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Bolland

Kap 9: Gas Power SystemsGassturbin

Olav Bolland

TEP4115/4120 Termodynamikk

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Bolland

Power production in Norway

• National grid: 99.5% hydropower– 27000 MW - 120 TWh/a– Per capita: 6 kW - 27000 kWh/a

• Offshore oil/gas: mechanical power and local grids– 3000 MW gas turbine power - 10 TWh/a

• Future:– Wind power: 2002-2010 +3 TWh/a (2010: 0.9 TWh!!)– More hydropower: potential YES – acceptance NO– Natural gas power: potential YES

problem is CO2

– CO2 is a hot issue!!– Dependence on import of coal & nuclear power?

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Bolland

Gas Turbines

Assumptions for the basic gas turbine cycle:• Air, as an ideal gas, is the working fluid throughout• Combustion is replaced with heat transfer from an external source

Fig. 9.8, page 389

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Bolland

Gas Turbine Applications• Aero Engines (jet, turbofan, turboprop)• Gas Pipelines (compressor driver)• Power plants (generator driver)• Combined Heat and Power (generator, utilisation of exhaust heat)• Ship Propulsion• Oil/Gas-Platforms (generator & compressor driver)• Others (emergency backup, desalination)

• 2000: Production value of aero engines larger than for gas turbines for power generation and mechanical drive

• 2001 : Production value of gas turbines for power generation and mechanical drive larger than for aero engines

Annual production value of gas turbines/aero engines: 50 bill. US$

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General Electric LM5000Laget med utgangspunkt i flymotor

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Bolland

Cutaway diagram of a Westinghouse 501D5A gas turbine

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Bolland

Siemens V94.2ca. 150 MW,

første gassturbin med lav-NOXNOX = (NO/NO2) = nitrogenoksider

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Turbin i gassturbin4-trinns, Siemens

1. trinns løpeskovler

1. trinns ledeskovler

Ringbrennkammer(brennerne kan ikkesees, bak til høyre)

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Bolland

Work closed/open systems

2 1

2

1

2 2 2

1 1 1

2

2 1 2 11

2

1

First law for a closed system:

Relating heat to entropy:

Q W U U

Q T dS

T dS dU PdV

Q T dS dU pdV

U U pdV W U U

W pdV

1 2

2 2 2

1 1 1

2 2

1 1

2 2

1 1

First law for an open system (steady-state):

0

Relating heat to entropy:

and and

dUQ W mh mh

dt

Q T dS dU pdV

T dS dU PdV T dS dH Vdp

H U pV dU dH pdV Vdp

Q dH V dp

Q m dh V dp

2

2 1 1 21

2

1

( ) ( ) 0m h h V dp W m h h

W V dp

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Bolland

The Brayton CycleCycle Analysis:

12

1 2

Wh h

m

233 2

Qh h

m

411 4

Qh h

m

34

3 4

Wh h

m

Fig. 9.9, page 389

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Bolland

Ideal Brayton Cycle

Using Constant Specific Heats, the cycle thermal efficiency is:

1

2

1

11 k

kpp

Fig. 9.10, page 391

Fig. 9.11, page 394

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Ideal Brayton Cycle, different pressure ratios

Fig. 9.12, page 395

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Bolland

Irreversibilities in a gas turbine cycle

Fig. 9.13, page 397

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Bolland

Regenerative/recuperative Gas Turbines

2

4 2

xreg

h h

h h

Fig. 9.14, page 400

Største gassturbin med rekuperatorer Rolls Royce WR21 (20 MW, in UK Type 45 destroyer)Rekuperator benyttes typisk på små GT, 100-500 kW.

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Bolland

Reheat and Intercooling

Fig. 9.16, page 404

Reheat, regeneration, and intercooling are most effective when used in combination with one another. However, weight limitations (e.g. aircraft applications) often limit their usage.

Fig. 9.18, page 407

Alstom GT26/GT24 (277/191 MW, 3000/3600 rpm)er de eneste gassturbiner som benytter reheat.Alstom bruker begrepet ”sequential combustion”.

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Aircraft Applications

Turbo Jet Applications, with and without afterburner

Fig. 9.20, page 414

Fig. 9.21, page 415

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Bolland

Turbo jet – with afterburner

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Aircraft Applications

a) Turboprop, b) Turbofan, and c) Ramjet applications

< 600 km/t

< 1000 km/t

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Bolland

Turbofan

GE90B777-300ER

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RakettmotorRomferge; i brun tank: oksygen hydrogen

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Compressible Flows: The Basics

2 1F V Vm

1-D Steady Flow Momentum Equation:

Velocity of Sound, isentropic wave, ideal gas: c kRT

Mach Number:V

Mc

Stagnation Enthalpy:

2

0 2

Vh h

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Fig. 9.23, page 419

Combined Cycle

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Hvorfor har en kombinert prosesshøy virkningsgrad ?

CARNOTl

h

T

T 1

Carnotvirkningsgrad; en kvalitativ beskrivelse av virkningsgrad for en kraftprosessTl er temperatur for varmeavgivelse fra prosessenTh er temperatur for varmetilførsel for prosessen

T

s

Th

Tl

Th h

s sh

3 2

3 2lav -

1

2

3

4

Th h

s sl

4 1

4 1lav

Dampturbin prosess

T

s

Th

Tl

Th h

s sh

3 2

3 2høy

1

2

3

4

Th h

s sl

4 1

4 1lav

Kombinert prosess

T

s

Th

Tl

Th h

s sh

3 2

3 2høy

1

2

3

4

Th h

s sl

4 1

4 1høy

Gassturbin prosess

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Utvikling av virkningsgrad for gassturbin-anlegg

1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 200620

25

30

35

40

45

50

55

60

65

70

Vir

knin

gsgr

ad [

%]

Kombinerte gassturbin-/dampturbinanleggFlyderiverte" gassturbinerStore industri-gassturbiner

Kombinerte gassturbin-/dampturbinanlegg

"Flyderiverte" gassturbiner

Store industri-gassturbiner

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Bolland

Varmegjenvinning fra en eksosgass ved dampproduksjon

0

100

200

300

400

500

600

700

0 50 100 150 200 250 300 350

Overført varme [MW]Heat transfer

Tem

per

atu

r [C

]T

emp

erat

ure Eksos/

Exhaust

Vann/DampWater/steam

Eksosgasskurve,stigningstall 1/(m*cp)

Overheter,stigningstall 1/(m*cp)

fordamper,fordamping ved konstant temperatur

pinch,minste dT i kjel,begrensende fordampproduksjon

economiser,stigningstall 1/(m*cp)

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Components of a Vapor Power PlantSteam Power Plant

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Rankine Cycle

Turbine:

1 2tW

h hm

Condenser (1 side):

2 3outQ

h hm

Boiler:

1 4inQ

h hm

Pump:

4 3pW

h hm

Overall Performance:

1 2 4 3

1 4

/ /

/

t p

in

W m W m h h h h

h hQ m

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Combined Cycle Power Plant

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Gasskraftverk Kårstø - 420 MW

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Combined Cycle Power Plant

%5.48100

5.48

%5.89100

415.48

E

PE

QP

%57100

57

E

P

Power Production only Heat & Power Production

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Bolland

Fuel characteristics for CO2-emission

Fossil fuels consists of the combustible componentsCarbon (C) and Hydrogen (H)

M ethane: C H1 4

The ratio between carbon and hydrogen gives the amount of CO2

C H O CO H O2 2 2m n

coal oil natural gas

coal oil natural gas

mn

mn

m

n

m

n

m

n

4 2

11 0 5 0 25. . .

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Bolland

Emission of CO2 from fossil fuels

30 35 40 45 50 55 60 65 70 75 80 85 90 95 100Eff iciency [%]

0100200300400500600700800900

1000110012001300

Em

issi

on o

f gr

am C

O2 p

er k

Wh e Methane (H/C=4)

Distillate oil (H/C=2)Lignite (brown coal)Bituminous coalAnthrasit

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”CO2-fri” gasskraft?Mest kjente teknologiprinsipper

Navn/begreper for de tre metodene:1: Post-combustion2: Pre-combustion3: Oxy-combustion (eller oxy-fuel)

CO₂separation

CO₂ compression & conditioning

N₂/O₂

CO₂

ShiftH₂

CO₂

Powerplant

Air

O₂N₂

CO₂

N₂/O₂CO₂ compression

& conditioning

Powerplant

Gasification

Reforming

CO₂separation

H₂

CO₂

CO/H₂

Air separation

CO/H₂

Coa

l, O

il, N

atur

al G

as,

Bio

mas

s Powerplant

Post-combustion

Pre-combustion

Oxy-combustion