Post on 11-Jan-2017
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TEKNOLOGI OTOMOTIF DASAR
(2 sks TEORI)
* Motor 2 & 4 Tak (Diagram P-V & Diagram Kerja)
BENI SETYA NUGRAHA, M.Pd.
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Topik Minggu LaluProses Pembakaran (Normal, Knocking,
Detonasi)Engine Operating CycleSiklus 2 & 4 Tak (Pendahuluan)
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Siklus Kerja Motor Bensin 4 Tak
(Four stroke Spark Ignition (SI) Engine)
Stroke 1: Fuel-air mixture introduced into cylinder through intake valve
Stroke 2: Fuel-air mixture compressed
Stroke 3: Combustion (roughly constant volume) occurs and product gases expand doing work
Stroke 4: Product gases pushed out of the cylinder through the exhaust valve
Compression
Stroke
Power
Stroke
Exhaust
Stroke
A
I
R
Combustion
Products
Ignition
Intake
Stroke
FUEL
Fuel/Air
Mixture
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Animasi Motor 4 Tak
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Diagram PV (Pressure-Volume Graph) 4-stroke SI engine
One power stroke for every two crank shaft revolutions
1 atm
Spark
TC
Cylinder volume
BC
Pressure
Exhaust valve
opens
Intake valve
closes
Exhaust
valve
closes
Intake
valve
opens
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IVO - intake valve opens, IVC – intake valve closes
EVO – exhaust valve opens, EVC – exhaust valve opens
Xb – burned gas mole fraction
Motored Four-Stroke Engine
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Pressure (bar)
100
Intake Exhaust
TC
BC
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IVO - intake valve opens, IVC – intake valve closes
EVO – exhaust valve opens, EVC – exhaust valve opens
Xb – burned gas mole fraction
Four-Stroke SI Engine
Valve overlap
Exhaust gas
residual
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Pressure (bar)
100
Intake Exhaust
OVERLAPPING
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Siklus Kerja Motor Bensin 2 Tak
(Modern Two-Stroke Spark Ignition Engine)
Stroke 1: Fuel-air mixture is introduced into the cylinder and is then compressed, combustion
initiated at the end of the stroke
Stroke 2: Combustion products expand doing work and then exhausted
* Power delivered to the crankshaft on every revolution
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Two Stroke Spark Ignition Engine
Intake (“Scavenging”)
Compression Ignition
ExhaustExpansion
Fuel-air-oil
mixture
Fuel-air-oil
mixture
Crank
shaft
Reed
valve
Exhaust
Port*
Transfer
Port*
*No valves and
thus no camshaft
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Animasi Motor 2 Tak
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EPO – exhaust port open
EPC – exhaust port closed
IPO – intake port open
IPC – intake port closed
Two-Stroke CI Engine
scavenging
Ai
Ae
Intake area (Ai)
Exhaust area (Ae)
PiPe
Exhaust Press (Pe)
Intake Press (Pi)
Cylinder Press (P)
110 CA
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Cross Loop Uniflow
Pembilasan pada Motor 2 Tak
(Scavenging in Two-Stroke Engine)
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Kelebihan Motor 2 Tak:
Power to weight ratio (PWR) lebih besar dibandingkan motor 4 tak
karena menghasilkan tenaga setiap putaran poros engkol.
Konstruksi sederhana, hanya ada saluran (ports) - tidak perlu mekanisme katup yang rumit
Perawatan lebih mudah
Banyak diaplikasikan pada motor kecil : sepeda motor, motor tempel, kompressor, pemotong rumput, gergaji mesin (chain
saw), .............
Kekurangan Motor 2 Tak:
Pembilasan kurang sempurna (tidak selesai/terlalu bersih) Emisi tinggi, bahan bakar tidak ekonomis
Proses pembakaran tidak bersih karena membakar oli Emisi tinggi
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Single Cylinder Engine
Motor 2 Tak menghasilkan Power (Langkah Usaha) setiap 1 putaran poros engkol (360 CA).
Motor 4 Tak menghasilkan Power (Langkah Usaha) setiap 2 putaran poros engkol (720 CA).
Interval torsi yang dihasilkan motor cukup jauh, menyebabkan getaran pada mesin.
Dimensi mesin sangat kompak sehingga motor 1 silinder umumnya diaplikasikan pada kendaraan kecil .
180 CA
(BDC)
0 CA
(TDC)
720 CA
(TDC)
540 CA
(BDC)
360 CA
(TDC)
4-stroke
2-stroke
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Multi-cylinder Engines
Multi-cylinder engines digunakan untuk mendistribusikan volume silinder motor pada beberapa silinder.
Keuntungannya memperpendek interval torsi yang dihasilkan motor, sehingga mengurangi getaran dan menghasilkan karakter
torsi yang dihasilkan lebih rata/halus.
Konfigurasi yang umum digunakan:
a. Inline b. V c. Boxer
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DIAGRAM PROSES KERJAMenghitung:Panjang Proses (=Langkah): Jumlah Derajat Putaran 1 Siklus
Jml Proses (=Langkah)Jarak Proses (=Langkah): Jumlah Derajat Putaran 1 Siklus
Jml Silinder MotorContoh:Motor 4 Tak 4 Silinder FO (Firing Order): 1-3-4-2
Gambarlah:Diagram EngkolDiagram Proses Kerja
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DIAGRAM PROSES KERJAPanjang Proses (=Langkah) = 2 x 360 CA
4= 720 CA 4= 180 CA
Jarak Proses (=Langkah) = 2 x 360 CA4= 720 CA 4= 180 CA
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DIAGRAM PROSES KERJAFO: 1-3-4-2Diagram Engkol:
Cyl: 1 , 4
CA: 0 , 720
(TDC)
Cyl: 2 , 3
CA: 180 , 540
(BDC)
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DIAGRAM PROSES KERJA
CYL/CA 0 180 360 540 720
1 INTAKE COMPRESSION POWER EXHAUST
2 COMPRESSION POWER EXHAUST INTAKE
3 EXHAUST INTAKE COMPRESSION POWER
4 POWER EXHAUST INTAKE COMPRESSION
1
2
3
4
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TUGASGambarlah Diagram Engkol & Diagram
Proses KerjaMotor 4 Tak 6 Silinder, FO: 1-5-3-6-2-4Motor 4 Tak 6 Silinder, FO: 1-3-5-6-4-2
Lengkap dengan perhitungannya!Kumpulkan pada TM y.a.d!
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Minggu depan belajar durasi katup & panjang langkah efektif
See U Next Week,
Wassalaam...