What Is Engine Governor?- Working, and Types

What is Engine Governor?

A governor, or speed limiter or controller, is a device used to measure and regulate the speed of a machine, such as an engine.

A classic example is a centrifugal governor, also known as the Watt or fly-ball governor on a reciprocating steam engine, which uses the effect of inertial force on rotating weights driven by the machine output shaft to regulate its speed by altering the input flow of steam.

An Engine governor is a device that automatically maintains the rotary speed of an engine or other prime mover within reasonably close limits regardless of the load. A typical governor regulates an engine’s speed by varying the rate at which fuel is furnished to it.

Nearly all governors depend for their action on centrifugal force and consist of a pair of masses rotating about a spindle driven by the prime mover and kept from flying outward by a controlling force, usually applied by springs.

With an increase in speed, the controlling force is overcome and the masses move outward; the movement of the masses is transmitted to valves supplying the prime mover with its working fluid or fuel. The revolving masses are balls attached to a vertical spindle by link arms, and the controlling force consists of the weight of the balls.

If the load on the engine decreases, the speed will increase, the ball M will move out, and member C will slide up the vertical spindle and reduce the steam admitted to the engine, thus reducing the speed. An increase in the load will have the opposite effect.

Modern governors are used to regulating the flow of gasoline to internal combustion engines and the flow of steam, water, or gas to various types of turbines.

Functions of Governor in IC engine

  • The function of a governor is to regulate the mean speed of an engine, when there are variations in the load.
  • 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.
  • The governor automatically controls the supply of working fluid to the engine with the varying load conditions and keeps the mean speed of the engine within certain limits.
  • A little consideration will show, that when the load increases, the configuration of the governor changes, and a valve is moved to increase the supply of the working fluid; conversely, when the load decreases, the engine speed increases and the governor decreases the supply of working fluid.

Types of Governors

Following are the three different types of governors used in automobile vehicles:

  • Centrifugal governor.
  • Inertia Governor

1. Centrifugal Governor

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.

Engine Governor

The arms are connected by the links to a sleeve, which is keyed to the spindle. This 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 S, S 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.

In this case, the extra power output is provided to balance the increased load. When the load on the engine decreases, the engine and the governor speed increase, 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. In this case, the power output is reduced.

Note: When the balls rotate at uniform speed, the controlling force is equal to the centrifugal force and they balance each other

Advantages of Centrifugal Governors

  • Simple and robust design, making them reliable in operation.
  • Cost-effective compared to electronic or hydraulic control systems.
  • Can handle high-speed applications efficiently.
  • Provide automatic speed regulation without the need for external power sources.

Disadvantages of Centrifugal Governors

  • Limited control precision compared to modern electronic control systems.
  • Response time may be slower compared to electronic or hydraulic systems.
  • Sensitive to external factors such as temperature and friction, which can affect their accuracy.
  • Require regular maintenance and adjustment to ensure proper functioning.
  • It may not be suitable for complex control requirements or advanced applications.

Applications of the Centrifugal Governors

The following are some critical considerations to consider while using a centrifugal governor.

  • It regulates the rotation speed of the automobile’s internal combustion engine and keeps it at the proper pace.
  • It is used in hydroelectric power plants to control the speed of the turbine shaft.
  • Mechanical music boxes employ centrifugal governors to adjust speed.

2. Inertia Governor

Inertia governors, also known as flywheel governors, function based on the principle of inertia. They utilise a weighted lever or pendulum mechanism that responds to changes in speed by exploiting the inertia of the rotating components. When the speed increases or decreases, the inertia governor adjusts the control mechanisms to maintain a consistent speed.

Inertia governors differ significantly from centrifugal governors as they operate on a different principle.

In an inertia governor, the arrangement of governor balls is such that the inertia force resulting from the angular acceleration of the governor shaft tends to alter their positions. The displacement of the balls is controlled by a spring and a mechanism within the governor, which, in turn, regulates the supply of the air-fuel mixture.

The positions of the balls in an inertia governor are dependent on the rate of change of speed of the governor shaft. Consequently, these governors exhibit quick responses when load changes occur. Unlike centrifugal governors that respond to finite changes in speed, inertia governors take action based on acceleration.

However, centrifugal governors are generally preferred over inertia governors due to practical difficulties in arranging and achieving the expected balance of the revolving parts in inertia governors. The design and implementation of inertia governors can be more challenging, making centrifugal governors a more common choice in various applications.

Advantages of the Inertia Governors

There are a few crucial aspects to consider when it comes to the benefits of an inertia governor.

  • Extremely sensitive to load variations.
  • Quick response as a result of immediate reaction.

Limitations of the Inertia Governors

The downside of the inertia type is the practical difficulty of achieving a complete balance of the governor’s revolving elements.

Applications of the Inertia Governors

When it comes to using an inertia governor, there are a few essential aspects to consider.

  • It is used in a steam turbine to adjust and maintain the turbine’s desired speed when the load increases or decreases during operation.
  • It is used in a diesel engine to keep the engine speed at a specific set point.

Difference Between Governor And Flywheel

The following table lists the difference between the governor and the flywheel.

FunctionSpeed RegulationEnergy Storage and Smoothing
PurposeControls engine speed under load changesStores kinetic energy
RoleMaintains constant mean speedReduces speed fluctuations
Energy ManagementDoes not store energyAbsorbs and releases energy
Load FluctuationsAdjusts working fluid supply to compensate for load changesMinimizes speed variations due to load changes
ApplicationCommonly used in internal combustion engines, turbines, etc.Found in many rotating machinery such as engines, machines, etc.
MechanismUtilises mechanical linkage and control systemsRotating mass with high inertia
Speed Control RangeActively adjusts and controls engine speedDoes not actively control speed
PerformanceEnsures stable operation under varying loadsHelps stabilise speed fluctuations
Storage CapacityDoes not store energyCan store limited energy
Efficiency ImpactIt can affect engine efficiency depending on design and operationNegligible impact on engine efficiency
Modern RelevanceModern engine control systems have reduced the reliance on governors.Still widely used in various machinery

Advantages and Disadvantages of Governor in IC Engine

Some important advantages and disadvantages of governors in IC engines are discussed below.

Advantages of a Governor in an IC Engine

The advantages of using a Governor in an IC Engine are:

  • Speed Regulation: The governor helps maintain a consistent mean speed of the engine by adjusting the supply of working fluid, ensuring stable operation under varying load conditions.
  • Improved Efficiency: By controlling the working fluid supply, the governor optimises the engine’s fuel consumption and efficiency, leading to better overall performance.
  • Prevents Overspeeding: It prevents the engine from running at dangerously high speeds by limiting the working fluid supply, thereby protecting the engine from potential damage.
  • Load Balancing: The governor helps balance the load on the engine, ensuring that it operates efficiently and avoids unnecessary strain.
  • Self-Regulation: The governor functions automatically without requiring constant manual adjustments, reducing the need for continuous monitoring.

Disadvantages of a Governor in an IC Engine

The various disadvantages of Governors are:

  • Limited Responsiveness: Some types of governors may have a slow response time to sudden load changes, causing momentary fluctuations in engine speed.
  • Mechanical Complexity: Governor systems can add complexity to the engine setup, potentially leading to increased maintenance and repair requirements.
  • Power Loss: The governor consumes a small amount of power to function, which leads to a minor reduction in overall engine output.
  • Sensitivity to Wear and Tear: The governor’s components may experience wear over time, affecting its accuracy and performance.
  • Incompatibility with Modern Controls: Some older governor designs may not integrate well with modern engine control systems, limiting the use of advanced engine management technologies.