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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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