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1 Proceedings o the National Conerence on THERMODYNAMIC ANALYSIS FOR IMPROVEMENT IN THERMAL PERFORMANCE OF A SIMPLE GAS TURBINE CYCLE THROUGH RETROFITTING TECHNIQUES (INLET AIR EVAPORATIVE COOLING, STEAM INJECTION & COMBINED IAC AND STIG) Shyam Agarwal* 1 and R.S. Mishra 1 1 Department o Mechanical Engineering, Delhi College o Engineering, Bawana Road, Delhi-114, India * Corresponding author Tel.: ; address: sh_agar@redi.com Abstract Retroitting technologies [inlet evaporative cooling system and steam injected gas turbine] have been applied on simple gas turbine cycle or perormance improvement ollowed by parametric analysis. The perormance improvement has been thermodynamically analysed and discussed or retroitted techniques ollowed by perormance studies. The parametric study predicts that retroitting techniques (FCS and STIG) improves net power output, thermal eiciency, power generation eiciency, irst law eiciency and exergetic eiciency (second law eiciency) while heat alls with a considerable increment in uel consumption. Exergy analysis showed that combustion chamber and turbine are most sensitive components o retroitted system. The results show that the power output, thermal eiciency, exergetic eiciency and uel-air ratio have been enhanced 3.1%,.18%,.% and 1.% respectively while heat alls.6% by FCS technology. The power output, thermal eiciency, exergetic eiciency and uel-air ratio have been improved 7.4%, 3.5%, 5.8% and 14.4% respectively while heat alls 1.% by STIG technology. The analysis shows that STIG technology is better than FCS and the combined FCS & STIG technology enhance the power output, thermal eiciency, exergetic eiciency and uel-air ratio 3.5%, 3.5%, 5.7% and 15.% respectively and reduces the heat 1.4%. Keywords: Gas turbine, Retroitting, FCS, STIG, Exergy Nomenclature AP Approach point ( C) PP Pinch point( C) Superscript TIT Turbine Inlet Temperature (K), raction o gas phase at dead state wbt Wet bulb temperature( C) 1 raction o gas phase beore combustion M Molecular weight (kg/kmol) raction o gas phase ater combustion E & Exergy (kw) CH chemical U Internal energy (kj) PH Physical m& mass low (kg/s) PT potential Subscripts Greek symbol sup superheated η eiciency Th thermal λ uel-air ratio HRSG Heat recovery steam generator ω steam-injection ratio GEN Heat generator Exergetic eiciency uel Acronyms and abbreviations REG Regenerator FCS Fog cooling system dbt Dry bulb temperature( C) STIG Steam injection gas turbine 1. Introduction Simple gas turbine power generation systems are widely used in Indian industries due to quick startup and shutdown capabilities. These units are mostly used to ulil the peak load demand but unortunately suer rom very low overall eiciency and reduction in power output during the summer season, when electricity demand is the highest. To investigate the anticipated power shortage, retroitting projects have been seriously gaining momentum to covert these existing simple gas turbine systems into relatively advanced cycle units resulting in both improved eiciency and power output. 195

2 Proceedings o the National Conerence on From the undamnetal thermodynamic point o view, the reason or low thermal eiciency o simple gas turbine are high back work ratio (large part o turbine work used to compress the inlet air) and substantial amount o available energy loss due to high temperature exhaust (oter above 5 C) caused by shat rotation o turbine at a relativelely high back pressure. This waste heat recovery rom the gas turbine exhaust can be utilized to improve generation eiciency through various modiications to basic cycle such as gas to gas recuperation, steam injection, chemical recuperation, inlet air cooling and combined cycle etc. Among many well-established technologies, the combined cycle is d as the most eicient way to recover the energy rom the exhaust or boosting the capacity and eiciency o power generation. However, the combined cycle technology is unsuitable or daily on-o operation pattern units due to low mobility (start-up time). Recently, the steam injection gas turbine (STIG) and inlet air cooling (IAC) by evaporation are the most common practices to enhance the perormance o power generation. Both eature can be implemented in the existing basic system without major modiication to the original system integration in a economic way. In the STIG technology, the steam gened rom the heat-recovery generator (HRSG) is injected into the combustion chamber. Both steam rom the HRSG and air rom the compressor receive uel energy in the combustion chamber and both simultaneously expand inside the existing turbine to boost the power output o turbine. It should be noted that the required injected steam pressure is obtained rom a pump itted in the steam unit. The net power output produced by steam is signiicantly higher than that o air in terms o per unit mass low, due to very small pumping work compared to compressor. The thermodynamic processes o a simple cycle gas turbine can be approximately modeled as a Brayton cycle, in which the back work ratio is usually very high, and the exhaust temperature is oten above 5 C. A high exhaust temperature implies there is plenty o useul energy rejected to the environment. The recovery o this wasted energy can otherwise be used to improve either the power generation capacity or eiciency via retroitting to the basic cycle such as STIG and inlet air cooling by evaporation technology. Since, the speciic heat o steam and hence enthalpy is relatively higher than air at a certain temperature, the STIG method is a very eective alternative to increase the eiciency and boost the power output o gas turbine. Kumar et al. 1 have been developed design methodology or parametric study and thermodynamic perormance evaluation o a gas turbine cogeneration system (CGTS). Wang & Chiou suggested that application o IAC and STIG technique can boost the output and generation eiciency. They concluded that implementing both STIG and IAC eatures cause more than a 7% boost in power and.4 % improvement in heat. Bouam et al. 3 have studied combustion chamber steam injection or gas turbine perormance improvement during high ambient temperature operations. Their research study is to improve the principal characteristics o gas turbine used under extreme ambient condition in Algerian Sahara by injecting steam in the combustion chamber. Srinivas et al. 4 have worked out on sensitivity analysis o STIG based combined cycle with dual pressure HRSG. They concluded that steam injection decreases combustion chamber and gas reheater exergetic loss rom 38.5 to 37.4% compared to the case without steam injection in the combustion chamber. Minciuc et al. 5 have presented thermodynamic analysis o tri-generation with absorption chilling machine. They have ocused on solutions o tri-generation plants based on gas turbine or internal combustion engine with absorption chilling machine. Moran 6 has developed design and economic methodology or the gas turbine cogeneration system. Nishida et al. 7 have analyzed the perormance characteristics o two coniguration o regenerative steam-injection gas turbine (RSTIG) systems. They concluded that the thermal eiciencies o the RSTIG systems are higher than those o regenerative, water injected and STIG systems and the speciic power is larger than that o regenerative cycle. The IAC technology is simply to cool down the inlet air entering the compressor with a cooler. Due to this, the compressor consumes less work and can compress more air per cycle to increase the capacity o the gas turbine. Dierent IAC options are evaporative cooling, mechanical chiller, absorption chiller and thermal energy storage, etc. applied in gas turbine power augmentation. Among them evaporative cooling is the cheapest one. Sinha & Bansode 8 have studied the eect o og cooling system or inlet air cooling. They concluded that perormance parameters indicative o inlet ogging eects have a deinite correlation with the climate condition (humidity and temperature) and showed improvement in turbine power and heat with inlet ogging. Chaker et al. 9 have developed the ormulation or og droplet sizing analysis and discussed various nozzle types, measurement and testing. This study describes the dierent available measurement techniques, design aspects o nozzles, with experimental and provides recommendations or a standardized nozzle testing method or gas turbine inlet air ogging. Salvi & Pierpaloli 1 have studied optimization o inlet air cooling systems or steam injected gas turbines. They proposed the technique o compression inlet air cooling through an ejection system supplied by the exhaust heat o the gas turbine. Bassily 11 has studied the perormance improvements o the intercooled, reheat and recuped gas turbine cycle using absorption inlet-cooling and evaporative ater-cooling. A parametric study o the eect o pressure ratio, ambient temperature, ambient relative-humidity, turbine s inlettemperature (TIT), and the eectiveness o the recuped heat-exchanger on the perormance o varieties o cycles is carried out. Bhargava & Homji 1 have studied parametric analysis o existing gas turbines with inlet 196

3 Proceedings o the National Conerence on evaporative and overspray ogging. This study shows the eects o inlet ogging on a large number o commercially available gas turbines. Although many eorts have been ocused to apply either STIG technology or the IAC method to enhance the gas turbine s perormance, very limited studies are available regarding simultaneous integration o STIG and IAC or the same system. In this study, a simple cycle generation unit is carried as base data and STIG and IAC eatures are retroitting by added in a sequencing o the system. The beneits obtained rom either the STIG or IAC can be distinguished or the integration eect rom the combined STIG and IAC can be realized. The perormance analysis has been carried out by varying ambient temperature, humidity ratio and steam injection ratio. System Description The simple cycle gas turbine system integd with both IAC and STIG eaturing are shown in Figure 1. The basic unit includes compressor, combustor, gas turbine and a generator. A heat recovery steam generator (HRSG) was installed at the downstream exit o the turbine (state point 5) in order to recover the heat rom the exhaust gases. The raction o superheated steam gened rom the HRSG is used or STIG (state point 9) and the remaining steam is used or process application. An evaporative og cooling system (FCS) is installed to cool the ambient air (state point 1 ) as shown in Fig. 1. Fog cooling is an active system which uses very ine og droplets o high pressure water injected through special atomizing nozzles located at discrete points across the inlet duct at high pressure to create the cooling eect. The amount o og is to be monitored base on dry and wet bulb ambient conditions to achieve the required cooling. A typical og cooling system consists o a high pressure pump skid connected or eeding to an array o maniolds located at a suitable place across the compressor inlet duct. The maniolds have a requisite number o og nozzles 6 which inject very ine droplets o water into the inlet air. The discharge through each nozzle is around 3ml/s and produces 3 billion droplets per second. The ine og evapos very ast, thus dropping inlet air temperature. Compressor Fogged & cooled air Fog cooling system Air Fuel Water Ambient air 3 Combustion chamber Steam-injection ω 9 Combustion products Heat recovery steam generator 4 Turbine 5 6 G Remaining superheated P steam (1-ω) 8 Condensate water 7 Exhaust gases Fig. 1- Simple cycle gas turbine with og cooling Modeling and Computer simulation Formulation The ollowing assumptions have been considered or the present study: 1. The composition o dry air has been assumed in terms o molar raction o 1mole o air is: (N =.78981, O =.989, CO =.31 and H O = ).. The heat loss rom the combustion chamber is % o the uel lower heating value. All other components ope without heat loss. 3. Fog cooling system has been maintained or 1% saturation o ambient air at wet bulb temperature o air. 3. The pressure o water injected rom the nozzle into the evaporative cooling chamber has been assumed 138 bar and converts into the og (ine droplets), absorbs latent heat o air through adiabatic mixing. 4. Combustion chamber has been maintained at constant temperature in the presence o steam (in case o steam injection). 197

4 Proceedings o the National Conerence on A computer program has been developed to ormulate and simulate the retroitting techniques over simple gas turbine with a set o steady-state governing equations including mass, energy, entropy and exergy balances using control volume analysis sequentially or compressor, combustor, gas turbine and HRSG. For complete combustion o natural gas (methane) with steam injection in the combustion chamber, chemical equation takes the ollowing orm: [ X 1, N N + X 1, O O + X 1, CO CO + X 1, H OH O] wh O λ CH [ w] [ X ', N N + X ', OO + X ', COCO + X ', H OH O] λ (1) X 1, N X, N = 1+ λ + w () X 1, O λ X, O = 1+ λ + w (3) X 1, CO + λ X, CO = 1+ λ + w (4) X 1, H O + λ + w X, H O = 1+ λ + w Mole raction o N Mole raction o O Mole raction o CO Mole raction o H O (5) where ω is the steam injection ratio deined as the ratio o mass o steam injected to the mass o air supplied. = m & & ω, = m s mg s m a ω & &, ω = ω ( 1 + λ), m& = m& s ω, ω = ω λ (6) where ω is the mass o steam injected to the mass o air supplied, ω is the ratio o mass o steam injected to the mass o combustion gases ormed and ω is the ratio o mass o steam injected to the mass o uel supplied. The maximum amount o permitted STIG is % o mass low o inlet air. The heat transer between exhaust gases and condensate water has been taken place in water heat recovery boiler where superheated steam is gened. m h h = m h (7) exh ( ) ( ) 6 7 w sup h cond where m exh and m w are mass low o exhaust gases o turbine and condensate water, h 6, h 7, h sup and h cond are enthalpies o exhaust gases at state 6 and 7, super-heated steam and condensate water. T = T PP (8) PP sat + TAP = Tsat AP (9) where T pp, T sat and T AP are Pinch point temperature, saturation temperature o water and approach point temperature. PP is the pinch-point dierence and AP is the approach point dierence rom saturation temperature. The temperature o air ater og cooling can be obtained rom an energy balance on the dry air, water spray and air-born water vapour beore and ater the system. Assuming adiabatic mixing, the energy gained by the sprayed water is balanced by the energy lost by the dry air, and the original air-born mixture, ater cooling such that: m (h h ) = m (h h ) +ω m (h h ) w v1 w1 a a1 a1 1 a v1 v1 h where m w and w1 h h (1) are the mass low and enthalpy o cooling water, m a is the mass low o dry air, h ( a1 a1 ) is the enthalpy change o dry air, ( v1 v1 ) is the enthalpy change o water vapour during cooling. The humidity ratio ( ω 1 ) can be speciied as:.6 Pv 1 ω 1 = (11) P1 Pv 1 where P v1 is the partial pressure o water vapour and P 1 is the total atmospheric pressure. From conservation o mass, the amount o water evapod is equal to the mass o water vapour at point 1minus the water vapour originally in the air at point 1. h 198

5 Proceedings o the National Conerence on m ) w = ( 1 ω1 m a ω (1) where ω 1 is the humidity ratio o air ater cooling, The partial pressure o water vapour can be ound rom the respective relative humidity (φ ) by: P = φ (13) v P sat where P and sat P are the saturation pressures o water or the corresponding temperature. Pressure loss in the sat adiabatic mixing is neglected. The enthalpy, entropy, and exergy can be determined at each state point using mass and energy balances. The perormance parameters required or the thermodynamic analysis o retroitted systems are given below: Thermal Eiciency (η Th ): Thermal eiciency o a thermal system is deined as the ratio o net work output W & ) to the total heat input ( Q & ) o the uel. W& net η = Th Q& ( net Generation Eiciency (η Gen ): Generation eiciency o a thermal system is deined as the ratio o electrical power output (W el ) to the total heat input o the uel(q ). W el η = (15) Gen Q Heat-Rate (HR in kj/s/kw): Heat is deined as the ratio o heat produced by the uel ( power output ( HR W & ) o the thermal system. el Q& W& el 199 (14) Q & ) to the electrical = (16) Speciic Fuel-Consumption (SFC): Speciic uel consumption o a thermal system is deined as the ratio o mass o uel to the net work output. It is reciprocal o speciic net work (W spec ). SFC m& W& = (17) net First Law Eiciency ( ): The ratio o all the useul energy extracted rom the system (electricity and process heat) to the energy o uel input is known as irst-law eiciency. First-law eiciency is also known as uel utilization eiciency or utilization actor or energetic eiciency. By deinition, where ( W& + Q& ) el Pr o η = (18) I Q& is process heat. Second Law Eiciency ( ): Since exergy is more valuable than energy according to the second law o thermodynamics, it is useul to consider both output and input in terms o exergy. The amount o exergy supplied in the product to the amount o exergy associated with the uel is a more accu measure o thermodynamic perormance o a system, which is called second-law eiciency. It is also called exergetic eiciency (eectiveness or rational eiciency). By deinition, ( W& + E& ) el pro η = (19) II E& where is the exergy content o process heat and is the exergy content o uel input. Exergy-Destruction Rate ( DR destruction within the system. E& E& D, tot E & )-The component exergy destruction can be compared to the total exergy D E& = () DR Results and Discussion In the present study ollowing conigurations with retroitting have been studied in comparison to simple gas turbine cycle: (i) Simple gas turbine cycle with inlet air cooling (IAC)

6 (ii) Simple gas turbine cycle with STIG (iii)simple gas turbine cycle with both IAC and STIG. Proceedings o the National Conerence on The initial conditions o these system analysis are as shown in Table 1. In the calculation the steady state operation is investigated without considering the turbine blade cooling. The perormance analysis o these retroitted gas turbine system is done by preparing a computer program in EES and validated with Moran 6. The temperature, pressure and gas concentration in each component are calculated by taking into consideration o the compositions and proportions o gases and consequently various parameters (reer Table 1) and exergy loss o these systems are estimated. The net power output and power generation eiciency are 3MW and 9.93% (shown in Table ) respectively. Attachment o evaporative coolers with simple cycle slightly improves the perormance parameters. Due to reduction in compressor work the net power output increases by 3%. The impact o evaporative cooling will be higher in dry summer season where dry bulb temperature is higher and R.H is lower. Simple gas turbine cycle with STIG (or steam injection ratio.1316) signiicantly improves the system eiciencies. The net power output increases by 7.4%. Combination o simple cycle with STIG and evaporative cooling urther improves the system perormance. It is quite obvious that contribution o STIG is quite signiicant. 1.Comparison o simple cycle gas turbine with and without FCS shows that net power output increases by 3.1% and various eiciencies increase by.6% while heat decreases by.6% using FCS technology..comparison o simple cycle gas turbine with and without STIG shows that net power output increases by 7.4% and thermal eiciency increases by 11.4% while heat decreases by 1.% using STIG technology. The power output, power generation eiciency improve appreciably while First-law eiciency and process heat all with increasing amount o STIG. 3.Comparison o simple cycle gas turbine with and without FCS and STIG shows that net power output increases by 3.5% and thermal eiciency increases by 11.59% while heat decreases by 1.4% using FCS and STIG combine technology. The generation eiciency and net power output increases while First-law eiciency (utilization actor) and process heat decreases with increasing amount o STIG. Table 1: Essential input parameters or simple gas turbine cycle and retroitted systems Parameters Simple gas turbine cycle+fog cooling+stig Ambient air temperature at state 1,in K Ambient air pressure at state1, in bar 1.13 Ambient air relative humidity at state1, in % 6 Spray water temperature at state1, in K Spray water pressure at state1, in bar 138 Air inlet pressure to compressor (P 1 ), in bar 1.13 Air inlet temperature to compressor, (T 1 ) in K Relative humidity o inlet air to compressor at 1, in % 1 Pressure ratio o compressor (r p ) 1:1 Isentropic eiciency o compressor (η SC), in %.86 Isentropic eiciency o Turbine (η ST), in %.86 Lower heating value o uel (LHV), in kj/kmol 8361 Mass low o air (m a ), in (kg/s) 81.4 Turbine inlet temperature (TIT) or maximum cycle temperature (T 4 ), in K 15 Injection pressure o uel (methane) (P ), in bar 1 Injection temperature o uel (methane) (T ), in K Pressure drop in combustion chamber, in % 5 Exhaust pressure o combustion products ater HRSG (P 7 ), in bar 1.13 Exhaust temperature o combustion products ater HRSG (T 7 ) in K Pressure o steam generation (P 9 ) in bar Pressure o condensate water at inlet o HRSG (P 8 ), in bar Temperature o condensate water at inlet to HRSG (T 8 ), in K Pressure drop in HRSG on the gas side, in % 5 Amount o steam injected, in (% o the mass low o the air) 1 Temperature o superheated steam STIG (T 9 ), in K Approach point, in K

7 Proceedings o the National Conerence on Pinch point, in K TABLE : Comparison o various perormance parameters o simple gas turbine cycle and retroitted cycles Perormance Parameter Simple gas turbine cycle Simple gas turbine cycle with Fog cooling Simple gas turbine cycle with STIG Simple gas turbine cycle with Fog cooling & STIG First law eiciency (%) Second law eiciency (%) Power generation eiciency (%) Thermal eiciency (%) Fuel-air ratio Steam injection ratio (per kg o mass o uel) Heat (kw/kwh) Speciic net work (kj/kg o uel) or speciic power (kw/kg/s o uel) Speciic uel consumption( kg/kwh) Work-heat ratio (kj/kj) Power-to-heat ratio (kw/kj/s) Speciic work ISO (kw-s/kg o air) Turbine work (MW) Compressor work (MW) Net Power output (MW) Electric work done (MW) Process heat (MW) Table 3 represents the comparison o exergy destruction in the components o simple cycle and retroitted cycles. The exergy destruction represents the waste o available energy. Exergy destruction o all components have been calculated to enhance the understanding o cycle perormance. Table 3 presents the exergy destruction o each cycle component ater retroitting. While examine the exergy destruction or all components, the combustor has the largest exergy destruction and shows the major location o thermodynamic ineiciency because o large irreversibility arising rom the combustion reaction and heat transer. Steam injection will increase the exergy destruction due to more mixing and combustion in the combustor. The exergylosses at position 7 (see Fig.1) is considered as exergy loss through stack. Since part o exhaust heat is recovered in HRSG, the exhaust exergy out o stack can be reduced substantially ater retroitting. The exergy losses through stack will not only waste the available exergy but also dump the thermal pollution to our living environment. Exergetic eiciency or each component can be deined as the ratio o supplied to the component and E & to R E &. Where S E & is the exergy S E & is the exergy recovered rom the component. For a retroitted cycle with R og cooling and STIG, exergetic eiciencies o compressor, turbine, combustor and HRSG are respectively 91%, 93%, 68% and 75%, among which gas turbine and compressor have a higher exergetic eiciency. This implies most o the exergy destruction in compressor and combustor are inexistable. It is interesting to note that although the exergy destruction o combustor is the highest, exergy eiciency o the combustor is higher than that o HRSG. Thereore, there is a greater improvement margin exists or HRSG than or combustor. Table 3: Comparison o exergy destruction in the components or simple gas turbine cycle and retroitted cycles Components Simple gas turbine cycle Simple gas turbine cycle+fog cooling Simple gas turbine cycle+stig Simple gas turbine cycle+fog cooling+stig 1

8 Proceedings o the National Conerence on Exergy destructi on (MW) Exerg y destru ction (%) Percentage exergy destruction is the exergy destruction within a component as a percentage o the total exergy destruction within the simple gas turbine system. 1.Comparison o simple cycle gas turbine with and without FCS shows that exergetic eiciency gets also improve by.64%. However uel-air ratio increases by 1%. The exergy destruction gets reduced into compressor and turbine due to low inlet temperature o air..comparison o simple cycle gas turbine with and without STIG shows that exergetic eiciency gets also improve by 87.4% however uel-air ratio increases by 14.4%. Exergy destruction increases in each system component except air compressor due to mixing o steam and air. The exergetic eiciency improves appreciably exergy destruction (%) o combustion chamber alls with increasing amount o STIG. 3.Comparison o simple cycle gas turbine with and without FCS and STIG shows that exergetic eiciency gets also improve by 87.6% however uel-air ratio increases by 15.%. The exergy destruction gets increased in each system component due increasing mass low. Exergy destruction (%) o system component does not show much variation with relative humidity however with increasing amount o STIG, exergy destruction o each component increases except combustion chamber and compressor. r = 1, T = 5 C, R.H. = 6%, TIT = 147 C Exergy destructi on (MW) Exer gy destr uctio n (%) Exer gy destr uctio n (MW ) Exerg y destru ction (%) Exerg y destru ction (MW) Exerg y destru ction (%) Combustion chamber Gas turbine Air compressor or Air compressor assembly HRSG Stack-loss Overall plant ( E & D ) Power output (MW) Total exergy destruction per MW o output( & MW ) E D Net work dierence with respect to simple gas turbine Simple cycle with og cooling 8.3 Simple cycle with STIG (.1) 9.15 Simple cycle with og cooling and STIG (.1) Cycles Simple cycle with STIG (.) 18.5 Simple cycle with og cooling and STIG (.) Fig. - Comparison o net work output or dierent cycles

9 Proceedings o the National Conerence on r = 1, T = 5 C, R.H. = 6%, TIT = 147 C Generation eiciency (%) Simple cycle Simple cycle with Simple cycle with Simple cycle with Simple cycle with Simple cycle with og cooling STIG (.1) og cooling and STIG (.) og cooling and STIG (.1) STIG (.) Cycles Fig. 3- Comparison o Generation eiciency or dierent cycles The trend o graphs shows that the combination o ogging and STIG with simple cycle gas turbine cycle is a good approach to enhance the perormance o the system on the basis o irst law as well as second law. Fig. & 3 predict that power output is maximum in case o simple cycle with ogging and STIG and generation eiciency is maximum or STIG only. The power output increases as the mass low increases and generation eiciency reduces minutely due to higher uel-air-ratio. Fig. 4- The eect o steam injection ratio on First-law eiciency, generation eiciency and process heat The Fig.4 shows the eect o STIG (-.% o mass low o air) on generation eiciency, irst law eiciency and process heat or ixed inlet air conditions as the air gets satud up to 1% R.H. The irst law eiciency alls with the increasing amount o steam injection ratio. The reason or decrease in First-law eiciency is that the slope o process heat is sharper than the slope o generation eiciency. The generation eiciency increases while the process heat alls with increasing amount o steam injection ratio along with the ogging o air up to 1% R.H. The graph predicts that steam injection eects the generation e iciency, irstlaw eiciency and process heat more than the og cooling o inlet. The exergy destruction (MW) or dierent system components with dierent amount o STIG has been shown in Fig.5. The power output increases or large amount o STIG due to increasing mass low o air. While the exergy destruction increases into the Combustion chamber, turbine and HRSG. The exergy destruction in combustion chamber is highest among all the system components due to highest temperature o combustion chamber. The graph predicts that steam injection increases the exergy destruction in combustion chamber due to mixing o high temperature superheated steam to the combustor highers the overall temperature. The exergy destruction (MW) per MW o power output or dierent system components with dierent amount o STIG has been shown in Fig.6. Due to signiicant increase in power output the o exergy destruction (MW) per MW o power output reduces or combustion chamber, compressor, HRSG and Stack - gases while increases or gas turbine due to increasing mass low with steam o lower exergy. 3

10 Proceedings o the National Conerence on Exergy destruction (MW) r = 1, T = 5 C, R.H. = 6%, TIT = 147 C Combustion chamber Compressor Gas Turbine HRSG Stack-gases Components Simple cycle (PO =3MW) STIG (.1) (PO = 39.15MW) STIG (.) (PO = 48.5MW) Fig. 5- Comparison o Exergy destruction o system components per MW o output or retroitted cycle (Fog cooling and STIG) with simple cycle. Exergy destruction (MW )/MW o Power output r = 1, T = 5 C, R.H. = 6%, TIT = 147 C Combustion chamber Compressor Gas Turbine HRSG Stack-gases Components.339 Simple cycle (PO =3MW) STIG (.1) (PO = 39.15MW) STIG (.) (PO = 48.5MW) Fig. 6- Comparison o Exergy destruction (MW) o system components or retroitted cycle (Fog cooling and STIG) with simple cycle.. Conclusions In this study, the perormance characteristics o simple gas turbine retroitted with either og cooling system (FCS) or /and steam injected gas turbine (STIG) technology have been analyzed and the various eiciencies and net power output have been investigated, In addition, various perormance parameters have also been compared on the basis o irst law as well as second law (exergy) analysis. During summer season as temperature increases, the density o ambient air decreases and hence the mass low decreases which consequences low power output. The FCS technology reduces the ambient temperature and increases relative humidity which ultimately increases mass low and hence power output increases. In this study, the power output improves by 3.1% and thermal eiciency by.6% using FCS technology retroitted with simple cycle gas turbine. As the exhaust gases leaving rom the turbine have very high temperature and undamental thermodynamic analysis predicted that low eiciency o gas turbine has been resulted. The methods used in the past to improve the eiciency were ocused on either increasing the expansion work or decreasing the compression work. In this study, the modiication o STIG and FCS to simple gas turbine enhanced the thermal eiciency up to 11.59% and the power output improved by 3.5%. Although the steam injection will increase the total exergy losses, the exergy loss per MW output is much smaller than that o simple cycle. Presently, the STIG technology is applied only to the gas turbine cycle. It can be extended to the combined power-cycle which are now well established. The present study can be urther extended or thermoeconomic or exergoeconomic analysis. 3. Reerences 1 Nishida K, Takagi T, Kinoshita S, Regenerative steam-injection gas turbine systems, Applied Energy 81 (5) 31-46; Japan. Hawaj O M, Mutairi H, A combined power cycle with absorption air cooling, Energy 3 (7) , Kuwait. 3 Pelster S, Favrat D,Von Spakovsky M R, The thermo economic analysis and environomic modeling and optimization o the synthesis and operation o combined cycle with advanced options, Engineering or gas turbine and power, transaction o the ASME 13 (1)

11 Proceedings o the National Conerence on 4 Bhargava R & Meher-Homji C B, Parametric analysis o existing gas turbines with inlet evaporative and overspray ogging, Journal o Engineering or gas turbines and power 17 (5) 145; Houston. 5 Chaker M, Homji C B M, Mee I I I T, Inlet ogging o gas turbine engines-part II: og droplet sizing analysis, nozzle types, measurement and testing, Journal o engineering or gas turbines and power 16 (4) 559, Monrovia. 6 Bansode S, Sinha R, A thermodynamic analysis or gas turbine power optimization by og cooling system, th national and 9th International ISHMT-ASME heat and mass transer conerence (1). 7 Alexis G K, Perormance parameters or the design o a combined rerigeration and electrical power cogeneration system, International journal o rerigeration 3 (7) , Greece. 8 Kumar A, Kachhwaha S S, Mishra R S, Thermodynamics analysis o a regenerative gas turbine cogeneration plant, Journal o Scientiic & Industrial Research, 69 (1) 5-31; India. 9 Wang F J & Chiou J S, Integration o steam injection and inlet air cooling or a gas turbine generation system, Exergy conversion and Management, 45 (4) 15-6, Taiwan; ROC. 1 Bilgen E, Exergetic and engineering analysis o gas turbine based cogeneration systems, Energy 5 () , Canada. 11 Ondryas I S, Wilson D A, Kawamoto M, Haub G L, Options in gas turbine power augmentation using inlet air chilling, Journal o Engineering or gas turbines and power 113 (1991) 5. 5