Gas Turbines - A Presentation
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Transcript of Gas Turbines - A Presentation
GAS TURBINES
P.MAHADEVAN
Objective
• Comprehend the thermodynamic processes occurring in a gas turbine
• Comprehend the basic components of gas turbines and their basic operation
• Comprehend the support systems associated with gas turbines
What is Gas Turbine?
• Energy converter• Chemical Energy to Mechanical EnergyFUNCTION
Prime Mover - Provide Power for movement / transportation
• Mechanical drive (Compressors, Pumps, Blowers)
• Electricity Generation (Generator)
What is Gas Turbine?
It’s an high technology engine It’ an high speed rotating machine (3.000-30.000 rpm) In industrial application may drive generators(GD =
Generator Drive) or pumps and compressors (MD = Mechanical Drive)
It’s used for mobile application as aircraft ships etc. Power range of gas turbine is between 100 kW and 350 MW It’s efficiency is between 25% and 40% High specific power (light and powerful machine) May use a large typology of fuels (gas and liquid types) It may operate continuously without stop also for one year
WHY GAS TURBINE ?
High efficiency Low emissions Low installed cost Low cost power generation Short lead time, modular Multi-fuel capabilities
HISTORICAL PERSPECTIVE
Man tried to develop some turbo machine right from BC days
Claude Burdin (1790-1873) was the first to use the word “turbine” derived from the Latin word “turbo” (spins)
Stolze developed the first gas turbine in 1872 First successful stationary gas turbine operation in 1940
HISTORICAL PERSPECTIVE (Contd)
150 BC - Hero - earliest example of jet propulsion 1500 AD - Leonardo da Vinci – sketch 1629 - Giovanni Branca - first practical application of a
steam turbine 1765 - Reciprocating Steam Engine invented by James Watt 1791 - John Barber - first patent for a turbine engine 1827 -1840 - Hydraulic Turbine 1872 - Stolze - first true gas turbine 1883 - Steam Turbine by De laval 1939 - Heinkel Aircraft Co. - credited for the first flight of a
gas turbine powered jet propelled aircraft 1959 - Gas turbines first used as emergency power
generation
Gas Turbines in Oil and Gas Applications
Principal GT Application Areas:Upstream a) Oil Field and Offshore Power Generation b) Gas Lift (Enhanced Oil Recovery -EOR) c) Water Injection f) Export Compression g) Gas Gathering h) Gas Plant and Gas Boost i) Gas Storage/Withdrawal
Gas Turbines in Oil and Gas Applications (Contd)
Midstream a) Pipeline Compression b) Oil Pipeline Pumping c) LNG Plant (refrigeration,
compression, power)
Gas Turbines in Oil and Gas Applications (Contd)
Downstream a) Refinery power (Steam and Power
Cogeneration) b) Refinery Integrated Gasification
Combined Cycle c) Methanol / Fischer-Tropsch /
Ethanol Fueled Plants
Brayton CycleOpen cycle, unheated engine 1-2: Adiabatic compression of air in compressor 2-3: Constant pressure burning (Combustion) in a combustor 3-4: Adiabatic Expansion through Turbine and Exhaust Nozzle (4-1: Atmospheric Pressure)
Basic Components
Basic Components
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
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
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
CompressorSupplies high pressure air for combustion processCompressor types–Radial/centrifugal flow compressor–Axial flow compressor
Compressor Types 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
Axial Compressor Operation
COMPRESSOR
is the part of theengine where air iscompressed
Compressor Discharge:(1) 30% for primary air (combustion air)(2) 5% operation of gas turbine accessories:
-bleed air and seal air-gas turbine start and motor air-gas turbine anti-icing
(3) remaining air is used as secondary air to:- cool combustion gases- Provide film cooling of the gas generator turbine
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
COMPRESSED AIR
Combustion Chambers Where air & fuel are mixed, ignited, and burned Spark plugs used to ignite fuel Types
Tubular (Single Can)Preferred by European manufacturersSimple design, long life
Annular: for larger, axial compressors Popular in aircraft designs
Can-annular: for really large turbinesPreferred by American manufacturersMost common type, ease of maintenance
TUBULAR TYPES
SINGLE CAN COMBUSTOR
CAN ANNULAR COMBUSTOR
Combustor Types
Another Classification Standard Combustor Dry Low Nox (DLN)
Combustor
Combustion Chamber(s) Operation
is the part of the engine where air is mixed with fuel and burned
COMBUSTOR(s)
Typical Gas Turbine Combustor
Conventional GT Fuel Nozzle
Gas Fuel
Liquid FuelAtomizing Air
Primary Air
Primary Air
Dual Fuel Nozzle Assembly
Turbine Operation
TURBINE
The turbine extract kinetic energy from the expanding gases as the gases comefrom the burner, converting this energy into shaft power to drive the compressorand the engine accessory.Nearly three fourths of all energy available from the product of combustion isneeded to drive the compressors.The turbine is composed from a ring of stator vanes called NOZZLE and a ring ofrotor blades called BUCKETS
Turbines
Consists of one or more stages designed to develop rotational energy
Uses sets of nozzles & blades
Single Shaft Gas TurbinesSingle Shaft Gas Turbine
(with Shaft Coupling):Power Turbine and Gas Generator Turbine on Same ShaftFixed Speed Applications (Range: 90%-100% Full Speed)Mostly used for Electric Power Generation; i.e., Generator Drive via Gearbox (1500 rpm –50 Hz, 1800 rpm – 60 Hz)
SINGLE SHAFT GAS TURBINE
COMBUSTIBILE
AIR
LOAD
COMBUSTORS
EXHAUST GAS
4
3
2
1
TURBINE
AXIAL
COMPRESSOR
AUXILIARY GEARBOX
STARTING MOTOR
60 MW 120 MW 60 MW(50%) (100%) (50%)
1-2 AIR COMPRESSION2-3 COMBUSTION3-4 EXPANSION
LOAD = ELECTRIC GENERATOR (OFTEN) COMPRESSOR, PUMP(NOT COMMON)AUXILARY GEAR BOX= DRIVES OIL PUMPS AND TRANSMITSTORQUE FROM STARTING MOTOR
Single Shaft Gas Turbines
Two-Shaft Gas Turbines
Two-Shaft Gas Turbine (no Shaft Coupling):Power Turbine Independently Supported on its Own Shaft and BearingsVariable Speed Applications (Range 25%-100% Full Speed)Used for Compressor, Pump and Blower Applications
Gas Generator Power Turbine
Types of Couplings
Gear Couplings
Grid-type
Pin-type
Coupling Guards – Non sparking
GEARS
Power Transmission System–Reduction gears used to transfer torque–With split shaft, turbines can run @
different speedsLoad Gear
–Between driver GT and driven equipment
Accessory Gear–For pumps and / or starter
GAS TURBINE TYPES
Industrial Heavy-Duty Aero Derivative Medium Range Small
Industrial Heavy Duty Gas Turbines
Designed shortly after World War II and introduced to the market in early 1950s
Design Characteristics; Heavy wall horizontally split casing, sleeve bearings, large dia combustors, thick airfoil sections for blades and stators
Advantages: Long life, high availability, slightly higher overall efficiencies, Comparatively low noise level
Primarily used in Power plants. Ideal for base load operation
Aero Derivative Gas Turbines
An aircraft-derivative gas generator and a free-power turbine
The gas generator is an aircraft engine modified to burn industrial fuel
Mostly used by gas transmission companies and on gas reinjection platforms
Advantages: favourable installation cost, Adaptation to remote control
Medium Range Gas Turbines
Ratings between 5000-15000 hp Design similar to Heavy Duty GTs Mainly used on offshore platforms and
petrochemical plants
SIMPLE CYCLE
Gas Turbine exhaust gas heat is wasted to the atmosphere
COMBINED CYCLE
Use Gas Turbine Exhaust Heat to Generate Steam in HRSG Use Steam from HRSG to drive steam
turbine generator
COMBINED CYCLE
COMBINED CYCLE
COMBINED CYCLE
Gas Turbine Generator
Stack Bypass Stack
Boiler
Economizer
Supplementary Duct Firing
CLOSED CYCLE APPLICATION
FACTORS AFFECTING GT PERFORMANCE
PRIMARY FACTORS- ambient temperature - ambient pressure (site elevation)
SECONDARY FACTORS- humidity - inlet system pressure drop - exhaust system pressure drop - power losses in the driven equipment (gear, pipeline
compressor or electric generator)
EFFECT OF AIR INLET TEMPERATURE
EFFECT OF AIR INLET TEMPERATURE
EFFECT OF ELEVATION
EFFECT OF INLET LOSS
EFFECT OF EXHAUST LOSS
EFFECT OF INLET LOSS
-100 -75 -50 -25 0 25 50 75 100Change in Inlet Ducting Loss mmH2O
0.98
0.99
1.00
1.01
1.02
Par
amet
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aram
eter
@ G
/Tee
Con
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n
Power Output
Heat Input
Exhaust Temperature
Datum conditions of:Engine inlet temperature 15 °CAmbient pressure 101.3 kPaRelative humidity 60 %Inlet duct loss 100 mmH2OExhaust duct loss 200 mmH2OBased on 'dry' operation in full base load region
EFFECT OF EXHAUST LOSS
-200 -150 -100 -50 0 50 100 150 200Change in Exhaust Ducting Loss mmH2O
0.98
0.99
1.00
1.01
1.02
Para
met
er/P
aram
eter
@ G
/Tee
Con
ditio
n
Power Output
Heat Input
Exhaust Temperature
Datum conditions of:Engine inlet temperature 15 °CAmbient pressure 101.3 kPaRelative humidity 60 %Inlet duct loss 100 mmH20Exhaust duct loss 200 mmH2OBased on 'dry' operation in full base load region
5/11/97 21/08/02
EFFECT OF INLET & EXHAUST LOSS
EFFECT OF ELEVATION
Effect of Relative humidity
-40 -30 -20 -10 0 10 20 30 40Change in Relative Humidity %
0.997
0.998
0.999
1.000
1.001
1.002
1.003
Par
amet
er/P
aram
eter
@ G
/Tee
Con
ditio
n
Exhaust Temperature
Power Output Datum conditions of:Engine inlet temperature 15 °CAmbient pressure 101.3 kPaRelative humidity 60 %Inlet Ducting Loss 100 mmH2OExhaust Ducting Loss 200 mmH2O
Heat Input
GAS TURBINE RATING
ISO RATINGPower rating at design speed and at sea level i.e. Ambient pressure is 14.7
psia (1.0 bar) with an ambient temperature of 59ºF (15ºC) and ambient relative humidity of 60% The ISO rating considers inlet and outlet losses to
be zero.
GAS TURBINE PACKAGE
Gas Turbine Package Components
Gas Turbine Package Components
INSIDE THE PACKAGE Fuel System
- Natural Gas- Liquid (pumped)
Lube Oil System - Supply bearings and gears with oil- Tank- Filter-Pumps (main, pre/post, backup)
Starter (pneumatic, hydraulic, AC motor, diesel engine) Controls (on-skid, off-skid) Seal Gas System (compressors)
Gas Turbine Package ComponentsOUTSIDE THE PACKAGE Enclosure
Fire ProtectionVentilation air inletVentilation exhaustVentilation Fans
Air Inlet System – combustion air Air-filter (self-cleaning, barrier,
inertial)Silencer
Exhaust SystemSilencerStack
Lube Oil Cooler (water, air) Motor Control Center Switchgear, Neutral Ground
Resistor Inlet Fogger/Cooler Fire Protection cabinet
FUEL SYSTEM
The purpose of the fuel system is to deliver fuel to the individual combustors of the turbine under the following conditions:At the required pressure and temperatureIn the right quantity to meet the load demandFree of contaminants, which may be harmful to the turbine
FUEL SYSTEM (Contd)
The fuel system may beGaseous fuelLiquid fuelDual fuel
FUEL SYSTEM (Contd)
The fuel system can be divided into:The combustion control system
located on base at the turbineThe fuel receiving, storage and
forwarding system
TYPICAL FUEL GAS SYSTEM
TYPICAL LIQUID FUEL STORAGE & FORWARDING SYSTEM
TYPICAL TURBINE LIQUID FUEL SYSTEM
DUAL FUEL SYSTEM
DUAL FUEL NOZZLE
TYPICAL ATOMIZING & PURGE AIIR SYSTEM
Wobbe Index
It is customary to give a Wobbe number without units–even though it has the dimensions Btu per scf–because to do so would lead to confusion with the volumetric heating value of the gas.
The usefulness of the Wobbe number is that for any given orifice, all gas mixtures that have the same Wobbe number will deliver the same amount of heat.
The Wobbe Index (WI) is the main indicator of the interchangeability of fuel gases
It is used to compare the combustion energy output of different composition fuel gases
Less than 5% deviation is desired
LUBRICATING & HYDRAULIC OIL SYSTEMS
The purpose of the lube oil system is to supply the lubricant to the bearings and gear box At the right pressure At the right temperature Clean and free from dirt, dust or material particles
The lube oil system works on a closed cycle
TYPICAL LUBE OIL SYSTEM
LUBE OIL SUMP
TURBINE GENERATOR
TYPICAL GTG LUBE OIL SYSTEM
TYPICAL CONTROL (TRIP) OIL SYSTEM
TYPICAL HYDRAULIC OIL SYSTEM
Starting System
Purpose– To get compressor initially rotated– Once at certain RPM, fuel injected and spark
ignited Types
– Electric motor– Diesel engine– Gas Expander/ pneumatic starter
STARTER ARRANGEMENT
Air Intake & Exhaust
Must minimize space and weight Must keep air inlet losses to a
minimum to ensure maximum performance Intake has screens/filters to ensure
clean, filtered air at all times
INLET AIR FILTER TYPES
Self Cleaning Filter
Air Intake Filter
Exhaust Exhaust generates thermal and
acoustic problems– Possible damage to personnel &
equipment Silencers and eductor nozzles used to
silence and cool exhaust Exhaust orientation – axial or
transverse
TYPICAL COOLING WATER SYSTEM
GT ENCLOSURE
TYPICAL GT ENCLOSURE
GT ENCLOSURE (Contd)
Requirements: Acoustic Weatherproof Fire protection Ventilation Lighting Doors
TYPICAL GT COMPARTMENT VENTILATION
FIRE PROTECTION
Fire DetectionTypes of Detectors Ultraviolet (UV) Infrared (IR) Rate Compensated ThermalFire SuppressionTypes of agents Halon CO2 – High Pressure or Low Pressure Inergen Water MistGas detection Infrared (IR) Electro catalytic
Typical CO2 Fire Protection System
TYPICAL CONTROL PANEL
HOT END DRIVE
GENERATORGEARBOX
Air Inlet
Compressor
Combustor
TurbineExhaust
BASE FRAME
MATERIALS OF CONSTRUCTION
Alloy steels for compressor & turbine Nickel or Cobalt based alloys for combustor Stainless Steel for Combustion Air Intake and
Lube Oil Systems.
HOT END DRIVE
COLD END DRIVE LAYOUT
TYPICAL TURBINE START UP CURVE
TYPICAL GT LOADING CURVE
ABNORMAL CONDITIONS THAT REQUIRE GAS TURBINE TRIP
– Over speed. – Low lube oil pressure. – High turbine exhaust temperature. – Excess vibration. – Flame failure in combustor. – Inlet air filter having high differential pressure.– Any initiation of fire protection around the unit.– Gas leak detection
Service life of Gas Turbine Components
Factors that may determine the service life of gas turbine components:
– starts and stops – load and temperature swings – running hours – whether components have protective coatings – material creep strength – endurance limit for fatigue strength evaluation – method of blade cooling – effect of steam injection– erosion wear noted during inspections
PERFORMANCE DEGRADATION
All turbomachinery experiences losses in performance with time.
RecoverableUsually associated with compressor fouling and can be partially rectified by water washing or by mechanically cleaning the compressor blades and vanes after opening the unit
Non-recoverable lossis due primarily to increased turbine and compressor clearances and changes in surface finish and airfoil contour
TYPICAL MAINTENANCE
INSPECTION TYPE
INTERVAL (EOH) DOWNTIME
COMBUSTION INSPECTION 16,000 7 DAYS
HOT GAS PATH INSPECTION
32,000 16 DAYS
MAJOR INSPECTION 64,000 25 DAYS
Turbine Performance Degradation Curves*
Turbine Performance Degradation Curves*
WATER WASH SYSTEM
On Line Wash Off line Wash With or Without detergent Water quality Fixed or mobile
EMISSIONS
EMISSIONS CONTROL – ON ENGINE
Temperature Effects on CO/NOx
AIRFLOW
60%
40%AIRFLOW
30%
70%
FUEL
FUEL
Conventional
Lean Pre-mixed
Same Turbine Inlet Temp.
Diffusion vs. Pre-Mixed
©Solar Turbines Incorporated
2900°F1870 K
4100°F2530 K
Catalytic Combustor
EMISSIONS CONTROL – OFF ENGINE
– Inlet Fogging & “Wet Compression”– Selective Catalytic Reduction (SCR)– Oxidation Catalysts for CO removal– SCONOx
Inlet Fogging & “Wet Compression”
SCONOx
SCR UNITS
GT APPLICATION CONSIDERATIONSOil & Gas Requirements:– Availability / Reliability– Ruggedness– High Power/Weight ratio– Efficiency not Critical
Industrial Power GenerationRequirements:– Cost of Electricity– Efficiency– Cost of O&M
INDUSTRY STANDARDS
STANDARD TITLEAPI 616 Gas Turbines for the Petroleum, Chemical, and Gas
Industry Services
ASME PTC 22 Performance Test Code on Gas Turbines
API 613 Special Purpose Gear Units for Petroleum, Chemical and Gas Industry Services
API 614 Lubrication, Shaft Sealing And Control Oil Systems For Special Purpose Applications
API 670 Non-contacting Vibration And Axial Position Monitoring System
API 671 Special-purpose Couplings For Refinery Services
FURTHER READINGBOOKS Gas Turbine Theory - HIH Saravanamuttoo, G. Rogers and H.
Cohen Sawyer’s Gas Turbine Engineering Handbook Gas Turbine Engineering Handbook – Meherwan P.Boye The Gas Turbine Handbook: Principles and Practices - Tony
GiampaoloJOURNALS Gas Turbine World Hydrocarbon Processing Power EngineeringINTERNET Vendor Websites
GAS TURBINE VENDORS
GE SOLAR ROLLS ROYCE SIEMENS MAN TURBO
GE GAS TURBINE RATINGS
SOLAR TURBINES
ROLLS-ROYCE