copy of lecture 1006 - engine performance parameters

8/6/2019 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


powerthrust

!0L RfQm

Tu

!0

L


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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Flight SpeedRPM


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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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Engine Characteristics

Typical Turbofan Characteristics


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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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