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Basics in the Thermodynamic Analyses of the Gas Turbine Power Plant. Prof. R. Shanthini Dept. of C & P Engineering University of Peradeniya. fuel. hot gases. CC. compressed air. C. GT. Gen. gases to the stack. atmospheric air. (W GT ). out. fuel. hot gases.
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Basics in the Thermodynamic Analyses of the Gas Turbine Power Plant Prof. R. Shanthini Dept. of C&P Engineering University of Peradeniya
fuel hot gases CC compressed air C GT Gen gases to the stack atmospheric air
(WGT) out fuel hot gases CC compressed air C GT Gen gases to the stack atmospheric air
(QCC) in (WGT) out (WC) in hot gases CC compressed air 3 2 C GT Gen 4 1 gases to the stack atmospheric air
(QCC) in (WGT) out (WC) in hot gases CC compressed air 3 2 C GT Gen 4 1 gases to the stack atmospheric air
(QGT) out (WGT) out = m ( h – h ) 3 4 g 2 2 + m ( C – C ) / 2 3 4 g hot gases + 3 GT 4 gases to the stack
(QGT) out (WGT) out - (QGT) out = m ( h – h ) 3 4 g 2 2 + m ( C – C ) / 2 3 4 g hot gases = 3 + GT 4 Adiabatic Gas Turbine gases to the stack Kinetic energy change ignored
m ( h – h ) T 3 4 3 g (WGT) out T 4 = m C ( T – T ) g pg 3 4 3 = = GT T at the outlet = T at the inlet 4 Specific heat of gas at constant pressure Mass flow rate of gas
T = m C ( T – T ) 3 g pg 3 4 (WGT) out T 4 3 = changes GT fixed fixed = ? 4 free to choose, but we fix it at some value
= T T P P P 4 3 = m C ( T – T ) 3 4 3 g pg 3 4 (WGT) out T for the given and 4 P = 4 3 = should be as small as possible GT = ? How small should T4 be ? 4
T = m C ( T – T ) 3 P g pg 3 4 3 (WGT) out T 4 P 4 3 3 GT real P3 T ideal 4 4s P4 4 s
P P T = m C ( T – T ) 3 4 3 g pg 3 4 (WGT) ) (-1)/ ( out P 4 = T T 3 4s P 3 T 4s (WGT) out,ideal = m C ( T – T ) g pg 3 4s 3 GT 4
T (WGT) m C ( T – T ) out g pg 3 4 = = m C ( T – T ) (WGT) g pg 3 4s out,ideal - T T 4 3 = - T T 4s 3 Turbine Efficiency 3 GT 4
T T T (-1)/ ( ) P = 4 T T ) T T ( T T 3 = – – 4s P 4s 3 3 3 4 = (WGT) out = m C ( T – T ) (WGT) g pg 3 4s out,ideal 3 GT 4
Let ‘s do some Excel sheet calculations on the Turbine
= 88% T Tinlet = 1200 K Poutlet = 1 bar
= 88% T Tinlet = 1200 K Poutlet = 1 bar
(WGT) out fuel hot gases CC compressed air C GT Gen gases to the stack atmospheric air
(QCC) in (WGT) out (WC) in hot gases CC compressed air 3 2 C GT Gen 4 1 gases to the stack atmospheric air
(QCC) in (WGT) out (WC) in hot gases CC compressed air 3 2 C GT Gen 4 1 gases to the stack atmospheric air
(QC) + m ( h – h ) 2 1 a out 2 2 + m ( C – C ) / 2 2 1 a compressed air 2 C (WC) = in 1 atmospheric air
(QC) + m ( h – h ) 2 1 a out 2 2 + m ( C – C ) / 2 2 1 a Adiabatic Compressor compressed air 2 C (WC) = in 1 atmospheric air
(QC) + m ( h – h ) 2 1 a out 2 2 + m ( C – C ) / 2 2 1 a Adiabatic Compressor Kinetic energy change ignored compressed air 2 C (WC) = in 1 atmospheric air
m ( h – h ) 2 1 a Adiabatic Compressor Kinetic energy change ignored compressed air 2 C (WC) = in 1 atmospheric air
m ( h – h ) 2 1 a = m C ( T – T ) a pa 2 1 Adiabatic Compressor Kinetic energy change ignored compressed air 2 C (WC) = in 1 atmospheric air
T = m C ( T – T ) (WC) 2 a pa 2 1 in T 1 = 2 C T at the inlet 1 T at the outlet = Specific heat of air at constant pressure Mass flow rate of air
T = m C ( T – T ) (WC) 2 a pa 2 1 in T 1 = ? 2 C fixed 1 changes = fixed free to choose, but we fix it at some value
= T T ; P P P = m C ( T – T ) 2 1 (WC) 2 2 2 a pa 2 1 in T for the given and 1 = P 1 = ? 2 C should be as small as possible 1 = How small should T2 be ?
P T 2 = m C ( T – T ) (WC) 2 a pa 2 1 in T 1 P 1 2 3 C T P3=P2 2 4 2s real 4s P4=P1 1 ideal 1 s
= ? T P = m C ( T – T ) (WC) 2 2s a pa 2 1 in ) (-1)/ ( P 2 = T T 1 2s P 1 T 1 (WC) P in,ideal 1 = m C ( T – T ) a pa 2s 1 = 2 C 1 = =
(WC) in,ideal = C (WC) in = m C ( T – T ) a pa 2s 1 - T T 1 2s = - m C ( T – T ) T T a pa 2 1 1 2 Compressor efficiency 2 C 1
C (-1)/ ( ) P = 2 T T / – ) T T ( T T 1 = + 2s P 2s 1 1 2 1 / (WC) = (WC) C in,ideal / m C ( T – T ) = T a pa 2s 1 2 C 1 in
Let ‘s do some excel sheet calculations on the Compressor
= 85% C Tinlet = 300 K Pinlet = 1 bar
= 85% C Tinlet = 300 K Pinlet = 1 bar
(WGT) out (WC) in W net fuel hot gases CC compressed air C GT Gen gases to the stack atmospheric air
(WC) - in,ideal W = net (WC) in W (WGT) net,ideal out (WGT) - out,ideal = Power available for electricity generation
Turbine Work Output
= 85% C = 88% T
(QCC) in W net hot gases CC compressed air 3 2 C GT Gen 4 1 gases to the stack atmospheric air
(QCC) in W net hot gases CC compressed air 3 2 C GT Gen 4 1 gases to the stack atmospheric air
CC CC (QCC) in = m ( h – h ) 3 2 a = m C ( T – T ) a pa 3 2 hot gases CC compressed air 3 2 / / - kinetic energy change ignored - fuel flow rate ignored
= 80% CC Net Work (in MW)
= 85% C = 88% T = 80% CC
Check the assumption of ignoring the fuel flow rate
= 85% C = 88% T = 80% CC
(QCC) in W net hot gases CC compressed air 3 2 C GT Gen 4 1 gases to the stack atmospheric air Heat Loss?
(QCC) in W net hot gases CC compressed air 3 2 C GT Gen 4 Heat Loss 1 gases to the atmosphere through the stack atmospheric air