Gas Turbine project

Transcripción

Gas Turbine project

NITI
STUDY OF OPEN AND CLOSED CYCLES GAS TURBINE
‫ﺑﺴﻢ اﷲ اﻟﺮﺣﻤﻦ اﻟﺮﺣﻴﻢ‬
Republic of Yemen
Ministry of Technical Education & Vocational Training
NATIONAL INSTITUTE FOR TECHNICIANS AND INSTRUCTORS
NITI – ADEN
Maintenance of Oil Equipments Section
Study of
Open and Closed cycles Gas Turbine
A graduation project is submitted to the Maintenance of Oil Equipment
Section in partial fulfillment of the requirements for the degree of
Technical Diploma in Mechanical Engineering
BY
1. AHMED ABDU ALI ABDULLAH
(7/394)
2. WALEED MOHAMMED ABDU QAIED
(7/353)
3. ADNAN AHMED ALI MOHAMMED
(7/512)
4. MABROK SALEM AHMED AL-AQEELI
(7/172)
SUPERVISOR
ENGINEER /GAMAL ABDULKADER
MANSOOR ALI AL-IRAQI
Aden, Yemen
June/ 2009
MAINTENANCE OF OIL EQUIPMENT SECTION
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ACKNOWLEDGMENTS
First and formst, we would like to thank the head of or section, Eng. Yahia Sallam
Ali, for his support, outstanding guidance and encouragement throughout our
senior project.
We would also like to express or gratitude a appreciation to Eng. Gamal
abdulkader Ahmed Mansoor for all the help and guidance he provided throughout
our education, and to the other members of our instructor.
We would like to thank our family, especially our parents, for their
encouragement, patience, and assistance over the years. We are forever indebted to
our parents, who have always kept us in their prayers.
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ABSTRACT
Our project Title is “Study of open and closed cycle gas turbine” it consists of
three chapters.
Chapter one gives general prelusion about gas turbine through some definitions
about gas turbine and other prime movers. It also explains the principle of gas
turbine, and compares it with other prime movers (steam turbine, reciprocating
internal combustion engines). Finally the chapter classifies gas turbine.
In chapter two and chapter three you will find the core of our subject which
studies Open and Closed Cycle Gas Turbines from the following points:
• Maine components.
• Arrangements.
• Applications.
• Advantages and disadvantages.
• Conclusion
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TABLE OF CONTENTS
NO. Page
Title Page……………………………………………………………………………i
Acknowledgments…………………………………………………………………..ii
Abstract………………………………………………………………………….....iii
Table of contents………………………………………………………...…………iv
List of Figures…………………………………………………………………...…vi
List of Tables……………………………………………………………...……...viii
CHAPTER 1 (prelusion)………………..……………………………...1
1. Introduction ……………………………………………………………………...2
2. Definition…………………………………………………………………...…....3
3. Principle of Gas Turbine………………………………………………………....7
4. Gas Turbine versus other Prime Mover……………………………………….....9
4.1 Gas Turbine versus other reciprocating internal combustion engine……..….9
4.2 Gas Turbine versus steam turbine……………….....…………………….....11
5. Gas Turbine Classification……………………………………………...…...….13
CHAPTER 2 (Open Cycle Gas Turbine)………….…………......…..15
1. Open Cycle Gas Turbine (internal type)……………………………………......16
2. Main Component of Open Cycle Gas Turbine………………………………….18
2.1 Compressors………..…………………………………………………........18
2.2 Combustion Chamber……………………………………..………….……22
2.3 Turbine…………...………………..………………………………….……24
3. Open Cycle Gas Turbine arrangement…………………………………….……25
3.1 Open Cycle with single shaft arrangement………………..…………….….25
3.2 Open Cycle with two shaft arrangement…………………….…….…….….26
3.3 Intercooler single shaft Open Cycle ……………...…………………….…..27
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3.4 Reheating single shaft Open Cycle………………………………....………28
3.5 Regenerating single shaft Open Cycle………………………...……..……..29
3.6 Combined Inter cooler, Reheat and Regenerator open cycle……………….30
4. Application of Open Cycle Gas Turbine…………………………………...…..32
5. Advantages and disadvantages of open cycle gas turbine………….…………..38
CHAPTER 3 (Close Cycle Gas Turbine)…….....………….………… 40
1. Closed Cycle Gas Turbine (external type)…………………………...…………41
2. Main Component ……………………………...……………………………….42
2.1 heat exchanger…………………………………………………………...…42
3. Closed cycle gas turbine arrangements……………………...………………….49
3.1 Semi-closed cycle Gas Turbine……………………..………………..……….49
3.2 Single spool, intercooled, recuperated shaft power engine…...........................50
4. Advantages and disadvantages of closed cycle gas turbine…………...…...…...52
5. Application of Closed Cycle Gas Turbine………...……………………..……..53
6. Conclusions (differences)……………………………...…….…………………54
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LIST OF FIGURES
NO. Page
Figures 1.1 (a) Internal combustion type………………….…………………..……4
Figures 1.1 (b) External Combustion type.................................................................4
Figures 1.2 (a) Single-stage turbine………………………………………….….….5
Figures 1.2 (b) Multi-stage turbine……………………………………………..…..5
Figures (1.3) Steam turbine…………………………………………………...…….6
Figures (1.4) Reciprocating internal combustion engine…………………...………6
Figures 1.5 (a, b, c) Principle of work of gas turbine……………………………….8
Figures (1.6)Typical Jet Engine versus Four Strokes Internal Combustion
Engine………………………………………………………………………..…….10
Figures (2.1) Open cycle gas turbine…………………………………….....……..16
Figures (2.2) Main process………………………………….…………....………..17
Figures (2.3) Main component of Gas Turbine…………………………...……….17
Figures (2.4) Centrifugal compressor and Impeller…………………...…..………19
Figures (2.5)Multi stage centrifugal compressor………………….………………20
Figures (2.6) Axial flow compressor…………………………………...………...21
Figures (2.7) Annular Combustor………………………………………..………..23
Figures (2.8)Can annular combustor…………………………….………...………23
Figures ( 2.9)Can combustor……………………………………………..……....23
Figures (2.10)Turbine Section………………………………..………...………...24
Figures (2.11)Open cycle with single shaft arrangement………………...………..25
Figures (2.12)Open cycle with two shaft arrangements………….……..…………26
Figures (2.13) Intercooler single shaft open cycle gas turbine…………….……...27
Figures (2.14) Reheating single shaft open cycle gas turbine……………………..28
Figures (2.15)Regenerative single shaft gas turbine………………………….…...29
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Figures (2.16)Combined intercooler, reheat and regenerator open cycle gas
turbine…...................................................................................................................31
Figures (2.17)Air craft application………………………….…..…………………32
Figures (2.18) power generation application…………………………..……………34
Figures (25.19)Industrial application……………………………..…….…………35
Figures (2.20)Marine application…………………………….………….………...35
Figures (2.21) Marine application………………………………..……..…………36
Figures (2.22.a) Transportation application…………………...……………..……36
Figures (2.22.b) Transportation application…………...…………………..………37
Figures (2.22.c)Transportation application………….…..………………………...37
Figures (3.1)Closed cycle gas………………………………..……...…………….40
Figures (3.2)Sell and tube heat exchangers with baffles……………...…...............42
Figures (3.3) Actual footage of tube bundle………………………...…….............43
Figures (3.4)Actual footage of baffles arrangement……………………................44
Figures (3.5) Double pipe heat exchanger (one hair –pin)……….…….….............45
Figures (3.6)Acuale footage of 7 hair – pins arrangement ……………..................45
Figures (3.7)The core of a compact heat exchanger………………………............46
Figures (3.8) Two –fluid compact heat Exchanger With header removed……......46
Figures (3.9) Actual footage of cut – section in compact heat exchanger…...........47
Figures (3.10)plate and frame heat exchangers………………………...................48
Figures (3.11)Actual footage of plate and frame heat exchangers……..................48
Figures (3.12)Semi-closed cycle gas turbine……………………...………………50
Figures (3.13)Closed cycle single spool, intercooled, recuperated shaft power
engine.......................................................................................................................51
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LIST OF TABLES
Table (3.1) Sell and tube heat exchanger components…………………………….43
Table (3.2) Compact heat exchanger cross section………………………………..46
Table (3.3)Differences between open and closed cycles gas turbine…….……….55
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GLOSSARY
Abbreviation
Definition
WD
Work done
SSBB
'Suck, Squeeze, Bang, Blow'
C
Compressor
T
Turbine
HPT
High pressure turbine
LPT
Low pressure turbine
HPC
High pressure compressor
LPT
Low pressure turbine
SFC
Specific fuel consumption
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chapter (1)
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chapter (1)
1.1 Introduction:
There are many different types of turbines: wind, water, steam and gas.
A gas turbine uses a highly pressurized gas to rotate a turbine. The main fuel types used, are
hydrocarbons usually propane or kerosene. The fuel is mixed with air which combusts and
expands. This gas is accelerated through the turbine causes it to rotate, the power output achieved
can be used to generate electricity, if it is connected to an alternator.
Gas turbines are mainly known for their use in aircraft propulsion. Gas turbines are used as their
power to weight ratio is better than normal piston engines which used previously in aviation. Gas
turbines blades can achieve high rotation speeds and operate at extremely high temperatures; the
materials used for the blades are heat resistant. Although the function of the gas turbine is simple,
the manufacturing process is awkward and expensive. As the components in a gas turbine need to
accurate and carefully made. If manufactured incorrectly the components could be liable to
fatigue. However the manufacturing process is not the only expensive part, the fuel is a costly
expenditure. A reduction in fuel can be made by reducing the amount of after burn used. They
work best when they are constantly loaded hence there use in aircrafts.
The gas turbine takes in air, heats in with fuel, which provides an expanding gas. This gas is then
accelerated and produces a propulsive force. A standard gas turbine sucks air in through an inlet.
Then it travels through to a compressor, and then to the combustion chamber where fuel is burnt
with this compressed air, the mixture of gas and air expands and produces a high velocity gas.
The gas is then accelerated through the turbine which in turn produces the thrust.
Gas turbines have been developed for the simple purpose of producing power.
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1.2 Definitions:
1.2.1 A Turbine.
A turbine is a kind of spinning device that uses the action of a fluid to produce work. Typical
fluids used are: air, wind, water, steam and helium...
1.2.2 A gas turbine.
Gas turbine can be defined in many ways:
•
A gas turbine is a continuous combustion engine. The combustion process can
be internal or external Figure1.1 (a, b). It is similar to a jet engine in many respects,
however unlike the jet which has an exhaust nozzle to produce thrust, the gas turbine
produces torque, by utilizing a power turbine stage.
•
A heat engine which uses the energy of expanding gases passing through single or
multi-stage turbine to create rotational power Figure 1.2 (a, b).
1.2.3 A reciprocating internal combustion engine.
It is a heat engine that uses one or more reciprocating pistons to convert pressure into a
rotating motion. Figure (1.3) shows a reciprocating internal combustion engine.
1.2.4 A steam turbine.
A steam turbine is a mechanical device that extracts thermal energy from pressurized
steam, and converts it into rotary motion. Figure (1.4) shows steam turbine.
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Combustor
Turbine
Fuel
Shaft
Air
Load
Exhaust
Figure 1.1 (a) Internal Combustion
Heater
Turbine
Shaft
Load
Cooler
Figure 1.1 (b) External Combustion
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Figure 1.2 (a) Single-stage turbine
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High pressure compressor
High pressure turbine
Steam
Steam
Steam
Medium pressure turbine
Exhaust
Figure (1.3) Steam turbine
Figure (1.4) reciprocating internal combustion engine
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1.3 Principle of work of gas turbine:
As it is shown in figure (1.5, a) the compressor caused a flow of air at certain rate. Figure
(1.5, b) shows the effect of heat on increasing the flow rate of air. This happens due to the
increase in the movement of the molecules of air. The physical principle shown in figure.1.2 (a,b)
explains that the fluid used in gas turbines (usually air) passes through three main stages, as
shown in figure. (1.5, c):
•
First stage:
Fresh air at ambient conditions is exposed to compression process, where its pressure is
raised.
•
Second stage:
Combustion process is then takes place, where the compressed air and the fuel are burned
at constant pressure.
•
Third stage:
Expansion of the compressed hot air and the combustion gases are used to turn the
turbine. As a result of turbine rotation the driven equipment starts working.
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Compressor
W.D
fan
(a)
Compressor
W.D
fan
flam
(b)
(c)
Figures 1.5 (a, b, c) principle of work of gas turbine
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1.4 Gas turbine versus other prime movers:
Gas turbine is considered as a prime mover. Here we will compare gas turbine with two
famous prime movers:
1.4.1 Gas turbine versus reciprocating internal combustion engines:
A gas turbine in comparison with reciprocating internal combustion engine has all the
advantage a rotary engine has over a reciprocating engine, like:
•
Simple mechanism
•
Higher speed
•
Compact and low weight
•
Small foundation and easy balancing
•
Maintenance cost is low, about 60 percent that of a diesel engine.
The phenomenon of detonation, which limits the achievable maximum power out of a
reciprocating engine, does not exist in gas turbine that, thus, can use cheaper liquid fuels .the
main advantage
of gas turbine
is low full load thermal efficiency, and poorer part load
efficiency. It is a costly machine due to the use of high heat resistant materials and sophisticated
manufacturing processes for blade manufacture. The gas turbine is not a self-starting unit, so
requires a starting motor. It runs at comparatively high speed and requires a reduction gear for
normal industrial applications.
The gas turbine is slow in its response to acceleration.
Comparison of the operation of gas turbine (jet engine) versus
reciprocating internal combustion engine:
A jet engine works on the principle of Sir Isaac Newton's third law of physics, i.e. for every
action there is an equal and opposite re-action. The action of forcing gases out from the rear of
the jet engine results in a re-active force in the opposite direction, and is commonly referred to as
(thrust). Engines of this type are often referred to as 'Reaction Engines', a rocket engine being
another example. Newton's third law and the action of a jet can be demonstrated in simple terms
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by inflating a balloon and releasing it, the escaping air propels the balloon in the opposite
direction.
Creating thrust takes energy. The energy required is obtained from burning fuels, whether it
is in gas or liquid form such as propane, kerosene, diesel or even vegetable oils! This fuel is
normally combined with pressurized air to increase the efficiency and power output for a given
engine size. This fuel/air mixture is burned in some form of combustion chamber where the
resulting hot gases expand creating an increase in pressure inside the combustion chamber. The
expanding gases are then used to do useful work. One example of this process is what happens
inside the cylinder of a car engine. Air and fuel are drawn into the cylinder by the downward
movement of the piston, the piston then moves up and squeezes this mixture which is then
ignited. The fuel burns creating a sudden sharp rise in pressure inside the cylinder. This pressure
then forces the piston back down producing mechanical work. The piston then moves back up the
cylinder to eject the burnt fuel ready for another cycle. This process is commonly referred to as
the 'Suck, Squeeze, Bang, Blow' cycle! (SSBB).
Figure (1.6) a Typical Jet Engine versus Four Strokes Internal Combustion Engine
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The way a basic Turbojet engine burns it's fuel is exactly the same as in car engine, but
instead of burning the fuel in discrete packets, the jet engine continuously sucks, squeezes, bangs
and blows all at the same time! Also, instead of using the expanding gases to push on a piston,
they are released through the turbine blades which takes some of the energy to drive the
compressor, the rest being released to the atmosphere.
•
In a basic turbo jet, the air enters the front intake (suck) and is compressed by the
compressor (squeeze),
•
Then forced into combustion chambers where fuel is sprayed into them and the mixture
is ignited (bang).
•
The gases that are formed expand rapidly, and are exhausted through the rear of the
combustion chambers and out through the nozzle (blow).
The expanding gases provide the forward thrust. Just before the gases enter the engine nozzle,
they pass through a fan-like set of turbine blades which rotates the engine shaft. This shaft, in
turn, rotates the compressor, thereby bringing in a fresh supply of air through the intake. All of
these processes are happening at the same time. Engine thrust may be increased by the addition
of an afterburner section into which extra fuel is sprayed into the exhausting gases (which
contains surplus hot oxygen ) to give the added thrust.
1.4.2 Gas turbine versus steam turbine:
Steam turbine is a highly developed machine made in very large sizes up to 500MW with
efficiency of nearly 40 per cent. However, steam turbines have one inherent disadvantage. It
requires bulky and expensive steam generating equipment(boiler or nuclear reactor) and
condensing plant. The hot gases produced in the boiler furnace are not used directly in the turbine
but are used to an intermediate fluid, steam Gas turbines that use the products of combustion
directly are much more compact, require less maintenance, require less man power to operate and
can be quickly
started and stopped Another great advantage of simple open cycle gas turbine is
that it does not require any water for its operation.
The main disadvantage of gas turbine is its lower efficiency. Gas turbine is highly suited for
peak load and standby power generation and aircraft propulsion.
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Gas turbine has the following advantages over the steam, turbine:
• Its operation is simple and it can be quickly started.
• It is initial and maintenance costs are low.
• It requires few parts and their design is simple.
• It has low weight-power ratio.
• Its lubrication cost is low.
• Low capital cost.
• Lesser room and floor space requirement.
• Low maintenance and operating cost.
• Low or no cooling water requirement.
• No feed water supply is required.
• Reliable operation.
• Low power station auxiliaries.
• Fully automatic operation with possible remote control which stands for low
Operating staff costs.
• Economical waste heat utilization.
• It can be easily started from clod conditions.
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1.5 Gas Turbine Classification:
Gas turbine plants may be classified according to the following criteria:
1.5.1 Type of load:
(A) peak load plants.
(b) Stand by plants.
(c) Base load plants.
1.5.2 Application:
(a) Aircraft.
(b) Locomotive.
(c) Marine.
(d) Transport.
1.5.3 Number of shaft:
(a) Single-shaft.
(b) Multi-shaft.
1.5.4 Fuel:
(A) liquid.
(b)Solid.
(c)Gas.
1.5.5 Compressor:
(A)Axial compressor.
(B) Radial compressor.
1.5.6 Cycle:
(a) Open cycle plants:
• Open cycle with single shaft arrangements.
• Open cycle with two shafts arrangements.
• Intercooler single shaft open cycle gas turbine.
• Reheating single shaft open cycle gas turbine.
• Regenerative single shaft open cycle gas turbine.
• Combined intercooling, reheat and regenerator open cycle gas turbine.
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(b) Closed cycle plants:
• Semi closed cycle gas turbine.
• Closed cycle single spool, intercooled, recuperated shaft power engine:
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2.1 Open cycle gas turbine (internal type):
In open cycle gas turbine, the air is taken from the atmosphere and exhausted into the
atmosphere as shown in figure (2.1).
During its cycle it is passes through three main processes in order to produce energy or to do
work:
•
Compression process: This is happened in the compressor.
Air molecules are
compressed in the compressor, so that the maximum amount of energy carries
(molecules) can be used in minimum amount of space.
•
Combustion process: this is happened in the combustor. This process imparts heat
energy to the air molecules. Fuel is burnt inside the combustion chamber filled with
compressed air. Heated air and exhaust gas molecules expand rapidly through a series
of nozzle at the aft end of the combustion chamber.
•
Expansion process: hot gases expanding from each burner basket gradually merge into
an integral annular exit duct. This transition duct located between the combustion
chamber and the turbine nozzle gauid vanes insure the final mixing of hot gases. The
hot gases then expand into the turbine which generates power. This turbine is used for
generating electricity or for other purposes. The exhaust of the burnt gases takes place
in the atmosphere. The fresh air is again taken from the atmosphere and the processes
are repeated. The processes are shown in figure (2.2).
Fuel
Load
Fresh air
Exhaust gases
Figure (2.1) open cycle gas turbine
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Figure (2.2) Main process
Inlet
Compressor
Shaft
Burner
Turbine
Figure (2.3) Main components of Gas Turbine
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2.2 Main component of open cycle gas turbine:
Open cycle gas turbine consists of the three main parts as shown in the figure (2.3) in the
previous page.
•
Compressor
•
Combustion chamber (Burner).
•
Turbine.
2.2.1 Compressor:
Compressors used in gas turbines are air compressors. There are many type of air
compressors. In general gas turbines today use Centrifugal or axial flow compressors. Positive
displacement compressors are never used because of the high flow rate required of the air mass.
The Centrifugal Compressor:
Centrifugal compressor accelerates a gas by centrifugal force. The gas then passes
through a diffuser and a volute where a gas velocity decrease .As gas velocity decrease then
pressure increases. The centrifugal compressor consists of an impeller, a diffuser, and a volute
figure (2.4).The impeller is actually two plates of metal separated by curved blades. As the
impeller spins, air is pushed from the eye (center) to the outer edge. Since the outer edge is
moving at a faster velocity than the eye ,the air accelerates as it move outer the outwardly moving
air produces a low pressure area behind it ,causing more air to be drawn into the eye of the
impeller Fast moving gas is thrown into the diffuser ,which is narrow passageway encircling the
impeller. Since the impeller blades are no longer acting on the air ,the air losses velocity .the
impeller however continue to eject high velocity air from the impeller blades .These air molecule
crowed into the slower moving molecules in the diffuser .The air being to compress .Air passes
from the diffuser into the volute .The spiral shape of the volute allows the air to expand ,further
reducing its velocity .The impeller continue to expel high velocity air ,which crowds into the
slower moving air in the diffuser and the volute .As air exits the volute, it is compressed. If
compressed air exiting the volute was fed into the eye of the second centrifugal compressor, the
result would be much higher air compression. Several impellers are mounted on the same shaft
constitute a multistage centrifugal compressor as shown in figure (2.5).
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The compressed discharge air from each impeller, or stage, enters the eye of the next impeller, air
compression increase with each succeeding stage.
The multistage centrifugal compressor is capable of producing high pressure air for moderate gas
stage power out put .Its efficiency ,however, is considerably lower than axial flow compressor
.For this reason ,the axial flow compressor is normally preferred.
Figure (2.4) Centrifugal compressor and impeller
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Diffuser
Impellers
Figure (2.5) Multi stage centrifugal compressor
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The Axial Flow compressor:
The axial flow compressor consist of a series of metal disc fixed to a single shaft
figure (2.6).The rim of each disc hold s a set of contoured blades, mounted at an angle .As the
shaft rotates, air is pushed along by the angle blades .These rotors behave like a series of fans,
pushing air along the axis of the compressor, hence, the name axial flow series of rotors spinning
along a shaft would generate a lot of wind, but the air still would not be compressed as it moves
axially along the flow path. Compressions accomplished by slightly reducing the velocity of the
air between each rotor disc, thereby building pressure between each rotor hangs a set of vanes
these vanes are fixed to the inner wall of the compressor casing and therefore do not spin with the
rotors since the vanes are stationary they called stator. The stator are angled to diffuse the air that
passes between them .Air entering the compressor inlet is pushed along by the first stage rotor.
This rotor imparts both velocity and pressure to the air. As the air flows into the first stage stator,
however continues to push air into the first stage rotor, thereby building pressure. The slightly
pressurized air is then picked up by the second stage rotor, and the velocity –pressurization cycle
occurs again an axial compressor may contain up to twenty stages, each stage imparting greater
air compression than the one before. Large axial flow compressor are designed to deliver highly
compressed air .The degree to which a compressor can deliver compressed air is expressed as its
ratio of compression. The ratio of compression is the amount of discharge pressure pound per
square inch (psi) of suction pressure .Some turbine applications required a compression ratio of
20 – psi discharge pressure for every 1 –psi suction pressure. This can be expressed simply as
20:1 .Under normal operating conditions, the axial –flow compressor will discharge air from 70
to 100 psi .Before entering the combustion chamber, the compressed air passes through the
diffuser assembly to slow it down .Remember, the air must be compressed .but it doesn't require
velocity as it enters the combustion chamber .Heat from the combustion burner will impart the
necessary velocity to turn the turbine.
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Stator
Rotor
(2.6) axial flow compressor
2.2.2 combustionFigure
chamber:
The combustion chamber receives air from the compressor which mixes with fuel
sprayed from nozzles in the front of the chamber. The mixture is burned at temperatures up to
2000C‫؛‬combustion chamber to generate the maximum possible heat energy. The burning process
is initiated by igniter plugs, isolated after start-up, and remains continuous until the fuel.
There are three types of combustors:
Annular combustor:
It consists of four concentric casing , the middle annular space is used to burn the fuel and called
flame tube, the outer spaces are used to pass air to cool the middle casing wall, figure (2.7 ) show
an actual annular combustor in which ten fuel injectors are mounted on bosses around the
combustor housing .The combustor housing incorporate a flange for mounting the bleed air valve.
Cannular Combustor:
It consists of number of cans distributed radially around longitudinal axis of the engine
and fixed together with interconnection surrounded by one casing for cooling air .fuel mixture is
burned inside the tubes and the outer air flow is used to cool flame tubes wall. Shown in figure
(2.8).
Can Combustor (separate flame tube combustor):
It is similar to cannular combustor but every tube has its own casing for cooling figure (2.9) this
type is the most frequently used .Such multiple combustor system require more elaborate fuel
and air distribution system than those using a single combustor ,but are more compact. Less
costly erect, and possess greater flexibility than systems using a single combustion chamber.
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Axial view
Side view
Figure (2.7) Annular
Side view
Axial view
Figure (2.8) Can annular combustor
Figure (2.9) Can combustor
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2.2.3 Turbine:
The turbine extracts energy from the exhaust gas. The turbine - like the compressor- can be
centrifugal or axial. In each type the fast moving exhaust gas is used to spin the turbine. Since the
turbine is attached to the same shaft as the compressor at the front of the engine the turbine and
compressor will turn together. The turbine may extract just enough energy to turn the
compressor. The rest of the exhaust gas is left to exit the rear of the engine to provide thrust as in
a pure jet engine. Or extra turbine stages may be used to turn other shafts to power other
machinery such as the rotors of a helicopter, the propellers of a ship or electrical generators in
power stations, as shown in figure (2.10)
Figure (2.10) Turbine Section
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2.3 Open cycle gas turbine arrangements:
The engine arrangements described below are all open cycle in that air is drawn from the
atmosphere, and only passes through the engine once. This arrangements work
To improve the cycle efficiency concentrated by. Adding modifications to the basic cycle such
as incorporating intercooling, regeneration, and reheating techniques.
2.3.1 Open cycle with single-shaft arrangement:
Single shaft arrangement the compressor and the turbine are directly coupled by single shaft
to the load. This has inferior flexibility characteristic. Any change in speed will change the speed
of compressor and the efficiency of the compressor will decrease due to air angle being different
than designed. There is also starting difficult. Gas turbine plant are not self- starting and must be
run about 30-40 percent of their normal speed before they develop sufficient power to maintain
the speed .this arrangement require a large motor to accelerate the shaft. Figure (2.11) show the
schematic diagram of in open cycle
The cost with single shaft arrangement is low. This type of arrangement is used for constant
speed operation and for application where the load is usually near to full load. At part loads the
efficiency of the plant is poor
Combustion chamber
Propulsion Power Coupling
Generator
Atmospheric air intake
Exhaust to atmospheric
Figure (2.11) Open cycle with single shaft arrangement
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2.3.2 Open cycle with two-shaft arrangement:
It consists of two turbines and a compressor. One turbine is coupled to the compressor and
the second to the load .this arrangement is also known as free turbine arrangement. The two
turbine shafts are mechanically independent and can run at Different speed. Another possible
arrangement is the use of two concentric shafts to couple compressor and one turbine by one
shaft, and another turbine and the load by another shaft. The two shaft arrangement is more
efficient than single shaft arrangement because one turbine coupled to the compressor can be run
at higher speed compatible to high compressor efficiency the power supply is controlled by
changing the amount of fuel supplied to the combustion chamber. However,
such a control has to main disadvantages: (I) the amount of flow changes with the fuel supply and
results in changing compressor speed .this reduce the efficiency of the compressor as air angles
are now not optimum. (II) The maximum temperature of the cycle is also lowered due to
improper fuel –air matching, resulting in a loss of efficiency. Figure (2.12) shows the schematic
arrangement of a two shaft turbine plant
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Figure (2.12) Open cycle with two shaft arrangements
2.3.3 Intercooler single shaft open cycle:
The air from low pressure compressor (L.P.C) flows to the inter cooler and then to high
pressure compressor. The pressure may be developed by two or more stage compressor. The
compressed air after delivery from first compressor is allowed to cool thus reducing in volume at
constant pressure. The cooled air then enters the high pressure compressor which then delivers air
to the combustor. The intercooling of the compressed air is done by circulating water which can
be cooled gain and again. Figure (2.13) shows an arrangement with intercooler.
Figure (2.13) Intercooler single shaft open
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2.3.4 Reheating single shaft open cycle gas turbine:
Open cycle gas turbine may be having a process of reheating by providing an auxiliary
combustion chamber and of course two turbines will have to be provided. The expansion of gases
is carried out in two or more turbines. These may be called as high pressure turbine and low
pressure turbine. In case of three stages, they may be termed as high pressure turbine,
intermediate pressure and low pressure turbines.
The gas in case of two stage turbine may be reheated in an auxiliary combustion chamber to
the maximum temperature.
Figure (2.14) shows an open cycle gas turbine with reheat.
Combustion Chamber
H.P.T
Air
l.P.T
Generator
To atmosphere
Auxiliary CC
Figure (2.14) Reheating single shaft open cycle gas turbine
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2.3.5 Regenerative single shaft open cycle gas turbine:
In this system the heat energy transfer from the exhaust gases to compressed air flowing
between the compressor and the combustion chamber. A surface heater called the regenerator is
required. This will result in cooler final exhaust gases which Results sin the reduction of waste
heat. Figure (2.15) shows the arrangement of the gas turbine with regenerator. The exhaust gas of
the turbine gives its heat to the compressed air when it passes through the regenerator. The
temperature fall of the gas is approximately equal to the temperature raise of the air. The pressure
losses in the regenerator are small. The addition of the heat to the air increases the efficiency of
the plant.
Gen.
C
T
Regenerator
Figure (2.15) Regenerative single shaft open cycle gas turbine
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2.3.6 Combined Intercooler, Reheat and Regenerator open cycle gas turbine:
Figure. (2.16) shows a typical gas turbine plant working on open cycle using intercooling, reheat
and regenerator. Air enters from the atmosphere into the low pressure air compressor from where
the compressed air is cooled to its original temperature. This cooling of air is done in an
intercooler. The cooled air at pressure then enters the high pressure air compressor where its
pressure is raised further. This high pressure air then passes through the regenerator where the
exhaust gases heat this air. The high pressure and hot air then enter the combustor where the fuel
burns and gases are formed. These gases are then allowed to expand in the high pressure turbine.
During the expansion, the pressure and the temperature of the gases drop down. These gases
which even now have sufficient air enter the auxiliary combustor so that the temperature of the
gases increases due to brining of fuel. This heating of gas takes place at low pressure. The hot
gases at low pressure then enter the low pressure turbine. The exhaust gases then finally enter the
regenerator to heat the incoming air. The exhaust gases then pass out in the atmosphere as it is an
open cycle. The intercooler is water cooled surface heat exchanger and a continuous supply of
water which could be used again and again is required. These turbine and air compressor are all
mounted on the same shaft. An electric generator
also mounted on the same shaft gets power for generator of electricity. An electric motor is
provided to start the turbine. A part of power generated by the turbine is utilized in driving the
compressor. All these improvements in a gas turbine plant raise the plant efficiency to over 30
per cent. This will result in more power per unit of flow at greater efficiency. The intercoolers
and regenerators are of shell and tube construction. Because of the low coefficient of transfer in
gas to gas transfer, the regenerator will tend to become bulky on account of large surface
involved. Generally the gas is allowed to pass through the tubes or air surrounds them. In such
cases the shell must be cylindrical to withstand air pressure. This arrangement enables the gas
side to be cleaned easily. If the compressed air is passed through the tubes and gases surrounding
them then the shell is not stressed and its shape may be oval, rectangular and so on. In the case of
open cycle turbine, the plant can have a single shaft as described above or may have twin shafts
or multiple shafts.
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In case of a twin shaft, the gas from one turbine enters the second turbine which is mounted on
other shaft. In some case the generator is mounted on other shaft and the first turbine runs the
compressor only. In some case both the shafts carry generators.
Generator
Inter Cooler
Regenerator
Combustor
Auxiliary combustor
To atmosphere
Figure (2.16) Combined intercooler, reheat and regenerator open cycle gas turbine.
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2.4 Applications of open cycle gas turbine:
People have been harnessing the power of flowing gases for thousands of years with
windmills. The first modern gas turbine was built 100 years ago, but in the last 50 years the
technology has been dramatically improved.
2.4.1 Aircraft (Jet Engine):
This is probably the most familiar example of the modern gas turbine.
Gas turbines have made a big impact on aircraft design. The gas turbine engine has almost
completely replaced the reciprocating engine for aircraft propulsion. as shown in figure (2.17)
Jet engines derive thrust by ejecting the products of combustion in a jet. In simplest terms, a
jet engine ingests air, heats it, and ejects it at high speed.
Because its basic design employs rotating rather than reciprocating parts, a jet engine is far
simpler than a reciprocating engine of equivalent power, weighs less, is more reliable, requires
less maintenance, and has a far greater potential for generating power. It does, however,
consumes fuel at a faster rate. Some of the specific aeronautical variations on the simplest gas
turbine are: turbofan, turboprop, prop fan, rocket, ramjet and scramjet.
Figure (2.17) Air craft application
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2.4.2 Power Generation:
When you’re talking about burning a liquid or gaseous fuel to generate electricity, gas turbines
are the prime mover of choice.
At sufficiently large sizes, gas turbines are cheaper, lighter and more efficient than steam
turbines or engines. as shown in figure (2.18)
Furthermore, they require less space and can be quickly brought into operation. They do not
require elaborate foundations and can be dropped on a simple concrete pad. In a matter of weeks,
a gas turbine can be delivered, hooked up to the grid and a fuel source, and be in operation.
On a day-to-day basis, gas turbines can be started and operational in a matter of minutes,
whereas steam turbines (and their associated equipment) can take hours to start-up. For these
reasons, gas turbines have found a niche in the medium sized, ‘peak’ generating stations – power
plants that are turned on and operated intermittently during periods of high demand.
2.4.3 Industrial Uses:
Gas turbines can be found in a number of industrial processes.
One of the more common applications is driving the compressors used on natural gas pipelines.
These units are often automated so that only occasional on-site supervision is required,l as shown
in figure (2.19)
Small portable gas turbines with centrifugal compressors have also been used to operate pumps.
They can be found in oil refineries as part of the Houdry process (where pressurized air, passing
over a catalyst burns off accumulated carbon).
2.4.4 Marine Applications:
Because gas turbines can deliver a lot of power (up to 20,000 horsepower) while remaining
lightweight and compact, they have been incorporated into the designs of many types of ships by
the world’s navies. They are also used in merchant ships. as shown in figure (2.20),(2.21).
2.4.5 Transportation:
Gas turbines have been tested in locomotives and automobiles. In spite of their small size and
weight compared to their power output, they have not been wildly successful because
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Figure (2.18) power generation application
They are inefficient at partial loads (or idling), and have low thermal efficiencies
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Figure (2.19) Industrial application
Figure (2.20) Marine application
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Figure (2.21) Marine application
Figure (2.22.a) transportation application
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Figure (2.22.b) transportation application
Figure (2.22.c) transportation application
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2.5 Advantages and disadvantages of open cycle gas turbine:
2.5.1 The advantage:
Simplicity. The combustion chamber is lighter in weight and smaller in size with
high rate of heat release. Secondly the ignition system is simple only a spark is
required for a short period to start the burning after which the combustion continues.
The combustion chamber may be designed to burn almost any of the hydrocarbon
fuel ranging from gasoline to heavy diesel oil including solid fuels.
Vibration less. In this system the moving or rotating parts being the rotor
(consisting of turbine and compressor connected by a shift) and the gear trains that
drive the other auxiliaries. There being no unbalanced forces the engine is vibration
less.
Cooling water. Cooling water is not needed except in those turbines using intercooler.
Law weight and size. In this cycle the turbine has a lower specific weight and
requires lesser space per horse power output. (Specific weight is the weight of engine
per H.P.output) this property of producing more power output in a small space and
low weight is quite useful in aviation engines.
Warm up period. The warm up period of the engine is negligible because after
the engine has been brought up to the speed by starting motor and fuel ignited the
engine then can accelerate from the clod start to a full load without warm up time.
This property is quite advantageous in marine, aviation.
2.5.2 Disadvantages:
Part load performance is low. This can be improved by using inter-cooler and
reheater.
Reduction in component efficiencies lowers the thermal efficiency of the cycle.
The gas turbine in open cycle requires a large quantity of air.
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3.1 Closed cycle gas turbine: (External type):
In a closed cycle gas turbine facility the working fluid (air or other gas) is continuously
recycled by cooling the exhaust air through a heat exchanger (shown schematically in
Figure (3.1 ) and directing it back to the Compressor inlet.
Because of its confined, fixed amount of gas, the closed cycle gas turbine is not an internal
combustion engine. In the closed cycle system, combustion cannot be sustained and the normal
combustor is replaced with a second heat exchanger to heat the compressed air before it enters
the turbine. The heat is supplied by an external source such as a nuclear reactor, the fluidized bed
of a coal combustion process, or some other heat source.
Figure (3.1) closed cycle gas turbine
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3.2 Main components of closed cycle gas turbine:
Closed cycle gas turbine has the same components for open cycle gas turbine, but its
combustion chamber is an outside one (burner or boiler) which is connected to a heat exchanger
which acts as a heater for the fluid used. In addition to that components closed cycle gas turbine
requires another heat exchanger a cooler for the fluid used.
3.2.1 heat exchangers:
A heat exchanger is a device that is used for transfer of thermal energy between two or more
fluid, between a solid surface and a fluid, or between solid particulates and a fluid, at differing
temperatures and in thermal contact, usually without external heat and work interactions. The
fluids may be single compounds or mixtures. Typical applications involved heating or cooling of
a fluid stream of concern, evaporation or condensation of a signal or multi component fluid
stream, and heat recovery or heat rejection from a system. In other applications, the objective
may be two sterilize, pasteurize, fractionate, distill, concentrate, crystallize, or control process
fluid. In some heat exchangers, the fluid exchanging heats are in direct contact. In other heat
exchangers, heat transfer between fluids takes place from a separating wall or into and out of a
wall in transient manner.
In most heat exchanger the fluid are separated by a heat exchanger transfer surface and ideally
they do not mix / such exchanger is referred to as the direct transfer type or simply
recuperators. In contrast, exchanger in which there is in intermittent heat exchanger between
the hot and the cold fluids via thermal energy storage and rejection through the exchanger
surface or matrix –are referred to as the indirect transfer type or storage type or simply
regenerators.
Such exchanger usually have leakage and fluid carryover from one stream to the another.
Heat exchanger may be classified according to the transfer, construction, flow arrangement,
surface compactness, and number of fluid and heat transfer mechanism or according to the
process function:
•
Shell and tube heat exchanger.
•
Double pipe heat exchanger.
•
Compact heat exchanger.
•
Plate and frame heat exchanger.
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tube heat exchanger Shell and:
Heat and tube heat exchangers are fabricated with around tubes mounted in cylindrical shells
with their axes coaxial with the shell axis. The differences between many variations of this basic
type of heat exchanger lie mainly in their construction features and the provisions made from
handling differential thermal expansion between tubes and shell.
There are various design considerations to be taken into account such as routing of fluids
(shell or tube),pressure drop specially in the case of increasing number of baffles and tube
diameter and adjusting the area with the suitability of the exchanger to conduct the heat required
to heat or cool a fluid with anther one .
Applications:
They are extensively used as process heat exchanger in the petroleum –refining and chemical
industries ; as steam generator ,condensers , boiler feed water heater and oil coolers in power
plant ; as condensers and evaporator is some air –conditioning and refrigeration application in
wast heat recovery application with heat recovery from liquids and condensing fluid ; and in
environmental control.
Figure (3.2) Actual footage of tube bundle
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Fig (3.3) Shell and tube heat exchangers with baffles
1-Shell.
8-Floating head flange.
15-Transevers baffles.
9-Channel partition.
16-Impingment baffle.
3-Shell channel.
10-Stationary tube sheet.
17-Vent connection.
4-Shell cover and flange.
11-Channel.
18-Drain connection.
5-Shell nozzle.
12-Channel cover.
19-Test connection.
13-Channel nozzle.
20-Support saddles.
7-Floating head.
14-Tie rodes and spacers. 21-Lifting ring.
Table (3.1) Sell and tube heat exchanger components
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Figure (3.4) Actual footage of baffles arrangement
Double pipe heat exchanger:
Atypical Double pipe heat exchanger is shown figure (3.5) essentially it constant of one pipe
placed concentrically inside another one of large diameter with appropriate end fitting one each
pipe to guide the fluids from one section to the next .the inner pipe have external longitudinal
fines welded to it either internally or externally to increase the heat transfer area for the fluids
with the lower heat transfer coefficient. The double pipe section can be connected in various
series or parallel arrangement for either fluid to meet pressure – drop limitations and LMTD
requirements.
The applications:
The major of double-pipe exchangers is for sensible heating or cooling of the process fluid
where small heat transfer areas (typically up to 50m) are required. They may also be used for
small amounts of boiling or condensation on the process fluid side. The advantages of doublepipe exchanger are largely in the flexibility of application and piping arrangement, plus the fact
that they can be erected quickly from standard components by maintenance crews.
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.
Figure (3.5) Double pipe heat exchanger (one hair –pin)
Figure(3.6 ) Acuale footage of 7 hair – pins arrangement .
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Compact heat exchanger:
One variation of fundamental compact exchanger element, is shown in figure (3.7) .the core
consist of a pair of parallel plates with connecting metal members that are bounded to the plates.
The arrangement of plates and bounded members provides both a fluid- flow channel and prime
and extended surface. It is observed that if a plane where drown midway between the two plats,
each half of the connecting metal members could be considered as longitudinal fins.
Compact heat exchangers may be classified by the kinds of compact element that they
employ. The compact elements usually fall into five classes:
•
Circular and flattened circular tubes.
•
Tubular surfaces.
•
Surfaces with flow normal to banks of smooth tubes.
•
plates fin surfaces
•
Finned-tube surfaces.
Figure (3.7) the core of a compact
heat exchanger
Figure (3.8 ) two –fluid compact heat
Exchanger With header removed
1-Plates.
2-Side bars.
3-Corrugated fines stamped from strip of metal.
Table (3.2) compact heat exchanger cross section
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Figure (3.9) Actual footage of cut – section in compact heat exchanger
Applications:
Compact or plat- fin heat exchangers have wide range of applications that include:
•
Natural gas liquefaction.
•
Cryogenic air separation.
•
Ammonia production.
•
Offshore processing.
•
Nuclear engineering.
•
Syngas production.
Plate and frame heat exchanger:
These exchangers are usually built of thin plates (all prime surfaces) the plates are either
smooth or have some form of corrugations , and they are either flat or wound in an exchanger
.generally this exchangers can not accommodate very high pressures ,temperatures , and pressure
and temperature differentials .these exchangers may be further classified as plate , spiral plate
lamella, and plate coil exchangers as shown in figure (3.10) the plate heat exchanger, being the
most important .
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Figure (3.10) plate and frame heat exchangers
Figure (3.11) Actual footage of plate and frame heat exchangers
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Applications:
These exchangers are relatively compact and light Weight heat transfer surfaces, making
theme attractive for used in confined or weight sensitive such as on board ships and oil
production plat forms. Pressures and temperatures are limited to comparatively low values
because of the gasket materials and constructions. They are typically used for exchanging heat
between two liquid streams in turbulent flow. They are occasionally used as condensers for fairly
dense vapors (e.g. ammonia) or as vaporizers as for a reboiler. They are used in food processing
industry because thy can be disassembled for cleaning and sterilization.
3.4 Closed cycle gas turbine arrangement:
3.4.1 Semi-closed cycle gas turbine:
The system is shown in figure (3.12).this system is combustion of open cycle and closed. The
air enters the low pressure compressor (L.P.C.)
and than flows through pre-cooler where its temperature is lower. Than it's compressed in high
pressure compressor (H.P.C.) and after that it is heated in combustion chamber. Its than expands
in the turbine ( T1 ) and some amount of gases heaving this turbine is expanded in turbine ( T2
)which drives the low pressure compressor (L.P.C.) portion of gases is cooled in the pre-cooler
.in this system the heat exchanger has been omitted for simplicity.
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L.P.C
T2
Cooling water
H.P.C
T1
Combustion chamber
Figure (3.12) Semi-closed cycle gas turbine:
3.4.2 Single spool, intercooled, recuperated shaft power engine:
In closed cycle configuration the working fluid is continuously recalculated. It may be air or
another gas such as helium. Usually the gas turbine is of intercooled recuperated configuration, as
shown in figure (3.13 ).however the combustor is replaced by a heat exchanger as fuel cannot be
directly. the heat source for the cycle may be a separate combustor burning normally unsuitable
fuels such as coal, a nuclear reactor,etc. on leaving the recuperator, the working fluid must pass
through a pre-cooler where heat is rejected to an external medium such as sea water to return it to
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the fixed inlet temperature, usually between 15C° and 30C°. The pressure at inlet to the gas
turbine is maintained against leakage from the system by an auxiliary compressor supplying large
storage tank called an accumulator.
The high density of the working fluid at engine entry enables a very high power output for a
given size of plant, which is the main benefit of the closed cycle. Pressure at inlet to the gas
turbine would typically be around twenty times atmospheric. In addition, varying the pressure
level allows power regulation without changing specific fuel consumption (SFC).
Up tank
Pre-cooler
Recuperator
Combustor, heat
exchanger
Compressor,
L.P, H.P
Intercooler
Turbine
Exhaust
diffuser
Load
Auxiliary compressor
Figure (3.13) Closed cycle single spool, intercooled, recurperated shaft power engine
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3.5 Advantages and disadvantages of closed cycle gas turbine:
3.5.1 The advantage:
Since the pressure of working fluid is independent of atmospheric pressure, a higher
pressure can be used to increase the specific output of the plant. This results in
diminution of the sizes of the components both for the machines and the heat transfer
apparatus used.
Gases other than air, which have more favorable properties can be used .Helium or
helium-carbon dioxide mixture gives higher efficiencies and smaller dimensions for
special purposes. The properties of helium at high pressure, such as high heat transfer,
low pressure drop, high sound velocity and neutrality towards radioactive materials
makes it possible to build smaller heat transfer equipment and is highly suitable for
nuclear plants.
Use of alternative working fluids such as helium, etc, gives rise to the possibility of
using alternative materials as no oxidation occurs with these inert gases.
The power output of a closed cycle gas turbine can be controlled by changing the mass
flow. The system pressure is proportional to the gas mass flow. By changing the
pressure and mass flow, output changes but the temperatures drop remains the same.
Constant temperatures lead to constant heat drop and constant velocities in the turbine
balding and hence the velocity triangles and consequently the turbine and compressor
efficiencies remain constant for every power control is affected by controlling
temperature which affects the efficiency of the turbine at part load.
Existence of constant temperature at all load results in low thermal stresses.
Due to the fact that the working fluid does not come in contact with products of nuclear
can be used.
In total energy plants direct waste heat utilization at a high temperatures for heating
purposes, without affecting power cycle efficiency, can be affected because heat
rejection is an isobaric process instead of isothermal change of state i.e. condensation.
The turbine blades are not fouled by the products of combustion.
The regulation of the closed cycle gas turbine is simpler.
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3.5.2 The Disadvantages:
The use of high pressure required a strong heat exchanger.
Since heat transfer is indirect, a part of the heat energy is lost in radiation and other
losses resulting in power combustion efficiency.
Due to use of air heaters and precooler the cost and bulk of a closed cycle gas turbine
plant is much more than that for an open cycle gas turbine plant.
A coolant is needed for precooler which is a disadvantage as compared to an open
cycle plant.
3.6 Applications of closed cycle gas turbine:
The closed cycle gas turbine used in power generation to produce electrical power .it was a
standby unit with a thermal efficiency.
Another application involves energy sources unsuited to direct combustion within a gas
turbine engine, such as nuclear reactors or alternative fuels. The working fluid is normally
helium.
A Closed cycle gas turbine have been manufactured despite numerous studies for power
generation and submarine propulsion.
Also closed cycle gas turbine engine is used to drive a pump or compressor.
Simple closed cycle gas turbine is used as Standby generator in Office block
Hospital.
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3.7 Conclusions (Differences):
The fundamental difference between open and closed cycle gas turbines is in the method of
heating the air after compression. In case of an open cycle turbine the fuel is burned in the air
itself to raise it to a high temperature and then products of combustion are passed on to the
turbine for expansion and which after delivering the work are finally rejected to the atmosphere.
For next cycle a fresh supply of air is sucked in the compressor. In case of closed cycle turbine on
the other hand. The sane air or the working fluid is circulated over and over again. The working
fluid is heated by burning the fuel in a separate supply of air in a combustion chamber and
transferring this heat to the working fluid which passes through tubes fitted in this chamber. Thus
the working fluid does not come contact with the products of combustion.
Advantages of a closed, as opposed to open, cycle include the following.
•
No inlet filtration requirements, or blade erosion problems.
•
Reduced turbo machinery size, due to the working fluid being maintained at a high
pressure and density. In addition, helium offers a high specific heat.
•
The use of energy sources unsuited to combustion within an open gas turbine cycle, such
as nuclear reactors or alternative fuels such as wood and coal. Helium offers a short half
life for use in radioactive environments.
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Differences
Closed
cycle
Open cycle
1. Gas turbine
helium
air
2. Gas turbine
new
design
adapted existing gas turbine
3. Generator
helium
cooled
air cooled
4. Heat dump in cycle
yes
open air
5. Intermediate Heat
Exchanger
no
yes
6. Control of the installation
mass flow mass flow
7. Efficiency calculated by
30 °C
15 °C
8. Efficiency
higher
lower due to pressure losses
9. Efficiency
at 15 °C comparable
10. Pressure
losses comparable
11. Magnetic bearings
compulsor
Advisable
y
12. Amount of helium
more
Less
13. Number of rotating seals
none
at least one (helium ventilator)
14. Inlet air
only
for
cooling for GT and reactor cooling
reactor
15.
reactor
cooling
Funnel arrangements
reactor cooling and GT outlet, but
no gaseous emissions
16. Starting
using
using existing starting system
generator
17. Response to power changes
Comparable
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18.Weight total installation
19. Volume total installation
20. Vibrations
Comparable
Comparable
Comparable
Table (3.3) differences between open and closed cycles gas turbine
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REFERENCES
[1] Thermal Power Engineering.
[2] Power plants.
[3Fundamental and principle of gas turbine.
[4] Gas turbine and jet and rocket propulsion.
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Gas Turbine project

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