The report included most of the vital information regarding the Marine diesel engine: the 2 stroke and the 4 stroke, etc that may be helpful to the students.

1. FIRST REPORT IN PRELIM 2ND
SEMESTER
BY: JAY MARK B. ANUTA
DEEP3B BSMT
REPORT IN MARINE
POWER

2. OBJECTIVES
• Describe the 2-stroke diesel engine cycle
• Describe the 4-stroke diesel engine cycle
• Describe the operating principle of marine diesel
engine
• Describe the advantages and disadvantages of a
slow-speed diesel engine
• Explain the cause of scavenge fires and how they
are dealt with
• Describe the methods Asupercharging
• Describe the fuel oil system from bunker tank to
injection
• Describe the lubrication system

3. I. THE 2-STROKE DIESEL CYCLE
• A two-stroke engine cycle undergoes different processes
in order to served its functions, these processes are:
1. Intake
2. Crankcase compression
3. Transfer exhaust
4. Compression
5. Power

4. INTAKE
The fuel/air mixture is first
drawn into the crankcase
by the vacuum that is
created during the upward
stroke of the piston. The
illustrated engine features a
poppet intake valve;
however, many engines
use a rotary value
incorporated into the
crankshaft.

5. CRANKCASE COMPRESSION
During the downward
stroke, the poppet valve
is forced closed by the
increased crankcase
pressure. The fuel
mixture is then
compressed in the
crankcase during the
remainder of the stroke.

6. TRANSFER EXHAUST
Toward the end of the stroke, the
piston exposes the intake port,
allowing the compressed fuel/air
mixture in the crankcase to
escape around the piston into the
main cylinder. This expels the
exhaust gasses out the exhaust
port, usually located on the
opposite side of the cylinder.
Unfortunately, some of the fresh
fuel mixture is usually expelled as
well.

7. COMPRESSION
The piston then rises,
driven by flywheel
momentum, and
compresses the fuel
mixture. (At the same
time, another intake
stroke is happening
beneath the piston).

8. POWER
At the top of the stroke, the
spark plug ignites the fuel
mixture. The burning fuel
expands, driving the piston
downward, to complete the
cycle. (At the same time,
another crankcase
compression stroke is
happening beneath the
piston.)

9. Video Presentation

10. II. THE 4-STROKE DIESEL CYCLE
• A four-stroke engine cycle undergoes different processes
in order to served its functions, these processes are:
1. Intake
2. Compression
3. Power
4. Exhaust

11. INTAKE
During the intake stroke, the
piston moves downward, drawing
a fresh charge of vaporized
fuel/air mixture. The illustrated
engine features a poppet intake
valve which is drawn open by the
vacuum produced by the intake
stroke. Some early engines
worked this way; however, most
modern engines incorporate an
extra cam/lifter arrangement as
seen on the exhaust valve. The
exhaust valve is held shut by a
spring (not illustrated here).

12. COMPRESSION
As the piston rises, the
poppet valve is forced
shut by the increased
cylinder pressure.
Flywheel momentum
drives the piston
upward, compressing
the fuel/air mixture.

13. POWER
At the top of the
compression stroke, the
spark plug fires, igniting
the compressed fuel. As
the fuel burns it
expands, driving the
piston downward.

14. EXHAUST
At the bottom of the power
stroke, the exhaust valve is
opened by the cam/lifter
mechanism. The upward
stroke of the piston drives
the exhausted fuel out of
the cylinder.

15. Video Presentation

16. III. OPERATING PRINCIPLES OF MARINE
DIESEL PROPULSION
The Diesel Engine
• One of the places where diesel engines play an
important role is the shipping industry. Diesel engines
are known by the name of compression ignition engines
due to technical reasons. Rudolf Diesel (German
Engineer), the brain behind the invention of the diesel
engine.

17. Diesel Marine Engines
• Marine engines are those which are used in marine
vehicles namely boats, ships, submarines and so forth.
Both 2-stroke as well as 4-stroke engines are used in the
marine industry. The engines used for the
main propulsion or turning the propeller/s of the normal
ships are usually slow speed 2-stroke engines while
those used for providing auxiliary power are usually 4-
stroke high speed diesel engines.

18. IV. THE ADVANTAGES AND
DISADVANTAGES OF SLOW-SPEED
DIESEL ENGINE
Advantages
• Inexpensive fuel cost
Disadvantages
• Viscos fuel consumption

19. V. THE CAUSE OF SCAVENGE FIRES
AND HOW TO DEAL WITH IT
The Purpose of Scavenging
Scavenging is the removal of
exhaust gases by blowing in fresh air;
thus, efficient scavenging is essential to
ensure a sufficient supply of fresh air
for combustion.

20. THE CAUSE OF SCAVENGE FIRE
• Cylinder oil can collect in the scavenge space of an
engine. Unburned fuel and carbon may also be blown
into the scavenge space as a result of defective piston
rings, faulty timing, a defective injector, etc.
A build-up of this flammable mixture presents a danger
as a blow past of hot gases from the cylinder may ignite
the mixture, and cause a scavenge fire. A loss of engine
power will result, with high exhaust temperatures at the
affected cylinders. The affected turbo-chargers may
surge and sparks will be seen at the scavenge drains.

21. HOW TO DEAL WITH IT?
• Once a fire is detected the engine should be slowed
down, fuel shut off from the affected cylinders and
cylinder lubrication increased. All the scavenge drains
should be closed. A small fire will quickly burn out, but
where the fire persists the engine must be stopped. A fire
extinguishing medium should then be injected through
the fittings provided in the scavenge trunking. On no
account should the trunking be opened up.

22. STEPS IN DEALING SCAVENGE FIRES
Scavenge fires are extremely dangerous and it is
important that quick and effective action is taken to rectify
the situation.
1. Engine revolutions must immediately be reduced to a
minimum.
2. If possible the fuel is to be cut off from the cylinder unit
concerned.
3. If more than one cylinder is involved then it will be more
effective if the engine is stopped and the turning gear
engaged and continuous turning commenced.

23. CONTINUED……..
1. The cylinder lubricators are then to be advanced to
the maximum setting on the effected cylinders.
2. Turbocharger air intakes are to be blanked off.
3. Scavenge space relief valves where possible can
be secured, and isolating flaps shut.
4. All external scavenge space surfaces must be
carefully scrutinised for outbreaks of fire and
strategic cooling applied as necessary.
5. There are various types of scavenge space fire
extinguishing systems in use i.e. steam, dry
powder, and CO2.

24. VI. THE METHODS OF SUPERCHARGING
Video Presentation

25. VII. THE FUEL SYSTEM FROM BUNKER
TANK TO INJECTION
Video Presentation

26. VIII. THE LUBRICATION SYSTEM
“Lubricating oil for a marine
diesel engine achieves two
objectives; it must cool and
lubricate.”

27. FUNCTION OF LUBRICATION
The lubrication system of an engine
provides a supply of lubricating oil to the
various moving parts in the engine. Its main
function is to enable the formation of a film
of oil between the moving parts, which
reduces friction and wear. The lubricating oil
is also used as a cleaner and in some
engines as a coolant

28. LUBRICATING OIL SYSTEM
Lubricating oil for an engine is stored in the bottom of the
crankcase, known as the sump, or in a drain tank located
beneath the engine . The oil is drawn from this tank
through a strainer, one of a pair of pumps, into one of a
pair of fine filters. It is then passed through a cooler before
entering the engine and being distributed to the various
branch pipes.
The branch pipe for a particular cylinder may feed the
main bearing, for instance. Some of this oil will pass along
a drilled passage in the crankshaft to the bottom end
bearing and then up a drilled passage in the connecting
rod to the gudgeon pin or crosshead bearing.

30. Large slow-speed diesel engines are
provided with a separate lubrication
system for the cylinder liners. Oil is
injected between the liner and the piston
by mechanical lubricators which supply
their individual cylinder, A special type of
oil is used which is not recovered. As well
as lubricating, it assists in forming a gas
seal and contains additives which clean
the cylinder liner.
CYLINDER LUBRICATION

31. On a two stroke crosshead engine
lubricating oil is supplied to the main
bearings and camshaft and camshaft
drive. A separate supply is led via a
swinging arm or a telescopic pipe to
the crosshead where some of it is
diverted to cool the piston (travelling
up and back through the piston rod),
whilst some is used to lubricate the
crosshead and guides, and the rest
led down a drilling in the connecting
rod to the bottom end or crankpin
bearing. Oil is also used to operate
the hydraulic exhaust valves.

32. VIDEO PRESENTATION

33. IX. GENERALLY ACCEPTED MARITIME
TERMS
1. Swept Volume
-Swept volume can be defined as the volume swept by the
engine piston during one stroke.
Swept volume is also the product of piston area and stroke.
2. Clearance Volume
-Clearance volume can be defined as the volume that
remains in the cylinder when the engine piston is in the top-
centre position.
-Clearance volume can also be defined as the difference
between the total cylinder volume and the swept volume.
The space covered by the clearance volume also forms the
combustion chamber.

34. 3. Compression Ratio
Compression ratio can be defined as the value obtained by
dividing the total cylinder volume by the clearance volume.
4. Volumetric efficiency
Volumetric efficiency can be defined as the ratio of the
volume of air drawn in to the cylinder to the swept volume.
5. Scavenge Efficiency
Scavenge efficiency can be defined as the ratio of the
volume of air in the cylinder at the start of the compression
to the volume swept by the piston from the top edge of the
ports to the top of the strokes.

35. 6. Air Charge Ratio
Air charge ratio can be defined as the ratio of the air contained in the
cylinder at the start of the compression to the swept volume of the
piston. It is also known as air mass ratio or air supply ratio.
7. Natural aspiration
Natural aspiration is a term which mainly applies to four stroke engines
and is defined as the process by which air charge is brought in to the
engine cylinder by only the downward movement of the piston without
using other aids.
8. Supercharging
Supercharging is a term used to indicate that the weight of the air
supplied to the engine has been considerably increased for greater fuel
usage and power production per stroke.
It is also noted that supercharged engines produce more power as
compared to non supercharged engines having the same stroke and
speed.

36. Shalom!