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# Electrical engineering power generation handbook selection, applications, operation, and maintenance

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• 3. ϩ ϩ H1 ϩ ⌬Q ϭ ϩ ϩ H2 ϩ ⌬Wsf (1.5)Enthalpies and internal energies are properties of the fluid. This means that each wouldhave a single value at any given state of the fluid. The specific heat at constant volume iscv ϭ΂ ΃v(1.6)The specific heat at constant pressure iscp ϭ΂ ΃p(1.7)cp Ϫ cv ϭ Rwhere R is the gas constant.For ideal gases:du ϭ cvdT (1.8)∂hᎏ∂T∂uᎏ∂TmV2s2ᎏ2gcmz2gᎏgcmV2s1ᎏ2gcmz1gᎏgcREVIEW OF THERMODYNAMIC PRINCIPLES 1.3TABLE 1.2 Some Common Thermodynamic Symbolscp ϭ specific heat at constant pressure, Btu/(lbm и °F) [J/(kg и K)]cv ϭ specific heat at constant volume, Btu/(lbm и °F) [J/(kg и K)]h ϭ specific enthalpy, Btu/lbm (J/kg)H ϭ total enthalpy, Btu (J)J ϭ energy conversion factor ϭ 778.16 ft и lbf/Btu (1.0 N m/J)M ϭ molecular mass, lbm/lb и mol or kg/kg и moln ϭ polytropic exponent, dimensionlessP ϭ absolute pressure (gauge pressure ϩ barometric pressure), lbf/ft2; unit may be lbf/in2(com-monly written psia, or Pa)Q ϭ heat transferred to or from system, Btu or J, or Btu/cycle or J/cycleR ϭ gas constant, lbf и ft/(lbm и °R) or J/(kg и K) ϭ Rෆ/MRෆ ϭ universal gas constant ϭ 1.545.33, lbf и ft/(lb и mol и °R) or 8.31434 ϫ 103J/(kg и mol и K)s ϭ specific entropy, Btu/(lbm и °R) or J/(kg и K)S ϭ total entropy, Btu/°R or J/kgt ϭ temperature, °F or °CT ϭ temperature on absolute scale, °R or Ku ϭ specific internal energy, Btu/lbm or J/kgU ϭ total internal energy, Btu or Jv ϭ specific volume, ft3/lbm or m3/kgV ϭ total volume, ft3or m3W ϭ work done by or on system, lbf и ft or J, or Btu/cycle or J/cyclex ϭ quality of a two-phase mixture ϭ mass of vapor divided by total mass, dimensionlessk ϭ ratio of specific heats, cp/cv, dimensionless␩ ϭ efficiency, as dimensionless fraction or percentSubscripts used in vapor tablesf refers to saturated liquidg refers to saturated vaporfg refers to change in property because of change from saturated liquid to saturated vaporREVIEW OF THERMODYNAMIC PRINCIPLESDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 8. A constant-pressure process at a pressure greater than the critical pressure is represented byline PQ. If water at a pressure of 40 MPa and 20°C is heated in a constant-pressure process,there will never be two phases present. However, there will be a continuous change of density.THE SECOND LAW OF THERMODYNAMICSThe second law puts a limitation on the conversion of heat to work. Work can always beconverted to heat; however, heat cannot always be converted to work.1.8 CHAPTER ONEFIGURE 1.5 Temperature-volume diagram for water showing liquid and vaporphases (not to scale).TABLE 1.4 Constants for Some Fluids*R, ft и lbf / Pc TcFluid M (lbm и °R) psia bar °R KAir 28.967 53.34 547.43 37.744 557.1 309.50Ammonia 17.032 90.77 1635.67 112.803 238.34 132.41Carbon dioxide 44.011 35.12 1071.34 73.884 547.56 304.20Carbon monoxide 28.011 55.19 507.44 34.995 239.24 132.91Freon-12 120.925 12.78 596.66 41.148 693.29 385.16Helium 4.003 386.33 33.22 2.291 9.34 5.19Hydrogen 2.016 766.53 188.07 12.970 59.83 33.24Methane 16.043 96.40 67.31 46.418 343.26 190.70Nitrogen 28.016 55.15 492.91 33.993 227.16 126.20Octane 114.232 13.54 362.11 24.973 1024.92 569.40Oxygen 32.000 48.29 736.86 50.817 278.60 154.78Sulfur dioxide 64.066 24.12 1143.34 78.850 775.26 430.70Water 18.016 85.80 3206.18 221.112 1165.09 647.27*Multiply values of R by 5.343 to convert to J/(kg и K).REVIEW OF THERMODYNAMIC PRINCIPLESDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 13. The thermal efficiency of the Carnot cycle is dependent on the heat source and heat sinktemperatures. It is independent of the working fluid.Since the Carnot cycle is reversible, it produces the maximum amount of work betweentwo given temperature limits, TH and TL. Therefore, a reversible cycle operating betweengiven temperature limits has the highest possible thermal efficiency of all cycles operatingbetween these same temperature limits. The Carnot cycle efficiency is to be considered anupper efficiency limit that cannot be exceeded in reality.REFERENCES1. El-Wakil, M. M., Power Plant Technology, McGraw-Hill, New York, 1984.2. Van Wylen, J. G., Fundamentals of Classical Thermodynamics, John Wiley & Sons, New York, 1976.REVIEW OF THERMODYNAMIC PRINCIPLES 1.13REVIEW OF THERMODYNAMIC PRINCIPLESDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 16. Net work⌬wnet ϭ (h1 Ϫ h2) Ϫ (h4 Ϫ h3) Btu/lbm (or J/kg) (2.5)Thermal efficiency␩th ϭ ϭ (2.6)For small units where P4 is not much larger than P3,h3 ≈ h4 (2.7)The pump work is negligible compared with the turbine work, the thermal efficiency (withlittle error) is(h1 Ϫ h2) Ϫ (h4 Ϫ h3)ᎏᎏᎏ(h1 Ϫ h4)⌬wnetᎏqA2.2 CHAPTER TWOFIGURE 2.1 Schematic flow diagram of a Rankine cycle.FIGURE 2.2 Ideal Rankine cycles of the (a) P-V and (b) T-s diagrams. Line 1-2-3-4-B-1 ϭ saturated cycle.Line 1′-2′-3-4-B-1′ ϭ superheated cycle. CP ϭ critical point.STEAM POWER PLANTSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 24. Turbine workwT ϭ (h1 Ϫ h2) ϩ (1 Ϫ m•2) (h2 Ϫ h3) ϩ (1 Ϫ m•2 Ϫ m•3) (h3 Ϫ h4) (2.21)Pump work|∑wp| ϭ (1 Ϫ m•2 Ϫ m•3) (h6 Ϫ h5) ϩ (1 Ϫ m•2) (h8 Ϫ h7)ϩ (h10 Ϫ h9) ≈ (1 Ϫ m•2 Ϫ m•3)ϩ (1 Ϫ m•2) ϩ (2.22)Heat rejected|qR| ϭ (1 Ϫ m•2 Ϫ m•3) (h4 Ϫ h5) (2.23)v9 (P10 Ϫ P9)ᎏᎏ␩pJv7 (P8 Ϫ P7)ᎏᎏ␩pJv5 (P6 Ϫ P5)ᎏᎏ␩p J2.10 CHAPTER TWOFIGURE 2.9 A typical combination open-type deaerating feedwater heater. (Courtesy Chicago Heater, Inc.)STEAM POWER PLANTSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 31. where e ϭ electrical fraction of total energy output ϭ [E/ (Eϩ⌬Hs) ]␩e ϭ electric plant efficiency␩h ϭ steam (or heat) generator efficiencyThe combined efficiency ␩c for separate generation is therefore given by␩c ϭ (2.30)Cogeneration is beneficial if the efficiency of the cogeneration plant [Eq. (2.28)] isgreater than that of separate generation [Eq. (2.30)].Types of CogenerationThe two main categories of cogeneration are (1) the topping cycle and (2) the bottomingcycle.The Topping Cycle. In this cycle, the primary heat source is used to generate high-enthalpy steam and electricity. Depending on process requirements, process steam at lowenthalpy is taken from any of the following:● Extracted from the turbine at an intermediate stage (like feedwater heating).● Taken from the turbine exhaust. The turbine in this case is called a back-pressure turbine.Process steam requirements vary widely, between 0.5 and 40 bar.The Bottoming Cycle. In this cycle, the primary heat (high enthalpy) is used directly forprocess requirements [e.g., for a high-temperature cement kiln (furnace)]. The low-enthalpy waste heat is then used to generate electricity at low efficiency.This cycle has lower combined efficiency than the topping cycle. Thus, it is not verycommon. Only the topping cycle can provide true savings in primary energy.Arrangements of Cogeneration PlantsThe various arrangements for cogeneration in a topping cycle are as follows:●Steam-electric power plant with a back-pressure turbine.●Steam-electric power plant with steam extraction from a condensing turbine (Fig. 2.14).●Gas turbine power plant with a heat recovery boiler (using the gas turbine exhaust to gen-erate steam).●Combined steam-gas-turbine cycle power plant. The steam turbine is either of the back-pressure type or of the extraction-condensing type.Economics of CogenerationCogeneration is recommended if the cost of electricity is less than the utility. If a utility isnot available, cogeneration becomes necessary, regardless of economics.The two types of power plant costs are (1) capital costs and (2) production costs. Capitalcosts are given in total dollars or as unit capital costs in dollars per kilowatt net. Capital1ᎏᎏᎏ(e/␩e) ϩ [(1 Ϫ e)/␩h]STEAM POWER PLANTS 2.17STEAM POWER PLANTSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 32. costs determine if a plant is good enough to obtain financing. Thus, it is able to pay the fixedcharges against capital costs.Production costs are calculated annually, and they are given in mills per kilowatt hour(a mill is U.S.\$0.001). Production costs are the real measure of the cost of power generated.They are composed of the following:●Fixed charges against the capital costs●Fuel costs●Operation and maintenance costsAll the costs are in mills per kilowatt hour. They are given byProduction costs ϭ (2.31)where the period is usually taken as one year.The plant operating factor (POF) is defined for all plants asPOF ϭ (2.32)total net energy generated by plant during a period of timeᎏᎏᎏᎏᎏᎏrated net energy capacity of plant during the same periodtotal (a ϩ b ϩ c) \$ spent per period ϫ 103ᎏᎏᎏᎏᎏKWh (net) generated during the same period2.18 CHAPTER TWOFIGURE 2.14 Schematic of basic cogeneration plant with extraction-condensing turbine.STEAM POWER PLANTSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 36. 3.4 CHAPTER THREEFIGURE 3.4 Single-cylinder turbine types. Typical types of single-cylinder tur-bines are illustrated. As shown, condensing turbines, as compared to back-pressureturbines, must increase more in size toward the exhaust end to handle the largervolume of low-pressure steam.FIGURE 3.3 Simple power plant cycle. This diagram shows that the working fluid, steam and water, travelsa closed loop in the typical power plant cycle.STEAM TURBINES AND AUXILIARIESDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 67. through the reservoir breather or in the valve relays. Impurities are small particles sus-pended in the fluid. They have irregular size, shape, and chemical composition.Water should never be introduced into the system during operation and maintenance.The system should also never be cleaned using chlorinated solvents. Nevertheless, waterstill enters the system due to contact of the fluid with air in the reservoir and in the valverelays and drain lines. A vacuum dehydration unit (Fig. 4.17) is normally used to maintainthe water concentration below 2000 parts per million (ppm). The unit takes the fluid fromthe reservoir and then returns the conditioned fluid to the reservoir. The fluid is pumpedfrom the main reservoir into the conditioner reservoir. It is heated to 80°C. Then, it ispassed into a vacuum chamber where the water is extracted. The processed fluid is thenpassed through a Fuller’s earth filter, which reduces the water content further, and alsoTURBINE GOVERNING SYSTEMS 4.21FIGURE 4.17 Fire-resistant fluid conditioner.TURBINE GOVERNING SYSTEMSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 83. LUBRICATION SYSTEMSLUBRICATION REQUIREMENTS AND TYPICALARRANGEMENTSThe turbine bearings must be lubricated to prevent damage that is caused by wear orincreased temperatures.1It is necessary to lift the turbine generator shaft before starting toturn the shaft. The jacking oil system is used to provide this function.The purposes of bearing lubrication are as follows:1. To provide a hydrodynamic oil wedge between the bearing and the shaft.2. To provide an oil flow to maintain the white metal of the bearing below 110°C. Thesources of heat inside the bearing include:a. Thermal conductionb. Friction between the oil film, the journal (portion of the shaft inside the bearing), andthe white metal of the bearingc. Turbulence within the oil itselfThe oil temperature leaving the bearing is normally limited to 71°C. Older units usedthe same oil for lubrication and turbine control and protection (Fig. 8.1). Modern units usefire-resistant fluid (FRF) with a pressure of 7 to 17.5 Megapascals (MPa) for the turbinecontrol system. Figure 8.2 illustrates the lubrication oil system of a modern unit. A directlydriven centrifugal pump delivers oil at 1.1 MPa. The oil from this pump goes through anoil turbine. The oil pressure is reduced across the turbine to 0.3 MPa. The oil turbine dri-ves a booster pump that supplies oil from the main tank to the suction of the centrifugal oilpump. The system is protected against overpressurization by a relief valve mounted on theoil tank. The relief valve is connected to the bearing oil supply line. During normal opera-tion, the directly driven main oil pump provides a highly reliable source of lubrication oil.The alternating-current (AC) auxiliary oil pump provides lubrication during start-up andshutdown. The direct-current (DC) auxiliary pump provides lubrication during emergencyshutdown (upon loss of AC supplies) or when the AC pump fails to start. Lubrication oil isalso supplied to the generator hydrogen seals from this system. However, most modernunits have a separate seal oil system to prevent contaminating the main oil with hydrogen.On these units, the supply from the main lubricating oil is used as a backup to the seal oilsystem. On modern units, the lubricating oil system supplies the following:●Each journal bearing of the turbine, generator, and exciter.●The main thrust surge bearing.●The generator hydrogen seal (this is either a sole supply or a backup system).●The bearings on the turbine-driven boiler feed pump (in plants having this feature).●The lubricating oil system also has filters, strainer, coolers, and tank vents.CHAPTER 88.1Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.Source: POWER GENERATION HANDBOOK
• 88. Jacking Oil Pumps and Priming PumpsThe jacking oil pumps deliver oil at around 30 MPa to the bearings. These are motor-drivenpositive-displacement pumps. They are either multiplunger pumps (Fig. 8.6) or two-shaftgear pumps (Fig. 8.7).OIL TANKSThe main oil tank (Fig. 8.8) has a capacity of 75 m3in modern units. The normal workingvolume is around 50 m3. Baffle plates separate the returning oil to the tank and the pumpsuction in order to assist in deaeration and settlement. It also prevents the formation of stag-nant oil pockets. The tank is designed to provide around 7 min for oil transit time betweenreturn and suction. The trend in modern units is to provide a self-contained section of thetank for the hydrogen seal system. This is done to eliminate the possibility of hydrogen gasentering the main lubricating oil system. If the lubricating oil system is used to provide the8.6 CHAPTER EIGHTFIGURE 8.4 Main lubricating oil pump.LUBRICATION SYSTEMSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 98. 1. Silicon-based grease. It contains molybdenum disulphide. Its operating temperatureis between Ϫ50°C to 300°C.2. Mineral oil with Bentone filler. The upper temperature limit of this grease is 260°C.3. Lithium-based grease. They have a wide range of application, including ball androller bearings.8.16 CHAPTER EIGHT2 CONTROLTHERMOSTATS1 MASTERTHERMOSTATHIGH-LEVEL CUTOFF SWITCHHEATER DRUMSPRAY PIPEVACUUM CONNECTIONPERFORATED DEAERATINGPLATES IN VACUUM DRUMLAGGING FILTERRELIEFRELIEFAIR PRESSUREACCESS DOORTO FILTERPIPI SVSVCLEAN-OILPUMPCLEAN-OILOUTLETDRAINSAMPLECOCKSAMPLECOCKTITIVACUUMTANK DRAINVACUUMRELEASEVACUUMPUMPDIRTY-OILINLETDIRTY-OILPUMPRECIRCULATINGVALVELEVEL SIGHTGLASSHEATERDRAINSILENCERHEATINGELEMENTSDIRTY OIL (WITH WATER)DIRTY OIL (WATERFREE)CLEAN OILDRAINVACUUMFIGURE 8.14 Oil regeneration plant—flow diagram.LUBRICATION SYSTEMSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 100. The first two types of grease are used for lubricating high-temperature sliding surfaces. Themain applications are turbine palms and pivots of steam valves.JACKING OIL SYSTEMSThe oil cannot separate the turbine generator shaft from the babbitt of the bearings whenthe shaft rotates at low speed. If separation is not achieved, the bearings and the shaft couldbecome damaged. However, the oil is able to maintain separation between the shaft and thebabbitt of the bearings when the speed exceeds 100 r/min. A hydrodynamic oil wedge ismaintained between the shaft and the babbitt above this speed. The jacking oil systeminjects high-pressure oil into the bottom of the bearings. It continues the injection of oiluntil the turbine generator floats on an oil film. The jacking oil system is needed until anoil wedge is established. This normally occurs above 200 r/min. The jacking oil systemgenerates a pressure of 30 MPa to lift the turbine generator rotor. The mineral oil used inthe system represents a fire hazard due to the proximity of high-temperature components.Special precautions are needed to reduce the fire hazard. A single pump was used in olderstations. Long pipelines were used to connect the pump to each bearing. This arrangementwas prone to oil leakage. Modern stations install the high-pressure pump on the bearingpedestals (Fig. 8.15). The discharge line of each pump has a pressure relief valve. It pre-vents overpressurization of the liner. The bearings of the turning gear are also providedwith jacking oil during start-up and shutdown. The pipework of the jacking oil system usesclass 1–type welded pipe joints. The high-pressure pipework is mounted near the pedestal.Figure 8.16 illustrates a typical arrangement of a jacking oil pump for a turning gear.GREASING SYSTEMSThe following components require greasing to ensure smooth movements between variousparts:●Turbine pedestals/base plates●Gear pivots of steam valvesSome power plants attempted to provide automatic greasing systems. They used multipis-ton pumps with long pipelines to deliver the grease to the equipment. Unfortunately, thesesystems malfunction regularly due to hardening of the grease in the pipelines. Modernplants provide manual greasing for their equipment. Figure 8.17 illustrates the greasingpoints on the main gear pivots of the steam valves.REFERENCE1. British Electricity International, Modern Power Station Practice, 3d ed., Pergamon Press, Oxford,United Kingdom, 1991.8.18 CHAPTER EIGHTLUBRICATION SYSTEMSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 109. the pressure-regulating valve is to maintain constant pressure at the glands). The pres-sure-regulating valve eventually closes completely when the pressure at the glandsreaches a predetermined value. At this stage, the steam leaking from the glands of theHP and IP turbines is used to seal the glands of the LP turbines. A leak-off valve controlsthe pressure at the glands by dumping steam to an LP heater. This configuration ensuresthe following:●That the pressure at the glands is controlled by one regulating valve at any one time●That there is an automatic changeover from live steam to leak-off steamThe pressure of the steam in the sealing line is displayed locally and in the control room.Alarms annunciate low-pressure conditions.GLAND SEALING SYSTEM 9.5FIGURE 9.4 Glands. (a) HP final glands; (b) LP glands.GLAND SEALING SYSTEMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 110. GLAND STEAM CONDENSERThe gland steam condenser maintains a subatmospheric pressure at the leak-off line of theglands. Thus, it prevents steam leakage from the turbines. A blower is used to vent the con-denser to the atmosphere. Air is drawn into the glands due to the small vacuum created bythe blower. The air mixes with the steam leaking from the turbine. The air is separated from9.6 CHAPTER NINEFIGURE 9.5 Gland steam desuperheater.GLAND SEALING SYSTEMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 111. the steam in the gland condenser. It is passed back to the atmosphere by the vent fans. Thecondensed steam is sent to the main condenser (Fig 9.6).REFERENCE1. British Electricity International, Modern Power Station Practice, 3d ed., Pergamon Press, Oxford,United Kingdom, 1991.GLAND SEALING SYSTEM 9.7FIGURE 9.6 Gland steam condenser.GLAND SEALING SYSTEMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 127. Heat Recovery Steam GeneratorsMost of the heat available in the exhaust gases [normally around 482 to 638°C (900 to1180°F)] of a gas turbine can be recaptured in a heat recovery steam generator (HRSG).The steam can be used in the following applications:●To drive a steam turbine in a combined cycle* plant●For heating purposes in a cogeneration plant●For a process in an industry such as a petrochemical plantThe HRSG (Fig. 10.19) is a counterflow heat exchanger used to generate steam byconvection.The following are its main components:●The superheater: This is the first component exposed to the exhaust gases from the gasturbine. It superheats the saturated steam leaving the boiler.AN OVERVIEW OF GAS TURBINES 10.15FIGURE 10.18 Schematic of an axial-flow turbine. (Courtesy of Westinghouse Electric Corporation.)*A combined cycle consists of a gas turbine working in conjunction with a steam power plant through an HRSG.FIGURE 10.19 Supplementary fired exhaust gas steam generator. (Courtesy of Henry Vogt Machine Company.)AN OVERVIEW OF GAS TURBINESDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 132. 11.4 CHAPTER ELEVENFIGURE 11.3 Centrifugal compressor characteristics. (a) Variation of pressure ratio in acentrifugal compressor; (b) variation of isentropic efficiency in a centrifugal compressor.GAS TURBINE COMPRESSORSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 134. 11.6 CHAPTER ELEVENFIGURE 11.5 Axial-flow compressor characteristics. (a) Variation of pressure ratio in anaxial flow compressor; (b) variation of isentropic efficiency in an axial flow compressor.GAS TURBINE COMPRESSORSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 135. GAS TURBINE COMPRESSORS 11.7FIGURE 11.6 Typical gas turbine compressor characteristic. The basis of gas turbine design and enginegoverning requirements.FIGURE 11.7 Effect of blow-off and increased nozzle area.GAS TURBINE COMPRESSORSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 136. 11.8FIGURE 11.8 Transient trajectories on compressor characteristics (two-shaft machine). Accelerationmoves the operating line toward surge. Deceleration moves the operating line away from surge.FIGURE 11.9 Axial-flow compressor construction. (a) Variable stator vanes; (b) bleed or dump valves.GAS TURBINE COMPRESSORSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.
• 137. GAS TURBINE COMPRESSORS 11.9inlet guide vanes (VIGVs), variable stator vanes (VSVs), or variable controlled bleed ordump valves (VBVs). All these devices avoid surge. They are illustrated in Fig. 11.9.NOMENCLATUREThese are the most widely used symbols in this chapter.m ϭ mass flowr ϭ pressure ratio␩c ϭ isentropic efficiency␳ ϭ density␥ ϭ ratio of specific heatsA ϭ cross-sectional areaP ϭ absolute pressureN ϭ speed of rotationT ϭ absolute temperatureV ϭ flow velocitySuffixes0 ϭ stagnation value1, 2, 3, etc. ϭ reference planesGAS TURBINE COMPRESSORSDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)Copyright © 2004 The McGraw-Hill Companies. All rights reserved.Any use is subject to the Terms of Use as given at the website.