Optimum Layout for a Turbofan Engine

P M V Subbarao

Professor

Mechanical Engineering Department

An excellent Choice for Fighter Planes ….

Mixed Flow Turbofan Engine

1 2 3 4 56h

76c

8

0306c pp

Ideal Mixer

• Ideal Mixer : Constant Total Pressure Process.• For a stable operation of the mixer, the inlet static

pressures of core flow and fan flow must be equal.• If they are not, back flow will occur in either the fan

or core.6h6c pp

030706h06c pppp

06h06c MM The stagnation pressure ratio across the fan:

02

06h0p,fan

02

03

p

pr

p

p

1 2 34

5 6h7

6c

8

0p,turbine0p,fancomp0p,02

03

03

04

05

06h0p,fan rrr

p

p

p

p

p

pr

02

04

04

06h

02

06h0p,fan p

p

p

p

p

pr

0p,turbinecomp0p, rr1

0p,turbinecomp0p,1 ττ

Condition for Efficient Mixing

Theory of Jet Propulsion : Just Enough Work

The power inputs to the compressor & fan = The power output of the turbine

turbinefancompressor WWW

comppccpcore

fanppcorecomppfanppcore

Tcfm

TcmTcm

,00,0

,00,0,00

111

111

comppccfanpcomppfanp f

,0,0,0,0,0

111111

comppccfanpcomppfanp f

,0,0,0,0,0

111111

comppcccomppfanp f

,0,0,0,0

1111

compp

comppcc

fanp

f

,0

,0,0

,0

1111

Adiabatic mixing process:

07pfancore06cpfan06hpcore Tcmf1mTcmTcf1m

0706c06h Tfα1αTTf1

fα1

αTTf1T 06c06h

07

00p,turbinecc0,0p,turb0506h TTT

00p,fan0306c TTT

f

T

10 00p,fan0p,turbinecc0,

07

Tf1T

f1

f1TT 0p,fan0p,turbinecc0,

007

1 2 34

5 6h7

6c

8

0prpppppp 0p,fan030706h06c0708

0708 TT

Mixed Flow Turbofan w/o AB

0prppppp 0p,fan030706h06c08

0

1

2

11 prMpp 0p,fan

28808

11

21

0

p

p0p,fan

28M

f

f1TTT 0p,fan0,turbinecc0,

0708

10

1T

T

1

2M 0

0p,fan28 τγ

f1

f1TT 0p,fan0,turbinecc0,

008

α

ατττ

28

088

M2

11

TT

γ

288

28 MRTV γ 88jetmix MRTV γ

Generation of Thrust : The Capacity

acjetmixcoremixedT, V1Vf1mF αα

Propulsive Power or Thrust Power: acmixedT,p VFP

Specific Thrust based on total jet flow S,

f1m

FS

core

mixedT,mixed

α

Thrust Specific Fuel Consumption TSFC

mixedT,

fuel

F

mTSFC

acjetmix

acjetmixcore

fuel

V1Vf1

f

V1Vf1m

mTSFC

αα

αα

Aviation Appreciation

Propulsion Efficiency

Jet the of PowerKinetic Available

Power Thrustηpropulsion

2ac

2jetmix

core

acmixedT,propulsion

V1Vf12

mVF

ηαα

Mixed –Flow Fan : Effect of Bypass Ratio

Non

-dim

ensi

onal

Spe

cific

Thr

ust

Non

-dim

ens i

onal

TS

FCr0p,comp=15

Mac=0.75cc=5.78

Subsonic Operation : Mixed Turbo Fan: Mac=0.75B

ypas

s R

atio

Compressor Pressure Ratio

Fan Pressure Ratio

2

3

4

5

Byp

ass

Rat

io

Compressor Pressure Ratio

Fan Pressure Ratio

Supersonic Operation : Mixed Turbo Fan: Mac=2.0

Subsonic Operation : Mixed Turbo Fan: Mac=0.75

TS

FC

Compressor Pressure Ratio

Fan Pressure Ratio

2

3

4

5

Spe

cific

Thr

ust

Compressor Pressure Ratio

Fan Pressure Ratio

Subsonic Operation : Mixed Turbo Fan : Mac=0.75

2

3

4

5

TS

FC

Compressor Pressure Ratio

Fan Pressure Ratio

2

3

4

5

Supersonic Operation : Mixed Turbo Fan : Mac=2.0

Supersonic Operation : Mixed Turbo Fan : Mac=2.0

Spe

cific

Thr

ust

Compressor Pressure Ratio

Fan Pressure Ratio

2

3

4

5

TS

FC

Compressor Pressure Ratio

Fan Pressure Ratio

2

34

5

Byp

ass

Rat

io

Fan Pressure Ratio

Compressor Pressure Ratio

Designs for Fuel Economy: Subsonic Flight

Designs for High Thrust: Supersonic Flight

6h 7

6c

9

Mixed flow turbofan with After Burner:

8

f

T

10 00p,fan0p,turbinecc0,

07

Tf1T

After burner temperatures are generally less than after combustor temperature.

T08 < T05

Generally the percentage of enhancement in thrust is specified to determine temperature of the gas after burner.

cc0,ab0, 0

08

T

T

0

07,00 11..

T

TfffTcVHf combababcombpab

combf

T

10 00p,fan0p,turbinecc0,comb

07

Tf1T

0prpppppp 0p,fan030706h06c0809

0

1

2

11 prMpp 0p,fan

29909

11

21

0

p

p0p,fan

29M

0TT ab0,08

1T

T

1

2M 0

0p,fan29 τγ

009 TT ab,0

29

099

M2

11

TT

γ

299

29 MRTV γ 99jetmix MRTV γ

Generation of Thrust : The Capacity

acjetmixabcombcoremixedT, V1Vff1mF αα

Propulsive Power or Thrust Power: acmixedT,p VFP

Specific Thrust based on total jet flow S,

abcombcore

mixedT,mixed ff1m

FS

α

TF30: Pratt and Whitney Mixed Flow Turbofan Engine

The TF30−P−414 engine is a mixed flow, dual spool afterburning low by pass turbofan designed and manufactured by Pratt and Whitney Aircraft of West Palm Beach, Florida. The engine incorporates a nine stage low pressure compressor including a three stage fan driven by a three stage low pressure turbine; and a 7 stage axial flow high pressure compressor driven by a single stage high pressure turbine.

SPECIFICATIONS:TF30

• Development of TF30−P−414 was initiated in March 1969. • TF30−P−414A was placed in service in October 1982. • 929 TF30−P−414’s were converted to P−414A’s with

conversion kits; conversion completed November 1987. • 269 P−414A’s were purchased.• Max Design Pressure Ratio, SLS :Fan: 2.14 to 1 Overall:

19.8 to 1

• Bypass airflow ratio: 0.878 to 1• Max rated airflow: 242.0 lbs/s

F110-GE-400 Mixed Flow Turbofan Engine

Details of F110-GE 400• The F110−GE−400 engine is a mixed flow, dual spool afterburning

low by pass turbofan designed and manufactured by General Electric Aircraft Engines in Lynn, Massachusetts.

• The engine is of modular construction, consisting of six engine modules, and an accessories gearbox.

• The engine incorporates a 3−stage fan driven by a two stage low pressure turbine; and a 9−stage axial flow high pressure compressor driven by a single stage high pressure turbine.

• To moderate engine performance at various power levels the engine features a variable geometry system.

• The combustor is a through flow annular type. • The hinged flap cam linked exhaust nozzle is hydraulically actuated. • The engine mounted accessory gearbox provides the necessary

extracted power needed to drive the accessories. • The engine control system regulates speeds, temperature levels and

fuel flow for afterburning and non after burning operation. • The lubrication and ignition system are self contained on the engine.• Development was initiated April 1984 and engine was placed in

service in late 1986

SPECIFICATIONS:F110-GE - 400

• Max Design Pressure Ratio, SLS:Fan:3.2 to 1 • Overall: 29.9 to 1

• Airflow Capacity: Max rated airflow: 270.0 lbs/s