1. Gas Turbine Combustion
and Power Generation
Dr. A. Kushari
Department of Aerospace Engineering
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
2. Outline
• Introduction
• Advantages and Disadvantages
• Future Requirements
• Gas Turbine Combustors
• Ongoing Research
• Conclusions
• Acknowledgement
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
3. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
4. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
5. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
6. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
7. Emission in Gas Turbines
•Lower emission compared to all conventional methods (except nuclear)
•Regulations require further reduction in emission levels
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
8. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
9. Gas Turbine Combustion
F/A – 0.01
Combustion efficiency : 98%
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
10. Ongoing Research
• Effect of inlet disturbances
• Combustion in recirculating flows
• Spray Combustion
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
11. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
12. Pressure Amplitude variation
= 0.2211 L = 20 cm
•Pressure oscillations increases
with decreasing length
•Dominant frequency 27 Hz
•Acoustic frequency 827 Hz
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
13. Pressure and Heat Release
80
130
180
230
280
330
10 15 20 25 30
Length of Inlet (cm)
Prms
(pascal)
60
70
80
90
100
110
120
130
140
150
160
Phase
angle
(degree)
Prms Phase angle
Less damping with increasing
length
Causes the rise is pressure
fluctuations
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
14. 0
5
10
15
20
25
30
35
40
45
10 15 20 25 30
Length of Inlet (cm)
frequency
(Hz)
110
112
114
116
118
120
122
124
SPL
(Db)
Frequency Amplitude
3.0 /
a
m g s
, = 0.3455
Low Frequency Variation with Inlet
Length
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
15. 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)
Frequency
(Hz)
Measured
Calulated (St = 0.171)
*
s
f D
St
U
St = 0.171 (60 deg cone)
0.171*
0.02
s
U
f
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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
16. Ongoing Research
• Effect of inlet disturbances
• Combustion in recirculating flows
• Spray Combustion
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
17. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
18. Image Processing
Filtered out image from the noises Grayscale image
Intensity image Simulation results
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
19. 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
Non-dimentional
distance(L2/L)
of
second
vortex
to
the
inlet
of
the
combustor
0
0.002
0.004
0.006
0.008
0.01
2.33 3.33 4.33 5.33 6.33
Non-dimensional time
Ratio
of
the
second
vortex
aera
to
the
total
area
of
the
cold
flowfield
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
20. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
21. Combustion in Recirculating Flow
0
0.2
0.4
0.6
0 8 16 24 32 40 48 56
Non-dimensional time
Non
-dimensional
flame
area
200
250
300
350
400
450
0 0.2 0.4 0.6 0.8 1
Non-dimensional distance along the combustor diameter
Temperature
in
degree
centigrate
Time scale reduces, complete combustion, Good pattern factor
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
22. Ongoing Research
• Effect of inlet disturbances
• Combustion in recirculating flows
• Spray Combustion
–Needs and Challenges
–Controlled atomization
–Emissions in spray combustion
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
23. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
24. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
25. Ongoing Research
• Effect of inlet disturbances
• Combustion in recirculating flows
• Spray Combustion
–Needs and Challenges
–Controlled atomization
–Emissions in spray combustion
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
26. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
28. 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
Liquid
Flow
Rate
(LPM)
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
(mm)
5 psi
10 psi
15 psi
20 psi
25 psi
LIQUID SUPPLY PRESSURE
Flow rate independent of pressure
difference
Reduced feedline coupling
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
29. Ongoing Research
• Effect of inlet disturbances
• Combustion in recirculating flows
• Spray Combustion
–Needs and Challenges
–Controlled atomization
–Emissions in spray combustion
IIT, Kanpur
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
30. 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
Nox
(ppm)
0
500
1000
1500
2000
2500
3000
3500
4000
4500
NOx
Theory
(ppm)
Exp
NOX (Theory)
40
60
80
100
120
140
160
-1 0 1 2 3 4 5
Radial Distance from Center Line (cm)
Sauter
Mean
Diameter
(
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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
31. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
32. 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
PROPULSION LAB, DEPARTMENT OF AEROSPACE ENGG.
