OCTOBER 19-20, 2012 - YMCA University of Science & Technology

2.2. Gas Turbines
Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
For the expansion ratio, r e temperature at the exit of the turbine isentropic process can be calculated by
( γ g −1)
γ g
gos gi e
T = T ( r )
The actual temperature T go at the exit of the turbine can be calculated by
T
ηT
=
T
And the inlet and outlet humidity ratios will be the same
w
gi
gi
gi
−T
−T
= w
The energy balance yields the turbine work W T given by the following relation
go
gos
go
WT = hgi − hgo
The exergy balance for the turbine gives the exergy destruction e DT as following
2.3. Combustor
e = ( e − e ) − W
DT gi go T
Mass of fuel supplied can be calculated by energy balance between the energy supplied by the fuel and change in
enthalpy of combustion products due to this heat addition. Change in enthalpy of air after adding fuel in
combustion chamber is
η m CV = h − h = h − h
cc f go gi
3 2
The exergy balance of the combustion chamber yields exergy destruction
Where
and ∆ g = ∆H −T ( s − s )
r r av P R
eDCC = m
fCCe fCC
+ eai − ego
e = ∆ g + R T
fCC r f a
(s P −s R ) is the entropy change during the combustion process and is given as
where
⎡ Tgo pgo ⎤ ⎡ Tgo pgo
⎤
sP − sR = xa ⎢C pa
ln − Ra ln ⎥+ xv ⎢C pv
ln −Rv
ln ⎥
⎣ Tai pai ⎦ ⎣ Tai pai
⎦
x a
1
= and
1 + w
ln
p
x
p
v
f
a
w
=
1 + w
The effect of water vapor present in fuel is neglected and humidity ratio at combustion chamber outlet will be
higher than inlet.
2.4. Air Preheater (regenerator)
Temperature of air (T ao ) at the exit of a heat exchanger can be calculated by
Tao
−T
Heat Exchanger Effectiveness =
T −T
Applying the energy balance equation on the heat exchanger yields
gi
ai
ai
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