chapter 7 flywheel theory of machines and mechanisms.pptx

lecture notes

1. Theory of machines and mechanisms ( MEng3210 ) Chapter Seven (Flywheels) May, 2024 ADAMA SCIENCE AND TECHNOLOGY UNIVERSITY SCHOOL OF MECHANICAL, CHEMICAL AND MATERIALS ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING

2. 7.1 Introduction A flywheel is an inertial energy-storage device. It smoothens out variations in the speed of a shaft caused by torque fluctuations. It is commonly used in IC Engines Piston compressors Punch presses Rock crashers

3. Design Approach There are two major stages Determining amount of kinetic energy fluctuation in a cycle. 2. Calculating the required mass moment of inertia ( I ) of the flywheel. 7.2 Design of Flywheel

4. Speed fluctuation Average Speed Coefficient of speed fluctuation Design Parameters Range of q: 0.01-0.05 for Precision Machinery Up to 0.2 for Crashers

5. Design Equation The kinetic energy E k in a rotating system is The change in kinetic energy of a system can be given as , It can also be written as

6. Thus, the mass moment of inertia I needed in the entire rotating system in order to obtain selected coefficient of speed fluctuation q is determined using the relation Design Equation (contd.)

7. Geometry of Flywheel (a) Solid Flywheel (b) Spoked Flywheel

8. Stresses in Flywheel Radial and Tangential (Hoop) Stresses Equations same as those developed for thick-walled pressure vessels.

9. Example 1 1. The mass of flywheel of an engine is 6.5 tonnes and the radius of gyration is 1.8 metres. It is found from the turning moment diagram that the fluctuation of energy is 56 kN -m. If the mean speed of the engine is 120 r.p.m ., find the maximum and minimum speeds .

10. Solution

11. Example 2 The flywheel of a steam engine has a radius of gyration of 1 m and mass 2500 kg. The starting torque of the steam engine is 1500 N-m and may be assumed constant. Determine: 1. the angular acceleration of the flywheel, and 2. the kinetic energy of the flywheel after 10 seconds from the start. .

12. Solution

13. The end Thank you!