Power plant engineering unit 3 notes by Varun Pratap Singh

Power Plant Engineering
Unit-3
NOTES
by
Varun Pratap Singh
Assistant Professor
Mechanical Engineering Department
College of Engineering Roorkee

Disclaimer
This document does not claim any originality and cannot be used as a substitute for prescribed
textbooks. The information presented here is merely a collection by the subject faculty members
for their respective teaching assignments. Various sources as mentioned at the end of the
document as well as freely available material from the internet were consulted for preparing
this document. The ownership of the information lies with the respective authors or institutions.
Further, this document is not intended to be used for commercial purposes and the subject faculty
members are not accountable for any issues, legal or otherwise, arising out of the use of this
document. The subject faculty members make no representations or warranties concerning the
accuracy or completeness of the contents of this document and specifically disclaim any
implied warranties of merchantability or fitness for a particular purpose. The subject faculty
members shall be liable for any loss of profit or any other commercial damages, including but
not limited to special, incidental, consequential, or other damages.

Youtube Video Reference:
1. MECH vidyarthi
https://www.youtube.com/channel/UCF2-2izHHPmDFFLDMV1hFHQ
2. Hyundai Engine Power Plant
https://www.youtube.com/channel/UCjuru-Cqitorn3V_06eYjCA
3. MAN Energy Solutions
https://www.youtube.com/channel/UCHQcKZdam9qg72REs6RTuqQ
4. Hyundai Engine & Machinery
https://www.youtube.com/watch?v=kAJA7ehEyRc
5. Irfan's Life
https://www.youtube.com/channel/UCjwUeqCL7uoSSGbgVTRq28w
6. Mechanical Engineering Association (MEA) - BITS Pilani, Dubai Campus
https://www.youtube.com/watch?v=N4dj8SX1SPU
7. BEST MECHANICAL ENGINEERING
https://www.youtube.com/channel/UC4vN8jWyjDlyRfryqQ3izsQ
8. ANUNIVERSE 22
https://www.youtube.com/channel/UC_47JgXfkr6nsfMxVOl9CsA
9. RealPars
https://www.youtube.com/channel/UCUKKQwBQZczpYzETkZNxi-w
10. Engineering World
https://www.youtube.com/watch?v=t7N1kKz5faM
11. Beyond the press
https://www.youtube.com/watch?v=yD2-auVioyU
12. Amit Mandal
https://www.youtube.com/channel/UCRJzWmd_kjK38flvDIVk79Q
13. GE Power
https://www.youtube.com/user/gepowerwatervideos
14. King Mechanical
https://www.youtube.com/watch?v=HlSCn0esufk
15. Siemens
https://www.youtube.com/channel/UCaEEm-0s0x3MHg9jzFcHuQQ
16. ‫غازى‬ ‫شادى‬ (Technical Engineering School)
https://www.youtube.com/channel/UCR0EfsRZIwA5TVDaQbTqwEQ

SYLLABUS
Unit-III
Diesel power plant
General layout, performance of diesel engine, fuel system, lubrication system, air intake and
admission system, supercharging system, exhaust system, diesel plant operation and efficiency,
heat balance.
Gas turbine power plant
Elements of gas turbine power plants, Gas turbine fuels, cogeneration, auxiliary systems such
as fuel, controls and lubrication, operation and maintenance, Combined cycle power plants.

Diesel power plant
https://www.youtube.com/watch?v=cIk7zsKKofo (English)
https://www.youtube.com/watch?v=6gvMn3eu8Jw (English + Hindi)
A diesel power plant or standby power station is the plant when we use diesel engine as a
prime mover or combine a diesel engine with an electric generator to produce electrical energy
by using diesel fuel or liquid fuels like natural gas. It’s generally a compact station so it can be
located when we actually require it. And the diesel power plant produces limited amounts of
electricity. also as an emergency supply station for many countries; and as diesel plant
produces power in the range of 2 to 50 MW; So, we can use it as standby sets to supply peak
load of hospitals, radio station, telephone exchanges, industries, cinema theatres, and very
suitable for mobile power generation, railways and ships.
https://www.youtube.com/watch?v=IVHyKg6sydk
https://www.youtube.com/watch?v=9RhMfmDXCko
Diesel power plant working principle:
https://www.youtube.com/watch?v=eAX_fK_c8Mc
(English)
The working principle of the diesel power station is very
simple; as we compress the air in a cylinder to raise the
temperature, then we burn the diesel inside the engine and
the combustion produces the working fluid at high
temperature and high pressure to convert the heat energy into
mechanical energy. And as the diesel engine acts as a prime
mover it rotates the rotor of the electrical generator and
converts this mechanical energy into electrical energy. This
working principle is a working cycle done by the processes:
intake, compression, expansion, and exhaust.

Why needed? (Application of diesel engine electric plant):
(a) Peak load plants: Diesel plants can be used in combination with thermal or hydro plants as peak
load units. They can be easily started or stopped at short notice to meet the peak demand.
(b) Mobile plants: Diesel plants mounted on trailer can be used for temporary or emergency
purposes such as supplying power to large civil engineering works.
(c) Standby unit: If the main unit fails or can’t cope up with demand, a diesel plant can supply
necessary power. For example, if the water available in the hydro plant is not adequately available
due to less rainfall, the diesel station can operate in parallel to generate short fall of power.
(d) Emergency plant: During power interruption in a vital unit like key industrial plant or hospital,
a diesel-electric plant can be used to generate the needed power.
(e) Nursery station: In the absence of the main grid, a diesel plant can be installed to supply power
in a small town. In course of time when electricity from main grid becomes available in the town,
the diesel unit can be shifted to some other station is called nursery station.
(f) Starting station: Diesel units can be used to run auxiliaries (like FD & ID fans) for starting large
steam power plant.
(g) Central station: Diesel-electric plant can be used as central station where power required is small.
PERFORMANCE OF DIESEL ENGINE
https://www.youtube.com/watch?v=FTQjB8j3eTk
The performance of the diesel engine means power and efficiency. The engine develops as
the various parameters of the engine, e.g. piston speed, air-fuel ratio, compression ratio, inlet
air pressure and temperature are varied.
The two usual conditions under which I.C. engines are operated are:
(1) constant speed with variable load, and
(2) variable speed with variable load.
The first situation is found in a.c. generator drives and the second one in automobiles, railway
engines and tractors etc. A series of tests are carried out on the engine to determine its
performance characteristics, such as: indicated power (I.P.), Brake power (B.P.), Frictional
Power (F.P.), Mechanical efficiency (ηm), thermal efficiency, fuel consumption and also
specific fuel consumption etc. Below, we shall have discussed how these quantities are
measured:
https://www.youtube.com/watch?v=N4dj8SX1SPU
INDICATED MEAN EFFECTIVE PRESSURE (IMEP)
In order to determine the power developed by the engine, the indicator diagram of engine
should be available. From the area of indicator diagram it is possible to find an average gas
pressure that while acting on piston throughout one stroke would account for the network done.
This pressure is called indicated mean effective pressure (I.M.E.P.).
INDICATED HORSE POWER (IHP)
The indicated horse power (I.H.P.) of the engine can be calculated as follows:

where
Pm = LM.E.P. in kg/cm2
L = Length of stroke in metres
A = Piston areas in cm2
N = Speed in R.P.M.
n = Number of cylinders
k = 1 for two stroke engine
= 2 for four stroke engine.
BRAKE HORSE POWER (B.H.P.)
Brake horse power is defined as the net power available at the crankshaft. It is found by
measuring the output torque with a dynamometer.
where
T = Torque in kg.m.
N = Speed in R.P.NT.
FRICTIONAL HORSE POWER (F.H.P.)
The difference of I.H.P. and B.H.P. is called F.H.P. It is utilized in overcoming frictional
resistance of rotating and sliding parts of the engine.
F.H.P. = I.H.P. – B.H.P.
INDICATED THERMAL EFFICIENCY (ηi)
It is defined as the ratio of indicated work to thermal input.
where W = Weight of fuel supplied in kg per minute.
CV = Calorific value of fuel oil in kcal/kg.
J = Joules equivalent = 427.
BRAKE THERMAL EFFICIENCY (OVERALL EFFICIENCY)
It is defined as the ratio of brake output to thermal input.
MECHANICAL EFFICIENCY (ηm)
It is defined as the ratio of B.H.P. to L.H.P. Therefore,

General Layout of Diesel Power Plant
https://www.youtube.com/watch?v=QDP2PCo0jMM
• The layout of a diesel engine power plant is shown in above figure.
• Diesel engine units are installed side by side with some room left fur extension in the future
• The repairs and usual maintenance works require some space around the units.
• The air intakes and filters are exhaust mufflers are located outside.
• Adequate space for oil storage, repair shop and office are provided as shown.
• Bulk storage of Oil may be outdoors.

Engine starting system: it’s used in old conditions as a starter as it uses the air to push the
engine and start an initial rotation until the engine run with its own power, and the starting
methods may be:
Following are the three common method of starting an engine.
i. By an auxiliary engine, this is mounted close to the main engine and drives the latter through
a clutch and gears.
ii. By using an electric motor (Self-starters), which used in small diesel engines where motor
draws heavy current and designed to work for continuously 30 Sec after it’s cooled. A storage
battery 12 to 36 volts is used to supply power to an electric motor that derives the engine.
iii. By compressed air system, in which compressed air at about 17bar supplied from an air
tank is admitted to a few engine cylinders making them work like reciprocating air motors to
run the engine shaft. Fuel is admitted to the remaining cylinders and ignited in the normal way
causing the engine to start. The compressed air system is commonly used for starting large
diesel engines employed for stationary power plant service.
Essential component or element of diesel-electric plant
The diesel power station consists of many components used to achieve the best of the plant
let’s illustrate:
1. Engine
2. Air intake system
3. Fuel system
4. Exhaust system
5. Cooling system
6. Lubrication system
Engine: it’s the main part of the plant which used to produce power, it may be of the two-
stroke or four strokes.
Air intake system: https://www.youtube.com/watch?v=LxpSN_kdOYk
it’s used to remove the dust particles from the atmospheric air to supply fresh air to the engine
for combustion, it may be dry (or oil) bath filter or oil immersed filter, and it consists of pipes
to supply the fresh air and filters to remove dust particles from the air.

Fuel supply system: https://www.youtube.com/watch?v=RcKS_ZFiKwU it consists of a
storage tank where we store the oil supplied to the plant, all day fuel tank where the oil pumped
for usage, strainer which used to remove suspended impurities of the oil, and fuel injection
(transfer) pump which used to inject the clean oil into the engine.
The five essential functions of a fuel injection system are:
1. To deliver oil from the storage to the fuel injector.
2. To raise the fuel pressure to the level required for atomization.
3. To measure and control the amount of fuel admitted in each cycle.
4. To control time of injection.
5.To spray fuel into the cylinder in atomized form for thorough mixing and burning.
The above functions can be achieved in a variety of ways. The following are the systems,
which are usual on power station diesels:
1.Common Rail.
2.Individual Pump Injection.
3. Distributor
1. COMMON RAIL INJECTION https://www.youtube.com/watch?v=qrEtGk3yv6I
https://www.youtube.com/watch?v=Xc3tgZ_xMmM
A typical common rail injection system is shown in
Fig. It incorporates a pump with built in pressure
regulation, which adjusts pumping rate to maintain the
desired injection pressure. The function of the pressure
relief and timing valves is to regulate the injection time
and amount. Spring-loaded spray valve acts merely as
a check. When injection valve lifts to admit high-
pressure fuel to spray valve, its needle rises against the
spring. When the pressure is vented to the atmosphere,
the spring shuts the valve.

2. INDIVIDUAL PUMP INJECTION
In this system, each fuel nozzle is connected to a
separate injection pump, Fig.8.5. The pump itself
does the measuring of the fuel charge and control of
the injection timing. The delivery valve in the
nozzle is actuated by fuel-oil pressure.
3. DISTRIBUTOR SYSTEM
This system is shown in Fig. 8.6. In this system, the
fuel is metered at a central point i.e., the pump that
pressurizes, meters the fuel and times the injection.
From here, the fuel is distributed to cylinders
incorrect firing order by a cam operated poppet
valves, which open to admit fuel to nozzles.
Exhaust system: it’s used to remove the exhaust gas from the engine to the atmosphere, and
we also add a silencer to this system to reduce the noise level of the system.
• Exhaust system discharge the engine exhaust to the atmosphere.
• The exhaust manifold connects the engine cylinder exhaust outlets to the exhaust pipe which
is provided with a muffler or silencer to reduce pressure on the exhaust line and eliminates
most of the noise which may result if gases are discharged directly to the atmosphere.
• The exhaust pipe should have flexible tubing system to take up the effects of expansion due
to high temperature and also isolate the exhaust system from the engine vibration.
There is scope of waste heat utilization from the diesel engine exhaust,
i. By installing a waste heat boiler to raise low pressure steam which can be used for any
process, purpose or for generating electricity.
ii. The hot exhaust may also be utilized to heat water in a gas-to-water heat exchanger which
can be in the form of a water coil installed in the exhaust muffler.
iii. It can also be used for air heating where the exhaust pipe is surrounded by the cold air
jacket.

Strainer: it’s used to remove solid impurities from the oil transferred from the main tank to
small dry tank through this strainer.

Cooling system:
it’s very important in the diesel power station to have a cooling system to maintain the overall
temperature of the engine at an agreeable level, and this cooling system requires a water source,
a water pump which circulates water through a cylinder, and cooling towers which used to cool
the hot water.
The main function of lubricant is to,
1. To reduce friction and wear between the parts having relative motion by minimizing the
force
of friction and ensures smooth running of parts.
2. To seal a space adjoining the surfaces such as piston rings and cylinder liner.
3. To clean the surface by carrying away the carbon and metal particles caused by wear.
4. To absorb shock between bearings and other parts and consequently reduce noise.
5. To cool the surfaces by carrying away heat generated due to friction.
6. It helps the piston ring to seal the gases in the cylinder.
7. It removes the heat generated due to friction and keeps the parts cool.
The various parts of an engine requiring lubrication are;
1. Cylinder walls and pistons.
2. Main crankshaft bearings.
3. Piston rings and cylinder walls.
4. Big end bearing and crankpins.
5. Small end bearing and Gudgeon pin bearings.
6. Main bearing cams and bearing valve tappet and guides
7. Timing gears etc.
8. Camshaft and camshaft bearings.
9. Valve mechanism and rocker arms.
A good lubricant should possess the following properties:
1. It should not change its state with temperature change.
2. It should maintain a continuous film between the rubbing surfaces.
3. It should have high specific heat so that it can remove the maximum amount of heat.
4. It should be free from corrosive acids.
5. The lubricant should be purified before it enters the engine.
6. It should be free from dust, moisture, metallic chips, etc.
7. The lubricating oil consumed is nearly 1% of fuel consumption.
8. The lubricating oil gets heated because of friction of moving parts and should be cooled
before recirculation.

Following are the two methods of cooling the engine.
(i) Air cooling: Air cooling is used in small engines, where fins are provided to increase heat
transfer surface area.
https://www.youtube.com/watch?v=RQQUnYkjMxo
(ii) Water cooling:
Big diesel engines are always water cooled. The cylinder and its head are enclosed in a water
Jacket which is connected to a radiator. Water flowing in the jacket carries away the heat from
the engine and becomes heated. The hot water then flows into the radiator and gets cooled by
rejecting heat to air from the radiator walls. Cooled water is again circulated in the water jacket.
Various methods used for circulating the water around the cylinder are the following.
(a) Thermosiphon cooling: In
this method water flow is caused
by density difference. The rate of'
circulation is slow and
insufficient.
(b) Forced cooling by pump: In this
method a pump, taking power from the
engine, forces water to circulate, ensuring
engine cooling under all operating
conditions. There may be overcooling
which may cause low temperature
corrosion of metal parts due to the
presence of acids.
(c)Thermostat cooling: This is a method
in which a thermostat maintains the
desired temperature and protects the
engine from getting overcooled.
(d) Pressurized water cooling:
In this method a higher water pressure, 1.5 to 2bar, is maintained to increase heal transfer in
the radiator. A pressure relief valve is provided against any pressure drop or vacuum.
(e) Evaporative cooling: In this method water is allowed to evaporate absorbing the latent heal
of evaporation from the cylinder walls. The cooling circuit is such that the coolant is always
liquid and the steam flashes in a separate vessel.

Lubricating system: it’s used to minimize the wear of the rubbing surface of the engine as we
store oil in a main lubricating oil tank then draw this oil from an oil pump to pass through the
oil filter to remove impurities.
• Lubrication is the flow of oil between two surfaces having relative motion.
• Following are the function of lubricating system.
(a) Lubrication: To keep moving parts sliding freely past each other, thus reducing
engine friction and wear.
(b) Cooling: To keep the surface cool by taking away a part of heat caused by friction.
(c) Cleaning: To keep bearing and friction ring clean of the product of wear and
combustion by washing them away.
(d) Sealing: To form a good seal between the piston ring and cylinder wall.
(e) Reduce noise: To reduce noise of engine by absorbing vibration.
Lubrication system can be classified as, (a) Mist lubrication system, (b) Wet sump lubrication
system and (c) Dry sump lubrication system.
https://www.youtube.com/watch?v=Cr4L37v8cQI
(a) Mist lubrication system
This system is used for two stroke cycle engine which
employs crankcase compression. Thus crankcase
lubrication is not suitable in these engines.
(b) Wet sump lubrication system
The bottom part of the crankcase, called sump,
contains the lubricating oil which is pumped
to the various part of the engine. There are three types
of wet sump lubrication system; they are Splash
system, Modified splash system and Full pressure
system

Splash system:
It is used for small four stroke stationary
engines. The oil level in the sump is maintained
in such a way that when the connecting rod’s big
end at its lowest position the dippers at the end
strike the oil in the troughs which are supplied
with oil from the sump by an oil pump. Due to
striking of dippers oil splashes over various parts
of engine like crank pin, bearing, piston ring,
piston pin etc. Excess oil drips back into the
sump.
Modified splash system: -
The splash system is not sufficient if the bearing
loads are high. For such cases, the modified
splash system is used, where the main and
camshaft bearings are lubricated by oil under
pressure pumped by an oil pump. The other
engine parts are lubricated by splash system as
shown in above figure.
Full pressure system
An oil pump is used to lubricate all the parts of
the engine. Oil is pumped to the main bearing of
the crankshaft and camshaft at pressure between
1.5bar to 4bar. Drilled passages are used to
lubricate connecting rod end bearing.
A gear pump submerged in oil and driven by the
camshaft draws the oil from the sump through a
strainer. A pressure relief valve is provided on
delivery side to prevent excessive pressure.
(c) Dry sump lubrication system
Oil from the sump is carried to a separate storage
tank or supply tank outside the engine cylinder. The
oil from the dry sump pumped through the filter to
the storage tank. Oil from the supply tank is pumped
to the engine cylinder through oil cooler. Oil
pressure varies from 3bar to 8bar. Dry sump system
is generally used for high capacity engine.
From the pump all the oil used for lubrication
usually passes through an oil filter before it reaches
engine bearing. The bearings are machined through
very high tolerance and are likely to be damaged if
any foreign material is allowed to the lubrication
line.

Filter arrangement are of two types, they are in full flow type, all the oil is filtered before it
is fed to the bearings, as in dry sump lubrication.
In bypass flow type, only a small part of oil is passed through the filter and rest is directly
supplied to the bearing, as in wet sump lubrication system.
Governing system: it’s used to control the speed of the engine by changing the fuel provide
according to engine load.
Application of diesel power plant:
https://www.youtube.com/watch?v=XpWdeEZeTSQ&list=PLdoIhVhbPQV7jjmF7hGnHqo9
21bVCmywH&index=4
As diesel power station has a capacity in the range of 2 to 5MW; So, we can use it in many
applications as:
A central station for medium or small power supplies.
And for emergency services as a standby plant to hydroelectric power plants and steam power
plants.
We can Use with thermal or hydropower plants as a peak load plant in combinations.
For mobile power generation, transportation systems like automobiles, railways, airplanes, and
ships.
A nursery station to transport the power from stations to small power plants, or supply power
to small towns.
It’s economical for industries where they require a small power in the order of 500 KW as it
offers high overall efficiency. And also used for electrical power generation in capacities 100
to 500 H.P.
Advantages And Disadvantages of Diesel Power Plant
https://www.youtube.com/watch?v=UYrmdPwJ2iY&list=PLdoIhVhbPQV7jjmF7hGn
Hqo921bVCmywH&index=3
Advantages of diesel power plant:
The diesel power station is simple in everything so it has many advantages as:
1. The low initial cost which makes it easy to quickly install and commission it.
2. The design is very simple and requires small space.
3. It can start and stop with quick facilities; as small generators can start and stop in few seconds
without any standby loss in the system.
4. The thermal efficiency is quite higher than other types.
5. We can build it near the load center and doesn’t cause a problem of ash disposal exists.
6. The size of the plant is quite smaller than steam plants also they have the same capacity.
7. It’s easy to design it for portable use.
8. The cooling is easy and requires a small quantity of water.
9. There isn’t any difficulty with varying loads.
10. Also, the fuel cost required for operation is low.
11. Replacement losses are smaller
12. And it also requires fewer members of engineers.

Disadvantages of diesel power station:
To be fair, as we illustrate the advantages; we will also illustrate the disadvantages of the diesel
plant which are:
1. The higher running costs due to the high cost of the diesel.
2. The general use of this plant is to produce small power requirement.
3. It can’t stand up for a long period of overload conditions.
4. The lubricants cost is high.
5. Complex and high-cost maintenance; which makes the life of the plant small from 7 to 10
years.
6. Its capacity is only about 50 MW.
7. It’s difficult to construct it for large scale.
8. Also, the noise produced by the plant is high. Efficiency of diesel power station:
We all know that efficiency is the output of the process to the input, but here with power plants
we have main three types of efficiency which are:
Economic efficiency: which is the specific cost of production includes fuel, labor, materials
and services cost; compared to the energy output of the plant for a definite period of time.
Operational efficiency: it’s the capacity factor or load factor; which measure the actual output
from the plant compared to the potential maximum output. Energy conversion efficiency: it
closely relates to the heat rate; which is the quantity of heat required by the electrical generator
to generate 1 KWh of electricity.

GAS TURBINE POWER PLANT
https://www.youtube.com/watch?v=GF-70yncAVY (Animation)
https://www.youtube.com/watch?v=rbFx9_0G8D8 (English+ Hindi)
Introduction:-
https://www.youtube.com/watch?v=BUn5-0VG3Hw
The gas turbine has low weight to power ratio hence gas turbines are extensively used to drive
aviation system of all kind in aircraft system. It is also being increasingly used in land vehicles
such as bus and truck and also to drive locomotives and marine ships. In oil and gas industries,
the gas turbine is widely employed to drive auxiliaries like compressor blower and pumps.
Gas turbines have been constructed to work on the following: oil, natural gas, coal gas,
producer gas, blast furnace and pulverized coal.
CLASSIFICATION OF GAS TURBINE POWER PLANT
The gas turbine power plants which are used in electric power industry are classified into two
groups as per the cycle of operation.
(a) Open cycle gas turbine.
(b) Closed cycle gas turbine.
OPEN CYCLE GAS TURBINE POWER PLANT
https://www.youtube.com/watch?v=yD2-auVioyU (Cold Start)
A simple open cycle gas turbine consists of a compressor, combustion chamber and a turbine
as shown in Fig. The compressor takes in ambient air and raises its pressure. Heat is added to
the air in combustion chamber by burning the fuel and raises its temperature.
The heated gases coming out of combustion chamber are then passed to the turbine where it
expands doing mechanical work. Part of the power developed by the turbine is utilized in
driving the compressor and other accessories and remaining is used for power generation. Since
ambient air enters into the compressor and gases coming out of turbine are exhausted into the
atmosphere, the working medium must be replaced continuously. This type of cycle is known

as open cycle gas turbine plant and is mainly used in majority of gas turbine power plants as it
has many inherent advantages.
(A) Advantages
1. Warm-up time. Once the turbine is brought up to the rated speed by the starting motor
and the
fuel is ignited, the gas turbine will be accelerated from cold start to full load without warm-up
time.
2. Low weight and size. The weight in kg per kW developed is less.
3. Fuels. Almost any hydrocarbon fuel from high-octane gasoline to heavy diesel oils can be
used in the combustion chamber.
4. Open cycle plants occupy comparatively little space.
5. The stipulation of a quick start and take-up of load frequently are the points in favour of
open
cycle plant when the plant is used as peak load plant.
6. Component or auxiliary refinements can usually be varied to improve the thermal
efficiency
and give the most economical overall cost for the plant load factors and other operating
conditions
envisaged.
7. Open-cycle gas turbine power plant, except those having an intercooler, does not require
cooling water. Therefore, the plant is independent of cooling medium and becomes self-
contained.
(B) Disadvantages
1. The part load efficiency of the open cycle plant decreases rapidly as the considerable
percentage of power developed by the turbine is used to drive the compressor.
2. The system is sensitive to the component efficiency; particularly that of compressor. The
open cycle plant is sensitive to changes in the atmospheric air temperature, pressure and
humidity.
3. The open-cycle gas turbine plant has high air rate compared to the other cycles, therefore, it
results in increased loss of heat in the exhaust gases and large diameter ductwork is necessary.
4. It is essential that the dust should be prevented from entering into the compressor in order to
minimise erosion and depositions on the blades and passages of the compressor and turbine
and so impairing their profile and efficiency. The deposition of the carbon and ash on the
turbine blades is not at all desirable as it also reduces the efficiency of the turbine.

CLOSED CYCLE GAS TURBINE POWER PLANT
https://www.youtube.com/watch?v=_hXXI5oUMFQ
Closed cycle gas turbine plant was originated and developed in Switzerland. In the year 1935,
J. Ackeret and C. Keller first proposed this type of machine and first plant was completed in
Zurich in 1944.
It used air as working medium and had a useful output of 2 mW. Since then, a number of closed
cycle gas turbine plants have been built all over the world and largest of 17 mW capacity is at
Gelsenkirchen, Germany and has been successfully operating since 1967. In closed cycle gas
turbine plant, the working fluid (air or any other suitable gas) coming out from compressor is
heated in a heater by an external source at constant pressure. The high temperature and high-
pressure air coming out from the external heater is passed through the gas turbine. The fluid
coming out from the turbine is cooled to its original temperature in the cooler using external
cooling source before passing to the compressor.
The working fluid is continuously used in the system without its change of phase and the
required heat is given to the working fluid in the heat exchanger.
The arrangement of the components of the closed cycle gas turbine plant is shown in Fig..
(A) Advantages
1. The inherent disadvantage of open cycle gas turbine is the atmospheric backpressure at the
turbine exhaust. With closed cycle gas turbine plants, the backpressure can be increased. Due
to the control on backpressure, unit rating can be increased about in proportion to the
backpressure. Therefore, the machine can be smaller and cheaper than the machine used to
develop the same power using open cycle plant.
2. The closed cycle avoids erosion of the
turbine blades due to the contaminated gases
and fouling of compressor blades due to
dust. Therefore, it is practically free from
deterioration of efficiency in service. The
absence of corrosion and abrasion of the
interiors of the compressor and turbine
extends the life of the plant and maintains
the efficiency of the plant constant
throughout its life as they are kept free from
the products of combustion.
3. The need for filtration of the incoming air
which is a severe problem in open cycle
plant is
completely eliminated.
4. Load variation is usually obtained by
varying the absolute pressure and mass flow
of the circulating medium, while the pressure ratio, the temperatures and the air velocities

remain almost constant. This result in velocity ratio in the compressor and turbine independent
of the load and full load thermal efficiency maintained over the full range of operating loads.
5. The density of the working medium can be maintained high by increasing internal
pressure range, therefore, the compressor and turbine are smaller for their rated output.
The high density of the working fluid further increases the heat transfer properties in
the heat exchanger.
6. As indirect heating is used in closed cycle plant, the inferior oil or solid fuel can be
used in the furnace and these fuels can be used more economically because these are
available in abundance.
7. Finally the closed cycle opens the new field for the use of working medium (other
than air as argon, CO2, helium) having more desirable properties. The ratio γ of the
working fluid plays an important role in determining the performance of the gas turbine
plant. An increase in γ from 1.4 to 1.67 (for argon) can bring about a large increase in
output per kg of fluid circulated and thermal efficiency of the plant.
(B) Disadvantages
1. The system is dependent on external means as considerable quantity of cooling water is
required in the pre-cooler.
2. Higher internal pressures involve complicated design of all components and high quality
material is required which increases the cost of the plant.
3. The response to the load variations is poor compared to the open-cycle plant,
4. It requires very big heat-exchangers as the heating of workings fluid is done indirectly. The
space required for the heat exchanger is considerably large. The full heat of the fuel is also not
used in this plant.
The closed cycle is only preferable over open cycle where the inferior type of fuel or solid fuel
is to be used and ample cooling water is available at the proposed site of the plant. However,
closed cycle gas turbine plants have not as yet been used for electricity production.
This is mainly a consequence of the limitations imposed by the unit size of heat exchanger.
The use of a large number of parallel heat exchangers would practically eliminate the economic
advantage resulting from increased plant size.
ELEMENTS OF GAS TURBINE POWER PLANT
It is always necessary for the engineers and designers to know about the construction and
operation of the components of gas turbine plants.
COMPRESSORS
The high flow rates of turbines and relatively moderate pressure ratios necessitate the use of
rotary compressors. The types of compressors, which are commonly used, are of two types,
centrifugal and axial flow types.
The centrifugal compressor consists of an impeller (rotating component) and a diffuser
(stationary component). The impeller imparts the high kinetic energy to the air and diffuser
converts the kinetic energy into the pressure energy. The pressure ratio of 2 to 3 is possible
with single stage compressor and it can be increased up to 20 with three-stage compressor. The

compressors may have single or double inlet. The single inlet compressors are designed to
handle the air in the range of 15 to 300 m3
/min and double inlets are preferred above 300
m3/min capacity. The single inlet centrifugal compressor is shown in Fig. The efficiency of
centrifugal compressor lies between 80 to 90%. The efficiency of multistage compressor is
lower than a single stage due to the losses.
The axial flow compressor consists of a series of rotor and stator stages with decreasing
diameters along the flow of air.
The blades are fixed on the rotor and rotors are fixed on the
shaft. The stator blades are fixed on the stator casing. The
stator blades guide the air flow to the next rotor stage
coming from the previous rotor stage. The air flows along
the axis of the rotor. The kinetic energy is given to the air as
it passes through the rotor and part of it is converted into
pressure. The axial flow compressor is shown in Fig. The
number of stages required for pressure ratio of 5 is as large
as sixteen or more.
A satisfactory air filter is absolutely necessary for cleaning
the air before it enters the compressor because it is essential
to maintain the designed profile of the aerofoil blades. The
deposition of dust particles on the blade surfaces reduces the
efficiency rapidly.
The advantages of axial flow compressor over
centrifugal compressor are high isentropic efficiency
(90-95%), high flow rate and small weight for the same
flow quantity. The axial flow compressors are very
sensitive to the changes in airflow and speed, which
result in rapid drop in efficiency. In both types of
compressors, it has been found that lowering of the inlet
air temperature by 15 to 20°C gives almost 25% greater
output with an increase of 5% efficiency.
INTERCOOLERS AND HEAT EXCHANGERS
https://www.youtube.com/watch?v=Ayo5vXEGG4o&list=PLo1EW04JARVhp6ZifEiGARbwlf9Ig7g5-&index=4
The intercooler is generally used in gas turbine plant when the pressure ratio used is sufficiently
large and the compression is completed with two or more stages. The cooling of compressed
air is generally done with the use of cooling water. A cross-flow type intercooler is generally
preferred for effective heat transfer.
The regenerators, which are commonly used in gas turbine plant, are of two types, recuperator
and regenerator.

In a recuperative type of heat exchanger, the air and hot gases are made to flow in counter
direction as the effect of counterblow gives high average temperature difference causing the
higher heat flow.
A number of baffles in the path of airflow are used to make the air to flow in contact for longer
time with heat transfer surface. The regenerator type heat exchanger consists of a heat-
conducting member that is exposed alternately to the hot exhaust gases and the cooler
compressed air. It absorbs the heat from hot gases and gives it up when exposed to the air. The
heat, capacity member is made of a metallic mesh or matrix, which is rotated slowly (40-60
r.p.m.) and continuously exposed to hot and cold air.
COMBUSTION CHAMBERS
The gas turbine is a continuous flow system; therefore, the combustion in the gas turbine differs
from the combustion in diesel engines. High rate of mass flow results in high velocities at
various points throughout the cycle (300 m/sec). One of the vital problems associated with the
design of gas turbine combustion system is to secure a steady and stable flame inside the
combustion chamber. The gas turbine combustion system has to function under certain
different operating conditions which are not usually met with the combustion systems of diesel
engines. A few of them are listed below:
1. Combustion in the gas turbine takes place in a continuous flow system and, therefore, the
advantage of high pressure and restricted volume available in diesel engine is lost. The
chemical reaction takes place relatively slowly thus requiring large residence time in the
combustion chamber in order to achieve complete combustion.
2. The gas turbine requires about 100:1 air-fuel ratio by weight for the reasons mentioned
earlier. But the air-fuel ratio required for the combustion in diesel engine is approximately 15:1.
Therefore, it is impossible to ignite and maintain a continuous combustion with such weak
mixture. It is necessary to provide rich mixture ignition and continuous combustion, and
therefore, it is necessary to allow required air in the combustion zone and the remaining air
must be added after complete combustion to reduce the gas temperature before passing into the
turbine.

3. A pilot or recirculated zone should be created in the main flow to establish a stable flame
that helps to ignite the combustible mixture continuously.
4. A stable continuous flame can be maintained inside the combustion chamber when the
stream velocity and fuel burning velocity are equal. Unfortunately, most of the fuels have low
burning velocities of the order of a few meters per second, therefore, flame stabilization is not
possible unless some technique is employed to anchor the flame in the combustion chamber.
The common methods of flame stabilization used in practice are bluff body method and swirl
flow method. Two types of combustion chambers using bluff body and swirl for flame
stabilization are shown in above mentioned figures.
The major difference between two is the use of different methods to create pilot zone for flame
stabilization. Nearly 15 to 20% of the total air is passed around the jet of fuel providing rich
mixture in the primary zone. This mixture burns continuously in the primary (pilot) zone and
produces high temperature gases. About 30% of the total air is supplied in the secondary zone
through the annuals around the flame tube to complete the combustion. The secondary air must
be admitted at right points in the combustion chamber otherwise the cold injected air may chill
the flame locally thereby reducing the rate of reaction. The secondary air helps to complete the
combustion as well as helps to cool the flame tube. The remaining 50% air is mixed with burnt
gases in the “tertiary zone” to cool the gases down to the temperature suited to the turbine blade
materials.
GAS TURBINES
The common types of turbines, which are in use, are axial flow type. The basic requirements
of the turbines are lightweight, high efficiency; reliability in operation and long working life.
Large work output can be obtained per stage with high blade speeds when the blades are
designed to sustain higher stresses. More stages of the turbine are always preferred in gas

turbine power plant because it helps to reduce the stresses in the blades and increases the overall
life of the turbine. More stages are further preferred with stationary power plants because
weight is not the major consideration in the design which is essential in aircraft turbine-plant.
The cooling of the gas turbine blades is essential for long life as it is continuously subjected to
high temperature gases. There are different methods of cooling the blades. The common
method used is the air-cooling. The air is passed through the holes provided through the blade.
REGENERATION AND REHEATING
Generally, the thermal efficiency of the simple open cycle is only about 16 to 23% as lot of
heat energy goes waste in the exhaust gases. Moreover, the cycle efficiency directly depends
upon the temperature of the inlet gases to the turbine. And as the metallurgical limitations do
not permit the use of temperatures higher than about 1000°C, a sizeable increase in efficiency
cannot be expected through the increased temperature of the gases. Of course, this efficiency
handicap can be overcome by incorporating thermal refinements in the simple open cycle e.g.
regeneration, reheating. But the plant will become complex in contrast to the simple open cycle
plant which is compact, occupies very little space, does not need any water and can be quickly
run up from cold. The thermal refinements can raise the plant efficiency to over 30% and
thereby obliterate the advantage of fuel efficiency possessed by diesel or condensing steam
power plants. These refinements are discussed below:
REGENERATION
https://www.youtube.com/watch?v=P5YvuGartW0&list=PLo1EW04JARVhp6ZifEiGARbwl
f9Ig7g5-&index=3
In regeneration, the heat energy from the exhaust gases is transferred to the compressed air
before it enters the combustion chamber. Therefore, by this process there will be a saving in
fuel used in the combustion chamber if the same final temperature of the combustion gases is
to be attained and also there will be a reduction of waste heat. Fig. 9.10. shows a regenerative
cycle.

REHEATING
https://www.youtube.com/watch?v=t5IQ2TyiG5w&list=PLo1EW04JARVhp6ZifEiGARbwlf
9Ig7g5-&index=5
In reheat cycle, the combustion gases are not expanded in one turbine only but in two turbines.
The exhaust of the high-pressure turbine is reheated in a reheater and then expanded in a low-
pressure turbine. By reheating, the power output of the turbine is increased but the cost of

additional fuel may be heavy unless a heat exchanger is also used. A reheat cycle is shown in
Fig. Considering the adiabatic expansions, the total work done in the two turbines will be equal
to: (I3 – I4a) + (I5 – I6a).
If the combustion gases were expanded in one turbine only down to point 7a for the same
pressure ratio, then the work output would have been: (I3 – I7a).
Now the constant pressure lines on the H-Φ chart diverge away from the origin and converge
towards the origin. Therefore, the line 5–6a will be greater than 4a–7a. Hence reheating
increases, the power output. By reheating, the average temperature of heat addition is raised
resulting in higher output and efficiency of the cycle. If reheat cycle is to be adopted then the
pressure ratio must be high as at low pressure ratios, the thermal efficiency is lowered by
reheating Fig. Reheating reduces the airflow through the cycle resulting in decreased input to
the compressor. For ideal reheating; the working fluid temperature after reheating is equal to
the maximum permissible turbine inlet temperature. That is,
OPERATIONS AND MAINTENANCE PERFORMANCE
OPERATION
https://www.youtube.com/watch?v=pEnlUpG9_t0
(a) Starting. Starting sequence of any gas turbine from rest to its rated speed requires a certain

order of events to be accomplished either manually or automatically. The major steps in
sequence are cranking, ignition, acceleration and governing.
The following is typical starting sequence of a gas turbine
1. Application of control power illuminates all the malfunctions lights.
2. Operate ‘Reset switch’ to reset malfunctions circuits: By doing so, malfunction lights go off
and all control devices assume the condition for starting.
3. Operate “Start” switch to initiate starting sequence. By doing this, lube oil pump and cooling
fan start. If there are separate switch for these, operate these.
4. When lube oil reaches a present pressure, the starter is energized and cranking of the engine
begins.
5. With the cranking of starting of starter, the engine and exhausts ducts are purged of any
combustible gases that might be present.
6. During the cranking cycle, the fuel boost pump is used and operated to increase fuel pressure.
7. As soon as the fuel pressure has reached a prescribed minimum value, fuel and ignition
switches are turned on provided a preset turbine speed has been reached.
8. The turbine accelerates due to the combustion of fuel and the assistance of the cranking
motor. At a preset value, say in the order of 70% of rated speed, the starter and ignition are cut
off automatically.
9. The turbine becomes self-sustaining and accelerates on its own to its governed speed till the
governing system takes over the control.
(b) Shut down. To stop the gas turbine fuel supply should be turned off. This is accomplished
by closing the fuel valve either manually or by de-energizing an electrically operated valve. In
cases where sleeve bearings are used, circulation of lube oil to bearings after shutdown is
necessary for cooling.
MAINTENANCE PERFORMANCE
The type of maintenance, which is done on the gas turbine, is the same as that of steam
turbines.
From the experiences of most manufacturers of gas turbine equipment forced outages are
frequently caused-at least in part by inadequate maintenance. The basic purposes of a
preventive maintenance programme are to reduce forced outages.
The following are the principal sub-systems of the gas turbine for which manufacturers present
maintenance instructions:
1. Turbine gear
2. Starting
3. Clutches and coupling
4. Fuel system
5. Pneumatic system
6. Fire protection system
7. Control equipment
8. Generator-exciter
9. Electrical controls
10. Auxillary gear and main gear
11. Gas turbine
12. Lube oil system
13. Over speed protection

14. Temperature control and monitoring systems
15. Air conditioning system
16. Emergency power
17. Motors
18. Related station equipment.
Maintenance is carried out daily monthly, quarterly, semi-annually and annually.
So for the sequence of overhaul is concerned, it is similar to that of steam turbines with some
exceptions.

TROUBLESHOOTING AND REMEDIES
https://www.youtube.com/watch?v=pEnlUpG9_t0&t=411s
Modern gas turbines are usually equipped with a very sophisticated protection system using
microprocessor and computers, which gives a visual and audio alarm when any pre-
established safe condition is violated. In all types of alarm, it is not necessary to shut the gas
turbine down. If an alarm condition is of sufficient duration and magnitude the unit will trip
and shut down automatically.
The following are the principal symptoms of gas turbine malfunctions and the most common
causes of these malfunctions:
(a) Drop in compressor discharge pressure and subsequent drop in load:
1. Dirty intake screens
2. Dirty compressor blades
3. Loss of compressor blades
4. Damaged labyrinth seals
(b) Smoke or dark stack:
1. Burner nozzle-dirty or worn
Puffs of smoke indicate that carbon is building up around the fuel nozzle and then passing
through the turbine creating rapid wear of blades, vanes and shrouds.
2. Uneven distribution of fuel to combustion chambers.
3. Combustion chambers damaged or out of position.
(c) Spread in turbine discharge temperatures:
1. Bad thermocouples
2. Uneven fuel to burners or dirty nozzles
3. Combustion chambers damaged or out of position
4. Unlit burners
5. Damaged burner nozzles
(d) High wheel space temperatures:
1. Cooling airlines plugged
2. Cooling air heat exchanger dirty, leaking water or loss of cooling water.
4. Wheel space seals worn due to rubs by axial movement or rotor (worn thrust bearing),
bowed shaft or casing out of round to open seal clearances
5. Cooling air supply not functioning properly.
(e) High turbine exhaust temperatures:
1. Loss of turbine blades or damaged inlet vanes
3. Exhaust temperature controller out of adjustment
4. Increased blade tip clearances due to radial ribs.
5. Dirty air compressor.

(f ) High Turbine Exhaust Pressure:
1.Turning vanes in turbine discharge duct damaged or missing.
2. Discharge silencer damaged.
(g) Vibration:
1. Indicating instrument out of adjustment
2. Loose shaft couplings
3. Bowed turbine shaft
4. Broken or missing turbine blades
5. Damaged bearings
6. Shaft miss-alignment
(h) Loss of fuel pressure:
1. Fuel control valve out of adjustment
2. Fuel strainers dirty
3. Fuel pump or compressor damaged
(i) Light of failure:
1. Faulty spark plug
2. Combustion chamber cross fire tubes out of place.
3. Electrical control out of adjustment
4. Fuel proportion out of adjustment
5. Fuel atomizing air out of proportion
6. Burner nozzles dirty or worn
7. Combustion chamber damaged
(j) Machine ‘Hunting’:
1. Worn governor and control parts
2. Fluctuating fuel controllers
3. Fluctuating exhaust temperature controllers
4. Hydraulic control valves leaking or strainers dirty.
(k) Loss of oil pressure
1. Filters
2. Pump failure
3. Leakage in pump.

COMBINED CYCLE POWER PLANTS
https://www.youtube.com/watch?v=eeiu-wcyEbs
https://www.youtube.com/watch?v=bnR-CLpZE9I
It has been found that a considerable amount of heat energy goes as a waste with the exhaust
of the gas turbine. This energy must be utilized. The complete use of the energy available to a
system is called the total energy approach. The objective of this approach is to use all of the
heat energy in a power system at the different temperature levels at which it becomes available
to produce work, or steam, or the heating of air or water, thereby rejecting a minimum of energy
waste. The best approach is the use of combined cycles.
There may be various combinations of the combined cycles depending upon the place or
country requirements. Even nuclear power plant may be used in the combined cycles.
Fig. shows a combination of an open cycle gas turbine and steam turbine. The exhaust of gas
turbine which has high oxygen content is used as the inlet gas to the steam generator where the
combustion of additional fuel takes place. This combination allows nearer equality between the
power outputs of the two units than is obtained with the simple recuperative heat exchanger.
For a given total power output, the energy input is reduced (i.e., saving in fuel) and the installed
cost of gas turbine per unit of power output is about one-fourth of that of steam turbine. In
other words, the combination cycles exhibit higher efficiency. The greater disadvantages
include the complexity of the plant, different fuel requirements and possible loss of flexibility
and reliability. The most recent technology in the field of co-generation developed in USA
utilizes the gaseous fuel in the combustion chambers produced by the gasification of low
quality of coal. The system is efficient and the cost of power production per kW is less.
APPLICATIONS OF GAS TURBINE
1. Gas turbine plants are used as standby plants for the hydro-electric power plants.
2. Gas turbine power plants may be used as peak loads plant and standby plants for smaller
power units.
3. Gas turbines are used in jet aircrafts and ships. Pulverised fuel fired plants are used in
locomotive.

Advantages of gas turbine power plant:
1. Warm up time: Once the turbine is brought up to rated speed by starting the motor and fuel
is ignited, the GT will accelerate to full load without warming up.
2. Low weight to size: The weight of GT per kW output is low, which is a favourable feature
in all vehicles.
3. Fuel flexibility: Any hydrocarbon fuel from high octane gasoline to heavy diesel oil and
pulverized coal can be used efficiently.
4. Floor space: Because of its small size, the floor space required for its installation is less.
5. Start up and shut down: A GT plant can be started up as well as shut down very quickly.
Thus suitable for peak load demand for certain region.
6. High efficiency: Suitable blade cooling permits use of high GT inlet temperature yielding
high thermal efficiency (around 30%).
7. Combined cycle mode: A GT power plant can be used in conjunction with a bottoming
steam plant in combined cycle mode to yield overall fuel to electricity efficiency of 55%.
8. Cooling water: The cooling water requirement is not much. Hence water availability is not
a restriction in installation of GT plant.
9. Ash disposal: In thermal power station ash disposal from site poses serious problem. This
is not so in GT power plant.
10. Transmission loss: It can be located in the load centre itself. Therefore, transmission loss
is minimal.
11. Installation cost: installation cost is less compared to thermal plant. Only foundation is
required. The plant comes from the factory to site, almost fully assembled.
12. Scope of cogeneration: GT plants are used to produce process heat for various uses.
13. Low capital cost: The capital cost per kW is considerably less than a thermal plant.
Disadvantages of gas turbine power plant:
1. Part load efficiency is low.
2. Highly sensitive to component efficiency like compressor and turbine efficiency.
3. The efficiency depends upon ambient condition (ambient temperature and pressure).
4. High air rate is required to limit the maximum GT inlet temperature; as a result, exhaust loss
is high.
5. Large compressor work is required, which tells upon efficiency of the plant.
6. Air and gas filter should be off high quality so that no dust enters to erode or corrode turbine
blade.

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