 280 Deg C)
HP Superheated with or
without reheat
(160 bar -540 Deg C)
Moisture
capture
provisions
1 or 2 stg. Moisture Separators and
re-heaters provided after HP casings
No Moisture separators are
employed due to superheated
steam
LP rotors Specially designed Mono-block LP
rotors ( This eliminates susceptibility to
fretting and loosening of shrunk-on
components )
-
Number of
HP/LP casings
One HP casing
Before LP stages ( 3 parallel stages)
HP + Reheat / IP stg
Before LP Stages
Bucket Design Aerodynamic Bucket design
To eliminate flow separation and reduce
losses and very long last stage buckets
Nuclear Vs Fossil Steam Turbines

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SC : CONDENSING TURBINES WITH NO
CONTROLLED EXTRACTIONS OR ADMISSIONS
1
15 1
6

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SC : CONDENSING TURBINES WITH NO
CONTROLLED EXTRACTIONS OR ADMISSIONS
1
15 1
6

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A : FULL SPEED, REHEAT, SINGLE
FLOW CONDENSING TURBINES
A14 Off-Shell Control Valves(s), Double-Shell High
Pressure Section With Reaction Staging, Generator on
High Pressure End, Sliding Support of Shell on Front
Standard.

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A : FULL SPEED, REHEAT, SINGLE
FLOW CONDENSING TURBINES
A15 Off-Shell Control Valves(s), Double-Shell High Pressure
Section With Reaction Staging, Generator on High Pressure End,
Sliding Support of Shell on Front Standard. Fixed Support of Shell
on Fixed Mid Standard, Sliding Low Pressure Exhaust Hood. For
Single-Shaft and Multi-Shaft Combined Cycle.

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D : FULL SPEED, REHEAT,
DOUBLE
FLOW CONDENSING TURBINESKW OUTPUT 293,597
FLOW (LB/HR) 1,922,040
PSIA 2414.4
°F 1000/1000
% MU 0.0
1 717 16 1 6

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D : FULL SPEED, REHEAT,
DOUBLE
FLOW CONDENSING TURBINESKW OUTPUT 293,597
FLOW (LB/HR) 1,922,040
PSIA 2414.4
°F 1000/1000
% MU 0.0
1 717 16 1 6

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G2 : FULL SPEED, REHEAT, FOUR FLOW
CONDENSING TURBINES ( HP + Reheat + LP-A +
LP–B )

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G3 : FULL SPEED, REHEAT, FOUR FLOW
CONDENSING TURBINES ( HP + Reheat + LP-A +
LP–B )

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N : FULL SPEED, NON REHEAT, SIX FLOW
CONDENSING TURBINES ( LP-A + LP–B + LP-
C)

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Thank you
STEAM TURBINE FUNDAMENTALS-
I