IC Engines Practice Set-1

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1. The ignition quality of petrol is expressed by

Octane number

All of these

Cetane number

Calorific value

2. The operation of forcing additional air under pressure in the engine cylinder is known as

Supercharging

Scavenging

Pre-ignition

Turbulence

3. The knocking in spark ignition engines can be reduced by

(C) Both (A) and (B)

(A) Retarding the spark

(B) Increasing the engine speed

(D) None of these

4. The firing order in an I.C. engine depends upon

Number of cylinders

Arrangement of the cylinders

All of these

Design of crankshaft

5. In a four stroke cycle petrol engine, the compression

Starts at 40° after bottom dead centre and ends at 30° before top dead centre

Starts at 40° before bottom dead centre and ends at 30° after bottom dead centre

Starts at bottom dead centre and ends at top dead centre

May start and end anywhere

6. Pick up the wrong statement about supercharging

Supercharging at high altitudes is essential

There can be limited supercharging in petrol engines because of detonation

Supercharging results in fuel economy

Supercharging reduces knocking in diesel engines

7. If the temperature of intake air in internal combustion engine increases, then its efficiency will

Decrease

Remain same

None of these

Increase

8. In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as

Polymerisation

Scavenging

Detonation

Supercharging

9. The air standard efficiency of an I.C. engine is given by (where r = Compression ratio, and γ = Ratio of specific heats)

1 - (1/r^{γ - 1})

None of these

1- r^{γ - 1}

1+ r^{γ - 1}

10. The pressure at the end of compression in the case of diesel engine is of the order of

12 kg/cm

6 kg/cm

35 kg/cm

20 kg/cm

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11. Pick up the false statement

S.I. engines are quality governed engines

High speed compression engines operate on dual combustion cycle

Thermal efficiency of diesel engine is about 34%

Theoretically correct mixture of air and petrol is approximately 15:1

12. Detonation is harmful due to

None of the above

Excessive turbulence which removes most of the insulating gas boundary layer from the cylinder walls

Increase in the rate of heat transfer, there is a reduction in the power output and efficiency of the engine

High intensity of knock causes crankshaft vibration and the engine runs rough

13. The mean effective pressure obtained from engine indicator indicates the

Instantaneous pressure at any instant

Maximum pressure developed

Average pressure

Minimum pressure

14. Which of the following is the lightest and most volatile liquid fuel?

Fuel oil

Diesel

Kerosene

Gasoline

15. Crankcase explosion in I.C. engines usually occurs as

Never occurs

Both mild and big explosions occurs simultaneously

First a mild explosion followed by a bi explosion

First a big explosion followed by a mil explosion

16. The maximum temperature in the I.C. engine cylinder is of the order of

1500-2000°C

1000-1500°C

500-1000°C

2000-2500°C

17. A stoichiometric air-fuel ratio is

Rich mixture for idling

Lean mixture

Rich mixture for over loads

Chemically correct mixture

18. In a four stroke cycle diesel engine, the compression

Starts at 40° after bottom dead center and ends at 10° before top dead center

Starts at top dead center and ends at 40° before bottom dead center

Starts at 40° before top dead center and ends at 40° after top dead center

May start and end anywhere

19. The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is

Same

More

May be more or less depending on engine capacity

Less

20. An engine indicator is used to determine the following

Speed

m.e.p. and I.H.P.

Volume of cylinder

Temperature

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21. The probability of knocking in diesel engines is increased by

All of these

High self ignition temperature

Higher viscosity

Low volatility

22. In a typical medium speed, 4-stroke cycle diesel engine

Fuel injection starts at 10° before top dead center and ends at 20° after top dead center

May start and end anywhere

Fuel injection starts at top dead center and ends at 20° after top dead center

Fuel injection starts at just before top dead center and ends just after top dead center

23. In a four stroke cycle diesel engine, the exhaust valve

Opens at 30° before bottom dead centre and closes at 10° after top dead centre

May open and close anywhere

Opens at 30° after bottom dead centre and closes at 10° before top dead centre

Opens at bottom dead centre and closes at top dead centre

24. The loud pulsating noise heard within the cylinder of an internal combustion engine is known as

Turbulence

Pre-ignition

Supercharging

Detonation

25. Supercharging is the process of

Injecting excess fuel for raising more loads

Providing forced cooling air

Supplying compressed air to remove combustion products fully

Supplying the intake of an engine with air at a density greater than the density of the surrounding atmosphere

26. The theoretically correct air fuel ratio for petrol engine is of the order of

9: 1

12: 1

15: 1

6: 1

27. The ignition of the charge by some hot surface within the engine before the passage of spark is called

Pre-ignition

Ignition delay

Auto-ignition

Detonation

28. Which one of the following engines will have heavier flywheel than the remaining ones?

30 kW two-stroke petrol engine running at 1500 r.p.m.

30 kW four-stroke petrol engine running at 1500 r.p.m.

30 kW two-stroke diesel engine running at 750 r.p.m.

30 kW four-stroke diesel engine running at 750 r.p.m.

29. Pour point of fuel oil is the

Temperature at which it solidifies or congeals

Minimum temperature to which oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame

It catches fire without external aid

Indicated by 90% distillation temperature i.e., when 90% of sample oil has distilled off

30. In compression ignition engines, swirl denotes a

Rotary motion of the gases in the chamber

Radial motion of the gases in the chamber

Haphazard motion of the gases in the chamber

None of the above

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31. The working pressure and temperature inside the cylinder of an internal combustion engine is _________ as compared to a steam engine.

Low

High

Very low

Very high

32. If the temperature of intake air in IC engines is lowered, then its efficiency will

Decrease

Increase

Remain same

Increase up to certain limit and then decrease

33. In a typical medium speed 4-stroke cycle diesel engine the inlet valve

Opens at top dead center and closes at bottom dead center

Opens at 20° before top dead center and closes at 35° after the bottom dead center

Opens at 10° after top dead center and closes 20° before the bottom dead center

May open or close anywhere

34. Number of working strokes per min. for a four stroke cycle engine are _________ the speed of the engine in r.p.m.

Four-times

Twice

Equal to

One-half

35. Which of the following medium is compressed in a Diesel engine cylinder?

Air and lub oil

Air and fuel

Air alone

Fuel alone

36. The rating of a diesel engine, with increase in air inlet temperature, will

Increase linearly

Decrease linearly

Decrease parabolically

Increase parabolically

37. The fuels in order of decreasing knock tendency for spark ignition engines are

Paraffin, napthene, aromatic

Paraffin, aromatic, napthene

Napthene, paraffin, aromatic

Napthene, aromatics, paraffin

38. In the opposed piston diesel engine, the combustion chamber is located

Below the piston

Between the pistons

There is no such criterion

Above the piston

39. The operation of forcing additional air under pressure into the engine cylinder is known as

Supercharging

Delay period

Turbulence

Carburetion

40. Compression ratio of I.C. Engines is

Swept volume/cylinder volume

Ratio of pressure after compression and before compression

Volume displaced by piston per stroke and clearance volume in cylinder

The ratio of volumes of air in cylinder before compression stroke and after compression stroke

IC Engines Practice Set-1

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