2. Parametric Study of Turbofan Engine Performance P M V Subbarao Professor Mechanical Engineering Department Its Time to think about fuel Economy……

3. Thrust Specific Fuel Consumption TSFC

4. Effect of Fan Bypass Ratio r 0,p,fan =2.5 r 0,p,comp =15 T 0max =1200K M ac =0.75

5. TSFC Combined Effect of Fan & Compressor Pressure Ratios  T 0max =1200K M ac =0.75

6. Combined Effect of Fan & Compressor Pressure Ratios  T 0max =1200K M ac =0.75

7. Combined Effect of Fan & Compressor Pressure Ratios TSFC Compressor Pressure Ratio Fan Pressure Ratio

8. Combined Effect of Fan & Compressor Pressure Ratios Specific Thrust kN.s/kg Compressor Pressure Ratio Fan Pressure Ratio r 0p,fan =1.5 r 0p,fan =2.0 r 0p,fan =4.0 r 0p,fan =3.5 r 0p,fan =4.5 r 0p,fan =3.0

9. Optimum Fan Pressure Ratio for Fuel Economy Fan Pressure Ratio TSFC  r 0,p,comp =24 T 0max =1800K M ac =0.9

10. Optimum Fan Pressure Ratio for Compactness Specific Thrust kN.s/kg Fan Pressure Ratio  r 0,p,comp =24 T 0max =1800K M ac =0.9

11. Optimum Fan Pressure Ratio for Propulsion Efficiency Fan Pressure Ratio  r 0,p,comp =24 T 0max =1800K M ac =0.9

12. Fan Effects on Thrust Ratio Fan Pressure Ratio r 0,p,comp =24 T 0max =1800K M ac =0.9 

13. Thrust Ratio : r 0,p,fan =2.5 & M ac =0.75 Compressor Pressure Ratio 

14. Turbofan with After Burner

15. Effect of After Burner : Compactness Turbojet w AB Turbojet w/o AB Turbofan w AB Turbojfan w/o AB For same level of life & Energy

16. Effect of After Burner : Fuel Economy TSFC Turbofan w/o AB Turbojet w/o AB Turbojet w AB Turbofan w AB

17. Optimization Analysis of Turbofan Operational Parameters : Flight Mach number & Ambient conditions. Design Variables : Fan Pressure Ratio, Bypass Ratio, Compressor Pressure Ratio, Combustion Chamber Temperature Ratio. Maximization of specific thrust is not an important issue. Fuel economy is the main focus for optimization.

18. Thrust Specific Fuel Consumption TSFC

19. For small fuel/air ratios: Assume that the value of f is constant:

20. For maximum fuel economy, maximize the denominator. Defined D as Fan Effects : Fan Pressure Ratio & Bypass Ratio. Core Effects : Bypass Ratio, Compressor Pressure Ratio & Combustion Chamber Temperature Ratio.

21. Optimal Selection of Bypass Ratio As fan handles the entire air intake, V coldjet is independent of bypass ratio

22. Rewrite as:

25. Condition for optimum bypass ratio at minimum TSFC. Solve above equation for optimum bypass ratio to give minimum specific fuel consumption. Further use of  opt to calculate velocities of cold and hot jets will gives ? ????

26. Maximum Fuel Economy : Effect of Compressor Pressure Ratio  opt r 0,p,comp T 04 =1700K r 0,p,fan =2.0 M ac =0.9

27. Maximum Fuel Economy : Effect of Fan Pressure Ratio  opt r 0,p,fan T 04 =1700K r 0,p,comp =24.0 M ac =0.9

28. Maximum Fuel Economy : Effect of Flight Mach Number  opt  ac T 04 =1700K r 0,p,comp =24.0 r 0,p,fan =3.0 r 0,p,fan =2.0

29. Optimal Selection of Fan Pressure Ratio

30. Maximum Fuel Economy : Effect of Bypass Ratio r fan,opt  r 0,p,comp =24.0 M ac =0.9

31. Maximum Fuel Economy : Effect of Compressor Pressure Ratio r fan,opt r comp T 04 =1700K  =4.0 M ac =0.9

32. r fan,opt  TSFC 8 7 6 5 4 3 2 1 23 4 5 67 89 16.5 16 15.5 15 14.5 14 13.5 13 17 Contours of Constant TSFC

33. Contours of Constant Specific Thrust r fan,opt  8 7 6 5 4 3 2 1 23 45 6 78 9 500 450 400 350 300 280 260 240 220 200

34. Mixed Flow Turbofan Engine 1 2 3 4 5 6h 7 6c 8