INTERNAL

COMBUSTION

ENGINES

SECTION 2

CONSTRUCTION OF INTERNAL

COMBUSTION ENGINES

CONSTRUCTION OF INTERNAL

COMBUSTION ENGINES

The Camshaft:-

1. An IC Engine produces power by burning fuel. In a 4-cycle engine, the change is introduced into the cylinder through

the intake Valve

2. In order for the four combustion events to occur at exactly the same time, the valves must open and close in relation to the

position of the in the cylinder. Piston

3. In the (2-cycle / 4-cycle) engine, combustion events are timed by the piston instead of by the valves.

2-cycle

4. The intake and exhaust valves in a 4-cycle engine are operated by a

camshaft.

Cams are mounted on this

Camshaft

5. The cams are oval shaped metal pieces which are (centered / off-center) on the shaft.

Off-center

6. There are two cams for each cylinder: one cam for the intake valve and one for the exhaust valve.

An 8-cylinder engine has . cams on its camshaft. 16

7. The camshaft is rotated by the crankshaft through the set of gears at the shaft ends.

The gear on the camshaft is (twice / one-half) as large as the gear on the

crankshaft.

Twice

8. Thus the camshaft gear turns at one-half the speed of the crankshaft.

Each valve opens (once / twice) for each two turns of the crankshaft.

Once

9. As the camshaft rotates, a cam lifts and moves a push rod.

The push rod lifts and drops a

Rocker area

10. As the push rod lifts one end of the rocker arm, the other end forces the valve stem down.

The valve spring is compressed and the valve . Opens

11. In a 4-cycle engine, each valve must open once each time the crankshaft makes two revolutions.

Each valve opens once every the camshaft makes revolution. One

12. The camshaft makes (one-half as many / twice as many) revolutions as the crankshaft.

One-half as many

13. With the camshaft gear turning at one half the speed of the crankshaft gear, the camshaft rotates only once every time the

crankshaft rotates .. Twice

14. The which operates an intake valve opens the valve at the beginning of intake and . it at the end of intake.

Closes

15. The cam which operates an exhaust valve . the exhaust valve at the beginning of the exhaust stroke and closes at the end

of the exhaust.

Opens

16. Intake and exhaust valves remain closed during the . power events.

Compression

17. Look at the drawing.

During compression and power, the cam (lifts/ does not lift) the push rod.

Does not lift

18. This happens because of the (shape / size) of the cam. Shape

19. Lets review The camshaft is turned by the (crankshaft / connecting rod).

Crankshaft

There is one cam for each .. in the engine. Valve

If the valves do not open and close at right time, the cylinders (fire /

do not fire) properly.

Do not fire

Both the intake and exhaust valves are (open / closed) during the

compression and power strokes.

Closed

The Carburetor:-

20. For smooth and efficient burning, air and fuel must be mixed in

just the right amounts.

To get the proper air fuel ratio, it is necessary to .. the amount of fuel and air being combined.

Control/Regulate

21. In order to be mixed with air and burned, liquid fuel is broken up into a fine mist.

When liquid fuel is sprayed into a combustible mixture is produced.

Air

22. The carburetor makes liquid fuel . by breaking it into a fine mist and mixing it with air.

Combustible/Burnible

23 .The carburetor is positioned so that it can atomize fuel, mix it with

air, and feed the mixture to the .. Cylinders

24. The carburetor is normally (near the top / near the bottom) of the cylinder.

Near the top

25. The drawing shows a simplified model of a carburetion system.

The downward motion of the piston creates a . pressure area in the cylinder.

Low

26. This low pressure pulls into the carburetor from the atmosphere.

Air

27. The narrow air passage inside the carburetor is called the venturi. As air rushes past the venture, it picks up particles of .

Fuel

28. At this point the drops of fuel and the air Mix

29. The fine air-fuel mist is fed to the cylinders through the Manifold

30. The .. in the manifold is adjustable to control the amount of charge being distributed to the cylinders.

Throttle

31. When the throttle is turned wider, more charge is fed to the cylinders.

The engine turns faster and delivers more .

Power

Gas Admission System:- 32. Spark ignition engines using natural gas or any other gas as a fuel

do not need a carburetor to mix air with fuel.

Instead, gas is piped under pressure to a . line, or it may be run through a mixing valve.

Header

33. When the head line is used, gas pressure is maintained in this header line up to each individual .........head.

Cylinder

34. The header line distributes the gas evenly through inlet pipes to the cylinders.

To distribute the mixture evenly, the gas may be put into the air at the

entrance to the Cylinder

35. Using a mixing valve or putting exactly the same amount of gas into the air passage at each cylinder gives an .. distribution of the air-fuel mixture.

Even

36. The proportion of air to natural gas must be closely controlled. When the fuel air proportion is right, the mixture .. smoothly and evenly.

Burns

37. Too rich a mixture explodes (detonates / knocks),. Too lean a mixture

may not even.. Ignite/Burn

38. As the load on an engine increases, the speed of the engine (increases / decreases).

Decreases

39. To maintain speed, the fuel supply must be .. Increased

40. To take care of changes in load, a throttle in the intake air passage adjusts the amount of air entering the cylinder.

A throttle in the gas header line adjusts the supply to the cylinder to compensate changes in load.

Gas

41. As the load changes, combustion is maintained by adjusting the supply of . and the supply of . with throttles which are separate but linked together.

Gas, Air

Governors:-

Types:- Mechanical Governor Hydraulic Governor

42. When the charge is ignited, combustion occurs, heated gases

expand, and power is produced.

The amount of produced depends upon the . of fuel burnt. Amount

43. When the load on the engine is changed, the amount of power produced must be changed to maintain a . speed.

Constant/Steady

44. Most stationary internal combustion engines use a governor to make the changes necessary when the engine load is changed.

The governor maintains the desired speed by adjusting the amount of

. furnished to the engine. Fuel

45. When we change the proportions of fuel to air in a charge we change the amount of fuel in the charge.

When we change the amount of fuel in the charge, we the amount of power produced.

Change

46. Where the proportion of fuel to air is to be changed, the fuel intake system is metered by the .

Governor

47. If the proportion of fuel to air in the charge is kept constant, then the

power produced by the engine is changed by changing the . of the charge.

Amount/Charge

47. The amount of charge admitted to the cylinder is controlled by the throttle.

Where the amount of charge is to be changed, the governor adjusts the .to give enough fuel.

Throttle

48. Before the governor can maintain a constant speed, it must be set for that speed.

Otherwise the engine may slow down too much when the load increases

or over speed if the load . Decreases

49. Once the governor is set at the desired engine speed, it maintains that speed.

When the load on the engine is increased, the amount of fuel admitted to

the engine is .. When the load on the engine is decreased, the amount of fuel admitted to

the engine is Increased , Decreased

50. Each type of internal combustion engine has a governor specifically adapted to the capabilities of the engine.

Most governors are connected to the throttle to control the amount of the

to be admitted to the engine. Charge

51. Two basic types of governors are used to control the amount of charge admitted to the engine by opening and .the throttle.

Closing

52. The mechanical governor is connected to the engine crankshaft through gears.

It is connected directly to the throttle so that any movement in the control

elements of the governor causes a corresponding movement in the .. Throttle

53. The hydraulic governor is also connected to the engine crankshaft through gears.

But the control elements of the governor transmit their motion to a pilot

valve which controls a flow of oil in and out of a hydraulic power

cylinder. The power piston in this hydraulic cylinder is connected to the

. Throttle

54. In either type of governor the three elements which control movements of the throttle are the flyweights, the speeder spring

and the speeder rod.

The flyweights receive in direct relation to the engine crankshaft and

translate engine speed into (torque / centrifugal force).

Centrifugal force

55. The centrifugal force of the revolving flyweights is applied against the speeder spring to move the speeder rod.

An increase in engine ..causes an increase in forces to be applied against the speeder spring, compressing it.

Speed

56. The speeder rod is connected to the speeder spring in such a way that when the speeder spring is compressed it causes the to move in the direction of spring compression.

Speeder rod

57. When the engine speed decreases, the centrifugal force of the flyweights decreases and the speeder spring expands.

When the speeder spring expands it causes the speeder rod to move in the

direction. Opposite/ Other

58. The speeder rod is connected to the engine throttle so that when the flyweights compress the speeder spring, the speeder rod causes the

throttle to close.

Thus engine speed is increased, the ..of charge admitted to the engine is decreased.

Amount

59. When engine speed decreases, the governor flyweights cause the speeder spring to expand.

This expansion of the speeder spring causes the speeder to open the

throttle to the amount of the charge admitted to the engine. Increase

60. Mechanical governors usually respond slowly when the speed is changed.

This slow acting governors allows engine speed to change much before

the amount of ..is changed. Charge

61. To correct the first error, the governor may make as a change in the opposite direction.

This hunting effect is a major fault of.governors.

Mechanical/Centrifugal

Hydraulic Governors:- 62. In the hydraulic governor, the control elements are the same and

operate the same as in the mechanical governor.

But the speeder rod is connected to a pilot valve instead of being

connected directly to the . Throttle

63. Any movement by the pilot valve is transmitted immediately by hydraulic pressure to the power piston in a hydraulic cylinder.

The hydraulic power piston moves instantly as a result of the transmitted

force, and because the throttle is connected directly to this piston it

..instantly too. Moves

64. In the hydraulic governor, too, an increase in engine speed is translated into movement of the throttle to decrease the amount of

charge to the engine.

A decrease in engine speed is translated into a movement of the throttle

to the amount of charge to the engine. Increase

65. Because hydraulic fluid transmits change far more rapidly than mechanical linkage, the hydraulic governor is more sensitive, it

can maintain a more nearly..engine speed. Constant/ Steady

66. When it is possible to maintain a more constant speed, the danger of the engine surging is eliminated.

When engine speed is constant, the transmission of power to the driven

unit is more. Even/ Constant

When power from the engine is transmitted at a nearly constant rate, the

effectiveness of the driving and driven units is (greater / less).

Greater

Overspeed Trip Mechanism:-

67. The governor controls the engine speed under normal conditions,

but sometimes emergency conditions occur.

When the engine is fully loaded and the load is suddenly removed, the

engine may run away or Overspeed

68. When the load is suddenly removed from a fully loaded engine, the governor may react too slowly, or may stick and nor react at all.

If the fuel is not shut off, speed continues to .until the engine flies apart.

Increase

69. A trip pin is used to cut off the ignition or the.supply in an emergency.

Fuel

70. The trip pin consists of an unbalanced weight held in place in the governor shaft by a spring.

If the engine over speeds, centrifugal force pushes a ..out of the shaft.

Unbalanced weight/ Trip pin

71. When the engine over speed, the trip pin moves out against the over speed latch.

The latch releases a trip lever which is pulled down and held by a Spring

72. The trip lever spring pulls the fuel shutoff lever down. This fuel shutoff lever cuts off the.supply to the engine.

Fuel

73. To restart the engine, the over speed trip must be reset by hand. The over speed trip is not like the governor, because the over speed trip

cannot..itself automatically. Reset/ Adjust

74. There are other types of over speed trip devices, including over speed governors.

Overspeed governors are emergency controls which take over and slow

the engine down by reducing its fuel supply if the regular

governor Fails

75. Lets Review Carburetors are needed with (liquid / gaseous) fuels.

Liquid

The Carburetor .. the fuel and the air. Mixes

In a gas fuel engine, fuel may be fed directly to the cylinders through

a ..line. Header

It may also be run through a valve. Mixing

A.controls the amount of charge fed into a cylinder. Throttle

The throttle can be automatically controlled by a . Governor

The of the engine is controlled by a throttle governor system. A (Centrifugal / Hydraulic) governor is more powerful.

Hydraulic

Electrical System:- 76. An IC engine takes chemical energy stored in the fuel and changes

this chemical energy to heat energy.

This heat energy is then changed to the.energy of the shafts rotation.

Mechanical

77. To start this whole reaction the fuel must first be mixed with air and burnt.

To burn, the air fuel must be . Ignited

78. A spark plug is usually used to ignite the air-fuel charge. The spark plug needs (Electrical / Mechanical) energy.

Electrical

79. Energy to ignite the charge is provided by the system. Electrical

80. Material which can carry electrical energy from one place to another is called a conductor.

A conductor is a pipeline for carrying energy. Electrical

81. Most metals are good conductors. (Copper / Rubber) is a good electrical conductor.

Copper

82. For electricity to flow, it must have an uninterrupted path, called a circuit.

The circuit is made out of a (Conducting / Non-conducting) material.

Conducting

83. The components of the engines electrical system are connected in a ..

Circuit

84. Electricity flows from a source, through the components of a system, to the user of the electricity and then back to the source.

In this system, the is the source of power and the ..is the user.

Battery, Light/Bulb

85. The drawings show two electrical circuits.

No electricity is reaching bulb A because the circuit is .

Open / Broken

86. Electricity flows only through (Closed / Open) circuits. Closed

87. An electric light switch turns light on and off by anda circuit.

Opening / Closing

88. An ..switch for an engine turns on the electrical system by closing a circuit.

Ignition

89. Lets say current flows in a copper wire, like water flowing through a pipe.

The electricity, like the water, does not flow unless there is

something..it through the line. Forcing

90. Voltage is the .which electricity through a wire. Force

91. The force which moves electricity through the circuit is called ..

Voltage

Battery:-

92. All electrical systems need a primary source of electricity. In a battery system, the battery is the (Primary source / User) of the

electricity.

Primary Source

93. The battery releases energy which is stored in chemical form.

Electrical energy

94. A battery uses ..energy to produce electrical energy. Chemical energy

95. Remember, we said that electricity must be forced through the circuit.

The battery is the source of electricity and the source of .. Voltage

96. We know that the spark is produced at the spark plug.

A spark is formed when the electricity is forced to jump across a between the two electrodes of a spark plug.

Gap

97. It takes a tremendous amount of force to make the electricity jump across this gap.

The voltage must be very (High / Low).

High

98. A battery produces electricity at 6 to 12 volts. This (Is / Is not) enough voltage to produce a spark at a spark plug.

Is not

99. An ignition coil may be used to increase battery voltage.

An ignition coil consists of two coils of wire wound around a

Core

100. It uses low voltage current in one coil to generate (Low / Higher) voltage current in the other.

Higher

101. Both the magneto and pulse generator generate current directly. They (Need / Do not need) a battery ot other source of low voltage

current.

Do not need

102. The relatively low voltage current (but higher than battery voltage) produced by the low voltage magneto and the pulse generator

passes through the distributor into a high tension coil at each

cylinder.

This coil (Increases / Decreases) the voltage even more.

Increases

103. The high voltage magneto uses a built in distributor and high tension coil to increase voltage. The high voltage current pulse

from this high tension coil is used by the Spark plug

Distributor:- 104. In an IC engine, the fuel-air mixture must ignite only at the

beginning of the stroke. Power

105. The spark (Must / Must not) occur during the other three events.

Must not

106. The device which times the spark for each cylinder is the Distributor.

The distributor allows current into a spark plug only to start the . stroke of that particular cylinder.

Power

107. The distributor acts like a moving switch. When electricity is needed by the spark plug, the distributor (Opens /

Closes) a circuit to that spark plug.

Closes

108. When electricity is not needed by the cylinder, the circuit to that cylinder must be

Opened

109. The distributor opens and closes each circuit in relation to the power stroke of each cylinder.

When the switch is at point 1, cylinder..fires.

1

110. Cylinders 2, 4 and 3 follow cylinder 1. This is the order that the .stroke comes in the cylinders.

Power

111. The distributor shaft is turned, through a gear train, by the crankshaft.

Just as the camshaft times the valves, the ..shaft times the distributor.

Distributor

112. Unlike magnetos and batteries, . produce electric current in spurts, rather than in a steady stream.

Pulse generators

113. In engines equipped with a pulse generator, the electrical spurts can be timed so that one spurt occurs for a power event in each

cylinder.

Engines with a pulse generator (Need / Do not need) a separate

distributor.

Do not need

114. Lets Review: Batteries produce (High / Low) voltage.

Low

Most large industrial engines (need / Do not need) a battery.

Do not need

Usually, large engines use a ..or a .to produce current. Magneto, Pulse Generator

Low voltage magnetos (Need / Do not need) an ignition coil.

Do not need

Current from the low voltage magneto or pulse generator is (Increased /

Decreased) by the high tension coil at each cylinder.

Increased

Current from high voltage magneto is increased by a single ignition coil

built into the Magneto

The times the spark for both low and high voltage magnetos. Distributor

With a (Magneto / Pulse generator / Battery), the distributor is not

needed.

Pulse generator

Diesel Engines:- 115. All IC engines burn fuel inside a cylinder to produce power. This power is used to drive the .

Pistons

116. IC engines are separated into two general classes. They are classified according to the way the is ignited.

Fuel / Charge

117. The gas or gasoline fueled engine uses a ..to ignite the charge.

Spark / Spark plug

118. Diesel engines do not need a spark to ignite the charge. When air is compressed, its temperature increases, even if heat is not added.

If the air is compressed enough, its temperature increases enough to

..a jet of fuel sprayed into the air.

Ignite

119. Diesel engines are (Spark ignition / compression ignition) engines. Compression ignition

120. Diesel engines compress air inside the cylinder to a very high pressure.

The air gets very hot, and when the fuel mist is injected into it, the

fuel.. immediately. Ignites

121. A diesel engine, by compressing air in the cylinder and then injecting fuel into the cylinders, eliminates the need to mix fuel

and air separately.

It needs no (Carburetor / fuel).

Carburetor

122. It uses the heat of compression to ignite the fuel and thus needs no system.

Ignition

123. High pressure fuel is pumped into the cylinders at, or slightly before, the end of the compression stroke.

The fuel .and the power stroke begins. Ignites

124. Diesel fuel oil is thicker than most other IC engine fuels. Fuel injector nozzles are used to break this fuel oil into very small

particles so that it can.. Burn

125. The drawing shows a high pressure fuel injection nozzle.

When high pressure fuel enters the engine through the nozzle tip, it is

broken into a ..mist. Fine / Small

127. The fuel is to the fuel injection nozzle by a fuel pump. Pumped

128. The speed of the diesel engine is controlled by adjusting the .of fuel injected into the cylinder.

Amount

129. Diesel engines may be either 2-cycle or 4-cycle engines.

Engine (A / B) is a 4-cycle engine.

A

130. Engine B has replaced intake and exhaust valves in the cylinder

head with two .in the cylinder wall. Ports

131. In the diesel engine, fuel injection starts the power event. Fuel must be injected into the compressed air at the ...time to give maximum power output.

Proper

132. The camshaft times the combustion cycle. Gears relate the camshaft to the .so that the camshaft and the cams can time the combustion events.

Crankshaft

133. The fuel injection pump is sometimes run off a separate shaft

driven by the crankshaft.

A gear also times this fuel injection. Pump

133. A diesel engine may also have a .to control engine speed automatically.

Governor

134. The compression ratio in the diesel engine is much higher than a gasoline engine.

They build up much (More / Less) pressure.

More

135. Thus, the pistons, crankshaft, and connecting rods are built much stronger in a (Diesel / Gasoline) engine.

Diesel

Review and Summary

136. The drawing shows a simplified IC engine. Name the lettered

parts.

A. Carburetor B. Valve C. Spark plug D. Cylinder E. Piston F. Camshaft G. Connecting rod H. Crankshaft I.

137. The engine (Is / Is not) a diesel. Is not

138. It operates on a (2 / 4)-stroke cycle.

4