ENGR 1611 – Concepts I
Topic: IC Engine
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Water timer Report Feedback
• Common mistakes:
• Grade distribution
• A=
• B=
• D=
(make sure you redo)
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Outline
• What is an internal combustion (IC) engine?
• What are the important parts of an engine?
• What is the difference between a 4-stroke and
a 2-stroke engine?
• What are the strokes of each?
• Description of lab activities and outcomes.
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Combustion Engines
• Converts combustion (burning, heat energy) to
mechanical energy
• External – combustion occurs externally (e.g., steam
engine where fire is away from moving parts and steam is
in direct contact)
• Internal – combustion occurs internally (i.e., fire is in direct
contact with the moving parts.
http://www.howstuffworks.com
http://www.lambocars.com/framed/highres/bugattie3.htm
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Key Concepts
• Internal combustion occurs in the engine block
• The change of heat energy to mechanical motion is based on
the physical law that gas will expand upon heating
• Gas Expansion causes piston to move down
• Linear piston motion causes rotation of the crank shaft which
connects to the transmission
0°C
20°C
40°C
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Key Concepts
• Internal combustion occurs in the engine block
• The change of heat energy to mechanical motion is based on
the physical law that gas will expand upon heating
• Gas Expansion causes piston to move down
• Linear piston motion causes rotation of the crank shaft which
connects to the transmission
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Key Concepts
• Internal combustion occurs in the engine block
• The change of heat energy to mechanical motion is based on
the physical law that gas will expand upon heating
• Gas Expansion causes piston to move down
• Linear piston motion causes rotation of the crank shaft which
connects to the transmission
• 4-Bar mechanism
• Simple and robust
• Lengths of the links control motion
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Throttle
(used to control air flow)
Engine Parts
Carburetor
(mixes fuel and air)
Intake Valve
Exhaust Valve
(entry port for fuel and air)
(exit port for fuel and air)
Piston
And Piston Rings
(seals gases within cylinder
and keeps oil out)
Connecting Rod
(converts linear motion to radial)
Engine Block
(confines gases)
Crank Shaft
Oil
(lubricates moving parts)
(distributes power)
Camshaft
(controls timing)
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Four Stroke
http://library.thinkquest.org
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Valve Timing
• Combustion occurs 1 time in 4 strokes
• 2 revolutions are required for 4 strokes
• Valves controlled by the camshaft
• Driven by gears off of the crankshaft
• See http://www.howstuffworks.com/camshaft1.htm
Pros and Cons
Pro:
Con:
efficient combustion
complex therefore expensive and heavy
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Two Stroke
http://www.howstuffworks.com/two-stroke2.htm
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Valve Timing
• Combustion occurs every revolution or 2 strokes
• Power stroke forces new air and fuel into the cylinder
• Piston motion itself drives the port opening and closing
Pros and Cons
Pro:
low cost engine
used in chain saws, weedwackers
Con:
inefficient combustion
poor emissions (scavenging)
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Comparison
• Four Strokes
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Produce more power at lower RPMs
More complete and efficient combustion
Less noise pollution
Multi-cylinder engines
• Two Strokes
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Produce more power at higher RPMs
Less efficient combustion à higher emissions
Cheaper, conducive to smaller applications
Weighs less
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IC Engine Lab
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Laboratory exercise
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Work in teams of 3 (assigned not chosen)
Perform partial disassembly of a 4-stroke engine
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Some will be lawn mowers others generators
Do not remove gears!
Will reassemble before end of class period
Goal to prepare a formal report
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Due next Thursday
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Report content
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Abstract
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Executive summary – 1 paragraph containing 4 to 5
sentences
Summarizes motivation, procedure and discovery
Introduction
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1 to 2 pages
History
Motivation for work
Reviews theory – summarize lecture or chapter 12
Outlines contents of report
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Report content
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Assembly Drawings of The Mechanism
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Description of Mechanism
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Subassembly of cylinder and piston
Subassembly of camshaft and gears
Detailed drawings of key components (see grade sheet)
At least 80% of drawings must be from CAD
Using part numbers and names used in assembly drawing
describe parts function, why is it necessary etc.
Discussion
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Questions from the assignment sheet.
• write question out then provide complete answer in
homework style format
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Report Content
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All report must be typed!!
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Team evaluation
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Completed by the elected team leader
Leader completes the team member evaluation on the grade
sheet
Leaders will provide a typed sheet that lists each persons task
responsibilities and is signed by each member including the
leader
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Every one must attend Monday lecture from 10-11 in
309 for peer review. The session will focus on the
abstract, introduction, and description sections.
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Reports are due start of lab next Thursday
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