Gas Turbine Combustion and Power Generation€¦ · Gas Turbine Combustion and Power Generation Dr. A. Kushari Department of Aerospace Engineering IIT, Kanpur PROPULSION LAB, DEPARTMENT

Gas Turbine Combustion

and Power Generation

Dr. A. Kushari

Department of Aerospace Engineering

IIT, Kanpur

PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.

Outline

• Introduction

• Advantages and Disadvantages

• Future Requirements

• Gas Turbine Combustors

• Ongoing Research

• Conclusions

• Acknowledgement

IIT, Kanpur


TURBINES: Machines to extract fluid

power from flowing fluids

Steam

Turbine

Water

Turbines

Gas

Turbines

Wind

Turbines

Aircraft Engines

Power Generation

•High Pressure, High Temperature gas

•Generated inside the engine

•Expands through a specially designed TURBINE

IIT, Kanpur


GAS TURBINES

• Invented in 1930 by Frank Whittle

• Patented in 1934

• First used for aircraft propulsion in 1942 on Me262 by

Germans during second world war

• Currently most of the aircrafts and ships use GT engines

• Used for power generation

• Manufacturers: General Electric, Pratt &Whitney,

SNECMA, Rolls Royce, Honeywell, Siemens –

Westinghouse, Alstom

• Indian take: Kaveri Engine by GTRE (DRDO)

IIT, Kanpur


PRINCIPLE OF OPERATION

• Intake – Slow down incoming air

– Remove distortions

• Compressor – Dynamically Compress air

• Combustor – Heat addition through

chemical reaction

• Turbine – Run the compressor

• Nozzle/ Free Turbine – Generation of thrust

power/shaft power

IIT, Kanpur


Advantages and Disadvantages

• Great power-to-

weight ratio

compared to

reciprocating engines.

• Smaller than their

reciprocating

counterparts of the

same power.

• Lower emission

levels

• Expensive:

– high speeds and high operating

temperatures

– designing and manufacturing

gas turbines is a tough problem

from both the engineering and

materials standpoint

• Tend to use more fuel when

they are idling

• They prefer a constant rather

than a fluctuating load.

That makes gas turbines great for things like transcontinental jet aircraft and

power plants, but explains why we don't have one under the hood of our car.

IIT, Kanpur


Emission in Gas Turbines

•Lower emission compared to all conventional methods (except nuclear)

•Regulations require further reduction in emission levels

IIT, Kanpur


Needs for Future Gas Turbines

• Power Generation – Fuel Economy

– Low Emissions

– Alternative fuels

• Military Aircrafts – High Thrust

– Low Weight

• Commercial Aircrafts – Low emissions

– High Thrust

– Low Weight

– Fuel Economy

Half the size and twice the thrust

Double the size of the Aircraft and double the distance traveled with 50% NOx

IIT, Kanpur


Gas Turbine Combustion

F/A – 0.01

Combustion efficiency : 98%

IIT, Kanpur


Ongoing Research

• Effect of inlet disturbances

• Combustion in recirculating flows

• Spray Combustion

IIT, Kanpur


Effect of Inlet Disturbance

Tunable inlet to create weak disturbance of

varying frequency

Bluff body stabilized flame

Unsteady pressure and heat release

measurement

IIT, Kanpur


Pressure Amplitude variation

= 0.2211 L = 20 cm

•Pressure oscillations increases

with decreasing length

•Dominant frequency 27 Hz

•Acoustic frequency 827 Hz

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Pressure and Heat Release

80

130

180

230

280

330

10 15 20 25 30

Length of Inlet (cm)

Prm

s (

pascal)

60

70

80

90

100

110

120

130

140

150

160

Ph

ase a

ng

le (

deg

ree)

Prms Phase angle

Less damping with increasing

length

Causes the rise is pressure

fluctuations

IIT, Kanpur


0

5

10

15

20

25

30

35

40

45

10 15 20 25 30

Length of Inlet (cm)

freq

uen

cy (

Hz)

110

112

114

116

118

120

122

124

SP

L (

Db

)

Frequency Amplitude

3.0 /am g s , = 0.3455

Low Frequency Variation with Inlet

Length

IIT, Kanpur


Variation of Dominant Frequency with Inlet Velocity

10

15

20

25

30

35

40

45

0.8 1 1.2 1.4 1.6 1.8 2

Mean Inlet Velocity (m/s)

Fre

quency (

Hz)

Measured

Calulated (St = 0.171)

*sf DSt

U

St = 0.171 (60 deg cone)

0.171*

0.02s

Uf

Dominant Frequency governed by vortex

dynamics

Feed back locking of flow instability and

combustion process

Phase relationship leads to

enhancement of combustion oscillations

IIT, Kanpur


Ongoing Research




IIT, Kanpur


Recirculating Flow Dynamics

• Primary zone

• Fuel air mixing

• Intense combustion

• Short combustion length

• High turbulence

• Fuel rich combustion

Understanding recirculating flow dynamics

Time scales

Pressure transients

Energy cascading

Combustion in recirculating flows

Droplet Flow interaction

IIT, Kanpur


Image Processing

Filtered out image from the noises Grayscale image

Intensity image Simulation results

IIT, Kanpur


Vortex Dynamics

0.35

0.4

0.45

0.5

0.55

0.6

2.33 3.33 4.33 5.33 6.33

Non-dimensional time

No

n-d

ime

nti

on

al

dis

tan

ce

(L2

/L)

of

se

co

nd

vo

rte

x t

o t

he

inle

t o

f th

e c

om

bu

sto

r

0

0.002

0.004

0.006

0.008

0.01

2.33 3.33 4.33 5.33 6.33

Non-dimensional time

Rati

o o

f th

e s

eco

nd

vo

rte

x a

era t

o t

he

tota

l area o

f th

e c

old

flo

wfi

eld

IIT, Kanpur


Transient Analysis

•Identification of signatures of re-circulation, turbulence and acoustics

through frequency domain analysis of pressure transients

•Turbulence energy cascading due to re-circulation

IIT, Kanpur


Combustion in Recirculating Flow

0

0.2

0.4

0.6

0 8 16 24 32 40 48 56Non-dimensional time

No

n -

dim

en

sio

na

l

fla

me

are

a

200

250

300

350

400

450

0 0.2 0.4 0.6 0.8 1 Non-dimensional distance along the combustor diameter

Te

mp

era

ture

in

de

gre

e

ce

nti

gra

te

Time scale reduces, complete combustion, Good pattern factor

IIT, Kanpur


Ongoing Research




–Needs and Challenges

–Controlled atomization

–Emissions in spray combustion

IIT, Kanpur


Spray Combustion: Issues

• Non-symmetrical spray flames and hot

streaks

– Serious damage to combustor liner

– Combustor exit temperature (pattern factor)

• Flame location, shape and pattern

• Emission Levels

IIT, Kanpur


Need for controlled atomization

– Big Drops => Longer Evaporation Time => Incomplete

Combustion => Unburned Hydrocarbons & Soot,

Reduced Efficiency

– Small Drops => Faster Evaporation and Mixing =>

Elongated Combustion Zone => More NOx

– Uniform size distribution for favorable pattern factor

• Reduced thermal loading on liner and turbine

– Reduced feedline coupling

IIT, Kanpur


Ongoing Research







IIT, Kanpur


Internally Mixed Swirl Atomizer

Good atomization with small pressure drop

Both hollow-cone and solid cone spray from same atomizer (wide range of applications)

Possible to atomize very viscous liquid

Self cleaning

Finer atomization at low flow rates

Less sensitive to manufacturing defects

The liquid flow rate and atomization quality can be controlled

Atomization of engine oil

IIT, Kanpur


Performance IIT, Kanpur


Multi-head internally mixed atomizer

• Build to provide a throughput rate in excess to 0.5 LPM with a droplet

size in the range of 20-30 mm

y = 0.149x-0.9698

0

0.5

1

1.5

2

2.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

ALR

Liq

uid

Flo

w R

ate

(L

PM

)

5 psi

10 psi

15 psi

20 psi

25 psi

LIQUID SUPPLY PRESSURE

0

10

20

30

40

50

60

70

80

90

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

ALR

D32

(m

m)

5 psi

10 psi

15 psi

20 psi

25 psi

LIQUID SUPPLY PRESSURE

Flow rate independent of pressure

difference

Reduced feedline coupling

IIT, Kanpur


Ongoing Research







IIT, Kanpur


Emissions in spray flames

0

10

20

30

40

50

60

70

80

90

100

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

No

x (

pp

m)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

NO

x T

he

ory

(p

pm

)

Exp

NOX (Theory)

40

60

80

100

120

140

160

-1 0 1 2 3 4 5

Radial Distance from Center Line (cm)

Saute

r M

ean D

iam

ete

r ( m

m)

z=5mm z=10mm

z=20mm z=35mm

Distance from Flame Holder

•Measured values quite less

compared to the theoretical

predictions

•Inherent fuel staging reduces the

NOx

•Longer flame => less NOx

IIT, Kanpur


Conclusions

• Disturbances can lead to combustion

oscillations

• Recirculating flow helps in reducing

disturbances

• Controlled Atomization can be achieved

through air-assisting

• Spray combustion reduces NOx emissions

through fuel staging

IIT, Kanpur


Acknowledgements

• M. S. Rawat

• S. K. Gupta

• S. Pandey

• P. Berman

• J. Karnawat

• S. Karmakar

• N. P. Yadav

• S. Nigam

• R. Sailaja

• M. Madanmohan

• Dr. K. Ramamurthi

• LPSC (ISRO)

• CFEES (DRDO)

IIT, Kanpur


THANK YOU

IIT, Kanpur


Documents

Gas Turbine Combustion and Power Generation€¦ · Gas Turbine Combustion and Power Generation Dr. A. Kushari Department of Aerospace Engineering IIT, Kanpur PROPULSION LAB, DEPARTMENT