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06-10-2015
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ME 311: Dynamics of Machines and
Mechanisms
Lecture 25: Multi Cylinder Engines: Part 3
By
Suril Shah
Mechanical Department
IIT Jodhpur
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Outline
• Summary
• Vee engine configuration
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Multicylinder Engine Designs
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http://gifsgallery.com/engine+cylinder+gifhttp://gifsgallery.com/engine+cylinder+gif
http://gothamknowledge.tumblr.com/post/776545
66480/rocketumbl-engine-gif-hypnotizing-i-love-it
https://en.wikipedia.org/wiki/Rotary_en
gine
THE CRANK PHASE DIAGRAM
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Phase angles of 0, 90, 180, 270°
SHAKING FORCES IN INLINE ENGINES
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SHAKING FORCES IN INLINE ENGINES
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INERTIA TORQUE IN INLINE ENGINES
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SHAKING MOMENT IN INLINE ENGINES
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SHAKING MOMENT IN INLINE ENGINES
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EVEN FIRING
• Creating firing pattern evenly spaced in time
• The optimum delta phase angle will be:
• Power stroke angles (ψ) : angles in the cycle at which the cylinders fire.
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Two-Stroke Cycle Engine, φj: 0,90,180,270°
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Four-stroke inline four-cylinder engine
crank phase diagram (φj: 0,90,180,270)
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Four-stroke inline four-cylinder engine
crank phase diagram (φj: 0,180,0,180)
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Solution
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Four-stroke inline four-cylinder engine (φj:
0,180,180,0)
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Four-stroke inline four-cylinder engine (φj:
0,180,180,0)
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Vee engine
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Design considerations
• Similar to inline engine
• Even firing takes precedence over inertia
balancing
• Mirror symmetry of the crank shaft balances
primary moments
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Vee engine
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Shaking Force
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Shaking Force
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Shaking
Moment
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Inertia Torque
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Gas Torque
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Crank throw design for 90° V-8 engine
• Shall we use two φ = 0,180,180,0° four-cylinder engines together on one such Crankshaft?
• Gives balance conditions as four-stroke, four-cylinder engine.
• We have eight cylinders hence a delta phase angle of 90° for optimum power pulse
• We could use the φ = 0, 90, 180, 270° crankshaft designed
• Give advantage of its better inertia balance condition as well as achieve even firing
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Bending and
Torsional mode
of Vibration
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90° V-8 engine :
Phase Diagram (0,90,270,180°)
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90° V-8 engine : Total torque
(0,90,270,180°)
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90° V-8 engine :Shaking Forces and
Moments (0,90,270,180°)
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90° V-8 engine :
Primary moment(0,90,270,180°)
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Opposed Engine
Configurations
• A vee engine with a 180° vee angle.
• Good balance condition possible with a small number of cylinders such as two or four
• A four-stroke opposed twin with 0, 180° crank has even firing plus primary force balance.
• A four-stroke, opposed four-cylinder engine (flat four) with a 0, 180, 180,0°, four-throw crank has primary force balance but must fire its cylinders in pairs.
• A four-stroke flat four with a two-throw, 0, 180° crank will have even firing and the same balance condition as the inline four with a 0, 180,180,0°crank.
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THANK YOU
Next Class: Balancing Multicylinder Engines
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