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# Jet engine ideal analysis

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A deck of slides that goes through a simple analysis of an Ideal Jet Engine

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### Jet engine ideal analysis

1. 1. Jet Engine Ideal Analysis
2. 2. Engine Efficiency • Propulsive Efficiency • Thermal Efficiency • Overall Efficiency
3. 3. Propulsive Efficiency • The propulsive efficiency compares how much work is done on the aircraft, by supplying kinetic energy to the air.
4. 4. Propulsive Efficiency Va m=100kg/s Compressor =10 Exhaust Combustor Turbine =10 Combustor m=100kg/s VJ
5. 5. Thermal Efficiency • The thermal efficiency of an engine is the efficiency of the conversion of the heat energy released by the fuel into kinetic energy in the jet stream.
6. 6. Overall Efficiency • The overall Efficiency compares the work done on the aircraft to the energy given by the fuel.
7. 7. Arrangement of Engine T1=288 K P1=101kPa m=100kg/s T3=1112 K Compressor =10 Combustor Turbine =10 Exhaust Combustor Turbine Entry Temperature 1112°K Compressor compression ratio = Turbine expansion ratio. 10 Specific Heat Capacity of Air at constant Pressure (Cp) Ratio of Specific Heat Capacities for air ( ) Universal Gas Constant (R) 1 kJ/kg °K 1.4 287 kJ/kg °K Inlet Air Temperature 288°K Outside air pressure 101 kPa Mass flow of air 100kg/s Calorific value of fuel is 43,000 kJ/kg
8. 8. Compressor T1=288 K P1=101kPa m=100kg/s T2=556 K P2=1010kPa Compressor =10 T3=1112 K Combustor Turbine =10 Combustor Exhaust
9. 9. Compressor T1=288 K P1=101kPa m=100kg/s T2=556 K P2=1010kPa Compressor =10 T3=1112 K Combustor Turbine =10 Combustor Wc Exhaust
10. 10. Turbine T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2=556 K P2=1010kPa Compressor =10 T4=576 K P4=101kA Combustor Turbine =10 Combustor Exhaust
11. 11. Turbine T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2=556 K P2=1010kPa Compressor =10 T4=576 K P4=101kA Combustor Turbine =10 Exhaust Combustor WT
12. 12. Useful Work T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2=556 K P2=1010kPa Compressor =10 T4=576 K P4=101kA Combustor Turbine =10 26,800kJ Combustor Exhaust Subtract the Work done by the compressor (WC)from the work done on the turbine (WT) to determine the useful work done by the engine on the aircraft. Useful Work = WT – WC. Useful Work = (53,600-26,800)=26,800 kJ
13. 13. Combustor T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2=556 K P2=1010kPa Compressor =10 T4=576 K P4=101kA Combustor Turbine =10 Combustor Q Exhaust
14. 14. Fuel T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2=556 K P2=1010kPa Compressor =10 T4=576 K P4=101kA Combustor Turbine =10 Combustor Q Exhaust
15. 15. Efficiency T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K P2=1010kPa Compressor =10 T4’=576 K P4=101kA Combustor Turbine =10 Combustor Q Exhaust
16. 16. Part 2 T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K P2=1010kPa Compressor =10 T4’=576 K P4=101kA Combustor Turbine =10 Combustor Q Repeat the analysis but with the compressor and turbine efficiencies at 85%. Exhaust
17. 17. Compressor T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 T4’=576 K P4=101kA Combustor Turbine =10 Combustor Q Exhaust
18. 18. Compressor T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 T4’=576 K P4=101kA Combustor Turbine =10 Combustor Q Exhaust
19. 19. Turbine T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 T4’=576 K T4 = 656 K P4=101kA Combustor Turbine =10 Combustor Q Exhaust
20. 20. Turbine T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 T4’=576 K T4 = 656 K P4=101kA Combustor Turbine =10 Combustor Q Exhaust
21. 21. Turbine T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 T4’=576 K T4 = 656 K P4=101kA Combustor Turbine =10 14,100kJ Combustor Exhaust Q Subtract the Work done by the compressor (WC)from the work done on the turbine (WT) to determine the useful work done by the engine on the aircraft. Useful Work = WT – WC. Useful Work = (45,600-31,500)=14,100 kJ
22. 22. Combustor T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 T4’=576 K T4 = 656 K P4=101kA Combustor Turbine =10 14,100kJ Combustor Exhaust Q=50900kJ
23. 23. Combustor T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 T4’=576 K T4 = 656 K P4=101kA Combustor Turbine =10 14,100kJ Combustor Exhaust Q=50900kJ
24. 24. Efficiency T1=288 K P1=101kPa m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 Combustor Turbine =10 T4’=576 K T4 = 656 K P4=101kA 14,100kJ Combustor Exhaust Q=50900kJ
25. 25. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 Combustor Turbine =10 T4’=576 K T4 = ? K P4=?kA 14,100kJ Combustor Q=50900kJ Therefore the work done by the turbine is also 31,500kJ
26. 26. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 Combustor Combustor Q=50900kJ Turbine =10 T4’=576 K T4 = 797 K P4=?kA Nozzle
27. 27. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Combustor Turbine =10 T4’=741 K T4 = 797 K P4=?kA Nozzle
28. 28. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kPa Nozzle
29. 29. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle P5
30. 30. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle Combustor P5=129kPa As P5 is > P1 the nozzle is choked.
31. 31. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle Combustor P5=129kPa
32. 32. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle Combustor P5=129kPa
33. 33. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle Combustor P5=129kPa T5=664K
34. 34. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle Combustor P5=129kPa T5=664K
35. 35. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle Combustor P5=129kPa T5=664K
36. 36. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kA Nozzle Combustor P5=129kPa T5=664K Calculate the Specific Fuel Consumption of the engine. The burning of the fuel heats the air from T2 to T3 Heat Energy required is: Q=m.cp(T3- T2 ) Q = 100 (1)(1112-603) = 50871kJ
37. 37. T1=288 K P1=101kPa m=100kg/s Part 3 T3=1112 K T2’=556 K P3=1010kPa T2=603 K P2=1010kPa Q=50900kJ Compressor =10 Combustor Turbine =10 T4’=741 K T4 = 797 K P4=244kPa Nozzle Combustor P5=129kPa T5=664K
38. 38. What happens when we install an afterburner?
39. 39. T1=288 K P1=101kPa m=100kg/s Afterburner T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 Combustor T4’=576 K T4 = 797 K P4=244kPa Turbine =10 T5 = ? K P5=? Afterburner Combustor Q=50900kJ The exhaust gas is reheated to 2000K. the calculations are the same as that the dry turbojet, but now the nozzle inlet temperature is 2000K. Nozzle
40. 40. m=100kg/s T2’=556 K T2=603 K P2=1010kPa Compressor =10 T3=1112 K P3=1010kPa Q=50900kJ Combustor Combustor Turbine =10 T4’=576 K T4 = 797 K P4=244kPa T5 = ? K P5=129kPa Afterburner Nozzle T1=288 K P1=101kPa Afterburner
41. 41. m=100kg/s T2’=556 K T2=603 K P2=1010kPa Compressor =10 T3=1112 K P3=1010kPa Q=50900kJ Combustor Combustor Turbine =10 T4’=576 K T4 = 797 K P4=244kPa T5 = 1667 K P5=129kPa Afterburner Nozzle T1=288 K P1=101kPa Afterburner
42. 42. m=100kg/s T2’=556 K T2=603 K P2=1010kPa Compressor =10 T3=1112 K P3=1010kPa Q=50900kJ Combustor T4’=576 K T4 = 797 K P4=244kPa Turbine =10 Combustor At the throat of the nozzle, the air is travelling at the speed of sound. Determine the velocity of the jet. T5 = 1667 K P5=129kPa Afterburner Nozzle T1=288 K P1=101kPa Afterburner
43. 43. m=100kg/s T2’=556 K T2=603 K P2=1010kPa Compressor =10 T3=1112 K P3=1010kPa Q=50900kJ Combustor Combustor Turbine =10 T4’=576 K T4 = 797 K P4=244kPa T5 = 1667 K P5=129kPa Afterburner Nozzle T1=288 K P1=101kPa Afterburner
44. 44. m=100kg/s T2’=556 K T2=603 K P2=1010kPa Compressor =10 T3=1112 K P3=1010kPa Q=50900kJ Combustor Combustor Turbine =10 T4’=576 K T4 = 797 K P4=244kPa T5 = 1667 K P5=129kPa Afterburner Nozzle T1=288 K P1=101kPa Afterburner
45. 45. m=100kg/s T2’=556 K T2=603 K P2=1010kPa Compressor =10 T3=1112 K P3=1010kPa Q=50900kJ Combustor Combustor Turbine =10 T4’=576 K T4 = 797 K P4=244kPa T5 = 1667 K P5=129kPa Afterburner Nozzle T1=288 K P1=101kPa Afterburner
46. 46. m=100kg/s T2’=556 K T2=603 K P2=1010kPa Compressor =10 T3=1112 K P3=1010kPa Q=50900kJ Combustor Combustor Turbine =10 T4’=576 K T4 = 797 K P4=244kPa T5 = 1667 K P5=129kPa Afterburner Nozzle T1=288 K P1=101kPa Afterburner
47. 47. m=100kg/s T3=1112 K P3=1010kPa T2’=556 K T2=603 K P2=1010kPa Compressor =10 Combustor Turbine =10 T4’=576 K T4 = 797 K P4=244kPa T5 = 1667 K P5=129kPa Afterburner Combustor Q=50900kJ m=1.18kg Q=120300kJ M=2.797kg Nozzle T1=288 K P1=101kPa Afterburner
48. 48. Comparison between Afterburner and Jet Engine With only the Engine