gas turbine: basics

Gas Turbine: Basics

Reviewed by

Muhammad Salman BilalBSEE,MSEE,MSEM

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Introduction Purpose of the plant

Main components, system configuration

Gas turbine technology History, energetic considerations, description

Turbogenerator Technical description, mechanical and electrical systems

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Turbogenerator (Solar Titan) Technical description, mechanical and electrical

systems

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Main points

Basically we apply the co-generation concept in order to produce heat energy (steam) from one side and electrical energy from the other.

The electrical energy is also such an important argument where a reliable network is necessary (chemical, textile, 3rd world,…)

Network voltage failure

Other particular situations

Advantages

Better efficiency in the energy production.

Better quality of the energy (self made = more reliability, flexibility…)

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Main components

The system is basically composed of :

Turbo generator

Produce electric energy and (or) thermal energy Medium voltage (MV) station (accessory)

Ensures the electrical power connection between the turbo generator, the plant and the network

Boiler (accessory)

Convert the thermal energy in steam

Diesel engine generator (accessory)

Produce electric energy

Gas Compressor (accessory Ener project)

Increase and stabilize the gas pressure when it drops

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ElectricGenerator

Turbogeneratorauxiliary

System (LV)

Air compressor

………

Main packagesupply

Diesel engine Gas turbine

ElectricGenerator

(11000 Vac)

MV station

MV plant

Main plant

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Gas turbine technology Energetic considerations, description

Turbogenerator (Solar Titan) Technical description, mechanical and electrical

systems

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The gas turbine is composed of 3 main parts :

The compressor

Increases the pressure of incoming comburant air.

The combustion chamber

The mixture fuel /air is burned and gas temperature increased.

The power turbine

Which converts the thermal and kinetic energy of the burned gases to mechanical energy, avalaible on the gas turbine rotor shaft.

Main components

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The gas turbine can be compared (continous cycle) with a four stroke engine (alternating cycle):

exhaustexhaust

combustioncombustion

Air inletAir inlet

compressioncompression

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Electricalpower

Mechanicalpower

Thermal power

Chemicalpower

Fuel

Combustionchamber Compressor

Power turbine Generator

airGearboxExhaust gas

Global efficiency

Gas turbine power flow

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Stage = stator + rotor

Through the stages of the compressor the gas decelerates and the pressure increases.In the compressor, the mechanical energy is converted in potential energy, increasing the gas pressure.

stator rotor

1 2 3

u

PPressureevolution

The compressor

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The combustion chamber shape is annular.

There the mixture fuel/air is burned at constant pressure.

Because of the high combustion temperature (~2000 °C), the gas temperature is reduced with air coming from the compressor (dilution air) to obtain an admissible temperature of the metallic parts (turbine blades and combustion chamber) 800-1200 °C

Combustion chamber

Fuel inlet Dilution air holes


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combustion chamber section

Ignition torch

Air from compressor

Primary air

Injector Secondary air

Tertiary air

Injector nose


14

stator rotor

1 2 3

u

P

Stage = rotor + stator

Through the stages of the power turbine the gas accelerates and the pressure decreases.

In the turbine, the potential energy of the gas is transformed to mechanical energy.

The total aerodynamic force acting on the rotor blades is transferred to the rotor shaft, which rotates at the speed .

Pressureevolution

Power turbine

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Turbine blades

Combustion chamber

Through the stages of the power turbine the gas is accelerated and energy trasferred to the rotor blades, which rotate the shaft. The power is finally trasferred to the compressor and the electrical generator.

Cooling air

Power turbine blades (T130)

Power turbine

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Turbogenerator Technical description, mechanical and electrical systems

Diesel generators (800 kVA, 1400 kVA)

Air compressor

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Package design Main components : Gas turbine

Gear boxGenerator

Main circuits : Electric start systemLube oil systemGas fuel systemLiquid fuel systemAir system

The electric system : Control room panels Field bus modules

Turbogenerator group

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Front view (Titan)

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Top view (Titan)

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Rear view (Titan)

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General view (example)

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2

4

5

6

1

7

Turbine type :- single shaft- axial flow design

1) Gearbox assembly2) Air inlet assembly3) Axial flow compressor4) Combustor assembly5) Turbine assembly6) Exhaust diffuser and bellows7) Supporting frame

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Titan 130 –20501 gas turbine engine specifications

Description DataCOMPRESSOR

Type AxialNumber of stages 14Compression ratio 17 : 1

Speed 11197 rpmCOMBUSTION CHAMBER

Type AnnularIgnition Torch

Number of fuel injectors 14

TURBINE

Type AxialNumber of stages 3

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Titan 130 The compressor

Air inlet duct

Through the air inlet duct, pre-filtered ambient air is drawn into the axial compressor and then used for combustion process.

Back view (from gearbox) Lateral view

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1

3

4

2

1) Compressor air inlet flange2) Forward compressor case3) Aft compressor case4) Variable guide vanes

Compressor case assembly

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3

1

1) Variable guide vane (stator)2) Rotor blades3) Forward compressor case

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The variable - position guide vane system (IGV) avoids compressor surge during starting and transient operation.

The angular position of the inlet guide vanesAnd stator vanes of the first six compressor stages are in function of gas turbine speed for start-up and acceleration. Increasing speed will cause the guidevanes to move from close position (- 45 °) to full open position (5°).The guide vane system uses an electric motor-driven roller screw actuator with position feedback.

The variable guide vane system is controlled by:- Guide vane actuator motor (command : 4-20 mA)- Guide vane actuator resolver (feedback : 4-20 mA)- Guide vane actuator controller

Variable guide vane system

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The combustor assembly is boltedto the aft end of the compressordiffuser assembly.

The main components are:

1) Fuel and air manifolds2) Fuel injectors3) Combustor liner assembly4) Torch igniter assembly5) Bleed air valve assembly

1

2

3

Titan 130 Combustor assembly

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The compressor bleed air system prevents compressor surge, reducing back pressure during start sequence and transient operations.The compressor air is bled from the combustor housing directly to the exhaust diffuser.

The system is composed of :

1) Bleed air pipe2) Butterfly valve3) Electrical actuator4) Clamp 1

2

3

4

Titan 130 Combustor assembly Bleed air

system

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Bleed air pipe

Electrical actuator

Titan 130 Combustor assembly Bleed air

system

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Titan 130 Combustor assembly Fuel supply

systemThe turbine fuel supply system is composed of : Three tubular manifolds, which encircle the combustor housing. (1)-Main gas supply (larger in diameter), (2)-Pilot gas supply, (3)-Atomization air (4)-14 liquid fuel injectors, which receive air and fuel from the manifolds.

3

2

1

4

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Titan 130 Combustor assembly Torch igniter assembly

The torch igniter assembly is installed on the bottom of the combustor assembly(7 o’clock position). During start cycle, a separate fuel line supplies liquid fuel to the torch which is lit by an igniter spark. The torch ignites the fuel / air mixture entering the combustor chamber through the injectors. When continous burning is recognized from the control system, the torch is extinguished.

Fuel supply inlet

Liquid drain outlet

Spark

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Titan 130 Power turbine & exhaust diffuser

The power turbine is located aft of the combustor assembly. The power turbine assembly includes first, second and third stage turbine rotor’s disc and turbine nozzles.First and second stages of blades are cooled with bleed air.Around the third stage turbine nozzles 12 thermocouples that measure the T5 temperature are mounted.

1) Power turbine assembly2) T5 thermocouples3) PCD air for cooling T5

ring4) Exhaust diffuser

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2

1

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The main function of the gearbox is to reduce the drive speed from the turbine to the generator.The generator speed is 1500 rpm for 50 HZ service.The gearbox is therefore located between the turbine and the generator.It has an epicyclic star-gear design.

The gearbox is also equipped with two starter motors (used for turbine start) and is used to drive the mechanic oil pump (for the main oil circuit).These are the auxiliary functions of the gearbox.Two speed pick-ups (1) (for speed control and protection use) are also mounted on the gearbox.

General description

1

Titan 130 Gearbox

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Description DataTYPE epicyclical

MANUFACTURER ALLEN GEARS

RATING

Transmitted Power 22200 HP (16561 Kw)

Input Speed 11197 rpm

Output Speed 1500 rpm

Gear Ratio 7,465

LUBRICATION (nom.val)

Pressure 1.7 – 3 barg

Temperature 43 – 74 °C

GEARBOX WEIGHT

Total weight 6042 Kg

Titan 130 Gearbox

Technical data

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HIGH SPEED(input)

LOW SPEED(output)

Primary stage1) Central sun wheel2) Star wheels (3)

Secondary stage3) Star wheel shaft4) Internal gear ring5) Star carrier6) Low shaft speed

Power flow

Titan 130 Gearbox

Main reduction drive

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1) Starter motor drives2) Oil pump drive3) Gearbox output shaft4) Speed pick-up

1

2

14 3

4

Titan 130 Gearbox

Auxiliary drives

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Titan 130 Generator

General description

•The generator converts mechanical power of gas turbine to electrical power.•The shaft of the generator is coupled to the slow speed shaft of the gearbox (1500 rpm).•The machine consists of a main generator, stator and rotor (internal-pole machine) and an exciter (external-pole machine).•The generator is air cooled, with two fans mounted on to the rotor shaft.•The main terminal box is mounted on the top of the generator. It contains the winding ends, the voltage and current trasformers for control, measurement and protection use.•An auxiliary box, also on the top of the generator,•contains low voltage terminals.

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1) Stator2) Magnet wheel (rotor)3) Rectifier bridge

4) Exciter armature5) Exciter coil6) Automatic voltage regulator(AVR)

Titan 130 Generator

Electric schematic

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Titan 130 Generator

Generator data

Manufacturer : Alstom( Leroy Somer)Type : synchronous, 4 polesNominal power : 17000 kVAFrequency : 50 HzVoltage : 11000 VPower factor : 0.8Speed : 1500 rpm

gas turbine: basics

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