PLTMG Prabumulih 18V34SG Rev.3 Pendahuluan

5/21/2018 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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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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IN

EX

Too Rich:

Higher NOx

Pre-ignition

Knocking

Too Lean:

Slow Combustion

Incomplete Combustion

Bad Combustion Stability

EX

IN


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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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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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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

PLTMG Prabumulih 18V34SG Rev.3 Pendahuluan

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