In this article, we will learn the basics of governors in engine, definition, types like centrifugal, etc., working, etc., along with performance.
Let’s explore!
What are Governors in Engine? Definition
Governors Basics
Fluctuation in mean speed due to load variation can be minimized with the help of a governor. A governor depends upon the centrifugal force for their action.
- The flow of gasoline to the internal combustion engine is regulated by making use of a governor.
- Flywheel in comparison minimizes fluctuations of speed within the cycle.
- It doesn’t control fluctuations due to load variation.
Governor Definition
A device that regulates the mean speed of the engine, when there is variation in load is called a governor. A governor regulates the engine’s speed by varying the supply of fuel to the engine.
Terms Related to the Governors
To fully understand this topic, we need to understand some important terms.
Let’s explore them.
Governor Height
The vertical distance from the center of the governor balls to the point where the axis of the arm intersects on the spindle axis.
Governor height is denoted by ‘h’.
Equilibrium Speed
It is the speed at which the balls, arms of the governor are in complete equilibrium. At this speed, the sleeve doesn’t move upwards and downward.
Sleeve Lift
The vertical distance traveled by the sleeve from the mean position, due to a change in the equilibrium speed.
Mean Equilibrium Speed
Mean equilibrium speed is defined as the speed at the mean position of the sleeve or the balls.
Maximum and Minimum Equilibrium Speed
The speed at maximum and minimum radius of rotation of the balls, without tending to move either way is called Maximum and Minimum Equilibrium speeds respectively.
There can be many equilibrium speeds between the mean and the maximum, similarly, between the mean and the minimum equilibrium speed.
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How Does a Governor Work?
The working procedure of a governor shall be as follows,
- Governor mechanism is used to control the main speed of the engine.
- If the load on the shaft increases, engine speed decreases.
- The throttle is opened and fuel is drained into the engine.
- On the other hand, if the load on the shaft decreases, engine speed increases.
- The throttle valve will close and the supply of fuel to the engine decreases.
- The throttle valve is controlled by the governor through a mechanism.
- In this way, the mean speed of the engine is kept within certain limits.
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What are the Types of Governor in Engine?
Now is the time to discuss various types of governors based on their work. Mainly there are two types of governors.
- Centrifugal governor
- Inertia governor
Centrifugal governors are classified into the following types,
- Pendulum type
- Loaded type
Loaded Type governer are further classified as
- Deadweight governor
- Spring controlled governor
The deadweight governor has further two types:
- Porter governor
- Proell governor
Spring-controlled governors are classified as follows:
- Hartnell governor
- Pickering governor
- Hartung governor
- Wilson Hartnell governor
Now, we will learn all these types of governors in brief.
What are Centrifugal Governors? Definition, Working, Types
What is Centrifugal Governor?
It is a commonly used governor in which the centrifugal force is balanced by the controlling force. In this type of governor, centrifugal action and change in speed control its action.
Construction of Centrifugal Governor
It contains two balls that rotate along with the sleeve. The balls are attached to the arm and driven by gearing from the engine crankshaft. The spindle axis and sleeve are connected together and driven by the bevel gear mechanism.
- A throttle valve attached to the sleeve is responsible for changing the fuel supply.
- Bell crank
lever connects the sleeve and throttle valve.
How Does Centrifugal Governor Work?
Its working principle is the centrifugal action of governor balls. As we know the centrifugal force is directly proportional to the radius of rotation of the masses. Therefore, when the governor speeds up, the spin of the ball at a larger radius.
- The sleeve slides upwards on the spindle and the throttle is closed with the help of a bell crank lever.
- When governor speed decreases, consequently the balls rotate at a smaller radius.
- The sleeve moves downwards on the spindle and the throttle is opened to the required limit.
Types of Centrifugal Governor
Centrifugal governors are classified into the following types,
- Pendulum type
- Loaded type
Pendulum Type
This governor is regulated or actuated by means of a pendulum. Governor based on pendulum-type is watt governor.
What is Watt Governor?
This governor was first used by James watt in steam engines, therefore called watt governor. It is the simplest form of the centrifugal governor.
Construction of Watt Governor
It consists of two fly balls attached to the sleeve. Through the bevel gears, the engine drives the spindle. The upper arms are connected to the spindle and the lower arms are connected to the sleeve.
The sleeve is designed to revolve with the spindle and can slide up and down based on the spindle speed.
Working Principle of Watt Governor
As the engine load decreases, its speed increases, and the angular velocity of the governor spindle increases. When there is an increase in centrifugal force on the ball, sleeves move upward and balls move outward. This operates the throttle valve and the fluid supply to the engine decreases.
Conversely, as the engine load increases, its speed and the angular velocity of the governor spindle will decrease. As the centrifugal force on the ball decreases, balls move inward and sleeves move downward. This operates the throttle valve and the fluid supply to the engine increases. In this way, the mean speed of the engine is maintained within the limits.
Height of the Watt governor
The height of the Watt governor is inversely proportional to the square of speed. It is given by a formula.
H = 895/ N2 meters
Watt governor only works at low speed (60 to 80 rpm). We can overcome this drawback by loading the governor with dead weight or by means of a spring.
Loaded Type
In this type of centrifugal governor, the governor is loaded by a central load or spring. Loaded type governors are divided into categories such as:
- Deadweight governor
- Spring controlled governor
Deadweight Governor
Also called gravity-controlled centrifugal governor, here a central load is attached to the sleeve, which slides on the spindle.
A force of friction exists between the sleeve and the spindle, due to this force the sleeve moves upward and downward.
The deadweight governor has further two types:
- Porter governor
- Proell governor
Porter Governor
Porter Governor is the modified form of watt governor.
Construction
The deadweight is attached to the sleeves and the lower link to the central sleeve. Governor balls are balanced at the top. The stoppers will control the movement of the sleeve.
Working
Porter governor works on the action of gravity. The added downward force increases the RPM required to enable balls to rise. Fuel supply is altered by operating the throttle valve through the movement of sleeve mechanism and balls.
Proell Governor
Proell governor is another type of gravity control governor. It has nearly the same construction and working as porter governor.
Construction and working
The two balls are fixed on the upward extension of the lower links which are in the form of bent links. This reduces the change in speed required for sleeve movement. As the sleeve mechanism and balls actuate the throttle valve changes the fuel supply to the engine.
Spring Controlled Governor
In this type of governor, the movement of sleeves or balls are controlled by making use of a helical spring. The springs resists the centrifugal force. Being suitable for IC engines, these governors can be designed for high speed.
There are four types of spring-controlled governors. They are the following:
- Hartnell governor
- Pickering governor
- Hartung governor
- Wilson Hartnell governor
Hartnell Governor
Construction
It consists of two bell crank levers connected to the frame. The levers contain two balls. As the frame is connected to the governor shaft, therefore the frame rotates with the shaft. There are two rollers between the levers and spindle.
Working
Its working is based on the spring force. The spring rotates with the spindle and controls the motion of the sleeve and balls. When engine speed increases, the ball moves outward. With the motion of the bell crank lever, the sleeve moves up. As a result, the throttle valve moves with the help of a mechanism, therefore, the fuel supply is lowered.
Pickering Governor
This governor is used in gramophones to adjust the speed of the turntable. It has a quick response to change in load.
Construction and working
It is simple in construction and has small sleeve movement. Three springs are arranged along the spindle. When the balls revolve, they move outward. This leads to the bending of spring.
Hartung Governor
In this type of spring-controlled governor, the bell crank levers are connected to rotating spring balls.
Wilson Hartnell Governor
In this governor, on either of the sleeves, the balls are attached to the spring. The bell crank rotates along the spindle when it is pressed down.
What is Inertia Governor? Definition, Working, Types
What is Inertia Governor?
In this type of governor, the centrifugal force is balanced by inertia. It is not widely used. The combination of centrifugal and angular force controls the position of rotating balls. Being more sensitive, the inertia governor has a faster response than the centrifugal governor.
Construction of Inertia Governor
The whole setup of this governor is arranged in a circle form. It is connected to the crankshaft and flywheel of the engine. Utilizing spring and linkages, the position of balls is changed in order to open and close the throttle valve.
Working Principle of Inertia Governor
The inertia forces are developed by the angular acceleration of the engine shaft, due to a change in speed. These forces are utilized for ball movement.
As the balls move, the throttle valve gets actuated and the fuel supply to the engine gets changed.
What are the Characteristics of Governor?
The performance of a governor can be measured by checking the following parameters.
Sensitiveness
It is the phenomenon in which a governor responds to small changes in speed.
It is defined as the ratio of the difference between the maximum & minimum equilibrium speed to the mean equilibrium speed.
- Sensitivity = Range of Speed/ Mean Speed
If a governor readily responds to a small change of speed, then it’s a sensitive governor. We can measure sensitivity by the movement of the sleeve for a small change of speed.
Consider two governors ‘A’ and ‘B’ both having the same rotational speed. With fluctuation, their speeds increase or decrease. The governor ‘A’ has a larger lift (or fall) of the sleeve than the lift (or fall) of the sleeve of governor ‘B’. Consequently, we can say that governor ‘A’ is more sensitive than governor ‘B’.
Stability
For each speed, if the radius of rotation of the ball is within the speed range of the controller, the controller will be stable.
If the equilibrium speed increases with the increase of radius of governor balls, then the governor is said to be stable otherwise unstable. Stability and sensitivity are two opposing characteristics.
Isochronism
For an isochronous controller, in the working range, the equilibrium speed is constant for all the radius of rotation. For an isochronous governor, the speed range is zero and the governor maintains a constant speed. Porter governor is a type of governor that cannot be isochronous.
Hunting
When a governor is too sensitive, the engine speed sometimes fluctuates continuously above and below the average speed. It also occurs in isochronous governors. Due to the high sensitivity, small changes in engine speed can cause significant changes in fuel delivery.
Due to inertia the engine overshoots the desired mean position. The sleeve of the governor moves to the top position; the fuel supply gets cut off and the engine speed decreases drastically below the equilibrium position. With a high fuel supply, the speed increases above equilibrium or mean position.
Governor Effort and Power
Governor Effort
The mean force acting on the sleeve to lower or raise it for a given change of speed is called the effort of the governor.
Power of Governor
For the given percentage change the work done at the sleeve is called Power of the governor. It is the product of effort and displacement of the sleeve.
Controlling Force
It is the resultant external force that controls the movement of the ball. The controlling force acts on the axis along the radial line.
Insensitiveness of Governor
Due to the friction force at the sleeve, there is a rise in the insensitiveness of the governor. For a given radius, we have two different speeds.
At one speed the sleeve moves up and on the other, the sleeve moves down.
Total we have three-speed given as;
- Speed N at which there is no friction
- Speed N’ at which sleeve moves up as speed is increasing
- Speed N’’ at which sleeve moves down as speed is decreasing.
The insensitiveness of the governor is calculated with a coefficient.
Coefficient of insensitiveness = (N’ – N’’)/ N
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Conclusion
This is the complete discussion about the governors. If you have any queries regarding any part of this topic, put your questions in the comments section.
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