Small Gasoline Engines

1
Small Gasoline Engines
2
Engine

• Define Engine

Are these engines?
What is the primary difference between these
engines and modern engines?
3
Heat Engine

• How does modern engines use heat?

4
Two general categories based on how the heat is
used.
External combustion engine
Internal combustion engine
5
Internal Combustion Engines
6
Small Engine Development(pg 5)

• Year Engine Designer/developer
• 1680 Gunpowder Christian Huygens
• 1698 Savery Pump Thomas Saverly
• 1712 Newcomen Steam Thomas Newcomen
• 1763 Watt Double-acting steam James Watt
• 1801 Coal gas/electric ignition Eugene Lebon
• 1802 High pressure steam Richard Trevithick
• 1859 Pre-mixed fuel and air Etienne Lenoir
• 1862 Gasoline Nikolaus Otto
• 1876 Four cycle gasoline Nikolaus Otto
• 1892 Diesel Rudolf Diesel
• 1953 Die-cast aluminum BS

7
Internal Combustion--Intro

• Engine designs can be classified by
• Size
• Ignition system
• Strokes per cycle
• Cylinder orientation
• Crankshaft orientation
• Control system
• Cooling system

8
1. Engine Size
Engines are available in a wide range of sizes.
Industry definition A small engine is an
internal combustion engine rated up to 25
horsepower.
9
1. Size - Largest

• The Wartsila-Sulzer RTA96-C turbocharged
  two-stroke diesel engine is the most powerful and
  most efficient prime-mover in the world today.

The cylinder bore is just under 38" and the
stroke is just over 98". Each cylinder displaces
111,143 cubic inches (1,820 liters) and produces
7,780 horsepower.
Total displacement comes out to 1,556,002 cubic
inches (25,480 liters) for the fourteen cylinder
version.
10
1. Size - Smallest

• Not much bigger than a stack of pennies, the
  "mini engine" is the first engine of its size to
  deliver power on a continuous basis.
• Currently will produce 2.5 watts of electricity
  (0.00335 hp).
• Uses 1/2 fluid ounce of fuel per hour

11
2. Ignition

• Spark ignition

Compression ignition
What is the primary difference?
12
3. Cycles

• Four stroke

Two stroke
Name one common use for each type.
13
4. - Cylinder Orientation

• There is no limit on the number of cylinders that
  a small engines can have, but it is usually 1 or
  2.

Four common cylinder orientations for small
engines
Vertical
Slanted
Horizontal
Multi position
Give an example of a use for each.
14
4. - Cylinder Orientationcont.
Three common cylinder configuration in multiple
cylinder engines
V
Horizontally opposed
In-line
Can you identify one application for each of
these types?
15
5. Crankshaft Orientation
Small gas engines use three crankshaft
orientations
Multi-position
Horizontal
Vertical
Identify a use for each one.
16
6. Controls

• Traditionally engines are controlled by
  mechanical means.
• Governor
• Throttle
• Choke
• Etc.
• Honda has an engine with an electronic control
  unit (ECU).

• ECU - Electronic Control Unit
• Monitors and controls engine functions including
  Throttle, Choke, Ignition Timing, Oil Alert
• Offers programmable governor and throttle modes
  for unprecedented flexibility and diagnostic LED
  for trouble shooting
• Stepper motors precisely control throttle and
  choke position

17
7. Cooling System

• Small engines use two types of cooling systems
• Air
• Water

Why does an internal combustion engine need a
cooling system?
Why what are the advantages and disadvantages of
both systems?
18
How is excess heat moved within and removed from
the engine?
7. Cooling Systemcont.
19
7. Cooling systemcont.

• Which one(s) of the heat transfer methods are
  used by the following engine systems?
• Cooling
• Lubrication
• Fuel

20
Physical Principles of Engines
21
Energy

• Energy is the capacity for doing work.

What are the two forms of energy?
Which form are these?
22
Boyles Laws

• Boyles Law the volume of gas varies inversely
  with the pressure.
• Any confined gas will double its pressure when
  the volume is decreased by one half.

Small gas engines use a compression ratio of 81.
Theoretical compression pressure. Using an
atmospheric pressure of 14.7 psi and a
compression ratio of 81 the theoretical
compression pressure is 117.6 psi
Note The actual cylinder press will be
different because of the losses that occur and
the complex relationship between gas pressure and
temperature.
23
Charles Law

• The pressure and temperature of a confined gas
  are directly proportional.

The increase in temperature can be approximated
by
For an engine with a 81 compression ratio and an
initial temperature of 72 oF, the compression
temperature will be
An engine with a 211 compression ratio and an
initial temperature of 72 oF, the compression
temperature will be
24
Force

• Anything that changes or tends to change the
  state of rest or motion of a body.

• A force can result in pressure, torque or work,
  depending on how it is applied.

25
Force--Pressure
Pressure is a force acting on a unit of area.

• The cylinder pressure is not constant.
• Increases during compression.
• Sharp spike after combustion
• Decreases through power stroke

How high can the pressure reach in a combustion
chamber?
26
ForcePressurecont.

• In an engine the pressure produced in the
  combustion chamber is converted to a force.
• The pressure is applied uniformly to all
  surfaces, including the head of the piston.

27
Torque

• A force acting on the perpendicular radial
  distance from a point of rotation.

To (lb-ft) Force x Radius
Problem Determine the amount of torque that will
be produced for an engine that has an average
combustion pressure of 250 psi, a 2.75 inch bore
and 1.25 inch throw.
28
Power

• Power is the rate of doing work.

Problem How much power is an engine producing if
the torque is 154 lb-ft and the engine operates
at 3,000 RPM.
29
Horsepower

• A unit of power developed by James Watt to
  provide a basis for comparing the amount of power
  produced by horses and other engines.

• 1 Hp 33,000 ft-lb/min

Problem How many horsepower is an engine
producing if the power is 46,200 ft-lb/min?
30
The End