PRESENTATION REPORT ON

Governor

Submitted By:

Anand kumar (ME/13/710)

Department of Mechanical Engineering

SHRI BALWANT INSTITUTE OF TECHNOLOGYApproved by AICTE, Min of HRD, Govt of India & DTE, Govt of HaryanaAffiliated to DCR University of Science and Technology, Murthal, Sonepat

Meerut Road (Pallri), Near DPS, Sonepat-131001, Haryana

ABSTRACT

My report focuses on the topic GOVERNOR in the following report I have studied about the basics of Governor. As well as the report covers the inside view of the Governor. A governor, or speed limiter, is a device used to measure and regulate the speed of a machine, such as an engine. A classic example is the centrifugal governor, also known as the Watt or flyball governor, which uses weights mounted on spring-loaded arms to determine how fast a shaft is spinning, and then uses proportional control to regulate the shaft speed.

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CERTIFICATEThis is to certify that the Seminar Topic entitled as GOVERNOR and submitted by ANAND

KUMAR having Roll No ME/13/710, embodies the bonafide work done by him under my

supervision.

Signature of the Supervisor:

Place:

Date:

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Table of Contents

1 INTRODUCTION.......................................................................................................................................................5

2 DESCRIPTION...........................................................................................................................................................7

2.1 CENTRIFUGAL GOVERNORS...................................................................................................................................................7

2.1.1 Gravity Controlled Centrifugal Governors.............................................................................................................. 9

2.1.2 Spring Controlled Centrifugal Governors............................................................................................................. 12

2.2 CHARACTERISTICS OF GOVERNORS...................................................................................................................................14

2.2.1 Stability............................................................................................................................................................................... 14

2.2.2 Sensitiveness of Governors.......................................................................................................................................... 14

2.2.3 Isochronous Governors................................................................................................................................................. 14

2.2.4 Hunting............................................................................................................................................................................... 15

2.2.5 Effort and Power of a Governor............................................................................................................................... 16

3 HISTORY..................................................................................................................................................................17

4 CONCLUSION..........................................................................................................................................................18

5 REFRENCES.............................................................................................................................................................19

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1 INTRODUCTION

The function of a Governor is totally different to that of a Flywheel. The former is required to

control the mean speed of a engine over a period of time as opposed to a flywheel which is

used to limit the almost inevitable fluctuations in speed, which occur during one cycle.

A good example of this is the single cylinder four stroke engine. There is only one power

stroke to two revolutions of the crankshaft. Without a flywheel, the speed would either

fluctuate by an unacceptable amount within one cycle, or the engine would not work at all

since the energy stored in the flywheel is required to carry the engine through to the next

Power Stroke.

A change in load on a engine will almost certainly lead to a change in speed and the

Governor is required to alter the supply of energy to the engine to bring the speed back to its

original value. This is achieved by connecting the rotating parts of the governor, through

suitable levers, to a sleeve on its axis of rotation. Any change in the speed causes a change in

the position of the rotating parts and consequently to the sleeve and this movement actuates

the fuel supply valve (this includes compressed air, steam or water) of the particular engine or

turbine. This function is of particular importance in A.C. electric generators since it is

important to maintain the correct number of cycles per second from the generator who's load

may change rapidly and unpredictably.

Generally Governors can be classified as either Centrifugal or Inertia. Flywheel which

minimizes fluctuations of speed within the cycle but it cannot minimize fluctuations due to

load variation. This means flywheel does not exercise any control over mean speed of the

engine. To minimize fluctuations in the mean speed which may occur due to load variation,

governor is used. The governor has no influence over cyclic speed fluctuations but it controls

the mean speed over a long period during which load on the engine may vary.

The function of governor is to increase the supply of working fluid going to the prime mover

when the load on the prime-mover increases and to decrease the supply when the load

decreases so as to keep the speed of the prime-mover almost constant at different loads.

Example: 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 hence less working fluid is required.

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When there is change in load, variation in speed also takes place then governor operates a

regulatory control and adjusts the fuel supply to maintain the mean speed nearly constant.

Therefore, the governor automatically regulates through linkages, the energy supply to the

engine as demanded by variation of load so that the engine speed is maintained nearly

constant.

Types of Governors The governors may, broadly, be classified as

A. Centrifugal governors, and

B. Inertia governors.

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2 DESCRIPTION

Governor is a device used to maintain the speed of an engine within specified limits when the

engine works in varying of different loads. Based on the source of controlling force, the

governors can be classified into two types. Governor types are centrifugal governors and

inertia governors.

2.1 Centrifugal Governors

The centrifugal governors are based on the balancing of centrifugal force on the rotating balls

by an equal and opposite radial force, known as the controlling force. It consists of two balls

of equal mass, which are attached to the arms. These balls are known as governor balls or fly

balls. The balls revolve with a spindle, which is driven by the engine through bevel gears.

The upper ends of the arms are pivoted to the spindle, so that the balls may rise up or fall

down as they revolve about the vertical axis. The sleeve revolves with the spindle; but can

slide up and down. The balls and the sleeve rises when the spindle speed increases, and falls

when the speed decreases. In order to limit the travel of the sleeve in upward and downward

directions, two stops are provided on the spindle. The sleeve is connected by a bell crank

lever to a throttle valve. The supply of the working fluid decreases when the sleeve rises and

increases when it falls. When the load on the engine increases, the engine and the governor

speed decreases. This results in the decrease of centrifugal force on the balls. Hence the balls

move inwards and the sleeve moves downwards. The downward movement of the sleeve

operates a throttle valve at the other end of the bell crank lever to increase the supply of

working fluid and thus the engine speed is increased. Hence, the extra power output is

provided to balance the increased load.

Fig 1: Centrifugal Governor

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When the load on the engine decreases, the engine and the governor speed increases, which

results in the increase of centrifugal force on the balls. Thus the balls move outwards and the

sleeve rises upwards. This upward movement of the sleeve reduces the supply of the working

fluid and hence the speed is decreased. Hence, the power output is reduced.

In centrifugal governors, multiple masses know as governor balls, are responsible to revolve

about the axis of a shaft, which is driven through suitable gearing from the engine crankshaft.

Each ball is acted upon by a force which acts in the radially inward direction and is provided

by dead weight, a spring or a combination of two. This force is commonly called as the

controlling force and it will increase as the distance of the ball from the axis of rotation

increases. The inward or outward movement of the ball is transmitted by the governor

mechanism to the valve which controls the amount of energy supplied to the engine.

Fig 2: Types of Centrifugal Governor

Types of Centrifugal Governors Depending on the construction these governors are of two

types:

(a) Gravity controlled centrifugal governors, and

(b) Spring controlled centrifugal governors.

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2.1.1 Gravity Controlled Centrifugal Governors

In this type of governors there is gravity force due to weight on the sleeve or weight of sleeve

itself which controls movement of the sleeve. These governors are comparatively larger in

size.

There are three commonly used gravity controlled centrifugal governors:

(a) Watt governor

(b) Porter governor

(c) Proell governor

Watt governor does not carry dead weight at the sleeve. Porter governor and proell governor

have heavy dead weight at the sleeve. In porter governor balls are placed at the junction of

upper and lower arms. In case of proell governor the balls are placed at the extension of lower

arms. The sensitiveness of watt governor is poor at high speed and this limits its field of

application. Porter governor is more sensitive than watt governor. The proell governor is

most sensitive out of these three.

2.1.1.1 Watt Governor

This governor was used by James Watt in his steam engine. The spindle is driven by the

output shaft of the prime mover. The balls are mounted at the junction of the two arms. The

upper arms are connected to the spindle and lower arms are connected to the sleeve

Fig 3: Watt Governor

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We ignore mass of the sleeve, upper and lower arms for simplicity of analysis. We can ignore

the friction also. The ball is subjected to the three forces which are centrifugal force (Fc),

weight (mg) and tension by upper arm (T). Taking moment about point O (intersection of arm

and spindle axis), we get

Figure shows a graph between height ‘h’ and speed ‘N’ in rpm. At high speed the change in

height h is very small which indicates that the sensitiveness of the governor is very poor at

high speeds because of flatness of the curve at higher speeds.

Fig 4: Graph between height & Speed

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2.1.1.2 Porter Governor

There are two sets of arms. The top arms OA and OB connect balls to the hinge O. The hinge

may be on the spindle or slightly away. The lower arms support dead weight and connect

balls also. All of them rotate with the spindle. We can consider one-half of governors for

equilibrium.

Let,

w be the weight of the ball,

T1 and T2 be tension in upper and lower arms, respectively,

Fc be the centrifugal force,

r be the radius of rotation of the ball from axis, and

I is the instantaneous centre of the lower arm.

Taking moment of all forces acting on the ball about I and neglecting friction at the sleeve,

we get

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Fig 5: Porter Governor

2.1.2 Spring Controlled Centrifugal Governors

In these governors, a helical spring or several springs are utilized to control the movement of

sleeve or balls. These governors are comparatively smaller in size.

In these governors springs are used to counteract the centrifugal force. They can be designed

to operate at high speeds. They are comparatively smaller in size. Their speed range can be

changed by changing the initial setting of the spring. They can work with inclined axis of

rotation also. These governors may be very suitable for IC engines, etc.

The most commonly used spring controlled centrifugal governors are:

(a) Hartnell governor

(b) Wilson-Hartnell governor

(c) Hartung governor

2.1.2.1 Hartnell Governor

The Hartnell governor is shown in Figure 6. The two bell crank levers have been. One end of

each bellprovided which can have rotating motion about fulcrums O and O crank lever

carries a ball and a roller at the end of other arm. The rollers make contact with the sleeve.

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The frame is connected to the spindle. A helical spring is mounted around the spindle

between frame and sleeve. With the rotation of the spindle, all these parts rotate.

With the increase of speed, the radius of rotation of the balls increases and the rollers lift the

sleeve against the spring force. With the decrease in speed, the sleeve moves downwards. The

movement of the sleeve is transferred to the throttle of the engine through linkages.

Fig 6: Hartnell Governor

2.1.2.2 Inertia Governors

This works on a different principle. The governor balls are arranged so that the inertia forces

caused by angular acceleration or retardation of the governor shaft tend to alter their

positions. The amount of the displacement of the balls is controlled by springs and the

governor mechanism to alter the supply of energy to the engine. The advantage of this type of

governor is that the positions of the balls are affected by the rate of change of speed of the

governor shaft. Consequently, a more rapid response to a change of load is obtained, since the

action of the governor is due to acceleration and not to a finite change of speed. The

advantage is offset, however, by the practical difficulty of arranging for a complete balance

of the revolving parts of the governor. For this reason centrifugal governors are much more

frequently used.

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2.2 Characteristics of Governors

Different governors can be compared on the basis of following characteristics.

2.2.1 Stability

A governor is said to be stable when for every speed within the working range there is a

definite configuration i.e. there is only one radius of rotation of the governor balls at which

the governor is in equilibrium. For a stable governor, if the equilibrium speed increases, the

radius of governor balls must also increase.

2.2.2 Sensitiveness of Governors If a governor operates between the speed limits N1 and N2, then sensitiveness is defined as

the ratio of the mean speed to the difference between the maximum and minimum speeds.

Thus,

N1 = Minimum equilibrium speed,

N2 = Maximum equilibrium speed, and

2.2.3 Isochronous Governors

A governor is said to be isochronous when the equilibrium speed is constant (i.e. range of

speed is zero) for all radii of rotation of the balls within the working range, neglecting

friction. The isochronism is the stage of infinite sensitivity.

Let us consider the case of a Porter governor running at speeds N1 and N2 rpm.

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For Isochronism, range of speed should be zero i.e. N2 – N1 = 0 or N2 = N1. Therefore from

equations (1) and (2), h1 = h2, which is impossible in case of a Porter governor. Hence a

Porter governor cannot be isochronous. Now consider the case of a Hartnell governor running

at speeds N1 and N2 rpm.

Note: The isochronous governor is not of practical use because the sleeve will move to one of

its extreme positions immediately the speed deviates from the isochronous speed.

2.2.4 Hunting

Hunting is the name given to a condition in which the speed of the engine controlled by the

governor fluctuates continuously above and below the mean speed. It is caused by a governor

which is too sensitive and which, therefore, changes by large amount the supply of fuel to the

engine.

The following points, for the stability of spring-controlled governors, may be noted 1. For the

governor to be stable, the controlling force (FC) must increase as the radius of rotation (r)

increases, i.e. FC / r must increase as r increases. Hence the controlling force line AB when

produced must intersect the controlling force axis below the origin. The relation between the

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controlling force (FC) and the radius of rotation (r) for the stability of spring controlled

governors is given by the following equation

Where a and b are constants

The value of b in equation (i) may be made either zero or positive by increasing the initial

tension of the spring. If b is zero, the controlling force line CD passes through the origin and

the governor becomes isochronous because FC /r will remain constant for all radii of rotation.

The relation between the controlling force and the radius of rotation, for an isochronous

governor is, therefore,

If b is greater than zero or positive, then FC /r decreases as r increases, so that the equilibrium

speed of the governor decreases with an increase of the radius of rotation of balls, which is

impracticable Such a governor is said to be unstable and the relation between the controlling

force and the radius of rotation is, therefore

2.2.5 Effort and Power of a Governor

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). It may be noted that when the governor is running steadily,

there is no force at the sleeve. But, when the speed changes, there is a resistance at the sleeve

which opposes its motion. It is assumed that this resistance which is equal to the effort varies

uniformly from a maximum value to zero while the governor moves into its new position of

equilibrium. 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.

i.e., Power = Mean effort × lift of sleevePage 16 of 20

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3 History

Centrifugal governors were used to regulate the distance and pressure

between millstones in windmills since the 17th century. Early steam engines employed a

purely reciprocating motion, and were used for pumping water – an application that could

tolerate variations in the working speed.

It was not until the Scottish engineer James Watt introduced the rotative steam engine, for

driving factory machinery, that a constant operating speed became necessary. Between the

years 1775 and 1800, Watt, in partnership with industrialist Matthew Boulton, produced

some 500 rotative beam engines. At the heart of these engines was Watt’s self-designed

"conical pendulum" governor: a set of revolving steel balls attached to a vertical spindle by

link arms, where the controlling force consists of the weight of the balls.

The theoretical basis for the operation of governors was described by James Clerk

Maxwell in 1868 in his seminal paper' On Governors' Building on Watt’s design was

American engineer Willard Gibbs who in 1872 theoretically analyzed Watt’s conical

pendulum governor from a mathematical energy balance perspective. During his Graduate

school years at Yale University, Gibbs observed that the operation of the device in practice

was beset with the disadvantages of sluggishness and a tendency to overcorrect for the

changes in speed it was supposed to control.

Gibbs theorized that, analogous to the equilibrium of the simple Watt governor (which

depends on the balancing of two torques: one due to the weight of the "balls" and the other

due to their rotation), thermodynamic equilibrium for any work producing thermodynamic

system depends on the balance of two entities. The first is the heat energy supplied to the

intermediate substance, and the second is the work energy performed by the intermediate

substance. In this case, the intermediate substance is steam.

These sorts of theoretical investigations culminated in the 1876 publication of the Gibbs'

famous work On the Equilibrium of Heterogeneous Substances and in the construction of the

Gibbs’ governor, shown adjacent. These formulations are ubiquitous today in the natural

sciences in the form of the Gibbs' free energy equation, which is used to determine the

equilibrium of chemical reactions; also known as Gibbs equilibrium.

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4 CONCLUSIONThe governors are control mechanisms and they work on the principle of feedback control.

Their basic function is to control the speed within limits when the load on the prime mover

changes. They have no control over the change is speed within the cycle. The speed control

within the cycle is done by the flywheel.

The governors are classified in three main categories that are centrifugal governors, inertial

governor and pickering governor. The use of the two later governors is very limited and in

most of the cases centrifugal governors are used. The centrifugal governors are classified into

two main categories, gravity controlled type and spring loaded type.

The gravity controlled types of governors are larger in size and require more space as

compared to the spring controlled governors. These types of governors are two, i.e. Porter

governor and Proell governor. The spring controlled governors are: Hartnel governor, Wilson-

Hartnell governor and Hartung governor.

For comparing different type of governors, effort and power is used. They determine whether

a particular type of governor is suitable for a given situation or not. To categorise a governor

the characteristics can be used. It can be determined whether a governor is stable or

isochronous or it is prone to hunting. The friction at the sleeve gives rise to the insensitiveness

in the governor. At any particular radius, there shall be two speeds due to the friction.

Therefore, it is most desirable that the friction should be as low as possible.

The stability of a spring controlled governor can be determined by drawing controlling force

diagram which should have intercept on the negative side of Y-axis

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5 REFRENCES

http://www.infoplease.com/encyclopedia/science/mechanical governor.html

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