What is Governor? What are main Types of Governor?

Governor is a type of mechanical device which is generally used to determine and regulate the speed of the engine to the desired level. It is a particular feedback system used where is a need to control the variation of load present in the system. The main purpose of the governor is to control the flow of fuel into the engine to maintain a constant speed hence sometimes it is known as a speed limiter. When a load of an engine increases the speed of engine decreases and vice versa when the load on engine decreases the speed of engine increases. This is where governors play an important role to increase or reduce the fuel flow to the engine according to the requirements.

governors

Types of Governor:

The Governors are mainly divided into two types i.e Centrifugal Governor and Inertia Governor. These are further divided into the following types according to their design.

1. Centrifugal Governor

In Centrifugal Governor only centrifugal force and change in speed are responsible for controlling the actions. It widely used due to the variety of applications and mostly preferred when the balance on the masses is needed in the operation.

Principle

It works on the principle of balancing the centrifugal force of the rotating balls.

Construction

A Centrifugal Governor has a simple design. This type of governor has multiple masses known as governor balls which rotate at the distance from the axis of a shaft and driven through suitable gearing from the engine crankshaft. It has two balls of equal masses attached to the arm. These balls are provided by the combination of dead weight or spring. The spindle axis is connected to the sleeve and driven by a bevel gear mechanism connected with the crankshaft. The throttle valve is connected to the sleeves and operates by the actual change of speed of the engine. As load increases speed got decreases and the speed of governor ball as well as governor also decreases which is geared with the crankshaft.

Working

It works as the mechanical link between the throttle which is responsible for fuel supply and the speed. The governor balls revolve with spindles and create a centrifugal force in the inward direction which is generally known as the controlling force. A governing action depends upon the change of speed and centrifugal force provided by the balls. As soon as the throttle valve opens it increases the supply of fluid increasing speed of the engine. The inward and upward movement of the ball is transmitted by the governor sleeve to the throttle valve which controls the amount of fuel supplied to the engine. As soon as the shaft rotates, the object starts rotating around the shaft and goes away from it due to the action of the centrifugal force which operates the throttle valve.

Advantages

1. Easy to balance revolving parts.

Limitations

1. Slow response and less sensitive.

Applications

1. It limits the rotation speed in the internal combustion engine of an automobile and keeps it controlled according to the desired speed.

2. It is used to control the speed of the turbine shaft in the Hydro-electric power plant.

3. Centrifugal governors are also used to control the speed of the mechanical music box.

The Centrifugal Governors are further classified into two types. Pendulum and spring control governor.

A.) Pendulum type Governor:

Watt Governor is a pendulum governor according to their design.

a.) Watt Governor:

It is the oldest and simplest type of Centrifugal governor. Previously it was used by James watt in his steam engine.

watt governor

Construction

In the Watt governor, two balls are arranged on the sleeves consisting of arms. Upperside of the arm is connected to the spindle to move the ball in the upward and downward direction when they revolve with Spindle. The lower arm is connected to the sleeve which is joined to the spindle to operate the throttle valve. The spindle gets drives through a bevel gear and two stoppers are provided to the bottom and top of the spindle to restrict the movements of the sleeves.

Working

When the load at the engine increases the angular velocity as well as the speed of the engine automatically decreases. At the uniform speed controlling force is equal to the centrifugal force which balances each other but when the centrifugal force on balls decreases, the balls and spindle start to move inward and downward direction, respectively. These movements are responsible for the mechanism of the throttle valve and cause it to open widely which increases the fuel supply to maintain the speed.

Limitations

1. suitable for only vertical position application.

Applications

1. It is used in ships and trains to maintain the speed of the engine.

2. It can be used in AC generators to maintain electric supply.

B.) Gravity Loaded Governor:

There are two different designs of a gravity controlled centrifugal governor.

1. Porter Governor

2. Proell Governor

a.) Porter Governor

It is a dead weight loaded type governor who works on the action of gravity. Porter Governor is a modification of the Watt governor.

porter governor

Construction

In Porter Governor two balls are located at the top and load is attached to the sleeves.  The lower link is connected to the central sleeve and two stoppers are provided to control the movements of sleeves.  A mechanism is attached to the sleeves to operate the throttle valve.

Working

The balls tend to move up and down on the spindle due to the speed of revolution of the spindle. As load at the engine decreases the speed of the engine as well as spindle also tends to increases. Centrifugal force is responsible for the movement of balls in the upward direction while the lower arm pushes the sleeves upward to move the ball outward. These movements actuate the throttle valve and fuel supply gets decreases through the mechanism connected to the sleeves.

b.) Proell Governor

It is another type of governor who works on gravity control. The function of porter and proell governor are the same with little difference in working.

proell governor

Construction and working

The construction and working of the Proell Governor are nearly similar to the porter governor. Here revolving balls are attached to the extension link situated at the lower part and it reduces the change in the speed responsible for the movement of the sleeves. The movements of the sleeve and balls operate the throttle valve and decrease fuel supply to the engine.

C.) Spring Controlled Governor”

There are four different designs of the spring control governor.

1. Hartnell Governor

2. Wilson Hartnell Governor

3. Hartung Governor

4. Pickering Governor

a.) Hartnell Governor

Construction

Hartnell Governors consists of two bell cranks situated the different points of the frame. A frame is attached to the spindle, each lever carries a ball to the horizontal roller at the end of the vertical arm. The helical ring is provided to maintain the equal level force on the rollers and the arrangement of the screw is there to adjust a force of the spring.

Working

The working of the Hartnell governor depends on the control of the spring force. Here spring rotates around the spindle axis and controls the movement of the ball and sleeves.  The spring applies the downward force while sleeves move upward and downward depending on the speed. Two bell cranks situated at the frames carries a ball at one end and roller carries it at the other end. As the speed of the engine increases ball moves outward and the bell crank lever moves at the pivot lifting sleeves upward against the spring force. These movements then passed to the throttle valve with the help of machines and it results in lowering fuel supply as well as speed.

Advantages

1.  Suitable for very high speed

2. Pre-compression can be adjusted to achieve the desired equilibrium speed.

b.) Wilson- Hartnell

Construction and working

The balls are associated with the vertical arm and attached to the spring arranged on either side of the sleeves. The spring consists of two parts which belong to each ball. At the horizontal arm, roller comes into contact with sleeves and press it and make the bell-cranks to rotate along the spindle. Speed tends to improve the ball movement and spring gets exerted at the inward pressing roller against the sleeves due to centrifugal force. One end of the spring is attached to the spring and the other is connected to the lever and it tends to remain the sleeves down.

c.) Hartung Governor:

Construction and working

This is another type of governor work on the principle of controlled by the movement of spring. In Hartung type governor bell crank levers are connected with the rotating spring balls. These balls are compressed against the frame of the governor while rollers are pressed against the sleeves at the horizontal arms.

d.) Pickering Governors

Construction and working

In Pickering Governor there are three springs arranged around the spindle. The arrangement ids angular and each spring holds similar weight at the centers. The revolving balls act against these flat spring and weights move outwards. Spring tends to bend as the ball rotates about the axis of the spindle with greater speed.

Advantages

1. Quick response to the change in load

2. Great durability and reliability

2. Inertia Governor

Inertia governor is completely different from the centrifugal governor. The combination of angular and centrifugal force is used to control the position of the balls as well as the operation of the Governor. Since it is not very popular, it is preferred when a rapid response is the main concern.

Principle

It works on the principle of movement of inertia due to both centrifugal and inertia force.

Construction

This type of governor is connected to the crankshaft and flywheels of an engine. The governor balls are arranged in such a way that the position of it is affected by the force due to the angular acceleration of the shaft.  A suitable spring is loaded inside the governor to control the amount of displacement of governor balls and the mechanism of governor alters the supply of energy to the engine.

Working

In the inertia governor, more rapid response is obtained to the change of load as the position of the balls is affected by the rate of change of speed of the governor shaft. This type of governors' action depends upon acceleration and not due to the finite change in speed. A movement of the ball is controlled by spring and mechanism of the governor and through this, the supply of air-fuel mixture can be controlled.

Advantages

1. Highly sensitive to varying load

2. Quick response due to fast reaction

Limitations

1. Hard to balance revolving parts

Applications

1. It is used in the steam turbine to control and maintain the desired speed of the turbine when load increase or decrease during working

2. It is used in a diesel engine to control the speed of the engine at a  particular set point.