Unit2 diesel engine power plant

DIESEL ENGINE POWER PLANT
APPLICATIONS OF DG SETS
PEAK LOAD PLANT
MOBILE PLANT
STAND BY UNIT
EMERGENCY PLANT
NURSERY STATION
STARTING STATION
CENTRAL STATION
S.PALANIVEL ASSOCIATE PROF./MECH ENGG
KAMARAJ COLLEGE OF ENGG.&TECH. (NEAR) VIRUDHUNAGAR

ADVANTAGES OF DIESEL ENGINE POWER PLANT
• EASY TO DESIGN & INSTALL
• EASILY AVAILABLE IN STANDARD CAPACITIES
• RESPOND TO LOAD VARIATION SMOOTHLY
• LESS STANDBY LOSSES
• OCCUPY LESS SPACE
• STARTED & STOPPED QUICKLY
• REQUIRE LESS COOLING WATER
• LESS CAPITAL COST
• LESS OPERATING & SUPERVISING STAFF
• EFFICIENCY IN PART LOADS HIGHER
• NO ASH HANDLING PROBLEM
• EASIER LUBRICATION SYSTEM
• LESS CIVIL ENGG. WORKS

DISADVANTAGES OF DIESEL ENGINE POWER PLANT
• HIGH OPERATING COST
• HIGH MTCE & LUBRICATION COST
• CAPACITY IS RESTRICTED
• NOISE PROBLEM
• CANNOT SUPPLY OVERLOAD
• UNHYGENIC EMISSION

DIESEL POWERPLANT LAYOUT

DIESEL ENGINE POWER PLANT
• ENGINE
• AIR INTAKE SYSTEM
• EXHAUST SYSTEM
• FUEL SYSTEM
• COOLING SYSTEM
• LUBRICATING SYSTEM
• STARTING OF ENGINE

Fuel Injection System`
Functions
1.Filter the fuel
2.Meter the correct quantity of injected fuel
3.Time the injection process injected
4.Regulate the fuel supply
5.Secure fine atomization of fuel
6.Distribute the atomized fuel in Combustion
chamber

Oil atomization
• Air blast fuel atomization ;l Compressed air
at 70 bar used to atomize & inject fuel. For
this Compressor and storage tank required
which is expensive.
• Solid Injection : Fuel oil is forced to flow thro
spray nozzles at a pressure of above 100 bar.
a) Common rail injection system
b) Individual pump injection system
c) Distributor system.

Common Rail Injection system
• A single pump supplies fuel under pressure to
fuel header or common rail.
• High pressure in the header forces the fuel to
each of the nozzles located in the cylinder
• At the proper time, a mechanically operated
valve allows fuel to enter cylinder thro nozzle
• The amount of fuel entering cylinder is
regulated by varying the length of the push
rod stroke.

Fuel oil injection system (contd.)
• Individual pump injection system
• Distributor system

Cooling & Lubricating System
• THERMO SIPHON COOLING
• THERMOSTAT COOLING
• Splash lubricating system
• Bypass type wet sample lubrication

Comparisons of various Power plants

Classification of gas turbines :
• Gas turbines are classified according to three factors , These are :
1. Combustion process
2. Path of working substance
3. Action of combustion gases in turbine

Classification of Gas turbine
Combustion process Path of Gases
Action of
Gases
Const.
volume
Const. pressure
Impulse Turbine
Impulse-Reaction
Turbine
Open Cycle GT Closed Cycle GT
Semi Closed Cycle GT

25
Brayton Cycle: Ideal Cycle for Gas-Turbine Engines
Gas turbines usually operate on an open cycle (Fig. 9–29).
Air at ambient conditions is drawn into the compressor, where its temperature and
pressure are raised. The high pressure air proceeds into the combustion chamber,
where the fuel is burned at constant pressure.
The high-temperature gases then
enter the turbine where they expand
to atmospheric pressure while
producing power output.
Some of the output power is used to
drive the compressor.
The exhaust gases leaving the
turbine are thrown out (not re-
circulated), causing the cycle to be
classified as an open cycle.

26
The open gas-turbine cycle can be
modelled as a closed cycle, using
the air-standard assumptions (Fig.
9–30).
The compression and expansion
processes remain the same, but the
combustion process is replaced by
a constant-pressure heat
addition process from an external
source.
The exhaust process is replaced by
a constant-pressure heat
rejection process to the ambient
air.
Closed Cycle Model

27
The ideal cycle that the working fluid
undergoes in the closed loop is the Brayton
cycle. It is made up of four internally
reversible processes:
1-2 Isentropic compression;
2-3 Constant-pressure heat addition;
3-4 Isentropic expansion;
4-1 Constant-pressure heat rejection.
The T-s and P-v diagrams of an ideal Brayton
cycle are shown in Fig. 9–31.
Note: All four processes of the Brayton cycle
are executed in steady-flow devices thus,
they should be analyzed as steady-flow
processes.
The Brayton Cycle

28
Thermal Efficiency
The energy balance for a steady-flow process can
be expressed, on a unit–mass basis, as
The heat transfers to and from the working fluid
are:
The thermal efficiency of the ideal Brayton cycle,
is the pressure ratio.where
Constant specific heats

29
The thermal efficiency of an ideal Brayton
cycle depends on the pressure ratio, rp of
the gas turbine and the specific heat ratio,
k of the working fluid.
The thermal efficiency increases with both
of these parameters, which is also the
case for actual gas turbines.
A plot of thermal efficiency versus the
pressure ratio is shown in Fig. 9–32, for
the case of k =1.4.
Parameters Affecting Thermal
Efficiency

30
The early gas turbines (1940s to 1959s) found only limited use despite their
versatility and their ability to burn a variety of fuels, because its thermal efficiency
was only about 17%. Efforts to improve the cycle efficiency are concentrated in
three areas:
1. Increasing the turbine inlet (or firing) temperatures.
The turbine inlet temperatures have increased steadily from about 540°C
(1000°F) in the 1940s to 1425°C (2600°F) and even higher today.
2. Increasing the efficiencies of turbo-machinery components (turbines,
compressors).
The advent of computers and advanced techniques for computer-aided design
made it possible to design these components aerodynamically with minimal
losses.
3. Adding modifications to the basic cycle (intercooling, regeneration or
recuperation, and reheating).
The simple-cycle efficiencies of early gas turbines were practically doubled by
incorporating intercooling, regeneration (or recuperation), and reheating.
Improvements of Gas Turbine’s Performance

31
Actual Gas-Turbine Cycles
Some pressure drop occurs during the
heat-addition and heat rejection processes.
The actual work input to the compressor is
more, and the actual work output from the
turbine is less, because of irreversibilities.
Deviation of actual compressor and
turbine behavior from the idealized
isentropic behavior can be accounted
for by utilizing isentropic efficiencies
of the turbine and compressor.
Turbine:
Compressor:

32
Brayton Cycle With Regeneration
Temperature of the exhaust gas leaving the turbine is
higher than the temperature of the air leaving the
compressor.
The air leaving the compressor can be heated by the
hot exhaust gases in a counter-flow heat exchanger (a
regenerator or recuperator) – a process called
regeneration (Fig. 9-38 & Fig. 9-39).
The thermal efficiency of the Brayton cycle increases
due to regeneration since less fuel is used for the same
work output.
Note:
The use of a regenerator
is recommended only
when the turbine exhaust
temperature is higher than
the compressor exit
temperature.

33
Effectiveness of the regenerator,
Effectiveness under cold-air standard
assumptions,
Thermal efficiency under cold-air
standard assumptions,
Effectiveness of the Regenerator
Assuming the regenerator is well insulated and changes in kinetic and potential
energies are negligible, the actual and maximum heat transfers from the exhaust
gases to the air can be expressed as

34
Thermal efficiency of Brayton cycle
with regeneration depends on:
a) ratio of the minimum to
maximum temperatures, and
b) the pressure ratio.
Regeneration is most effective at
lower pressure ratios and small
minimum-to-maximum temperature
ratios.
Factors Affecting Thermal
Efficiency

35
Brayton Cycle With Intercooling,
Reheating, & Regeneration
The net work output of a gas-turbine cycle
can be increased by either:
a) decreasing the compressor work, or
b) increasing the turbine work, or
c) both.
The compressor work input can be decreased by
carrying out the compression process in stages
and cooling the gas in between (Fig. 9-42), using
multistage compression with intercooling.
The work output of a turbine can be increased by
expanding the gas in stages and reheating it in
between, utilizing a multistage expansion with
reheating.

36
Physical arrangement of an ideal two-stage gas-
turbine cycle with intercooling, reheating, and
regeneration is shown in Fig. 9-43.

37
The work input to a two-stage compressor is minimized when equal pressure
ratios are maintained across each stage. This procedure also maximizes the
turbine work output.
Thus, for best performance we have,
Conditions for Best Performance
Intercooling and reheating always
decreases thermal efficiency unless
are accompanied by regeneration.
Therefore, in gas turbine power
plants, intercooling and reheating are
always used in conjunction with
regeneration.

38
Compare Open cycle and Closed cycle Gas turbines
Open cycle:
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. Open cycle plants occupy comparatively little space.
4. Open-cycle gas turbine power plant, except those having an intercooler, does not
require cooling water.
5. 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.
6. 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.

39
Compare Open cycle and Closed cycle Gas turbines
Contd…
Closed cycle:
1. 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.
3. The need for filtration of the incoming air which is a severe problem in open cycle plant
is completely eliminated.
4. The maintenance cost is low and reliability is high due to longer useful life.
5. The system is dependent on external means as considerable quantity of cooling water
is required in the pre-cooler.
6. The response to the load variations is poor compared to the open-cycle plant

Gas Turbines
• Gas turbines also called combustion turbines, a type
of IC engine in which burning of an air-fuel mixture
produces hot gases that spin a turbine to produce
power.
• It is the production of hot gas during fuel
combustion, not the fuel itself that the gives gas
turbines the name.
• Combustion occurs continuously in gas turbines, as
opposed to reciprocating IC engines, in which
combustion occurs intermittently.

Working
They Work On Brayton Cycle.
 Air is compressed(squeezed) to high pressure by a compressor.
 Then fuel and compressed air are mixed in a combustion
chamber and ignited.
 Hot gases are given off, which spin the turbine wheels

General View of a Gas Turbine

Components Of Gas Turbine
Gas turbines have three main parts:
i)Air compressor
ii) Combustion chamber
iii) Turbine

Air compressor:
The air compressor and turbine are mounted at
either end on a common shaft, with the
combustion chamber between them.
Gas turbines are not self starting. A starting
motor is used.
The air compressor sucks in air and compresses
it, thereby increasing its pressure.

Combustion chamber:
In the combustion chamber, the compressed air
combines with fuel and the resulting mixture is
burnt.
The greater the pressure of air, the better the
fuel air mixture burns.
Modern gas turbines usually use liquid fuel, but
they may also use gaseous fuel, natural gas or
gas produced artificially by gasification of a
solid fuel.

Turbine:
Hot gases move through a multistage gas
turbine.
Like in steam turbine, the gas turbine also has
stationary and moving blades.
The stationary blades
guide the moving gases to the rotor blades
adjust its velocity.
The shaft of the turbine is coupled to a
generator.

APPLICATIONS
drive pumps, compressors and high speed cars.
aircraft and ships.
 Power generation (used for peak load and as
stand-by unit).

Combined Cycle Power Plants
The maximum steam temp. in a power
cycle does not exceed 600 deg.C, although
the temp. in a dry bottom pulversied coal
furnace is about 1300 deg. C.
There fore , there is great thermal
irreversibility and a decrease of availability
because of heat transfer from combustion
gases to steam through a such large temp.
differences.
KAMARAJ COLLEGE OF ENGG. & TECH (NEAR) VIRUDHUNAGAR

• By superposing a high temp. power plant as
a topping unit to the steam power plant, a
higher energy conversion efficiency from
fuel to electricity could be achieved,
• since the combined plant operates through a
higher temp. range.

• Combined cycle plants may be of the
following types
Gas Turbine- Steam Turbine plant
MHD- Steam Plant
Thermionic – Steam plant
Thermoelectric – Steam plant.

• The air standard cycle for a gas turbine
power plant is the Brayton Cycle, which like
Rankine cycle also consists of two reversibile
adiabatics and two reversible isobars,
• but in Brayton cycle working fluid does not
undergo phase change where as in Rankine
cycle, the working fluid is water gets phase
change as steam.

• To overcome GT plant’s low cycle efficiency,
a Gas Turbine may be used in conjunction
with a steam turbine plant in an utility base
load station to offer the utilities the gas
turbine advantages of quick starting and
stopping and permit flexible operation of the
combined plant over a wide range of loads.

Combined Cycle Power Plant

Coal based combined cycle plants
Coal is low grade fuel compared to oil and natural gas, but
reserves of coal are very large, much effort has been
devoted to developing clean coal technologies to reduce
harmful emissions of SOx & Nox.
Successful usage of coals for combined cycle power
generation necessitated the development of firing systems
whose products of combustion have
1.Sufficiently low concentration of particulates to reduce
erosion and ensure a satisfactory life of GT.
2.Sufficiently low concentrations of pollutant gases and
particulates in the exhaust to satisfy environmental
regulation relating to discharges from power plants.

• To reduce the concentration of particulates in products of
combustion before entering the gas turbine, hot clean-up
systems like multi- cyclones, ceramic filters etc. developed.
• To control emission of oxides of sulphur and nitrogen,
different techniques like low NOx burners, staged
combustion, flue gas scrubbing etc. are being put into use.
• Following are two dominant coal based technologies.
1.Pressurised fluidized bed combustion (PFBC) system, which
may be either bubbling fluidized or circulating fluidized bed.
2. Integrated Gasified Combined cycle (IGCC)

PFBC based combined cycle
• This system supplies hot gas at elevated pressure to gas
turbine via hot gas cleanup system.
• Coal and lime stone are supplied to the pressurized
combustor. Limestone is used as the bed material to absorb
sulphur.
• Cooling tubes immersed in the fluidized bed are used to
generate steam which is supplied to steam turbine.
• The combustion products leaving the combustor are passed
through a clean-up system before being expanded in the gas
turbine.
• Exhaust gases are then passed through a heat exchanger
which heats the feed water before being discharged.
• Temp. in PFBC is limited to about 850 deg. C because this is
the most favorable temp of sulphur retention and is below
the ash fusion temp. of coal

Integrated gasification Combined Cycle (IGCC)
• Coal is gasified, either partially or fully and the gas produced
after clean-up is burnt in the combustion chamber of GT. It
is called an integrated gasification combined cycle (IGCC)
• Coal and limestone are fed to a pressure vessel, the coal
being gasified by oxygen and steam. The ash and limestone
form a slag which is discharged and the gas is cooled.
• The use of air instead of oxygen produces a gas of lower
calorific value.
• Exhaust gases from GT raise steam in the HRSG.
• The thermo dynamic performance of an IGCC power plant
shows that there is an optimum pressure ratio for the gas
cycle at a given temp. ratio (T3/T0) for max. cycle efficiency.

IGCC
• An integrated gasification combined cycle (IGCC) is a technology that
uses a high pressure gasifier to turn coal and other carbon based fuels
into pressurized gas—synthesis gas . Impurities removed from the
syngas prior to the power generation cycle.
• Some of these pollutants, such as sulfur, can be turned into re-usable
byproducts through the Claus Process. This results in lower emissions of
Sulfur dioxide, mercury and in some cases Carbon dioxide.
• With additional process equipment, a water gas reaction can increase
gasification efficiency and reduce carbon monoxide emissions by
converting it to carbon dioxide. The resulting carbon dioxide from the
shift reaction can be separated, compressed, and stored through
sequestration.
• Excess heat from the primary combustion and syngas fired generation is
then passed to a steam cycle, similar to a combined cycle gas turbine.
• This process results in improved thermodynamic efficiency compared to
conventional pulverized coal combustion.

Block diagram of IGCC Plant

• The plant is called integrated because
• the syngas produced in the gasification section is used as fuel for
the gas turbine in the combined cycle and
• the steam produced by the syngas coolers in the gasification
section is used by the steam turbine in the combined cycle.
• In this example the syngas produced is used as fuel in a gas
turbine which produces electrical power. In a normal combined
cycle, so-called "waste heat" from the gas turbine exhaust is used
in a Heat Recovery Steam Generator (HRSG) to make steam for
the steam turbine cycle.
• An IGCC plant improves the overall process efficiency by adding
the higher-temperature steam produced by the gasification
process to the steam turbine cycle. This steam is then used in
steam turbines to produce additional electrical power.

Advantages & Disadvantages of IGCC
• IGCC plants are advantageous in comparison
to conventional coal power plants due to
their high thermal efficiency, low non-carbon
greenhouse gas emissions, and capability to
process low grade coal.
• The disadvantages include higher capital and
maintenance costs, and the amount of CO2
released without pre-combustion capture.

Process of IGCC
• The solid coal is gasified to produce syngas, or
synthetic gas.
• Syngas is synthesized by gasifying coal in a closed
pressurized reactor with a shortage of oxygen.
• The shortage of oxygen ensures that coal is broken
down by the heat and pressure as opposed to
burning completely.
• The chemical reaction between coal and oxygen
produces a product that is a mixture of carbon and
hydrogen, or syngas.
CxHy + (x/2)O2 → (x)CO2 + (y/2)H2

• The heat from the production of syngas is
used to produce steam from cooling water
which is then used for steam turbine
electricity production.
• The syngas must go through a pre-
combustion separation process to remove
CO2 and other impurities to produce a more
purified fuel.

• Three steps are necessary for the separation of impurities :
 Water gas shift reaction : The reaction that occurs in a
water-gas-shift reactor is CO + H2O CO⇌ 2 + H2. This
produces a syngas with a higher composition of hydrogen
fuel which is more efficient for burning later in
combustion.
 Physical separation process: This can be done through
various mechanisms such as absorption, adsorption or
membrane separation.
 Drying, compression and storage/shipping.
• The resulting syngas fuels a combustion turbine that
produces electricity. At this stage the syngas is fairly
pure H2. S.PALANIVEL ASSOCIATE PROF./MECH ENGG

Thermodynamics of Brayton – Rankine
combined cycle plant
• Improvising of Brayton Cycle plant by combining with Steam
turbine with Rankine cycle are possible in the following
methods :
• 1.1Two cyclic power plants coupled in series : The topping
plant (GT) operating on Brayton cycle and the bottom one
(ST) operating on Rankine cycle.
• Over all efficiency of the combined plant is given by
=Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2
• WhereȠ1 = Thermal efficiency of Brayton Cycle (GT) and
Ƞ2 = thermal Efficiency of Rankine
• In the above all the heat rejected by the topping plant (GT)
is absorbed by the bottom plant (ST)S.PALANIVEL ASSOCIATE PROF./MECH ENGG

• 1.2 Heat losses between two plants in series : There is
always some heat loss and the heat absorbed is less than the
heat rejected.
• Let QLbe the heat loss between two plants, then the overall
efficiency is =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - Ƞ2XL
• XL= fraction of heat lost (Q1/QL)
• Two cyclic plants operating in parallel : let us consider two
plants operating in parallel , one in Brayton cycle and other
one from Rankine Cycle.
• The total heat supplied Q1 is divided beteen two plants as
Q2 and Q4, so that X1= Q2/Q1 = Q2/(Q2+Q4)
• The overall efficiency of the combined plant
= Ƞ2 + X1(Ƞ1 - Ƞ2 ) ………. AS.PALANIVEL ASSOCIATE PROF./MECH ENGG

• If X2 = Q4/Q1 = Q4/(Q2+Q4)
• The overall efficiency of the combined plant = Ƞ1 -
x2(Ƞ1 - Ƞ2 ) ………. B
• If Ƞ1 > Ƞ2, then >Ƞ Ƞ2 as per A
• <Ƞ Ƞ1 as per B
• Hence lies betweenȠ Ƞ1 and Ƞ2
• Thus no advantage to parallel system.
• If the Cyclic plant 1 operating on Brayton cycle
could absorb more heat say equal to Q1 + Q4, then
it would be advantangeous to use that plant alone.

Series parallel plants with two cyclic plants in
series having supplementary firing
• Let the fraction of the total heat supplied is used for
supplementary heating be X2= Q4/Q1
• overall efficiency is =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - Ƞ1X2(1- Ƞ2 )
• Therefore the overall efficiency of a series – parallel plant
is less than that of two coupled cycles in series since the
last term is positive.
• In the absence of supplementary heating ie. When x2 =0,
the overall efficiency is that of ideal series plant.S.PALANIVEL ASSOCIATE PROF./MECH ENGG

• Series parallel plants with two cyclic plants in series
having supplementary firing and heat loss in
between the two plants:
• Let the fraction of the total heat supplied is used
for supplementary heating be x2= Q4/Q1 and XL
fraction of heat loss to heat supply XL = QL /Q1 ,
where QL = heat loss to surrounding
• Overall efficiency is =Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - XLȠ2-
Ƞ1X2(1- Ƞ2 ) :
• If X2 = 0
=Ƞ Ƞ1 + Ƞ2 - Ƞ1Ƞ2 - XLȠ2

• Combined Cycle Plants with limited supplementary firing :
Supplementary firing raises the temp. of the exhaust gas to
800 to 900 deg. C. relatively high flue gas temp. raises the
condition of steam ( 84 bar, 525 deg.C) there by improving
the efficiency of the steam cycle.
• Combined Cycle Plants with maximum supplementary firing :
Maximum supplementary firing refers to the maximum fuel
that can be fired with the oxygen available in the Gas turbine
exhaust. The use of large supplementary firing in Combined
cycle plants with GT inlet temp. causes the efficiency to drop.
• For this reason Combined cycle plants with maximum
supplementary firing are only of minimal importance in
comparison to simple Combined Cycle plants.

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