ca05mvwd comparative performance of combined gas turbine systems under three different blade coo

7/30/2019 CA05MVWD Comparative Performance of Combined Gas Turbine Systems Under Three Different Blade Coo

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Comparative performance of combined gas turbine

systems under three different blade cooling schemes

Yousef S.H. Najjar a,*, Abdullah S. Alghamdi b, Mohammad H. Al-Beirutty b

a Department of Mechanical Engineering, Jordan University for Science and Technology, P.O. Box 3030,

Irbid 22110, Jordanb Department of Mechanical Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia

Received 15 January 2003; accepted 7 December 2003

Available online 24 January 2004

Abstract

Recent advances in gas turbine development have led to wider usage of combined power plant for

electrical power generation, and made it possible to reach a thermal efficiency of 5560%. This was a result

of introducing higher turbine inlet temperature (TIT) and other factors. However, this temperature is re-

stricted by the metallurgical limit of turbine blades of about 800 C. Thus, need arises to design efficient

cooling systems to cool the turbine components subjected to such high temperatures.The performance of a combined system with different cooling techniques in the high temperature section

of the turbine is evaluated. A general model of the combined system is developed and used to compare the

performance relevant to the three main schemes of blade cooling, namely air-cooling, open-circuit steam

cooling (OCSC) and closed-loop steam cooling (CLSC).

The performance results of the combined system are expressed in terms of overall efficiency and specific

power as functions of three primary variables and some other secondary variables, which depend on the

considered type of cooling. The primary variables are the TIT, compressor pressure ratio Rc, and thecooling mass ratio Uc. The secondary variables are related to the geometry, aerothermodynamics, andheat transfer parameters of the gas turbine blades. The specific power and efficiency of the gas turbine are

found to be sensitive to the type of cooling technique used.

The combined system with CLSC is found to outperforms the OCSC system in specific power and overallefficiency. Thus, it is clear that more power is created when the cooling steam in the closed-loop is not

thrown away. Under the given conditions the power of the lower steam cycle with CLSC is increased by 6%,

accompanied by 19% rise in cycle efficiency relative to OCSC at similar conditions.

The CLSC results in 11% enhancement in power and 3.2% in efficiency relative to air-cooling. The CLSC

is less sensitive to variations of operating variables at part load.

2003 Elsevier Ltd. All rights reserved.

* Corresponding author. Tel.: +1-962-2-7201000x22569; fax: +962-2-7100836.

E-mail address: [email protected] (Y.S.H. Najjar).

1359-4311/$ - see front matter

2003 Elsevier Ltd. All rights reserved.doi:10.1016/j.applthermaleng.2003.12.002

Applied Thermal Engineering 24 (2004) 19191934

www.elsevier.com/locate/apthermeng
http://mail%20to:%[email protected]/http://mail%20to:%[email protected]/


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Keywords: Performance; Combined systems; Gas turbines; Blade cooling-air; Steam

1. Introduction

There is a strong demand for an efficient and clean power generation system to meet the recentenergy saving requirements and environmental regulations. A combined cycle power plant is one

of the best solutions to fulfill this demand. Its performance depends on the collective perfor-mances of both the topping gas turbine engine and the bottoming steam cycle.

The gas turbine power output and efficiency increase with the turbine inlet temperature (TIT).

However, the maximum value of TIT is restricted by metallurgical limits of turbine bladematerial, which should be kept at about 800 C in order to protect the blades from damage. TheTIT could be raised above this limit by using especially high temperature materials or cooling the

hot turbine components with a suitable coolant. This definitely penalizes the turbine work, but itis more than compensated by the gains in power output and efficiency.

Toshiba Corporation has been studying a 1500 C class gas turbine [1]. Two-percent better

efficiency than competitive cycle designs could reflect a saving of $3040 million in fuel costs overa typical 30-year life of a 400500 MW plant [2]. The goal of 60% efficiency became achievable by

Westinghouse and others through an improvement in operating process parameters for both gasturbine and steam turbine, and raising of TIT to 1700 K [3,4].

The use of ceramic materials in gas turbines obviates the need for elaborate cooling passages.

Much effort has been expended on the development of silicon nitride and silicon carbide materialsfor small turbine blades. However, the need to operate the gas turbines at high TIT requires

materials of excellent high temperature properties, in addition to the advanced technologies forcooling the hot parts of the engine [5].

Most gas turbines use air as a coolant for vanes and blades [6]. However, there are some studies

on alternative coolants such as water, and steam [7,8]. The use of superheated steam as a coolantcan provide some performance advantages, since steam is a more effective cooling medium thanair in that it can absorb more heat. Blade temperature is expected to be lower than conventionally

air-cooled components, and the steam raised in a waste-heat boiler may expand with the com-bustion gases, it increases the turbine mass flow and also provides a certain amount of heataddition. Most of current developments in gas turbine engines utilize air or steam for cooling.

However, steam cooling of turbine blades is expected to allow the turbine inlet temperature to beincreased beyond the temperature at which the turbine material can be used without cooling or

with air-cooling [9], thus increasing the cycle efficiency and power output.In this work, it is intended to study the following combined gas turbine systems:

1. Combined system with air-cooling.2. Combined system with open-circuit steam cooling (OCSC).

3. Combined system with closed-loop steam cooling (CLSC).

In the CLSC system, as the steam passes through the turbine blading, it picks up heat from the

hot components; hence its temperature increases. As steam leaves the cooled component, it enters

1920 Y.S.H. Najjar et al. / Applied Thermal Engineering 24 (2004) 19191934


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into the combined cycle steam turbine loop to do more work. The steam is not thrown away suchas in OCSC, it exits after cooling at nearly reheat conditions and joins the hot reheat steam fromheat recovery steam generator (HRSG) to drive the IP/LP steam turbine section [2,4,9]. Fig. 1

shows a schematic drawing of a closed-loop steam-cooled combined gas turbine system derivedfrom sketch in [2]. Since no cooling steam is ejected from the airfoils, aside from a small amount of

steam leakage through the rotor seals, there is very little influence of the cooling steam on theairfoil flow fields. Also, the reduction in gas path temperature is minimized, since the convective

cond condensercreh cold reheat process

ec economizerev evaporatorf fuel, property of saturated liquid

fwh feed water heaterg gas, property of saturated vaporgc gas path with coolant flow

gt gas turbinehp high pressure

hr heat rejected from the gas turbinehreh hot reheat processhp;o HP steam delivery pressure

ip;o IP steam delivery pressurei state of a substance entering a control volumeo state of a substance exiting a control volume

ov overallm mean, mechanicalp pump

pl pump of low pressureph pump of high pressure

pp pinch pointrec heat recovered in the boiler

s stage, isentropic property, steamsat saturation statesc steam cooling

st steam turbinesup superheatert turbine, tip radius

tc cooled turbineth theoretical valueun unused heat



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heat flux across the airfoils is relatively small. Typically, in the CLSC system, the reduction in gaspath temperature is only about 68 C whereas, with air-cooling mixing reduces the gas path

temperature by approximately 5683 C [3].The OCSC is relatively less desirable, and has some disadvantages such as:

1. The stagnation pressure loss due to friction and aerodynamic losses resulting from the ejectionof the cooling steam from the airfoil into the gas path with consequent irreversible mixing.

2. Internal losses, as the cooling steam is pumped to a pressure significantly higher than that of thepressure of the gas path where it is injected.

3. The cooling steam is lost for ever with the stack gases. New treated make-up water must besupplied to the boiler to compensate for it.

Thus the CLSC system has clearly apparent relative merits.

2. Performance analysis

The intended cooling is suggested to be internal cooling by air or steam using cooling pas-sages of constant cross-sectional area, passing span-wise from root to tip of the gas turbine blades.

Fig. 1. Schematic diagram of combined cycle with closed-loop steam cooling.

Y.S.H. Najjar et al. / Applied Thermal Engineering 24 (2004) 19191934 1923


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Fig. 1 shows a schematic diagram for the combined cycle with CLSC. Fig. 2 shows the temper-ature profile for the HRSG. The corresponding drawings for the air and OCSC resemble to a high

degree these figures except for minor differences. Thereby, they have been omitted for brevity.The general model of a combined cycle will be used to compare the performance parameters of

the three systems using air or steam as a coolant. In this model, performance parameters depend

on many variables, in addition to the type of coolant. These variables are the compressor pressureratio Rc, turbine inlet temperature TIT and inlet coolant temperature Tcr. Consequently, com-parative study of the influence of different cooling schemes on the thermal efficiency and specific

power of the combined cycle will be presented.

2.1. Combined system with closed-loop steam cooling

There are distinct differences in the physical properties of steam and air, which affect heattransfer and cooling characteristics of gas turbine blades. Steam, as a coolant is considerably

better, especially in specific heat, conductivity. Since steam has higher specific heat than air, itsheat carrying capacity is greater than that of air, and it will be seen that steam cooling showsbetter performance.

The detailed drawing of the combined system with CLSC is given in Fig. 2. In this system,steam is used in two ways: first to cool the gas turbine blades and to create more power and

Fig. 2. Temperature profile for HRSG of the combined cycle with closed-loop stem cooling.



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improve efficiency, and second to improve the performance of the IP/LP steam turbines by putting

the picked-up heat back into the lower cycle. Steam exhausts from the HP steam turbine atintermediate pressure and splits in two streams. The main stream is returned to the HRSG for

reheating as hot reheat steam. The remainder of the exhaust steam from HP goes to cool the gasturbine. After cooling the gas turbine, this steam returns at nearly hot reheat condition and joinsthe hot reheated steam from the HRSG to drive the IP/LP steam turbine section to generate morepower. The CLSC scheme involves heat and pressure losses but it avoids mixing and pumping

losses associated with the OCSC. The steam is passed through passageways within the bladeassemblies and through the blades themselves, then it is collected and sent back to the steam cycleas hot steam. Thereby, the convective heat transfer is the only mode of heat transfer. Since steam

is not thrown away and no steam is ejected from the airfoils, there is very little influence of thecooling steam on the airfoil flow field, and hence mixing losses are minimized. In addition, the

reduction in gas path temperature is minimized, since the convective heat flux across the airfoils isrelatively small.

Fig. 3 shows the temperature profile in the heat recovery boiler including the reheat process, atthe design point of TIT 1624 K and Rc 10. Performance at off-design and part load wascalculated using a specially designed computer program over wide range of the operating variables

shown in Table 1. The salient equations used in performance calculations are briefly shown inAppendix A.

2.2. Combined system with air-cooling

With air-cooling, the combined system will give the required performance when running at thedesign point, TIT 1624 K and Rc 10, in addition to the thermodynamic states of the pressure

30

32

34

36

38

40

7 8 9 10 11 12Rc

Wov,MW

air cooling

open-circuit steam

closed-loop steam

Fig. 3. Variation of total specific power with Rc.

Table 1

Range of operating variables for the combined cycle with CLSC

Design point

TIT, K 1324 1424 1524 1624 1724

Rc 7 8 9 10 11



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and temperature, P; T around this system at design conditions. The performance over widerange of operating conditions was carried out by a specially designed computer program.

2.3. Combined system with open-circuit steam cooling

In this case, the steam for cooling of turbine blades is extracted from the lower cycle after it has

expanded in the HP steam turbine. Using superheated steam as a coolant can provide some per-formance advantages. In OCSC, the coolant mixes with the gas flow after removing the heat from

the blades. In this process, the mixing and expansion losses are proportional to the coolant flow.Consequently, there is a strong incentive to minimize the coolant-to-gas mass flow ratio, [8,10,11].

Since the cooling steam is exhausted with the gas flow to the boiler, some of the heat in the

exhaust steam will be converted to useful power in the lower cycle. Performance was calculatedusing a specially designed computer program.

The following assumptions were considered in the computations for the three systems:

1. Ambient conditions: Ta 25 C, Pa 1 bar and ma 52:51 kg/s.2. Diesel fuel: Hc 42517 kJ/kg.3. Pressure losses:

(a) combustion chamber, DPcc 2% of compressor delivery pressure P02,(b) economizer, DPec 3% of boiler inlet pressure Pb;i,(c) evaporator, DPev 2:5% ofPec and in superheater, Psup 2:4% ofPev,(d) hot reheat steam, DPhreh 8:4% of HP steam delivery pressure Php;o,(e) cold reheat steam, DPcreh 5% of IP steam delivery pressure Pip;o.

4. Efficiencies: gm 0:99, gcc 0:98, isentropic efficiency for the steam turbines gst 0:86 and forthe pumps, gp 0:8.

5. Boiler conditions: gb 0:8, feed water enters the boiler at Pb;i 6:5 MPa (Tsat 280 C) andTb;i 120 C and steam leaves the boiler at Tb;o 550 C T12.

6. Reheat processes: after expansion in HP steam turbine to P13, the steam is reheated to T15 460C, (hot reheated steam). After expansion in IP steam turbine to P16, the steam is reheated toT17 380 C, (cold reheated steam).

7. Feed water heater: open type, and direct contact with the steam. The pressure in the feed waterheater is Pfwh 200 kPa and the water leaves it as saturated liquid, but the remaining steam inthe LP turbine expands to 10 kPa.

3. Discussion of results

Steam is a better coolant than air. Specific heat of air remains almost constant over a wide

range from 260 to 1316 C varying from 1.005 to 1.214 kJ/kg K, while the specific heat of steamchanges with both pressure and temperature. The specific heat of steam for gas turbine bladecooling varies from 3.559 kJ/kg K at 4.1 MPa and 260 C to 2.638 kJ/kg K at 0.69 MPa and 1093

C [12]. Thus, substituting air by steam as a coolant appreciably increases the specific power andcycle efficiency.



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Engine performance, namely overall specific power and overall cycle efficiency are calculated at

the design point and over a wide range of operating variables (Table 1): Rc, TIT and cooling massratio Uc.

The variation of performance with Rc is shown in Figs. 3 and 4 for the three systems of cooling.The combined system with CLSC gives the best values of specific power and overall efficiencycompared with air-cooling, whereas the OCSC lies in-between. This is due to the fact that CLSCdoes not affect the expansion gases path and that steam has better heat carrying capacity than air,

moreover, because the coolant is recirculated to improve the performance of the lower cycle. Anincrease of about 11% in specific power with CLSC over air-cooling at the same value of TIT isseen from Fig. 3. Furthermore, the overall specific fuel consumption decreases by about 2.6% at

design point. In Fig. 4, the efficiency of the system with air-cooling initially increases with Rc andlater on decreases, which may be due to the fact that increasing Rc will increase the gas turbine

output, but the positive work gain fails to compensate for the compressor work increase, andhence the efficiency decreases.

Figs. 5 and 6 compare the performance results for the three cooling techniques as function ofturbine inlet temperature, TIT. They show strong dependence of specific power and efficiency onTIT. CLSC system yields comparable performance with OCSC.

50.5

51

51.5

52

52.5

53

53.5

7 8 9 10 11 12Rc

efficiency,

%

air cooling

open-circuit steam

closed-loop steam

Fig. 4. Variation of overall efficiency with Rc.

18

23

28

33

38

43

48

1324 1424 1524 1624 1724 1824

TIT K

Wov,

MW

air cooling

open-circuit steam

closed-loop steam

Fig. 5. Variation of total specific power with TIT.



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40

42

44

46

48

50

52

54

56

1324 1424 1524 1624 1724 1824

TIT K

efficiency,%

air cooling

open-circuit steam

closed-loop steam

Fig. 6. Variation of overall efficiency with TIT.

32

33

34

35

36

37

38

0 2 4 6 8 10

Cooling ratio, %

Wov,MW

air cooling

open-circuit steam

closed-loop steam

Fig. 7. Variation of total specific power with cooling ratio.

51

51.5

52

52.5

53

53.5

54

0 2 4 6 8 10

Cooling ratio, %

efficiency,

%

air cooling

open-circuit steam

closed-loop steam

Fig. 8. Variation of overall efficiency with cooling ratio.



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The study also indicates that the coolant (steam) flow required could be kept relatively small,and this is shown in Figs. 7 and 8. Hence, it becomes clear that increasing the coolant quantity for

example in the air-cooling system gives the lowest values of specific power and efficiency due to thedirect loss of turbine work caused by a corresponding compressor work and the reduction inturbine mass flow, as shown in Figs. 7 and 8.

The performance results of OCSC and CLSC systems show favorable results compared with air-cooling, due to the high specific heat of steam. In the OCSC, more steam is generated using the

waste heat from the gas turbine, the quantity of the generated steam in the heat recovery steamgenerator increases by 9% compared with air-cooling at the same conditions. Table 2 shows thecomparative performance of the three systems for the same Rc, TIT, and blade surface temperatureTb. However, the overall efficiency gov in general is about 53%, which is less than the 60% achievedby General Electric [2]. This is mainly due to the use of diesel fuel (Hc 42; 517 kJ/kg) instead ofnatural gas (Hc 49; 500 kJ/kg), TIT 1624 K instead of 1703 K with GE, Rc 10 instead of 23;and Tb 800 C with Uc 2:5% instead ofTb $ 850 C with coating material and less Uc.

Table 2

Comparison of operating variables and performance parameters for the system with cooled gas turbine

Combined system with

air-cooling


OCSC


CLSCCompression ratio, Rc 10 10 10

GT inlet temperature, TIT 1624 K 1624 K 1624 K

Outlet stagnation temperature, T04 1061.8 K 1061.8 K 1052.1 K

Inlet stagnation pressure, P03 9.8 bar 9.8 bar 9.8 bar

Outlet stagnation pressure, P04 1.04 bar 1.04 bar 1.04 bar

Cooling mass ratio, Uc 8.0267% 3.912% 2.527%

Inlet cooling temperature, Tcr 348.27 C 348.27 C 348.27 C

Mass flow rate of air, ma 52.51 kg/s 52.51 kg/s 52.51 kg/s

Mass flow rate of fuel, mf 1.505 kg/s 1.630 kg/s 1.630 kg/s

Mass flow rate of gas, mg 50 kg/s 54.14 kg/s 54.14 kg/s

Mass flow rate of coolant, mac 4.0133 kg/s 2.118 kg/s 1.368 kg/s

Mass flow of whole gas,mgc

54.013 kg/s 56.26 kg/s 54.14 kg/s

Mass flow rate of steam, ms 11.37 kg/s 12.43 kg/s 11.36 kg/s

Blade relative temperature, BRT 0.451 0.451 0.451

Cooling effectiveness, 0.549 0.549 0.549

Blade surface temperature, Tb 800 C 800 C 800 C

grid Heat recovered in the boiler 39.1 MW 41.9 MW 37.3 MW

Heat rejected from GT, Qhr 46 MW 49.5 MW 45.5 MW

Total unused heat, Qun 6.90 MW 7.60 MW 8.2 MW

Exhaust gas temperature, T7 142.5 C 146.1 C 165.3 C

GT net power, Wgt 18.23 MW 22.24 MW 21.82 MW

GT fuel consumption, sfcgt 0.297 kg/kW h 0.2638 kg/kW h 0.2689 kg/kW h

GT efficiency, ggt 28.48% 32.09% 31.5%

Rankine cycle net power, Wr 14.56 MW 14.04 MW 14.83 MW

Rankine cycle efficiency, gr 37.33% 33.48% 39.75%Overall specific power, Wov 32.79 MW 36.28 MW 36.65 MW

Overall fuel consumption, sfcov 0.165 kg/kW h 0.162 kg/kW h 0.160 kg/kW h

Overall efficiency, gov 51.23% 52.35% 52.89%



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In conclusion, the performance results for the three combined systems at similar operating

conditions of (Rc 10 and TIT 1624 K) are summarized as follows:

By further analysis, one can find the relative effect of operating variables on performance, todecide the trade-offs in research and development. This is shown in the table below, which con-

tains the relative effect of 10% reduction in the operating variables of Rc, TIT, and Uc on theperformance parameters (Wov and gov) for the three schemes:

is clear that 10% reduction in TIT gives the highest effect on performance parameters. Thus, areduction of TIT will significantly decrease the overall specific power and therefore the overall

efficiency. On the other side, the relative effect of 10% reduction inUc on performance is insignificant.

With CLSC, the relative effect of 10% reduction in the operating variables on the performanceparameters is the lowest, which can be considered as an advantage of the system with CLSC over

the previous systems and overcomes a serious drawback for any gas turbine system, which is thedramatic drop in performance at part load. As displayed, the effect of the reduction of Uc is

relatively small, since the coolant is not exhausted.

4. Conclusions

1. Three different cooling techniques are suggested for the gas turbine. Gas turbine cycle efficiencyand the specific power are found to be sensitive to the type of cooling technique used.

2. CLSC of gas turbine blades gives much better overall performance than air-cooling, andOCSC:

(a) Under the conditions considered in this work, specific power of the combined system withCLSC is enhanced by 11% accompanied by 3.2% rise in overall efficiency compared with

air-cooling at similar operating conditions.(b) Increasing of cooling-air negatively affects gas turbine performance. For an increase of 10%

cooling-air, the combined power decreases by 2.3%.

(c) CLSC is less sensitive to variation of operating variables at part load. With air-cooling, thecombined specific power drops by 24% and the efficiency by 7.1% due to 10% reduction in

Cooling scheme Uc, % Wov, MW s:f:c:ov, kg/kW h gov, %Air-cooling 8.0267 32.79 0.165 51.23

OCSC 3.912 36.28 0.162 52.35CLSC 2.527 36.65 0.160 52.89

Air OCSC CLSC

DW, % Dg, % DW, % Dg, % DW, % Dg, %

Rc +2.20 +0.14 +1.65 )0.31 +1.6 )0.29TIT )24.0 )7.11 )23.5 )6.12 )22.4 )5.10Uc +0.86 +0.11 )0.13 )0.13 )0.04 )0.06



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TIT. In contrast, with CLSC, 10% reduction in TIT leads to decrease in specific power by22% and by 5.1% in efficiency.

Appendix A

A.1. Salient equations used in the thermal analysis relevant to combined cycle with air-cooling

Compressor (12):

gc 0:91

&

Rc 1

300

'13

T02 T01 T01 Rn1=n

c 1where

n 1

n

c

ca 1

ca

1

gc

Wtc ma Cpa T02 T01=gm

Combustion chamber (23):

cooling effectiveness; e T03c TbT03c Tcr

and blade relative temperature; BRT 1 e Tb TcrT03c Tcr

fth Cpa12T02 298 Cpa13T03c 298

Cpa13T03c 298 h13T03c 298 Hc

fact fth

gcc

mac Uc mg

mf ma mac fact

hence

_mg _ma _mac 1 fact

Turbine (34) [13]:

gt 0:9 rt 1

250

wt mg Cpg T03c T04c



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where

n 1

n

t

cg 1

cg ! gtc

Performance parameters for gas turbine cycle:

Wn Wt Wtc

s:f:c: _mf 3600

Wn

ggt Wn

_mf Hc

Heat recovery boiler (812):

T6 Tsat DTpp

T9 Tsat DTap

HP steam (1213):

gst h12 h13h12 h13s

and h13 h12 gsth12 h13s

Hot reheat steam (1415):

and T7 T6 Qec Qreh2

mgc Cpg hlfThe total heat recovered in the boiler (812):

Qrec mgc Cpg T4 T7 hlf

The total heat loss to surrounding, unused heat (4-a):

Qun mgc Cpg T7 Ta 0:01 Qrec

HP turbine (1213):

Whp _ms h12 h13

Low pressure pump (2021):

Wpl t20 P21 P20

gp

_Wpl _ms 1 Xfw Wpl

High pressure pump (228):

Wph t22 P8 P22

gp



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hence

_Wph _ms Wph

I/LP steam turbine (1519):

WI=LP _msh15 h16 h17 h18 1 Xfw h18 h19

hence; the total network of rankine cycle is

_Wst _Whp _WI=LP _Wph _Wpl

Overall network:

Wov Wgt Wst

Overall specific fuel consumption:

s:f:c:ov _mf 3600

Wov

Overall efficiency:

gov Wov

_mf Hc 100

32786

1:5053 42517 100 51:23

hence

gov gh gl gh gl tungl

A.2. Equations relevant to the combined cycle steam cooling

Combustion chamber (23):

Uc msc

mg 100

msc Uc mg

mf ma fact and mg ma mf

Turbine (34):Wt _mg Cpav T03c T04c

where

Cpav _mgCpg _mscCps

_mg _msc

Heat recovery boiler (812):

_mgc _mg _msc



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Evaporator and superheater (912):

_ms Q12 _msch15 h14

h12 h9 bdh10 h9 h15 h14

Evaporator (911):

Qev _msh11 h9 bdh10 h9

Economizer (89):

Qec _ms1 bdh9 h8

Low/high pressure pump (2022):

_Wpl _ms _msc 1 Xfwh Wpl

_Wph

_ms

_msc

Wph

HP and I/LP steam turbine (1219):

Whp _ms h12 h13

_WI=LP _ms _msch15 h16 h17 h18 1 Xfwhh18 h19

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[2] R. Farmer, K. Fulton, Design 60% net efficiency in frame 7/9 H steam-cooled CCGT, Gas Turbine World (1995)

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[3] M.S. Briesch, R.L. Bannister, I.S. Diakunchak, D.J. Huber, A combined cycle designed to achieve greater than 60

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[6] D.G. Ainley, Internal air cooling for turbine blades, Reports and Memoranda No. 3013, 1955.

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[8] J.F. Louis, K. Hiraoka, M.A. Elmasri, A comparative study of the influence of different means of turbine coolingon gas turbine performance, ASME Paper No. 83-GT-180, 1983.

[9] H. Cohen, G.F.C. Rogers, H.I.H. Saravanamuttoo, Gas Turbine Theory, 1987, pp. 294297.

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evaluation, ASME Paper No. 79-JPGC-GT-2, 1979.

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ca05mvwd comparative performance of combined gas turbine systems under three different blade coo

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