Mechanical Governor

A mechanical governor is a device used in various machines and engines to regulate and control the speed or rotational output. It operates based on the principle of centrifugal force and mechanical linkages. The main purpose of a mechanical governor is to maintain a stable speed or output, even under varying load conditions. It achieves this by automatically adjusting the fuel or energy input to the machine, ensuring that the desired speed is maintained within a predetermined range.

This blog shall delve into Mechanical Governor, Working Principle, Types, and Advantages. This article will help you prepare for exams like SSC JE ME and RRB JE Mechanical Engineering.

What is a Mechanical Governor?

A governor in mechanical engineering terms is a mechanical device utilised to automatically regulate and maintain the rotational motion of an engine or other prime mover within relatively close limits, irrespective of the load. Its primary function is to enable the engine to operate at a selected speed unaffected by variations in the load. By controlling the fuel flow into the engine, the governor ensures a consistent speed, which is why it is sometimes referred to as a speed limiter. As the load on the engine changes, causing the engine speed to decrease or increase, the governor plays a vital role in adjusting the fuel flow accordingly, ensuring optimal performance based on the requirements.

Working Principle of Mechanical Governor

The working principle of a governor is based on the equilibrium between the governor spring and flyweights. The selected spring and flyweight combination ensures that centrifugal force and spring force are balanced at the desired engine speed. When the speed increases, the centrifugal force of the flyweights increases as well, causing a reduction in fuel delivery through the system of levers. Conversely, when the speed decreases, the control rod adjusts to increase the fuel delivery rate and raise the speed to the desired level. 

Governors are designed to automatically maintain all speeds, including idling and minimum speed. They are commonly incorporated into fuel injection pump designs. Diesel engine governors should possess certain qualities or characteristics to ensure effective operation.

Types of Mechanical Governor

Governors can be broadly classified into two types:

Centrifugal Governors

These governors operate based on the principle of centrifugal force. They typically consist of rotating masses or flyweights that are driven by the engine's output shaft. As the engine speed changes, the centrifugal force on the flyweights varies, causing the governor to adjust the control mechanisms accordingly to regulate the speed.

The centrifugal governor operates by detecting changes in speed through gears and flyweights. It maintains a balance between the centrifugal force of the rotating balls and an equal and opposite radial controlling force. The flyweights play a crucial role in speed adjustment. These rotating balls are positioned opposite to each other and have the same weight.

When operating a small engine with a light load, the carburettor supplies an appropriate air-fuel mixture to the combustion chamber. As the crankshaft starts spinning, the centrifugal force causes the flyweights to open. Pressure is then applied to the governor and crank. The crank is connected to the throttle valve, resulting in the flyweights pulling the throttle valve towards the closed position.

If the load on the crankshaft increases, the flyweights spin at a slower speed, causing a decrease in centrifugal force. Consequently, the throttle valve is not fully pulled to the closed position, allowing an increased supply of air-fuel mixture.

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.

May not be suitable for complex control requirements or advanced applications.

Inertia Governors 

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 Inertial Governors

Provide precise and accurate speed control.

Quick response time to changes in load or speed variations.

Can handle sudden and transient loads effectively.

Offer stable and reliable speed regulation even in harsh operating conditions.

Do not require external power sources for operation.

Disadvantages of Inertial Governors

Complex design and construction, resulting in higher costs.

Require regular maintenance and adjustment for optimal performance.

May not be suitable for high-speed applications.

Can be sensitive to external factors such as vibration and shock.

Limited control range compared to electronic control systemsAdvantages of Mechanical Governor

The multiple advantages of Mechanical governors are:

Simplicity: Mechanical governors are relatively simple in design and construction, consisting of mechanical components and linkages.

Reliability: They tend to be robust and reliable, with fewer electronic components that could be prone to failure.

Cost-effectiveness: Mechanical governors are generally less expensive compared to their electronic counterparts.

Easy maintenance: Maintenance and repairs of mechanical governors are often simpler and can be performed without specialised electronic expertise.

Well-established technology: Mechanical governors have been used for a long time, and their principles of operation are well-understood, making them familiar to many technicians and engineers.

Suitable for low-tech applications: They are commonly used in simpler applications where precise control and advanced features may not be necessary.

Disadvantages of Mechanical Governors

The advantages of Mechanical Governors include:

Limited speed control: Mechanical governors may have limited responsiveness in regulating engine speed, leading to difficulties in maintaining precise speed control, especially under varying loads and conditions.

Sluggish response: Mechanical governors often suffer from sluggish response times, causing delays in adjusting the engine speed when there are sudden changes in load or demand.

Wear and tear: The mechanical components of governors can experience wear and tear over time, leading to reduced efficiency and accuracy in speed control.

Maintenance requirements: Mechanical governors require regular maintenance and calibration to ensure they function correctly. Failure to maintain them properly can result in performance issues or even engine damage.

Sensitivity to environmental factors: Mechanical governors can be affected by external factors like temperature, humidity, and vibrations, which may affect their performance and accuracy.

Size and complexity: Mechanical governors can be relatively bulky and complex, taking up valuable space and adding weight to the engine.

Lack of versatility: Some mechanical governors are designed for specific engine models or applications, limiting their versatility for use in different settings.

Inefficient fuel consumption: Due to their limited responsiveness, mechanical governors may not optimise fuel consumption as effectively as more advanced electronic systems.