Gas turbine lecture by kpm

Gas Turbine
Power
Generation
K. P. Mudafale
Assistant Professor
Department of Mechanical Engineering
Priyadarshini College of Engineering, Nagpur

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

• 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)

 A gas turbine is a machine delivering mechanical power
or thrust.
 It does this using a gaseous working fluid.
 The mechanical power generated can be used by, for
example, an industrial device.
 The outgoing gaseous fluid can be used to generate
thrust. In the gas turbine, there is a continuous flow of
the working fluid.
 This working fluid is initially compressed in the
compressor. It is then heated in the combustion
chamber. Finally, it goes through the turbine.

Layout gas turbine power plant

How does a Gas Turbine Work?
Gas turbines use the hot gas produced by burning a fuel
to drive a turbine. They are also called combustion
turbines or combustion gas turbines.
Because some of its heat and pressure energy has been
transferred to the turbine, the gas is cooled to a lower
pressure when it leaves the turbine. It is then either
discharged up a chimney (often called a stack) or is directed
to a special type of boiler, called a Heat Recovery Steam
Generator (HRSG), where most of the remaining heat
energy in the gas is used to produce steam.

How does a Gas Turbine Work?
Gas Turbine (Brayton cycle) PV and TS

1) Inlet Air
The air coming into the compressor of a gas turbine must
be cleaned of impurities (such as dust and smoke)
which could erode or stick to the blades of the
compressor or turbine, reducing the power and efficiency
of the gas turbine.
Dry filters or water baths are usually used to carry out
this cleaning.

2) Air Compressor
The air compressors used in gas turbines are made up of
several rows of blades (similar to the blades on a household
fan).
Each row of blades compress and push the air onto the
next row of blades.
As the air becomes more and more compressed, the
sizes of the blades become smaller from row to row.

3) Fuel
Gas turbines can operate on a variety of gaseous or liquid fuels,
Liquid or gaseous fossil fuel such as crude oil, heavy fuel oil, natural
gas, methane, distillate and "jet fuel"
(a type of kerosene used in aircraft jet engines);
Gas produced by gasification processes using, for example, coal,
municipal waste and biomass;
Gas produced as a by-product of an industrial process such as oil
refining.
 When natural gas is used, power output and thermal efficiency of the
gas turbines are higher than when using most liquid fuels.

4) Burners and Combustors
The compressed air and fuel is mixed and metered in special
equipment called burners. The burners are attached to chambers called
combustors.
The fuel & air mixture is ignited close to the exit tip of the burners,
then allowed to fully burn in the combustors.
The temperature of the gas in the combustors and entering the turbine
can reach up to 1350°C. Special heat resistant materials (such as
ceramics) are used to line the inside walls of the combustors.
The area between the combustors and the turbine are also lined.

5) Gas Turbines
Gas turbines produce high quality heat that can be used for industrial
or district heating steam requirements
Gas turbines are an established technology available in sizes ranging
from several hundred kilowatts to over several hundred megawatts.

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.

Emission in Gas Turbines
•Lower emission compared to all conventional methods (except nuclear)
•Regulations require further reduction in emission levels

Applications of Gas turbine
• For supercharging of I.C. engines
• Ship propulsion i.e. Marine engines
• Industrial applications. Like Crude oil pumping,
Refining processes.
• Air craft engines.
• Electric power generation.
• For the turbojet and turbo propeller engines.

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

GAS TURBINE WITH REGENERATION CYCLE
The thermal efficiency of the Brayton cycle increases as a result of
regeneration since less fuel is used for the same work output.
A gas-turbine engine with regenerator.
T-s diagram of a Brayton
cycle with regeneration.

GAS TURBINE WITH REGENERATION CYCLE
Effectiveness of
regenerator
T-s diagram of a Brayton
cycle with regeneration.
Effectiveness under cold-air
standard assumptions
Under cold-air standard
assumptions

GAS TURBINE WITH INTERCOOLING CYCLE

GAS TURBINE WITH REHEATING CYCLE

Brayton cycle with intercooling, reheating, and
regeneration
For minimizing work input to compressor and maximizing work output from turbine:

Problem1) In an air-standard Brayton cycle the air enters the compressor
at 0.1MPa, 15C. The pressure leaving the compressor is 1.0MPa, and
the maximum temperature in the cycle is 1000C. Determine
1.The pressure and temperature at each point in the cycle
2.The compressor work, turbine work, and cycle efficiency.
Solution: For each of the control volumes analyzed,
the model is deal gas with constant specific heat,
value at 300K, and Control volume: Compressor.
Inlet state: P1, T1 known;
state fixed. Exit state: P2 known.
2 1
2 1
1
2 2
1 1
c
k
k
w h h
s s
T P
T P

 

 
  
   
1
2
1
2
2 1 2 1
1.932
556.8
269.5 /
k
k
c p
P
P
T K
w h h C T T kJ kg

 

 
 

    

Control volume: Turbine.
Inlet state: P3, T3 known; state fixed.
Exit state: P4 known.
3 4
3 4
1
3 3
4 4
t
k
k
w h h
s s
T P
T P

 

 
  
 
 
1
3
4
4
3 4 3 4
1.932
710.8
664.7 /
395.2 /
k
k
t p
net t c
P
P
T K
w h h C T T kJ kg
w w w kJ kg

 

 
 

    
  
 
3 2 3 2 819.3 /
H p
q h h C T T kJ kg
    
Control volume: High-temperature heat exchange.
Inlet state: state 2 fixed.
Exit state: State 3 fixed.

Control volume: Low-temperature heat exchange.
Inlet state: state 4 fixed.
Exit state: State 1 fixed
 
4 1 4 1 424.1 /
48.2%
L p
net
th
H
q h h C T T kJ kg
w
q

    
 

Problem 2) Consider an ideal air-standard Brayton cycle in which the air
into the compressor is at 100 kPa, 20°C, and the pressure ratio across
the compressor is 12:1. The maximum temperature in the cycle is
1100°C, and the air flow rate is 10 kg/s. Assume constant specific heat
for the air, value from Table A.5. Determine the compressor work, the
turbine work, and the thermal efficiency of the cycle.

Problems 3) A large stationary Brayton cycle gas-turbine power
plant delivers a power output of 100 MW to an electric generator.
The minimum temperature in the cycle is 300 K, and the maximum
temperature is 1600 K. The minimum pressure in the cycle is 100
kPa, and the compressor pressure ratio is 14 to 1. Calculate the
power output of the turbine. What fraction of the turbine output is
required to drive the compressor? What is the thermal efficiency of
the cycle?

Problems 4) A regenerative gas turbine with intercooling and
reheat operates at steady state. Air enters the compressor at 100
kPa, 300 K with a mass flow rate of 5.807 kg/s. The pressure ratio
across the two-stage compressor is 10. The pressure ratio across
the two-stage turbine is also 10. The intercooler and reheater each
operate at 300 kPa. At the inlets to the turbine stages, the
temperature is 1400 K. The temperature at the inlet to the second
compressor stage is 300 K. The efficiency of each compressor and
turbine stage is 80%. The regenerator effectiveness is 80%.
Determine (a) the thermal efficiency, (b) the back work ratio, (c)
the net power developed, in kW.

Gas turbine lecture by kpm

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