This document discusses gas turbine combustion systems. It provides information on the basic components and working principles of gas turbines, including the compressor, combustor, turbine, and their functions. Simplistic gas turbine working principles are explained as isentropic compression, constant pressure heat addition in the combustor, and isentropic expansion in the turbine. Equations for thermal efficiency, stagnation enthalpy, and other parameters are also presented. Advantages of gas turbines like high power-to-weight ratio and disadvantages such as higher costs compared to reciprocating engines are summarized.

1. 1
Gas Turbine Combustion Systems
Dr. Eng. Ramzi R .Barwari
Assist .Professor /Thermal Power/Refrigeration &Air-conditioning
Consultant Engineer
Salahaddin University/College of Engineering
Mechanical Engineering Department

2. 2
Gas Turbine
• Simple Cycle

3. 3
Gas Turbine Components
Compressor – Combustor - Turbine

4. 4
Gas Turbine

5. 5
Gas Turbine Combustor Arrangement

6. 6
Simplistic Gas Turbines working principles
1-2 Isentropic compression (in a compressor)
2-3 Constant pressure heat addition (in a combustor)
3-4 Isentropic expansion (in a turbine)
4-1 Constant pressure heat rejection

7. 7
Some Basics

8. 8
Gas Turbine components
Inlet system Collects and directs air into the gas turbine. Often, an air
cleaner and silencer are part of the inlet system. It is designated for a
minimum pressure drop while maximizing clean airflow into the gas turbine.
Compressor Provides compression, and, thus, increases the air density for
the combustion process. The higher the compression ratio, the higher the
total gas turbine efficiency . Low compressor efficiencies result in high
compressor discharge temperatures, therefore, lower gas turbine output
power.
Combustor Adds heat energy to the airflow. The output power of the gas
turbine is directly proportional to the combustor firing temperature; i.e., the
combustor is designed to increase the air temperature up to the material
limits of the gas turbine while maintaining a reasonable pressure drop.

9. 9
Gas Producer Turbine Expands the air and absorbs just enough energy from
the flow to drive the compressor. The higher the gas producer discharge
temperature and pressure, the more energy is available to drive the power
turbine, therefore, creating shaft work.
Power Turbine Converts the remaining flow energy from the gas producer
into useful shaft output work. The higher the temperature difference across the
power turbine, the more shaft output power is available.
Exhaust System Directs exhaust flow away from the gas turbine inlet. Often a
silencer is part of the exhaust system. Similar to the inlet system, the exhaust
system is designed for minimum pressure losses.

10. 10
Simplistic Gas Turbines working principles
1-2 Isentropic compression (in a compressor); h2-h1 = mCp(T2-T1)
2-3 Constant pressure heat addition (in a combustor); h3-h2 = mCp(T3-T2)
3-4 Isentropic expansion (in a turbine); h3-h4 = mCp(T3-T4)
4-1 Constant pressure heat rejection

11. 11
Gas Turbine
minCpTin
(min+mF)CpTout
Shaft power 
mFqRcomb

12. 12
First Law:     W
V
V
h
h
Q 



 2
1
2
2
1
2
2
1
2
2
0
V
h
h 

Stagnation enthalpy
Compressor work )
( 1
2
1
2 T
T
c
h
h p 


Turbine work
)
( 4
3
4
3 T
T
c
h
h p 


Heat input )
( 2
3
2
3 T
T
c
h
h p 


For isentropic process  
4
3
1
1
2
1
2
1
T
T
r
P
P
T
T


















 







 





13. 13
Thermal Efficiency
)
(
)
(
)
(
input
energy
output
net work
2
3
1
2
4
3
T
T
c
T
T
c
T
T
c
p
p
p














 









 1
1
1
r
Net work out   )
( 1
2
4
3 T
T
c
T
T
c
W p
p
net 




14. 14
1
2’
2
3
4
4’
Equipment efficiencies
01
02
01
'
02
T
T
T
T
C
































 
1
1
01
02
01
01
02


 P
P
T
T
T
C




























 



1
04
03
03
04
03
/
1
1
P
P
T
T
T T
'
04
03
04
03
T
T
T
T
T




T
S
Process 1-2’ and 3-4’ ideal
Process 1-2 and 3-4 actual

15. 15
1
2’
2
3
4
4’
T
S
Recuperator
5
6
Heat exchanger effectiveness
02
04
02
05
T
T
T
T




)
(
)
(
)
(
input
energy
output
net work
5
3
1
2
4
3
T
T
c
T
T
c
T
T
c
p
p
p








16. 16
How they work
Energy is added to the gas stream
Combustion increases the temperature,
velocity, and volume of the gas flow
Turbine rotates, powering the compressor
Energy is then extracted in the form of shaft
power, compressed air and thrust

17. 17
Disadvantages of gas turbine engines
More expensive compared to a similar-sized
reciprocating engine
More complex machining operations
Usually less efficient than reciprocating
engines, especially at idle
Delayed response to changes in power
settings

18. 18
Advantages of gas turbine engines
Very high power-to-weight ratio
More size efficient
Moves in one direction only, with fewer
moving parts
Low operating pressures
High operation speeds
Low lubricating oil cost and consumption