Final report

1
Sri Pavan Teja Tatini
PRE-FINAL YEAR | MECHANICAL ENGINEERING
Report on Industrial Training
GAS TURBO POWER STATION

REPORT ON
INDUSTRIAL TRAINING
AT
GAS TURBO POWER STATION
VIJJESWARAM
Submitted by
Tatini Sri Pavan Teja
2014193
Department of Mechanical Engineering

ACKNOWLEDGEMENT
It is always a pleasure to remind the fine people in the Engineering program
for their sincere guidance I received to uphold my practical as well as
theoretical skills in engineering.
Firstly I would like to thank Dr. Prashant K Jain (HoD Mechanical
Engineering) for meticulously planning academic curriculum in such a way
that students are not only academically sound but also industry ready by
including such industrial training patterns.
I express my immense pleasure and deep sense of gratitude to
Shri M.Chitti Babu, General Manager (APGPCL, Vijjeswaram) for giving
me this valuable opportunity to undergo industrial training in GTPS to
enhance my theoretical knowledge and Shri Ch. N Pulleswara Rao,
Manager (Mechanical Department, OMS)for guiding me through out the
length of the training
Finally, I would also like to thank all the staff of operations, mechanical and
I&C departments for their encouragement and support during the course of
the training.
Sri Pavan Teja Tatini
Pre-Final Year
Mechanical Engineering

Sri Pavan teja Tatini 1
CONTENTS
1. Introduction
1.1 Electricity and India
1.2 A brief introduction about GTPS
2. Electricity Production through gas
2.1 Simple Cycle
2.2 Combined power Cycle
2.3 Components of a Combined Cycle Power Plant
3. Gas Turbines
3.1 Introduction
3.2 Components of Gas Turbines
3.3 Simple Gas Turbine
3.4 Classification of Gas Turbines
3.5 Factors effecting performance
3.6 Performance Enhancement
3.7 Performance Degradation
3.8 Advantages
3.9 Gas Turbines At GTPS
4. Heat Recovery Steam Generator
4.1 Introduction
4.2 Classification
4.3 Components
5. Steam Turbines
5.1 Introduction
5.2 Components

Sri Pavan teja Tatini 2
1. INTRODUCTION
1.1 Electricity and India
The utility electricity sector in India had an installed capacity of 303
GW as of 31 May 2016. Renewable Power plants constituted 28% of total
installed capacity and Non-Renewable Power Plants constituted the
remaining 72%. The gross electricity generated by utilities is 1,106
TWh(1,106,000 GWh) and 166 TWh by captive power plants during the
2014–15 fiscal. The gross electricity generation includes auxiliary power
consumption of power generation plants. India became the world's third
largest producer of electricity in the year 2013 with 4.8% global share in
electricity generation surpassing Japan and Russia.
During the year 2014-15, the per capita electricity generation in India was
1,010 kWh with total electricity consumption (utilities and non utilities) of
938.823 billion or 746 kWh per capita electricity consumption.Electric
energy consumption in agriculture was recorded highest(18.45%) in 2014-15
among all countries.The per capita electricity consumption is lower
compared to many countries despite cheaper electricity tariff in India
The most serious issue India must address is that the gap between energy
demand and energy supply is wide and growing. Two reasons for this trend
are demographics and economics: not only is India’s economy growing,
thereby demanding more energy and electricity, but the population is as well.
There is also massive urbanization, which is putting more pressure on energy
and the environment.
India’s power network comprises five regions spanning the country. While
each is connected with a neighboring region, there are inadequate inter-
regional connections through high voltage transmission lines, creating

Sri Pavan teja Tatini
3
difficulties for moving power from electricity surplus states to those in
deficit. This also creates difficulties on a seasonal basis, as power is often in
short supply during the dry season and abundant in some regions during the
monsoon but cannot be moved to help other states.
The following table gives the details of electricity production in India during
the last 10 years.
Installed
Capacity
as on
Coal Gas Diesel Nuclear Hydel Renewable total
31-Mar-
1997
54,154 6,562 294 2,225 21,658 902 85,795
31-Mar-
2002
62,131 11,163 1,135 2,720 26,269 1,628 105,046
31-Mar-
2007
71,121 13,692 1,202 3,900 34,654 7,760 132,329
31-Mar-
2012
112,022 18,381 1,200 4,780 38,990 24,503 199,876
31-Mar-
2015
169,118 23,062 1,200 5,780 41,267 35,777 276,204
31-Mar-
2016
185,172 24,508 993 5,780 42,783 42,727 301,963
1.2 Brief introduction about GTPS, Vijjeswaram
GTPS, Gas turbo power station, vijjeswaram is the first gas based
power generating plant in south India. It is located on the left flank of Sir
Arthur Cotton Barraige on the western side of the river Godavari. It is a joint
sector plant owned by AP Gas Power Corporation ltd and many other private
sector companies.

4
It consists of two stages i.e. Stage-I & Stage-II with a total capacity of
272 MW i.e. 100 MW& 172 MW respectively and both the stages are
installed as combined cycle plants of both gas and steam turbines. Stage-l
was setup during the years 1990-92 with a capacity of 100MW, comprising 2
x 33 MW Gas Turbines and 1 x 34 MW Steam Turbine. This is the first gas
based power plant in South India.
Stage-II with installed capacity of 1x112MW Gas turbine and 1x60
MW steam turbine was commissioned during 1997-98. This has provision to
run with 100% natural gas or dual fuel i.e…, natural gas with Naphtha

5
2 Electricity production through Gas
Generally, electricity production using gas is done using two different
power cycles
 Simple Cycle
 Combined Power Cycle
2.1 Simple Cycle
When a gas turbine is arranged to operate in simple cycle mode,
air is drawn in from the atmosphere, compressed, heated by combustion with
a fuel and expanded through the turbine. The mechanical power generated as
a result of rotation of the turbine is used to drive an electrical generator and
the hot gases are exhausted to the atmosphere.
Figure 1
The connection between the turbine and the driven machine may
be through direct coupling of the drive/ driven machine shafts, or through a
speed adjustment gearbox. Since the electrical generator speed is normally
kept constant, the direct coupling is usually used for the larger power
generation machines in order to optimize the mechanical efficiency.

6
The simple cycle arrangement is often used for small installations,
or in areas where there is a large demand for power and fuel prices are low.
However, owing to its low fuel to electricity efficiency (30–35%), its use is
not common in the industry.
Improvements to this efficiency can be made through recovering
some of the heat in the gas exhaust and using it to preheat fuel or inlet air.
Developments have led to other uses for the hot exhaust gas streams and the
'combined cycle' arrangement.
2.2 Combined Power Cycle
The process for converting the energy in a fuel into
electric power involves the creation of mechanical work, which is then
transformed into electric power by a generator. Depending on the fuel type
and thermodynamic process, the overall efficiency of this conversion can be
as low as 30 percent. This means that two-thirds of the latent energy of the
fuel ends up wasted. For example, steam electric power plants which utilize
boilers to combust a fossil fuel average 33 percent efficiency. Simple cycle
gas turbine (GTs) plants average just under 30 percent efficiency on natural
gas, and around 25 percent on fuel oil. Much of this wasted energy ends up
as thermal energy in the hot exhaust gases from the combustion process.
To increase the overall efficiency of electric power plants,
multiple processes can be combined to recover and utilize the residual heat
energy in hot exhaust gases. In combined cycle mode, power plants can
achieve electrical efficiencies up to 60 percent. The term “combined cycle”
refers to the combining of multiple thermodynamic cycles to generate power.
Combined cycle operation employs a heat recovery steam generator (HRSG)
that captures heat from high temperature exhaust gases to produce steam,
which is then supplied to a steam turbine to generate additional electric

7
power. The process for creating steam to produce work using a steam turbine
is based on the Rankine cycle.
The most common type of combined cycle power plant
utilizes gas turbines and is called a combined cycle gas turbine (CCGT) plant.
Because gas turbines have low efficiency in simple cycle operation, the
output produced by the steam turbine accounts for about half of the CCGT
plant output. There are many different configurations for CCGT power
plants, but typically each GT has its own associated HRSG, and multiple
HRSGs supply steam to one or more steam turbines. For example, at a plant
in a 2x1 configuration, two GT/HRSG trains supply to one steam turbine;
likewise there can be 1x1, 3x1 or 4x1 arrangements. The steam turbine is
sized to the number and capacity of supplying GTs/HRSGs.
In GTPS both the stages use combined cycle to generate
electricity. In Stage - I exhaust from both the gas turbines is collected and is
used to produce steam which is used to run the steam generator. The same
happens in stage - II with the one gas turbine present there.
2.3 Components of a Combined Cycle Power Plant
Electricity generation in a Combined cycle power plant happens in two steps
1. Gas turbine Generator
2. Heat Recovery Steam Generator (ḪRSG)

8
Figure 2

9
3 . Gas Turbines
3.1 Introduction
Gas turbine is rotary type of I.C. engine. The cyclic events of gas
turbine are similar to reciprocating type I.C. engine, but each event in the gas
turbine is carried out in different devices.
A simple gas turbine is comprised of three main sections a
compressor, a combustion chamber, and a power turbine. The gas-turbine
operates on the principle of the Brayton cycle, where compressed air is
mixed with fuel, and burned under constant pressure conditions. The
resulting hot gas is allowed to expand through a turbine to perform work. In
a 33% efficient gas-turbine approximately two / thirds of this work is spent
compressing the air, the rest is available for other work i.e. (mechanical
drive, electrical generation).
The air is first compressed in a rotary compressor before passing
to combustion chamber where fuel is injected and ignited. The hot burnt
gases expand through the blades of a turbine where the kinetic energy of

10
burnt gases is utilized to produce power. Finally the gases are exhausted
from the turbine unit.
The part of power developed is used to drive the compressor, thus
the overall efficiency of the gas turbine unit is lowered. Gas turbines are
comparatively small weight and size as that of steam turbines.
3.2 Components of Gas Turbine
There are three main components in any Gas turbine. They are:
1. Compressor
2. Combustion Chamber
3. Turbine
1. Compressor
Air is drawn into the compressor via guide vanes and flows in
the direction of the shaft axis through several rows of stationary vanes
(stators) and rotating blades (rotor buckets). Each vane/blade set is known as
a compressor stage and serves to progressively increase air pressure as it
passes from stage to stage.
Figure 3

11
2.Combustion Chamber
Within the combustion chamber the compressed air is mixed
with vaporized fuel and the mixture is burned. This creates products of
combustion that are at a higher temperature than the compressed air and is
used to do more work than the energy used in compressing the air.
Figure 4
3. Turbine
The hot, high pressure products of combustion are passed to the
turbine where they are allowed to expand through several rows of alternate
stationary vanes and rotating blades. Each vane/blade set is known as a
turbine stage, and as the mixture accelerates past each stage, the kinetic
energy within the expanding gas is converted into rotational energy using the
rotor blades.

12
Figure 5
3.3 Simple gas Turbine
A schematic diagram for a simple-cycle, single-shaft gas
turbine is shown in figure - 6. Air enters the axial flow compressor at point -
1 at ambient conditions. Air entering the compressor at point- 1 is
compressed to some higher pressure. No heat is added; however, the
temperature of the air rises due to compressio00n, so that the air at the
discharge of the compressor is at a higher temperature and pressure.
Figure 6
Upon leaving the compressor, air enters the combustion system at
point-2, where fuel is injected and combustion takes place. The combustion
process occurs at essentially constant pressure. Although very high local
temperatures are reached within the primary combustion zone (approaching
stoichiometric conditions), the combustion system is designed to provide
mixing, burning, dilution, and cooling.
Thus, by the time the combustion mixture leaves the combustion
system and enters the turbine at point-3, it is a mixed average temperature. In
the turbine section of the gas turbine, the energy of the hot gases is converted
into work. This conversion actually takes place in two steps. In nozzle
section of the turbine, the hot gases are expanded and a portion of the
thermal energy is converted into kinetic energy. In the subsequent bucket

13
section of the turbine, a portion of the kinetic energy is transferred to the
rotating buckets and converted to work. Some of the work developed by the
turbine is used to drive the compressor, and remainder is available for useful
work at the output flange of the gas turbine. Typically, more than 50% of the
work developed by the turbine sections is used to power the axial flow
compressor.
3.4 Classification of Gas Turbines
Gas turbines are classified as follows :
1. According to path of working fluid:
a) Open-cycle gas turbine
b) Closed-cycle gas turbine
2. According to basis of combustion process:
a) Constant pressure type gas turbine
b) Constant volume type gas turbine
3.4.1 Open - Cycle Gas Turbine
The rotary compressor takes in air from atmosphere and raises
the pressure to required level. The compressed air from compressor enters
combustion chamber where it mixes with fuel, and ignition takes place at
constant pressure. The hot gases expands through turbine blades producing
power, after expansion gases are exhausted into atmosphere. Part of the
turbine power is used to drive the compressor and remaining is utilized to
generate electricity.
Open gas turbine cycle is the most basic gas turbine unit. The
working fluid does not circulate through the system, therefore it is not a true
cycle. It consists of a compressor, a combustion chamber and a gas turbine.

14
The compressor and the gas turbine are mounted on the same shaft. The
compressor unit is either centrifugal or axial flow type.
3.4.2 Closed - cycle Gas Turbine
In this case the same working fluid (air) is continuously
circulated. Air is first compressed adiabatically in a compressor and high
compressed air enters the heat exchanger where air is heated at high pressure
by external source. Here air is not in direct contact with fuel i.e., air is not in
contact with products of combustion. Hot air is now expanded adiabatically
through turbine blades producing power. The air leaving the turbine enters
the coolers where it is cooled to initial temperature by circulating cooling
water. Cooled air is recirculated to the compressor and the cycle is repeated.
Figure 7
3.5 Factors effecting performance of Gas Turbine
Since the gas turbine is an ambient air-breathing engine. Its
performance will be changed by anything affecting the mass flow of the air
intake to the compressor, most obviously changes from the reference
conditions of 59°F (15°C) and 14.7 PSIA (1.013 bar). Figure 8 illustrates
how ambient temperature affects output, heat rate, heat consumption, and

15
exhaust flow for Frame 9E 03 gas turbine manufactured be “General
Electric” present at GTPS, Vijjeswaram. Each turbine model will have its
own temperature-effect curve, as it depends on the cycle parameters and
components efficiencies as well as air mass flow.
Figure 8
Correction for altitude or barometric pressure is more
straightforward. The less dense air reduces the airflow and output
proportionately heat rate and other cycle parameters are not affected.
Similarly, moist air, being less dense than dry air, will also have an effect on
output and heat rate. In past, this effect was thought to be too small to be
considered

16
Figure 9
However, with the increasing size of gas turbines and
utilization of humidity to bias water and steam injection for NOx control, this
effect has greater significance. It should be noted that this humidity effect is
a result of the control system approximation of firing temperature used on
GE heavy-duty gas turbines. Single shaft turbines that use turbine exhaust
temperature biased by compressor discharge pressure will reduce power as a
result of ambient humidity because the density losses due to compressor inlet
air temperature. The control system is set to follow the inlet air temperature
function. Inserting air filtration, silencing, evaporative coolers, chillers in the
inlet, or exhaust heat recovery devices causes pressure losses in the system.
The effects of these pressure losses are somewhat unique to each design.The
effect of humidity is given by the following graph

17
Figure10
Fuel type will also impact performance. The natural gas
produces more output than does distillate oil. This is due to the higher
specific heat in the combustion Products of natural gas, resulting from the
higher water vapor content produced by the higher hydrogen/carbon ratio of
methane.As a result of these influences, each turbine model will have some
application guidelines on flows, temperatures, and shaft output to preserve
its design life. In most cases of operation with lower heating value fuels, it
can be assumed that output and efficiency will be equal to or higher than that
obtained on natural gas. In the case of higher heating value fuels, such as
refinery gases, output and efficiency may be equal to or lower than that
obtained on natural gas.

18
Figure 11
3.6 PERFORMANCE ENHANCEMENTS:
Generally, controlling some of the factors that affect gas turbine
performance is not possible. Most are determined by the planned site
location and the plant configuration, i.e., simple- or combined-cycle. In
the event additional output is needed, several possibilities to enhance
performance may be considered
3.6.1 Inlet Cooling
The ambient effect curve(Figure 8) clearly shows that turbine
output and heat rate are improved as compressor inlet temperature decreases.
Lowering the compressor inlet temperature can be accomplished by
installing an evaporative cooler or Inlet chiller in the inlet ducting
downstream of the inlet filters. Careful application of these systems is

19
necessary, as condensation or carryover can exacerbate fouling and degrade
performance. Generally, such systems are followed by compressor the
moisture separators or coalescing pads to reduce possibility of moisture
carryover.
Figure12 : Effect of evaporative cooling on heat rate and output
As Figure 12 shows, the biggest gains from evaporative cooling
are realized in hot, low - humidity climates. It should be noted, from Figure
12, that evaporative cooling is limited to ambient temperatures of 59
F/150
C and above because of potential for icing the compressor. Information
contained in Figure 12 is based on an 85% effective evaporative cooler.
Effectiveness is of how close the cooler exit temperature
approaches the a measure ambient wet bulb temperature. For most
applications, coolers having an effectiveness of 85% or 90% provide the
most economic benefit.

20
Chillers, unlike evaporative coolers, are not limited by the
ambient wet bulb temperature. Tho achievable temperature is limited only
by the capacity of the chilling device to produce coolant and the ability of
the coils to heat. initially follows a line of constant specific humidity(Figure
13). As saturation is approached, water begins to condense from the air,
and mist eliminators are used. Further heat transfer cools the condensate and
air, and causes more condensation. Because of the high heat of vaporization
of water, most of the cooling energy in this regime goes to condensation and
little to temperature reduction.
Figure 13 : Inlet Chilling Process
3.6.2 Steam and Water Injection for Power Augmentation
Injecting steam or water into the head end of the combustion chamber for
NOX abatement increases mass flow and, therefore, output. Generally, the
amount of water is limited to the amount required to meet the NOX
requirement in order to minimize operating cost and impact on inspection
intervals

21
.
Figure14
Steam injection for power augmentation has been an available
option on GE gas turbines for over 30 years. When steam is injected for
power augmentation, it can be introduced into the compressor discharge
casing of the gas turbine as well as the combustion chamber. The effect on
output and heat rate is the same as that shown in the Figure 14. GE gas
turbines are designed to allow up to 5 of the compressor airflow for steam
injection to the combustion chamber and compressor discharge. Steam must
contain 50 F/28 c super heat and be at pressures comparable to fuel gas
pressures .
When either steam or water is used for power augmentation, the
control system is normally designed to allow only the amount needed for
NOX abatement until the e machine reaches base load. At that point,
additional steam or water can be(full) admitted via the governor control.
3.7 PERFORMANCE DEGRADATION

22
All turbo machinery experiences losses in performance with time.
Gas turbine performance degradation can be classified as recoverable or non-
recoverable loss. Recoverable loss is usually associated with compressor
fouling and can be partially rectified by water washing or more thoroughly,
by mechanically cleaning the compressor blades and vanes after opening the
unit. Non-recoverable loss due primarily to increased turbine and
compressor clearances and changes in surface finish and airfoil contour.
Because this loss is caused by reduction in efficiencies,it cannot be
recovered by operational procedures, external maintenance or compressor
cleaning, but only through replacement of affected parts at recommended
inspection intervals.
Quantifying performance degradation is difficult because
consistent, valid field data is hard to obtain. Correlation between various
sites is impacted by variables such as mode of operation, contaminants in
the air, humidity, fuel and diluent injection levels for NOX Another problem
is that test instruments and procedures vary widely, often with large
tolerances.
Typically, performance degradation during the first 24,000 hours
of operation(the normally recommended interval for a hot gas path
inspection) is 2% to 6% from the performance test measurements when
corrected to guaranteed conditions. This assumes degraded parts are not
replaced. If replaced, the expected performance degradation is 1% to 1.5%.
Recent field experience indicates that frequent off-line water washing is not
only effective in reducing recoverable loss, but also reduces the rate of non-
recoverable loss.

23
One generalization that can be made from The data is that
machine located in 3 dry, hot climates typically degrade less than those in
humid climates.
3.8 Advantages of Gas Turbine
1. Equipment Cost
The basic cost of a gas turbine-based power plant is
significantly less than similar sized alternatives, such as conventional coal or
oil fired facilities. As an example, the cost per installed kilowatt (kW) for a
gas turbine based plant is in the region of $200 to $350 compared with $750
to $1,000 for a conventional coal-fired plant.
2. Lead Time
The time from placement of order to final commissioning of a gas
turbine based power plant can be significantly shorter than similar sized
alternatives. As an example, construction of a simple cycle gas turbine based
plant can take as little as 12 months, compared with three to five years for a
conventional coal-fired plant.
3. Efficiency
Gas turbine based power plants can be extremely efficient
depending on the design and arrangement of the equipment. Fuel to
electricity efficiencies of 55–60% are achievable compared with a norm of
35–38% for conventional coal-fired plant.
4. Environmental Impact

24
Gas turbine based plant has much less impact on the environment
than similar sized alternatives. Emissions of harmful gases and particulates
are significantly lower than conventional coal-fired plants, and their physical
size is also small since there is no need for large civil works, extensive fuel
stock piles, ash dumps etc.
3.9 Gas Turbines At GTPS
At GTPS there are a total of 3 gas turbines(2 in stage - I and 1 in stage - II)
The following table gives their specifications.
Table
Stage - I Stage - II
N.O of Gas Turbines 2(2 x 33 MW) 1(112 MW)
Model GE Frame 6B GE Frame 9E
Control System MARK - IV MARK - VI
Compressor Stages 17 17
Turbine Stages 3 3
Shaft Rotation Speed 5100rpm 3000rpm
Load gear box Available Not available
Starting device Diesel engine Electrical starting motor
Fuel Natural gas Natural gas and naptha
(duel fuel system)
Why use a Load gear box?
The diesel engine is used to provide the starting torque for gas turbine, while
firing takes place in combustion chamber. This diesel engine accelerates the
turbine shafts to high speeds which are far greater than the generator rated
speed. In order to regulate this excess speed and to bring the generator to run
at its rated speed, a load gear box is used.

25
4. Heat Recovery Steam Generator
4.1 Introduction
The HRSG is basically a heat exchanger, or rather a series of
heat exchangers. It is also called a boiler, as it creates steam for the steam
turbine by passing the hot exhaust gas flow from a gas turbine or combustion
engine through banks of heat exchanger tubes. The HRSG can rely on
natural circulation or utilize forced circulation using pumps. As the hot
exhaust gases flow past the heat exchanger tubes in which hot water
circulates, heat is absorbed causing the creation of steam in the tubes. The
tubes are arranged in sections, or modules, each serving a different function
in the production of dry super-heated steam. These modules are referred to
as economizers, evaporators, super-heaters/reheaters and preheaters.
4.2 Classification of HRSG
Modular HRSGs can be categorized by a number of ways such
as direction of exhaust gases flow or number of pressure levels. Based on the
flow of exhaust gases, HRSGs are categorized into vertical and horizontal
types. In horizontal type HRSGs, exhaust gas flows horizontally over

26
vertical tubes whereas in vertical type HRSGs, exhaust gas flow vertically
over horizontal tubes.
Based on pressure levels, HRSGs can be categorized into single
pressure and multi pressure. Single pressure HRSGs have only one steam
drum and steam is generated at single pressure level whereas multi pressure
HRSGs employ two (double pressure) or three (triple pressure) steam drums.
As such triple pressure HRSGs consist of three sections: an LP (low pressure)
section, a reheat/IP (intermediate pressure) section, and an HP (high pressure)
section. Each section has a steam drum and an evaporator section where
water is converted to steam. This steam then passes through super heaters to
raise the temperature beyond the one at the saturation point.
GTPS employs a horizontal multi-pressure (double) HRSG in both Stage - I
and Stage - II
4.3 Components Of an HRSG
The various components of HRSG are explained below
Evaporator section:
This is the most important section of HRSG. In this
section the water gets evaporated to steam. This section consists of coils in
which water is passed, and these coils are surrounded by exhaust gas
released by the gas turbine. The heat transferred is enough to evaporate the
water to steam and thus the steam is generated in an evaporator
Super heater section
The Super heater section of HRSG is used to dry the
saturated vapour being separated in the steam drum. In some units it may
only be heated to little above the saturation point wherein other units it may

27
be super-heated to significant temperature for additional energy storage. The
Super heater section is normally located in the hotter gas stream, in front of
the evaporator.
Economizer:
The Economizer Section, sometimes called a preheater or
preheat coil, is used to preheat the feed water being introduced to the system
to replace the steam being removed from the system via the super heater or
steam outlet and the water loss through blow down. It is normally located in
the colder gas downstream of the evaporator. Since the evaporator inlet and
outlet temperatures are both close to the saturation temperature for the
system pressure, the amount of the heat that may be removed from the flue
gas is limited due to the approach to the evaporator, whereas the economizer
inlet temperature is low, allowing the flue gas temperature to be taken lower.

28
5. Steam turbine
5.1 Introduction
A steam turbine is a mechanical device whose purpose is to
convert thermal energy into work. Thermal energy is the type of energy that
manifests itself as an increase in temperature. The steam turbine uses thermal
energy from steam under pressure and converts it into rotary motion or
mechanical work. The original version of the steam turbine was the steam
engine, which was powered by reciprocating pistons. Steam turbines are idle
prime movers for driving machines requiring rotational mechanical input
power. They can deliver constant or variable speed and are capable of close
speed control. Drive applications include centrifugal pumps, compressors,
ship propellers and electric generators.
5.2 Components of Steam Turbine
The main components of Steam turbines are
1. Casings
2. Blading
3. Blade carriers with stationery blades
4. Welded disc rotor with rotating blades
5. Dummy Piston
6. Rotor Coupling
7. Gland seals
Casings :
Turbine casings are pressure vessels which contain the steam so
that it can perform work by causing rotation of the turbine shaft. The type
and size of casing materials are determined primarily by pressure and

29
temperature conditions of steam. Components mounted in the casing are the
blade carriers, turbine shaft and shaft seals. Blade carriers hold and maintain
the stationary blades in place. The turbine shaft and rotating blades provide
the torque to rotate the generator shaft. The mechanical energy conversion
takes place across the stationary and rotating blades. Shaft seals provide
sealing between the casing and shaft. They prevent HP steam from leaking
out and air from entering into the LP turbine, which is under vacuum.
Blading :
Turbine blades convert the thermal energy into mechanical energy,
which is then supplied to the generator via the rotor. Each stage consists of
stationary and rotating blades. There are basically two types of blade designs
in use today.
1. Impulse design
2. Reaction design
In the impulse design, theoretically all the pressure drop is across
the stationary blading and essentially none across the rotating blades. This
design is characterized by a long, slender rotor with diaphragms, which are
used for sealing.
In the reaction design, there is an equal pressure drop across both
the stationary and rotating blades, which leads to very similar blade profiles.
The reaction design is characterized by a drum type rotor. Since there is a
pressure drop across the rotating blades, a thrust is developed which must be
compensated either by a dummy or balance piston or a modified steam path
layout.

30
Dummy or Balance Piston :
The design of reaction blading results in a pressure drop across
both stationary and rotating blades. This means that a thrust force is applied
to the rotor in the direction of steam flow. The most common method to
reduce this force is to alternate the flow direction in the different stages (HP,
IP, LP) and to use a dummy or balance piston.
The diameter of this piston is calculated as to minimize the force.
This force varies with the different operation data (MW output). It is
transmitted via the axial bearing to the casing, and from there to the
foundation.
Rotor flange coupling :
Couplings are introduced to increase the ability for individual
overhaul and transport.Coupling flanges have honed bores into which
coupling bolts with expansion sleeves are screwed. During operation, torque
is transmitted by the shearing force of the bolts and sleeves. At the same
time, the radially pre-tensioned sleeves center the coupling halves so they do
not slip, even in cases of electrical disturbances with high transient loads.
The gas turbine and the generator are one unit and are coupled
rigidly with an expansion sleeve coupling. The steam turbine is used only in
combination with combined cycle and therefore the coupling is flexible. The
design is made in such a way that the steam turbine can be started
individually and will be coupled to the generator at nominal speed.
Gland Seals :
Stationary and rotating turbine components must be sealed to
prevent steam leakages into the atmosphere,air leakages into the LP turbine,

31
maintain the correct and efficient steam flow within the turbine.Since
contact-type shaft sealing can cause distortion and deformation of the rotor,
sealing segments are designed to be non-contacting during operation thus
limiting friction effects.The seal is built as a labyrinth for the steam which,
passing the labyrinth, continuously loses pressure.

32
Conclusion
In review this internship has been an excellent and rewarding
experience. I have been able to meet and network with so many people that I
am sure will be able to help me with opportunities in the future.
One main thing that I have learned through this internship is time
management skills as well as self-motivation. When I first started I did not
think that I was going to be able to make myself sit in an office for eight
hours a day, five days a week. Once I realized what I had to do I organized
my day and work so that I was not overlapping or wasting my hours. I
learned that I needed to b organized and have questions ready for when it
was the correct time to get feedback. From this internship and time
management I had to learn how to motivate myself through being in the
office for so many hours. I came up with various proposals and ideas that
the company is still looking into using

Final report

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (8)

Similar to Final report

Similar to Final report (20)

Final report