gas turbine - part 1

Gas Turbine SystemPart 1 – Gas Turbine Proper

PurposePurpose Used to generate electrical power for Used to generate electrical power for

transmission to the grid.transmission to the grid. Prime mover of the Electrical GeneratorPrime mover of the Electrical Generator

FlowpathFlowpath Model 7FAModel 7FA Rated output of 200,000 kva at a power Rated output of 200,000 kva at a power

factor of 0.85 factor of 0.85 Real power output is Real power output is

• 200,000 kva x 0.85 pf = 170 MW200,000 kva x 0.85 pf = 170 MW Actual output can be limited by generator Actual output can be limited by generator

temperature.temperature. Uses Dry Low Nox Burners (version 2.6)Uses Dry Low Nox Burners (version 2.6)

FlowpathFlowpath Recall the simplified Recall the simplified

figure of the Gas figure of the Gas TurbineTurbine

Air is compressed, Air is compressed, ignited (combusted), ignited (combusted), and expanded and expanded before flowing before flowing through an HRSG.through an HRSG.

Inlet air filter Inlet air filter assembly is used to assembly is used to clean the airclean the air

FlowpathFlowpath

The inlet filter cleans The inlet filter cleans the air and the the air and the ducting straightens ducting straightens the air flow into the the air flow into the compressor, compressor, eliminating vortexes eliminating vortexes and other and other disturbances.disturbances.

FlowpathFlowpath Inlet air heating coils areInlet air heating coils are

used as anti-icing on used as anti-icing on high humidity, low high humidity, low temperature days. temperature days.

Failure to warm the air Failure to warm the air will result in icing on the will result in icing on the compressor blades.compressor blades.

This reduces GT This reduces GT efficiency, however less efficiency, however less problems than ice flow in problems than ice flow in the compressor.the compressor.

FlowpathFlowpath Inlet plenum has a set Inlet plenum has a set

of IGVs that are of IGVs that are adjusted during startup adjusted during startup and shutdown to and shutdown to protect the compressorprotect the compressor

Protection is from Protection is from surging and stalling of surging and stalling of the airflow.the airflow.

Each stage of Each stage of compression consists compression consists of a rotating stage and of a rotating stage and a stationary stage.a stationary stage.

FlowpathFlowpath Air flows from Air flows from

compressor discharge, compressor discharge, backward along the backward along the combustion can and combustion can and into the combustion into the combustion area.area.

Mixed with fuel gas for Mixed with fuel gas for combustion.combustion.

Some air is used for Some air is used for cooling.cooling.

Combustion is Combustion is sustained.sustained.

FlowpathFlowpath

Dry Low Nox Dry Low Nox combustors create a combustors create a lean air mixture, lean air mixture, causing lower flame causing lower flame temperatures and temperatures and lower NOx Emissions.lower NOx Emissions.

Turbine section Turbine section receives hot gassesreceives hot gasses

Heat energy in the air Heat energy in the air mass works to rotate mass works to rotate the gas turbine shaft.the gas turbine shaft.

FlowpathFlowpath Each stage of the Each stage of the

turbine (3 total) turbine (3 total) consists of a row of consists of a row of nozzles and buckets.nozzles and buckets.

Each nozzle, the Each nozzle, the kinetic energy of the kinetic energy of the flow is increased with flow is increased with an associated an associated pressure drop. This pressure drop. This converts the heat to converts the heat to useful work.useful work.

Force on the blades Force on the blades rotates the shaftrotates the shaft..

FlowpathFlowpath

From the last stage From the last stage blades, the exhaust blades, the exhaust gas is sent through the gas is sent through the HRSG before being HRSG before being sent to the sent to the atmosphere.atmosphere.

Gas Turbine SystemsGas Turbine Systems

The gas turbine has several sub-systems The gas turbine has several sub-systems associated with it.associated with it.• Lube OilLube Oil• CO2 Fire ProtectionCO2 Fire Protection• Water WashWater Wash• Inlet Air FilterInlet Air Filter• Inlet Air HeatingInlet Air Heating• Air ProcessingAir Processing• VentilationVentilation• HydraulicHydraulic• Fuel GasFuel Gas

Gas Turbine ProperGas Turbine Proper

GT consists of:GT consists of:• 18 stage axial flow 18 stage axial flow

compressorcompressor• 14 chamber, can type 14 chamber, can type

combustorcombustor• 3 stage axial flow turbine.3 stage axial flow turbine.

Mounted on vertical Mounted on vertical supports, both forward supports, both forward and aft.and aft.

Aft supports are air Aft supports are air cooled.cooled.

Gas Turbine ProperGas Turbine Proper CompressorCompressor Axial flow refers to the Axial flow refers to the

air flow along the axis.air flow along the axis. Figure to the left Figure to the left

illustrates the illustrates the comparison between an comparison between an axial flow compressor axial flow compressor and a centrifugal and a centrifugal compressor.compressor.

Axial flow is used in this Axial flow is used in this application due to large application due to large volume of air flow.volume of air flow.


Each stage consists of a Each stage consists of a rotating set of blades rotating set of blades and a stationary set of and a stationary set of blades.blades.

Rotor rotates in the Rotor rotates in the compressor casing and compressor casing and holds all rotating blades.holds all rotating blades.

Stator blades are Stator blades are mounted in casing.mounted in casing.

Air flows between them.Air flows between them.


Picture to the left Picture to the left illustrates a typical gas illustrates a typical gas turbine rotor assembly.turbine rotor assembly.

Larger blades are Larger blades are located on the first stage located on the first stage and force it rearward.and force it rearward.

As the air is As the air is compressed, less area compressed, less area is needed to compress is needed to compress the air, so the blade size the air, so the blade size decreases.decreases.

Gas Turbine ProperGas Turbine Proper Process continues Process continues

through each through each successive stagesuccessive stage

Pressures are raised to Pressures are raised to 10-15 times the inlet 10-15 times the inlet pressure.pressure.

Air flow is dependent on Air flow is dependent on the physical size and the physical size and speed of the machine.speed of the machine.

Remember 2/3 of the Remember 2/3 of the power produced by the power produced by the GT is used to drive the GT is used to drive the compressor.compressor.

Gas Turbine ProperGas Turbine Proper Therefore a 1% gain Therefore a 1% gain

in compressor in compressor efficiency produces a efficiency produces a 2% gain in shaft 2% gain in shaft output.output.

Likewise in the Likewise in the reverse direction.reverse direction.

Blades must be kept Blades must be kept clean (water wash) to clean (water wash) to maintain capacity.maintain capacity.

Gas Turbine ProperGas Turbine Proper Most notable Most notable

indication of dirty indication of dirty blades will be blades will be reduced output on reduced output on the Generator.the Generator.

However, pressure However, pressure transducers will allow transducers will allow the operator to the operator to monitor discharge monitor discharge pressure.pressure.

IGV's

1ST STAGE BLADES

2ND STAGE BLADES

COMPRESSOR ROTOR


Gas Turbine ProperGas Turbine Proper Compressor rotor blades are made of Compressor rotor blades are made of

Stainless steel and are individually Stainless steel and are individually attached to the compressor rotor.attached to the compressor rotor.

Air foil shapeAir foil shape Stator vanes are constructed of steel.Stator vanes are constructed of steel. Also air foil shaped to allow smooth airflow.Also air foil shaped to allow smooth airflow.

Gas Turbine ProperGas Turbine Proper Compressor CasingCompressor Casing Constructed of AluminumConstructed of Aluminum Houses the gas turbine compressor and Houses the gas turbine compressor and

provides mounting for stator vanes.provides mounting for stator vanes. Annular passages are constructed in the Annular passages are constructed in the

casing at the outlet side of the 9casing at the outlet side of the 9thth and 13 and 13thth stages.stages.

Air is extracted from 9Air is extracted from 9thth stage during stage during startup, acceleration, and shutdown for startup, acceleration, and shutdown for pulsation protection.pulsation protection.

Gas Turbine ProperGas Turbine Proper Air is extracted from 13Air is extracted from 13thth stage and stage and

compressor discharge for cooling purposes compressor discharge for cooling purposes of the turbine 1of the turbine 1stst and 2 and 2ndnd stages. stages.

Discharge air is also routed to the inlet air Discharge air is also routed to the inlet air heating system for anti-icing (highest heating system for anti-icing (highest temperature air).temperature air).

Approximately 25% of the air from the Approximately 25% of the air from the discharge of the compressor is used for discharge of the compressor is used for combustion.combustion.

Gas Turbine ProperGas Turbine Proper IGVsIGVs Set of vanes used to pivot on axis to Set of vanes used to pivot on axis to

regulate air flow into the compressor regulate air flow into the compressor This provides pulsation (stall) protection This provides pulsation (stall) protection

during startup and shutdown.during startup and shutdown. Hydraulically actuated using a feedback Hydraulically actuated using a feedback

loop of vane angle position.loop of vane angle position. Linkage, mounted on the side of the Linkage, mounted on the side of the

machine actually pivots the IGVs.machine actually pivots the IGVs.

Gas Turbine ProperGas Turbine Proper The hydraulic actuation of the inlet guide vanes is The hydraulic actuation of the inlet guide vanes is

illustrated on G.E. System Drawing No. 0469. The illustrated on G.E. System Drawing No. 0469. The system consists of servo-valve 90TV-1, LVDT position system consists of servo-valve 90TV-1, LVDT position sensors 96TV-1 and 96TV-2, and hydraulic dump valve sensors 96TV-1 and 96TV-2, and hydraulic dump valve VH3-1. The hydraulic oil for the IGV originates from the VH3-1. The hydraulic oil for the IGV originates from the Hydraulic Supply System, GE System Drawing No. 0434. Hydraulic Supply System, GE System Drawing No. 0434. The IGV Trip Oil System as illustrated on G.E. System The IGV Trip Oil System as illustrated on G.E. System Drawing No. 0418. When the IGV trip solenoid valve Drawing No. 0418. When the IGV trip solenoid valve 20TV-1 is energized CLOSED, its drain port is blocked; 20TV-1 is energized CLOSED, its drain port is blocked; thus providing trip oil pressure to the IGV system. As thus providing trip oil pressure to the IGV system. As long as trip oil pressure is available, the dump valve long as trip oil pressure is available, the dump valve (VH3-1) shifts to the 'operating' position. The controlled (VH3-1) shifts to the 'operating' position. The controlled positioning of servo-valve (90TV-1) will then port positioning of servo-valve (90TV-1) will then port hydraulic oil through the dump valve to operate the hydraulic oil through the dump valve to operate the variable inlet guide vane actuator.variable inlet guide vane actuator.

Gas Turbine ProperGas Turbine Proper During startup and During startup and

shutdown, the IGVs shutdown, the IGVs are held in the full are held in the full closed position.closed position.

This reduces the This reduces the amount of torque amount of torque required by the required by the starter and the starter and the amount of air drawn amount of air drawn into the compressor.into the compressor.

Gas Turbine ProperGas Turbine Proper When the When the

Temperature Temperature corrected speed is corrected speed is reached, the inlet reached, the inlet vanes open slightly vanes open slightly to increase airflow to to increase airflow to the compressor.the compressor.

Corrected speed is Corrected speed is a value of rotor a value of rotor speed and inlet air speed and inlet air temp.temp.

Gas Turbine ProperGas Turbine Proper When less than 20% When less than 20%

generator load, the generator load, the IGVs are in the IGVs are in the minimum position. minimum position.

0% open represents 0% open represents 14% open of the 14% open of the vanes. They are vanes. They are never completely never completely shut.shut.

Gas Turbine ProperGas Turbine Proper The IGVs are then The IGVs are then

opened to the opened to the minimum full speed minimum full speed position, around 48°, position, around 48°, until the temperature until the temperature of the exhaust gas of the exhaust gas increases to within increases to within 10°F of base load 10°F of base load temperature.temperature.

Gas Turbine ProperGas Turbine Proper This method This method

produces a higher produces a higher exhaust gas exhaust gas temperature for a temperature for a longer time while longer time while ramping to base ramping to base load.load.

This chokes the This chokes the turbine, cuts down turbine, cuts down on cooling.on cooling.

Gas Turbine ProperGas Turbine Proper The increases the The increases the

exhaust gas exhaust gas temperature, thus temperature, thus increasing and increasing and maintaining steam maintaining steam production and production and superheat at less superheat at less than base load.than base load.

Gas Turbine ProperGas Turbine Proper In simple cycle In simple cycle

mode, not worried mode, not worried about steaming, just about steaming, just about mass flow about mass flow through the through the compressor, so compressor, so ramping open takes ramping open takes place a lot sooner. place a lot sooner.

Full open angle is Full open angle is about 89° - 100%about 89° - 100%

Gas Turbine ProperGas Turbine Proper Speedtronic calls Speedtronic calls

the simple cycle the simple cycle mode - IGV mode - IGV Temperature Temperature Control OffControl Off

Combined Cycle Combined Cycle Mode is IGV Mode is IGV Temperature Temperature Control ONControl ON

Not an option here.Not an option here.

Gas Turbine ProperGas Turbine Proper Surge and StallSurge and Stall When less than When less than

synchronous speed synchronous speed (3600 rpm), the (3600 rpm), the aerodynamics of the aerodynamics of the compressor blades compressor blades do not promote do not promote smooth progression smooth progression of air through the of air through the compressor.compressor.

Gas Turbine ProperGas Turbine Proper Not conducive to Not conducive to

low speed or low low speed or low flow conditions.flow conditions.

Surge results when Surge results when the air flow stalls the air flow stalls across the across the compressor blades. compressor blades.

Can be minor or Can be minor or severe.severe.

Gas Turbine ProperGas Turbine Proper Compressors are Compressors are

protected from protected from surge and stall by surge and stall by • Controlling air flow Controlling air flow

into the compressor into the compressor – IGVs– IGVs

• Bleeding air from the Bleeding air from the compressor in one compressor in one or more stages (9or more stages (9thth / / 1313thth stages). stages).

Gas Turbine ProperGas Turbine Proper Bleed ports are Bleed ports are

equipped with equipped with open/close valves open/close valves (VA-1/2). (VA-1/2).

Open at less than Open at less than 95% speed and 95% speed and close at greater than close at greater than 95% speed.95% speed.

Bleed air is piped to Bleed air is piped to turbine exhaust.turbine exhaust.

Gas Turbine ProperGas Turbine Proper Bearings and SealsBearings and Seals Rotor is supported at the forward end by Rotor is supported at the forward end by

Bearing No. 1Bearing No. 1 Bearing No. 2 supports the Aft End.Bearing No. 2 supports the Aft End. Seals are located on each side of the Seals are located on each side of the

bearing cavity to prevent leakage.bearing cavity to prevent leakage. Seals are under vacuum, keeping oil in. Seals are under vacuum, keeping oil in.

Gas Turbine ProperGas Turbine Proper Combustor Combustor 14 individual reverse flow combustion 14 individual reverse flow combustion

chambers located circumferentially around chambers located circumferentially around the gas turbine.the gas turbine.

Combustion air enters the combustion Combustion air enters the combustion chamber at the center of the unit.chamber at the center of the unit.

Air flows upstream (backwards/reverse) Air flows upstream (backwards/reverse) along outside of the liner cap. along outside of the liner cap.

The combustion liner helps meter the The combustion liner helps meter the amount of air into the combustion area.amount of air into the combustion area.

Gas Turbine ProperGas Turbine Proper Liners Liners Openings along the Openings along the

length provide a film of length provide a film of air for cooling the walls air for cooling the walls of the inner liners and of the inner liners and caps.caps.

14 chambers14 chambers 2 have spark plugs (2/3)2 have spark plugs (2/3) 4 have flame detectors 4 have flame detectors

(11,12,13,14).(11,12,13,14).

Gas Turbine ProperGas Turbine Proper Flame is started with Flame is started with

the retractable spark the retractable spark plug.plug.

Flame is propagated Flame is propagated using crossfire tubes.using crossfire tubes.

Crossfire tubes Crossfire tubes connect all of the connect all of the primary zones of each primary zones of each adjacent combustion adjacent combustion chambers.chambers.

Gas Turbine ProperGas Turbine Proper Nitrogen OxidesNitrogen Oxides Formed in the combustion processFormed in the combustion process

• Thermal NOx – Most PrevalentThermal NOx – Most Prevalent• Fuel NOx – not prevalent when firing natural Fuel NOx – not prevalent when firing natural

gas.gas. Thermal Nox is generated by the high Thermal Nox is generated by the high

temperature reaction between nitrogen in temperature reaction between nitrogen in the atmosphere (78%) and oxygen in the the atmosphere (78%) and oxygen in the air.air.

Highly dependent on temperatureHighly dependent on temperature


N

NN

N

N

Ox

N

N

N

N

N

NOx Ox

OxOx

AMBIENT AIR 79% Nitrogen 21% Oxygen

N

Ox

OxOxN

N N

Ox

N

N

Ox

Ox

N OxN

N

Ox

Ox N

Ox

N

OxN

NITROGEN OXIDES Nitric Oxide Nitrogen Dioxide

OxN

Ox = 1 Oxygen Molecule

= 1 Nitrogen Molecule

OxN

OxN OxN

NOx

= Nitrogen Dioxide

= Nitric Oxide

THERMALDISSOCIATION

Gas Turbine ProperGas Turbine Proper At atmospheric condition, nitrogen (N2) At atmospheric condition, nitrogen (N2)

and Oxygen (O2) are quite stable.and Oxygen (O2) are quite stable. When exposed to heat, the molecules When exposed to heat, the molecules

break apart – thermally dissociatebreak apart – thermally dissociate The unstable atoms combine with each The unstable atoms combine with each

other in forms of NO and NO2.other in forms of NO and NO2. About 95% is NO – colorless and odorlessAbout 95% is NO – colorless and odorless About 5% is NO2 – brownish color and About 5% is NO2 – brownish color and

odorodor

Gas Turbine ProperGas Turbine Proper Reducing NOx EmissionsReducing NOx Emissions Burning of fuel happens in three distinct Burning of fuel happens in three distinct

flames:flames:• Diffusion Flame – Air/Fuel mixed and burned Diffusion Flame – Air/Fuel mixed and burned

simultaneouslysimultaneously• Lean Premix Flame – Air and fuel are Lean Premix Flame – Air and fuel are

premixed before point of combustion.premixed before point of combustion.• Partially Premixed – Combination of diffusion Partially Premixed – Combination of diffusion

and premix flame. Fuel is injected far enough and premix flame. Fuel is injected far enough up stream to mix fuel prior to combustionup stream to mix fuel prior to combustion

Gas Turbine ProperGas Turbine Proper Older turbines used only diffusion flames.Older turbines used only diffusion flames. Requires rich fuel to air ratios Requires rich fuel to air ratios Made for extremely high temperatures.Made for extremely high temperatures. High NOx emissions.High NOx emissions. Need to Lower emissions due to Clean Air Need to Lower emissions due to Clean Air

Act.Act. Injection water and injection steamInjection water and injection steam Dry Low Nox combustors – lower the flame Dry Low Nox combustors – lower the flame

temperatures, without affecting temperatures, without affecting horsepower.horsepower.

Gas Turbine ProperGas Turbine Proper Dry Low Nox combustors are founded on Dry Low Nox combustors are founded on

the principal that the fuel air ratio of any the principal that the fuel air ratio of any combustion process affects (DIRECTLY) combustion process affects (DIRECTLY) the flame temperature.the flame temperature.

Lean fuel air ratios produce lower Lean fuel air ratios produce lower temperature flames than rich air to fuel temperature flames than rich air to fuel ratios.ratios.

Gas Turbine ProperGas Turbine Proper Reducing air fuel Reducing air fuel

ratio too low will ratio too low will result in loss of result in loss of flame.flame.

Lean air fuel ratios Lean air fuel ratios are not permissible are not permissible with diffusion with diffusion burners.burners.

Premix the air and Premix the air and fuel before burning.fuel before burning.

Gas Turbine ProperGas Turbine Proper The fuel is injected The fuel is injected

in multiple ports and in multiple ports and stages inside the stages inside the combustor, well in combustor, well in advance of the advance of the flame zone.flame zone.

Lower flame Lower flame temperatures, result temperatures, result in less thermal in less thermal disassociation, thus disassociation, thus NOx formationNOx formation

Gas Turbine ProperGas Turbine Proper DLN burner has one DLN burner has one

zone of combustion, zone of combustion, however introducing however introducing the fuel in stages the fuel in stages and different and different locations promotes locations promotes premixing of the fuel premixing of the fuel and airand air

Gas Turbine ProperGas Turbine Proper Combustion control Combustion control

by the Speedtronic by the Speedtronic is dependent on the is dependent on the flame detectors, as flame detectors, as well as the turbine well as the turbine firing temperature.firing temperature.

This is used to This is used to sequence the fuel sequence the fuel into the turbine.into the turbine.

Gas Turbine ProperGas Turbine Proper Speedtronic only Speedtronic only

indirectly calculates indirectly calculates turbine firing turbine firing temperature based temperature based on exit temperature on exit temperature (leaving the turbine). (leaving the turbine). This is based on This is based on thermodynamic thermodynamic principles. principles.

DLN uses six DLN uses six nozzles per can.nozzles per can.

Gas Turbine ProperGas Turbine Proper PM1 - centrally PM1 - centrally

located nozzlelocated nozzle PM2 - 2 outer PM2 - 2 outer

nozzles, adjacent to nozzles, adjacent to crossfire tubes.crossfire tubes.

PM3 – 3 outer PM3 – 3 outer nozzles positioned nozzles positioned around the around the remainder of the remainder of the combustor.combustor.

PM3 PM1

Q PM2

Gas Turbine ProperGas Turbine Proper Q – Fuel pegs Q – Fuel pegs

located located circumferentially circumferentially around the around the combustor can, combustor can, upstream of the upstream of the premix nozzles.premix nozzles.

Fully sequence Fully sequence progressing through progressing through 8 stages before 8 stages before reaching full load.reaching full load.

Q PM2

PM3 PM1

Gas Turbine ProperGas Turbine Proper The primary The primary

controlling controlling parameter is the parameter is the turbine firing turbine firing reference reference temperature temperature (TTRF1)(TTRF1)

Refer to pages 16 Refer to pages 16 and 17 for and 17 for explanation of explanation of sequencing.sequencing.

Q PM2

PM3 PM1


Mode Nozzles in Use Description of Operation Start 0 No fuel is admitted. 0 PM1 and PM2 Fuel is admitted to the combustor can for initial

firing and crossfire. PM1 = 30% fuel flow PM2 = 70% fuel flow PM3 = 0% Q=0%

1 PM2 Fuel is admitted from crossfire until approximately 95% speed (3420 rpm). PM1 = 0 % PM2 = 100% PM3 = 0% Q = 0%

2 PM1 Fuel is admitted from 95% speed (3420 rpm) to Full Speed No Load. Exhaust Temp spreads should be below 120°F. PM1 = 100% PM2 = 0% PM3 = 0% Q = 0% Synchronization to the grid is possible.

3 PM1 and PM2 At 1600°F – 2000°F, fuel will be split among PM1 and PM2.

4 PM1 and PM3 At 2000°F, fuel will be split between PM1 and PM3 manifolds.

5 PM2 and PM3 At 2170°F, fuel will transition to PM2 and PM3, before admitting gas to Q. This only occurs briefly.

5Q PM2 and PM3 and Q

At 2170°F, fuel will transition to Q. PM2 and PM3 are already open.

6Q PM1 and PM2 and PM3 and Q

At 2220°F, fuel will flow to all four nozzles.

Gas Turbine ProperGas Turbine Proper Ignition and Flame Ignition and Flame

DistributionDistribution 2 spark igniters or 2 spark igniters or

spark plugs.spark plugs. High voltage spark High voltage spark

when energized when energized which ignites fuel.which ignites fuel.

After the LCI has After the LCI has begun rotation a begun rotation a purge cycle begins.purge cycle begins.

Q PM2

PM3 PM1

Gas Turbine ProperGas Turbine Proper After a few minutes, After a few minutes,

the LCI drops out, the LCI drops out, unit coasts to unit coasts to ignition rpm, about ignition rpm, about 300 rpm then the 300 rpm then the igniters start igniters start sparking.sparking.

Flame is generated Flame is generated and propagated and propagated through the crossfire through the crossfire tubes.tubes.

Q PM2

PM3 PM1

Gas Turbine ProperGas Turbine Proper Since the Brayton Since the Brayton

cycle is continuous cycle is continuous – flame will always – flame will always be present.be present.

Spark Plugs retract.Spark Plugs retract. LCI will continue to LCI will continue to

accelerate turbine accelerate turbine until full speed.until full speed.

LCI drops out at LCI drops out at 95% speed.95% speed.

Q PM2

PM3 PM1

Gas Turbine ProperGas Turbine Proper At higher than 95% At higher than 95%

speed, the turbine speed, the turbine and firing is what and firing is what raises the turbine raises the turbine speed.speed.

Reaches full speed, Reaches full speed, no load condition.no load condition.

Q PM2

PM3 PM1

Gas Turbine ProperGas Turbine Proper Turbine – ExpansionTurbine – Expansion As gas expands, As gas expands,

both thermal and both thermal and kinetic energy of kinetic energy of combustion gasses combustion gasses is converted to is converted to mechanical energy.mechanical energy.

Use impulse and Use impulse and reaction principles, reaction principles, illustrated on the illustrated on the left.left.

Gas Turbine ProperGas Turbine Proper Turbine consists of Turbine consists of

• Turbine RotorTurbine Rotor• Turbine StatorTurbine Stator• Exhaust FrameExhaust Frame• Exhaust DiffuserExhaust Diffuser

Turbine consists of Turbine consists of forward and aft wheels.forward and aft wheels.

Spacers between Spacers between wheelswheels

All are mated with a tie-All are mated with a tie-bolt construction.bolt construction.

Gas Turbine ProperGas Turbine Proper Due to pressure Due to pressure

reduction resulting in reduction resulting in energy conversion, energy conversion, the size of buckets the size of buckets are increased through are increased through the successive the successive stages to stages to accommodate the accommodate the gas flow. Less gas flow. Less pressure, more pressure, more volume.volume.

Gas Turbine ProperGas Turbine Proper Fir tree-shaped Fir tree-shaped

dovetails that fit into dovetails that fit into the cutouts in the the cutouts in the turbine wheels.turbine wheels.

22ndnd and 3 and 3rdrd stage stage buckets are shrouded buckets are shrouded at blade tips to at blade tips to increase turbine increase turbine efficiency – efficiency – minimizing tip minimizing tip leakage.leakage.

Gas Turbine ProperGas Turbine Proper Turbine Stator – Turbine Stator –

NozzlesNozzles Similar to the rotor Similar to the rotor

stages, these also stages, these also increase in sizeincrease in size

Labyrinth seals Labyrinth seals prevent leakage prevent leakage along the shaft.along the shaft.

Horizontally split Horizontally split along casing line.along casing line.

Gas Turbine ProperGas Turbine Proper Turbine Shell and Turbine Shell and

Exhaust FrameExhaust Frame Hold the stator Hold the stator

nozzles in place and nozzles in place and control turbine control turbine clearances.clearances.

Cooling is provided to Cooling is provided to control size of GT control size of GT shell and thus shell and thus leakage past the leakage past the blades.blades.

Gas Turbine ProperGas Turbine Proper Cooling provided by two exhaust frame Cooling provided by two exhaust frame

blowers.blowers. 75 hp motors 75 hp motors This prevents thermal growth of turbine, This prevents thermal growth of turbine,

maintaining alignment.maintaining alignment. #2 bearing cooling provided by two 7.5 hp #2 bearing cooling provided by two 7.5 hp

blowers.blowers.

Gas Turbine ProperGas Turbine Proper Turbine CoolingTurbine Cooling Increased firing temperatures and mass Increased firing temperatures and mass

flows have increased turbine output.flows have increased turbine output. These are possible by betterThese are possible by better

• Blade and nozzle designsBlade and nozzle designs• MaterialsMaterials• Improved CoolingImproved Cooling

Gas Turbine ProperGas Turbine Proper Cooling air supplied by Cooling air supplied by

compressor discharge.compressor discharge. Flows out of blades Flows out of blades

and into the exhaust and into the exhaust duct.duct.

11stst and 2 and 2ndnd stage stage cooling is samecooling is same

33rdrd stage is not cooled stage is not cooled because temp is because temp is already low.already low.

Gas Turbine ProperGas Turbine Proper Turbine nozzles are Turbine nozzles are

cooled with cooled with compressor discharge compressor discharge air. air.

First and second stage First and second stage nozzles are cooled by nozzles are cooled by internal impingement internal impingement and external film and external film cooling.cooling.

See leading and See leading and trailing edge holes.trailing edge holes.

Gas Turbine ProperGas Turbine Proper Turbine rotor cooling is to promote Turbine rotor cooling is to promote

reasonable temperatures and longer reasonable temperatures and longer service life.service life.

Turbine cooling is monitored using the Turbine cooling is monitored using the wheelspace temperatures.wheelspace temperatures.

Detectors are located in each wheelspace Detectors are located in each wheelspace for remote indication.for remote indication.


THERMOCOUPLE WHEELSPACE TEMPERATURE

TT-WS1AO-1 1st Stage Aft Outer 950°F

TT-WS1AO-2 1st Stage Aft Outer 950°F TT-WS1FI-1 1st Stage Forward Inner 800°F TT-WS1FI-2 1st Stage Forward Inner 800°F

TT-WS2AO-1 2nd Stage Aft Outer 950°F

TT-WS2AO-2 2nd Stage Aft Outer 950°F

TT-WS2FO-1 2nd Stage Forward Outer 950°F

TT-WS2FO-2 2nd Stage Forward Outer 950°F

TT-WS3AO-1 3rd Stage Aft Outer 800°F

TT-WS3AO-2 3rd Stage Aft Outer 800°F

TT-WS3FO-1 3rd Stage Forward Outer 850°F

TT-WS3FO-2 3rd Stage Forward Outer 850°F

gas turbine - part 1

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