Essential reading:

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Tomislav Skracic, MAUndergraduate English Course
forMARINE ENGINEERS5th Semester

• Essential reading
• SPINCIC, A., PRITCHARD, B., An English Textbook
  For Marine Engineers 2, Pomorski fakultet, Rijeka
  2009.
• LUZER, J., SPINCIC, A., Gramaticka vježbenica
  engleskog jezika za pomorce, Pomorski fakultet,
  Rijeka 2003.

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• LESSON 11

FUEL OIL SYSTEMS
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• FUEL OILS
• H.F.O. Heavy fuel oil (residual, blends
  crudes)
• D.F.O. Diesel fuel oil or M.D.O. Marine Diesel
  oil or light fuel oil ( in restricted sense )
• 1.1.1 Residuals are residues from various
  rafinery processes
• 1.1.2 Blends are fuel oil mixtures of different
  viscosity to obtain a product of desired
  viscosity and density.
• 1.1.3 Crudes natural mixtures consisting of
  hydrocarbons sulphur, nitrogen and / or oxygen
  derivatives of hydrocarbons.

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2. FUEL VISCOSITY Viscosity is the internal
resistance of a fluid to relative movement. Oil
is more viscous when cold. Viscosity is measured
in Redwood Universal, Saybolt Universal, Saybolt
Furol and Engler, but most commonly in kinematic
cSt.
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3. PURPOSE OF THE FUEL OIL SYSTEM To store,
transfer clean the oil prior to injection. 4.
SEPARATE FUEL OIL SYSTEMS 4.1 H.F.O. Heavy fuel
oil ? in navigation 4.2 D.F.O. Diesel fuel oil
/ or M.D.O. Marine Diesel oil / or light fuel
oil ? in manuvering.
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5. FROM THE DOUBLE BOTTOM TO THE ENGINE 5.1 Oil
is taken from the double bottom tanks and pumped
into a settling tank. 5.2 Then it is heated in
the settling tank (the sediment and the water are
drawn off. ) 5.3 Next, the fuel is purified in a
centrifuge (a centrifuge is a unit usually
consisting of a purifier and a clarifier). 5.3.1
. A purifier eliminates contaminants and a
clarifier eliminates high density
impurities). 5.4 Then it is admitted into a
service tank.
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5. FROM THE DOUBLE BOTTOM TO THE ENGINE 5.5
From the service tank the oil is passed through a
heated buffer tank to the booster pumps (or fuel
delivery pump). 5.5.1 Buffer tank or a mixing
tank a) H.F.O. and M.D.O. are mixed in
it b) it recives a surplus fuel not consumed
by engine 5.6 Eventualy it is discharged into
injection system through a fuel heater, viscosity
regulator and a fine filter.
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B. Pritchard, J. Luzer, M. Borucinsky, A. Spincic
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6. SAFETY DEVICES 6.1 Low tank level alarm
signals that a level in the tank is too low. 6.2
Pressure loss alarm indicates a pressure drop
below permissible limits. 6.3 Viscosity
regulator controls fuel oil temperature, i.e.
viscosity) 6.4 Pressure regulating valve ensures
constant pressure at the fuel main 6.5 Quick
close valves are valves having collapsable briage
and may be closed from outside machinery
space. 6.6 Emergency remote cut-out switches
fitted to the pumps and actuated in case of
emergency.
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• Gear pump rotates at about 40 rpm
• Fuel inlet / supply is close to the heater
  discharge
• The fuel is discharged through a capillary tube
• The pressure diference between each end of the
  tube is directly proportional to the viscosity of
  oil flowing through it.
• Pressures are measured with Bourdon tubes and
  compared to read as viscosity.
• Pressures are fed to a differential presure
  transmitter which can automatically operate the
  heater control to maintain fuel viscosity within
  close limits

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7. COMBUSTION
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B. Pritchard, J. Luzer, M. Borucinsky, A. Spincic
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8. FACTORS LEADING TO GOOD COMBUSTION 8.1
VISCOSITY It must be low enough to ensure
correct atomisation at the fuel injection. When
fuel oil is heated its viscosity is reduced. 8.2
ATOMISATION Is splitting up the fuel into very
small droplets. The size of a droplet depends
upon a) the atomizer holes b) pressure
difference between the fuel pump discharge and
that of the compressed air in the combustion
chamber.
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B. Pritchard, J. Luzer, M. Borucinsky, A. Spincic
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8.3 PENETRATION Is the distance the oil
droplets travel into combustion space before
mixing with air and igniting.
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Penetration depends upon a) atomisation b)
velocity leaving the injector c) conditions
within the combustion chamber It is desirable
that the fuel penetrates into the whole
combustion space but it should not impinge on the
internal surface before burning. 8.4
TURBULENCE Is the movement of the compressed air
and fuel within a combustion space before
combustion occurs.
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B. Pritchard, J. Luzer, M. Borucinsky, A. Spincic
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• Turbulence is caused by
• swirl, which is impared due to the air entry at
  scavange ports
• fuel spray pattern
• piston crown shape
• Turbulence improves fuel and air mixing for
  effective and rapid combustion.

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9. FUEL INJECTORS They are inserted into fuel
valve pocket of the engine cylinder. Injectors
can be fitted centrally (symmetrical fuel spray)
or in other way depending upon the position of
exhaust valves.
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B. Pritchard, J. Luzer, M. Borucinsky, A. Spincic
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9. FUEL INJECTORS Defects a) choking due to
dirt b) inadeqate cooling ( high t. ? carbon
building up on the atomiser) ( low t. ?
external corrosion) Testing Fuel injectors
must be regulary overhauled After assembly an
injector is tested with a test pump (operating
pressure and fuel spray) There should be no
leakages.
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• 9.1 COOLING
• By circulating water or oil through cooling
  passages.
• Heavy fuel injectors are fitted with water
  cooled nozzles.
• If there were no cooling, the nozzles would
  become too hot and liable to carbon deposits.

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• 9.2 VALVE BODY OR NOZZLE HOLDER CONTAINS
• spring,
• compression nut,
• intermediate spindle,
• fuel oil passages,
• cooling passages

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• 9.2 VALVE BODY OR NOZZLE HOLDER CONTAINS
• spring,
• compression nut,
• intermediate spindle,
• fuel oil passages,
• cooling passages

The body of an injector has a hardened
surface. The nozzle or atomiser is secured by a
compression nut / retaining nut / spring
adjusting nut. A dowel is fitted to ensure that
fuel oil passages and cooling water passages are
aligned. The needle valve and the atomiser are
kept as one unit.
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• 9.3 FUEL INJECTOR NEEDLE VALVE
• Spring loaded non-return needle valve (1) is
  lapped in a bore of an atomiser (2).
• The pump supplies fuel oil through the oil fuel
  passage (6).
• The upper chamber (3) is charged with fuel and
  sealed by needle valve (1).
• The lower chamber (5) is sealed with mitre seat
  (4), also making an effective oil seal.
• Atomiser holes (7) are used for discharging the
  fuel through them at a high pressure.

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• 9.4 NOZZLES
• 9.4.1. Purpose
• The fuel is injected at high velocity through
  small holes in the injector nozzle and the fine
  spray penetrates throughout the combustion
  chamber.
• the injection must be sharp to avoid
  deterioration of spray into a dribble or jets.

• 9.4.2. Opening pressure
• Usually about 600 bar (for medium speed diesel
  engines)
• 9.4.3 Types
• Multi orifice type.
• The disposition of holes and their number depend
  upon the combustion chamber design.

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Fuel injector and some examples of nozzles
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Exercise 1 Supply the missing terms

• Internal combustion engine procedure
• The fuel oil system for a diesel engine can be
  considered in two parts the fuel supply and the
  fuel __________ systems. Fuel supply deals with
  the __________ of fuel oil suitable for use by
  the injection system.
• A slow-speed two-stroke diesel is usually
  arranged to operate continuously on __________
  and have available a diesel oil supply for
  __________ conditions.

heavy fuel injection manoeuvring provision
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Exercise 1 Supply the missing terms

• The oil is stored in tanks in the __________ from
  which it is pumped to a __________ tank and
  heated. After passing through centrifuges the
  cleaned, heated oil is pumped to a daily
  __________ tank. From this tank the oil flows
  through a three-way __________ to a mixing tank.
  A flow meter is fitted into the system to
  indicate fuel consumption. __________ are used to
  pump the oil through heaters and a viscosity
  __________ to the engine-driven fuel pumps. These
  pumps will discharge high-pressure fuel to their
  respective __________.

valve injectors settling booster pumps double
bottom regulator service
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Exercise 1 Supply the missing terms

• The viscosity regulator controls the fuel oil
  __________ in order to provide the correct
  viscosity for combustion. A pressure regulating
  valve ensures a constant-pressure supply to the
  engine-driven pumps, and a __________ bypass is
  used to heat up the fuel before starting the
  engine. A diesel oil daily service tank may be
  installed and is connected to the system via a
  __________ .

temperature pre-warming three-way valve
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Exercise 1 Supply the missing terms

• The engine can be started ________ and manoeuvred
  ________diesel oil or even a blend of diesel and
  heavy fuel oil. The mixing tank is used to
  collect recirculated oil and also acts ________ a
  buffer or reserve tank as it will supply fuel
  when the daily service tank is empty.The system
  includes various safety devices such ________
  low-level alarms and remotely operated tank
  outlet valves which can be closed ________ the
  event of a fire.

as as on in up
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Exercise 1 Supply the missing terms

• Delivering right amount of fuel
• The function ______ the fuel injection system is
  to provide the right amount of fuel ______ the
  right moment and in a suitable condition ______
  the combustion process. There must therefore be
  some form of measured fuel supply, a means ______
  timing the delivery and the atomisation of the
  fuel.The injection of the fuel is achieved
  ______ the location of cams ______ a camshaft.
  This camshaft rotates at engine speed for a
  two-stroke engine and ______ half engine speed
  for a four-stroke.

at at by for of of on
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Exercise 1 Supply the missing terms

• A typical fuel injector ________ two basic parts,
  the nozzle and the nozzle holder or body. The
  high-pressure fuel enters and ________ down a
  passage in the body and then into a passage in
  the nozzle, ________ finally in a chamber
  surrounding the needle valve. The needle valve
  ________ closed on a mitred seat by an
  intermediate spindle and a spring in the injector
  body. The spring pressure, and hence the injector
  opening pressure, ________ by a compression nut
  which acts on the spring. The nozzle and injector
  body are manufactured as a matching pair and are
  accurately ground to ________ a good oil seal.
  The two ________ by a nozzle nut.

are joined can be set ending has give is
held travels
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Exercise 1 Supply the missing terms

• The __________ valve will open when the fuel
  pressure acting on the needle valve tapered face
  exerts a sufficient __________ to overcome the
  spring compression. The fuel then flows into a
  lower __________ and is forced out through a
  series of tiny holes.
• The small holes are sized and arranged to
  atomise, or break into tiny __________, all of
  the fuel oil, which will then readily burn. Once
  the injector pump or timing __________ cuts off
  the high pressure fuel supply the needle valve
  will shut quickly under the spring __________
  force.

chamber compression drops force needle valve
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Exercise 2 Describe the fuel oil system and the
passage of fuel oil from the DB tank to the engine
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