Operation and Maintenance Gas Turbine Operation and Maintenance

OPERATION, PERFORMANCE AND MAINTENANCE Gas Turbine OPERATION, PERFORMANCE AND MAINTENANCE CHAPTER 1 Introduction to the gas turbine engine Gas Turbine Engine Classification I- Industrial Gas Turbine II- Air craft Gas Turbine Major gas turbine implementation Aircraft propulsion, Oil and gas pipeline pumping Offshore platforms Utility power generation Ship propulsion Equipment Prime mover

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 Standards 2- performance and specifications

CHAPTER 5 Selected topics on gas turbine component design CHAPTER 6 Maintenance of gas turbines CHAPTER 7 Miscellaneous Gas Turbine Thrust balance Dry gas seal system Bearings

CHAPTER 1 Introduction to the gas turbine engine

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

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.

Oil and gas pipeline pumping Offshore platforms * 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 The output is the all shaft power The output can range from 100% thrust or essentially all shaft power II- Air craft Gas Turbine 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 GAS GENERATOR TURBINES COMBUSTOR AIR COMPRESSOR EXHAUST DIFFUSER AIR INLET

AIR FUEL EXHAUST

II- Air craft Gas Turbine A- Turbo propeller All of the power output is used to turn the propeller shaft. Combustion chamber Propeller Compressor Turbine

The power output is split between B- Turbofan The power output is split between 1- power to turn the fan 2- Jet thrust Exhaust Fan Compressor Turbine

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

Compact type GT. Combustion Chamber AIR IN EXHAUST AIR OUT FLUE GASES Compressor Wheel Turbine Wheel AIR IN EXHAUST Rotating assembly cut-away Note shaft laminations Integral expander housing cover Bearing housing made of stainless steel (non magnetic material is a must to avoid effects of the housing on the rotor). AIR OUT FLUE GASES Combustion Chamber

Compact type GT. Compressor and Turbine Wheels A range of expander wheels 3” (75mm) to 18” (450mm). Note splitter vanes on larger wheel, these are used to optimize the gas flow through the wheel while balancing the increased frictional losses of more blades. Compare performance of wheel with 2 blades and infinite blades. A 2 blade design provides minimal frictional losses but does not efficiently channel flow through the wheel. An infinite bladed wheel achieves optimum flow but frictional losses are too great. MTC designs only 100% open wheels, NO brazing, welding, etc… 100% solid construction permits higher wheel stresses and faster tip speeds.

Shaft Attachment Tapered attachment means wheels are removed easily, no scoring due to interference fit. Note holes in expander wheel are pressure balance holes, to be addressed during ATE discussion.

CHAPTER 2 Energy transmission in gas turbine engines

PCD = 8 to 12 bar Fuel Pressure is constant Atmospheric Air COMPRESSOR TURBINE Atmospheric Air COMPRESSOR PCD = 8 to 12 bar Pressure is constant

Power distribution Assuming 100% Efficiency LOAD 35 MW 55 MW COMBUSTION CHAMBER EXHAUST 25 MW FUEL 35 MW 55 MW 20 MW HOT AIR COLD AIR 20 MW 35 MW LOAD 10 MW COMPRESSOR TURBINE

Radiation& Mechanical losses Sankey diagram Exhaust 70% Radiation& Mechanical losses 2% Mechanical power 28% Compressor Power Fuel Input 100% Turbine Power

Gas Turbine Combined Cycle BOILER COMPRESSOR TURBINE STEAM Hot Gas Generator STEAM TURBINE Generator Generator

CHAPTER 3 Fluid flow in gas turbines

* Gas Turbine performance Combustor Turbine Compressor Exhaust TEMRERATURE PRESSURE

Thermal energy v2 < v1 P2 > P1 CONSTANT Plus FLUIDS FLOW KINAMATIC ENERGY P2 P1 Thermal energy Plus + 2 g V2 2 P2 + 2 g V1 2 P1 CONSTANT v2 < v1 P2 > P1

= = = = V 2g P TOTAL ENERGY DIMENTIONS ( ft ) ( ft ) density 2 ft ft sec = ft 2 sec = ( ft ) Lb 2 ft 3 = P ft 3 2 = ( ft ) density

FIXED FIXED AIR IN COMPRESSOR STAGES STATOR BLADES STATOR BLADES MOVING FIXED

Y2 Y1 STATOR BLADES COMP. BLADES STATOR BLADES FIXED FIXED MOVING AIR IN COMPRESSOR STAGES AIR PRESSURE THROUGH COMPRESSOR BLADES HAS NO CHANGE AS X = X STATOR BLADES ACT AS DIFFUSER AS Y2 > Y1 Y2 X X Y1 STATOR BLADES COMP. BLADES STATOR BLADES FIXED FIXED MOVING

V inlet = V outlet STATOR BLADES ACT AS DIFFUSER VOLUME INCREASED HOW PRESSURE BUILDS UP IN COMPRESSOR STAGES STATOR BLADES ACT AS DIFFUSER VOLUME INCREASED PRESSURE INCREASED VELOCITY (IN STATOR ) DECREASED VELOCITY (IN MOVING ) INCREASED VELOCITY IS CONSTANT ALONG THE COMPRESSOR V inlet = V outlet STATOR BLADES COMP. BLADES STATOR BLADES MOVING FIXED FIXED

Axial Flow Compressor Pressure Constant Velocity Velocity Pressure increased Pressure Stator Rotor Stator Rotor Stator

FIXED FIXED FLUE GASES IN GAS TURBINE. STATOR STATOR BLADES BLADES MOVING

FIXED FIXED FLUE GASES IN GAS TURBINE. STATOR STATOR STATOR BLADES ACT AS NOZZELS STATOR BLADES STATOR BLADES TURBINE BLADES FIXED MOVING FIXED

TEMPERATURE DECREASED HOW POWER GENERATES IN GT. STAGES STATOR BLADES ACT AS NOZZELS THE FLUE GASES VELOCITY ENERGY WILL BE TRANSFERED TO TURBINE BLADES ENERGY PARAMETERS THROUGH THE TURBINE INLET AND OUTLET WILL BE : PRESSURE DECREASED VELOCITY DECREASED TEMPERATURE DECREASED VOLUME INCREASED

A AIR THROUGH COMPRESSOR STAGES 1- PRESSURE INCREASED 2- VELOCITY CONSTANT 3- TEMPERATURE INCREASED 4- VOLUME DECREASED

B AIR THROUGH COMBUSTION CHAMBERS 1- PRESSURE CONSTANT 2- TEMPERATURE INCREASED 3- VOLUME INCREASED

C FLUE GASES THROUGH TURBINE STAGES 1- PRESSURE DECREASED 2- VELOCITY DECREASED 3- TEMPERATURE DECREASED 4- VOLUME INCREASED

performance and specifications CHAPTER 4 Gas turbine engine performance and specifications

* Code and Standards API STD 616 Gas Turbines for Petroleum, Chemical, and Gas Industry Services API RP 11PGT Recommended Practice for Packaged Combustion Gas Turbines

General System Operational Sequence Single shaft Generator Set 100% Ngp Supply Lube Oil to : Turbine Gear box Generator bearings Accessory driver 75% Ngp Variable Guide vanes start to open Bleed Valve start to close 65% Ngp Starter Drop out Main L/O Pump supply all pressure Back-up Lube Oil Pump stopped 83 % Ngp Bleed Valve Fully closed Turbine driven L/O Pump starts as Engine rotates Ngp Percent 15% to 20% Ngp Purge Ignition Command Fuel valve opened General System Operational Sequence Single shaft Generator Set START COMMAND Back-up Lube Oil Pump started Commence Rotation Elapsed time

IN CASE OF GAS TURBINE AIR COMPRESSOR SURGE BLEED VALVE WILL OPEN 43 43

P V SIMPLE CYCLE P-V DIAGRAM OF G.T. ATMS 3 2 4 1 COMBUSTION COMPRESSION 4 TURBINE (EXPANSION) ATMS V

A THERMAL POWER ENERGY MACHINE WHY GAS TURBINE CONSIDERED AS A THERMAL POWER ENERGY MACHINE

P Wc = m * Cp ( T2 – T1 ) KW V Q f = m * Cp ( T3 – T2 ) KW GAS TURBINE POWER COMBUSTION 2 3 P TURBINE (EXPANSION) 1- COMPRESSION STAGE Wc = m * Cp ( T2 – T1 ) KW COMPRESSION ATMS 4 1 V 2- COMBUSTION STAGE Q f = m * Cp ( T3 – T2 ) 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 k 3- TURBINE POWER STAGE Wt = m * Cp ( T3 – T4 ) KW k

ξ ξ = = = OVERALL EFFICIENCY Wt - Wc Q f ( T3 – T4 ) – ( T2 – T1 ) OUTPUT INPUT * 100 ( T3 – T4 ) – ( T2 – T1 ) T3 – T2 = * 100 ( T3 –T2) – (T4 – T1 ) T3 – T2 = * 100

OVERALL EFFICIENCY ξ T 1 – ( T4 – T1 ) ( T3 – T2 ) = * 100

ξ ξ To improve * EXHAUST TEMP. T4 TO BE AS LOW AS POSSIBLE = 1 – To improve ξ T = 1 – ( T4 – T1 ) ( T3 – T2 ) * 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

ξ ξ ξ ξ ξ 1 – AMBIENT TEMPERATURE = 20 C EXAMPLE FIND 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 T1 = 20 + 273 = 293 K T3 = 950 + 273 = 1223 K T4 = 490 + 273 = 763 K T2 = 300 + 273 = 573 K O ξ = 1 – ( T4 – T1 ) ( T3 – T2 ) ξ = 1 – ( 763 – 293 ) ( 1223 – 573 ) ξ = 1 – ( 470 ) ( 650 ) ξ = 1 – ( 0.72 ) ξ = 0. 28 = 28%

ENTHALPY AND KINETIC ENERGY h = Cp T Cp = 0.24 Btu / Ib F Cp = 1.01 KJ / kg C

Two shaft Gas Turbine AIR Gas Compressor Combustion Chamber POWER LOW PRESSURE 6000 RPM COMP HIGH PRESS 9000 RPM COMPRESSOR LOW PRESSURE 6000 RPM TURBINE HIGH PRESS 9000 RPM AIR Combustion Chamber POWER TURBINE 5000 RPM Gas Compressor