Download Introduction-to-Small

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1680 Christian Huygens develops a internal
combustion engine that utilized gunpowder
as a fuel source
1698 Thomas Savery developed the Savery
pump utilizing steam to force water from the
ground
1712 Thomas Newcomen develops a steam
engine in which many components are still
used in engines today including the piston in
a cylinder as well as valves and pivot arms
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1801 Eugene Lebon developed and internal
combustion engine that used coal gas ignited by
an electric ignition source
1859 Etienne Lenoir introduces an internal
combustion engine that mixed coal gas and air
together
 It was at this same time that there was an
resurgence in steam power that put the internal
combustion engine on standby until 1862
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1862 Nikolaus Otto and Eugene Lange designed
and built the first gasoline engine
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1876 Otto successfully modified his gasoline
powered engine and introduced the four-stroke
cycle engine. Known as the Otto cycle.
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1892 Rudolf Diesel patented an new type of
internal combustion engine that ignited fuel
under high pressure. Later to become know as
the diesel engine
 The first diesel engines used coal dust as a fuel source
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Identify the key differences between a 2Stroke and 4-Stroke engine
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Identify the four strokes of a 4-cylcle engine
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Identify the two strokes of a 2-cycle engine
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Identify the five events of both the 4 and 2
cycle engine
Engine
classification
External
Combustion
Two Stroke
Internal
Combustion
Ignition
Ignition
Spark
Compression
(Gasoline)
(Diesel)
Four Stroke
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A compression ignition engine uses
compression of the air-fuel mixture to ignite
the mixture
 Most commonly use diesel fuel
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A spark ignition engine uses an electrical
spark to ignite the air-fuel mixture
 Most commonly use gasoline as a fuel source
Intake
Exhaust
Compression
Power
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Utilizes four strokes to complete one operating
cycle
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Four Stroke Engine Completes five distinct
events during each cycle
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Intake
Compression
Ignition
Power
Exhaust
Piston
moving
down
creates
vacuum in
cylinder
drawing in
air-fuel
mixture
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Piston
moving up
compresses
air-fuel
mixture
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Air-fuel
mixture
ignited by
spark plug
forces
piston down
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Piston
moving
up forces
out
exhaust
gases
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Intake/Compression
Power/Exhaust
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Utilizes two strokes to complete one operating
cycle
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Completes the same five events as the four
stroke engine
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Intake
Compression
Ignition
Power
Exhaust
Air-fuel mix enters
combustion chamber
through transfer
ports
 piston moving up
compresses air-fuel
mix
 air-fuel mix drawn
into crankcase from
intake port
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Air-fuel mix ignited
by spark plug
forces piston down
compressing airfuel mix in
crankcase
Exhaust gas
discharged through
exhaust port
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Two forms of energy:
 Potential energy
 Kinetic energy
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Potential energy is stored energy
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Kinetic energy is energy in motion
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All internal combustion engines operate by
utilizing basic principles of
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Heat
Force
Pressure
Torque
Work
Power
Chemistry
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Definition
 Heat is kinetic energy caused by matter in motion
within a substance
Heat added to a substance causes velocity to
increase
Heat removed from a substance causes velocity to
decrease
We see this principle in action during the
compression and power stroke
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When the air-fuel mixture is compressed and
heated up it changes the mixture to a
gaseous state
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This prepares the air-fuel mixture for efficient
combustion
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Force is anything that changes or tends to
change the state of rest or motion of a
body(anything with mass)
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For example if you push on an object a force
has been exerted on that object
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Force is measured in pounds(lb) in the English
system or Newton's(N) in the metric system
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Force does not always result in movement of
an object
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Force can be applied in different ways to
produce pressure, torque or work
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Pressure is a force acting on a unit of area
Area is the number of unit squares equal to
the surface of an object
When force and area are known pressure is
found by applying the formula
P=F/A
 P= pressure (in lb/sq inch)
 F= force (in lb)
 A= area (in sq in.)
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In an internal combustion engine pressure is
applied to the top of the piston head.
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Piston motion is transferred from the
connecting rod to the crankshaft .
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How much pressure is exerted if a force of
2000 pounds is applied to an area of 4.91
square inches?
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P=F/A
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P=2000/4.91
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P=407.33 psi
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What is the pressure exerted if 60 pounds of
force is applied to an area of 4 square inches?
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What is the pressure if a 1000 pound force is
applied to an area of 5 square inches?
P=F/A
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P=60/4
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P=15 psi
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P=1000/5
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P=200 psi
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Torque is a force acting on a perpendicular
radial distance from a point of rotation
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Torque is equal to force times distance
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The result is a twisting or turning force
expressed as pound feet (lb-ft) or in newtonmeters (Nm)
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When force and radius are know, torque is
found by applying the formula:
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T=F*r
 T=torque (in lb-ft or Nm)
 F= force (in lb)
 r= radius (distance)
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What is the torque developed if a 60 lb force
is applied at the end of a 2 foot lever arm?
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T=F*r
T=60*2
T=120 lb-ft
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The same amount of torque would be applied
if 120 lb. force was placed at the end of a 1’
lever
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T=F*r
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You have a 2’long wrench and apply 25 lbs of
force how much torque has been applied?
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How could you apply the same amount of
torque but apply less force?
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Lever- a simple machine that consists of a
rigid bar that pivots on a fulcrum (pivot point)
with both resistance and effort applied
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Main purpose is to overcome large resistance
with reduced effort
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One of the main examples of a lever in a small
engine is the crankshaft
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Provides lever distance from the center line
of the crankshaft
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Converts force applied by the piston to result
in rotation of the crankshaft
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Stroke is the linear distance a piston travels
inside the cylinder from the cylinder head end
to the crankshaft end
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Stroke is determined by throw of the
crankshaft
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Throw is the measurement on a crankshaft
from the centerline of the crankshaft to
centerline of the connecting rod (offset)
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Work is force applied through a parallel
distance causing linear motion.
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Work occurs only when the force results in
motion
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Work is measured in lb-ft or Nm
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Requires only enough force to complete the
desired task
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If additional force is applied that force will
result in acceleration
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Work and torque are similar
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The only true difference is torque does not
always result in perceptible motion
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When force and distance are known, work is
found by applying the formula:
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W=F*D
 W= work
 F= force(in lb)
 D=distance (in lb)
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What is the amount of work performed if a
mower pulled a container that weighed 330 lb
100 feet?
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W= 330*100
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W=?
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How much work is performed when lifting a
72 lb engine from the floor to the top of a 3
foot high workbench?
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W=F*D
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Power is the rate at which work is done.
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Power adds in a time factor
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Power can be expressed in several ways
 Force
 Distance
 speed
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Typical examples include
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Horsepower
Watts (W)
Kilowatt (kWh)
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Both watt and horsepower measure how fast
work is completed
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When force and distance are known, power is
found by applying the following
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P=W/T
 P=power (in lb-ft/min)
 W= work (force*distance)(in lb-ft)
 T= time (in min)
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P=W/T
P=power (in lb-ft/min)
W= work (force*distance)(in lb-ft)
T= time (in min)
What is the power output of an engine that
performs 100,000 lb-ft of work in 6 minutes?
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P=W/T
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P=100,000/6
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P= 16,666.67 lb-ft/min
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Horsepower (HP) is a unit of power equal to
746 watts (W) or 33,000 lb-ft per minute, 550
lb-ft per second
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HP is used to rate and rank the power
produced by an engine based on a finite
engine speed.
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HP was developed by James Watt in the
1800’s
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Developed HP to give a reference of power to
the steam engine that he produced for the
mining industry
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He based his observations of power on the
average horse
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He determined that an average horse could
move/lift 33,000 lb on a linear plane, 1’in 1
minute.
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This is the basis for the standard 550 lb-ft per
second that is still used today
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Horsepower is found by applying the
following
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HP=W/T*33,000
 HP= horsepower
 W=work (force*distance) in lb-ft
 T=time ( in min)
 33,000=HP constant (in lb-ft)
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What is the horsepower rating of an engine
that produces 412,500 lb-ft in 2.5 minutes?
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HP=W/T*33000
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HP=?
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HP=412,000/2.5*33000
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HP=412,000/82,500
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HP=5 Hp