Gas turbine power plant

Combustion and Power
Generation
Dr. O.P. TIWARI
H.O.D, Mechanical
Engg.
S.R.I.M.T
S.R.I.M.T
DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,LkoDEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T, Lko

Power Plant Engineering
Classification of Power Plants
Steam (Thermal) Power Plant
Hydro Electric Power plant
Nuclear power Plant
Gas Turbine Power Plant
Diesel Power Plant
S.R.I.M.T
DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko

Gas Power Plant
• A gas power plant uses gas turbine as the
prime mover for generating electricity.
• It uses natural gas or kerosene or benzene as
fuel.
• Gas plant can produce only limited amount of
the electricity.
•Efficiency of the plant is only 35%
S.R.I.M.T

Layout of the Gas turbine Power plant
S.R.I.M.T

5
Types of Gas Turbine Plants
• Simple Cycle
– Operate When Demand is High – Peak Demand
– Operate for Short / Variable Times
– Designed for Quick Start-Up
– Not designed to be Efficient but Reliable
• Not Cost Effective to Build for Efficiency
• Combined Cycle
– Operate for Peak and Economic Dispatch
– Designed for Quick Start-Up
– Designed to Efficient, Cost-Effective Operation
– Typically Has Ability to Operate in SC Mode
S.R.I.M.T

6
Gas Turbine Basic Components
Compressor
Compressor
Turbine
Section
Power
Turbine
Section
S.R.I.M.T

Basic Components
S.R.I.M.T

Basic Components
• Compressor
– Draws in air & compresses it
• Combustion Chamber
– Fuel pumped in and ignited to burn with
compressed air
• Turbine
– Hot gases converted to work
– Can drive compressor & external load
S.R.I.M.T

Compressor
• Compressor types
1.Radial/centrifugal flow compressor
2.Axial flow compressor
3.Supplies high pressure air for combustion
process
S.R.I.M.T

Compressor
• Radial/centrifugal flow
– Adv: simple design,
good for low
compression ratios
(5:1)
– Disadv: Difficult to
stage, less efficient
• Axial flow
– Good for high
compression ratios
(20:1)
– Most commonly used
S.R.I.M.T

Compressor
• Controlling Load on Compressor
– To ensure maximum efficiency and allow for
flexibility, compressor can be split into HP &
LP sections
– Vane control: inlet vanes/nozzle angles can
be varied to control air flow
• Compressor Stall
– Interruption of air flow due to turbulence
S.R.I.M.T

Use of Compressed Air
• Primary Air (30%)
– Passes directly to combustor for combustion
process
• Secondary Air (65%)
– Passes through holes in perforated inner shell
& mixes with combustion gases
• Film Cooling Air (5%)
– Insulates/cools turbine blades
S.R.I.M.T

Blade Cooling
S.R.I.M.T

Gas Turbine Combustion
F/A – 0.01
Combustion efficiency : 98%
S.R.I.M.T

Combustion Chambers
• Where air & fuel are mixed, ignited, and
burned
• Spark plugs used to ignite fuel
• Types
– Can: for small, centrifugal compressors
– Annular: for larger, axial compressors (LM
2500)
– Can-annular: rarely used
S.R.I.M.T

GAS TURBINES
• Invented in 1930 by Frank Whittle
• Patented in 1934
• First used for aircraft propulsion in 1942 on Me262 by
Germans during second world war
• Currently most of the aircrafts and ships use GT engines
• Used for power generation
• Manufacturers: General Electric, Pratt &Whitney,
SNECMA, Rolls Royce, Honeywell, Siemens –
Westinghouse, Alstom
• Indian take: Kaveri Engine by GTRE (DRDO)
S.R.I.M.T

Turbines
• Consists of one or more stages
designed to develop rotational energy
• Uses sets of nozzles & blades
• Single shaft
– Power coupling on same shaft as turbine
– Same shaft drives rotor of compressor
and power components
S.R.I.M.T

Turbines
• Split Shaft
– Gas generator turbine drives compressor
– Power turbine separate from gas generator
turbine
– Power turbine driven by exhaust from gas
generator turbine
– Power turbine drives power coupling
S.R.I.M.T

Dual Shaft, Split Shaft
S.R.I.M.T

Gas Turbine Systems
• Air System
– Air intakes are located high up & multiple
filters
– Exhaust discharged out stacks
• Fuel System
– Uses either DFM or JP-5
• Lubrication System
– Supply bearings and gears with oil
S.R.I.M.T

Brayton Cycle(working cycle)
1-2: Compression
2-3: Combustion
3-4: Expansion through Turbine
and Exhaust Nozzle
4-1: Atmospheric Pressure)
S.R.I.M.T

s
T
1
4
2'
3
2
4'
3'
3''
v
P
1 4
2 3
Closed Brayton
cycle (cont.)
QH
QL
s=const
QH
QL
p=const
S.R.I.M.T

Efficiency of a Brayton cycle
1st
law for this cycle: W Q QH L 
energy conversion efficiency is:
   
useful work
heat input
W
Q
Q Q
QH
H L
H
 
 
    


1 1
4 1
3 2
Q
Q
mC T T
mC T T
L
H
P
P
 
 
  


1
1
1
1 4 1
2 3 2
T T T
T T T
S.R.I.M.T

Efficiency of a Brayton cycle (cont.)
for an isentropic process:
 P P V V
k
1 2 2 1
T
T
P
P
P
P
T
T
k
k
k
k
2
1
1
2
1
3
4
3
4
1




   






 
in case of an ideal gas:
T
T
T
T
3
2
4
1

    







1 11
2
1
2
1
T
T
P
P
k
k
PV P V T T1 1 2 2 1 2
Pv constk

S.R.I.M.T
So…

Efficiency of a Brayton cycle (cont.)
isentropic
pressure
ratio
 
   
1
1
2 1
1
P P
k
k
0
10
20
30
40
50
60
0 5 10 15
Pressure ratio
Thermalefficiency%
Example
S.R.I.M.T

PRINCIPLE OF OPERATION
• Intake
– Slow down incoming air
– Remove distortions
• Compressor
– Dynamically Compress air
• Combustor
– Heat addition through
chemical reaction
• Turbine
– Run the compressor
• Nozzle/ Free Turbine
– Generation of thrust
power/shaft power
S.R.I.M.T

29
 The energy contained in a flowing ideal
gas is the sum of enthalpy and kinetic
energy.
 Pressurized gas can store or release
energy. As it expands the pressure is
converted to kinetic energy.
Principles of
Operation
• Open Cycle
Also referred to as simple cycle)
Link to picture
S.R.I.M.T

heat
exchanger
Closed Brayton cycle
2
1 4
turbinecompressor
Wnet
QH
QL
heat
exchanger
3
S.R.I.M.T

31
Thermodynamic Fundamentals
• Pressure Ratio &
CT Components
S.R.I.M.T

COGENERATION
• Decentralized combined heat and power production-cogeneration is
a very flexible and efficient way of utilizing fuels.
• Cogeneration based on biomass is environmentally friendly, and all
kinds of biomass resources can be used.
• Cogeneration plants can be used in all situations where a given heat
demands exists.
• COGENERATION TECHNOLOGIES
• Gas Engines.
• Gas Turbines.
• The Stirling Engine.
S.R.I.M.T

Brayton cycle
with regeneration
turbine
exhaust
compressor
air
intake
combustion
chamber
fuel
Wnet
regenerator
x
1
2
3
y
regenerator
S.R.I.M.T

Modified Brayton cycle
turbines
exhaust
compressors
combustion
chamber
regenerator 9
8
1
5
6 7
10
fuel
air
intake
2 3
intercooler
4
S.R.I.M.T

Modified Brayton cycle
• multi-stage compression with intercooling
• multi-stage expansion with reheat
s
T
3
8
4
7
1
6
5
2
9
10
S.R.I.M.T

AUXILIARY SYSTEMS
• Auxiliary systems are the backbone of the gas turbine plant. Without
auxiliary system, the very existence of the gas turbine is impossible.
1.STARTING SYSTEMS : Two separate systems-starting and
ignition are required to ensure a gas turbine engine will start satisfactorily.
• Types of Starter :-The following are the various types of gas turbine
starter.
• (a) Electrical :-(i) A.C. and (ii) D.C.
• A.C. cranking motors are usually 3 phase induction types rated to
operate on the available voltage and frequency.
• D.C. starter motor takes the source of electrical energy from a bank of
batteries of sufficient capacity to handle the starting load. Engaging or
disengaging clutch is used.
S.R.I.M.T

• (b) Pneumatic or Air Starter :-Air starting is used mostly as it
is light, simple and economical to operate. As air starter motor has a
turbine rotor that transmits power through a reduction gear and clutch to
the starter output shaft that is connected to the engine.
• (c) Combustion Starter. It is in every respect a small gas turbine.
It is a completely integrated system which incorporates a planetary
reduction gear drive with over-running clutch.
• (d) Hydraulic Starting Motor. It consists of a hydraulic starter motor
for main engine, an accumulator, a hydraulic pump motor for auxiliary
power unit (A.P.U.).
• 2 .IGNITION SYSTEMS :-Ignition system is utilized to initiate spark
during the starting. Once it starts, the combustion is continuous and the working of
ignition system is cut-off automatically .
• The following are the types of ignition system.
1. Capacitor discharge system.
(a) High tension system and (b) Low tension system.
2. Induction system.
3. A. C. power circuits.
S.R.I.M.T

LUBRICATION SYSTEM
• Elements of Lubrication System:-The
following are the elements of lubrication system of a gas turbine
• 1. Oil tank,
• 2. Oil pump
• 3. Filter and strainer,
• 4. Relief valve,
• 5. Oil cooler,
• 6. Oil and pipe line,
• 7. Magnetic drain plug,
• 8. By-pass, valve, and
• 9. Warning devices.
S.R.I.M.T

Fig:-Lubrication System for gas turbine
S.R.I.M.T

CONTROL OF GAS TURBINES
• The purpose of gas turbine controls is to meet the specific control requirements
of users and safe operation of the turbine. There are basically two types of
controls. They are as follows:-
• (A) Prime control and
• (B) Protection control
1.PRIME CONTROL
• The objective of the prime control is to ensure the proper application of the
turbine power to the load.
• The users of the gas turbines have specific control requirements according the
use of gas turbines . The requirements might be to control:
• (1) The frequency of an a.c. generator,
• (2) The speed of a boat or ship,
• (3) The speed of an aircraft,
• (4) The capacity or head of a pump or compressor,
• (5) The road speed of a vehicle.
S.R.I.M.T

Fig-prime control (hydro-mechanical)
S.R.I.M.T

2.PROTECTIVE CONTROLS:- The objective of
the protective control is to ensure adequate protection for the
turbine in preventing its operation under adverse conditions.
Basically, the protective control is of two types:-
• 1. Shutdown control and
• 2. Modulating control
• 1. Shut Down Control
The shut down type control detects a condition which can cause a serious
malfunction and actuate the shut-off valve to stop the turbine following are the
various types of shut down controls.
• (a) Turbine over temperature,
• (b) Turbine over speed,
• (c) Low lube oil pressure,
• (d) High lube oil temperature, and
• (e) excess vibration.
S.R.I.M.T

• (2) Modulating Controls
• The purpose of modulating control is to sense an impending malfunction or
a condition, which could adversely affect turbine life and make some
modification to the operating condition of the turbine in order to alleviate
the undesired conditions.
S.R.I.M.T

Engine Power Transfer
• Turbojet
• Thrust provided by reaction against expansion of
exhaust gases
• Turbofan
• Thrust provided by reaction against expansion of
large volumes of air
• Marine systems
• Thrust provided by turbine
• SCRAMjet/RAMjet
S.R.I.M.T

45
Combustion Turbine Fuels
• Conventional Fuels
– Natural Gas
– Liquid Fuel Oil
• Nonconventional Fuels
– Crude Oil
– Refinery Gas
– Propane
• Synthetic Fuels
– Chemical Process
– Physical Process
S.R.I.M.T

Emission in Gas Turbines
•Lower emission compared to all conventional methods (except nuclear)
•Regulations require further reduction in emission levels
S.R.I.M.T

S.R.I.M.T

What is the CCGT?
A combined cycle gas turbine power plant,
frequently identified by CCGT shortcut,is
essentially an electrical power plant in
which a gas turbine and a steam turbine
are used in combination to achieve
greater efficiency than would be possible
independently.
The gas turbine drives an electrical
generator.The gas turbine exhaust is then
used to produce steam in a heat
exchanger (steam generator) to supply a
steam turbine whose output provides the
means to generate more electricity.
However the Steam Turbine is not
necessarily, in that case the plant produce
electricity and industrial steam which can
be used for heating or industrial
purpose.
S.R.I.M.T

49Picture courtesy of Nooter/Eriksen
How does a Combined Cycle Plant Work?
S.R.I.M.T

50
Combining the Brayton and Rankine Cycles
• Gas Turbine Exhaust used as the heat source for the Steam
Turbine cycle
• Utilizes the major efficiency loss from the Brayton cycle
• Advantages:
– Relatively short cycle to design, construct & commission
– Higher overall efficiency
– Good cycling capabilities
– Fast starting and loading
– Lower installed costs
– No issues with ash disposal or coal storage
• Disadvantages
– High fuel costs
– Uncertain long term fuel source
– Output dependent on ambient temperature
S.R.I.M.T

51
Combined Cycles Today• Plant Efficiency ~ 58-60 percent
– Biggest losses are mechanical input to the compressor and heat in the
exhaust
• Steam Turbine output
– Typically 50% of the gas turbine output
– More with duct-firing
• Net Plant Output (Using Frame size gas turbines)
– up to 750 MW for 3 on 1 configuration
– Up to 520 MW for 2 on 1 configuration
• Construction time about 24 months
• Engineering time 80k to 130k labor hours
• Engineering duration about 12 months
• Capital Cost ($900-$1100/kW)
• Two (2) versus Three (3) Pressure Designs
– Larger capacity units utilize the additional drums to gain efficiency at
the expense of higher capital costs
S.R.I.M.T

52
Combined Cycle Efficiency
• Simple cycle efficiency (max ~ 44%*)
• Combined cycle efficiency (max ~58-60%*)
• Correlating Efficiency to Heat Rate (British Units)
 = 3412/(Heat Rate) --> 3412/ = Heat Rate*
– Simple cycle – 3412/.44 = 7,757 Btu/Kwh*
– Combined cycle – 3412/.58 = 5,884 Btu/Kwh*
• Correlating Efficiency to Heat Rate (SI Units)
 = 3600/(Heat Rate) --> 3600/ = Heat Rate*
– Simple cycle – 3600/.44 = 8,182 KJ/Kwh*
– Combined cycle – 3600/.58 = 6,207 KJ/Kwh*
• Practical Values
– HHV basis, net output basis
– Simple cycle 7FA (new and clean) 10,860 Btu/Kwh (11,457 KJ/Kwh)
– Combined cycle 2x1 7FA (new and clean) 6,218 Btu/Kwh (6,560 KJ/Kwh)
*Gross LHV basis
S.R.I.M.T

53
Gas Turbine Generator Performance
Factors that Influence Performance
– Fuel Type, Composition, and Heating Value
– Load (Base, Peak, or Part)
– Compressor Inlet Temperature
– Atmospheric Pressure
– Inlet Pressure Drop
• Varies significantly with types of air cleaning/cooling
– Exhaust Pressure Drop
• Affected by addition of HRSG, SCR, CO catalysts
– Steam or Water Injection Rate
• Used for either power augmentation or NOx control
S.R.I.M.T

Advantages and Disadvantages
• Lower emission levels
• Great power-to-weight
ratio compared to
reciprocating engines.
• Smaller than their
reciprocating
counterparts of the
same power.
• Expensive:
– high speeds and high operating
temperatures
– designing and manufacturing
gas turbines is a tough problem
from both the engineering and
materials standpoint
• Tend to use more fuel when
they are idling
• They prefer a constant rather
than a fluctuating load.
That makes gas turbines great for things like transcontinental jet aircraft and
power plants, but explains why we don't have one under the hood of our car.
S.R.I.M.T

Needs for Future Gas Turbines
• Power Generation
– Fuel Economy
– Low Emissions
– Alternative fuels
• Military Aircrafts
– High Thrust
– Low Weight
• Commercial Aircrafts
– Low emissions
– High Thrust
– Low Weight
– Fuel Economy
Half the size and twice the thrust
Double the size of the Aircraft
and double the distance traveled
with 50% NOx
S.R.I.M.T

Ongoing Research
• Effect of inlet disturbances
• Combustion in recirculating flows
• Spray Combustion
–Needs and Challenges
–Controlled atomization
–Emissions in spray combustion
S.R.I.M.T

THANK YOU
S.R.I.M.T

Gas turbine power plant

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Gas turbine power plant

Semelhante a Gas turbine power plant (20)

Último

Último (20)

Gas turbine power plant