CHAPTER                      8Gas Power Cycles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-1Modeling is apowerfu...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-2The analysis ofmany ...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-6P-v and T-s diagrams...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-7A steady-flow Carnot...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-8T-s diagram forExamp...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-10Nomenclature forrec...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-11Displacement andcle...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-12The net workoutput ...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-13Actual and ideal cy...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-14Schematic of a two-...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-16Thermal efficiencyo...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-18The thermalefficien...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-21T-s and P-vdiagrams...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-22Thermal efficiency ...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-23P-v diagram of anid...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-26T-s and P-v diagram...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-27The execution of th...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-28A steady-flow Erics...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-29An open-cycle gas-t...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-30A closed-cyclegas-t...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-31T-s and P-vdiagrams...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-32Thermal efficiencyo...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-33For fixed values of...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-36The deviation of an...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-38A gas-turbineengine...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-39T-s diagram of aBra...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-40Thermal efficiency ...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-42Comparison ofwork i...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-43A gas-turbineengine...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-44T-s diagram of anid...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-45As the number ofcom...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-48Basic components of...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-51Energy supplied to ...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-52A turbofan engine.8...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-53A modern jetengine ...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-54A turboprop engine....
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-55A ramjet engine.8-3...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-57Under averagedrivin...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-62Aerodynamic draginc...
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Cengel ch08

  1. 1. CHAPTER 8Gas Power Cycles
  2. 2. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-1Modeling is apowerfulengineering toolthat providesgreat insight andsimplicity at theexpense of someloss in accuracy.8-1
  3. 3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-2The analysis ofmany complexprocesses can bereduced to amanageable levelby utilizing someidealizations.8-2
  4. 4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-6P-v and T-s diagrams of aCarnot cycle.8-3
  5. 5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-7A steady-flow Carnotengine.8-4
  6. 6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-8T-s diagram forExample 8–1.8-5
  7. 7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-10Nomenclature forreciprocating engines.8-6
  8. 8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-11Displacement andclearance volumesof a reciprocatingengine.8-7
  9. 9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-12The net workoutput of a cycle isequivalent to theproduct of themean effectivepressure and thedisplacementvolume.8-8
  10. 10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-13Actual and ideal cycles inspark-ignition engines andtheir P-v diagrams.8-9
  11. 11. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-14Schematic of a two-stroke reciprocatingengine.8-10
  12. 12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-16Thermal efficiencyof the ideal Ottocycle as a functionof compression ratio(k = 1.4).8-11
  13. 13. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-18The thermalefficiency of theOtto cycle increaseswith the specificheat ratio k of theworking fluid.8-12
  14. 14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-21T-s and P-vdiagrams for theideal Diesel cycle.8-13
  15. 15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-22Thermal efficiency of theideal Diesel cycle as afunction of compressionand cutoff ratios (k = 1.4).8-14
  16. 16. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-23P-v diagram of anideal dual cycle.8-15
  17. 17. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-26T-s and P-v diagrams of Carnot,Stirling, and Ericsson cycles.8-16
  18. 18. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-27The execution of theStirling cycle.8-17
  19. 19. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-28A steady-flow Ericssonengine.8-18
  20. 20. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-29An open-cycle gas-turbine engine.8-19
  21. 21. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-30A closed-cyclegas-turbine engine.8-20
  22. 22. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-31T-s and P-vdiagrams for theideal Brayton cycle.8-21
  23. 23. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-32Thermal efficiencyof the ideal Braytoncycle as a functionof the pressureratio.8-22
  24. 24. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-33For fixed values ofTmin and Tmax , thenet work of theBrayton cycle firstincreases with thepressure ratio, thenreaches a maximumat rp = (Tmax /Tmin) k/[2(k – 1)], and finallydecreases.8-23
  25. 25. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-36The deviation of anactual gas-turbinecycle from the idealBrayton cycle as aresult ofirreversibilities.8-24
  26. 26. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-38A gas-turbineengine withregenerator.8-25
  27. 27. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-39T-s diagram of aBrayton cycle withregeneration.8-26
  28. 28. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-40Thermal efficiency ofthe ideal Braytoncycle with andwithoutregeneration.8-27
  29. 29. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-42Comparison ofwork inputs to asingle-stagecompressor (1AC)and a two-stagecompressor withintercooling(1ABD).8-28
  30. 30. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-43A gas-turbineengine with two-stage compressionwith intercooling,two-stageexpansion withreheating, andregeneration.8-29
  31. 31. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-44T-s diagram of anideal gas-turbinecycle withintercooling,reheating, andregeneration.8-30
  32. 32. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-45As the number ofcompression andexpansion stagesincreases, the gas-turbine cycle withintercooling,reheating, andregenerationapproaches theEricsson cycle.8-31
  33. 33. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-48Basic components of aturbojet engine and theT-s diagram for the idealturbojet cycle. [Source: The Aircraft Gas Turbine Engine and Its Operation. © United Aircraft Corporation (now United Technologies Corp.), 1951, 1974.]8-32
  34. 34. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-51Energy supplied to anaircraft (from theburning of a fuel)manifests itself in variousforms.8-33
  35. 35. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-52A turbofan engine.8-34 [Source: The Aircraft Gas Turbine and Its Operation. © United Aircraft Corporation (now United Technologies Corp.), 1951, 1974.]
  36. 36. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-53A modern jetengine used topower Boeing 777aircraft. This is aPratt & WhitneyPW4084 turbofancapable ofproducing 84,000pounds of thrust.It is 4.87 m (192in.) long, has a2.84 m (112 in.)diameter fan, andit weighs 6800 kg(15,000 lbm).8-35 Photo Courtesy of Pratt&Whitney Corp.
  37. 37. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-54A turboprop engine.8-36 [Source: The Aircraft Gas Turbine Engine and Its Operation. © United Aircraft Corporation (now United Technologies Corp.), 1951, 1974.]
  38. 38. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-55A ramjet engine.8-37 [Source: The Aircraft Gas Turbine Engine and Its Operation. © United Aircraft Corporation (now United Technologies Corp.), 1951, 1974.]
  39. 39. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-57Under averagedriving conditions,the owner of a 30-mpg vehicle willspend $300 less eachyear on gasolinethan the owner of a20-mpg vehicle(assuming $1.50/galand 12,000miles/yr).8-38
  40. 40. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.FIGURE 8-62Aerodynamic dragincreases and thusfuel economydecreases rapidlyat speeds above55 mph.8-39 (Source: EPA and U.S. Dept. of Energy.)

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