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7/27/2019 (1) Aunit1l3terminologia Del Rendimiento
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Lesson 3: Engine Performance Terminology
Objective:
The student will be able to define essential engine performance
terminology and calculate engine displacement, compression ratio,
and horsepower.
References:
Glossary of Terms LEXQ8150
Introduction:
To understand diesel engine design and performance, it is necessary
to know the terminology and math calculations that apply to diesel
engines.
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Unit 1 1-3-2 Engine Fundamentals
Lesson 3
This presentation will review engine performance and engine
performance terminology.
Fig. 1.3.1
There are many factors that determine the performance of an engine.
The operating conditions that an engine is exposed to and the specific
application an engine is placed in can affect the performance of the
engine. Many of the determining factors for performance, however,
are determined by the manufacturer of the engine.
Some of the basic specifications that a manufacturer makes on an
engine that affect performance of the engine are:
Bore
StrokeDisplacement
Compression Ratio
The performance of an engine is typically rated by comparing power
output and/or efficiency of the engine. These evaluations can be
measured in several different ways. The basis for these
measurements and the manufacturers specifications must be known
in order to better understand the effects that all of these factors and
measurements have on engine performance.
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Unit 1 1-3-3 Engine Fundamentals
Lesson 3
BDC
TDC
STROKE
BORE
CRANKSHAFT
AT TDC
CRANKSHAFT
AT BDC
Fig. 1.3.2
Top Dead Center (tdc)
Top dead center (tdc) is a term used to describe the position of thepiston when the piston is at its highest point in the cylinder. This
occurs when the crankshaft and the connecting rod are fully extended
and straight with one another. Many events in the operation of the
engine are identified by crankshaft position, measured in degrees
either before or after tdc.
Bottom Dead Center (bdc)
Bottom dead center (bdc) is a term used to describe the position of
the piston when the piston is at its lowest point in the cylinder. This
occurs when the crankshaft and the connecting rod are fully retractedand straight with one another.
Bore (B)
Bore is a term used to describe the diameter of a single cylinder in an
engine. Bore is typically measured in millimeters or inches.
Stroke (L)
Stroke is a term used to describe the distance that a piston travels in
the cylinder of the engine. The stroke is measured as the difference
between the position of the piston at BDC to TDC. The amount of
stroke is determined by the design of the crankshaft. The stroke is
equal to exactly twice the throw of the crankshaft. Stroke is typically
measured in millimeters or inches.
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Unit 1 1-3-4 Engine Fundamentals
Lesson 3
17 TO 1
DIESEL ENGINE
Fig. 1.3.3
Engine Displacement
The bore, the stroke, and the number of cylinders all determine the
displacement of an engine. The displacement of an engine is simply
the amount of volume displaced by all cylinders in an engine during
one complete rotation. The displacement of an engine can becalculated using the following formula:
Displacement = x r2 x L x n
Where...
= 22/7
r2 = radius x radius
radius = 1/2 bore
L = stroke
n = number of cylinders in the engine
Compression Ratio
The compression ratio of an engine is determined by the cylinder
displacement and the combustion chamber volume. In order to
calculate the compression ratio use the following formula:
CR = Total Cylinder Volume / Combustion Chamber Volume
Typical compression ratios of diesel engines range from 11:1 to
22:1. This is significantly higher than the compression ratio of a
typical gasoline engine. Diesel engines utilize higher compression
ratios to increase the pressure within the combustion chamber.
Higher pressures will cause an increase in the temperature of the air
and fuel in the combustion chamber. This high temperature
(approximately 1000F) will cause the diesel fuel to ignite without
the use of a spark plug.
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Work
Work is defined as a force that is applied over a distance.
W = F x D
Power
Power is defined as the rate at which work is performed
P = F x D / t
or
P = W / t
Where t is the time that the work is performed in.
The standard measure of power in the metric system is the kilowatt
(kW), and in the english system the standard measure of power is the
horsepower (HP).
1 HP = 0.746 kW
1 kW = 1.340 HP
The term horsepower was originally derived by James Watt, a
scottish inventor. Watt observed the ability of a horse in coal mine
hoisting coal. He defined 1 HP to be equal to the ability of a horse to
raise 33,000 lb of coal a distance of 1 ft in 1 minute.
There are several different types of power that are often discussed.
Indicated horsepower (IP) is the power that an engine is
theoretically able to produce. This is found by multiplying the
displacement of the engine by the mean effective pressure in the
cylinder in pounds per square inch and dividing it by 33,000.
Brake engine horsepower (BP) is the power that is found by
physically testing an engine on a dynamometer. A dynamometer
is a device that is coupled to an engine for the purpose ofmeasuring the torque and the horsepower output of the engine.
Friction power (FP) is the power that an engine requires in order
to overcome the frictional losses of bearings, gears, and other
moving parts of the engine. Friction power increases as the size
and/or the speed of an engine increases.
BP = IP - FP
Unit 1 1-3-5 Engine Fundamentals
Lesson 3
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Torque
When the engine is running, the combustion that takes place causes
the pistons to move downward in the cylinder. This downward piston
motion pushes on the connecting rods and causes the crankshaft to beturned. The resulting twisting force produced by the crankshaft is
called torque.
The torque and the horsepower that an engine produces are related to
one another with the following equation:
HP = T x RPM / 5252
NOTE: This formula can not be used with metric units. Convert
the metric units to english units before performing the
calculation.
Where...
T = Torque (measured in ft lb)
5252 = 33,000 / 2 (constant)
The constant of 5252 is derived by dividing the 33,000 lb in Watts
horsepower formula by the angular value of one rotation of the
crankshaft in radians, 2.
Torque is measured in foot-pounds (ft lb) in the english system and inNewton-meters (Nm) in the metric system.
1 ft lb = 1.3558 Nm
1 Nm = 0.7376 ft lb
Friction
A certain amount of force is required in order to slide the surfaces of
two objects against one another. The resistance to this motion is
called friction. As the load is increased, friction is increased. For
example it requires more effort to slide a heavy object than it does to
slide a light object. The condition of the two surfaces in contact also
makes a difference. This is why the lubrication system in an engine
is so important. The oil film between the moving parts of an engine
keep the friction between the two surfaces very low. This not only
gives the engine a long service life, but also creates less drag on the
engine, reducing the amount of frictional power. This allows the
engine to produce more brake power.
Unit 1 1-3-6 Engine Fundamentals
Lesson 3
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Inertia
Sir Isaac Newtons first law of motion states that an object in motion
tends to stay in motion and an object at rest will tend to stay at rest,
until acted upon by an outside force. This phenomenon is due toobjects possessing inertia. The amount of inertia an object has is
directly proportional to the amount of mass that the object has. For
example a car has more inertia than a bicycle. This is why it is
harder to move or stop a car than a bicycle.
Efficiency
The efficiency that a particular engine has is expressed as a
percentage of the actual power to the theoretical power of an engine.
The actual power produced by an engine is always less than the
theoretical power. There are several ways to describe the efficiencyof an engine.
Volumetric efficiency is defined as how capable an engine is of
filling the cylinder with air on the intake stroke compared to the
cylinder being completely filled with air at atmospheric pressure.
Because air must be sucked into the cylinder with the downward
motion of the piston, the engine is never able to fill the cylinder
100%.
Brake power is the amount of usable power that an engine
actually produces. Indicated power is the amount of theoreticalpower that an engine should be able to produce. Mechanical
efficiency is the ratio of brake power to indicated power.
BP / IP = Mechanical Efficiency
Thermal efficiency is the degree to which an engine is able to
successfully convert the energy in the fuel into heat energy to
cause the pistons to turn the crankshaft.
Fuel efficiency is defined in several different ways. The most
common of which is kilometers per liter (km/L) or miles per
gallon (mpg), which would be used to describe the fuel efficiencyof an engine in an over the road application such as in a truck.
Fuel efficiency for marine or industrial applications may be
expressed in liters per hour (Lph) or gallons per hour (gph) at
rated speed.
Fuel efficiency may also be expressed in brake specific fuel
consumption (bsfc). Bsfc is defined as the amount of fuel used
per unit of power and time. The bsfc of an engine is expressed in
either g / (kW hr) or lb / (hp hr).
Unit 1 1-3-7 Engine Fundamentals
Lesson 3
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Unit 1 1-3-8 Engine Fundamentals
Lesson 3
12,000 FT.9.3 PSI
8,000 FT.
10.9 PSI
4,000 FT.
12.7 PSI
3657 M.64.12 kPa
2438 M.
75.15 kPa
1219 M.
87.50 kPa
101.35 kPa SEA LEVEL SEA LEVEL 14.7 PSI
EARTH'S SURFACE
WEIGHT OF
AIR ONEARTH'SSURFACE
Fig. 1.3.4
As an example, due to increased pressure at sea level the air is more
dense than the air on top of a mountain. The dense air allows for
more air molecules to flow into the cylinder. This allows for the fuel
to be more completely burned in a diesel engine, which produces
more power. This is why engines perform better in lower altitudes,
the air is more dense.
Ambient air temperature also plays a role in how much air can flow
into an engine. The lower the temperature of the air, the more dense
the charge of air is that enters the cylinders. The greater the density
of the air, the more power that can be produced efficiently in theengine.
Humidity is also an important factor in diesel engine combustion.
Humidity is a relative measure of the amount of moisture that is
suspended in the air. The suspended moisture has a cooling effect on
the air as it enters the engine. Therefore, the greater the humidity of
the air, the colder the air, the denser the air, the more power that can
be produced efficiently in the engine.
Atmospheric Conditions
In order to produce the desired levels of power, diesel engines require
a large volume of air. Therefore the atmospheric pressure, the
ambient air temperature, and the relative humidity of the air play alarge role in the performance characteristics of the engine.
It is the atmospheric air pressure that is present that forces the air into
the engine. Atmospheric pressure is the pressure that is exerted on
the earths surface due to the weight of the atmosphere (the air
surrounding the earth). Atmospheric pressure is greatest at sea level
because there is more air above the air at sea level than there is above
the air at the top of a mountain. Refer to figure...
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Unit 1, Exercise 1.3.1
Define the following terms:
TDC - Top Dead Center: The highest position that a piston reaches in the cylinder.
BDC - Bottom Dead Center: The lowest position that a piston reaches in the cylinder.
Bore: The diameter of each cylinder in an engine.
Stroke: The distance travelled by the piston from BDC to TDC.
Displacement: The circular area of one cylinder multiplied by its stroke multiplied by the
number of pistons. This is also sometimes referred to as the swept volume.
Compression Ratio: The ratio of total cylinder volume to combustion chamber volume.
Work: A force applied over some distance.
Power: The rate at which work is performed.
Horsepower: A unit of standard measure for power in the english system.
Kilowatt: A unit of standard measure for power in the metric system.
Torque:The amount of twisting force that is produced by an engine.
Indicated Horsepower: The amount of power that an engine is theoretically able to produce.
Brake Engine Horsepower: A measurement of the actual power that is available for useful work
from an engine.
Dynamometer: A device used to measure the torque and horsepower output of an engine.
Mechanical Efficiency: The ratio of brake power to indicated power. Gives an idea of how
much power is lost due to friction in the engine.
Thermal Efficiency: The degree to which an engine is able to convert the energy in the fuel into
heat energy to cause the pistons to turn the crankshaft.
Volumetric Efficiency: The capability of an engine is of filling the cylinder with air on the intake
stroke compared to the cylinder being completely filled with air at
atmospheric pressure.
Unit 1 1 Engine Fundamentals
Lesson 3, Exercise 1.3.1
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Unit 1 3 Engine Fundamentals
Lesson 3, Exercise 1.3.1
Write the equations for calculating the following:
Displacement: Displacement = x r2 x L x n
Where...
= 22/7
r2 = radius x radius
radius = 1/2 bore
L = stroke
n = number of cylinders in the engine
Horsepower: HP = T x RPM / 5252
Using the Glossary of Terms, define the following:
Force: The action of one body on another tending to change the state of motion of the body
acted upon.
Heat: Form of energy, the addition of which, causes substances to rise in temperature; energy
associated with random motion of molecules.
British Thermal Unit (BTU): The amount of heat required to raise 1 lb of water from ice to
water at standard atmospheric pressure.
Brake Mean Effective Pressure (BMEP): Mean effective pressure acting on the piston which
would result in the given brake horsepower output, if
there were no losses due to friction, cooling, and
exhaust. This is equal to the mean indicated pressure
multiplied by the mechanical efficiency of the engine.
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Unit 1 4 Engine Fundamentals
Lesson 3, Exercise 1.3.1
Unit 1, Exercise 1.3.1
Define the following terms:
Bore:
Stroke:
TDC - Top Dead Center:
BDC - Bottom Dead Center:
Displacement:
Compression Ratio:
Work:
Atmospheric Pressure:
Power:
Mechanical Efficiency:
Horsepower:
Thermal Efficiency:
Kilowatt:
Indicated Horsepower:
Friction:
Torque:
Brake Engine Horsepower:
Dynamometer:
Volumetric Efficiency:
Inertia:
Fuel Efficiency:
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Unit 1 5 Engine Fundamentals
Lesson 3, Exercise 3.1
Write the equations for calculating the following:
Displacement:
Horsepower:
Using the Glossary of Terms, define the following:
Force:
Heat:
British Thermal Unit (BTU):
Brake Mean Effective Pressure (BMEP):
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Unit 1- 1 Engine Fundamentals
Instructor Copy Quiz 1.3.1
CATERPILLAR ENGINE FUNDAMENTALS
Unit 1 Quiz
Circle the best answer or fill in the blanks. Name .
1. The crankshaft in a Caterpillar 3406B is:
A. hardened at the journals only
B. totally hardened
2. Which engines require MSHA certification?
A. MarineB. Underground Mining
C. On-Highway Truck
3. Which of the following Caterpillar on-highway truck engines are considered medium duty
(mid-range) class?
A. C-10
B. 3306C
C. 3126B
D. 3406C
4. What three factors are necessary to create combustion?
air fuel heat
5. How does the 4 stroke diesel engine combustion process differ from 4 stroke gasoline
engines?
Ignition process - diesel uses compression, gasoline uses spark to ignite fuel
6. Name the 4 cycles of Caterpillar diesel engine operation.
intake compression
power exhaust
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Unit 1- 2 Engine Fundamentals
Instructor Copy Quiz 1.3.1
7. Four strokes of the piston equal how many revolutions of the crankshaft?
A. 1
B. 2
C. 4D. 8
8. During the four-stroke cycle, the piston is moving toward TDC (Top Dead Center) during
what two strokes?
A. Compression and exhaust
B. Intake and power
C. Intake and exhaust
D. Compression and power
9. What does this formula represent?
RPM x Torque
5252
A. BTU
B. % Torque Rise
C. Horsepower
D. Thermal Efficiency
10. 317 kilowatts is equivalent to how many horsepower?
A. 400
B. 425
C. 236
11. In a Caterpillar 3406 engine, when piston #1 is at TDC compression, piston #6 is at:
TDC exhaust
12. Horsepower is defined as:
A. work done in a given period of time.
B. twisting effort of the crankshaft in an engine.
C. the displacement of an engine in liters.
D. the energy derived from burning dried horse manure
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Unit 1- 3 Engine Fundamentals
Instructor Copy Quiz 1.3.1
13. Engine displacement is defined as:
A. weight of the engine.
B. length of the engine when it is installed.
C. total volume that is displaced by all pistons making one stroke each.D. moving the engine from one place to another.
14. Compression ratio is defined as:
A. ratio of compression pressure to firing pressure.
B. ratio of volume in a cylinder with the piston at Bottom Dead Center compared to
volume at Top Dead Center.
C. ratio of crankcase pressure to atmospheric pressure.
D. ratio of turbocharger boost pressure to exhaust backpressure.
15. Explain the difference between "Flywheel Horsepower" and "Wheel Horsepower".
Flywheel horsepower is measured at the flywheel, wheel horsepower is measured at the
wheels of a vehicle (drivetrain losses will make wheel hresepower less)
16. What section of a Service Manual has step-by-step procedures for setting intake and
exhaust valves on a Caterpillar engine?
Testing and adjusting
17. An industrial engine application that requires the engine to operate at rated load and speed
up to 100% of the time is considered:
A. A Rating
B. B Rating
C. C Rating
D. D Rating
E. E Rating
18. Which components in a diesel engine convert reciprocating motion to rotary motion?
A. Camshaft and crankshaft
B. Connecting rod and crankshaft
C. Piston and crankshaft
D. Crankshaft and flywheel
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Unit 1- 4 Engine Fundamentals
Instructor Copy Quiz 1.3.1
19. An industrial engine application that requires the engine to operate at rated load and speed
for a short time is considered:
A. A Rating
B. B RatingC. C Rating
D. D Rating
E. E Rating
20. A "parent bore block" is:
A. a cylinder block with removable wet cylinder liners.
B. usually used in heavy duty engine designs.
C. a cylinder block with cylinders bored by your father.
D. a cylinder block where the cylinders are bored directly into the cylinder block
material.
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Unit 1- 1 Engine Fundamentals
Student Copy Quiz 1.3.1
CATERPILLAR ENGINE FUNDAMENTALS
Unit 1 Quiz
Circle the best answer or fill in the blanks. Name____________________________
1. The crankshaft in a Caterpillar 3406B is:
A. hardened at the journals only
B. totally hardened
2. Which engines require MSHA certification?
A. MarineB. Underground Mining
C. On-Highway Truck
3. Which of the following Caterpillar on-highway truck engines are considered medium duty
(mid-range) class?
A. C-10
B. 3306C
C. 3126B
D. 3406C
4. What three factors are necessary to create combustion?
________________ _________________ _________________
5. How does the 4 stroke diesel engine combustion process differ from 4 stroke gasoline
engines?
________________________________________________________
________________________________________________________
6. Name the 4 cycles of Caterpillar diesel engine operation.
_____________________ _____________________
_____________________ _____________________
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Unit 1- 2 Engine Fundamentals
Student Copy Quiz 1.3.1
7. Four strokes of the piston equal how many revolutions of the crankshaft?
A. 1
B. 2
C. 4D. 8
8. During the four-stroke cycle, the piston is moving toward TDC (Top Dead Center) during
what two strokes?
A. Compression and exhaust
B. Intake and power
C. Intake and exhaust
D. Compression and power
9. What does this formula represent?
RPM x Torque
5252
A. BTU
B. % Torque Rise
C. Horsepower
D. Thermal Efficiency
10. Define Torque Rise in a diesel engine.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
11. In a Caterpillar 3406 engine, when piston #1 is at TDC compression, piston #6 is at:
______________________________________________________________
12. Horsepower is defined as:
A. work done in a given period of time.
B. twisting effort of the crankshaft in an engine.
C. the displacement of an engine in liters.
D. the energy derived from burning dried horse manure
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Unit 1- 3 Engine Fundamentals
Student Copy Quiz 1.3.1
13. Engine displacement is defined as:
A. weight of the engine.
B. length of the engine when it is installed.
C. total volume that is displaced by all pistons making one stroke each.D. moving the engine from one place to another.
14. Compression ratio is defined as:
A. ratio of compression pressure to firing pressure.
B. ratio of volume in a cylinder with the piston at Bottom Dead Center compared to volume
at Top Dead Center.
C. ratio of crankcase pressure to atmospheric pressure.
D. ratio of turbocharger boost pressure to exhaust backpressure.
15. Explain the difference between "Flywheel Horsepower" and "Wheel Horsepower".
_____________________________________________________________
_____________________________________________________________
16. What section of a Service Manual has step-by-step procedures for setting intake and exhaust
valves on a Caterpillar engine?
_____________________________________________________________
17. An industrial engine application that requires the engine to operate at rated load and speed
up to 100% of the time is considered:
A. A Rating
B. B Rating
C. C Rating
D. D Rating
E. E Rating
18. Which components in a diesel engine convert reciprocating motion to rotary motion?
A. Camshaft and crankshaft
B. Connecting rod and crankshaft
C. Piston and crankshaft
D. Crankshaft and flywheel
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Unit 1- 4 Engine Fundamentals
Student Copy Quiz 1.3.1
19. An industrial engine application that requires the engine to operate at rated load and speed
for a short time is considered:
A. A Rating
B. B RatingC. C Rating
D. D Rating
E. E Rating
20. A "parent bore block" is:
A. a cylinder block with removable wet cylinder liners.
B. usually used in heavy duty engine designs.
C. a cylinder block with cylinders bored by your father.
D. a cylinder block where the cylinders are bored directly into the cylinder block material.