1. Parametric Study of Turbofan Performance
P M V Subbarao
Professor
Mechanical Engineering Department
Identification of Sensitive Design & Operationa Variables ……

2. Performance of An Ideal Turbofan
Inlet

3. Performance Analysis of Turbofan
Performance Parameters: Specific Thrust & TSFC
Operational Parameters : Flight Mach number & Ambient conditions.
Design Variables : Fan Pressure Ratio, Bypass Ratio, Compressor Pressure Ratio, Combustion Chamber Temperature Ratio.
Fan Effects :
Fan Pressure Ratio
Bypass Ratio.
Fan Stream Thrust Vs Total Thrust.

4. Influence of Fan: Pressure Ratio: Mac = 0.75
r0,p,comp=15.0
a=4.0
T0max=1200K

5. Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K
Mac =0.75

6. Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K
Mac =0.75
TSFC

7. Optimum Fan Pressure Ratio for Fuel Economy
=3 a
=4
=6
=5
r0,p,comp=24
T0max=1800K
Mac =0.9 7 12 8 10
TSFC
Fan Pressure Ratio

8. Optimum Fan Pressure Ratio for Compactness
=3
=4
=5 6
Specific Thrust kN.s/kg 7 8 10
r0,p,comp=24 T0max=1800K Mac =0.9 12
Fan Pressure Ratio

9. Optimum Fan Pressure Ratio for Propulsion Efficiency
r0p,comp=24 T0max=1800K Mac =0.9 a
Fan Pressure Ratio

10. Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K
Mac =0.75
Fan Pressure Ratio
r0p,fan=4.0
r0p,fan=3.5
r0p,fan=4.5
r0p,fan=3.0
r0p,fan=2.0
Specific Thrust kN.s/kg
r0p,fan=1.5
Compressor Pressure Ratio

11. Combined Effect of Fan & Compressor Pressure Ratios
T0max=1200K
Mac =0.75
Fan Pressure Ratio
TSFC
Compressor Pressure Ratio

12. Fan Effects on Fuel Economy: r0,p,fan=2.5 & Mac=0.75
=5
=4
=3
=2
=1.5
=1.0 a
=0.5
TSFC
=8
=12
Compressor Pressure Ratio

13. 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.

14. Neglect the value of f in denominator, as the value of f is <<1
Thrust Specific Fuel Consumption TSFC
Neglect the value of f in denominator, as the value of f is <<1

15. Simplified Model for TSFC
For maximum fuel economy, maximize the denominator.

16. Simplified Objective Function
Core Effects : Bypass Ratio, Compressor Pressure Ratio & Combustion Chamber Temperature Ratio.
Fan Effects : Fan Pressure Ratio & Bypass Ratio.

17. Selection of Optimum Bypass Ratio
As fan handles the entire air intake, Vcoldjet is independent of bypass ratio

18. Modified Objective Function
Rewrite OF for best  as:

19. Relative change in Turbine TR to BPR

20. The final Objective function for best 