Dynamics of Machines Unit V-Governors-Short notes with MCQ

1. ME8594 - DYNAMICS OF MACHINES
UNIT-V-MECHANISM FOR CONTROL
(GOVERNORS)
By,
Dr.S.SURESH,
Assistant Professor,
Department of Mechanical Engineering
Jayalakshmi Institute of Technology.

2. The governor is a device used to regulate the mean
speed of an engine, when there are variations in the load
e.g. when the load on an engine increases, its speed decreases,
therefore it becomes necessary to increase the supply of working fluid.
On the other hand, when the load on the engine decreases, its speed
increases and thus less working fluid is required.
GOVERNERS
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3. TYPES OF GOVERNERS
1) Centrifugal Governor
It works on the principle of balancing centrifugal force of the rotating
balls.
Applications
•Internal combustion engine.
•Hydro-electric power plant.
2) Inertia Governor
It works on the principle of movement of inertia due to both centrifugal and
inertia force.
Applications
•Steam turbine to control
•Diesel engine 3

4. TYPES OF CENTRIFUGAL GOVERNERS
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5. CENTRIFUGAL GOVERNORS
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6. (a) Watt (b) Porter (c) Proell
Pickering
governor
Wilson-Hartnell governor
Hartung governor
Hartnell governor 6

7. TERMS USED IN GOVERNORS
Equilibrium speed of governor:
Speed at which the governor is in complete balance
Mean equilibrium of governor:
speed of governor when the ball or sleeve is in mean position.
Maximum and minimum equilibrium speed of governor:
speed at which the radius of rotation of the ball is at minimum or in maximum
Height of governor:
Distance between the center of balls and the point where the upper arms of ball
meet the spindle axis of the governor.
Radius of rotation:
Horizontal distance of center of the ball from the axis of governor.
Sleeve lift of Governor:
It is the vertical movement of sleeve due to increasing or decreasing of equilibrium
speed.
Centrifugal force:
Radially outward force on Governor ball due to the rotational speed.
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8. 1. Watt Governor
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Relation between
Height and Speed
of the governor

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11. 2. PORTER GOVERNOR
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12. The point ‘B’ in equilibrium under the following forces
Relation between height of the governor (h) and speed of the ball (N)
When the length of arms are equal to the length of links
When consider the frictional force 12

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18. 3. PROELL GOVERNOR
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Relation between
Height and speed
of the governor

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22. 4. HARTNELL GOVERNOR
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Sleeve Lift Stiffness of the spring

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25. CHARACTERISTICS OF GOVERNORS
 Sensitiveness
Sensitiveness is the ratio of the difference
between the maximum and minimum equilibrium
speeds to the mean equilibrium speed.
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26.  Stability
A governor is said to be stable when there is one radius of rotation of the
balls for each speed which is within the speed range of the governor.
For a stable governor, if the equilibrium speed increases, the radius of
rotation of governor must also increase.
Note: A governor is said to be unstable, if the radius of rotation decreases as the
speed increases.
 Iso chronism
A governor is said to be isochronous if equilibrium speed is constant for all the
radii of rotation in the working range.
 Hunting
A governor is said to be hunt if the speed of the engine fluctuates continuously
above and below the mean speed.
This supply by a large amount when a small change in the speed of rotation
takes place.
Infinite Sensitivity
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27.  Effort
The effort of a governor is the mean force exerted
at the sleeve for a given percentage change of speed. (or
lift of the sleeve).
 Power
The power of a governor is the work done at the
sleeve for a given percentage change of speed. It is the
product of the mean value of the effort and the distance
through which the sleeve moves.
Power = Mean effort × lift of sleeve
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28. CONTROLLING FORCE
 A governor running at a steady speed, the inward
force acting on the rotating balls is known as
controlling force.
 It is equal and opposite to the centrifugal reaction.
In porter governor controlling force is provided by the
weight of sleeve and balls.
In spring controlled governor (eg: Hartnell governor)
controlling force provided by spring and weights.
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29. CONTROLLING FORCE DIAGRAM
 The controlling force diagram shows how the inward force varies
with the radius of rotation and the effect of friction. Which also
enables the examination of stability and sensitiveness of
governor.
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30. Controlling force diagram for spring controlled governor-Different conditions
•For the isochronous governor, the curve will be a straight line passing
through the origin. Fc = mω2r or Fc = ar, here a is constant.
•For Stable governor, the equation of governor is Fc = ar-b, here a and b are
constants.
In spring controlled governor, stability can be maintained by increasing spring
stiffness.
•For unstable spring controlled governor the equation for controlling force
curve is Fc = ar+b (this type of governor is impracticable)
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