Gas Turbine

Operation and Maintenance

OPERATION, PERFORMANCE AND MAINTENANCE

Gas Turbine

CHAPTER 1

Introduction to the gas turbine engine

Gas Turbine Engine Classification I- Industrial Gas Turbine II- Air craft Gas Turbine

• Aircraft propulsion,• Oil and gas pipeline pumping• Offshore platforms• Utility power generation• Ship propulsion • Equipment Prime mover

Major gas turbine implementation

CHAPTER 2

Energy transmission in gas turbine engines

CHAPTER 3

Fluid flow in gas turbines

Air in the compressor stages. How pressure builds up through the compressor stages. Flue gas in the turbine stages. Air in the combustion chamber

CHAPTER 4 Gas turbine engine performance and specifications

1- Code and Standards2- performance and specifications

CHAPTER 5

CHAPTER 6

Selected topics on gas turbine component design

Maintenance of gas turbines

CHAPTER 7

Miscellaneous

• Gas Turbine Thrust balance• Dry gas seal system• Gas Turbine Thrust balance• Dry gas seal system• Bearings

Introduction to the gas turbine engine

CHAPTER 1

As a result, the specific fuel consumption of the turbo-machine has been reduced and thrust to weight ratios have increased.

Preface

The aircraft gas turbine engines test ran and produced thrust for the first time in 1937.

After 1945, aircraft gas turbine development efforts have been directed towards increasing pressure ratios, turbine inlet temperatures, component efficiencies, bypass ratios, reliability and durability.

The turbo-machine is now one of the worlds most important prime movers.

The first jet engine developed only a few hundred pounds of thrust, while the latest generation of engines exceed 100,000 pounds thrust.

The engines for the land-based power plants exceed 250MW in power output.

* Major gas turbine implementation

• Aircraft propulsion,• Oil and gas pipeline pumping• Offshore platforms• Utility power generation• Ship propulsion • Equipment Prime mover

* Gas Turbine Engine Classification

I- Industrial Gas Turbine

II- Air craft Gas Turbine The output can range from 100% thrust or essentially all shaft power

The output is the all shaft power

A- Turbo propeller All of the power output is used to turn the propeller shaft. a gear box is used between the engine and propeller

B- Turbofan The power output is split between thrust and power to turn the fan which comes after the compressor.

C- Turbo Jet All of the power output is used in a form of thrust

I- Industrial Gas Turbine

DIFFUSER

AIR COMPRESSOR

AIR INLET

COMBUSTOR

GAS GENERATOR TURBINES

EXHAUST

AIR

AIR

FUEL

FUEL

EXHAUST

EXHAUST

A- Turbo propeller

Turbine

Combustion chamber

CompressorPropeller

II- Air craft Gas Turbine

All of the power output is used to turn the propeller shaft.

B- Turbofan

TurbineCompressorFan Exhaust

1- power to turn the fan

The power output is split between

2- Jet thrust

C- Turbo Jet

TurbineCompressor Exhaust

All of the power output is used in a form of Jet thrust

Turbine Wheel

Compressor Wheel

Compact type GT.

AIR OUT

Combustion Chamber

FLUE GASES

EXHAUST

AIR IN

Compact type GT.Compressor and Turbine Wheels

Shaft Attachment

Energy transmissionin gas turbine engines

CHAPTER 2

COMPRESSOR TURBINE

Atmospheric Air

PCD = 8 to 12 bar Pressure is constant

Fuel

Power distributionPower distribution

COMBUSTION CHAMBER

COMPRESSOR

20 MW

FUEL

35 MW

20 MW HOT AIRCOLD AIR

35 MW

EXHAUST

25 MW

TURBINE

LOAD

10 MW

55 MW

Assuming 100% Efficiency

Exhaust70%

Mechanical power28%

Sankey diagram

Fuel Input100%

Radiation& Mechanical losses2%

Turbine Power

Compressor Power

Gas Turbine Combined Cycle

Generator

COMPRESSOR TURBINE

Hot Gas

BOILER

STEAM

STEAM TURBINE

GeneratorGenerator

Fluid flow in gas turbines

CHAPTER 3

* Gas Turbine performanceT

EM

RE

RA

TU

RE

PR

ES

SU

RE

Compressor Combustor

Turbine

Exhaust

FLUIDS FLOW KINAMATIC ENERGY

v2 < v1 P2 > P1

P1

P2

+2 g

V22 P2

+2 g

V12 P1 CONSTANT

Thermal energy Plus

TOTAL ENERGY DIMENTIONS

2V2g

ft2

sec 2

ft2sec

= ( ft )=ft

2

sec

ft2sec

=

P

density

ft 3

2ft= ( ft )=

Lb

Lb

2

ft 3

ft=

AIR IN COMPRESSOR STAGES

AIR IN COMPRESSOR STAGES

FIXED

STATOR BLADES

FIXED

STATOR BLADES

COMP.BLADES

MOVING

AIR IN COMPRESSOR STAGESAIR IN COMPRESSOR STAGES

FIXED

STATOR BLADES

COMP.BLADES

MOVING FIXED

STATOR BLADES

X

XY1

Y2

STATOR BLADES ACT AS DIFFUSER

AS Y2 > Y1

AIR PRESSURE THROUGHCOMPRESSOR BLADES

HAS NO CHANGE

AS X = X

STATOR BLADES ACT AS DIFFUSER

FIXED

STATOR BLADES

FIXED

STATOR BLADES

VOLUME INCREASED

HOW PRESSURE BUILDS UP IN COMPRESSOR STAGES

HOW PRESSURE BUILDS UP IN COMPRESSOR STAGES

PRESSURE INCREASED

VELOCITY (IN STATOR ) DECREASED

VELOCITY (IN MOVING ) INCREASED

VELOCITY IS CONSTANT ALONG THE COMPRESSOR

V inlet = V outlet

VELOCITY IS CONSTANT ALONG THE COMPRESSOR

V inlet = V outlet

COMP.BLADESMOVING

Velocity

Pressure

Rotor Stator StatorRotor

Axial Flow Compressor Pressure

Stator

Constant Velocity

Pressure increased

TURBINEBLADES

MOVINGFIXED

STATOR BLADES

FIXED

STATOR BLADES

FLUE GASES IN GAS

TURBINE.

FLUE GASES IN GAS

TURBINE.

TURBINEBLADES

MOVINGFIXED

STATOR BLADES

FIXED

STATOR BLADES

FLUE GASES IN GAS

TURBINE.

FLUE GASES IN GAS

TURBINE.

STATOR BLADES ACT AS NOZZELS

VOLUME INCREASED

HOW POWER GENERATES IN GT. STAGES HOW POWER GENERATES IN GT. STAGES

PRESSURE DECREASED

VELOCITY DECREASED

TEMPERATURE DECREASED

STATOR BLADES ACT AS NOZZELSTHE FLUE GASES VELOCITY ENERGY WILL BE TRANSFERED TO TURBINE BLADES

ENERGY PARAMETERS THROUGH THE TURBINE INLET AND OUTLET WILL BE :

AIR THROUGH COMPRESSOR STAGESAIR THROUGH COMPRESSOR STAGES

3- TEMPERATURE INCREASED

1- PRESSURE INCREASED

2- VELOCITY CONSTANT

4- VOLUME DECREASED

A

AIR THROUGH COMBUSTION CHAMBERSAIR THROUGH COMBUSTION CHAMBERS

1- PRESSURE CONSTANT

2- TEMPERATURE INCREASED

3- VOLUME INCREASED

B

FLUE GASES THROUGH TURBINE STAGESFLUE GASES THROUGH TURBINE STAGES

1- PRESSURE DECREASED

3- TEMPERATURE DECREASED

4- VOLUME INCREASED

2- VELOCITY DECREASED

C

Gas turbine engine performance and specifications

CHAPTER 4

* Code and Standards

API RP 11PGT Recommended Practice for Packaged Combustion Gas Turbines

API STD 616 Gas Turbines for Petroleum, Chemical, and Gas Industry Services

Back-up Lube Oil Pump started

START COMMAND

Supply Lube Oil to :• Turbine• Gear box• Generator bearings• Accessory driver

Turbine driven L/O Pump starts as Engine rotates

15% to 20% Ngp

Purge

Ignition CommandFuel valve opened

Commence Rotation

65% Ngp• Starter Drop out• Main L/O Pump supply all pressure• Back-up Lube Oil Pump stopped

83 % NgpBleed ValveFully closed

Ngp

Per

cen

t

Elapsed time

100% Ngp 75% Ngp• Variable Guide vanes start to open• Bleed Valve start to close

General System Operational

SequenceSingle shaft

Generator Set

General System Operational

SequenceSingle shaft

Generator Set

43

IN CASE OF GAS TURBINEAIR COMPRESSOR SURGE BLEED VALVE WILL OPEN

IN CASE OF GAS TURBINEAIR COMPRESSOR SURGE BLEED VALVE WILL OPEN

COMPRESSOR TURBINE

BLEED VALVE

SIMPLE CYCLE P-V DIAGRAM OF G.T.SIMPLE CYCLE P-V DIAGRAM OF G.T.

P

ATMS

V1

CO

MP

RE

SSION

4

TU

RB

INE

(EX

PAN

SION

)

32COMBUSTION

WHY GAS TURBINE CONSIDERED AS

A THERMAL POWER ENERGY MACHINE

WHY GAS TURBINE CONSIDERED AS

A THERMAL POWER ENERGY MACHINE

1- COMPRESSION STAGE

Wc = m * Cp ( T2 – T1 ) KW

2- COMBUSTION STAGE

Q f = m * Cp ( T3 – T2 ) KW

3- TURBINE POWER STAGE

Wt = m * Cp ( T3 – T4 ) KW

W c = Compressor power kw

W t = Turbine power kw

Q f = Fuel produced power kw

m = Air mass flow kg/sec.

Cp = Specific heat kj/kg.

T = Absolute Temperature

0k0k

GAS TURBINE POWERGAS TURBINE POWER P

ATMS

V

1C

OM

PR

ESSIO

N

4

TU

RB

INE

(EX

PAN

SION

)32

COMBUSTION

=Wt - Wc

Q fξ

0

OUTPUT

INPUT* 100= * 100

( T3 – T4 ) – ( T2 – T1 )

T3 – T2= * 100

OVERALL EFFICIENCY ξT

( T3 –T2) – (T4 – T1 )

T3 – T2= * 100

1 – ( T4 – T1 )

( T3 – T2 )= * 100

OVERALL EFFICIENCY ξT

ξT

= 1 – ( T4 – T1 )

( T3 – T2 )ξ0

To improve

* EXHAUST TEMP. T4 TO BE AS LOW AS POSSIBLE

* FIRING TEMP T3 TO BE AS HIGH AS POSSIBLE

* COMP.OUT.TEMP.T2 TO BE AS LOW AS POSSIBLE

* T2 - T1 to be considered

EXAMPLEFIND THE Turbine EFFICIENCY OF G.T HAS THE FOLLOWING DATA: -

1 – AMBIENT TEMPERATURE = 20 C

2 – FIRING TEMPERATURE = 950 C

3 – EXHAUST TEMPERATURE = 490 C

4 – COMP. OUT TEMPERATURE = 300 C

O

O

O

O

T1 = 20 + 273 = 293 K

T3 = 950 + 273 = 1223 K

T4 = 490 + 273 = 763 K

T2 = 300 + 273 = 573 K

O

O

O

O

ξ0

= 1 – ( T4 – T1 )

( T3 – T2 ) ξ0

= 1 – ( 763 – 293 )

( 1223 – 573 )

ξ0

= 1 – ( 470 )

( 650 ) ξ0

= 1 – ( 0.72 )

ξ0

= 0. 28 = 28%

ENTHALPY AND KINETIC ENERGY

h = Cp T

Cp = 0.24 Btu / Ib F

Cp = 1.01 KJ / kg C

EXAMPLE

FIND THE OVERALL EFFICIENCY OF G.TURBINE HAS THE FOLLOWING DATA: -

1 – AMBIENT TEMPERATURE T1 = 12

2– COMP. OUT TEMPERATURE T2 = 200

3 – EXHAUST TEMPERATURE T3 = 950

4– FIRING TEMPERATURE T4 = 340

1- T1 = 20 + 273 = 293 K2- T2 = 300 + 273 = 573 K3- T3 = 950 + 273 = 1223 K4- T4 = 490 + 273 = 763 K

( T4 – T1 )( T3 – T2 )

( 763 – 293 ) ( 1223 – 573 )

ξ = 0.56

1 – =ξ

1 – =ξ

AIR

COMPHIGHPRESS

9000 RPM

TURBINEHIGHPRESS9000 RPM

POWERTURBINE5000 RPM

COMPRESSORLOW PRESSURE6000 RPM

TURBINELOW PRESSURE6000 RPM

Combustion Chamber

Gas Compressor

Two shaft Gas Turbine