Flywheel and Governors

Theory of Machines

1. * Function Of flywheel - A flywheel is an inertial energy-storage device. It absorbs mechanical energy and serves as a reservoir, storing energy during the period when the supply of energy is more than the requirement and releases it during the period when the requirement of energy is more than the supply. The main function of a fly wheel is to smoothen out variations in the speed of a shaft caused by torque fluctuations. If the source of the driving torque or load torque is fluctuating in nature, then a flywheel is usually called for. 5. Flywheel & Governors (8marks)

2. Turning moment diagram for 4-stroke internal combustion engine:-

3. * Coefficient of Fluctuation of Speed (C S ) - The difference between the maximum and minimum speeds during a cycle is called the maximum fluctuation of speed . The ratio of the maximum fluctuation of speed to the mean speed is called the coefficient of fluctuation of speed .

4. * Coefficient of Fluctuation of Energy (C E )- It may be defined as the ratio of the maximum fluctuation of energy to the work done per cycle. C E   W Where, P = Power N = Number of working strokes /min = N, for two stroke cycle = N/2, for four stroke cycle E = I * ω² I = Mass moment of Inertia ω= Angular speed  

5. GOVERNORS

6. INTRODUCTION Function of Governor - The function of a governor is to regulate the mean speed of an engine when there are variations in the load . The governor automatically controls the supply of working fluid to the engine with the varying load conditions and keeps the mean speed within certain limits .

7. Working principle When the load of an engine increases , its speed decreases , therefore it become necessary to increase the supply of working fluid . On the other hand when the load on the engine decreases, its speed increases and thus less working fluid is required.

8. Types of governor Watt governor : It is the simplest type of a centrifugal governor . If N is the speed of arm and ball about the spindle axis , then the height of the governor (h) is given by h=895/N^2 Porter governor : It is a modification of the watt governor , with a central load attached to the sleeve. The ratio of height of a porter governor to the height of a watt’s governor is = m+M /m Hartnell governor : It is a spring controlled governor.in a hartnell governor , the compression of the spring or lift of the sleeve (h) is given by h=(r2-r1) y/x Stiffness of the spring s=s2-s1/h Where, r1= minimum radius of rotation r2= maximum radius of rotation s1= spring force exerted at the minimum radius of rotation s2= spring force exerted at the maximum radius of rotation x = length of vertical or ball arm of the lever y = length of horizontal or sleeve arm of the lever

9. 1.Centrifugal Governor

10. It consists of two balls of equal masses attached to yhe two arms . the upper ends of the arm are pivoted to a spindle,which is driven by the engine through bevel gear. The lower arms connected to a sleeve which is connected to the spindle. The sleeve revolve with the spindle but can slide up and down . the two stops s1 and s2 on the spindle prevents the upwards and downward motion of sleeve . the sleeve is connected by a bell crank lever to a throtle valve,which controls the supply of the working fluid..

11. WATT GOVERNOR OPEN-ARM TYPE =In the first fig. the upper links are conncted by a horizontal link and the governor is known as open arm type watt governor . CROSSED –ARM TYPE =In the second fig the upper links cross the spindle and are connected by another link and the governor is known as crossed-arm governor.

12. 2.Porter Governor

13. 3.Proell Governor

14. 4.Hartnell Governor

15. 5 .Wilson-Hartnell Governor

16. 6.Hartung Governor

17. 7 .Pickering governor

18. POSITION AT DIFFERENT SPEED

19. PORTER GOVERNOR Porter governor : it is a modification of the watt governor , with a central load attached to the sleeve. The ratio of height of a porter governor to the height of a watt’s governor is = m+M /m

20. Hartnell Governor Hartnell governor : it is a spring controlled governor . In a hartnell governor , the compression of the spring or lift of the sleeve (h) is given by h=(r2-r1) b/a Stiffness of the spring s=s2-s1/h

21. Mechanical Governor Operation Mechanical Governor Operation at low engine speed

22. Mechanical Governor Operation at medium engine speed

23. Mechanical Governor Operation at high engine speed

24. FLYWHEEL GOVERNOR It controls speed variation caused by engine turning moment during cycle. It stores energy and gives up the energy whenever required. It regulates speed during one cycle only. It regulate the mean speed of engine when there is variation in load . It regulate the speed by regulating the quantity of charge. It regulates speed over period of time. FLYWHEEL Vs GOVERNOR

25. It has no control over quantity of charge. It is not essential if cycle fluctuation are not present as in multi cylinder engine. Governor takes care of quantity of charge . It is very essential element as it regulates the fuel supply as per demand FLYWHEEL GOVERNOR

26. IMPORTANT TERMS RELATED TO GOVERNOR Isochronous governors :A governor is said to be Isochronous when the equilibrium speed is constant for all radii of rotation of the balls . Hunting : A governor is said to be hunt if the speed of the engine fluctuates continuously above and below the mean speed. Stability of a governor :A governor is said to be stable when for very speed within the working range there is a definite configuration