HARUKO

NAMA : YUSAK MARBUN
NIM : 0811 0307 0009
MATA KULIA: MOTOR PENGGERAK KAPAL

GAS TURBINE
A gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. (Gas turbine may also refer to just the turbine element.) Energy is added to the gas stream in the combustor, where fuel is mixed with air and ignited. In the high pressure environment of the combustor, combustion of the fuel increases the temperature. The products of the combustion are forced into the turbine section. There, the high velocity and volume of the gas flow is directed through a nozzle over the turbine's blades, spinning the turbine which powers the compressor and, for some turbines, drives their mechanical output. The energy given up to the turbine comes from the reduction in the temperature of the exhaust gas. Energy is extracted in the form of shaft power, compressed air and thrust, in any combination, and used to power aircraft, trains, ships, generators, and even tanks.
TYPES OF GAS TURBINES
 Aeroderivatives and jet engines
 Amateur gas turbines
 Auxiliary power units
 Industrial gas turbines for electrical generation
o Compressed air energy storage
 Turboshaft engines
 Radial gas turbines
 Scale jet engines
 Microturbines
COMPONENTS OF GAS TURBINE
 compressor
 compressor Sentrifugal
 compressor Aksial
 space
 Turbine
 Gas turbine engine

ADVANTAGES AND DISADVANTAGES OF GAS TURBINE ENGINES
ADVANTAGES OF GAS TURBINE ENGINES
• Very high power-to-weight ratio, compared to reciprocating engines;
• Smaller than most reciprocating engines of the same power rating.
• Moves in one direction only, with far less vibration than a reciprocating engine.
• Fewer moving parts than reciprocating engines.
• Low operating pressures.
• High operation speeds.
• Low lubricating oil cost and consumption.
DISADVANTAGES OF GAS TURBINE ENGINES
 Cost
 Less efficient than reciprocating engines at idle
 Longer startup than reciprocating engines
 Less responsive to changes in power demand compared to reciprocating engines

STEAM TURBINE
The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible . A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884. It has almost completely replaced the reciprocating piston steam engine primarily because of its greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 80% of all electricity generation in the world is by use of steam turbines.
TYPES OF STEAM TURBINES
 Steam Supply and Exhaust Conditions
 Casing or Shaft Arrangements
ADVANTAGES AND DISADVANTAGES OF STEAM TURBINE ENGINES
ADVANTAGES OF STEAM TURBINE ENGINES
 High efficiency at full load
 Mechanical simplicity and hence potential reliability.
 Conventional reciprocating steam locomotives give a varying torque through the cycle, resembling a sine characteristic. This makes wheelslip at starting much more likely.
 Conventional steam locomotives have substantial reciprocating masses such as connecting rods and valve gear. This creates fore-and-aft forces that cannot be completely balanced without unacceptably increasing the up-and-down forces on the track.
DISADVANTAGES OF STEAM TURBINE ENGINES
 High efficiency is only obtained at full-load. Naval vessels very often had cruising turbines which could be run at full output while the main turbines were shut down.
 High efficiency is only obtained when the turbine exhausts into a near-vacuum, generated by a condenser. These are very large pieces of equipment to carry around.
 Turbines cannot run in reverse. Ships carried separate turbines solely for reversing, and locomotives had to do the same (see the Turbomotive for an example)
COMPONENTS OF STEAM ENGINES
 Heat source
 Boilers
 Motor units
o Simple expansion
o Oscillating cylinder steam engines
o Compounding engines
o Multiple expansion engines
o Uniflow (or unaflow) engine
o Turbine engines
o Rotary steam engines
 Cold sink
 Monitoring equipment.

DIESEL ENGINE
A diesel engine (also known as a compression ignition engine and sometimes capitalized as Diesel engine) is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to spark ignition engines such as a petrol engine (known as a gasoline engine in North America) or gas engine (using a gaseous fuel, not gasoline), which uses a spark plug to ignite an air-fuel mixture. Both diesel engines and spark ignition engines are modelled by the Otto cycle. The diesel cycle (a thermodynamic model slightly different from the Otto cycle) is not to be confused with the diesel engine, both of which were developed by Rudolph Diesel and named after him. The diesel engine has the highest thermal efficiency of any regular internal or external combustion engine due to its very high compression ratio. Low-speed diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) often have a thermal efficiency which exceeds 50 percent. Diesel engines are manufactured in two stroke and four stroke versions. They were originally used as a more efficient replacement for stationary steam engines.
HOW DIESEL ENGINES WORK
 Early fuel injection systems
 Fuel delivery
 Major advantages
 Mechanical and electronic injection
 Indirect injection
 Direct injection
 Unit direct injection
 Common rail direct injection
 Cold weather
o Starting
o Gelling
TYPES OF DIESEL ENGINE
 Early
 Modern
 Gas generator
ADVANTAGES AND DISADVANTAGES OF DIESEL ENGINE
ADVANTAGES OF DIESEL ENGINE
 Modern diesel engines have overcome disadvantages of earlier models of higher noise and maintenance costs. They are now quiet and require less maintenance as compared with gas engines of similar size.
 They are more rugged and reliable.
 There is no sparking as the fuel auto-ignites. The absence of spark plugs or spark wires lowers maintenance costs.
 Fuel cost per KiloWatt produced is thirty to fifty percent lower than that of gas engines.
 An 1800 rpm water cooled diesel unit operates for 12,000 to 30,000 hours before any major maintenance is necessary. An 1800 rpm water cooled gas unit usually operates for 6000-10,000 hours before it needs servicing.
 Gas units burn hotter than diesel units, and hence they have a significantly shorter life compared with diesel units.
DISADVANTAGES OF ENGINE DIESEL
 They are harder to start in cold weather.
 They cost more to purchase up front.
 Many local repair shops do not have the service personnel or parts for diesel engines.
 They cost more to repair than a comparable gasoline engine.
 They can go farther than your bladder can on a tank of fuel.
COMPONENTS OF DIESEL ENGINE
 Injector CRI 2
 Injector CRI 3
 High pressure fuel pump CP3 /CP4
 Pressure control valve DRV
 Pressure limiting valve DBV
 Pressure sensor RDS
 Rails.

Karakteristik propeler meliputi:

- Diameter; pada umumnya, semakin besar diameter dan semakin rendah putarannya maka efisiensi propulsinya semakin tinggi
- Putaran (Rpm); pemilihan/penentuan putaran merupakan kompromi antara efisiensi, berat, kebutuhan ruang permesinan, serta kebutuhan biaya (initial cost)
- Hub; ukurannya sebaiknya tidak terlalu besar
- Jumlah daun; propeler merupakan sumber getaran yang potensial berkaitan dengan aspek hidrodinamik badan kapal, khususnya buritan; gangguan getaran akan menurun dengan semakin besarnya jumlah daun; pada mulanya propeler dibuat dengan tiga daun, dewasa ini jumlah daun ada yang mencapai tujuh
- Sudut pitch; berpengaruh terhadap daya dorong yang dihasilkan
- Blade skew; daun propeler tidak semua berbentuk skew; disebut skew bila bentuknya tidak simetrik terhadap garis referensi radial pada bidang propeler, lihat gambar 6-18; gambar 6-19 menunjukkan kemiringan (rake) posisi daun terhadap sumbu poros
- Ketebalan daun (thickness); sebaiknya ketebalannya kecil, namun ada batas ketebalan minimum yang diijinkan, berkaitan dengan tegangan (stress) yang ditimbulkan
- Berat propeler; merupakan beban yang harus diperhitungkan dan harus di sangga

Propeler

Propeler berfungsi merubah daya yang dihasilkan oleh motor induk dan selanjutnya ditransmisikan melalui poros menjadi daya dorong (thrust). Propeler dibedakan atas Fixed Pitch Propeller (FPP) lihat gambar 6-18, Controllable Pitch Propeller (CPP), Propeller in Nozzle, Contra-rotating propeller, dan Vertical-axis propeller.


Gambar 6-18 menunjukkan suatu contoh dari konstruksi propeler tipe FPP dengan tiga buah daun. Gambar 6-19 menunjukkan definisi dari rake dan skew, serta penampang (section) dari daun baling-baling.


- Propeler dengan sudut pitch tetap
Disebut juga Fixed Pitch Propeller, FPP); terdiri dari sejumlah daun, dua sampai tujuh buah, yang terpasang pada pangkal (hub atau boss).

- Conventional fixed-pitch propeller; dibuat dengan cara pengecoran hub dan daun-daun nya menjadi satu (single casting); konstruksinya sederhana serta harganya (initial cost) relatif murah
- Detachable-blade propeller; dibuat dengan cara terpisah antara hub dan daun-daunnya; daun-daunnya dipasang dengan ikatan baut pada hub; keuntungannya dalam segi perbaikan, misalnya hanya memerlukan perbaikan satu daun tertentu, tidak perlu mengganti dengan satu unit propeler lengkap

- Propeler dengan sudut pitch yang dapat diatur
Disebut juga Controllable Pitch Propeller (CPP), atau disebut juga Variable Pitch Propeller (VPP) atau Controllable and Reversible Pitch Propeller (CRP); lihat gambar 6-20 dan 6-21.

Beberapa keuntungannya sebagai berikut:

- mampu dioperasikan dalam kodisi yang sangat bervariasi, termasuk perubahan arah daya dorong (gerakan kapal maju atau mundur), secara cepat atau sering, tanpa perlu membalik putaran poros; sesuai untuk kapal tunda dan trawler
- pada sistem yang memakai motor induk berupa diesel putaran tinggi dan turbin gas sangat sesuai karena memungkinkan penyesuaian (matching) putaran dan daya antara motor induk dengan propeler yang sangat fleksibel

CPP dilengkapi dengan mekanisme pengaturan posisi atau sudut pitch daun-daunnya, pada umumnya berupa sistem elektro-hidrolik; sistemnya rumit, harga dan pemeliharaanya mahal

Propeller in nozzle

Dirancang dengan cara menempatkan propeler di dalam sebuah tabung berupa nozzle, dengan demikian maka aliran fluida akan lebih terarah ke propeler sehingga efisiensinya menjadi lebih tinggi; ada dua jenis propeler sebagai berikut:
- Pump jet; propeler ditempatkan di dalam nosel yang relatif panjang, dan dilengkapi dengan sudu pengarah yang tetap (guide vanes); keuntungannya adalah kebisingan (noise) yang relatif kecil
- Kort nozzle; propeler ditempatkan di dalam nosel yang relatif pendek (rasio panjang dibanding diameter antara 0,5 sampai 0,8); banyak digunakan pada kapal tunda; gambar 6-25.

- Contrarotating propeller
- Terdiri dari dua buah propeler yang disusun/dipasang secara tandem (yang satu ditempatkan di belakang yang lainnya); lihat gambar 6-26.
- Masing-masing propeller dipasang pada sebuah poros dan terpasang secara coaxial (poros yang satu ditempatkan di dalam poros yang lainnya, jadi poros yang diluar merupakan poros berongga);
- Arah putarannya berlawanan, sehingga memerlukan roda gigi pembalik putaran;
- Diameter propeler menjadi lebih kecil namun efisiensinya relatif tinggi;
- Pada putaran yang tinggi, propeler yang ditempatkan di depan sangat mempengaruhi kavitasi pada propeler yang ditempatkan di belakangnya (oleh karena itu tidak disarankan untuk putaran tinggi)
- Vertical axis propeller

- Termasuk propeler yang belum lama dikembangkan
- Terdapat dua tipe yang diberi nama menurut penciptanya, yakni Kirsten-Boeing dan Voith-Schneider
- Memiliki empat atau lebih daun yang terpasang pada piringan (disk) dengan poros vertical
- Arah daya dorong (thrust) meliputi maju, mundur, maupun arah kesamping. Dalam hal ini propeler dapat berfungsi sebagai kemudi, dengan demikian tidak diperlukan daun kemudi (rudder) maupun mekanisme pembalik arah putaran poros

The steps involved here are:
1. Intake stroke: Air and vaporized fuel are drawn in.
2. Compression stroke: Fuel vapor and air are compressed and ignited.
3. Combustion stroke: Fuel combusts and piston is pushed downwards.
4. Exhaust stroke: Exhaust is driven out. During the 1st, 2nd, and 4th stroke the piston is relying on power and the momentum generated by the other pistons. In that case, a four cylinder engine would be less powerful than a six or eight cylinder engine.
Two-stroke The steps involved here are:
1. Intake and exhaust occur at bottom dead center. Some form of pressure is needed, either crankcase compression or super-charging.
2. Compression stroke: Fuel-air mix compressed and ignited. In case of Diesel: Air compressed, fuel injected and self ignited
3. Power stroke: piston is pushed downwards by the hot exhaust gases.