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Aero Group Design – Dr. K.J. Hart - UH
Aero Group Design ProjectAircraft Propulsion
Aero Group Design – Dr. K.J. Hart - UH
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!
Aero Group Design – Dr. K.J. Hart - UH
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.
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
Take-Off Thrust RequiredConsider:• Aerodynamic lift required • Take-off speed• Aerodynamic drag• Ground friction• Length of runway• Runway altitude • Engine thrust vs aircraft speed
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
)
Aero Group Design – Dr. K.J. Hart - UH
Maximum Engine Thrust vs Pax
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
)
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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)
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
)
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
Flight Idle (Descent)
• Thrust ~ 4% max.take-off thrust
• Fuel burn ~ 4% max.take-off fuel burn
Aero Group Design – Dr. K.J. Hart - UH
Propeller Powerplant• Relatively few new engines available• KTP family of engines available (See manufacturer for details)• Propeller selection & performance analysis required
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
KTP Turboprop Engine sfc at Take-Off
• Assume constant value of 0.480 lb/hr/HP at all altitudes & AIT
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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
Aero Group Design – Dr. K.J. Hart - UH
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