Dynamics of Machines - Unit V-Governors

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

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

2. Thegovernorisadeviceusedtoregulatethemean
speedofanengine,whentherearevariationsintheload
e.g.whentheloadonanengineincreases,itsspeeddecreases,
thereforeitbecomesnecessarytoincreasethesupplyofworkingfluid.
Ontheotherhand,whentheloadontheenginedecreases,itsspeed
increasesandthuslessworkingfluidisrequired.
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
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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-Hartnellgovernor
Hartunggovernor
Hartnellgovernor 6

7. TERMSUSEDINGOVERNORS
Equilibriumspeedofgovernor:
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:
Horizontaldistanceofcenteroftheballfromtheaxisofgovernor.
SleeveliftofGovernor:
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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9. 9
Relation between
Height and Speed
of the governor

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11. 2. PORTERGOVERNOR
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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
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15. 15

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18. 3. PROELLGOVERNOR
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Relation between
Height and speed
of the governor

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20. 20

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22. 4. HARTNELLGOVERNOR
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Sleeve Lift Stiffness of the spring

23. 23

24. 24

25. CHARACTERISTICS OFGOVERNORS
Sensitiveness
Sensitivenessistheratioofthedifference
betweenthemaximumandminimumequilibrium
speedstothemeanequilibriumspeed.
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26. Stability
Agovernorissaidtobestablewhenthereisoneradiusofrotationofthe
ballsforeachspeedwhichiswithinthespeedrangeofthegovernor.
Forastablegovernor,iftheequilibriumspeedincreases,theradiusof
rotationofgovernormustalsoincrease.
Note:Agovernorissaidtobeunstable,iftheradiusofrotationdecreasesasthe
speedincreases.
Isochronism
Agovernorissaidtobeisochronousifequilibriumspeedisconstantforallthe
radiiofrotationintheworkingrange.
Hunting
Agovernorissaidtobehuntifthespeedoftheenginefluctuatescontinuously
aboveandbelowthemeanspeed.
Thissupplybyalargeamountwhenasmallchangeinthespeedofrotation
takesplace.
Infinite Sensitivity
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27. Effort
Theeffortofagovernoristhemeanforceexerted
atthesleeveforagivenpercentagechangeofspeed.(or
liftofthesleeve).
Power
Thepowerofagovernoristheworkdoneatthe
sleeveforagivenpercentagechangeofspeed.Itisthe
productofthemeanvalueoftheeffortandthedistance
throughwhichthesleevemoves.
Power=Meaneffort×liftofsleeve
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28. CONTROLLING FORCE
Agovernorrunningatasteadyspeed,theinward
forceactingontherotatingballsisknownas
controllingforce.
It is equal and opposite to the centrifugal reaction.
Inportergovernorcontrollingforceisprovidedbythe
weightofsleeveandballs.
Inspringcontrolledgovernor(eg:Hartnellgovernor)
controllingforceprovidedbyspringandweights.
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29. CONTROLLING FORCEDIAGRAM
Thecontrollingforcediagramshowshowtheinwardforcevaries
withtheradiusofrotationandtheeffectoffriction.Whichalso
enablestheexaminationofstabilityandsensitivenessof
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. F
c= mω
2
r or F
c= ar, here a is constant.
•For Stable governor, the equation of governor is F
c= 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 F
c= ar+b(this type of governor is impracticable)
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