1. Optimal Design of Turbofan
P M V Subbarao
Professor
Mechanical Engineering Department
Its Time to think about fuel Economy!!!

2. Best Selling Turbofans in World CFM series

3. Current Turbofan Engines
Model
Thrust
Bypass ratio
Pressure ratio
Applications
CFM56-7B18
(86.7 kN)
5.5
32.7
Boeing
CFM56-7B20
(91.6 kN)
5.4
Boeing , Boeing
CFM56-7B22
(101 kN)
5.3
CFM56-7B24
(108 kN)
Boeing , Boeing , Boeing
CFM56-7B27
(121 kN)
5.1 Bo

4. Simplified Objective Function
For maximum fuel economy, maximize the denominator.
Fan Effects : Fan Pressure Ratio & Bypass Ratio.

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

6. Relative change in Turbine TR to BPR

7. The final Objective function for best 

8. Optimum Bypass ratio for Minimum TSFC
Solve above equation for optimum bypass ratio to give minimum specific fuel consumption.
Further use of aopt to calculate velocities of cold and hot jets will give ? ????

9. Best  for Maximum Fuel Economy : Effect of Compressor Pressure Ratio
aopt
T04=1700K
r0,p,fan=2.0
Mac=0.9
r0,p,comp

10. Best  for Maximum Fuel Economy : Effect of Fan Pressure Ratio
T04=1700K
r0,p,comp=24.0
Mac=0.9
aopt
r0,p,fan

11. Best  for Maximum Fuel Economy : Effect of Flight Mach Number
T04=1700K
r0,p,comp=24.0
r0,p,fan=2.0
aopt
r0,p,fan=3.0
Mac

12. Selection of Optimum Fan Pressure Ratio
f is a weak function of  !!!???!!!

13. Maximum Fuel Economy : Effect of Compressor Pressure Ratio
T04=1700K
a=4.0
Mac=0.9
rfan,opt
rcomp

14. Maximum Fuel Economy : Effect of Bypass Ratio
rfan,opt
r0,p,comp=24.0
Mac=0.9 a

15. Best  for Maximum Fuel Economy : Effect of Fan Pressure Ratio
T04=1700K
r0,p,comp=24.0
Mac=0.9
aopt
r0,p,fan
rfan,opt a

16. Design Charts : Contours of Constant TSFC
r0p,fan a

17. Design Charts : Contours of Constant Specific Thrust
r0p,fan a

18. Latest Turbofan Models form PW
PW1100G[47]
PW1400G
PW1500G[48]
PW1900G
Fan Diameter
81 in (206 cm)
73 in (185 cm)
Bypass ratio
12.5:1
12:1
Static Thrust
110–160 kN
120–140 kN
85–104 kN
76–102 kN
Compressor
Axial flow, 1 geared fan, 3 stage LPC, 8 stage HPC
Combustor
Twin annular pre-swirl combustor[49]
Turbine
Axial flow, 2-stage HP, 3-stage LP
Application
A320neo family
Irkut MC-21
CSeries
E-Jets E2 190/195
Service entry
January 2016
2018
15 July 2016

19. Green Engines PW1200G PW1500G PW1100G-JM PW1400G-JM PW1900G
Thrust (kN) k
Fuel Burn (vs. current engines) %
-16 %
Noise
(vs. stage 4)
-15 dB
-20 dB
Emissions - CO2 reduction per a/c (tonnes annually)
-2.700
-3.000
-3.600
Emissions - NOx (margin to CAEP 6)
-50 %
-55 %

20. How to Facilitates Afterburner ???
Serves, Defense & Space Applications ….

21. Mixed Flow Turbofan Engine1 2 6c 3 8 6h 7 4 5
Condition for Ideal Mixing: