Estimating gas turbine performance

Estimating Gas Turbine Performance

Reference GTS–111D page 1


The following is a method for estimating gas turbine performance usingperformance curves and site data (i.e., elevation, ambient temperature, inlet andexhaust pressure drops, and the type of fuel). Both full load and part loadperformance calculations are described and illustrated. Typical examples areprovided for package power plants.

Performance curves are based on the ISO standard (59°F, 60% relative humidityand 14.7 psia). Theses curves do not include the water or steam injection for NOxcontrol due to the many different NOx levels offered. However, the effect of aknown water or steam flow can be calculated separately per the dilutent effectscurves.

This procedure should be used only for the approximation of performance at siteconditions and not for performance guarantees. Performance guarantees for thisproposal are shown in the “Performance Specifications” section. Theperformance curves included are to illustrate the calculationprocedure and do not reflect current ratings. Performance curvesapplicable to the equipment offered in this proposal are listed under “Turbine andGenerator Performance Curves” in the “Engineering Data” Section.

Nomenclature

D = differential; i.e. DP is pressure drop

fa = inlet DP factor for output

fb = exhaust DP factor for output

fc = compressor inlet temperature factor for output

fd = compressor inlet temperature factor for exhaust flow

fe = compressor inlet temperature factor for heat rate

ff = inlet DP factor for heat rate

fg = exhaust DP factor for heat rate

fh = humidity factor for output

fi = humidity factor for heat rate

HC = heat consumption (fuel consumption in Btu/h)

HR = heat rate (Btu/kWh)

KW = power output (kW)

P = barometric pressure (psia)

Pc = effective pressure (psia) at the inlet flange of a package power plant

Tx = exhaust gas temperature (°F)

g



Wx = exhaust flow (lb/h)

EFF = thermal efficiency (%)

(LHV) = based on fuel lower heating value

Subscripts s, i, o

s denotes at site conditions

i denotes at ISO conditions

o denotes at site altitude, actual inlet and exhaust DP’s, and compressorinlet conditions of 59°F @ 60% RH.

I. Full Load Performance

A. Method

1. Output (KWs) = (KWi) x (Ps/14.7) x fa x fb x fc x fh

2. Heat Rate (HRs) = (HRi) x fe x ff x fg x fi

Note: Altitude has no effect on heat rate

3. Heat Consumption (HCs) = (KWs) x (HRs)

4. Exhaust Temperature (Tx) Read from appropriate curve. Addtemperature increase for additional inlet and/or exhaust pressuredrops.

5 Exhaust Flow (Wxs) = (Wxi) x (Pc/14.7) x fd

Where Pc = Ps – (0.0361 x additional DP (inches of H2O) at inlet)

B. Notes

1. Round off calculations as follows:

Output – To nearest 10 kW or maximum of 4 significant figuresHeat Rate – To nearest 10 Btu/kWh

Heat Consumption – To nearest 0.1 x 106 Btu/h or maximum of 4significant figures

Exhaust Temperature – To nearest degree F Exhaust Flow – To four significant figures (lb/h)

2. The ratio Ps/14.7 can be read directly from the altitude correctioncurve 416HA662

C. Sample Full Load Calculation

Package Power Plant – MS7001(EA) Simple Cycle Model PG7111(EA)with an air–cooled generator.



Site Conditions:

Altitude = 600 ft

Barometric Pressure Ps = 14.39 psia (from Curve 416HA662)

Compressor Inlet Temperature = 90°F

Inlet DP = 2.5’ H2O (included in rating)

Exhaust DP = 10” H2O (5.5” H2O is includedin rating)

Fuel = Distillate Oi1

Mode = Base Load

1. Design Conditions (ISO) from Curve 499HA733

Output KWi = 82100 kW

Heat Rate HRi = 10560 Btu/kWh (LHV)

Exhaust Flow Wxi = 2358 x 103 lb/h

2. Calculation of factors.

The ratings for the package power plant include a standard inlet and exhaustpressure drop as stated with the ratings. Therefore the pressure drops usedto calculate fa, fb, ff, fg, Pc, and exhaust temperature increase are the pressuredrops in excess of the standard pressure drops.

The resulting performance decrease effect of additional pressure drop issubtracted from unity to obtain the output multiplication factor. The heat ratepercentage effect is added to unity to obtain the heat rate multiplier foradditional pressure drops.

fb � 1.0 ��0.424

x 4.5� 1100

� 0.9953

fc � 0.890 (from Curve 499HA734)

fa � 1.0

fe � 1.025 (from Curve 499HA734)ff � 1.0fg � 1.0 ��0.42

4x 4.5� 1

100� 1.0047

Output :

Heat Rate :

(curve 499HA733 with additional 4.5” H2O)

(curve 499HA733 with additional 4.5” H2O)

fh � 0.9982 (from Curve 498HA697)

fi � 1.0048 (from Curve 498HA697)



Pc � 14.39 psia � 0 � 14.39 psiafd � 0.930 (from Curve 499HA734)

Exhaust Flow :

3. Calculation of Full Load Conditions at Site:

Output KWs � 82100 x 14.3914.7

x 1.0 x 0.9953 x 0.890 x 0.9982

� 71063 or 71060kW

Heat Rate HRs � 10560 x 1.025 x 1.0 x 1.0047 x 1.0048

� 10927 or 10930 Btu�kWh (LHV)

Heat Consumption HCs � 71060 x 10930

� 776.7 x 106 Btu�h (LHV)

Exhaust temperature is calculated by adding the temperature increasedue to pressure drops to the value read from Curve 499HA734:

Tx � 1006 � 1.94

(0 � 4.5) F

Tx � 1008.1 or 1008 F

Exhaust Flow � 2358 x 103 x 14.3914.7

x .930

� 2146.7 x 103 or 2147 x 103 Ib�h

II. Part Load Performance

Part load output, heat rate and heat consumption are calculated in a similarmanner as base load using the part load heat consumption curve. Before using theoutput % off the heat consumption curve, all part load performance must bereferenced to 59°F site performance kWo.

A. Method

1. At site barometric pressure with site inlet and exhaust pressure dropsand at 59°F compressor inlet temperature, calculate the followingbase load performance parameters:

Output, kWo

Heat rate, HRo

Heat consumption, HCo

This data then becomes the corrected values on which to base the partload calculations.

2. Calculate percentage of load:



% load = required load/kWo

3. From the applicable performance curve, at the percent of loadcalculated from (2) above and at the compressor inlet temperature,read the percent of design heat consumption.

HCs = HCo x % design heat consumption.

4. Heat rate at required load:

HRs = HCs ÷ kWs

5. Exhaust flow and temperature are calculated in an analogous manneras base load using corrected design outputs as shown above, and theEffects of Modulated Inlet Guide Vanes Curve at the appropriateambient. The extreme right hand point of each ambient curve on theModulated Inlet Guide Vane Curve represents the full open IGVposition, the knee point in each curve represents the closed IGVposition, Note that this curve is for combined cycle machines only.Simple cycle machines, which are not normally concerned with partload Exhaust conditions, operated on a different schedule and can notbe calculated using this curve.

B. Sample Part Load Calculation

The following sample part load calculations are for the MS7001(EA) simplecycle package power plant used previously.

Site conditions:

Altitude = 600 ftBarometric pressure = 14.39 psiaCompressor inlet temperature = 90°FRelative Humidity = 60%RHInlet DP = 2.5” H2O (included in

rating)Exhaust DP = 10” H2O (5.5” H2O is

included in rating)Fuel = Distillate OilLoad required = 75 percent base load

1. Calculation of site performance at full load and 59°F at 60%RH:

KWo = KWi x (14.39/14.7) x fa x fb

KWo = 821000 x 0.9789 x 1.0 x 0.9953 = 79990 kW

HRo = HRi x ff x fg

HRo = 10560 x 1.0 x 1.0047 = 10610 Btu/kWh (LHV)

HCo = KWo x HRo



HCo = 79990 x 10610 = 848.7 x 106 Btu/h (LHV)

2. Calculation of site performance for 90°F @ 60%RH:

Site output (base load) = KWo x fc x fh = 79990 x 0.891 x 0.9983 = 71150 kW

At 75% base load, required load = 71150 x 0.75 = 53360 kW

% load = 53360/79990 = 66.7%

3. From Curve 499HA733 at 66.7% design load and 90°F, % design heatconsumption = 71%

Part load, site heat consumption, HCs = HCo x % design heat rate

HCs = 848.7 x .71 = 602.6 x 106 Btu/h (LHV)

4. Site heat rate HRs = HCs ÷ kWs

HRs = 602.6 x 106 ÷ 53360 = 11290 x Btu/kWh (LHV)

5. Entering the Modulated Inlet Guide Vane Effects Curve (516HA129)at the 66.7% output calculated in Step 2 and, for the 90°F ambientcurve;

Exh Temp. = 990°FWexh % design = 75.5%

Wexh = Wi x % designWexh = 2358 x .755 = 1780 x 103 lb/h

Performance With Water or Steam Injection

The amount of steam or water injection required to meet a given NOx emissionlevel is not available from a curve because of the many variables impacting thisvalue. In fact, the exact flow is typically not finalized until the field EmissionsCompliance Testing. However, given a specific flow value, the resulting effect onoutput and Heat Rate can be determined using the Injection Effects Curves.

For example, taking the “dry” Output and Heat Rate Performance calculatedfrom Example I and, assuming GE has reported (for the specific conditons given)an estimated steam flow to meet 65 ppmvd @ 15% O2 NOx of 42590 lb/h (11.83pps); The resulting output and Heat Rate would be:



KW = 71060 x (1 + 0.059) (from curve 499HA899A) = 75250 KW

HR = 10930 x (1 – .0275) (from curve 499HA900A) = 10630 Btu/Kw–h (LHV)



SI and Metric Units Conversion

The following is a list of conversion factors mostcommonly used for gas turbine performance calculations.

Conversion FactorsTo Convert To Multiply Byatm kg/cm2 1.0333

atm lb/in2 14.7

bars atm 0.9869

bars lb/in2 14.5

Btu/h kcal/h 0.2520

Btu/h kJ/h 1.0548

Btu/hph kJ/kWh 1.4148

Btu/lb kJ/kg 2.326

°F °R °F + 459.7

°C °F (°C x 9/5) + 32

°C °K °C + 273.2

ft3/min l/s 0.4720

ft3/min m3/min 0.02832

gal/mln l/s 0.06308

in. of mercury kg/cm2 0.03453in. of water

(at 4°C) kg/cm2 0.00254in. of water

(at 4°C) lb/in2 0.03613

J Btu 9.478 x 10–4

kg lb 2.205

kg/cm2 lb/in2 14.22

kg/m3 lb/ft3 0.06243

kW hp 1.341

lb/in2 Pa 6894.8

l/min ft3/s 5.886 x 10–4

l/min gal/s 0.004403

scf Nm3 0.0268

W Btu/h 3.4129



0 10 20 30 40 50 60 70 80 90 100 110 120 130 GENERATOR OUTPUT – PERCENT DESIGN

10

20

30

40

50

60

70

80

90

100

110

120

130

120 F

59 F

0 F

499HA733REV A

DATE: 10/17/89DA JAQUEWAY

GENERAL ELECTRIC MODEL PG7111(EA) GAS TURBINEESTIMATED PERFORMANCE – CONFIGURATION: NATURAL GAS & DISTILLATE

Compressor Inlet Conditions 59 F (15.0 C), 60% Rel. HumidityAtmospheric Pressure 14.7 psia (1.013 bar)

NOTES: 1. Altitude correction on curve 416HA662 REV A 2. Ambient temperature correction on curve 499HA734 REV A 3. Effect of modulated IGV’s on exhaust flow and temp. on curve 516HA129 4. Air cooled generator 7A6 5. Humidity correction on curve 498HA697 REV B – all performance calculated with specific humidity of .0064 or less so as not to exceed 100% relative humidity. 6. Plant performance is measured at the generator terminals and includes allowances for excitation power, shaft driven auxiliaries, and 2.5 in. H2O (6.2 mbar) inlet and 5.5 in. H2O (13.7 mbar) exhaust pressure drops. 7. Additional pressure drop effects:

%Effect on Effect on Output Heat Rate Exhaust Temp. 4 in. H2O (10.0 mbar) inlet –1.42 0.45 1.9 F (1.1 C) 4 in. H2O (10.0 mbar) exhaust –0.42 0.42 1.9 F (1.1 C)

kW Btu (kJ)/kWh Btu (kJ)/h lb/h (kg)/h

NATURAL GAS 83500 10480 (11060)

875.1 (923.5) 2351 (1066)

DISTILLATE 82100 10560 (11140)

867.0 (914.6) 2358 (1070)

PPB 061088

HE

AT

CO

NS

UM

PT

ION

– P

ER

CE

NT

DE

SIG

N

FUEL DESIGN OUTPUTDESIGN HEAT RATE (LHV)DESIGN HEAT CONS (LHV) X10–6DESIGN EXHAUST FLOW X10–3MODE: BASE LOAD



0 10 20 30 40 50 60 70 80 90 100 110 120

COMPRESSOR INLET TEMPERATURE (DEG. F)

70

75

80

85

90

95

100

105

110

115

120

125

130

HEAT RATE

OUTPUT

EXHAUST FLOW

HEAT CONS.

499HA734REV A

DATE 10/17/89DA JAQUEWAY

940950960970

980990

10001010102010301040

GENERAL ELECTRIC MODEL PG7111(EA) GAS TURBINEEffect of Compressor Inlet Temperature on

Output, Heat Rate, Heat Consumption, Exhaust FlowAnd Exhaust Temperature at 100% Speed

FUEL: NATURAL GAS & DISTILLATE OILDESIGN VALUES ON CURVE 499HA733 REV ADESIGN MODE: BASE LOAD

EX

HA

US

T T

EM

PE

RA

TU

RE

(D

EG

. F)

PE

RC

EN

T D

ES

IGN



0 10 20 30 40 50 60 70 80 90 100 110 120 130GENERATOR OUTPUT – PERCENT

65

70

75

80

85

90

95

100

105

110

115

0 F

59 F

90 F

120 F

516HA129DATE 10/17/89DA JAQUEWAY

30 F

500550600

650700

750800850

900950

100010501100

0 F

59 F

90 F

120 F

GENERAL ELECTRIC MODEL PG7111(EA) GAS TURBINE

Effect of Modulated Inlet Guide Vanes on Exhaust Flow and TemperatureAs a Function of Output and Compressor Inlet Temperature.

FUEL: NATURAL GAS & DISTILLATE OILDESIGN VALUES ON CURVE 499HA733 REV A

30 F

EX

HA

US

T T

EM

PE

RA

TU

RE

(D

EG

. F)

EX

HA

US

T F

LOW

– P

ER

CE

NT

DE

SIG

N

DESIGN MODE: BASE LOAD



0 1 2 3 4 5 6 7 8 9

ALTITUDE – THOUSAND FEET

10.5

11

11.5

12

12.5

13

13.5

14

14.5

15

15.5

4/24/90F.J. BROOKS

416HA662REV A

GENERAL ELECTRIC GAS TURBINEALTITUDE CORRECTION FACTOR

ALTITUDE VS ATMOSPHERIC PRESSURE

ANDALTITUDE VS CORRECTION FACTOR

FOR GAS TURBINE OUTPUT AND FUEL CONSUMPTION

NOTES:1. Heat Rate and Thermal Efficiency are not affected by altitude.2. Correction Factor = P(atm)/14.7

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

ATMOSPHERIC PRESSURE

CORRECTION FACTOR



0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035SPECIFIC HUMIDITY (lb. water vapor/lb. dry air)

0.994

0.995

0.996

0.997

0.998

0.999

1

1.001

1.002

1.003

1.004

1.005

1.006

1.007

1.008

1.009

1.01

10/10/89DA JAQUEWAY

498HA697REV B

GENERAL ELECTRIC MS6001, MS7001 AND MS9001 GAS TURBINESCORRECTIONS TO OUTPUT AND HEAT RATE

FOR NON–ISO SPECIFIC HUMIDITY CONDITIONSFor operation at base load on exhaust

temperature control curve

POWER OUTPUT

HEAT RATE

ISO SPECIFIC HUMIDITY0.0064 lb. water vapor/lb. dry air

CO

RR

EC

TIO

N F

AC

TO

R



0 2 4 6 8 10 12 14 16 18 20

STEAM INJECTION – LB/S

0

1

2

3

4

5

6

7

8

9

10

11

12

GE MODEL PG7001(EA) GAS TURBINEEFFECT OF STEAM INJECTION ON OUTPUTBASE LOAD – NATURAL GAS / DISTILLATE

100F

59F

45F

0F

PE

RC

EN

T IN

CR

EA

SE

IN O

UT

PU

T

CURVE 499HA899AKH CONWAY 4/14/89



100F

59F

0F

0 2 4 6 8 10 12 14 16 18 20

STEAM INJECTION – LB/S

0.

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

GE MODEL PG7001(EA) GAS TURBINEEFFECT OF STEAM INJECTION ON HEAT RATE

BASE LOAD – NATURAL GAS / DISTILLATE

PE

RC

EN

T D

EC

RE

AS

E IN

HE

AT

RA

TE

45F

CURVE 499HA900AKH CONWAY 4/14/89

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Estimating gas turbine performance