GTG Performance

7/30/2019 GTG Performance

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PG6101FA

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GTG Performance ??? Availability

Output

Efficiency



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Why performance

monitoring To maintain high availability Minimize degradation and maintain

operation near design efficiency Diagnose problems and avoid operation in

the region where serious malfunction canoccur

Extend time between inspections and

overhauls Reduce life cycle cost



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Single shaft GT



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GTG PerformanceThe Br ayt on Cycle



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Brayton cycle is characterized by : Pressure ratio

Firing temperature



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The pressure ratio resulting in maximum outputand maximum efficiency change with firingtemperature.

Higher the pressure ratio, the greater thebenefits from increased firing temperature.Increase in firing temperature provide powerincrease at a given pressure ratio, although thereis a sacrifice of efficiency due to the increase incooling air losses required to maintain parts lives.



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In combined-cycle applications pressure ratioincrease have a less pronounced effect onefficiency.

Note : As pressure ratio increases, specific powerdecreases. Increase in firing temperature result

in increased thermal efficiency. The significant differences in the slope of the

two curves indicate that the optimum cycleparameters are not the same for simple andcombined cycles.



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Simple-cycle efficiency is achievedwith high pressure ratios.

Combined-cycle efficiency isobtained with more modest pressureratios and greater firingtemperatures.



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Fact or s A f f ect ing Gas

Tur bine Per f or mance Ai r Temper at ur e

Sit e Elevat ion (Bar omet r ic Pr essur e)

Humidi t y I nlet DP

Exhaust DP

Fuels

Fuel Temper at ur e



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Ai r Temper at ur e and

Sit e Elevat ion GT performance is changed by

anything that affects the density

and/or mass flow of the air intake tothe compressor

ISO conditions

59 F/15 C 14.7 psia/1.013 bar



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Effect of CTIM on output



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Effect of CTIM on heat

rate



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MW 1/CTIM

0.505Average Gain in MW / C

0.4753.5371.057623

0.4833.0621.049424

0.4952.5791.041325

0.5052.0841.033126

0.5161.5791.024927

0.5261.0631.016628

0.5370.5371.008329

0.0001.000030

Gain in MW / CGain in MWCFCTIM



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Effect of Barometric

pressure on output



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Effect of Barometric pressure

on heat Rate



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Humidity Humid air is less dense than dry air

Single-shaft turbines that use

turbine exhaust temperature biasedby the compressor pressure ratio toapproximate firing temperature will

reduce power as a result of increasedambient humidity.



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Effect of RH on output



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Effect of RH on Heat rate



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I nlet and Exhaust

Losses

Inserting air filtration, silencing, evaporative coolers or chillersinto the inlet or heat recovery devices in the exhaust causespressure losses in the system

4 Inches (10 mbar) H2O Inlet Drop Produces: 1.42% Power Output Loss 0.45% Heat Rate Increase 1.9 F (1.1 C) Exhaust Temperature Increase

4 Inches (10 mbar) H2O Exhaust Drop Produces: 0.42% Power Output Loss

0.42% Heat Rate Increase 1.9 F (1.1 C) Exhaust Temperature Increase



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Effect of Inlet DP on

output



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Effect of Inlet DP on heat

rate



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Effect of back pressure on

output



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Effect of back pressure on

heat Rate



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Effect of frequency on

output



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Effect of frequency on

heat rate



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MW Frequency

0.074-3.2380.952548.5

-1.805-3.3120.951549.0

-1.507-1.5070.977349.5

0.0000.0001.000050.0

1.2291.2291.019350.5

1.0272.2561.036051.0

Change in MW / 0.5 HzChange in MWCFFrequency



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Fuel temp Heated fuel results in higher turbine

efficiency due to the reduced fuel

flow required to raise the total gastemperature to firing temperature



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Effect of Fuel temp on

output



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Effect of Fuel temp on heat

rate



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Effect of Fuel LHV on

output



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Effect of Fuel LHV on heat

Rate



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Compressor performance



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Gas t ur bine per f or mance

degr adat ion Recover able loss

Recoverable loss is usually associated with compressor fouling and canbe partially recovered by water washing or, more thoroughly, bymechanically cleaning the compressor blades and vanes after openingthe unit.

N on- r ecover able loss Non-recoverable loss is primarily due to increased turbine and

compressor clearances and changes in surface finish and airfoilcontour.

Since this loss is caused by reduction in component efficiencies, itcannot be recovered by operational procedures, external maintenanceor compressor cleaning, but only through replacement of affected

parts at recommended inspection intervals.



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Design specification for

GTG

11665.56Kcal/SM3Fuel LHV

82.4CFuel Temp

0.85RatioGenerator Power Factor

11.18In H2OExhaust DP

89mm H2OInlet DP

1012.49m BarAtmospheric Pressure

70%Relative Humidity

5231RPMTurbine Speed

30CCompressor Inlet Temperature

50HzFrequency

RatedUnitsParameters



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Performance monitoring Heat rate

Specific fuel consumption

Efficiency Compressor efficiency



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Performance calculationHeat rate =

Fuel consumption (SM3) * Calorific value of fuel (Kcal/SM3)Units produced (KWH)



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Performance calculationSpecific fuel consumption =

Fuel consumed per unit of electricity produced

Natural gas consumed (SM3)

Units generated (KWH)



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Performance calculationTurbine efficiency

MW Output (Kcal) * 100

Fuel Input (Kcal)

860 * 100

Heat rate (Kcal/kwh)



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Performance calculation

Compressor Efficiency

P2

P1

(-1)

-1

T2T1

-1

Cp/Cv



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Inspection Gas turbine must be inspected in

following areas

Inlet air filter & Evaporative coolers Compressor

Combustor

Turbine



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Inlet air filter inspection Time to replace filters

Filter plugging

Inlet duct air leak



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Compressor Consumes around 50-65% of the energy

produced by turbine thus fouling of the

compressor can drastically reduce overallefficiency of the gas turbine.

Fouling of the compressor can cause surgewhich not only creates performance

degradation but also creates bearingproblems and flameouts



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Compressor Parameters to be monitored

Efficiency

Surge map Compressor power consumption

Compressor fouling index

Compressor deterioration index

Humidity effect on fouling Stage deterioration



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Compressor performance

calculations Compressor work or power consumed

Wc = CpavgT1{(P2/P1)((y-1)/y)-1}



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Compressor losses

Losses can be divided in to two categories Controllable losses Loss due to compressor fouling

Loss due to inlet pressure drop

Loss due to inlet temperature increase

Uncontrollable losses Loss due to barometric press drop

Loss due to high ambient temperature

Loss due to high ambient humidity

Loss due to frequency drop

Loss due to ageing



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Compressor fouling graph



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G T C o m p r e s s o r e f f i c i e n c y t re n d

9 0 .0

9 0 .5

9 1 .0

9 1 .5

9 2 .0

9 2 .5

9 3 .0

9 3 .5

1

/0

1

/5

1

/1

0

1

/1

5

1

/2

0

1

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1

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0

2

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2

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/1

4

D a t e

C

o

m

p

resso

rE

fficien

cy

Off line water wash

On line water wash



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Compressor wash Online compressor wash

some plants do it daily and some do it whenpressure ratio drops by 2%

Offline compressor wash Pressure ratio drop by 8% beyond which surge

can occur Once in three months as per GE performance

degradation guarantee contract Not meeting our export targets



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Combustor Following parameters to be

monitored

Combustor efficiency Specific fuel consumption



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Turbine Following parameters to be

monitored

Turbine inlet temperature



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GTG Performance

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