Difference Between Flywheel and Governor

Both flywheel and governor are mechanical devices used mostly for the same purpose; that is to control or regulate the fluctuations in speed with the exception of the point of impact.

While a flywheel regulates the variation of speed at crankshaft, governor controls the variation of speed caused by load variation.

The main difference between the two is that the flywheel is always under operation when the engine is running and the operation is continuous from cycle to cycle, whereas the operation is intermittent in case of the governor, which means it only operates when the engine does not run at its mean speed.

Well, both tend to stabilize speed during fluctuations, so the difference seems to lie mainly in the working. Let’s take a good look at the two.

What is Flywheel?

A flywheel is a heavy rotating wheel attached to a revolving shaft that smooths out the delivery of power of a reciprocating engine due to the difference between the driving torque and the active torque over the cycle of operation.

Basically, it’s a mechanical device specifically designed to store rotational energy. It acts as a reservoir, meaning it stores energy when the supply of the energy is more than that is required for the operation and releases the same when the supply is less than the requirement.

In simple terms, a flywheel stores the excess of rotational energy for intermittent use. It provides continuous energy when the energy source is discontinuous. In automobile engines, it stores energy to help the engine over idle strokes of the piston. It’s often called as a flex plate when connected to automatic transmission.

What is Governor?

A governor is also a mechanical device that controls mean speed of the engine when there are variations in the load. It’s essentially a speed-controller device used to measure and regulate the speed of the machine irrespective of the load variations. It maintains the speed of the engine within specified limits regardless of load variations.

The governor changes the configuration when the load on the engine varies and controls the supply of the fuel accordingly. Unlike a flywheel, it can regulate speed but is unable to store and supply energy when required. It’s used in most engine-powered applications such as tractors, lawn mowers, automobiles, etc. It acts as a cruise control mechanism which keeps the engine running at a specified speed limit of your choosing, regardless of variations in the load. It detects changes in the load and adjusts the throttle accordingly.

Difference between Flywheel and Governor

1. Basics of Flywheel and Governor

Both are mechanical devices used for speed regulation/control to compensate for speed variations but with different point of impact. A flywheel maintains a constant speed under different load conditions for each thermodynamic cycle. A governor, on the other hand, also controls the engine operation and its main speed but the means is different from that of a flywheel.

2. Function of Flywheel and Governor

The flywheel stores excess of rotational energy for intermittent use. It stores energy when the supply is more than what’s required for the operation and releases the same when the supply is less than the requirement. The governor regulates the flow of fuel to maintain a constant mean speed throughout the cycle regardless of variations in load.

3. Operation of Flywheel and Governor

Flywheel is a heavy rotating metal wheel that resists changes in rotational speed providing energy when the energy source is discontinuous. The momentum of inertia is what drives the flywheel and it rotates at a varying angular speed. Despite energy variations, the crankshaft runs at constant speed in each stroke of the cycle. Governor, on the other hand, controls and maintains the speed of the engine by regulating the amount of fuel supply to the engine.

4. Speed of Flywheel and Governor

A flywheel rotates at a varying angular speed which increases when storing energy and decreases when releasing the same. It absorbs mechanical energy by increasing its angular velocity and releases the energy by decreasing the angular velocity. A governor, on the other hand, minimizes fluctuations within the mean speed which occurs due to load variation. It increases the fuel flow to keep the mean speed constant.

5. Application of Flywheel and Governor

A flywheel is more like an intra-cycle device that’s mainly used in reciprocating engines where the energy source is variable such as in automobile engines or fabricating machines like rolling mill, punching machines, etc. A governor, on the contrary, is like a speed-controller device used to regulate the speed of a machine and is mostly used in vehicles, turbine shafts, centrifugal governor, etc.

Flywheel vs. Governor: Comparison Chart

Summary of Flywheel vs. Governor

While the function of a flywheel is to regulate the fluctuations of speed during each cycle, the function of a governor is to keep the mean speed of the engine constant throughout the entire cycle. Flywheel stores rotational energy when the mechanical energy supplied is more than that’s required for operation, whereas a governor regulates the fuel supply according to the varying load conditions. While hypothetically both serve the same purpose, that is speed control, they do it very differently. The main difference in fact lies in the point of impact. This article compares the two on various aspects.

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