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ME 362DYNAMICS OF MACHINERY

(2,0,2)

Denis Edem DzebreDepartment of Mechanical Engineering, KNUST.

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INTRODUCTION

Theory of Machines studies relative motion between the varioumachine, under the influence of forces.

Dynamics of Machinery is a branch of theory of machines andeffects of forces on machines or their components while they are i

Tries to define the laws of motion of components of mechanismsthe motion of the components, balance machines and mechanis

other things.

DDEK / 2014 / ME 362 DYNAMICS OF MACHINERY

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OUTLINE

Governors

Balancing

Gyroscopes


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READING MATERIALS

Mechanics of Machines, Hannah and Stephens

Theory of Machines, Kurmi and Gupta

Lecture Notes, ME 361 - Dynamics of Machinery, IDL KNUST


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ASSESSMENT


Class Attendance 5%

Assignments 10%

Mid-Semester Exam 15%

End of Semester Exam 70%

TOTAL 100%

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GOVERNORS

Governors together with flywheels control the speeds of engines.

Flywheels control fluctuation of engine speed (try to keep the spcertain range).

Governors control engine mean speed.

They try to maintain a mean engine speed by regulating the flow of fcombustion process in response to the load on the engine.

Load increase on the engine reduces engine (and governor) speed, oregulating valve and vice versa.

There are various types; Mechanical, Pneumatic, ElectromeElectronic governors, etc. etc. etc. (http://constructionmanuals.tpub.c

Focus is on Mechanical Governors.

http://constructionmanuals.tpub.com/http://constructionmanuals.tpub.com/http://constructionmanuals.tpub.com/

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MECHANICAL GOVERNORS

Are of two basic types; Inertia and Centrifugal.

Inertia/Shaft Governor

Relies on rate of change of speed to regulate fuel flow. Are reputsensitive


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Centrifugal Governor - Parts


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Centrifugal GovernorM/O


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CENTRIFUGAL GOVERNORS

Some Terminologies

Height of a governor

Refers to the vertical distance from the center of the ball to a point wthe arms (or arms produced) intersection the spindle axis, usually deno

Equilibrium speed.

the speed at which the governor balls, arms etc., are in complete eqsleeve does not tend to move upwards or downwards.

Mean equilibrium speed.

the speed at the mean position of the balls or the sleeve.

Maximum and minimum equilibrium speeds.

the speeds at the maximum and minimum radius of rotation of ttending to move either way.

Sleeve lift.

It is the vertical distance which the sleeve travels due to change in equ


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Types of Centrifugal Governors


Source:

Theory of Mach

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MECHANICAL GOVERNORS Types of Centrifugal Governors

Pendulum/Watt governor has low range of operating speed due small controlling force (from light weight of the sleeve).

Loaded governors provide a greater controlling force either

weighted mass or due to springs to oppose centrifugal mass


Key:

a. Watt/Pendulum

b. Porter

c. Proell

d. Hartnell

e. Wilson-Hartnell

f. A variation of the

(d) (e) (f)

Source:

Mechanics of Mac


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CENTRIFUGAL GOVERNORSSome Basic Concepts

Controlling Force

Resists the centrifugal force acting on the balls when the goveComprises the resultant effect of gravity on sleeve, weight at sleeve

Stability

A governor is said to be stable when there is only one radius ogovernor balls at which the governor is in equilibrium. The radiusstable governor increases with itsspeed of rotation. An unstable

move to one ofitsextreme positions, not settling at itsmean posit



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Some Basic Concepts

Sensitiveness

This depends on whether the governor is being treated as a single enta machine that it is connected to.

In the first instance,

The smaller the change in speed for a given sleeve movement, the the governor.

In the other instance, the speeds considered are the full load and nothe governor. So, the smaller the change in speed from no load to thmore sensitive the governor will be.



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Some Basic Concepts

Co-efficient of Insensitiveness

Co-efficient of insensitiveness is the change in speed required formake a correction to the fuel control system. It is calculated with tmaximum speeds before movement. It is due to friction which movement of the governor sleeve even when the speeds have chang



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CENTRIFUGAL GOVERNORSSome Basic Concepts

Hunting

This is the continuous fluctuation of the governor speed above andspeed. It occurs in a governor that is too sensitive, letting too much

into the engine.

Isochronous

A governor is said to be isochronous when the equilibrium sfor all radii of rotation of fly balls with the working range. This p

occurs in spring loaded governors.


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