Flywheel free study notes for Diploma/BTech.

1. What is Flywheel ?

A flywheel is a heavy rotating mechanical device used to store energy and regulate speed fluctuations in machines.

Key Idea

• Stores energy when supply > demand
• Releases energy when demand > supply
• Maintains nearly uniform angular speed

2. Function of a Flywheel

• Reduces fluctuation of speed
• Stores rotational energy
• Supplies energy during low power strokes
• Improves machine efficiency and smoothness

Common Applications

• Internal combustion engines
• Reciprocating engines
• Punching and shearing machines
• Rolling mills

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3. Principle of Working

$E = \frac{1}{2} I \omega^2$E=21​Iω2

Where:

• $E$E = energy stored
• $I$I = mass moment of inertia
• $\omega$ω = angular velocity

Working Explanation

• During power stroke → energy stored
• During idle stroke → energy released
• Thus, speed remains nearly constant

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4. Construction of Flywheel

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Main Parts

1. Rim
   • Outer heavy ring
   • Stores most of the energy
2. Hub
   • Central portion
   • Mounted on shaft
3. Arms (Spokes)
   • Connect rim and hub
   • Provide structural support

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5. Types of Flywheels

(a) Solid Disc Flywheel

• Simple construction
• Used in small machines

(b) Rim Type Flywheel

• Heavy rim with spokes
• Stores more energy
• Widely used in engines

(c) High-Speed Flywheel

• Made of advanced materials
• Used in modern energy storage systems

6. Coefficient of Fluctuation

(a) Coefficient of Speed Fluctuation

$$C_s = \frac{N_{max} – N_{min}}{N_{mean}}$$

(b) Coefficient of Energy Fluctuation

$$C_e = \frac{E_{max} – E_{min}}{E_{mean}}$$

7. Energy Storage in Flywheel

$\Delta E = I \omega^2 C_s$

• $\Delta E$ΔE = maximum fluctuation of energy
• $C_s$Cs​ = coefficient of speed fluctuation

Important Insight

• Larger inertia → more energy storage
• Heavier rim → better performance

8. Turning Moment Diagram

• Shows variation of torque with crank angle
• Area above mean torque line → energy stored
• Area below → energy released

9. Flywheel vs Governor

Feature	Flywheel	Governor
Function	Controls speed fluctuation	Controls mean speed
Action	Stores/releases energy	Regulates fuel supply
Application	Cyclic machines	Engines

10. Advantages of Flywheel

• Smooth operation
• Reduces vibration
• Improves machine life
• Stores energy efficiently

11. Disadvantages of Flywheel

• Heavy and bulky
• Requires space
• Initial cost is high
• Risk at high speeds (bursting)

12. Applications of Flywheel

• IC engines (cars, bikes)
• Steam engines
• Punch presses
• Power plants
• Renewable energy storage systems

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