IC Engines Practice Set-1

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

Starts at bottom dead centre and ends at top dead centre

May start and end anywhere

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

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

2. Supercharging is the process of

Supplying compressed air to remove combustion products fully

Injecting excess fuel for raising more loads

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

Providing forced cooling air

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

Pre-ignition

Detonation

Supercharging

Turbulence

4. Detonation is harmful due to

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

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

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

None of the above

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

(B) Increasing the engine speed

(D) None of these

(C) Both (A) and (B)

(A) Retarding the spark

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

Decrease

Remain same

Increase

Increase up to certain limit and then decrease

7. Pick up the false statement

High speed compression engines operate on dual combustion cycle

S.I. engines are quality governed engines

Thermal efficiency of diesel engine is about 34%

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

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

6 kg/cm

20 kg/cm

35 kg/cm

12 kg/cm

9. 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 40° before top dead center and ends at 40° after top dead center

May start and end anywhere

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

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

All of these

Low volatility

Higher viscosity

High self ignition temperature

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

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

May start and end anywhere

Fuel injection starts at 10° before 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

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

High

Low

Very high

Very low

13. In compression ignition engines, swirl denotes a

Rotary motion of the gases in the chamber

None of the above

Radial motion of the gases in the chamber

Haphazard motion of the gases in the chamber

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

12: 1

6: 1

9: 1

15: 1

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

May open and close anywhere

Opens at bottom dead centre and closes at top dead centre

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

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

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

All of these

Number of cylinders

Arrangement of the cylinders

Design of crankshaft

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

There is no such criterion

Below the piston

Between the pistons

Above the piston

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

1- r^{γ - 1}

1+ r^{γ - 1}

1 - (1/r^{γ - 1})

None of these

19. Pick up the wrong statement about supercharging

There can be limited supercharging in petrol engines because of detonation

Supercharging reduces knocking in diesel engines

Supercharging at high altitudes is essential

Supercharging results in fuel economy

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

Increase parabolically

Decrease parabolically

Increase linearly

Decrease linearly

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

Auto-ignition

Pre-ignition

Ignition delay

Detonation

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

Supercharging

Delay period

Turbulence

Carburetion

23. An engine indicator is used to determine the following

Volume of cylinder

Speed

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

Temperature

24. The ignition quality of petrol is expressed by

Cetane number

Calorific value

Octane number

All of these

25. 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

26. Compression ratio of I.C. Engines is

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

Volume displaced by piston per stroke and clearance volume in cylinder

Ratio of pressure after compression and before compression

Swept volume/cylinder volume

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

First a big explosion followed by a mil explosion

Never occurs

Both mild and big explosions occurs simultaneously

First a mild explosion followed by a bi explosion

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

Increase

Remain same

Decrease

None of these

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

Diesel

Kerosene

Gasoline

Fuel oil

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

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

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

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

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

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

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

May open or close anywhere

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

Opens at top dead center and closes at bottom dead center

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

Scavenging

Pre-ignition

Supercharging

Turbulence

33. Pour point of fuel oil is the

It catches fire without external aid

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

Temperature at which it solidifies or congeals

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

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

Maximum pressure developed

Instantaneous pressure at any instant

Minimum pressure

Average pressure

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

Napthene, paraffin, aromatic

Paraffin, aromatic, napthene

Paraffin, napthene, aromatic

Napthene, aromatics, paraffin

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

Air alone

Air and fuel

Fuel alone

Air and lub oil

37. 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

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

Detonation

Supercharging

Polymerisation

Scavenging

39. A stoichiometric air-fuel ratio is

Rich mixture for idling

Lean mixture

Chemically correct mixture

Rich mixture for over loads

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

Equal to

Twice

One-half

Four-times

IC Engines Practice Set-1

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