Short Notes: Flywheels and Governors | Short Notes for Mechanical Engineering PDF Download

 Page 1


                        
 
 
Unit 6. Flywheels, Governors and Balancing.    12 Marks   
5.1 Flywheel – introduction to flywheel - Need, function and application of flywheel with the 
help of turning moment diagram for single cylinder 4-Stroke I.C Engine  
6.2Coefficient of fluctuation of energy, coefficient of fluctuation of speed and its significance. 
6.3 Governors- Introduction, Types, function and application. Terminology of Governors. 
Comparison between flywheel and governor. 
6.4 Balancing – Need and types of balancing, Balancing of single rotating mass. Analytical and 
graphical method for balancing of several masses 
Cos – curse outcomes 
CO6 - Select suitable flywheel and governor for various applications. 
Necessity/ function of flywheel 
A flywheel used in machines serves as a reservoir. Flywheel stores 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. 
In case of steam engines, internal combustion engines, reciprocating compressors and pumps, 
the energy is developed during one stroke and the engine is to run for the whole cycle on the 
energy produced during this one stroke. For example, in internal combustion engines, the 
energy is developed only during expansion or power stroke which is much more than the 
engine load and no energy is being developed during suction, compression and exhaust strokes. 
The excess energy developed during power stroke is absorbed by the flywheel and releases it to 
the crankshaft during other strokes in which no energy is developed, thus rotating the 
crankshaft at a uniform speed. A little consideration will show that when the flywheel absorbs 
energy, its speed increases and when it releases energy, the speed decreases. Hence a flywheel 
does not maintain a constant speed; it simply reduces the fluctuation of speed.  
Application of flywheel – flywheel is used in I.C. engines, Steam engines, mechanical press, 
forging machines etc. 
 
Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine 
         
                           Figure - Turning Moment Diagram for  4 stroke I.C engines. 
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Unit 6. Flywheels, Governors and Balancing.    12 Marks   
5.1 Flywheel – introduction to flywheel - Need, function and application of flywheel with the 
help of turning moment diagram for single cylinder 4-Stroke I.C Engine  
6.2Coefficient of fluctuation of energy, coefficient of fluctuation of speed and its significance. 
6.3 Governors- Introduction, Types, function and application. Terminology of Governors. 
Comparison between flywheel and governor. 
6.4 Balancing – Need and types of balancing, Balancing of single rotating mass. Analytical and 
graphical method for balancing of several masses 
Cos – curse outcomes 
CO6 - Select suitable flywheel and governor for various applications. 
Necessity/ function of flywheel 
A flywheel used in machines serves as a reservoir. Flywheel stores 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. 
In case of steam engines, internal combustion engines, reciprocating compressors and pumps, 
the energy is developed during one stroke and the engine is to run for the whole cycle on the 
energy produced during this one stroke. For example, in internal combustion engines, the 
energy is developed only during expansion or power stroke which is much more than the 
engine load and no energy is being developed during suction, compression and exhaust strokes. 
The excess energy developed during power stroke is absorbed by the flywheel and releases it to 
the crankshaft during other strokes in which no energy is developed, thus rotating the 
crankshaft at a uniform speed. A little consideration will show that when the flywheel absorbs 
energy, its speed increases and when it releases energy, the speed decreases. Hence a flywheel 
does not maintain a constant speed; it simply reduces the fluctuation of speed.  
Application of flywheel – flywheel is used in I.C. engines, Steam engines, mechanical press, 
forging machines etc. 
 
Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine 
         
                           Figure - Turning Moment Diagram for  4 stroke I.C engines. 
lOMoARcPSD|34232105
                        
 
 
A turning moment diagram for a four stroke cycle internal combustion engine is shown in Fig. 
on the horizontal axis crank angles are shown and vertical axis turning moment(Torque or 
energy in Nm) is shown. In internal combustion engines, the energy is developed only during 
expansion or power stroke which is much more than the engine load and no energy is being 
developed during suction, compression and exhaust strokes. The excess energy developed 
during power stroke is shown by positive loop. During other strokes (suction, compression and 
exhaust) no energy is developed and they are shown by negative loops. The effect of the inertia 
forces on the piston is taken into account in above turning moment diagram. 
 
Maximum fluctuation of energy in flywheel 
The difference between the maximum and the minimum energies in flywheel is known as 
maximum fluctuation of energy. 
Maximum fluctuation of energy in flywheel = E
max 
- E
min
 
Where   E
max 
– maximum energy and  Emin
 
– minimum energy. 
 
Coefficient of Fluctuation of Energy  (C
E
) 
The ratio of the maximum fluctuation of energy to the work done per cycle is known as 
coefficient of fluctuation of energy. 
 
 
 
Fluctuation of Speed 
The difference between the maximum and minimum speeds during a cycle is called the 
maximum fluctuation of speed. 
Let N
max
 and N
min
 = Maximum and minimum speeds in r.p.m. during the cycle of flywheel. 
Maximum fluctuation of speed = N
max 
 -  N
min
 
 
Coefficient of Fluctuation of Speed (Cs) 
The ratio of the maximum fluctuation of speed to the mean speed is called the coefficient of 
fluctuation of speed. 
                                    Cs =  
       
 
 
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Unit 6. Flywheels, Governors and Balancing.    12 Marks   
5.1 Flywheel – introduction to flywheel - Need, function and application of flywheel with the 
help of turning moment diagram for single cylinder 4-Stroke I.C Engine  
6.2Coefficient of fluctuation of energy, coefficient of fluctuation of speed and its significance. 
6.3 Governors- Introduction, Types, function and application. Terminology of Governors. 
Comparison between flywheel and governor. 
6.4 Balancing – Need and types of balancing, Balancing of single rotating mass. Analytical and 
graphical method for balancing of several masses 
Cos – curse outcomes 
CO6 - Select suitable flywheel and governor for various applications. 
Necessity/ function of flywheel 
A flywheel used in machines serves as a reservoir. Flywheel stores 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. 
In case of steam engines, internal combustion engines, reciprocating compressors and pumps, 
the energy is developed during one stroke and the engine is to run for the whole cycle on the 
energy produced during this one stroke. For example, in internal combustion engines, the 
energy is developed only during expansion or power stroke which is much more than the 
engine load and no energy is being developed during suction, compression and exhaust strokes. 
The excess energy developed during power stroke is absorbed by the flywheel and releases it to 
the crankshaft during other strokes in which no energy is developed, thus rotating the 
crankshaft at a uniform speed. A little consideration will show that when the flywheel absorbs 
energy, its speed increases and when it releases energy, the speed decreases. Hence a flywheel 
does not maintain a constant speed; it simply reduces the fluctuation of speed.  
Application of flywheel – flywheel is used in I.C. engines, Steam engines, mechanical press, 
forging machines etc. 
 
Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine 
         
                           Figure - Turning Moment Diagram for  4 stroke I.C engines. 
lOMoARcPSD|34232105
                        
 
 
A turning moment diagram for a four stroke cycle internal combustion engine is shown in Fig. 
on the horizontal axis crank angles are shown and vertical axis turning moment(Torque or 
energy in Nm) is shown. In internal combustion engines, the energy is developed only during 
expansion or power stroke which is much more than the engine load and no energy is being 
developed during suction, compression and exhaust strokes. The excess energy developed 
during power stroke is shown by positive loop. During other strokes (suction, compression and 
exhaust) no energy is developed and they are shown by negative loops. The effect of the inertia 
forces on the piston is taken into account in above turning moment diagram. 
 
Maximum fluctuation of energy in flywheel 
The difference between the maximum and the minimum energies in flywheel is known as 
maximum fluctuation of energy. 
Maximum fluctuation of energy in flywheel = E
max 
- E
min
 
Where   E
max 
– maximum energy and  Emin
 
– minimum energy. 
 
Coefficient of Fluctuation of Energy  (C
E
) 
The ratio of the maximum fluctuation of energy to the work done per cycle is known as 
coefficient of fluctuation of energy. 
 
 
 
Fluctuation of Speed 
The difference between the maximum and minimum speeds during a cycle is called the 
maximum fluctuation of speed. 
Let N
max
 and N
min
 = Maximum and minimum speeds in r.p.m. during the cycle of flywheel. 
Maximum fluctuation of speed = N
max 
 -  N
min
 
 
Coefficient of Fluctuation of Speed (Cs) 
The ratio of the maximum fluctuation of speed to the mean speed is called the coefficient of 
fluctuation of speed. 
                                    Cs =  
       
 
 
lOMoARcPSD|34232105
                        
 
 
Function/ necessity of governor  
The function of a governor is to regulate the mean speed of an engine, when there are 
variations in the load. 
When the load on an engine increases, its speed decreases, therefore it becomes 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. 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.  
Application of governors – Steam engine, I.C engines, flow control mechanisms etc. 
 
Classification of governors 
The centrifugal governor classified below 
 
 
Centrifugal governor or Watt governor 
 
 
                                          Fig . centrifugal governor. 
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Page 4


                        
 
 
Unit 6. Flywheels, Governors and Balancing.    12 Marks   
5.1 Flywheel – introduction to flywheel - Need, function and application of flywheel with the 
help of turning moment diagram for single cylinder 4-Stroke I.C Engine  
6.2Coefficient of fluctuation of energy, coefficient of fluctuation of speed and its significance. 
6.3 Governors- Introduction, Types, function and application. Terminology of Governors. 
Comparison between flywheel and governor. 
6.4 Balancing – Need and types of balancing, Balancing of single rotating mass. Analytical and 
graphical method for balancing of several masses 
Cos – curse outcomes 
CO6 - Select suitable flywheel and governor for various applications. 
Necessity/ function of flywheel 
A flywheel used in machines serves as a reservoir. Flywheel stores 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. 
In case of steam engines, internal combustion engines, reciprocating compressors and pumps, 
the energy is developed during one stroke and the engine is to run for the whole cycle on the 
energy produced during this one stroke. For example, in internal combustion engines, the 
energy is developed only during expansion or power stroke which is much more than the 
engine load and no energy is being developed during suction, compression and exhaust strokes. 
The excess energy developed during power stroke is absorbed by the flywheel and releases it to 
the crankshaft during other strokes in which no energy is developed, thus rotating the 
crankshaft at a uniform speed. A little consideration will show that when the flywheel absorbs 
energy, its speed increases and when it releases energy, the speed decreases. Hence a flywheel 
does not maintain a constant speed; it simply reduces the fluctuation of speed.  
Application of flywheel – flywheel is used in I.C. engines, Steam engines, mechanical press, 
forging machines etc. 
 
Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine 
         
                           Figure - Turning Moment Diagram for  4 stroke I.C engines. 
lOMoARcPSD|34232105
                        
 
 
A turning moment diagram for a four stroke cycle internal combustion engine is shown in Fig. 
on the horizontal axis crank angles are shown and vertical axis turning moment(Torque or 
energy in Nm) is shown. In internal combustion engines, the energy is developed only during 
expansion or power stroke which is much more than the engine load and no energy is being 
developed during suction, compression and exhaust strokes. The excess energy developed 
during power stroke is shown by positive loop. During other strokes (suction, compression and 
exhaust) no energy is developed and they are shown by negative loops. The effect of the inertia 
forces on the piston is taken into account in above turning moment diagram. 
 
Maximum fluctuation of energy in flywheel 
The difference between the maximum and the minimum energies in flywheel is known as 
maximum fluctuation of energy. 
Maximum fluctuation of energy in flywheel = E
max 
- E
min
 
Where   E
max 
– maximum energy and  Emin
 
– minimum energy. 
 
Coefficient of Fluctuation of Energy  (C
E
) 
The ratio of the maximum fluctuation of energy to the work done per cycle is known as 
coefficient of fluctuation of energy. 
 
 
 
Fluctuation of Speed 
The difference between the maximum and minimum speeds during a cycle is called the 
maximum fluctuation of speed. 
Let N
max
 and N
min
 = Maximum and minimum speeds in r.p.m. during the cycle of flywheel. 
Maximum fluctuation of speed = N
max 
 -  N
min
 
 
Coefficient of Fluctuation of Speed (Cs) 
The ratio of the maximum fluctuation of speed to the mean speed is called the coefficient of 
fluctuation of speed. 
                                    Cs =  
       
 
 
lOMoARcPSD|34232105
                        
 
 
Function/ necessity of governor  
The function of a governor is to regulate the mean speed of an engine, when there are 
variations in the load. 
When the load on an engine increases, its speed decreases, therefore it becomes 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. 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.  
Application of governors – Steam engine, I.C engines, flow control mechanisms etc. 
 
Classification of governors 
The centrifugal governor classified below 
 
 
Centrifugal governor or Watt governor 
 
 
                                          Fig . centrifugal governor. 
lOMoARcPSD|34232105
                        
 
 
         The centrifugal governors consist of two balls of equal mass, which are attached to the 
arms as shown in Figure. These balls are known as governor balls or fly balls. The balls revolve 
with a spindle, which is driven by the engine through bevel gears. The upper ends of the arms 
are pivoted to the spindle, so that the balls may rise up or fall down as they revolve about the 
vertical axis. The arms are connected by the links to a sleeve, which is keyed to the spindle. This 
sleeve revolves with the spindle; but can slide up and down. The balls and the sleeve rise when 
the spindle speed increases, and falls when the speed decreases. In order to limit the travel of 
the sleeve in upward and downward directions, two stops S
1
, S
2
 are provided on the spindle. 
The sleeve is connected by a bell crank lever to a throttle valve. The supply of the working fluid 
decreases when the sleeve rises and increases when it falls.  
        When the load on the engine increases, the engine and the governor speed decreases. This 
results in the decrease of centrifugal force on the balls. Hence the balls move inwards and the 
sleeve moves downwards. The downward movement of the sleeve operates throttle valve at 
the other end of the bell crank lever to increase the supply of working fluid and thus the engine 
speed is increased.  
       When the load on the engine decreases, the engine and the governor speed increases, 
which results in the increase of centrifugal force on the balls. Thus the balls move outwards and 
the sleeve rises upwards. This upward movement of the sleeve reduces the supply of the 
working fluid and hence the speed is decreased. 
 
 
                        Figure – Connections of upper arm in centrifugal or Watt governor. 
The simplest form of a centrifugal governor is a Watt governor shown in Figure. It is basically a 
conical pendulum with links attached to a sleeve of negligible mass. The arms of the governor 
may be connected to the spindle in the following three ways: 
1. The pivot P is on the spindle axis as shown in Fig. (a). 
2. The pivot P is offset from the spindle as shown in Fig. (b). 
3. The pivot P is offset, but the arms cross the spindle axis as shown in Fig. (c). 
 
The working principal of all governors are same, only difference in constructions of the 
governors. The various governors are explained below. 
 
 
 
 
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Page 5


                        
 
 
Unit 6. Flywheels, Governors and Balancing.    12 Marks   
5.1 Flywheel – introduction to flywheel - Need, function and application of flywheel with the 
help of turning moment diagram for single cylinder 4-Stroke I.C Engine  
6.2Coefficient of fluctuation of energy, coefficient of fluctuation of speed and its significance. 
6.3 Governors- Introduction, Types, function and application. Terminology of Governors. 
Comparison between flywheel and governor. 
6.4 Balancing – Need and types of balancing, Balancing of single rotating mass. Analytical and 
graphical method for balancing of several masses 
Cos – curse outcomes 
CO6 - Select suitable flywheel and governor for various applications. 
Necessity/ function of flywheel 
A flywheel used in machines serves as a reservoir. Flywheel stores 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. 
In case of steam engines, internal combustion engines, reciprocating compressors and pumps, 
the energy is developed during one stroke and the engine is to run for the whole cycle on the 
energy produced during this one stroke. For example, in internal combustion engines, the 
energy is developed only during expansion or power stroke which is much more than the 
engine load and no energy is being developed during suction, compression and exhaust strokes. 
The excess energy developed during power stroke is absorbed by the flywheel and releases it to 
the crankshaft during other strokes in which no energy is developed, thus rotating the 
crankshaft at a uniform speed. A little consideration will show that when the flywheel absorbs 
energy, its speed increases and when it releases energy, the speed decreases. Hence a flywheel 
does not maintain a constant speed; it simply reduces the fluctuation of speed.  
Application of flywheel – flywheel is used in I.C. engines, Steam engines, mechanical press, 
forging machines etc. 
 
Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine 
         
                           Figure - Turning Moment Diagram for  4 stroke I.C engines. 
lOMoARcPSD|34232105
                        
 
 
A turning moment diagram for a four stroke cycle internal combustion engine is shown in Fig. 
on the horizontal axis crank angles are shown and vertical axis turning moment(Torque or 
energy in Nm) is shown. In internal combustion engines, the energy is developed only during 
expansion or power stroke which is much more than the engine load and no energy is being 
developed during suction, compression and exhaust strokes. The excess energy developed 
during power stroke is shown by positive loop. During other strokes (suction, compression and 
exhaust) no energy is developed and they are shown by negative loops. The effect of the inertia 
forces on the piston is taken into account in above turning moment diagram. 
 
Maximum fluctuation of energy in flywheel 
The difference between the maximum and the minimum energies in flywheel is known as 
maximum fluctuation of energy. 
Maximum fluctuation of energy in flywheel = E
max 
- E
min
 
Where   E
max 
– maximum energy and  Emin
 
– minimum energy. 
 
Coefficient of Fluctuation of Energy  (C
E
) 
The ratio of the maximum fluctuation of energy to the work done per cycle is known as 
coefficient of fluctuation of energy. 
 
 
 
Fluctuation of Speed 
The difference between the maximum and minimum speeds during a cycle is called the 
maximum fluctuation of speed. 
Let N
max
 and N
min
 = Maximum and minimum speeds in r.p.m. during the cycle of flywheel. 
Maximum fluctuation of speed = N
max 
 -  N
min
 
 
Coefficient of Fluctuation of Speed (Cs) 
The ratio of the maximum fluctuation of speed to the mean speed is called the coefficient of 
fluctuation of speed. 
                                    Cs =  
       
 
 
lOMoARcPSD|34232105
                        
 
 
Function/ necessity of governor  
The function of a governor is to regulate the mean speed of an engine, when there are 
variations in the load. 
When the load on an engine increases, its speed decreases, therefore it becomes 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. 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.  
Application of governors – Steam engine, I.C engines, flow control mechanisms etc. 
 
Classification of governors 
The centrifugal governor classified below 
 
 
Centrifugal governor or Watt governor 
 
 
                                          Fig . centrifugal governor. 
lOMoARcPSD|34232105
                        
 
 
         The centrifugal governors consist of two balls of equal mass, which are attached to the 
arms as shown in Figure. These balls are known as governor balls or fly balls. The balls revolve 
with a spindle, which is driven by the engine through bevel gears. The upper ends of the arms 
are pivoted to the spindle, so that the balls may rise up or fall down as they revolve about the 
vertical axis. The arms are connected by the links to a sleeve, which is keyed to the spindle. This 
sleeve revolves with the spindle; but can slide up and down. The balls and the sleeve rise when 
the spindle speed increases, and falls when the speed decreases. In order to limit the travel of 
the sleeve in upward and downward directions, two stops S
1
, S
2
 are provided on the spindle. 
The sleeve is connected by a bell crank lever to a throttle valve. The supply of the working fluid 
decreases when the sleeve rises and increases when it falls.  
        When the load on the engine increases, the engine and the governor speed decreases. This 
results in the decrease of centrifugal force on the balls. Hence the balls move inwards and the 
sleeve moves downwards. The downward movement of the sleeve operates throttle valve at 
the other end of the bell crank lever to increase the supply of working fluid and thus the engine 
speed is increased.  
       When the load on the engine decreases, the engine and the governor speed increases, 
which results in the increase of centrifugal force on the balls. Thus the balls move outwards and 
the sleeve rises upwards. This upward movement of the sleeve reduces the supply of the 
working fluid and hence the speed is decreased. 
 
 
                        Figure – Connections of upper arm in centrifugal or Watt governor. 
The simplest form of a centrifugal governor is a Watt governor shown in Figure. It is basically a 
conical pendulum with links attached to a sleeve of negligible mass. The arms of the governor 
may be connected to the spindle in the following three ways: 
1. The pivot P is on the spindle axis as shown in Fig. (a). 
2. The pivot P is offset from the spindle as shown in Fig. (b). 
3. The pivot P is offset, but the arms cross the spindle axis as shown in Fig. (c). 
 
The working principal of all governors are same, only difference in constructions of the 
governors. The various governors are explained below. 
 
 
 
 
lOMoARcPSD|34232105
                        
 
 
Porter Governor. 
                           
                                               Figure - Porter Governor. 
The Porter governor is a modification of a Watt’s/Centrifugal governor, with Dead weight 
attached to the sleeve as shown in Fig. The dead weight moves up and down with sleeve on the 
central spindle. This additional downward force gives control over sleeve movement. When the 
speed of spindle increases, the fly ball moves away from spindle due to centrifugal force and 
sleeve slides up on the spindle. When the speed of spindle decreases, the fly ball moves 
towards the spindle and sleeve slides down on the spindle. Up down movement of sleeve 
operates the throttle which governs the quantity of fuel. 
 
 
 Proell  Governor. 
                       
                                            Figure -  Proell Governor. 
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