pltmg prabumulih 18v34sg rev.3 pendahuluan
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GAS ENGINE POWER PLANT
Operation & Maintenance Course
18V34SG
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DAFTAR ISI
A. PendahuluanA. Ragam jenis mesin gas
B. Proses pada mesin gasC. Data utama mesin gas (Wartsila 18V34SG)
B. Komponen utamaA. Block bearing & oil sump
B. Head
C. Piston & Connection rod (conrod)
D. Liner
E. Crankshaft
F. Turbocharger
C. Sistem bahan bakar
D. Sistem udara / Charge air (CA) and exhaust gas (EG)
E. Sistem udara bertekanan / Compressed air system
F. Sistem pendingin / Cooling system
G. Sistem pelumas / Lubrication systemH. Prinsip operasi dan instrumentasi
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Pendahuluan
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PendahuluanKlasifikasi Piston engine
Piston
engine
Piston
engineOtto cycle
Spark ignition
Diesel cycle
Compressed ignition
Piston
engine
Four stroke
Two stroke
Four stroke
Two stroke
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Teknologi bahan bakar pada gas engine
GAS DIESEL GD - Diesel principle
- High pressure gas
- Real dual fuel
SPARK IGNITED SG - Otto principle
LEAN BURN - Low pressure gas
- Mono fuel
PILOT FUEL IGNITED DF - Otto principle
LEAN BURN - Low pressure gas
- Dual fuel
Wrtsil Gas Engine PortfolioPendahuluan- Gas Engine
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PendahuluanGas engine(lanjutan)
Proses Dual fuel Proses gas diesel
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PendahuluanAplikasi gas engine
1. Pembangkit listrik
2. Otomotif
3. Perkapalan
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PendahuluanSpesifikasi teknis
1. Bore
2. Stroke
3. Rpm
4. Mean effective pressure
5. Piston speed
6. Lower heating value (LHV)
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PendahuluanFuel technical specification
1. Lower heating value (LHV) : MJ/m3
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Gas Engine Process - Spark Gas Engine Otto Cycle
General Principle
The gas is mixed with the combustion air only in the intake channels inthe cylinder head close to the air inlet Valves.
Bahan bakar gas dicampur dengan udara di saluran intake dalamcylinder head, sebelum keluar melalui inlet valve.
This design ensures that only air is present in the charge air manifold,and thus the risk for explosions in the engines charge air intake system is
minimised.
Design ini menjamin hanya udara yang ada dalam intake manifold,sehingga meminimalkan resiko ledakan sistem intake manifilold
Since the gas valve can be timed independently of the inlet valve,scavenging of the cylinder is possible without risk that unburned gas isescaping directly from the inlet to the exhaust.
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AIR & GAS
INTAKE
EX
* ** *
IN
**
* * * *
*
***
** ****
COMPRESSION
OF AIR & GAS
EXIN
IGNITION
BY SPARK PLUG
EXIN
SG-engine operating principle (W34SG)
Wrtsil Gas Engine PortfolioGas Engine Process - Spark Gas Engine (SG)
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Gas Engine Process - Lean Burn Combustion
At higher loads a lean air-fuel mixture is also a requirement to avoiddetonation (knocking). On the other hand the misfiring limit is getting
closer, which means that the operating window is decreasing.
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Gas Engine Process - Lean Burn Combustion
0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.28
10
12
14
16
18
20
22
Air-fuel ratio
BMEP[bar]
Detonation
Misfiring
Operatingwindow
NOx(
g/kWh)
< 1 g/kWh
Therm
alefficiency(%)
46%
At higher loads a lean air-fuel mixture is also a requirement toavoid detonation (knocking). On the other hand the misfiring
limit is getting closer, which means that the operating window
is decreasing.
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Gas Engine Process - Cylinder Head
MAIN GAS ADMISSION VALVE
CHECK VALVE
SPARK PLUG
PRECHAMBER
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Gas Engine Process - Lean Burn Combustion
IN
EX
Too Rich:
Higher NOx
Pre-ignition
Knocking
Too Lean:
Slow Combustion
Incomplete Combustion
Bad Combustion Stability
EX
IN
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Gas Engine Process - Lean Burn Combustion
0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.28
10
12
14
16
18
20
22
Air-fuel ratio
BMEP[bar]
Detonation
Misfiring
Operatingwindow
NOx(
g/kWh)
< 1 g/kWh
Thermalefficiency(%)
46%
At higher loads a lean air-fuel mixture is also a requirement toavoid detonation (knocking). On the other hand the misfiring
limit is getting closer, which means that the operating window
is decreasing.
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Gas Engine Process - Lean Burn Combustion
Varying ambient conditions affects the air-fuel controlgiving the same engine performance
Air-fuel ratio
1.2 1.4 1.6 1.8 2 2.2
Detonation
M
isfiring
6
8
10
12
14
16
20
22
BMEP[bar]
Varying gas quality (methane
number) affects the output of the
engine giving as high output as
possible, but with a safe margin
to detonation.
Control Strategy at varying conditions
All the cylinders have the
optimal performance
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Gas Engine Process - Cylinder Control Principle
- kW- air/fuel- etc..
INPUT:- rpm
WECS
MAIN GAS
ADMISSION VALVE
PRECHAMBER
CONTROL VALVE
CHECK VALVE
COMBUSTION
SENSOR
Individual adjustment ofgas feed and ignition for
every cylinder
Every cylinder equippedwith a combustion
sensor
The gas feed is adjustedindividually to get the
correct air-fuel ratio in
every cylinder
In case of knocking onlythat specific cylinder is
adjusted
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Gas Engine Process - Lean Burn Combustion
Several input parametersused for wastegate controlgiving same engineperformance regardless ofchanging ambient conditions
Charge air temperature andpressure used for fine tuninggiving same engineperformance regardless ofchanging ambient conditions
Charge air pressure used forfast regulation needed atload transients
Air-Fuel Ratio Control
Air
Exhaust
WECS
PI
Exhaust wastegateLoad
Speed
T P
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Gas Explosions in a Lean Burn Engine
Gas explosions may occur in a lean burn engine Engine start is the most hazardous stage Preconditions:
correct concentration (3 - 17 vol% @ 400 oC)
ignition source (spark or like) Possible locations:
exhaust system ! air receiver
crankcase outside engine (leaks)
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Gas Explosions and fires in closed areas
Gas explosions and fires in closed areas may occur dueto gas leak Preconditions:
concentration (5 - 14 vol% @ 20oC) ignition source (spark or like)
Only a very small energy (1 mJ) is needed to ignite thegas
Almost any spark or flame may ignite the gas electric appliances, e.g. drilling machine, light
switches cigarette, matches even frictional electricity
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General Safety Concept
Active safety features (active controlled systemspreventing dangerous gas concentration in any location)
in engine control system (valves, control procedures
etc.)
in exhaust system (ventilation fan) Passive safety features (passive systems reacting to gas
explosion and preventing or minimizing damages)
in engine (explosion relief valves)
in exhaust system (explosion relief valves, ducting,dimensioning...)
in buildings (collapsing structures...)
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Gas Leak Test
During start: Automatic test of the gas regulating shut-off valves'
tightness for shut down and emergency situations.ompresse r
PressureTransmitter
1
2
3
VentVent
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Cylinder & Exhaust Manifold Ventilation
During start: Engine is rotated five revolutions to discharge any
unburned gas in the cylinders or in the exhaust
manifold. Gas admission and ignition are not active.
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Air Throttle Valve Position Control
During start and operation: Opens the air throttle valve to pre-programmed set value to ensure
proper air-fuel ratio.
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Start Fuel Limiting Function
During start: To prevent excessive gas admission and possible misfiring, the amount
of gas is limited during start and speed increase.
M
axgasadmission
duration
Engine speed
0 200 400 600 800
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Engine Speed Control
During start: Engine speed is checked during start. Too slow speed increase indicatesa possible misfiring of cylinder(s) and engine will be shut down to
prevent gas from entering the exhaust system.
0
100
200
300
400
500
600
700
800
00:00
00:02
00:04
00:06
00:08
00:10
00:12
00:14
00:16
00:18
00:20
00:22
00:24
00:26
00:28
00:30
00:32
00:34
00:36
00:38
00:40
00:42
00:44
00:46
00:48
00:50
00:52
00:54
00:56
00:58
01:00
Time [s]
Enginespeed[rp
Prelubricating of engine Gas leak test Start Ac cel erati on Syncronisation
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Exhaust Gas Temperature Monitoring
During start: If a specified minimum exhaust gas
temperature for any cylinder is not reached in
a specified time after nominal speed is
reached, the main gas duration of that cylinder
will be immediately increased. If the cylinder
still is under the specified minimum exhaust
gas temperature after a specified time, the
engine will be shut down.
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Redundant Speed Measuring SG
During operation: SG engine speed is measured with a redundant system consisting of a
rotary encoder and a speed pick-up. The encoder signal is used to
determine the gas admission and timing.
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Redundant Speed Measuring DF
During operation: DF engine speed is measured with a redundant system consisting of
two speed pick-ups and a TDC pick-up. The main speed pick-up and
TDC pick-up signals are used to determine the gas admission and
timing.
Speed pick-up
Speed pick-up
(redundant)
TDC pick-up
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Exhaust Gas Temperature Monitoring
During operation:
During engine operation the system monitors
the exhaust gas temperature of each cylinder.
If the temperature of any cylinder is lower orhigher than the specified limit a shutdown
occurs. Also, if the temperature deviates too
much from the exhaust gas average
temperature shutdown occurs.
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Idling Duration Limit
During operation:
To minimize the running time with poor
combustion during no load run and
consequently the gas gathering in the exhaust
system the time for idling is limited.
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Exhaust System Ventilation
After engine stop: To discharge any unburned gas in the exhaust system the system is
ventilated by a fan.
Explosion relief valve
Ventilation fan
Exhaust
Control
system
Silencer
Exhaust gas boilerfsFlow switch
Ven tilat ion valve
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ExhaustSystem Design
Upward slopes to avoid gas pockets wheregas might get trapped
Ventilation system
Explosion relief valves, ducted outdoors and
opening at an excess pressure of 0.5 bar
Sustain an under pressure of 0.3 bar without
collapse
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Gas Regulating Unit The shut-off valves and vent valves operate fail safe.
Safety shut-off valve (optional) is closed, if gas pressure
is too high at engine. It can be reopened only manually.
VentVent Vent
Ball valve Filter
Pilot operated
Downstream pipeElectro-pneumatic
Main Pressure Regulator
shut-off valves
Control Air Compressed Air
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Start Blocking
Shutdown or emergency stop signal not reset Exhaust system ventilation not finished
Start air pressure below the start block limit
Main and prechamber gas pressures below start
block limit
Low or high gas temperature
Safety valve in the gas regulating unit is tripped
Turning gear engaged
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Alarms
Sensor failure Low control air pressure
Low exhaust gas temperature
High exhaust gas temperature after anycylinder
High exhaust gas temperature deviation
between cylinders Start attempt failed
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Shutdowns
Start failure High charge air temperature
High exhaust gas temperature after anycylinder
Low exhaust gas temperature after anycylinder
High exhaust gas temperature deviation
between cylinders High deviation of main gas pressure
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Emergency stops
Emergency stop push button, on engine or external,pressed
Rotary encoder sensor failure
Overspeed from rotary encoder
Overspeed from speed pick-up Speed deviation between rotary encoder and engine
speed pick-up
Deviation in number of encoder pulses per revolution
Degassing failure in auto stop mode. Activated if the gaspressure is still present after the shutdown control task
has disabled the inlet gas pressure control