Internal Combustion Engines Flashcards
A diesel engine requires five supporting systems in order to operate
Air intake, exhaust, cooling, lubrication, and fuel injection
The back and forth motion of one or more pistons is transformed into the rotary motion of the crankshaft
Reciprocating engines
Diesel engines are not self speed limiting because the air entering the engine is
Always the maximum amount
Engine speed is limited solely by
The amount of fuel injected into the engine cylinders
Diesel engines require a _____ to control the amount of fuel being injected into the engine
Speed limiter (governor)
A diesel engine does not require ____
An ignition system
In a diesel engine, the fuel is injected into the cylinder as ____
The piston comes to the top of its compression stroke
When fuel is injected in a diesel engine, it vaporizes and ignites due to
The heat created by the compression of the air in the cylinder
Terms used to define the displacement of an engine
Bore and stroke
Displacement is measured in
Cubic inches or litres
Diametre of the engine’s cylinders
Bore
The distance the piston travels from the top of the cylinder to the bottom
Stroke
Bore x stroke x number of cylinders equals
Displacement
Highest point of travel by the piston
Top dead center
Lowest point of travel by the piston
Bottom dead center
There are ____ degrees of crankshaft travel between TDC & BDC
180
All events that occur in the engine are related to
The location of the piston
For a diesel engine, power is rated in
Units of horsepower
The power transmitted to the pistons by the gas in the cylinders and is mathematically calculated
Indicated horsepower
Amount of useable power delivered by the engine to the crankshaft
Brake horsepower
Indicated horsepower can be as much as ___ higher than brake horsepower
15%
The difference between indicated and brake horsepower is due to
Internal engine friction, combustion inefficiencies, and parasitic losses
Ratio of an engine’s brake HP and its indicated HP
Mechanical efficiency
Mechanical efficiency of a four cycle diesel
About 82 - 90 percent
Measure of an engine’s ability to apply the power it is generating
Torque
Torque is commonly given in units of
Foot pounds
1 HP = _____ ft-lbs/min or ____ ft-lbs/sec
33000
550
Amount of compression
Compression ratio
Amount of space within the cylinder when the cylinder is at BDC as compared to the amount of space within the cylinder when the piston is at TDC
Compression ratio
Gasoline engine compression ratios range from
8:1 to 12:1
Diesel engine compression ratio ranges from
14:1 to 25:1
The high compression ratio of a diesel engine heats the air in the cylinder to approximately
1000•F
Ignites the fuel when injected into the cylinder (diesel)
Heat of compression
To find the compression ratio
Divide the total volume of the cylinder with the piston at BDC by the volume of the cylinder at TDC
Machine that converts thermal energy into mechanical energy
Engine
The correct relationship between the crankshaft and camshaft
Timing
Must be maintained so that the fuel injector operation and the opening and closing of inlet and exhaust valves occur in the correct sequence
Timing
In a four stroke engine, the camshaft is geared so that it rotates at ____ the speed of the crankshaft
Half (1:2)
Air is drawn into the cylinder due to
The negative pressure created by the increase in cylinder volume
At BDC the air in the cylinder is at
Atmospheric pressure (14.7 psia)
When the piston has traveled to the top of its stroke, the temperature has increased to approximately ___ and approximately ____ (pressure)
1300•F
750 psia
In a four stroke engine, scavenging takes place when
The piston is nearing TDC during the latter part of an upstroke and the early part of the downstroke
Have a better mechanical efficiency
Two stroke engine
Less fuel efficient engine
Two stroke engine
In a two stroke engine, the camshaft is geared so that it rotates ____ the crankshaft
At the same speed as (1:1)
Installed in all two stroke diesel and some four stroke diesel engines, increase the flow of air into the cylinders
Blower
Compresses the air and forces it into an air box or intake manifold
Blower
Creates constant air pressure that is available during the cycles of operation
Blower
In a two stroke engine, scavenging takes place during
The latter part of the downstroke and the early part of the upstroke
After the piston travels approximately ___ of the way to BDC, the piston starts to uncover the inlet or scavenging ports
3/4
Lets the blown, compressed fresh air enter the cylinder which helps cool the cylinder and scavenge the cylinder of the remaining exhaust gases
Overlap
Air forced into the cylinder
Scavenge air
Ports through which air is forced into the cylinder
Scavenge ports
In a four stroke diesel engine, what term is used to describe the timeframe during which both the intake and exhaust valves are open
Valve overlap
Secure an engine in place to the hull structure or a sub base, but are not actually part of the engine
Engine mounts
Two types of engine mounts
Rigid and flexible
Prevent any movement of the engine in relation to the cutter or boat
Rigid mounts
Two primary types of rigid mounts
Rigid and epoxy
Used for absorbing minor engine vibrations
Flexible engine mounts
Mounting pedestal for the engine and its driven machinery, where alignment is critical
Sub-base
Secure the engine, driven machinery, and sub-base to the hull structure
Foundation bolts
Foundation bolts must be inspected for what periodically
Tightness
Method of inspecting foundation bolts
Sounding
If the sounding is clear (like a bell)
The bolt is tight
If the sounding is dull (like a thud)
The bolt needs tightening
Wear what when sounding foundation bolts
Safety goggles
Provides the structure and rigid frame for the engine’s cylinders, coolant, and oil passages, and provides support for the crankshaft and camshaft bearings
Block
The area around the crankshaft and crankshaft bearings
Crankcase
Usually located on the bottom of the cylinder block
Crankcase
Located at the bottom of the crankcase
Oil pan
This area encloses the rotating crankshaft and crankshaft counterweights and directs returning oil into the oil pan
Crankcase
Collects and stores the engine’s supply of lubricating oil
Oil pan
Provides the top seal for the cylinder bore or sleeves
Cylinder head
Provides the structure holding exhaust valves (and intake valves where applicable), the fuel injector, and necessary linkages
Cylinder head
Construction of the cylinder head
Designed to withstand rapid changes in temperature and pressure, and is normally made of a heat resistant cast iron or alloy
Seals the surface between the cylinder block and cylinder head
Cylinder head gasket
Cylinder head studs are manufactured from
Round rod, generally of alloy steel
Two types of cylinders
Integral liner
Removable liner
Each cylinder is bored or machined into the block casting, making the block and cylinders an integral part
Integral liner
A machined steel sleeve/liner is pressed into the block casting to form the cylinder
Removable liner
Provides the engine with the cylindrical structure needed to confine the combustion gases and to act as a guide for the engine’s pistons
Cylinder liner, bore, or barrel
Construction of cylinder liners
Commonly close-grain cast iron, and may be treated with chromium to aid in oil retention
Three types of cylinder liners
Dry liner
Wet liner
Water-jacketed
Engine coolant circulates in passages in the engine block; the liner does not come into contact with the coolant
Dry liner
Engine coolant comes into contact with the liner
Wet liner
The cooling jacket is an integral part of the liner assembly. The flow through this liner is normally bottom to top
Water jacketed
To ensure a good seal will be made between the piston rings and liner, this check must be performed prior to piston intallation
Out of roundness check
Use ___ to check liners with integral cooling passages
Hydrostatic testing method
Use ___ equipment to locate cracks in dry liners
Magnaflux
To locate cracks in a liner with integral cooling passages, technicians will commonly fill the passage with
Glycol type antifreeze
Components that move up and down or back and forth in a repetitive motion
Reciprocating components
Transforms the thermal energy of the expanding gases into mechanical energy
Piston
Rides in the cylinder liner or sleeve
Piston
Pistons are commonly made of
Aluminium or cast iron alloys
____ pistons are used in high speed engines because they are lightweight and provide better heat transfer
Aluminium
____ pistons are used in low speed engines because they offer a longer service life and less wear
Cast iron
Prevent the combustion gases from escaping and keep friction to a minimum
Piston rings
How much of a pistons heat is transferred via ring contact with the piston wall
About 30%
The upper part of a piston directly responsible for changing the volume of the cylinder
Crown
Reinforcement used on larger pistons to prevent flexing or warping
Piston crown rib
Can serve as the crown rib on smaller pistons
Piston pin boss
The side of the piston
Piston skirt
Receives the side thrust created by the movement of the connecting rod and crankshaft, and works to keep the piston in proper alignment
Piston skirt
Three skirt designs
Plain
Slotted
Knurled
Rib around the inside of the skirt used on large pistons or long skirted pistons to prevent flexing or warping
Skirt reinforcement
Rings are usually made of
Cast iron and coated with chrome or molybdenum
Most pistons have how many rings
Two to five
___ acts primarily as the pressure seal and is known as a compression ring
Top ring
____ acts as a wiper ring to remove and control the amount of oil film on the cylinder walls
Intermediate ring
___ is an oiler ring and ensures that a supply of lubricating oil is evenly deposited on the cylinder walls. Also known as an oil control ring
Bottom ring
Seals the combustion chamber, preventing blow by and loss of power
Compression ring
Transfers heat from the piston to the cylinder wall
Compression ring
On the upstroke, prevents metal to metal contact by distributing oil to the cylinder wall
Oil control ring
On the down stroke, wipes excess oil from the cylinder wall, preventing oil from burning in the cylinder
Oil control ring
Spring steel ring placed behind the oil control ring to increase the pressure of the ring face against the cylinder wall
Flexible ring with expander
Ring gap of the expander is placed ____ from the gap of the oil control ring
180 degrees away
The part of the ring that comes in contact with the cylinder wall
Face
The distance from the face to the inside edge of the ring
Wall thickness
The ends of the rings, which allow the ring to be expanded over the piston and compressed to fit into the cylinder bore
Ring joint
The distance between the ends of the ring
Ring gap
Hold the rings in place
Piston grooves
Done to ensure proper fit of rings in the piston
Measuring piston groove width and depth
The space between the rings and the lands that allows the ring to expand
Side clearance
Side clearance is measured with
A feeler gauge
The link between the piston and the connecting rod
Piston pin (wrist pin)
Piston pin is usually constructed of
Hollow, machined, hardened, precision ground, alloy steel and provides maximum strength with a minimum of weight
The piston pin is attached one of three ways
Fixed or stationary
Semi-floating
Full-floating
The pin is secured to the piston pin bosses by a bolt or pin, and the connecting rod rotates on the wrist pin
Fixed or stationary
The pin is secured to the connecting rod by a bolt or pin, and the wrist pin rotates in the piston pin bosses
Semi-floating
The pin is free to rotate in the piston pin boss and the connecting rod
Full-floating
Heavily reinforced opening in the skirt
Piston pin boss
The mounting point for bushings or bearings which support the piston pin
Piston pin boss
Rib over the piston pin boss to prevent flexing or warping of the boss
Piston pin boss reinforcement
Clean the piston components with ___ and dry them with ____
Fuel oil
Compressed air
Connects the piston to the crankshaft
Connecting rod
The rods are made from
Drop-forged, heat-treated steel
Two types of connecting rod construction
Conventional construction
Fork and blade construction
Changes the reciprocating movement of the pistons and the connecting rods into a rotary motion
Crankshaft
Normally crankshafts are machined from
Forged alloy or high carbon steel, sometimes a cast iron alloy
Serve as the points of support and as the center of rotation for the shaft
Main journals
Hollow construction of the journals ___
Reduces weight considerably, increases torque capability of the crankshaft, provides a passage for the flow of oil
The rear main journals in some applications are ___ than the front end journals due to ____
Larger
The weight of the flywheel and the extra support it needs
The points of attachment for the connecting rods and are offset from the main journals
Connecting rod journals
Form the link between the main or intermediate journals and the connecting rod journals
Webs
The arrangement of two webs together with the connecting rod journal
Throw
Balance the off-center weight of the individual crank throws and thereby compensate for centrifugal force generated by each rotating crank throw
Counterweights
Counterweights will always be found in
Pairs
Use inertia to reduce the pulsating effect of power impulses
Counterweights
In all engines, the bending of the crankshaft takes place primarily in ___
The webs
Crank web deflection should be taken ___
After major overhaul
Dry dock
Haul out of the cutter
Crank web deflection readings should only be taken with the cutter ___
In the water
For engines with crank journals of ____, crankshaft deflection readings are to be recorded in ____
Four inches or more
Machinery history and reported in the cutter engineering report
Micrometre for measuring the differences in distance between the webs of a crankshaft during a revolution of the shaft
Strain gauge
The strain gauge should be installed with its two endpoints in ___
The crankshaft prick-punch marks
Strain gauge readings are generally taken at five crank positions
TDC, inboard, near or at BDC, outboard, TDC again
If the strain gauge reading is not within _____, a complete set of readings will need to be retaken
.0025 of 0
When the driving mechanism of an engine consists only of gears, the mechanism is commonly called
Gear train
Gear teeth placed at an angle
Helical teeth
Placed between two other gears to transfer motion from one gear to the other without changing their direction
Idler gear
The space between the thickness of a gear tooth and the width of the space between teeth in the matting gear
Backlash
Backlash is normally measured using
A feeler gauge
The camshaft is driven by a series of gears called
Idler gears
Timing gears
Serve to support rotating shafts and other moving parts, also used to transmit loads from one part of the engine to another
Bearings
Two basic types of engine bearings
Anti-friction bearings
Friction bearings
The use of anti-friction bearings is limited mainly to ___
The exterior areas of the engine
Anti-friction bearings can be grouped into six general classifications
Ball bearings Cylindrical roller bearings Needle bearings Tapered roller bearings Self-aligning roller bearings Thrust bearings
All anti-friction bearings employ a
Rolling element
Roller bearings are often made of
Carbonised steel alloy
Type of friction bearing used in most CG engines
Precision type
Stores up energy during the power event and releases it during the remaining events of the operating cycle
Flywheel
Flywheels are made of
Cast iron, cast steel, or rolled steel
Device used to absorb torsional vibrations of the crankshaft
Vibration damper
The vibration damper is mounted on ___
The crankshaft at the front of the engine
Uses a freely rotating disk acting against a fixed disk which creates friction and thereby acts as a brake
Vibrating damper
Consists of a hollow housing that contains a free or floating flywheel. The small clearance between the flywheel and the housing is filled with a ___
Viscous silicone fluid
Limits the increase or decrease in speed during sudden changes of load
Flywheel
Counterweights use ____ to reduce the pulsating effects of power impulses
Inertia
The group of parts that changes the type of motion and causes the valves of an engine to operate
Valve actuating mechanism
Long bar with egg-shaped eccentric lobes, one lobe for each valve and fuel injector
Camshaft
Slop or give in the valve train before the cam actually starts to open the valve
Valve lash
Eccentric projections that change the rotary motion of the camshaft to the reciprocating motion needed to operate the valves, injectors, and other components
Cam lobes
The amount a valve opens or moves away from its seat
Lift
The amount of time that a valve remains open
Duration
The sides of the cam
Flanks
The highest point on the cam
Nose
Transmit the rotating motion of the the cam to the the rocker arm. They ride the flank of the cam and are raised by the nose as the camshaft rotates
Cam followers
Three types of cam followers
Flat
Roller
Pivoted
Type of cam follower, provides for quick opening and closing of the valves
Flat
Type of cam follower, Provides for reduced friction between moving parts
Roller
Type of cam follower, Similar to the roller follower. The main advantage is that the pivot arm (instead of the sliding follower) takes up the side thrust created by the cam
Pivoted
Part of the actuating assembly responsible for transmitting the motion of the cam follower to the rocker arm
Pushrod
Constructing of pushrod
Usually hollow
Cup in the tip
Round at the other end
Hardened wear surfaces
Transmits the motion of the cam follower to the valve
Rocker arm
One end is in contact with the valve stem and the other end is actuated by the camshaft
Rocker arm
Mechanically opened and closed to admit or exhaust the gases as needed
Valves
The point at which the valve seals against the head
Valve seat
Part of the actuating assembly that admits intake air and discharges the exhaust gases from the combustion space
Poppet valve
The heads of poppet valves have
Beveled edges
Exhaust valves are usually made of
Silicon chromium steel
Acts as a surface against which a valve comes to rest to provide a seal against leaking
Valve seat insert
Replaceable ring that fits into a counter-bored recess in the valve port of the cylinder head
Valve seat insert
Three methods to install a valve seat insert
Pressing insert into place
Cold shrink method
Heat sink method
Reduces the diameter of the insert by the use of dry ice
Cold shrinking
Involves heating the head and installing the insert and then allowing the head to cool
Heat sinking
Prevent undesirable side to side movement of the valve in the cylinder head
Valve guides
Valve guides are usually made of
Materials that are softer than the valve stem
Returns a valve to the closed position
Valve spring
Valve springs are made of
Round steel wire wound in a helical coil
The two supports that the valve springs are mounted between
Valve spring retainers
The lower spring retainer may simply be
A recess in the top of the cylinder head
