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GE Power Systems

GE AeroderivativeGas Turbines - Designand Operating Features

G.H. BadeerGE IADGE Power SystemsEvendale, OH

GER-3695E

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Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Selection of Aeroderivative Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

LM1600 Gas Turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4LM2500 Gas Turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5LM2500+ Gas Turbine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5LM6000 Gas Turbine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6LM6000 Sprint™ System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8STIG™ Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Design and Operation of GE Aeroderivative Gas Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . 12Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Fuels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Ratings Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Performance Deterioration and Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Maintenance Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Advances in Aircraft Engine Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

GE Aeroderivative Gas Turbines - Design and Operating Features

GE Power Systems ■ GER-3695E ■ (10/00) i


GE Power Systems ■ GER-3695E ■ (10/00) ii

AbstractAeroderivative gas turbines possess certain tech-nical features inherent in their design heritagewhich offer operational and economic advan-tages to the end user. This paper presents anoverall description of GE's current LM series ofaeroderivative gas turbines with power outputranging from 13 to 47 MW. It discusses opera-tional and economic considerations resultingfrom GE’s aeroderivative gas turbine designphilosophies, and the value of these considera-tions in a customer’s gas turbine selectionprocess.

GE's total research and development budget foraircraft engine technology is approximately onebillion dollars a year. Today’s entire GE gas tur-bine product line continues to benefit from thisconstant infusion research and developmentfunding. Advances are constantly being madewhich improve GE’s gas turbine benefits to thecustomer.

IntroductionHeadquartered in Cincinnati, OH, GE’sIndustrial Aeroderivative Gas Turbine Division(GE-IAD) manufactures aeroderivative gas tur-bines for industrial and marine applications.GE Power Systems sells and services the current

gas turbine products, which include theLM1600, LM2500, LM2500+ and LM6000. Inaddition, the LM2000 is offered as an integrat-ed packaged product including an LM2500 gasturbine at reduced rating.

Figure 1 presents the performance characteris-tics for power generation applications, whileFigure 2 presents the product line’s perform-ance characteristics for mechanical drive appli-cations.

GE’s aeroderivative industrial products are pro-duced in two configurations:

■ Gas turbine, made up of a GE-suppliedgas generator and power turbine

■ Gas generator, which may be matchedto an OEM-supplied power turbine.

These turbines are utilized in simple cycle,STIG™ (Steam Injected Gas Turbine) applica-tions for power enhancement, or integratedinto cogeneration or combined-cycle arrange-ments. GE also produces a variety of engine-mounted, emissions control technologies,described in Figure 3.

Selection of Aeroderivative EnginesPrior to commencing production of a newaeroderivative gas turbine based on the current


GE Power Systems ■ GER-3695E ■ (10/00) 1

GE INDUSTRIAL AERODERIVATIVE GAS TURBINE PERFORMANCE CHARACTERISTICSGENERATOR DRIVE GAS TURBINE RATINGS

OUTPUT HEAT RATE EXHAUST FLOW EXHAUST TEMP. FREQUENCYMODEL FUEL kWe Btu/kWhr kJ/kWhr lb/s kg/s deg F deg C Hz

LM1600PA G 13750 9624 10153 103 46.7 910 488 50/60D 13750 9692 10225 103 46.7 928 498 50/60

LM2000 G 18000 9377 9892 139 63 886 474 60LM2500PE G 22800 9273 9783 152 69 974 523 60

D 22800 9349 9863 152 69 994 534 60LM2500PK G 30700 8815 9300 192 87.2 959 515 50/60

D 29600 8925 9415 189 85.8 965 518 50/60LM2500PV G 30240 8598 9071 186 84.3 931 499 60

D 28850 8748 9229 182 82.5 941 505 60LM6000PC G 43315 8198 8648 277 126 845 451 60

D 42111 8293 8748 276 125 851 455 60G 42665 8323 8779 277 126 845 451 50D 41479 8419 8881 276 125 851 455 50

LM6000PD G 42227 8246 8698 275 125 841 449 60D 41505 8331 8787 273 124 854 457 60G 41594 8372 8830 275 125 841 449 50D 40882 8458 8921 273 124 854 457 50

Figure 1. GE aeroderivative product line: generator drive gas turbine performance characteristics

line of aircraft engines, GE considers the fol-lowing factors:

■ Market forecast for marine andindustrial engines

■ Projected performance and pricecompetitiveness of the new line ofaeroderivative engines

■ Degree of difficulty involved inconverting the aircraft engines designinto the new, aeroderivativeconfiguration.

The last point is extremely important. In orderto keep a new aeroderivative product’s overall

cost as low as possible, the aircraft engine cho-sen as the basis for this line must be convertiblefrom aircraft to marine and industrial usage:

■ With very few changes to its originaldesign

■ Using parts which are mass-producedfor the aircraft application.

Figure 4 shows the operating hours accrued foreach of the GE parent engines in flight applica-tions and their derivative engines in industrialand marine service. For example, the LM2500and its parent aircraft engine have over 63 mil-lion hours of operating experience and have



GE INDUSTRIAL AERODERIVATIVE GAS TURBINE PERFORMANCE CHARACTERISTICSMECHANICAL DRIVE GAS TURBINE RATINGS*

OUTPUT HEAT RATE EXHAUST FLOW EXHAUST TEMP.MODEL FUEL sHP kWs Btu/HPhr kJ/kWhr lb/s kg/s deg F deg C

LM1600PA G 19200 14320 6892 9750 103 46.7 910 488D 19200 14320 6941 9820 103 46.7 928 498

LM2500PE G 31200 23270 6777 9587 152 69 974 523D 31200 23270 6832 9665 152 69 994 534

LM2500PK G 42000 31320 6442 9114 192 87.2 959 515D 40500 30200 6522 9227 189 85.8 965 518

LM2500PV G 42000 31320 6189 8756 186 84.3 931 499D 40100 29900 6297 8909 182 82.5 941 505

LM6000PC G 58932 43946 6002 8490 277 126 845 451D 56937 42458 6095 8621 276 125 851 455

LM6000PD G 57783 43089 6026 8524 275 125 841 449D 56795 42352 6088 8611 273 124 854 457

*ISO (15C, 60% RH, SEA LEVEL, NO LOSSES), BASE LOAD, AVERAGE NEW ENGINE

Figure 2. GE aeroderivative product line: mechanical drive gas turbine performance characteristics

ENGINE MOUNTED NOx ABATEMENT METHODS

MODELGAS

GENERATORGAS

TURBINESIMPLE CYCLE

COMBINED CYCLE STIG

WATER INJECTION

STEAM INJECTION DLE

LM1600 X X X X X X X XLM2000 X X X X X X X XLM2500 X X X X X X X X

LM2500+ X X X X X X XLM6000 X X X X X X

Figure 3. GE aeroderivative product line: available equipment arrangements

QUANTITY OPERATING HOURS QUANTITY OPERATING HOURSLM1600 (F404) 3400 7,000,000 146 3,500,000

LM2500 (TF39/CF6-6) 1130 32,300,000 1767 31,200,000

LM6000 (CF6-80C2) 2806 58,700,000 300 3,200,000

Data as of February, 2000

AIRCRAFT AERODERIVATIVE

Figure 4. Aircraft and aeroderivative engine operating experience as of February 2000

demonstrated excellent reliability. All GEAeroDerivative engines benefit from this com-bined experience.

The following sections will introduce and sum-marize the key characteristics of each of theindividual LM model gas turbines. Configur-ation terminology and arrangement options aredefined in Figure 5.

The following features are common to all LMmodel gas turbines:

■ A core engine (compressor,combustor, and turbine)

■ Variable-geometry for inlet guide andstator vanes

■ Coated combustor dome and liner

■ Air-cooled, coated, high-pressureturbine (HPT) blading

■ Uncooled power turbine blading

■ Fully tip-shrouded power turbine rotorblading

■ Engine-mounted accessory gearboxdriven by a radial drive shaft.

The LM1600 and LM6000 are dual-rotor units.A rotor consists of a turbine, drive shaft, and

compressor. The low-pressure rotor consists ofthe low-pressure turbine (LPT), which drivesthe low-pressure compressor (LPC) via a con-centric drive shaft through the high-pressurerotor. The high-pressure rotor is formed by thehigh-pressure turbine driving the high-pressurecompressor (HPC). The LM2000, LM2500 andLM2500+ are single-rotor machines that have

one axial-flow compressor, and an aerodynami-cally coupled power turbine.

The LM1600, and LM6000 employ electronical-ly operated, variable-bleed valves arranged inthe flow passage between the low- and high-pressure compressors to match the LPC dis-charge airflow to the HPC. These valves arefully open at idle and progressively close to zerobleed at approximately 50% power. The posi-tion of these variable-geometry controls is afunction of the LP rotor speed, HP rotor speedand inlet air temperature.

Aeroderivative engines incorporate variablegeometry in the form of compressor inlet guidevanes that direct air at the optimum flow angle,and variable stator vanes to ensure ease of start-ing and smooth, efficient operation over theentire engine operating range.



Combustor

HPC

ExhaustInlet

Fuel

LPC HPT

LPT

PT

Load Load

Variable Stators

Variable Bleed

Variable IGV

Core Engine

Figure 5. Gas turbine terminology and arrangement

Aeroderivative turbines are available with twotypes of annular combustors. Similar to thoseused in flight applications, the single annularcombustor features a through-flow, venturiswirler to provide a uniform exit temperatureprofile and distribution. This combustor config-uration features individually replaceable fuelnozzles, a full-machined-ring liner for long life,and an yttrium-stabilized zirconium thermalbarrier coating to improve hot corrosive resist-ance. In 1995, a dry, low emissions (DLE) com-bustor was introduced to achieve low emissionswithout the use of fuel diluents, such as water orsteam.

The LM1600, LM2000, LM2500, and LM2500+all include an aerodynamically coupled, high-efficiency power turbine. All power turbines arefully tip-shrouded. The LM1600 PT andLM2500+ High Speed Power Turbine (HSPT)feature a cantilever-supported rotor. The powerturbine is attached to the gas generator by atransition duct that also serves to direct theexhaust gases from the gas generator into thestage one turbine nozzles. Output power istransmitted to the load by means of a couplingadapter on the aft end of the power turbinerotor shaft. Turbine rotation is clockwise whenviewed from the coupling adapter looking for-ward. Power turbines are designed for frequent

thermal cycling and can operate at constantspeed for generator drive applications, and overa cubic load curve for mechanical drive appli-cations. The LM6000 power turbine drives boththe LPC and the load device. This feature facil-itates driving the load from either the front oraft end of the gas turbine shaft.

All of the models have an engine-mounted,accessory drive gearbox for starting the unitand supplying power for critical accessories.Power is extracted through a radial drive shaftat the forward end of the compressor. Drivepads are provided for accessories, including thelube and scavenge pump, the starter, the vari-able-geometry control, and the liquid fuelpump.

LM1600 Gas Turbine The LM1600 gas turbine consists of a dual-rotorgas generator and an aerodynamically coupledpower turbine. The LM1600 is shown in Figure6, and consists of a three-stage, low-pressurecompressor; a seven-stage, variable-geometry,high-pressure compressor; an annular combus-tor with 18 individually replaceable fuel nozzles;a single-stage, high-pressure turbine; and a sin-gle-stage, low-pressure turbine. The gas genera-tor operates at a compression ratio of 22:1.



Figure 6. LM1600 gas turbine

The LM1600 incorporates variable-geometry inits LPC inlet guide vanes and HPC stator vanes.Four electronically operated, variable-geometrybleed valves match the discharge airflowbetween the LPC and HPC. In industrial appli-cations, the nozzles and blades of both the HPTand LPT are air-cooled and coated with“CODEP,” a nickel-aluminide-based coating, toimprove resistance to oxidation, erosion, andcorrosion. For marine applications, HPT noz-zles are coated with a thermal barrier coating,LPT nozzles are coated with CODEP and theblades of both the HPT and LPT are coatedwith PBC22. The two-stage power turbineoperates at a constant speed of 7,000 rpm overthe engine operating range for generator driveapplications, and over a cubic load curve formechanical drive applications.

LM2500 Gas Turbine The LM2500 gas turbine consists of a single-rotor gas turbine and an aerodynamically cou-pled power turbine. The LM2500 (Figure 7)consists of a six-stage, axial-flow design com-pressor, an annular combustor with 30 individu-ally replaceable fuel nozzles, a two-stage, high-pressure turbine, and a six-stage, high-efficiencypower turbine. The gas generator operates at acompression ratio of 18:1.

The inlet guide vanes and the first six-stages ofstator vanes are variable. In both stages of the

high-pressure turbine, the nozzles and bladesare air-cooled. For industrial applications, thenozzles are coated with CODEP and the bladesare coated with platinum-aluminide to improveresistance to erosion, corrosion and oxidation.

The six-stage power turbine operates at a nomi-nal speed of 3,600 rpm, making it ideal for 60Hz generating service. Alternatively, it can beused in 50 Hz service without the need to add aspeed reduction gear. The LM2500 can alsooperate efficiently over a cubic load curve formechanical drive applications.

The LM2500 gas turbine is also offered at an18MW ISO rating as an integrated packagedproduct called the LM2000 with an extendedhot-section life for the gas turbine.

LM2500+ Gas Turbine The first LM2500+, a design based on the verysuccessful heritage of the LM2500 gas turbine,rolled off the production line in December1996. The LM2500+ was originally rated at 27.6MW, for a nominal 37.5% thermal efficiency atISO, no losses and 60 Hz. Since that time, its rat-ing has continually increased to reach its cur-rent level of 31.3 MW and 41% thermal effi-ciency. An isometric view of the LM2500+ gasturbine, including the single annular combus-tor (SAC), is shown in Figure 8.

The LM2500+ has a revised and upgraded com-




pressor section with an added zero stage forincreased flow and pressure ratio, and revisedmaterials and design in the HP and power tur-bines. The gas generator operates at a compres-sion ratio of 22:1. The inlet end of the LM2500+design is approximately 13 inches/330 mmlonger than the current LM2500, allowing forretrofit with only slight inlet plenum modifica-tions. In addition to the hanging support foundon the LM2500, the front frame of theLM2500+ has been modified to provide addi-tional mount link pads on the side. This allowsengine mounting on supports in the base skid.

The LM2500+ is offered with two types of powerturbines: a six-stage, low speed model, with anominal speed of 3600 rpm; or a two-stage highspeed power turbine (HSPT).

The LM2500+ six-stage power turbine displaysseveral subtle improvements over the L2500model from which it was derived:

■ Flow function was increased by 9%, inorder to match that of the HPC.

■ Stage 1, 5 and 6 blades as well as thestage 1 nozzle were redesigned.

■ Disc sizing was increased for all of thestages.

■ Spline/shaft torque capability wasincreased.

■ Casing isolation from flow path gasesby use of liners stages 1-3.

The LM2500+ two-stage HSPT has a designspeed of 6100 rpm, with an operating speedrange of 3050 to 6400 rpm. It is sold formechanical drive and other applications wherecontinuous shaft output speeds of 6400 rpm aredesirable. When the HSPT is used at 6,100 rpmto drive an electric generator through a speedreduction gear, it provides one of the bestoptions available for power generation applica-tions at 50 Hz.

Both the six-stage and two-stage power turbineoptions can be operated over a cubic load curvefor mechanical drive applications.

In 1998, a version of LM2500+ was introducedto commercial marine application. The only dif-ferences between the marine and industrial ver-sions to address the harsher environment are asfollows:

■ Stage 1 HPT nozzle coating

■ Stage 1 HPT shroud material andcoating.

LM6000 Gas Turbine The LM6000 turbine (Figure 9) consists of a five-stage LPC; a 14-stage HPC, which includes sixvariable-geometry stages; an annular combustorwith 30 individually replaceable fuel nozzles; a



Figure 8. LM2500+ gas turbine

two-stage, air-cooled HPT; and a five-stage LPT.The overall compression ratio is 29:1. TheLM6000 does not have an aerodynamically cou-pled power turbine.

The LM6000 is a dual-rotor, “direct drive” gasturbine, derived from the CF6-80C2, high-bypass, turbofan aircraft engine. The LM6000takes advantage of its parent aircraft engine’slow-pressure rotor operating speed of approxi-mately 3,600 rpm. The low-pressure rotor is thedriven-equipment driver, providing for directcoupling of the gas turbine low-pressure systemto the load, as well as the option of either coldend or hot end drive arrangements.

The LM6000 maintains an extraordinarily highdegree of commonality with its parent aircraftengine, as illustrated in Figure 10. This is unlikethe conventional aeroderivative approachwhich maintains commonality in the gas gener-

ator only, and adds a unique power turbine. Bymaintaining high commonality, the LM6000offers reduced parts cost and demonstrated reli-ability.

The status of the LM6000 program, as ofFebruary 2000, includes:

■ 300 units produced since introductionin 1991

■ 208 units in commercial operation

■ First DLE combustor in commercialoperation producing less than 25 ppmNOx - 1995

■ High time engine =50,829 hours

■ 12 month rolling average engineavailability = 96.8%

■ Engine reliability = 98.8%

■ Exceeded 3.1 million operating hours




LPCompressor

HPCompressor

HPTurbine

LPTurbine Power

Turbine

LPCompressor

HPCompressor

HPTurbine

LPTurbine

Common Unique

Generator or Compressor

Generator or Compressor AlternateGenerator or Compressor

LM6000 Approach

Traditional Approach

Common

Figure 10. LM6000 concept

■ Variable speed mechanical drivecapability – 1998

■ Dual fuel DLE in commercialoperation – 1998

■ LM6000 PC Sprint™ System incommercial operation - 1998

In mid-1995, GE committed to a major productimprovement initiative for the LM6000. Newmodels designated as LM6000 PC/PD were firstproduced in 1997, and included a significantincrease in power output (to more than 43MW) and thermal efficiency (to more than42%); dual fuel DLE; and other improvementsto further enhance product reliability.

LM6000 Sprint™ System Unlike most gas turbines, the LM6000 is prima-rily controlled by the compressor dischargetemperature (T3) in lieu of the turbine inlettemperature. Some of the compressor dis-charge air is then used to cool HPT compo-nents. SPRINT™ (Spray Inter-cooled Turbine)reduces compressor discharge temperature,thereby allowing advancement of the throttle tosignificantly enhance power by 12% at ISO, andgreater than 30% at 90°F (32°C) ambient tem-peratures.

The LM6000 Sprint™ System is composed of

atomized water injection at both LPC and HPCinlet plenums. This is accomplished by using ahigh-pressure compressor, eighth-stage bleedair to feed two air manifolds, water-injectionmanifolds, and sets of spray nozzles, where thewater droplets are sufficiently atomized beforeinjection at both LPC and HPC inlet plenums.Figure 11 displays a cross-section of the LM6000Sprint™ System. Figure 12 provides the Sprint™Gas Turbine expected performance enhance-ment, relative to the LM6000-PC.

Since June 1998, when the first twoSprint™units began commercial operation, tenother installations have gone into service. As ofFebruary 2000, LM6000 Sprint™ Gas Turbine(Figure 13) operating experience exceeds20,000 hours. Sprint™ System conversion kitsfor LM6000 PC models are now available forthose considering a potential retrofit.

STIG™ Systems STIG™ (Steam Injected Gas Turbine) systemsoperate with an enhanced cycle, which useslarge volumes of steam to increase power andimprove efficiency. See Figure 14 for STIG™ sys-tem performance enhancements at ISO baseload conditions.

In the STIG™ cycle, steam is typically producedin a heat recovery steam generator (HRSG) and



8th StageBleed Air Piping

WaterMetering

Valve

24 SprayNozzles

Air atomized spray - Engine supplied air - Droplet diameter less than 20 microns

Orifice

AirManifold

Water Manifold

AirManifold

23 SprayNozzles

Figure 11. LM6000 Sprint™ flow cross section

is then injected into the gas turbine. TheSTIG™ system offers a fully flexible operatingcycle, since the amount of steam injected canvary with load requirements and steam avail-ability. Also, steam can be injected with the gasturbine operating from 50% power to full load.

A typical STIG™ cycle is shown in Figure 15. The

installation includes a steam-injected gas tur-bine, coupled with an HRSG which can be sup-plementally fired. The control system regulatesthe amount of steam sent to process and, typi-cally, the excess steam is available for injection.Figure 16 shows the steam injection capabilityfor the various models.



Sea level, 60% Rel Hum, 5" Inlet/10" Exhaust losses Natural Gas with Water Injection to 25 ppm

25000

30000

35000

40000

45000

50000

55000

40 50 60 70 80 90 100

Engine Inlet Temperature deg F

Sh

aft

Po

wer

kW SPRINT

Base LM6000-PC

30%

12% TM

Figure 12. LM6000 Sprint™ gas turbine performance enhancement

Figure 13. LM6000 Sprint™ gas turbine

Standard Base Load, Sea Level, 60% RH, - Natural Gas - 60 Hertz -4 in. (102mm) Inlet/10 in. (254mm) Exhaust Loss - Average Engine at the Generator Terminals*

Model Dry Rating (MWe) %Thermal Efficiency (LHV) STIG Rating (MWe) %Thermal Efficiency (LHV)

LM1600 13.3 35 16 37LM2000 18 35 23.2 39LM2500 22.2 35 27.4 39

*3% margin on Eff. Included

Figure 14. STIG™ system performance enhancement – generator drive gas turbine performance



Gas turbine~

Air

Fuel SteamHRSG

To process

Exhaust

H2O

Figure 15. Typical STIG™ cycle

Standard Base Load, Sea Level, 60% RH, - Natural Gas - 60 Hertz -4 in. (102mm) Inlet/10 in. (254mm) Exhaust Loss - 25 PPM NOx

Steam Flows -lb/hr (kg/hr)Model Rating (MWe)* %Thermal Efficiency* Fuel Nozzle Compressor Discharge

LM1600 16 37 11540 (5235) 9840 (4463)LM2000 23.2 39 14558 (6604) 15442 (7005)LM2500 27.4 39 18300 (8301) 31700 (14379)

LM2500+ 32.5 40 23700 (10750)LM6000 42.3 41.1 28720 (13027)

* Average Engine at generator terminals (2.5% on LM1600 Gen, 2.0% on all others Gen, 1.5% GB included)

Figure 16. STIG™ steam flow capability – generator drive gas turbine performance

HP Steam to combustor for

NOx abatement

HP Steam for power augmentation

Figure 17. STIG™ system steam injection ports

The site at which steam is injected into the gasturbine differs according to the design of theparticular model. For instance, in both theLM1600, LM2000 and LM2500, steam is inject-ed into the high-pressure section via the com-bustor fuel nozzles and compressor dischargeplenum. See Figure 17 for the location of steaminjection ports on an LM2500 gas turbine. ASTIG™ system is not planned for the LM6000,beyond that steam injected through the fuelnozzles for NOx abatement.

Emissions NOx emissions from the LM1600, LM2000,LM2500, LM2500+ and LM6000 can bereduced using on-engine water or steam injec-tion arrangements, or by the incorporation ofDLE combustion system hardware. The intro-duction of steam or water into the combustionsystem:

■ Reduces NOx production rate

■ Impacts the gas turbine performance

■ Increases other emissions, such as COand UHC

■ Increases combustion system dynamicactivity which impacts flame stability

■ The last item results in a practicallimitation on the amount of steam orwater which can be used for NOxsuppression.

Figure 18 lists the unabated NOx emission levelsfor the GE Aeroderivative gas turbines when

burning either natural gas or distillate oil.Depending on the applicable federal, state,country and local regulations, it may be neces-sary to reduce the unabated NOx emissions.

Figure 19 shows GE’s current, guaranteed mini-mum NOx emission levels for various controloptions. With steam or water-injection and sin-gle fuel natural gas, the LM2500 can guaranteeNOx emissions as low as 15 ppm. For applica-tions requiring even lower NOx levels, othermeans, such as selective catalytic reduction(SCR), must be used.

In 1990, GE launched a Dry Low EmissionsCombustor Development program for itsaeroderivative gas turbines. A premixed com-bustor configuration (Figure 20), was chosen toachieve uniform mixing of fuel and air. Thispremixing produces a reduced heating valuegas, which will then burn at lower flame tem-peratures required to achieve low NOx levels.Increased combustor dome volume is used toincrease combustor residence time for com-plete reaction of CO and UHC. DLE combus-tors feature replaceable premixer/nozzles andmultiple burner modes to match low demand.



ISO - Base Load - SAC CombustorUnabated NOx Emissions (ppmvd ref.15% O2)

Model Natural Gas Distillate Oil LM1600 127 209LM2000 129 240LM2500 179 316

LM2500+ 229 346LM6000 205 403

Figure 18. GE aeroderivative gas turbine unabated NOx emissions

Figure 19. Minimum NOx emission guarantee levels – wet and dry emissions control options

In order to achieve low emissions throughoutthe operating range, fuel is staged through theuse of multiple annuli. The LM1600 uses a dou-ble annular configuration, while all other mod-els use a triple annular construction.

Factory testing of components and engineassembly on an LM6000 gas turbine was com-pleted in 1994. These tests demonstrated lessthan 15 ppm NOx, 10 ppm CO and 2 ppm UHCat a firing temperature of 2350°F/1288°C atrated power of 41 MW.

The Ghent power station in Belgium becamethe first commercial operator to use theLM6000 fitted with the new DLE combustor sys-tem. A milestone was reached in January 1995when the station achieved full power at 43 MWwith low emissions of 16 ppm NOx, 6 ppm COand 1 ppm UHC. As of today, the high timeLM6000 engine has accumulated over 34,000hours.

By the end of 1999, there were 3 LM1600, 58LM2500, 27 LM2500+, and 30 LM6000 gas tur-bines equipped with the DLE combustion sys-tem in service worldwide.

Today, GE continues its DLE technology devel-

opment on the Dual Fuel DLE front.Completely dry operation has been achieved ongas and distillate fuels on two LM6000 enginesin the United Kingdom. Operating on liquidfuel, NOx and CO emission levels have been lessthan 125 ppm and 25 ppm, respectively. GEcontinues to do research on reducing liquidfuel to NOx levels below 65 ppm , with the goalof achieving this by the end of the year 2000. Byearly 2001, GE plans to release a Dual Fuel DLEsystem on the LM2000, LM2500 and LM2500+gas turbines.

Design and Operation of GEAeroderivative Gas Turbines

Design Features GE Aeroderivative gas turbines combine hightemperature technology and high pressureratios with the latest metallurgy to achieve sim-ple-cycle efficiencies above 40%, the highestavailable in the industry.

It is essential to GE’s aeroderivative design phi-losophy that an industrial or marine aeroderiv-ative gas turbine retain the highest possibledegree of commonality with the flight engine



Combustion Liner

Heat Shield

Premixer

Figure 20. DLE combustor

on which the aeroderivative is based. Thisresults in a unique and highly successfulapproach to on-site preventive and correctivemaintenance, including partial disassembly ofthe engine and replacement of componentssuch as blades, vanes and bearings. On-sitecomponent removal and replacement can beaccomplished in less than 100 manhours.Complete gas generators and gas turbines canbe made available within 72 hours (guaran-teed), with the complete unit replaced andback on-line within 48 hours. The hot-sectionrepair interval for the aeroderivative meets theindustrial demand of 25,000 hours on naturalgas. The LM engines have been adapted tomeet the important industrial standards ofASME, API, NEC, ISO9001, etc., consistent withtheir aircraft engine parentage.

Other advantages related to the evolution fromthe flight application are the technical require-ments of reduced size and low weight. Theaeroderivatives’ rotor speeds (between 3,000and 16,500 rpm) and casing pressure (20 to 30atmospheres) may appear high when comparedwith other types of gas turbines. However, thehigh strength materials specified for the aircraftengine are capable of handling these pressuresand rotor speeds with significant stress margins.For example, cast Inconel 718, commonly usedfor aircraft engine casing material, has a yieldstrength of 104 ksi (717 kN/m2) at1200°F/649°C, while cast iron commonly usedin other types of gas turbine casings has a yieldstrength of 40 ksi at 650°F (276 kN/m2 at343°C).

The aeroderivative design, with its low support-ed-weight rotors – for example, the LM2500 HProtor weighs 971 lbs/441 kg – incorporatesroller bearings throughout. These do notrequire the large lube oil reservoirs, coolers andpumps or the pre-and post-lube cycle associated

with other bearing designs. Roller bearingshave proven to be extremely rugged and havedemonstrated excellent life in industrial serv-ice. Although bearings generally provide reli-able service for over 100,000 hours, in practice,it is advisable to replace them when they areexposed during major repairs, or, at an estimat-ed 50,000 hours for gas generators and 100,000hours for power turbines.

The high-efficiency aeroderivative is an excel-lent choice for simple-cycle power generationand cyclic applications such as peaking power,which parallels aircraft engine use. With starttimes in the one-minute range, the aeroderiva-tive is ideal for emergency power applications ofany sort.

With its inherently low rotor inertias, and thevariety of pneumatic and hydraulic startingoptions available, the GE Aeroderivative enginehas excellent “black start capability,” meaningthe ability to bring a “cold iron” machine on-line when a source of outside electrical power isunavailable. An additional benefit of having lowrotor inertias is that starting torques and powerrequirements are relatively low, which in turnreduces the size and installed cost of either thepneumatic media storage system or the dieselor gasoline engine driven hydraulic systems. Forexample, the LM2500 starting torque is lessthan 750 ft-lbs (1,017 N-m), and its air con-sumption during a typical start cycle is between2,000 and 2,600 SCFM (56,600 and 73,600l/min).

Fuels Natural gas and distillate oil are the fuels mostfrequently utilized by aeroderivatives. Theseengines can burn gaseous fuels with heating val-ues as low as 6,500 Btu/lb (15,120 kJ/kg).Recently, an LM6000 with a single, annularcombustor was modified to operate on mediumBtu (8,000-8,600 Btu/lb ~ 18,600-20,000 kJ/kg)



fuel. It demonstrated that it could operate withlower NOx emissions without requiring flame-quenching diluents such as water or steam.

As part of GE’s Research and DevelopmentProgram, an LM2500 combustor, modified toutilize low heating value biomass fuel, has beenoperated in a full annular configuration atatmospheric pressure. A sector of the annularcombustor design was then tested at gas turbineoperating pressures. Ignition, operability, gastemperature radial profiles, temperature varia-tions and fuel switching were in acceptableranges when operated on simulated biomassfuel. Low NOx is a by-product since low heatingvalue fuel is essentially the same as operating ina lean premix mode like the DLE combustor.

Operating Conditions The climatological and environmental operat-ing conditions for aeroderivatives are the sameas for other types of gas turbines. Inlet filtrationis necessary for gas turbines located in areaswhere sand, salt and other airborne contami-nants may be present.

At the extreme ends of the ambient tempera-ture spectrum, the aeroderivative exhibits a lessattractive lapse rate (power reduction at off-ambient temperatures) than other types of gasturbines. However, the LM aeroderivative doeshave a “constant power” performance optionwhich can be applied in areas where theextremes are encountered for extended periodsof time.

Ratings Flexibility All turbines, including aeroderivatives, have“base ratings”. In the case of GE’s aeroderiva-tives, when natural gas is used as the fuel andthe engine is operated at the base power tur-bine inlet temperature control setting, its baserating corresponds to a hot-section repair inter-val of approximately 25,000 hours. The LM2000

is an exception; at its base rating the hot-sectionrepair interval is approximately 50,000 hours.

Aeroderivatives utilize the same basic hardwareas aircraft engines, which are designed to oper-ate reliably at firing temperatures much higherthan the corresponding aeroderivative base rat-ing temperatures. By taking advantage of theextensively air cooled hot-gas-path componentstypically found in aircraft engines, aeroderiva-tive models can operate at higher temperaturesand power levels than their base rating.

The LM2500 will be used as an example, withthe other LM products having similar charac-teristics. Figure 21 illustrates the full capability ofthe LM2500 as a function of ambient tempera-ture. In the ambient temperature region above55°F/13°C, the LM2500’s maximum capabilityis limited by the maximum allowable tempera-ture at the power turbine inlet. Figure 21 alsoshows the availability of additional power abovethe ISO base rating of the unit.

In order to achieve this increased power, opera-tion at increased cycle temperature is necessary.As with any gas turbine, the hot-gas-path sectionrepair interval (HSRI) of the LM2500 is relatedto the cycle temperature. Figure 22 presents therelationship between output power, power tur-



Figure 21. LM2500 maximum power capability

bine inlet temperature and estimated timebetween hot-section repairs. The ISO rating tem-perature corresponds to the curve for an esti-mated 25,000 hours between hot-section repairswhen burning natural gas fuel. Figure 22 alsoshows that power is available for applicationsrequiring more power than is available when lim-iting the temperature to that associated with the25,000 hours curve. However, those LM2500s uti-lizing this additional power will require more fre-quent hot-section repair intervals.

The LM2500, like any gas turbine operating at aconstant cycle temperature, has more poweravailable at lower ambient temperatures than athigher ambient temperatures. This is shown inFigure 22 by the sloping lines of constant hot-section repair intervals (constant power turbineinlet temperature). There are, however, manyapplications in the industrial market that can-not use all of the power that is available at thelower ambient temperatures. In these cases, theoperating characteristic of “constant power,”regardless of the ambient temperature, is moreconsistent with the actual requirements of theinstallation.

Figure 23 shows an example of an application

where constant power, rather than variablepower, is required over a specific ambient tem-perature range. This figure clearly shows thatthe LM2500 is capable of producing this powerover the full ambient temperature range.However, the estimated hot-section repair inter-val for this type of operation is not apparent inFigure 23, since when operating during highambient temperature conditions, the power tur-bine inlet temperature corresponds to shorterintervals than when operating at lower ambienttemperatures.

An ambient temperature profile for the partic-

ular site is needed to determine the duration ofoperation at the various power turbine inlettemperatures. Once this ambient temperatureinformation is available, an estimate of the hot-section repair interval for this power level andparticular site can be made. If the operator doesnot provide duty cycle estimates, it is generallyassumed that a unit operates continuously for8,600 hours per year for any given site.

To carry this example further, assume the ambi-ent temperature profile for this particular siteresults in an estimated hot-section repair inter-val of 25,000 hours for this power level.

Comparison of operation at constant tempera-ture and constant power level is shown in Figure24. Since both curves result in an estimated hot-



Figure 22. Effect of increased power rating onLM2500 hot-section repair interval

Figure 23. LM2500 constant power rating

section repair interval of 25,000 hours, poten-tial power at low ambient temperatures hasbeen traded for more potential power at higherambient temperatures. Again, for an applica-tion where the required power is independentof the ambient temperature, a constant powerrating results in trading off the higher power atlow ambient temperatures for extended con-stant power at higher ambient temperatures.

Performance Deterioration and Recovery Deterioration of performance in GEAeroderivative (LM) industrial gas turbines hasproven to be consistent over various enginelines and applications. Total performance loss isattributable to a combination of “recoverable”(by washing) and “non-recoverable” (recover-able only by component replacement or repair)losses.

Recoverable performance loss is caused by foul-ing of airfoil surfaces by airborne contami-nants. The magnitude of recoverable perform-ance loss is determined by site environment andcharacter of operations. Generally, compressorfouling is the predominant cause of this type ofloss. Periodic washing of the gas turbine, eitherby on-line wash or crank-soak wash procedures,will recover 98% to 100% of these losses. The

severity of the local environment and opera-tional profile of the site determine the frequen-cy of washing.

Studies of representative engines in variousapplications show a predictable, nonrecover-able performance loss over long-term use.Deterioration experience is summarized inFigure 25 for power and heat rate for an LMaeroderivative gas turbine operating on naturalgas fuel.

This figure illustrates long-term, non-recover-able deterioration, not losses recoverable bywashing. Power deterioration at the 25,000-hour operating point is on the order of 4%;heat rate is within 1% of “new and clean” guar-antee. These deterioration patterns are refer-enced to the “new and clean” base rating guar-antee, although actual as-shipped engine per-formance is generally better than the guaranteelevel.

Generally, HPT components are replaced at25,000 hour intervals for reasons of blade lifeand performance restoration. The result ofreplacement of the HPT components is 60% ormore restoration of the non-recoverable per-formance loss, depending on the extent of workaccomplished. Over 80% recovery can beachieved if limited high-pressure compressor



Figure 24. LM2500 constant PT inlet temperatureand constant power operation

Figure 25. LM2500 field trends – power and heatrate deterioration

repairs are performed at the same time.General overhauls at about 50,000-hour inter-vals entail more comprehensive componentrestorations throughout the engine, and mayresult in nearly 100% restoration of the non-recoverable performance.

When using liquid fuel, which is more corrosivethan natural gas, a similar but more rapid pat-tern of deterioration occurs, resulting inapproximately the same 3% to 5% level at thetypical 12,500-hour liquid-fuel HPT repair inter-val.

Maintenance FeaturesIn an operator’s life cycle cost equation, the

most important factors are engine availabilityand maintenance cost. To enhance these con-siderations in regard to its aeroderivativeengines, GE has invested considerable effort indeveloping features to optimize the result ofthis equation. GE’s aeroderivatives’ uniquedesigns allow for maintenance plans with thefollowing features:

■ Borescope inspection capability. Thisfeature allows on-station, internalinspections to determine thecondition of internal components,thereby increasing the intervalbetween scheduled, periodic removalsof engines. When the condition of theinternal components of the affectedmodule has deteriorated to such anextent that continued operation is notpractical, the maintenance programcalls for exchange of that module.

■ Modular design. Using their flightheritage to maximum advantage,aeroderivative engines are designed toallow for on-site, rapid exchange ofmajor modules within the gas turbine.The elapsed time for a typical HPT

and combustion module replacementis 72 hours. This exchange allows thegas turbine to operate for anadditional 25,000 hours.

■ Compactness. The GE AeroDerivativeengines have inherited modestdimensions and lightweightconstruction that generally allows foron-site replacement in less than 48hours.

■ Monitoring and Diagnostics Servicesare made available by establishingdirect phone connections from thecontrol system at the customers' sitesto computers in GE's LM monitoringcenter. These services link theexpertise at the factory with theoperations in the field to improveavailability, reliability, operatingperformance, and maintenanceeffectiveness. Monitoring of keyparameters by factory experts allowsearly diagnosis of equipment problemsand avoidance of expensive secondarydamage. The ability for serviceengineers to view real-time operationsin many cases results in acceleratedtroubleshooting without requiring asite visit (Figure 26).



Figure 26. Monitoring and Diagnostic services: GEengineer remotely monitoring a unit

The integration of all of the features notedabove enables the operator to monitor the con-dition of the engine, maximize uptime, andconduct quick maintenance action. To learn ingreater depth about the maintenance of the GEAeroderivative gas turbines, refer to GER-3694,“Aeroderivative Gas Turbine Operating andMaintenance Considerations.”

Advances in Aircraft EngineTechnologyGE Aircraft Engines invests over $1 billionannually in research and development, much ofwhich is directly applicable to all of GE’saeroderivative gas turbines. In particular, con-sistent and significant improvement has beenmade in design methodologies, advanced mate-rials and high-temperature technologies. Areasof current focus are presented in Figure 27. Asthese technological advances are applied toindustrial uses, GE’s aeroderivative enginesbenefit from continual enhancement to attaingreater power, efficiency, reliability, maintain-ability and reduced operating costs.

In 1993, GE Aircraft Engines began testing thenew, ultra-high thrust, GE90, high bypass fanengine (Figure 28). The thrust level demonstrat-ed at initial certification was 87,400 pounds(376,764 N), and since then, has reached athrust level of 110,000 pounds.

The advanced technologies proven in the GE90engine include wide-chord composite fanblades, short durable 10-stage HPC, compositecompressor blades and nacelles, and a dual-dome annular combustor. These attributes con-tribute to delivering economic advantages oflow fuel consumption, low noise and emissions,reliability of a mature engine, and growth capa-bility to over 100,000 pounds thrust.

In 1995, the GE90 engine entered commercialservice on a Boeing 777 aircraft operated byBritish Airways. One year later, a growth versionof this engine, rated at 90,000 pounds of thrust,was certified and delivered. By 2000, GE90engines had realized a major landmark, havingaccumulated more than one million flighthours since entry into service. After loggingone million flight hours, and fueled by strongmarket interest and customer commitments,the Boeing Company and GE introduced twonew, longer range models, powered by thenewly introduced, growth derivative GE90-115Bengine.

SummaryGE’s continued investment in R&D aircraftengine technology enables the LM series of gasturbines to maintain their leadership positionin technology, performance, operational flexi-bility, and value to the customer. Offered inpower output from 13 to 47 MW, and having the



• Components– Multi-Hole Combustion Liner– Dual Annular Combustors– Aspirating Seals– Counter Rotating Turbines– Fiber Optic Controls– High Temperature Disks– MMC Frames/Struts– Model Based Controls– Composite Wide Chord Fan Blades– Swept Airfoils– Lightweight Containment– High Torque Shafts– Magnetic Bearings

• Metals– High temperature Alloys

• N5. N6, R88DT, MX4– Intermetallic Alloys

• NiAl, TiAl, Orthorhombic Ti– Structural Ti Castings

• Non-metals– Polymeric Composites

• PMR 15 Case• Composite Fan Blade

– High Temperature Polymerics (700oF/371oC)– Thermal Barrier Coatings

• Advanced Materials– Metal Matrix Composites (MMC)– Ceramic Matrix Composites

• Advanced Processes– Dual Alloy Disks– Spray Forming– Laser Shock Peening– Translational friction Weld– Braiding– Resin Transfer Molding– Waterjet Machining– Superplastic Forming/Diffusion Bonding– Robust Material Processes

• Technology Aids– Six Sigma Processes– Remote Monitoring & Diagnostics– Concurrent Engineering/Manufacturing– Design Engineering Workstations– Computational Fluid Dynamics– Process– Modeling– Stereolithography Apparatus– Virtual Reality– Advanced Instrumentation– New Product Introduction Methods

Figure 27. New processes and technologies

Figure 28. GE90 high-bypass fan engine on Boeing 777

ability to operate with a variety of fuels andemission control technologies, GE’s aeroderiva-tive gas turbines have gained the widest accept-ance in the industry, with total operating expe-rience in excess of 41million hours. These tur-bines have been selected for a multitude of

applications, from power generation tomechanical drive, for the exploration, produc-tion and transmission of oil and gas, as well asmarine propulsion systems including transport,ferryboat, and cruise ship installations.



List of FiguresFigure 1. GE aeroderivative product line – generator drive gas turbine performance

Figure 2. GE aeroderivative product line – mechanical drive gas turbine performance

Figure 3. Available GE aeroderivative product line equipment arrangements

Figure 4. Aircraft and aeroderivative engine operating experience as of February 2000

Figure 5. Gas turbine terminology and arrangement



Figure 8. LM2500+ gas turbine


Figure 10. LM6000 concept

Figure 11. LM6000 Sprint™ flow cross-section

Figure 12. LM6000 Sprint™ performance enhancement

Figure 13. LM6000 Sprint™ gas turbine

Figure 14. STIG™ System performance enhancement- generator drive gas turbine performance

Figure 15. Typical STIG™ cycle

Figure 16. STIG™ steam flow capability generator drive gas turbine performance

Figure 17 LM2500 STIG™ steam injection ports

Figure 18. GE aeroderivative gas turbine unabated NOx emissions

Figure 19. Minimum NOx emission guarantee levels - wet and dry emissions control options

Figure 20. DLE combustor

Figure 21. LM2500 maximum power capability

Figure 22. Effect of increased power rating on LM2500 hot-section repair interval

Figure 23. LM2500 constant power rating

Figure 24. LM2500 constant PT inlet temperature and constant power operation

Figure 25. LM2500 field trends - power and heat rate deterioration

Figure 26. Monitoring and Diagnostic Services: GE engineer remotely monitoring a unit.

Figure 27. New processes and technologies

Figure 28. GE90 high-bypass fan engine on Boeing 777



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