MS5001 PA Complete Maintenance MANUAL

7/27/2019 MS5001 PA Complete Maintenance MANUAL

1/986

g

GE Power SystemsOil & Gas

Technical Training

MS5001 PA

GAS TURBINE

Operation and Maintenance

Training Manual

Customer: AGIP GAS BV LYBIAN BRANCH

Plant location: WAFA COAST- LYBIA


2/986MOD. ARGE 2/S

INDEX

CHAP. 1Page

1. INTRODUCTION................................................................................................1-1

1.1 STATIONARY APPLICATIONS .............................................................1-1

1.2 MOBILE APPLICATIONS........................................................................1-2

1.3 HISTORICAL NOTES...............................................................................1-2

1.4 NUOVO PIGNONE GAS TURBINE MANUFACTURING PLANT ......1-3

09-98-E P. 1-0


3/986MOD. ARGE 2/S

09-98-E P. 1-1

1. INTRODUCTION

A gas turbine is an internal combustion motive machine. From all points of view, it canbe considered as a self-sufficient system: in fact, it is capable to aspirate and compress

ambient air via its own compressor, to enrich the energetic power of air in its own

combustion chamber and to convert this power into useful mechanical energy during the

expanding process that takes place in its own turbine section. The resulting mechanical

energy is transmitted via a coupling to a driven operating machine, which produces work

useful for the industrial process in which the gas turbine belongs.

1.1 STATIONARY APPLICATIONS

These applications are the subject of this traning course. They are intended for the

following industrial uses:

Generator drive, in order to produce electric energy by an open cycle.

Generator drive, to produce electric energy by a combined cycle.

Generator drive, to produce electric energy by co-generation.

Compressor drive

Pump drive

Pipeline compressor drive

Pipeline pump drive

Particular industrial processes


4/986MOD. ARGE 2/S

09-98-E P. 1-2

1.2 MOBILE APPLICATIONS

These applications were the first ones to be introduced in terms of time. Theyinclude the following fields:

railways

marine propulsion

aviation

road traction

1.3 HISTORICAL NOTES

The first gas turbines to be used in operating applications appeared on the market

at the end of the Forties; they were generally used in railways and presented the

advantage of burning liquid fuel, even of poor quality. In this regard, we will

mention the MS3001 turbine built by General Electric, with a power of 4500 HP,

which was used just for this purpose.

Successive achievements in material technology and extensive research into

combustion resulted in rapid improvements in performance, in terms of specificpower and efficiency, obtained by increasing maximum temperatures in the

thermodynamic cycle.

In this matter, three generations of evolution can be defined, distinguished by the

maximum temperature (C) ranges of gases entering the first rotor stage of the

turbine:

First generation 760


5/986MOD. ARGE 2/S

09-98-E P. 1-3

1.4 NUOVO PIGNONE GAS TURBINE MANUFACTURING PLANT

Nuovo Pignone has built gas turbines of heavy duty type for industrial applicationssince 1961. These are made in the Florence workshop under a Manufacturing

Agreement with General Electric, Schenectady - N.Y. - USA, which, in time, has

led to the acquisition of complete licences (MS5002 gas turbine) and to the

complete execution of some gas turbine models (turbines of the PGT range),

starting from engineering and on to all construction phases.

As a complement to their main activities, Nuovo Pignone converts gas turbines

intended originally for the aircraft industry into packages for industrial applications

which use the originary gas generator in conjunction with power turbines made

by General Electric (LM range), or by Nuovo Pignone (PGT16 and PGT25

ranges).Since 1962 up to the present time, Nuovo Pignone has built about 1000 turbines,

complete with all auxiliaries required for their operation; of these, a good deal are

part of turnkey plants for all application purposes listed at para. 1.1.


6/986MOD. ARGE 2/S

09-98-E P. 1-4

In the following tables, gas turbines currently produced by Nuovo Pignone are divided

by model and by type of application.

TABLE 1.1 GAS TURBINES FOR MECHANICAL DRIVE APPLICATIONS(1)

Model Continuous Heat Rate RPM

duty on the

Power load side

KW Kj/Kwh

PGT 2 2180 13360 22500

PGT 5 5500 13680 10290

PGT 5 R 4850 10530 10290

PGT 10 10440 10590 7900

MS 3002 10890 13480 6500

MS 3002 R 10440 10480 6500

PGT 1614260 9935 7900

PGT 25 23270 9565 6500

H.S.P.T 29980 8935 6100

LM 2500 22670 9720 3600

MS 5002(D) 32600 11890 4670

LM 5000 34450 9960 3600

MS 6001 41010 10780 5100

LM 6000 44850 8435 3600

MS 7001 86280 10750 3600

_____________________________

(1) The values in the table refer to the turbine loading flange, under ISO conditions andthe use of natural gas.


7/986MOD. ARGE 2/S

09-98-E P. 1-5

Model Continuous Heat Rate Hz

duty on

Power load side

KW Kj/Kwh

PGT 2 2150 13536 60/50

PGT 5 5500 12852 60/50

PGT 10 10700 11052 60/50

PGT 16 13760 10295 60/50

PGT 25 22450 9910 60/50

H.S.P.T 28930 9260 60/50

LM 2500 22330 10110 60/50

MS 5001 26300/27830 12650/12640 60/50

LM 5000 33060 10270 60/50

MS 6001 38340/41400 10780 60/50

LM 6000 43450 8710/ 60/50

MS 6001 FA 70140 10530 60/50

MS 7001 EA 83500/90200 11060 60

MS 9001 E 123400/133000 10850 50

MS 9001 EC 169200 10300 50

MS 9001 FA 226500 10090 50

_____________________________(1) The values in the table refer to the turbine loading flange, under ISO conditions and the

use of natural gas.

TABLE 1.2 TURBINE S FOR GENERATOR DRIVE APPLICATIONS

(1)


8/986NTRODUCTION

P. 1-4

GE 2 (PGT 2)

OverviewOverviewOverviewOverviewOverviewThe GE2 is a 2MW single shaft machine for base load power generation. Thanks to the high exhaust tem-

perature, the GE2 is perfectly suited for cogeneration in industrial and civil applications (over 5MW ofthermal power) and emergency electric power generation. The single combustion chamber can operate with

a wide variety of liquid and gaseous fuels (or dual fuels) and it is designed to reduce environmental impact

to a minimum, thus satisfying the most restrictive environmental regulations. The load reduction gear is

integrated with the gas turbine and provides output speeds suitable for power generation (1500/1800 RPM).

A microprocessor system for regulation, control and protection has been designed to render the management

and operation of the GE2 gas turbine completely automatic.

Design InfoDesign InfoDesign InfoDesign InfoDesign InfoCompressor

Two stage centrifugal compressor

Pressure ratio 12.5:1

Combustion

Single, combustion chamber

Turbine

Two stage turbine

Investment cast blades, forged discs

Package

The complete Gen Set ismounted on a single baseplate

The enclosure is integral with the baseplate providing maximum accessibility for gas

turbine and auxiliaries maintenance; noise level < 85dB (A) at 1m

In outdoor applications the filter plenum is flanged on top of the enclosure

The package design is standardized for quick delivery; custom applications can beprovided

Package dimensions (including generators and filters) LxWxH = 5.5mx3.8mx2.3m;

Weight = 12t

Emissions Control

Steam or water injection for standard combustion chamber

Dry Low Emission configuration available to satisfy the most stringent environmental

regulations

Performance InfoPerformance InfoPerformance InfoPerformance InfoPerformance InfoGenerator Drive (Expected Performance at ISO Conditions with fuel natural gas)

Model Output Heat Rate Exhaust Flow Exhaust TemperatureGE2 2000 kWe 14400 kJ/kWh 10.7 kg/s 525 C


9/986INTRODUCTIONS

P. 1-5

GE 5 (PGT 5)

OverviewOverviewOverviewOverviewOverviewThe PGT5 heavy-duty gas turbine has been designed with modular concepts to facilitate accessibility and

maintainability.The gas generator consists of a 15-stage, high efficiency, axial-flow compressor directly coupled to a single

stage turbine.

The low pressure shaft (two-shaft version) is a single-stage, high-energy turbine, with variable second stage

nozzles which grant maximum flexibility for mechanical drive service.

The PGT5 has a single combustion chamber system which is rugged, reliable and able to burn a wide range

of fuels, from liquid distillates and residuals to all gaseous fuels, including low BTU gas.

Typical applications include pump drive for oil pipelines and compressor drive for gas pipelines.


Axial flow compressor, 15 stages


Combustion

Single, reverse flow combustion can

TurbineTwo shafts

High Pressure turbine one reaction stage

Low Pressure turbine one reaction stage

Package

The gas turbine module on a single baseplate includes the engine, starting system, auxilia-

ries and acoustic enclosure

Std. Configuration (excluding inlet/exhaust ducts/system):

size 8mLxWxH = 8.5mx2.5mx3.0m

weight 28 t

Emissions Control

DLE combustion system

Steam and water injection system

Performance InfoPerformance InfoPerformance InfoPerformance InfoPerformance Info

Generator Drive: Single Shaft version(Expected Performance at ISO Conditions with fuel natural gas)

Model Output Heat Rate Exhaust Flow Exhaust Temperature

PGT5 5220 kWe 13422 kJ/kWh 24.6 kg/s 524 C

Mechanical Drive:Two Shafts version (Expected Performance at ISO Conditions with fuel natural gas)


PGT5 5450 kW 13450 kJ/kWh 25.8 kg/s 533 C


10/986NTRODUCTION

P. 1-6

GE 5B (PGT 5B)OverviewOverviewOverviewOverviewOverviewThe GE5B series is a 6 MW range industrial duty gas turbine designed in two configurations: A single shaft

configuration for power generation and a two shaft configuration for mechanical drive applications. The

completely new design of the GE5B combines the technology of aircraft engine design with the ruggednessof the heavy duty PGT class of turbines. The flexibility, simplicity and compactness of the GE5B make it

ideal for industrial power generation, including steam production, Oil & Gas applications in remote areas

and Offshore installations. The control system is configured for fully automatic operation and has provisions

for connection to Remote Monitoring and Diagnostics. The GE5B is ideally suited for applications, which

require a continuous supply of electrical power with high availability and reliability. The exhaust energy is

enough to provide a substantial quantity of steam at various pressures and temperatures when coupled to a

Heat Recovery Steam Generator.



First three stator stages are variable geometry

Pressure ratio 15:1

Combustion

Annular combustion chamber, 18 fuel nozzles

Turbine

Two reaction stages

First stage cooled

Package

The gas turbine module on a single baseplate includes engine, starting system, load gear,

auxiliaries and acoustic enclosure

The off-base equipment is limited to the lube oil coolers and electric generator

The inlet filtration module is designed for mounting above the gas turbine enclosure

The enclosure has wide double-joined doors allowing for ease of access to all turbinecomponents and auxiliaries or engine removal

The package design is standardized for quick delivery; custom applications can be

provided

Package dimensions (including filters on top of the enclosure)

LxWxH = 5.9mx2.5mx5.7m;Weight = 30t

Emissions Control

The standard unit is configured with a DLE combustion system



GE5 5500 kWe 11720 kJ/kWh 19.7 kg/s 571 C


11/986INTRODUCTIONS

P. 1-7

PGT 10A (two shaft)

OverviewOverviewOverviewOverviewOverviewThe PGT10 is a high efficiency gas turbine designed and developed by Nuovo Pignone for shaft outputs

ranging between 9,500 and 15,000 HP at ISO conditions. Since first introduced to the market in 1988, the

PGT10 has met its design goals by providing customers with high performance and high reliability and

availability while keeping its design simplicity and easy maintenance concepts. To achieve high

efficiencies over an extended spectrum of power range, an uncommon combination of features has been

incorporated into the design: High pressure ratio, firing temperature level in line with second generation gas

turbines, variable axial compressor stator vanes and power turbine nozzles. The PGT10 combustion system

consists of a single combustion chamber designed for low NOx emissions and is suitable for a large variety

of gaseous and liquid fuels. Typical applications for PGT10 two-shaft gas turbines are not only natural gas

compression, centrifugal pump drive and process application, but also power generation as well as

Cogeneration and Offshore applications.




Combustion

Single combustion chamberTurbine (Two shafts)

High Pressure turbine two stages

Low Pressure turbine two reaction stages

Package

The gas turbine module on a single baseplate includes the engine and a load gear; the

auxiliaries are installed on a separate baseplate joined to that of the gas turbine to form a

single lift on which the sound-insulated enclosure is mounted

The electric generator is installed on a concrete foundation to limit overall shipping

dimension

The package design is standardized for quick delivery, but custom applications can be

provided

Package dimensions (excluding generator and filters) 9.1mx2.5mx3.0m; Weight: 32t

Emissions Control

The combustion system is available both in conventional and DLE configuration to

satisfy the most stringent environmental regulations

Steam and water injection systems are available for NOx reduction and power augmenta-

tion

Performance InfoPerformance InfoPerformance InfoPerformance InfoPerformance InfoGenerator Drive: Two Shaft version(Expected Performance at ISO Conditions with fuel natural gas)


PGT10 10220 kWe 11540 kJ/kWh 42.1 kg/s 484 C



PGT10 10660 kW 11250 kJ/kWh 42.3 kg/s 493 C


12/986NTRODUCTION

P. 1-8

GE 10B (single/two shaft) (PGT 10B 1/2)OverviewOverviewOverviewOverviewOverviewThe GE10 is a high efficiency and environmental friendly Heavy Duty Gas Turbine designed and developed

by Nuovo Pignone for Power Generation (including industrial co-generation) and Mechanical Drive appli-

cations.Since it was first introduced to the market in 1988, the model PGT10A has been providing high perform-

ance, reliability and availability to worldwide customers while keeping with easy maintenance concepts.

From this starting point, in 1998 Nuovo Pignone launched on the market the high performance version of

this model with two different configurations:

Two shafts for mechanical drive and single shaft for power generation and cogeneration applications.

The GE10 Gas Turbine, with its ability to burn different fuels (natural gas, distillate oil, low BTU fuel), can

be installed in many countries with different environmental conditions: continental, tropical, offshore and

desert.

Continuous improvement of the model is carried out with reference to performance and emissions reduction

capability. In this context particular emphasis has been placed on the design of a DLN system for Nitrogen

Oxides (NOx) reduction in order to meet present and future standards for pollutant emissions.



First three stages of stator are variable geometry

Pressure ratio 15.5:1Combustion

Single combustion chamber

Turbine

Single shaft GE10/1 Two shaft GE10/2

Three reaction stages High Pressure turbine two reaction stages (cooled)

First two stages cooled Low Pressure turbine two reaction stages

Package

The gas turbine module on a single baseplate includes the engine and the load gear; the auxiliaries

are installed on a separate baseplate joined to that of the gas turbine to form a single lift on which

the sound-insulated enclosure is mounted

The electric generator is installed on a concrete foundation to limit overall shipping dimensions

The package design is standardized for quick delivery; but custom applications can be provided Package dimensions (excluding generator and filters) LxWxH = 9mx2.5mx3; Weight = 40t

Emissions Control

The combustion system is available both in conventional and DLN configuration to satisfy strin-

gent environmental regulations

Steam and water injection systems are available for NOx reduction and power augmentation


Generator Drive: Single Shaft version(Expected Performance at ISO Conditions with fuel natural gas)


GE10 11250kW 11467 kJ/kWh 47.3 kg/s 490 C


Model Output Heat Rate Exhaust Flow Exhaust Temperature GE10 11690 kW 11060 kJ/kWh 46.9 kg/s 487 C


13/986INTRODUCTIONS

P. 1-9

PGT 16

OverviewOverviewOverviewOverviewOverviewThe PGT16 gas turbine is composed of the twin spool GE Aeroderivative LM1600 Gas Generator coupled

with a rugged, industrial power turbine designed by Nuovo Pignone.

The LM1600 Gas Generator is derived from the F404 turbofan aircraft engine, while the power turbine of the

PGT16 gas turbine is identical to the power turbine of the PGT10 Nuovo Pignone Heavy Duty, high effi-

ciency gas turbine, which has been in operation for more than half a million hours.

The power turbine shaft speed (7900 RPM) is optimized for direct coupling to pipelines and injection and

process centrifugal compressors with speed ranges that suit all operating conditions.

High efficiency and reliability are just two of a large number of benefits contributing to LM2500+ customer

value.

For generator drive applications the LM1600, coupled to its synchronous generator with a speed reduction

gear, is a highly flexible turbogenerator that can also cover combined cycle/cogeneration applications with

an electrical efficiency close to 50%.

Design Info

Compressor Twin spool axial compressor (3 stages LP compressor, 7 stages HP compressor)


Combustion

Annular combustion chamber (18 fuel nozzles)

Turbine

Twin Spool Gas Generator turbine (1 stage HP turbine, 1 stage LP turbine)

Two stages Power turbine (7900 RPM) with variable angle first stage nozzles

Package

The complete gas turbine module is mounted on a single baseplate

The enclosure is integrated with the baseplate providing maximum accessibility for gas

turbine and auxiliaries maintenance

Standard Configuration (excluding inlet/exhaust ducts/system):

Size LxWxH = 8.1mx2.5mx3.8m

Weight 19t

Emissions Control

Steam or water injection systems for NOx abatement

Dry Low Emission (DLE) combustion system

Performance InfoPerformance InfoPerformance InfoPerformance InfoPerformance InfoGenerator Drive: (Expected Performance at ISO Conditions with fuel natural gas)


PGT16 13735 kWe 10314 kJ/kWh 47.4 Kg/s 493 C

Mechanical Drive: (Expected Performance at ISO Conditions with fuel natural gas)

Model Output Heat Rate Exhaust Flow Exhaust TemperaturePGT16 14252 kW 9756 kJ/kWh 47.4 kg/s 493 C


14/986NTRODUCTION

P. 1-10

PGT 25OverviewOverviewOverviewOverviewOverviewThe PGT25 gas turbine consists of the GE Aeroderivative LM2500 Gas Generator coupled with a rugged,

industrial power turbine designed by Nuovo Pignone. The LM2500 gas generator and the PGT25 power

turbine demonstrated the best overall performances to cover the 17,000-31,000 HP range with maximumefficiency above 37%.

The speed of the output shaft, 6500 rpm, as well as the high capacity and simplicity of maintenance have

made the PGT25 highly suitable for driving direct coupled centrifugal compressors for pipeline service or

natural gas reinjection plants. Its light weight and high efficiency makes it well suitable for offshore and

industrial power generation.

The modular design, extended to all accessory equipment, takes into account the special requirements of

platform applications (minimum weights and overall dimensions), as well as drastically reduces erection

time and costs.

The gas generator can be easily dismantled with a simple translation within the package space, thus reduc-

ing the time required for maintenance.

Simplicity of construction and the high quality of the materials employed allow for long intervals between

overhauls and reduced maintenance costs.


Sixteen stages axial compressor


Combustion


Turbine

Two stages Gas Generator turbine

Two stages Power turbine (6500 RPM)

Package

The complete gas turbine module comes mounted on a single baseplate

The enclosure is integrated with the baseplate providing for maximum accessibility for gasturbine and its auxiliaries maintenance


LxWxH = 9.1mx3.5mx3.7m ,Weight 38t

Emissions Control





PGT25 22417 kWe 9919 kJ/kWh 68.9 Kg/s 525 C

Mechanical Drive: (Expected Performance at ISO Conditions with fuel natural gas)Model Output Heat Rate Exhaust Flow Exhaust Temperature

PGT25 23260 kW 9560 kJ/kWh 68.9 kg/s 525 C


15/986INTRODUCTIONS

P. 1-11

MS 5001

OverviewOverviewOverviewOverviewOverviewThe MS5001 single shaft turbine is a compact heavy-duty turbine designed for long life and easy mainte-

nance.The MS5001 gas turbine is the ideal solution for industrial power generation where low maintenance,

reliability and economy of fuel utilization are required.

Low investment costs make the MS5001 package power plant an economically attractive system for peak

load generation.

The MS5001 is ideally suited for cogeneration achieving very high fuel utilization indexes and allowing for

considerable fuel savings. Typical applications are industrial plants for cogeneration of power and process

steam or in district heating systems.



Pressure ratio 10.5:1Combustion

Can-annular combustion, 10 chambers

Turbine

2 stages

First stage nozzles cooled

Package

Complete turbine package mounted on a single baseplate

Enclosure integrated with the baseplate providing maximum accessibility for gas turbine

and auxiliaries maintenance

Standard configuration (excluding inlet/exhaust ducts/system):

size LxWxH = 11.6mx3.2mx3.7m;

weight 87.5tEmissions Control


Dry Low NOx (DLN) combustion system



MS5001 26300 kWe 12650 kJ/kWh 124.1 kg/s 487 C


16/986NTRODUCTION

P. 1-12

MS 5002OverviewOverviewOverviewOverviewOverviewThe MS5002 gas turbine was launched in the 1970s and it has been updated and up-rated along the years to

match the higher power demand.

Presently two versions are available:

MS5002C - 38000 HP at ISO condition

MS5002D - 43700 HP at ISO condition.

The MS5002 is a gas turbine specifically designed for mechanical drive applications with a wide operating

speed range to meet operating conditions of the most common driven equipment, centrifugal compressors

and pumps. It also has the capability to burn a large variety of gaseous and liquid fuels.

Almost 500 units (more than 300 of which were manufactured by Nuovo Pignone) have been installed

world-wide in all possible environments including arctic, desert, offshore, etc., always demonstrating easy

operability as well as very high reliability and availability. The simple design and robustness of the ma-

chine allow for complete maintenance to be performed on site without the need for special tools or service

shop assistance. Typical applications include Gas Boosting, Gas Injection/Reinjection, Oil & Gas Pipelines,

LNG plants and Gas Storage

Design InfoDesign InfoDesign InfoDesign InfoDesign Info

CompressorMS5002C

Sixteen stages axial compressor


MS5002D

Seventeen stages axial compressor


Combustion

Reverse flow, multi chamber (can-annular) combustion system (12 chambers)

Turbine

Single stage Gas Generator turbine

Single stage power turbine (4670 RPM rated speed) with variable angle nozzles.

Package

Two baseplates configuration (gas turbine flange to flange unit and auxiliary system.

Enclosures integrated with the baseplates providing maximum accessibility for gas turbine



size LxWxH = 15.0mx3.2mx3.8m

weight 110t

Emissions Control



Performance InfoPerformance InfoPerformance InfoPerformance InfoPerformance InfoMechanica Drive (Expected Performance at ISO Conditions with fuel natural gas)


MS5002C 28340 kW 12310 kJ/kWh 126.0 kg/s 515 C

MS5002D 32590 kW 11900 kJ/kWh 141.3 kg/s 510 C


17/986INTRODUCTIONS

P. 1-13

PGT 25+

OverviewOverviewOverviewOverviewOverviewThe PGT25+ gas turbine has been developed for 30 MW ISO shaft power service with the highest thermal

efficiency level (approx. 40%).The PGT25+ gas turbine consists of the GE Aeroderivative LM2500+ Gas Generator (updated version of

LM2500 gas generator with the addition of zero stage to axial compressor) coupled with a 6100 RPM Power

Turbine. Built on the LM2500 heritage and with demonstrated 99.6% reliability, the PGT25+ incorporates

proven technology improvements and a large percentage of parts in common with LM2500 in order to

deliver the same outstanding level of reliability. Designed for its ease of maintenance, the PGT25+ also

provides a high level of availability.

High efficiency and reliability are just two of large number of benefits contributing to PGT25+ customer

value.

Application flexibility makes the PGT25+ ideal for a range of mechanical drive (gas pipeline etc.), power

generation, industrial cogeneration and offshore platform applications in any environment.

Design InfoDesign InfoDesign InfoDesign InfoDesign Info

Compressor Seventeen stages axial compressor


Combustion


Turbine

Two stage Gas Generator turbine

Two stage Power turbine (6100 RPM)

Package

Gas Generator, Power Turbine and auxiliary System mounted on a single baseplate




size LxWxH = 6.5mx3.6mx3.9m (gas turbine and auxiliary baseplate)

weight 38t (gas turbine and auxiliary baseplate)

Emissions Control





PGT25+ 30226 kWe 9084 kJ/kWH 84.3 Kg/s 500 C

Mechanical Drive: (Expected Performance at ISO Conditions with fuel natural gas)Model Output Heat Rate Exhaust Flow Exhaust Temperature

PGT25+ 31360 kW 8754 kJ/kWh 84.3 kg/s 500 C


18/986NTRODUCTION

P. 1-14

MS 6001

OverviewOverviewOverviewOverviewOverviewThe MS6001 is a single shaft heavy-duty gas turbine. Its design was based on the well proven mechanical

features of the MS5001 in order to achieve a compact, high efficency unit.The MS6001 is widely applied in power generation applications for base, mid-range and peak load service.

Other typical applications include driving of process machines, such as compressors, in LNG plants.

Combined cycle plants based on MS6001 achieve very high efficiencies with higher availability and

reliability than conventional thermal plants.




Combustion


Dual fuel capability

Turbine 3 stages, first two cooled buckets

First 2 stage nozzles cooled

Package

Complete turbine package mounted on a single baseplate

Enclosure integrated with the baseplate providing for maximum accessibility for gas

turbine and its auxiliaries maintenance


size LxWxH = 15.9mx3.2mx3.8m;

weight 96t

Emissions Control





MS6001B 42100 kWe 11230 kJ/kWh 145.8 kg/s 552 C



MS6001B 43530 kW 10825 kJ/kWh 145 kg/s 544 C

ExperiencesExperiencesExperiencesExperiencesExperiences

More than 46 units sold


19/986INTRODUCTIONS

P. 1-15

LM 6000

OverviewOverviewOverviewOverviewOverviewThe GE LM6000 delivers more than 44.8 MW of power at over 42.7% thermal efficiency.

It is the worlds most fuel-efficient, simple-cycle gas turbine. High efficiency, low cost and easy installationmake the LM6000 the perfect modular building block for electrical power applications such as industrial

cogeneration of utility peaking, both midrange and base-load operations. As an aircraft engine aboard the

Boeing 747, the LM6000 has logged more than 10 million flight hours, with the lowest shop visit rate of

any jet engine.

Continuing the tradition of GEs LM6000 established record, the LM6000 is ideal as a source of drive-

power for pipeline compression, offshore platforms, gas reinjection and LNG compressors. The LM6000 has

been GEs first aeroderivative gas turbine to employ the new Dry-Low Emission premixed combustion

system; this system is retrofittable on LM6000s already in operation. Water or steam injection can also be

used to achieve low NOx emissions.


Low pressure compressor 5 stages

High pressure compressor 14 stages

Pressure ratio 30:1Combustion

Annular combustion chamber

Turbine

High Pressure turbine 2 stages

Low Pressure turbine 5 stages

Package

Gas Generator, Power Turbine and auxiliary system mounted on a single baseplate





weight 31t

Emissions Control

Steam or water injection system for NOx abatement



Generator Drive: (Expected Performance at ISO Conditions with fuel natural gas)


LM6000 43076 kWe 8707 kJ/kWh 131 Kg/s 450 C


Model Output Heat Rate Exhaust Flow Exhaust TemperatureLM6000 44740 kW 8455 kJ/kWh 127 kg/s 456 C


20/986NTRODUCTION

P. 1-16

MS 7001

OverviewOverviewOverviewOverviewOverviewThe MS7001EA is a single shaft heavy-duty gas turbine for power generation and industrial applications

requiring the maximum reliability and availability.With design emphasis placed on energy efficiency, availability, performance and maintainability, the

MS7001EA is a proven technology machine with more than 500 units of its class in service.

Typical applications in addition to the 60Hz power generation service are large compressor train drives for

LNG plants.


Seventeen stages axial compressor


Combustion

Reverse flow, multi chamber (can-annular) combustion system (10 chambers)

Turbine

Three stages turbine (3600 RPM)

Package

Two baseplates configuration (gas turbine flange to flange unit and auxiliary system)





weight 121t

Emissions Control






MS7001EA 85100 kWe 11000 kJ/kWh 300 kg/s 537 C



MS7001EA 81590 kW 11020 kJ/kWh 278 kg/s 546 C


21/986INTRODUCTIONS

P. 1-17

MS 9001OverviewOverviewOverviewOverviewOverviewThe MS9001E is a single shaft heavy-duty gas turbine. It was developed for generator drive service in the 50

Hertz market.The MS9001E is widely applied in power generation for base, mid-range and peak load service.

Combined cycle plants based on MS9001E achieve very high efficiencies with higher availability and

reliability than conventional thermal plants.




Combustion


Dual fuel capability

Turbine

3 stages, first two cooled buckets

First 2 stage nozzles cooledPackage

Two baseplates configuration (gas turbine flange to flange unit and auxiliary system)





weight 217.5

Emissions Control






MS9001E 123400 kWe 10650 kJ/kWh 412.8 kg/s 543 C

ExperiencesExperiencesExperiencesExperiencesExperiences

44 Units sold


22/986NTRODUCTION

P. 1-18

GE 5 (1/2 shaft) 5,2 - 5,4 MW 26,9 %

GE 5 B 5,9 - 6,2 MW 32 %

PGT 10 10,5 MW 32,6 %

GE 10 B(1/2 shaft) 11,7 MW 33 %

PGT 16 14,2 MW 36,9 %

PGT 25 23,2 MW 37,7 %

MS 5001 26,3 MW 28,5 %

MS 5002 C-D 28,3 -32,5 MW 29,2 - 30,3%

PGT 25+ 29,9 MW 40, 3 %

MS 6001 B 42 MW 32,5 %

LM 6000 44,8 MW 41,1 %

MS 7001 EA 81,5 MW 32,7 %

MS 9001 E 123,4 MW 33,8 %

GE 2 2,0MW 25 %

TYPE POWER MAX EFFiCIENCY


23/986MOD. ARGE 2/S

INDEX

CHAP. 2Page

2. THEORETICAL OPERATING SCHEME .........................................................2-1

2.1 OPERATING PRINCIPLE ........................................................................2-2

2.2 MAIN COMPONENT PARTS OF A GAS TURBINE .............................2-4

2.2.1 Compressor .....................................................................................2-5

2.2.2 Combustion section ........................................................................2-62.2.3 Turbine section ...............................................................................2-7

2.3 BRAYTON CYCLE ...................................................................................2-7

2.4 INFLUENCE OF EXTERNAL FACTORS ON

GAS TURBINE PERFORMANCE .........................................................2-14

2.5 INFLUENCE OF INTERNAL FACTORS ON

GAS TURBINE PERFORMANCE .........................................................2-16

09-98-E P. 2-0


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2. THEORETICAL OPERATING SCHEME

Fig. 2.1 shows an example of a gas turbine (in this specific case, it is our MS6001 gasturbine) with a sectional view of the machine properly said. This figure has the purpose

to highlight the main component parts involved in the operating cycle.

Fig. 2.1 - Example of a simple cycle gas turbine (single shaft)

The main component parts illustrated in Fig. 2.1 are:

machine, generally calledflange - flange

auxiliary equipment

baseplate

The above systems are completed by the suction, exhaust and control systems,

which, like the auxiliary equipment and the baseplate, are dealt with in the relevant

chapters, whereas here only details about their arrangement and interface with the

flange-flange assembly (Fig. 2.1) are described.

In fact, this chapter deals exclusively with the operating principles of a flange-

flange.

BASAMENTO

AUSILIARI FLANGIA-FLANGIA

BASEPLATE

FLANGE TO FLANGEAUXILIARIES


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2.1 OPERATING PRINCIPLE

A gas turbine works in the following way:

it aspirates air from the surrounding environment;

it compresses it to a higher pressure;

it increases the energy level of compressed air by the addition of fuel gas

which undergoes combustion in a combustion chamber;

it directs high pressure and high temperature air to a turbine section, which

converts thermal energy into mechanical energy that makes the shaftrevolve; this serves, on the one hand, to supply useful energy to the driven

machine, coupled to the machine by means of a coupling and, on the other

hand, to supply energy necessary for air compression, which takes place in

a compressor connected directly with the turbine section itself;

it expels low pressure and low temperature gases resulting from the above-

mentioned converting process into the atmosphere.

Fig. 2.2 overleaf shows the behavioral pattern of pressures and temperatures, in

terms of quality, inside the different machine sections corresponding to the above-

mentioned operating phases.


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Fig. 2.2


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Fig. 2.2 enhances the fact that combustion takes place under almost constant

pressure conditions.

Unlike alternative motors, compression and expansion take place on a continualbasis, as happens for power generation.

On the contrary, in an alternative motor (for ex., a four-stroke, eight cycle motor),

though power is generated in the expansion phase, like in a turbine, this process

takes only 1/4 of the complete cycle, whereas in a gas turbine expansion takes place

continually all through the cycle. The same applies to compression.

For the same reason, along with the fact that there are no masses in alternate

motion, the degree of regularity of the running cycle of a gas turbine is incomparably

greater than that of an alternative motor (eight or Diesel cycle).

2.2 MAIN COMPONENT PARTS OF A GAS TURBINE

Fig. 2.3 - A sectional View of a Gas Turbine

A gas turbine (Fig. 2.3) is composed of three main sections, described in the following

paragraphs. As concerns design and construction features, these are extensively dealt with in

Chapter 3.


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2.2.1 Compressor

The compressor shall be of the axial type (Fig. 2.3). The choice of this typeof compressor depends on the fact that this compressor is capable to deliver

high air output ratings, necessary to obtain high values of useful power in a

reduced size. This concept will be resumed later, when the main

thermodynamic ratios in the operating cycle of a gas turbine are described.

A compressor consists of a series of stages of rotating blades, which increase

air speed in terms of kinetic energy, followed alternately by stages of stator

blades, which convert kinetic energy into higher pressure.

The number of compression stages is related to the structure of the gas

turbine and, above all, to the compression ratio to be obtained.At the compressor inlet side, there are Inlet Guide Vanes (or, IGV), whose

primary purpose is to direct air, delivered by the suction system, towards the

first stage of rotating blades. Another important function of IGVs is to

ensure a correct behaviour by the compressor, in terms of fluid dynamics,

under different transient operating conditions (for example, during start-up

and shut down) when, due to different running speeds as apposed to normal

operating speed, the opening angle of IGVs is changed: this serves to vary

the air delivery rate and to restore ideal speed triangles in transient phases.

Finally, in combined cycles and in the co-generation process, the capability

to change the geometrical position of IGVs permits to optimise temperaturesat the turbine exhaust side and, thus, to increase the efficiency of the recovery

cycle by varying the flow rate of the air entering the compressor.

At the compressor output side there are a few stages of Exit Guide Vanes or

EGV, necessary to obtain maximum pressure recovery before air enters the

combustion chamber.

The compressor serves also to supply a source of air needed to cool the walls

of nozzles, buckets and turbine disks, which are reached via channels inside

the gas turbine, and via external connecting pipings. Additionally, the

compressor supplies sealing air to bearing labyrinth seals.


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2.2.2 Combustion Section

In the case of "heavy duty" gas turbines as the one shown in Fig. 2.3, thecombustion section consists of a system of one or more tubular combustion

chambers (in this specific case there are ten combustion chambers) arranged

symmetrically and evenly in a circumference; these chambers receive and

burn fuel by means of an equal number of burners (one per combustion

chamber).

Air enters each chamber with a flow direction inverse to that of the hot gases

inside (for this reason, this method of air distribution is called "reverse

flow"). This external flow, which marginally touches the various chambers,

serves to cool them. In addition, the part of air that does not take part in thecombustion process is used for cooling the combustion products; in fact, it

is introduced into the chambers through diluition holes until optimal

temperature conditions are established to allow the gas and air mixture into

the turbine section.

Air passage from the combustion section properly said to the gas turbine

inlet takes place inside manifolds called transition pieces; here, the gases

flowing out of the single combustion chambers are led to form a continuous

annular profile, equal to the one that leads into the first stage nozzles ring.

Initially, the combustion process is ignited by one or more spark plugs. Once

ignited, combustion proceeds in a self-sufficient way without the help of

spark plugs, as long as the delivery conditions of fuel and combustion air are

fulfilled.

In the case of gas turbines built for the aviation industry (LM , PGT16 and

25 range), the combustion section consists of a single chamber of toroidal

shape, with direct and not "reverse flow" cooling; in fact, this helped reduce

external diametral sizes, since a smaller frontal section was needed in order

to offer as little resistance as possible to aircraft motion.

For the same reason, this combustion chamber does not need any separate

transition pieces. The other operating principles are the same as those

described for tubular chambers.


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2.2.3 Turbine Section

In the case of "heavy duty" turbines, as shown in Fig. 2.1, the turbine sectioncomprises a certain number of stages (in this specific case, three stages), each

one of them consisting of one stator stage (distributor nozzle); in this stage,

high temperature and high pressure gases delivered by the transition piece

described beforehand are accelerated and directed towards the rotor stage of

buckets mounted on a disk connected with the power shaft.

As mentioned before (para. 2.1), the conversion of thermal energy and

pressure into kinetic energy takes place in the stator stage.

The rotor stage completes this conversion, as here kinetic energy is

transformed into energy that drives the shaft, thus generating the power

required to drive the compressor (internal compression work, cannot be usedas externally useful work) and to operate the driven machine (generator,

compressor, etc.) connected to the gas turbine by means of a coupling.

The energy of gases supplied by the combustion system can be varied by

changing the delivery rate of fuel. In this way you can regulate the useful

power values needed for the technological process of which the gas turbine

is the motor.

2.3 BRAYTON CYCLE

The thermodynamic cycle according to which a gas turbine works is known asthe Brayton cycle.

Fig. 2.4 illustrates a diagram of a gas turbine (in this specific case, an MS6001

single shaft turbine). This diagram is useful to understand the meaning of the

thermodynamic cycle more easily.

Fig. 2.4 - Gas Turbine Operating Diagram

Air enters the compressor at point (1), which represents ambient air conditions. These

conditions are classified according to pressure, temperature and relative humidity values.


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It was agreed that standard design conditions be classified as ISO Conditions, to which there

correspond the following reference values:

ISO CONDITIONS

Ambient temperature (C) 15

Ambient pressure (mbar) 1013

Relative humidity (%) 60

Afterwards, air is compressed inside the compressor, and exits in the condition indicated at

point (2). During the converting process from (1)to(2),no heat is released outside. However,air temperature increases, due to polytropic compression, up to a value variable depending on

gas turbine model and ambient temperature.

After leaving the compressor, air enters the combustion area, practically under the same

pressure and temperature conditions as at point (2)(except for losses undergone on the wayfrom the compressor delivery side to the combustion chamber inlet, which amount to about 3

to 4% of the absolute value of delivery pressure). Fuel is injected into the combustion chamber

via a burner, and combustion takes place at practically constant pressure.

Conversion between points(2)and(3)represents not only combustion. In fact, the temperature

of the combustion process properly said, which takes place under virtually stechiometric

conditions, reaches excessively high values (around 2000 C) locally in the combustion area

next to the burner, due to the resistance of materials downstream.

Therefore, the conversion final temperature, relative to point(3),is lower, as it is the result ofprimary gases mixing with cooling and dilution air as described previously.

In this regard, it is useful to give some definitions of temperature at point (3), which is the

maximum cycle temperature or firing temperature (see Fig. 2.5).


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Fig. 2.5 - Firing temperature

SectionA refers to the so-called "turbine inlet temperature", which is the averagetemperature of gases in plane A.

Section Brefers to the so-called firing temperature, which is the average gas

temperature in plane B.

SectionCrefers to the so-called ISO firing temperature", which is the average gas

temperature in plane C, calculated as a function of the air and fuel flow rates via

a thermal balance of combustion according to the ISO 2314 procedure.

The difference in the interpretation of temperatures in sections Aand Bconsists

in the fact that, on gas turbines like those which we are dealing with in this training

course, in section Bwe take into account the mixture of 1st stage nozzle cooling

air, which was not involved in the combustion process, but mixes with burnt gasesafter cooling the surface of the nozzle.

According to the Nuovo Pignone - General Electric standard, the temperature that

best represents point (3)is the one in section B.


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The following transformation, comprised between points (3) and (4), represents

the expansion of gases through the turbine section, which, as mentioned before,

converts therma energy and pressure into kinetic energy and, thanks to therevolutions of the power shaft, into work used for compression (internal, not

useable) and external useful work, thanks to the connection with an operating

machine.

Over 50% of the energy developed by expansion in the gas turbine is absorbed by

the axial compressor for its compressing work.

Downstream of section (4), gases are exhausted into the atmosphere.

The thermodynamic representation of the events described so far is visible in Fig.

2.6 (pressure diagrams - volume P-V and temperature - entropy T-S).

Fig. 2.6 - Brayton Cycle

In the cycle illustrated in the above figure, the 4 points correspond to the same

described before.

In particolar, note the compression and expansion transformations, obviously

these are not isoentropic.

In this respect, please remember that:

thespecific compression work Wc

, from (1) to(2), is expressed with good

approximation by the following ratio:

Wc = Cpm(T2-T1) (T2-T1) (Kj/Kgasp. air)

thespecific expansion work Wt

, from(3) through(4), is expressed by:

Wt = Cpm(T3-T4) (T3-T4) (Kj/Kggas.)

Heat Q1, supplied to the combustion chamber from(2)to(3),is expressed by:

Q1 = Cpm(T3-T2) (T3-T2) (Kj/Kggas.)


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The gas turbine cycle "closes" ideally with the transformation from (4)to (1),

which corresponds to the cooling of exhaust gases, in that heat Q2is aspirated out

into the atmosphere, as though the latter were a refrigerant of infinite capability.The thermodynamic ratio that describes the cooling process of exhaust gasesis

the following:

Q2 = Cpm(T4-T1) (T4-T1) (Kj/Kggas.)

The various values for Cpm

, expressed in the preceding ratios, represent the average

specific heat at constant pressure between the extreme temperature values in the

interval examined.

For a more rigorous evaluation, it would be necessary to proceed by means of

integral calculation.

Once Q1, Q

2, W

cand W

t, are known, you can obtain the valuesforthe following

significant parameters:

Thermodynamic efficiency= (Q1- Q

2)/Q

1

This ratio means that, by parity of heat Q1, introduced into the combustion chamber

by fuel, efficiency will increase as heat Q2

decreases, dissipated into the

atmosphere. We will see in Chap. 8 how to recover this heat partially in combined

cycles and in the regenerative cycle.

Useful work Nusupplied to the driven machine= G

gasW

t- G

ariaW

c

In the latter ratio, Ggas and Garia correspond respectively the weight of gasesdelivered to the turbine inlet section, and to the air aspirated by te compressor,

necessary to pass from specific to global values.

So far, all descriptions and examples refer to a single shaft turbine like MS 6001.

In fact, in the diagram illustrated in Fig. 2.4, the entire turbine section is connected

mechanically witht the axial compressor.

Such types of single shaft turbines are suitable for driving operating machines that

run at constant speed, such as alternators and, for this reason, are used typically in

the generation of electric energy.

In applications, in which power regulation is achieved by means of speed variationin the driven machine, two-shaft gas turbines are usually employed (see diagram

in Fig. 2.7); in this case, the turbine is divided into two mechanically separate

sections:

A high pressure section, which runs at constant speed within a wide range

of powers, and drives exclusively an axial compressor.

A low pressure section, connected with the operating machine via a coupling;

this section can vary its running speed independent of the high pressure

turbine section.


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This configuration, with the addition of other elements which will be described in

Chapter 4, serves to regulate the driven machine speed without the need to vary the

speed of the axial compressor; thus, the latter may continue to run at its designspeed, with optimal efficiency.

Fig. 2.7 - Two Shaft Gas Turbine Diagram

The ratios described so far apply in general to all machine types.

The classical concepts of thermodynamics permit to give a correct evaluation to

the Brayton cycle and to the influence by parameters such as pressures, temperatures,

specific heats, polytropic exponents, etc.

A diagram in Fig. 2.8 expresses the ratios among the following parameters:

Firing temperature T3(C) Compression ratio

Thermal efficiency

Specific power (KW/(Kg/sec.))


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Fig. 2.8 - Relations between significant thermodynamic quantities

This diagram indicates that:

a) under equal temperature T3, maximum efficiency is reached by increasing

the compression ratio. The maximum efficiency value does not corresponds

to the maximum specific power.

b) The higher the increase in the compression ratio, the greater the benefit

provided by increased firing temperature T3

for specific power and

efficiency values.

However, it is not possible to exceed certain values for T3, because of

limitations imposed by the resistance of the materials currently available.

The increase in temperature T3represents therefore a very important parameter

that requires vast and constant efforts in the research about materials, blade

cooling technology, etc., in order to achieve reliable and efficient products

capable to meet ever growing demands by the market.

c) Specific power is important, because, to a higher specific power there

corresponds a gas turbine of smaller size, though of equal power output.

d) Efficiency is important, because the higher the efficiency, the lower the

consumption and operating costs.


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2.4 INFLUENCE OF EXTERNAL FACTORS ON GAS TURBINE PER-

FORMANCE

A gas turbine uses ambient air, therefore, its performance is greatly affected by allfactors that influence the flow rate of air delivered to the compressor, in terms of

weight.

These factors are:

Temperature

Pressure

Relative humidity

In this regard, we remind you that reference conditions for the three above-

mentioned factors are, by convention, ISO standards (para. 2.3).

As the compressor inlet temperature increases, there increases the specific

compression work, while the weight of the air delivered decreases (because of a

decrease in specific weight ). Consequently, the turbine efficiency and useful

work (and, therefore, power) diminish as well. If temperature decreases, the

reverse occurs.

This dependence of temperature on the air aspirated by the compressor and power

and efficiency varies from turbine to turbine, according to cycle parameters,

compression and expansion output and air delivery rate.

Fig. 2.9 shows an example of how power, specific consumption (heat rate) and the

delivery rate of exhaust gases depend on ambient temperature.

Fig. 2.9 - Influence of ambient temperature on turbine performance


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Specific consumption, dimensionally represented in figure 2.9 as HEAT RATE,

is the inverse of efficiency, in that it indicates the ratio between thermal energy,

resulting from the combustion process, and mechanical energy, supplied to thepower shaft (or to the generator terminals, if we consider the performance of a load

gear and generator, if present).

To summarise, we call Q1

the energy resulting from combustion and Nu the

external useful work: thus, specific consumption or Heat Rate is defined as:

HR = Q1/Nu

and is generally expressed as Kj/Kwh.

If the atmospheric pressure decrases in comparison with the ISO reference

pressure, there decreases the weight of air delivered (because of a reduction in its

specific weight) and, proportionally, there decreases the useful power, which is

proportional to the weight of the gas delivered. On the contrary, the other

parameters of the thermodynamic cycle (HR, etc.) are left uninfluenced.

Fig. 2.10 shows the percentage pattern of the useful power of a gas turbine in

relation to its installation altitude.

Fig. 2.10

ATMOSPHERIC

PRESSURE

ALTITUDE - 1000 FEET

CORRECTION

FACTOR

CORRECTION

FACTOR

ATMOSPHERIC

PRESSURE


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Relative humidity influences the specific weight of air aspirated by the compressor.

In fact, humid air is less dense than dry air, so if the relative humidity increases,there

decreases the power output and there increases specific consumption (HR) (Fig.2.11).

In the past, such an effect used to be neglected. Nowadays, as ever more powerful

gas turbines are made and humidity is added in the form of water or steam by

reduction of NOx, this effect must be taken into consideration.

Fig. 2.11

2.5 INFLUENCE OF INTERNAL FACTORS ON GAS TURBINE PERFORM-

ANCE

Next to the three external factors described in the preceding paragraph, there are

other factors which notably affect the performance of a gas turbine. These may be

called internal factors, because they are related to the auxiliary systems of the gas

turbine.

They are the following:

Pressure drop in the compressor inlet section

Pressure drop in the turbine exhaust system

Fuel type

Air extraction from the axial compressor

Steam injection

Water injection

Evaporative cooling


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Pressure drops in the compressor inlet section

Pressure drops are caused by the gas turbine suction system, composed of an

airfiler, a silencer, a length of duct, pipe section regulators, etc., installed upstreamof the compressor suction flange. When air flows through this system, it is

subjected to friction, which reduces its pressure and thus its specific weight. These

drops cause a reduction in useful power and an increase in specific consumption

or "heat rate", as mentioned previously in the case of the influence exerted by

ambient pressure.

Pressure drops in the turbine exhaust system

These are caused by the exhaust system of the gas turbine, composed of one or

more silencers, a length of duct, a recovery boiler (in the case of combined cycles

or co-generation), diverters, shutters, etc., through which exhaust gases areexpelled into the atmosphere.

Exhaust gases flowing through this system are subjected to friction, which

increases the value of back pressure as opposed to the value of external, atmospheric

pressure. This reduces the amount of turbine expansion, as the latter terminates

one isobar higher than the reference one, which results in reduced useful power

and increased specific consumption (heat rate).

Table 2.1 reports the typical values by which performance is dependent on pressure

drops at the compressor inlet section and at the turbine exhaust section. For the

reasons explained above, this dependance is proportional to the values of pressure

drop.TABLE 2.1 EFFECTS OF PRESSURE DROPS

Every 100 mm H2O at suction : Every 100 mm H2O at exhaust :

1.42 % power loss 0.42 % power loss

0.45 % increase in Heat Rate 0.42 % increase in Heat Rate

1 C increase in exhaust temperature 1 C increase in exhaust temperature

Fuel gas influence

Best performance is achieved if natural gas rather than diesel oil is used. In fact,

output power under base load power and under equal conditions (environmental,pressure drops , etc.) will be about 2% greater and specific consumption (Heat

Rate) between 0.7 and 1% lower, depending on gas turbine model.

These differences will become all the more remarkable if we compare performances

obtained with natural gas and with progressively "heavier"fuel types, such as

residuals, Bunker C, etc.

This behavior is due to the higher heating power of products originated by the

combustion of natural gas, as the latter has a higher content of water vapour,

resulting from a higher ratio between hydrogen and carbon, which is typical of

methane, the main component part of natural gas.


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Gaseous fuels with a lower calorific value than natural gas (commonly called "low

btu gases") can greatly influence the performance of a gas turbine.

In fact, if the calorific value diminishes (Kj/Nm3

), the weight of fuel delivered tothe combustion chamber must increase to provide the necessary amount of energy

(Kj/h).

This addition in the weight of the fluid, which is not even compressed by the

compressor, provokes an increase in power (see the definition of useful workat

para. 2.3) and a reduction in specific consumption.

In this case, the power absorbed by the compressor is left substantially unvaried.

However, in the case of combustion of low btu gases, the following side effects

must be taken into consideration:

An increase in the weight of fluid delivered to the turbine increases thecompression ratio in the compressor, which must not come too near the

surging limit.

An increase in the fuel delivered often requires larger diameters of tubings

and control valves (and, consequently, higher costs). This effect is all the

more conspicuous in the case in which also the temperature of a gas and,

therefore, its specific volume, are higher (for example, gases produced by

coal gassing).

Gases with a low calorific value are frequently enough saturated with water

vapour upstream of the gas turbine combustion system. This provokes an

increase in the coefficients of heat transmission by combustion products,and an increase in metal temperature on hot parts of the turbine.

Air extraction from the axial compressor

On some gas turbine applications (chemical processes, pipe blowing during the

commissioning stage, etc.) it may become necessary to extract compressed air

from the compressor delivery side.

As a general rule, and unless prescribed otherwise in the case of machines

originally built for the aviation industry, it is possible to extract as much as 5% of

the air delivered by the compressor without the need to alter the turbine layout at

all.It is possible to achieve extraction values ranging between 6 and 20 % , depending

on the machine and combustion chamber configuration, if alterations are made to

casings, pipings and the control system.

Fig. 2.12 shows how percentages of air extraction influence output power and

specific consumption (heat rate), taking into consideration also ambient temperature.


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Fig. 2.12

Steam injection and water injection

Steam or water injection may have the following two purposes:

a reduction in nitrogen oxide (NOx) level.

an increase in output power.

Reducing the nitrogen oxide (NOx) level

The method of steam or water injection was introduced in the early 70s to limit and

control the presence of nitrogen oxides or NOX.

Injection is usually performed in the area where the combustion chamber cap is

present. The injection system is built in a way to set a limit to the amount of

injectable steam or water, in order to safeguard stability and continuity in the

combustion process. Anyway, the amount of steam and water injected is sufficientto guarantee a massive reduction in the level of NOx.

According to the amount of steam or water injected into the combustion chamber,

which the turbine control system automatically monitors in relation to the NOx

level desired, output power will increase consequently to an increase in the mass

of fluid delivered through the gas turbine.

In the case of steam injection, the Heat Rate or specific consumption will also

decrease for the same reasons that apply to fuel gases with a low calorific value.

On the contrary, the latter advantage does not exist in the case of water injection,

as here a higher quantity of fuel is needed to vaporize water to the condition that

allows it to be injected into the combustion chamber.

HEATRATE(%)

HEAT

RATE(%)


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In condition of peak duty, with a maximum of 1250 hours/year, it is possible to

increase the water delivered through the combustion chamber cap area in order to

increase the gas turbine power output. Obviously, this calls for shorter maintenanceintervals.

As concerns the maximum water flow rates and maintenance procedures, these

must be evaluated case by case, depending on the machine model and its

combustion system.

Output power increase

Steam injection for increasing the gas turbine output power has been available and

warranted by over 30 years' experience.

Unlike water, steam is injected into the compressor exhaust casing, thus eliminating

all limitations imposed in order to safeguard stability in the combustion process.For this reason, the maximum amount of injectable steam is limited to percentage

values of the weight of air aspirated by the compressor.

Steam must be overheated, and there must be at least 25 C difference with respect

to the compressor delivery temperature; steam supply limit pressure must be at

least 4 bar(g) greater than maximum pressure in the combustion chamber.

In the case of steam or water injection, the amount of steam injected in conditin

of partial load must be equal to the amount required to abate NOx. Once the load

base value is reached, the control system gives the OK to inject the additional

steam needed to increase the turbine output power.


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Fig. 2.13 shows the typical effects of steam injection on the output power of a gas

turbine (in this case, an MS 5002 gas turbine) as a function of ambient temperature.

Fig. 2.13 - Effects of steam injection on output power(MS5002 Gas Turbine)


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COALESCER/DEMISTER

SUMP TANK

CELLE AD EVAPORAZIONE

COLLETTORE H2O

POMPA DI CIRCOLAZIONE H2O

ARIA REFRIGERATA

VERSO IL FILTRO

DELLARIA

ARIA CALDAAMBIENTE

Evaporative cooling

Curves in fig. 2.9 show clearly how power and efficiency increase as the

compressor inlet temperature decreases.The latter can be reduced artificially by using an evaporative cooler located

upstream of the suction filter.

Water, fractioned into drops or in the form of a liquid film, cools the air by

evaporating in the cooler as it flows in contrary direction, thus originating an

adiabatic-isoenthalpic exchange (see fig. 2.14).

Fig. 2.14 Evaporative cooler

In order to prevent water from being drawn towards the compressor and fouling it,

downstreams of the cooler there are one or more stages of drop separators

(demisters), which, by inertia, separate any water drops that might be carried away

downstream of the cooler by the flow of air aspirated by the turbine.

Fig. 2.15 shows the effects of evaporative cooling on the gas turbine output power

and specific consumption.

As can be noted, benefits increase as relative humidity decreases and ambient

temperature increases.

Unfortunately, the above requirements are met in environments (for example,

deserts), in which water is not always available in the amounts needed by the

cooler.

COOLED AIR

TOWARD AIR

FILTER

AMBIENT HOT AIR

EVAPORATION CELLS

H20 HEADER

COALESCER/DEMISTER

SUMP TANK

H20 CIRCULATING PUMP


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Fig. 2.15 Effects of Evaporative Cooling on Performance

Inlet chillingIn environments in which a high degree of average relative humidity is present

(higher than 60%) and ambient temperatures are not excessively high, it is

advisable to cool air with a different method, commonly called "inlet chilling";

according to this method, air is cooled during a refrigerating cycle (based generally

on absorption) carried out in a closed circuit. In this way, the restrictions imposed

by relative humidity and by ambient temperature, described in the preceding

system, can be eliminated. The minimum temperature reached by air at the end of

the cooling process is strictly dependent on the capability of the refrigerating cycle

to produce cold liquid and on the efficiency of the thermal exchange that takes

place in the water - air exchanger.

Figure 2.16 shows an operating diagram of this system (in this example, steam

is used for the absorption cycle), composed of a chiller, water connecting pipings

and a water - air exchanger, installed downstream of the gas turbine suction filter.

Same as in evaporative cooling, also in this case it is necessary to install a

coalescer/demister downstream of the system, in order to prevent humidity from

reaching the compressor inlet section.


47/986MOD. ARGE 2/S

09-98-E P. 2-24

Fig. 2.16 Air "chilling cooling" system, based on absorption

Figure 2.17 shows a comparison between the cooling powers of the two systems.

Fig. 2.17 Comparison psychometric chart

DRENAGGIO

CHILLER

CAMERA

FILTRI

SCAMBIATORE

DEMISTER/COALESCER

ARIA AMBIENTE

ARIA FREDDA VERSO

IL COMPRESSORE

INGRESSO VAPOREALLA TORRE DI RAFFREDDAMENTO

INGRESSO AC UA FREDDA

RITORNO AC UA DA RAFFREDDARE

% RH const. lines

Saturation line

constant moisture content line

Kgwater/Kgaira

b

c

d

TaTc Td

constant enthalpy line

PSYCHROMETRIC

CHART

Tb

DEMISTER/COALESCER

COOLED AIR

TOWARD COMPRESSOR

DRAIN

CHILLER

STEAM INLETTO COOLING

TOWER

FILTERS

CHAMBERAMBIENT AIR

HEAT EXCHANGER

COOLING WATER INLET


48/986MOD. ARGE 2/S

09-98-E P. 2-25

Line a - d represents air cooling in the case of evaporative cooling. As mentioned

before, this line follows the constant enthalpy line, resulting in a progressive

increase in relative humidity.The restriction imposed by this cooling method consists in the fact that there

remains a minimum distance from the saturation curve, compatibly with realistic

exchange surfaces, considered from the point of view of construction. Normal

values indicate around 90% relative humidity, that is, there still remains a 10%

margin before the saturation line is reached.

Under these conditions, the final air temperature is equal to Td.

In the case of the chilling process, the cooling line has a constant moisture content

along segment a - b. If the potential of the refrigerating cycle and the efficiency of

the exchanger allow it, cooling can reach the saturation line and follow it along

segment b - c, in which heat is removed to form condensate (H2O). In this secondsegment, there is a smaller temperature reduction, because most of the cooling

energy serves for the condensing process and only a small part of it participates

in lowering temperature.

In the chilling system, the air final temperature will be equal to Tb or Tc, according

to the chosen degree of cooling.


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