Size of Flywheel for Multi-Cylinder Engine vs Single-Cylinder Engine

Introduction:
The flywheel is an essential component of an engine that helps in maintaining a consistent speed and reducing speed fluctuations. It stores kinetic energy during the power stroke and releases it during the non-power strokes of the engine cycle. The size of the flywheel required for an engine depends on the indicated work per cycle, mean speed, and permissible fluctuation of speed.

Explanation:
To understand why the size of the flywheel required for a multi-cylinder engine is smaller than that of a single-cylinder engine, we need to consider the following factors:

1. Indicated Work per Cycle:
The indicated work per cycle is the work done by the engine on the piston during each cycle. In a multi-cylinder engine, the power strokes of different cylinders are overlapping, which results in a smoother power delivery compared to a single-cylinder engine. As a result, the indicated work per cycle in a multi-cylinder engine is distributed over multiple power strokes, reducing the overall fluctuations in torque. This reduces the requirement of a larger flywheel to smooth out speed fluctuations.

2. Mean Speed:
The mean speed of an engine is the average speed at which it operates. In a multi-cylinder engine, the power strokes of different cylinders are phased in a way that they overlap, resulting in a more uniform torque output. This allows the engine to operate at a higher mean speed compared to a single-cylinder engine. Higher mean speed leads to increased energy storage capacity in the flywheel, allowing for a smaller flywheel size.

3. Permissible Fluctuation of Speed:
The permissible fluctuation of speed is the maximum allowable speed variation during each cycle. In a multi-cylinder engine, the overlapping power strokes of different cylinders help in reducing the speed fluctuations. The smoother power delivery reduces the need for a larger flywheel to compensate for speed variations. On the other hand, a single-cylinder engine has a more pronounced speed fluctuation, requiring a larger flywheel to maintain a consistent speed.

Conclusion:
In conclusion, the size of the flywheel required for a multi-cylinder engine is smaller compared to a single-cylinder engine. This is due to the smoother power delivery, higher mean speed, and reduced speed fluctuations in a multi-cylinder engine. The overlapping power strokes of different cylinders help in distributing the indicated work per cycle, resulting in a more uniform torque output. This allows for a smaller flywheel size to maintain a consistent speed and reduce speed fluctuations.