propulsion options for group design aircraft

Aero Group Design – Dr. K.J. Hart - UH

Aero Group Design ProjectAircraft Propulsion


Lecture Contents• Where do engine thrust requirements originate?• Factors affecting choice of engine type, number & location• How is engine performance data presented?• What approximate size of engine will be needed?• Engine data• Basic take-off and cruise thrust/power - Effects of :

– Forward speed – AIT – altitude– Ratings

• Activity Flow Chart!


Thrust Needed for Flight

Aircraft Require Thrust

• To provide runway acceleration to a speed at which: lift generated > aircraft weight

• To sustain aircraft in level flight against drag forces resulting from its motion through the air.


Need for Thrust - Take-Off

Lift > Weight at take-off speed

Acceleration = (take-off speed)2

2 x available take off distance

Thrust required = (aircraft MTOW x acceleration)+ rolling resistance + aerodynamic drag

V2 = u2 +2asu = 0a = v2/2s

R-R

ThrustLift

Aero Drag

Rolling resistanceWeight


Take-Off Thrust RequiredConsider:• Aerodynamic lift required • Take-off speed• Aerodynamic drag• Ground friction• Length of runway• Runway altitude • Engine thrust vs aircraft speed


Need for Thrust - Cruise

Thrust = Aerodynamic drag+ margin for climb capability

At all cruise altitudes, ambient temperatures & cruising speeds

R-R

Weight

Lift

Aero Drag

Thrust


Number, Size & Position of Engines

• Take-off thrust required• Cruise thrust required• Engine failure case• Engine availability• Weight • Structural loads• C of G• Cost of engine & fuel


Multiple Engine Location

For 2 or more enginesOptions for their location with many factors to be considered:-• Sufficient ground clearance - especially propeller driven aircraft• Minimising effect of an engine failure on control of aircraft• Ensuring clean, non-turbulent, supply of air to engine intake• Effect of engine weight & thrust on aircraft structure & C of G• Cabin noise• Ease of maintenance• Effect of an uncontained engine failure• Minimising aerodynamic drag for high speed fighter aircraft• Vulnerability to battle damage


Engine Performance Data

Fuel BurnUnits: lb/hr or kg/hrSFC (Specific Fuel Consumption)Units: lb/ESHP/hr or kg/kW/hlbs of fuel used per hour per HP of engine power

1 lb/ESHP/hr = 0.60828 kg/kW/h

Fuel BurnUnits: lb/hr or kg/hr

SFC (Specific Fuel Consumption)Units: lb/hr/lbf or kg/N/hr

lbs of fuel used per hour per lb of engine thrust

1 lb/hr/lbf = 0.10197 kg/N/hr

PowerSHP = Actual shaft power deliveredESHP = Equivalent output shaft power

(including exhaust thrust)Units: kW or Horsepower1 kW = 1.341 HP 1 HP = 0.7457 kW

ThrustNet Propulsive Thrust

(Exhaust thrust - Inlet drag)

Units: lb thrust or kN1 kN = 224.8lbf 1 lbf = 4.44822N

TurbopropTurbofan


Aircraft Total Take-Off Thrust vs MTOW

Approximate Total Take-Off Thrust vs MTOW

0

50000

100000

150000

200000

250000

300000

350000

0 100 200 300 400 500 600 700

MTOW (tonne)

Tota

l Max

. Tak

e-O

ff Th

rust

(lbf

)


Maximum Engine Thrust vs Pax


Maximum Engine Thrust vs MTOWEngine Max. Take-Off Thrust vs MTOW

0

20000

40000

60000

80000

100000

120000

0 100 200 300 400 500 600 700

MTOW (tonne)

Engi

ne M

ax. T

ake-

Off

Thru

st (l

bf) 2 engines

3 engines4 engines


Turbofan Powered Aircraft Weight & Thrust Turbofan

Powered Aircraft

Pax (1-cl)

Range (nm)

MTOW (tonne)

Total thrust (lbf)

Engines (1 option shown)

Cruise sfc

lb/hr/lbf Avro RJ-70 94 1230 43.1 28000 4 LF507 0.73 Avro RJ-85 112 960 44 28000 4 LF507 0.73 Fokker F-100 122 1460 45.8 27700 2 RR Tay 620 0.692 Avro RJ-100 128 980 46 28000 4 LF507 0.73 Embraer 195LR 108 1800 50.8 37000 2 GE CF34-10E 0.629 Boeing 717 117 2060 54.9 42000 2 BR715 0.621 Yakolev Yak-42 120 1025 57 ~ 50000 3 Ivchenko D-36 0.636 Boeing 737-500 132 2375 60.6 47000 2 CFM56-3C 0.661 Boeing 737-300 149 2255 62.8 47000 2 CFM56-3C 0.661 Boeing 737-700 149 2255 62.8 45400 2 CFM56-3C 0.625 Airbus A318 129 2800 66 47600 2 PW6124 0.656 ‘Boeing’ MD81 172 1543 67.8 40000 2 JT8D-200 0.747 ‘Boeing’ MD87 139 2852 67.8 40000 2 JT8D-200 0.747 Boeing 737-400 168 2060 68 47000 2 CFM56-3C 0.661 Airbus A319 145 3700 75.5 48960 2 V2522-A5 0.586 Airbus A320 180 3000 77 49600 2 V2527-A5 0.586 Boeing 737-800 189 2930 79 52600 2 CFM56-3C 0.625 Airbus A321 220 2250 85 63200 2 V2533-A5 0.586 Tupolev TU-214 210 3374 110.7 70550 2 Perm PS-90A 0.617 Boeing 757-200 228 3900 115.7 86200 2 RB211-535E4 0.617 Ilyushin IL62 186 4840 162 4 Kuznetsov NK84 Boeing 787-3 ~330 3400 163.7 106400 2 RR Trent 1000E 0.493


Aircraft Total Take-Off Thrust vs MTOW

Approximate Total Take-Off Thrust vs MTOW

0250005000075000

100000125000150000175000200000225000250000

0 50 100 150 200 250 300

MTOW (tonne)

Tota

l Max

. Tak

e-O

ff Th

rust

(lbf

)


Engine Options• High Bypass Turbofans

– Good sfc– High lapse rate with forward speed

• CFM56 (20000 – 35000) lbf• V2500 (22000 – 33000) lbf• PW6000 23000 lbf• BR715 (18000 – 21000) lbf• GE CF34-10 18500 lbf

• Turboprops– Improved fuel burn compared to turbofan– Limited aircraft forward speed – Image – Noise

• AE2100 (3600 – 4600) HP• PW150A 5071 HP• TP400-D6 11000 HP

• Propfans– Improved fuel burn compared to turbofan– Novel – Noise


Engine Size

Approximate High BPR Turbofans Diameter vs Thrust

020406080

100120140160

0 20000 40000 60000 80000 100000 120000

Thrust lbf

Dia

met

er

Approximate High BPR Turbofans Length vs Thrust

0

50

100

150

200

250

300

0 20000 40000 60000 80000 100000 120000

Thrust lbf

Leng

th in

Approximate High BPR Turbofans Weight vs Thrust

02000400060008000

100001200014000160001800020000

0 20000 40000 60000 80000 100000 120000

Thrust lbf

Wei

ght l

b


Operational Effects on Thrust & Fuel Burn• Thrust & fuel burn depend on mass flow of air through engine• Mass flow of air through engine depends on:

– Forward speed of aircraft– Ambient pressure & temperature– Altitude


Effects of Forward Speed on Engine ThrustMomentum Thrust = m (Cexhaust - Ca)

Thrust ∝ (Cexhaust - Ca)• For constant Cj,

thrust reduces as Ca increases

Thrust ∝ m• As Ca increases,

– Ram pressure rise increases– ρ increases– mair increases– Thrust increases


Effects of Forward Speed on Fuel Burn

• Thrust reduces as speed increases

• Air density increases as speed increases due to ram effect

• Air mass flow increases as speed increases• Fuel flow increases as speed increases

• SFC deteriorates as speed increases


Effect of Ambient Temperature on Engine Thrust & Fuel Burn

Control action needed on amount of fuel injected into combustion chamber to prevent excessive rotational speeds and gas/component temperatures

• ρair decreases• mair decreases• Thrust or power decreases

• Compressor work at same ωdecreases

• mfuel decreases

• ρair increases• mair increases• Thrust or power increases

• Compressor work at same ωincreases

• mfuel increases

Ambient Air Temperature Increases

Ambient Air Temperature Decreases


Effect of Altitude on Engine Performance

• Ambient air pressure reduces(ρ, mair , thrust reduce)

• Ambient air temperature constant(ρ, mair , thrust constant)

Net thrust DECREASES at a faster rate

• Ambient air pressure reduces(ρ, mair , thrust reduce)

• Ambient air temperature reduces(ρ, mair , thrust increase)

T ‘lapse rate’ < P ‘lapse rate’Net thrust DECREASES with altitude

Above 36000 ftUp to 36000 ft


Runway Altitude• Engine available thrust varies with altitude of ‘runway’• Aircraft weight does not vary with altitude of ‘runway’

• Some typical airport elevations (feet above sea-level):-• London Heathrow (80)• Madrid (1998) • Teheran (Iran) (3949) • Johannesburg (SA) (5557)• Mexico City (7341)• Quito (Ecuador) (9228) • La Paz (Bolivia) (13354)

A340-600 in La Paz (Bolivia)(airport altitude = 13354 feet)


Engine Rating Structure Take-Off Rating• Maximum power available• Used only during take-off operation• Generally limited to a maximum of 5 minutes duration.

Maximum Continuous Rating• No time limit• Used during unusual situations at discretion of pilot• (eg single engine cruise for a twin engine aircraft)

Maximum Climb Thrust• May be time limited (typically 30 minutes)• Used for normal climb to cruise altitude or when changing altitudes• Rating is sometimes same as Maximum Continuous

Maximum Cruise Thrust• Used for any time period during normal cruise at discretion of pilot• Lower cruise power used where possible to conserve fuel & engine life

Idle Speed• Not actually a power rating• Lowest usable thrust setting for either ground or flight operation


Generic (KTF) High BPR Turbofan Engines

Engine Datum Take-off thrust (lbf)

Diameter in

Length in

Weight lb

KTF10 10000 43.7 73.7 1933KTF15 15000 50.8 86.8 2812KTF20 20000 57.4 97.5 3673KTF25 25000 63.8 106.6 4524KTF30 30000 69.8 114.8 5368KTF35 35000 75.5 122.1 6209KTF40 40000 80.8 128.9 7048KTF45 45000 85.8 135.1 7885KTF50 50000 90.5 141.0 8723KTF55 55000 94.8 146.5 9514KTF60 60000 98.8 151.7 10299KTF65 65000 102.4 156.7 11078KTF70 70000 105.8 161.4 11851KTF75 75000 108.7 166.0 12620KTF80 80000 111 170.4 13384KTF85 85000 113 175 14500KTF90 90000 115 179 15000KTF95 95000 117 183 15730KTF100 100000

G

raph

1 fo

r al

titud

e &

Mac

h N

o. e

ffec

ts

120 187 16482


Take-Off Thrust Variation with Altitude, AIT & Forward Speed

60

65

70

75

80

85

90

95

100

0 0.1 0.2 0.3

Mach No.

Thru

st/T

hrus

t at S

ea-le

vel I

SA s

tatic

ISA 6000ft

ISA 4000ft

Sea-level ISASea-level ISA+20ISA 2000ft

Graph 1


Generic (KTF) High BPR Turbofan EnginesEngine Datum Take-off

thrust (lbf) Take-off sfc (lb/hr/lbf)

KTF07 7500 KTF10 10000 KTF15 15000 KTF20 20000 KTF25 25000 KTF30 30000 KTF35 35000 KTF40 40000 KTF45 45000 KTF50 50000 KTF55 55000 KTF60 60000 KTF65 65000 KTF70 70000 KTF75 75000 KTF80 80000 KTF85 85000 KTF90 90000 KTF95 95000 KTF100 100000

Graph 2

Variation in Take-off sfc with Mach No.

0.30.320.340.360.380.4

0.420.440.460.480.5

0 0.05 0.1 0.15 0.2 0.25 0.3

Mach No.

sfc

(lb/h

r/lbf

)


Generic (KTF) High BPR Turbofan EnginesEngine Datum Take-off thrust (lbf)

Climb & Cruise Thrust (lbf)

KTF07 7500 KTF10 10000 KTF15 15000 KTF20 20000 KTF25 25000 KTF30 30000 KTF35 35000 KTF40 40000 KTF45 45000 KTF50 50000 KTF55 55000 KTF60 60000 KTF65 65000 KTF70 70000 KTF75 75000 KTF80 80000 KTF85 85000 KTF90 90000 KTF95 95000 KTF100 100000

Graph 3 ≅

Min cruise thrust

50% max

cruise thrust


Variation in Max. Climb/Max Cruise Thrust with Altitude & Mach No.

10

15

20

25

30

35

40

45

50

55

60

65

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9

Mach No.

T

hrus

t

(

%IS

A-S

LS T

ake-

Off

Thru

st

Sea-Level

10000ft

20000ft

30000ft

35000ft

40000ft

Graph 3

AssumesISA AIT.Hot day thrust would be lower


Generic (KTF) High BPR Turbofan EnginesEngine Datum Take-off thrust (lbf) Altitude Cruise sfc (lb/hr/lbf) KTF07 7500 KTF10 10000 KTF15 15000 KTF20 20000 KTF25 25000 KTF30 30000 KTF35 35000 KTF40 40000 KTF45 45000 KTF50 50000 KTF55 55000 KTF60 60000 KTF65 65000 KTF70 70000 KTF75 75000 KTF80 80000 KTF85 85000 KTF90 90000 KTF95 95000 KTF100 100000

Graph 4


Variation in Max. Climb/Max. Cruise sfcwith Altitude & Mach No.

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9

Mach No.

sfc

(lb/h

r/lbf

)

Sea-Level

10000ft

20000ft

30000ft

Graph 4

Data typical of engines in service in 2000. Assume 10% improvement for 2015


Flight Idle (Descent)

• Thrust ~ 4% max.take-off thrust

• Fuel burn ~ 4% max.take-off fuel burn


Propeller Powerplant• Relatively few new engines available• KTP family of engines available (See manufacturer for details)• Propeller selection & performance analysis required


Turboprop Powered Aircraft Weight & Power

Turboprop Powered Aircraft

Pax

Range(nm)

MTOW (tonne)

Total power

(ESHP)

Engines (1 option shown)

Cruise sfc

lb/hr/hp ATR-72 68 890 22.5 5500 2 PW127 ~0.473 Saab 2000 58 1549 22.8 8304 2 RR AE2100A 0.424 Bombardier DHC-8 70 1546 29.3 10142 2 PW150A 0.43 Alenia C-27 Spartan 31.8 9274 2 RR AE2100D2 0.400 C130-J Hercules 79.5 18548 4 RR AE2100D3 0.400 A400M 130.1 44000+ 4 TP400-D6 0.350


Generic (KTP) Turboprop EnginesEngine Datum

Take-off power (HP)

Diameter in

Length in

Weight lb

KTP1 1000 21.6 87.1 480 KTP2 2000 26.7 93.2 866 KTP3 3000 30.2 96.9 1223 KTP4 4000 33.0 99.7 1562 KTP5 5000 35.3 101.9 1889 KTP6 6000 37.3 103.7 2206 KTP7 7000 39.1 105.3 2516 KTP8 8000 40.7 106.7 2819 KTP9 9000 42.2 107.9 3116 KTP10 10000 43.6 109.0 3408 KTP11 11000 44.9 110.1 3696 KTP12 12000 46.1 111.0 3981 KTP13 13000 47.2 111.9 4261 KTP14 14000 48.3 112.7 4539

Use

Gra

ph 1

P fo

r al

titud

e &

AIT

eff

ects

A

ssum

e no

forw

ard

spee

d ef

fect

on

engi

ne p

ower


70

75

80

85

90

95

100

0 1000 2000 3000 4000 5000 6000

Altitude (feet)

Pow

er/P

ower

at S

ea-le

vel I

SA s

tatic

Take-off powerISATake-off powerISA+20

Graph 1P

Take-Off Power Variation with Altitude & AITTake Off Power Variation with Altitude & AIT


KTP Turboprop Engine sfc at Take-Off

• Assume constant value of 0.480 lb/hr/HP at all altitudes & AIT


Generic (KTP) Turboprop Engines

Engine Datum Take-off power (HP)

Climb & Cruise Power

KTP1 1000 KTP2 2000 KTP3 3000 KTP4 4000 KTP5 5000 KTP6 6000 KTP7 7000 KTP8 8000 KTP9 9000 KTP10 10000 KTP11 11000 KTP12 12000 KTP13 13000 KTP14 14000

Graph 3P ≅

Min cruise power

50% max cruise power


0102030405060708090

100

0 50 100 150 200 250 300 350

Forward Speed (knots)

Pow

er/IS

A-S

LS T

ake-

off P

ower

%

Graph 3P

Assumes ISA AIT.Hot day power would be lower

5000 ft10000 ft15000 ft20000 ft25000 ft30000ft

Variation in Max. Cruise Power with Altitude & Forward Speed


Variation in Cruise sfc with Altitude & Forward Speed

Variation in Cruise sfc with Altitude & Forward Speed

0.36

0.38

0.4

0.42

0.44

0.46

0.48

0.5

0.52

0.54

0.56

0 50 100 150 200 250 300 350 400

Foward Speed (knots)

sfc

(lb/h

r/HP)

Max cruise sfc 5000ftMax cruise sfc 10000ftMax cruise sfc15000ftMax cruise sfc20000ftMax cruise sfc 25000ftMax cruise sfc 30000ft

Graph 4P


Propeller Thrust vs Power RelationshipThrust = Engine power X ηprop

Aircraft forward speed

• Assume variable pitch propeller

• Typical max efficiency values for modern propellers = 80%

• Need to calculate propeller performance throughout flight envelope

• Static take-off thrust?

• ESDU 83001 Approximate Parametric Methods for Propeller Thrust


Propfans• Higher bypass ratios = improved efficiency• UHB ducted & unducted fan concept engines

– Demonstrated by GE on MD80

• Major problem – noise from supersonic tips of fan blades

Assume possible 20% improvement in fuel efficiency compared to year 2000 turbofans


Engine Selection Flow Chart

• Detailed aircraft drag calcs• Detailed engine thrust calcs• Take-off distance • AIT/altitude envelope• OEI • Climb rate• Fuel load• Range• Overall Weight

Are your engines suitable for aircraft?

No

Celebrate

Yes

Iterate

Select an engineslightly more powerful thanyou think youneed

Basic aircraft drag calculations• Estimate aircraft weight• Check thrust required

– For take-off at max.weight– For cruise at max. altitude

propulsion options for group design aircraft

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