Transcript INTERNAL COMBUSTION ENGINE - Area10FFA

CHAPTER 1
ENGINE CLASSIFICATION
 An engine is a machine that converts a form of energy
into mechanical force.
 External combustion engine is an engine that
generates heat energy form the combustion of a fuel
outside the engine. Ex. Steam engine
 Internal combustion engine is an engine that
generates heat energy from the combustion of a fuel
inside the engine. Ex. Gasoline engine
ENGINE CLASSIFICATION
 Small engine is an internal combustion engine that
converts heat energy from the combustion of a fuel
into mechanical energy generally rated up to 25
horsepower.
 Classified further by ignition, number of strokes,
cylinder design, shaft orientation and cooling systems.
IGNITION
 Spark ignition or compression ignition engines are
based on how fuel is ignited.
 Spark ignition engines commonly use gasoline
 Compression engines use diesel fuel.
 Both engines are available in 4-stroke or 2-stroke
cycle engine.
NUMBER OF STROKES
 Small engines are classified as either 4-stroke or 2-
stroke engines.
 4-stroke engine utilizes four strokes to complete one
operating cycle of the engine.
 2-stroke engine utilizes two strokes to complete one
operating cycle of the engine.
NUMBER OF STROKES
 Both engines complete five distinct events during a
cycle.
 1. intake
 2. compression
 3. ignition
 4. power
 5. exhaust
CYLINDER DESIGN
 Small engine typically contain one or two cylinders.
 Cylinder orientation can be Vertical
 Horizontal
 Slanted depending on the axis of the cylinder
CYLINDER DESIGN
 In multiple cylinder engines can be “V”, horizontal
opposed, or in-line configuration.
 Usually cylinder orientation are selected for its power
and application.
 Horizontal opposed engines have low profile produces
a low degree of vibration.
 All engines provides ease of manufacturing but
requires more space.
SHAFT ORIENTATION
 Shaft orientation is the axis of the shaft.
 Vertical shaft engines commonly are used in push
lawnmowers. Blade is directly attached to the shaft and
rotates parallel to the ground.
 Horizontal shaft engines commonly are used with
generators, tillers, pumps, augers, etc. Power is transfer
to a driven component.
COOLING SYSTEM
 In a combustion engine approximately 30% of the
energy released is converted to useful work.
 Remaining energy is lost in the form of heat to:
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cooling air(30%)
Exhaust systems(30%)
Radiation & friction (10%)
HISTORY
 1680 - Christain Huygens developed the first internal
combustion engine.
 Next 100 years, inventors focused on steam engines.
 1801- Eugene Lenoir developed the first internal
combustion engine using coal gas with electric
ignition.
 1859- Etienne Lenoir mixed coal gas and air together
HISTORY
 1862 – Nikolaus Otto developed the first successful
gasoline engine.
 1892 – Rudolf Diesel patented a new type of internal
combustion reciprocating engine that ignited the fuel
by high compression. Today is is known as the Diesel
engine.
 1920 – Briggs and Stratton Corporation introduced a
portable Model P engine operating at 2200 rpm and
developed 1HP.
HISTORY
 1931 – B&S produced a low-profile L-head ½ HP Model
Y engine used under washing machine tubs.
 1953 – B&S produced the first die-cast aluminum block
small engines. First 50 million engines produced
between 1924-1967.
 Took only 8 years to produced the next 50 million.
Today, B&S engines are widely used in agricultural
applications.
ENERGY CONVERSION PRINCIPLES
 All internal combustion engines exhibits and convert
different forms of energy.
 Energy is the resource that provides the capacity to do
work.
 Potential energy is stored energy
 Kinetic energy is energy of motion
(Ex. Converts the potential engine in gasoline into kinetic
energy of a rotating shaft.
ENERGY CONVERSION PRINCIPLES
 The operation of an internal combustion engine is
based on basic energy conversion principles.
 All internal combustion engines operate by utilizing
basic principles of:
Heat
Force
Pressure
torque
work
power
chemistry
HEAT
 All matter is composed of atoms and molecules
that are in a constant state of motion.
 Heat is kinetic energy.
 Heat added to a substance causes molecule
velocity to increase causing an increase in
internal energy. Heat removed from a substance
causes an decrease of internal energy. Ex. Events
occurring during compression and power stroke of an
engine.
HEAT TRANSFER
 Three methods of heat transfer;
1. Conduction
2. Convection
3. radiation
HEAT TRANSFER
 Conduction is heat transfer that occurs atom to atom
when molecules come in direct contact with each
other, and through vibration, kinetic energy is passed
from one to the other.
 Heat conduction occurs in small engines through
the medium of lubricating oil. Oil comes in direct
contact with engine parts that have a much high
temperature than the oil. The oil conduct the heat
away from the part and into the crankcase.
HEAT TRANSFER
 Convection is heat transfer that occurs when heat is
transferred by currents in a fluid.
 Heat transfer by convection occurs in a liquid-cooled
engine radiator.
Warm liquid from the engine is pumped into the top
of the radiator. The liquid gives up its heat to air
as it passes through the radiator. Cooler liquid is
then drawn from the bottom and returned to the
engine.
HEAT TRANSFER
 Radiation is heat transfer that occurs as radiant
energy without a material carrier.
 Radiant energy waves move through space without
producing heat until it comes in contact with a opaque
object.
Heat radiation occurs in small engines as the
engine block, cylinder head and other
components have heat passed through them into
the atmosphere.
TEMPERATURE
 Temperature is the measurement of degree or intensity
of heat.
 A common unit for quantity of heat measurement is
the Btu (British Thermal Unit)
 Btu is the amount of heat energy required to raise the
temperature of 1 pound of water 1 degree F.
 Calorie is the amount of heat energy required to
change the temperature of one gram of water 1 degree
C.
Temperature Scales
 Temperature is commonly expressed in the small
engine industry using the Fahrenheit or Celsius scale.
 Freezing points / boiling points–
 32° F freezing & 212° F boiling
 0° C freezing & 100° C boiling
Temperature Scales
 Formulas
 °C = °F – 32
1.8
°F = (1.8 X °C) + 32
FORCE
 Force is anything that changes or tends to change the
state of rest or motion of a body. A body is anything
with mass.
 Force is measured in pounds(lbs) or in newtons(N)
PRESSURE
 Pressure is a force acting on a unit of area. Area is
the number of unit square equal to the surface of an
object.
 When force and area are known, pressure is found by
applying the formula. P=pressure(psi); F=force(in lb);
A=area(sq in.)
P= F
A
PRESSURE
Example: What is the pressure exerted if a 60 lb force is
applied to an area of 4 sq. inches?
P=F
A
P = 60 = 15 psi
4
TORQUE
 Torque is a force acting on a perpendicular radial
distance from a point of rotation. It is equal to force
times radius.
 When force and radius(distance) are known, torque is
found by applying the formula:
T=Fxr
T = torque (in. lb or ft. lb)
R = force (in. lb)
R = radias (distance)
TORQUE
 What is the torque developed if a 60 lb. force is
applied at the end of a 2-foot lever arm?
T=Fxr
T = 60 x 2
T = 120 ft. lbs
 Lever is a simple machine that consists of a rigid bar
that pivots on a fulcrum(pivot point) with both
resistance and effort applied.
Levers
 Lever is a simple machine that consists of a rigid bar
that pivots on a fulcrum(pivot point) with both
resistance and effort applied.
 The purpose is to obtain mechanical advantage to
overcome a large resistance with reduced effort.
 This principle is used on several rigid and semi-rigid
components in a small engine. Example-Crankshaft
WORK
 Work is the force applied through a parallel distance
causing linear motion. Work occurs only when the
force results in motion.
 When force and distance are known, work is found by
applying the formula:
W=FXD
W = work
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F = force (lb)
D=distance (ft)
WORK
 Example of work: What is the amount of work
performed if a horse pulled a container that weighed
330 lbs 100 feet?
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W=FXD
W = 330 X 100
W= 33,000 lbs-ft
POWER
 Power is the rate at which work is done.
 Power adds in a time factor.
 Therefore, power is work divided by time.
 Power can be expressed in several ways—force,
distance and speed.
 Examples: Power ratings include horsepower, watt or
kilowatt. Both horsepower and watt measure how fast
work is done.
POWER
 When force and distance are known, power is found by
applying the formula:

P=W
T
P= power (ft.lb/min
W= force x distance (ft.lb)
T= time (minutes)
POWER
 Example: What is the power output of an engine that
performs 100,000 ft lbs of work in 6 minutes?
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P=W
T
P = 100,000
6
P = 16,666.67 ft.lbs/minute
HORSEPOWER
 Horsepower (HP) is a unit of power equal to 746 watts
or 33,000 ft lbs. per minute.
 Horsepower is commonly used to rate and rank the
power produced by an engine based on a finite engine
speed.
 Note: The evolution of HP as a measurement used today goes
back to the history of the combustion engine. James Watt
realized that a steam engine produced more power than anyone
human. He needed a reference point to compare the power of his
new steam engine. He selected a horse and determined that a
horse could move/lift 33,000 lbs on a linear plane, 1 foot per 1
minute. This was the basis for the standard used today.
HORSEPOWER
 Horsepower is found by applying the formula:
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HP =
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HP = horsepower
W = work (force x distance) (ft.lb)
T = time (minutes)
33,000 = HP contant (ft lb)
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W
.
T x 33,000
Determining Horsepower
 What is the horsepower of an engine that produces
5,940,000 ft lbs in 10 minutes?
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HP = _____W
.
T x 33,000
HP = 5,940,000
10 x 33,000
HP = 5,940,000
330,000
HP = 18 horsepower
QUESTION?
 What is the horsepower rating of an engine that
produces 412,500 ft lbs in 2-1/2 minutes?
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ANSWER? _________________________
CHEMISTRY
 All internal combustion engines utilize some form of
fossil (hydrocarbon) fuel as a source of energy.
Combustion chemistry involves the combining of
hydrocarbon fuel with oxygen from the atmosphere.
 C8H18 + 12½02 + 47N2 = Air-fuel mixture
Gasoline + oxygen + nitrogen
 8CO2 + 9H2O + 47N2 = Exhaust gases
carbon dioxide + water +nitrogen