Copy of Lecture 1006 - Engine Performance Parameters
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Transcript of Copy of Lecture 1006 - Engine Performance Parameters
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Engine Performance Parameters
Dr. Firman Hartono
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Engine Performance Parameters
Setelah mengikuti kuliah ini mahasiswa dapat:
Menyebutkan parameter-parameter performa mesin
Menjelaskan perbedaan static thrust, gross thrust dan net thrust
Menjelaskan pengaruh kecepatan, tekanan, temperatur dan
ketinggian pada thrust Menjelaskan matching aircraft - engine
Referensi:
P. Hill, and C. Peterson, Mechanics and Thermodynamics of
Propulsion, Addison-Wesley Publishing Company, New York, 1992
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Principle of Thrust
Thrust is the force which moves any aircraft through the air.
Different propulsion systems develop thrust in differentways, but all thrust is generated through some applicationofNewton's third law of motion (for every action there is anequal and opposite reaction).
In any propulsion system, a working fluid is accelerated bythe system and the reaction to this acceleration produces aforce on the system (Newtons second law).
Thrust
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The Thrust Equation
General thrust equation
can be derived from
continuity and momentum
laws without the need for
detailed consideration of
the internal mechanismsof particular engines
? A eaeea Appuufm ! 1T
For the system described above:
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Gross, Net and Specific Thrust
Gross Thrust Thrust produced when the engine is not in motion
eaum!Fg
Net Thrust Thrust produced when the aircraft is flying
Nozzle unchoked ? Auuea ! Fn
Nozzle choked ? A eaeea ppuu ! Fn
in the equations,f is assumed to be much less than one
Specific Thrust Net thrust per unit of inlet air mass flow rate
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Force Distribution
thrust exist when total internal force act forward
When the internal mechanism of the engine is considered, onecan calculate the engines force distribution
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Thrust / Shaft Horse Power
THP=Thrust x Aircraft Speed x conversion factor (hp)
in International System
v!
hp
W
s
m
SpeedAircraftNThrustTHP
745
for turboprop, the engines available power rated inshaft horse powerorequivalence shaft horse power
hpSpeedAircraftThrustJetSHPESHP v!
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Specific Fuel Consumption
s.f.c = the amount of fuel consumed per unit thrust or power
T
msfc
f
!
For turboprop and turboshaft engine
shaft
f
P
mbsfc
!
If Pshaft is replaced by Peqiv = Pshaft + Thrust x A/c Speed, bsfc becomes
ebsfc (equivalence brake specific fuel consumption)
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Engine Performance
Propulsion efficiency
energykineticpropellantofproductionofrate
powerthrustp !L or
!
221
22uu
fm
Tu
ea
p
L
For turboprop
po ershaft
po erthrustpropeller
p !Lor
s
pr
p
uT!L
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ratenconsumptioenergytotal
energykineticpropellantofproductionofrateth !L
Rf
ea
thQm
uufm
!22
1
22
L
ratenconsumptioenergytotal po ershaft
th !L
f
sth
m!L
Engine Performance
Thermal efficiency
For turboprop
or
or
ratenconsumptioenergytotal
powerthrust
!0L RfQm
Tu
!0
L
ratenconsumptioenergytotal
po erthrustpropeller!
0L
Rf
pr
Qm
uT
!
0L
or thpLLL !0
Total efficiency
For turboprop
or
or
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Factors Affecting Thrust
Design or Operating factors
Revolution per minute (rpm)
Exhaust nozzle area
Rate of fuel consumption
Bleed air Turbine Inlet Temperature
Water injection
Non-design factors
Flight speed Ambient temperature
Ambient pressure
Humidity
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Factors Affecting Thrust
Flight SpeedRPM
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Factors Affecting Thrust
Air TemperatureAir Pressure
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Factors Affecting Thrust The temperature of the air drops with
an increase of altitude from itsstandard sea level condition, so does
the pressure
Temperature drops increases density
Pressure drops decreases density
The decrease in density caused by thedropping pressure more than
overcomes the increase cause by the
lowering temperature and the air
density decreases as altitude
increases
The decrease in density drops thethrust
After 10,800 m, the air temperature no
longer decreases and the thrust drops
more rapidly
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Aircraft Engine Matching
Aircraft Characteristics
Lift and Drag
since
thenAt cruise:
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Aircraft Engine Matching
Engine Characteristics
Typical Turbofan Characteristics
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Aircraft Engine Matching
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Aircraft Range
RfQm
Tu
!
0L
Range is directly proportional to: Engine overall efficiency
Aircraft aerodynamic efficiency
Energy contained in fuel
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Ex.
Berikut performa turbojet hasil pengukuran static thrust pada ketinggian sea level
(biru):
ir mass flo
vs Engine
0
0.1
0.2
0.3
0.4
0.5
0.6
0 20 00 0 40 00 0 6 00 00 8 00 00 10 00 00 12 00 00
Engine
irmassflo
(g
s)
Exper
ent Ref [8]
hrust vs Engine
0
5
10
15
20
25
0 20 00 0 4 00 00 6 00 00 80 00 0 100 00 0 12 00 00
Engine
hrust
(Kg)
Exper
ent Ref [4]
Fuel flo
vs Engine
0.0000
2.0000
4.0000
6.0000
8.0000
10.0000
12.0000
14.0000
0 2 00 00 4 00 00 6 00 00 8 00 00 10 00 00 12 00 00
Engine
Fue
lflo
(g
s)
Exper
ent Ref [4]
ada putaran maksimum 108000 rpm, berapakah thrust? ada thrust tsb, jika
tidak terjadi choking pada nosel, berapakah kecepatan gas keluar exhaust?
Berapakah s.f.c? Berapakah efisiensi thermal, efisiensi propulsive dan efisiensi
total?
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Questions?