IC Engines Practice Set-1

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

Napthene, aromatics, paraffin

Napthene, paraffin, aromatic

Paraffin, aromatic, napthene

Paraffin, napthene, aromatic

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

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

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

3. 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

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

Design of crankshaft

Number of cylinders

Arrangement of the cylinders

All of these

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

Turbulence

Supercharging

Scavenging

Pre-ignition

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

Turbulence

Pre-ignition

Supercharging

Detonation

7. 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

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

9: 1

15: 1

6: 1

12: 1

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

Ignition delay

Detonation

Pre-ignition

Auto-ignition

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

2000-2500°C

1000-1500°C

500-1000°C

1500-2000°C

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11. Detonation is harmful due to

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

None of the above

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

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

Both mild and big explosions occurs simultaneously

Never occurs

First a mild explosion followed by a bi explosion

First a big explosion followed by a mil explosion

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

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

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

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

May start and end anywhere

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

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

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

Delay period

Carburetion

Supercharging

Turbulence

16. A stoichiometric air-fuel ratio is

Lean mixture

Chemically correct mixture

Rich mixture for idling

Rich mixture for over loads

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

Increase up to certain limit and then decrease

Remain same

Decrease

Increase

18. Pick up the wrong statement about supercharging

Supercharging at high altitudes is essential

Supercharging reduces knocking in diesel engines

Supercharging results in fuel economy

There can be limited supercharging in petrol engines because of detonation

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

Equal to

Four-times

Twice

One-half

20. Supercharging is the process of

Providing forced cooling air

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

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21. Pour point of fuel oil is the

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

Temperature at which it solidifies or congeals

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

Increase linearly

Decrease parabolically

Increase parabolically

Decrease linearly

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

Maximum pressure developed

Average pressure

Minimum pressure

Instantaneous pressure at any instant

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

High self ignition temperature

Low volatility

All of these

Higher viscosity

25. In compression ignition engines, swirl denotes a

None of the above

Rotary motion of the gases in the chamber

Radial motion of the gases in the chamber

Haphazard motion of the gases in the chamber

26. 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

Supercharging

Detonation

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

Kerosene

Gasoline

Diesel

Fuel oil

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

High

Low

Very low

Very high

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

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

May open and close anywhere

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

Opens at bottom dead centre and closes at top dead centre

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

None of these

1+ r^{γ - 1}

1- r^{γ - 1}

1 - (1/r^{γ - 1})

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

Increase

None of these

Remain same

Decrease

32. Pick up the false statement

Thermal efficiency of diesel engine is about 34%

S.I. engines are quality governed engines

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

High speed compression engines operate on dual combustion cycle

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

Air and fuel

Air and lub oil

Air alone

Fuel alone

34. Compression ratio of I.C. Engines is

Swept volume/cylinder volume

Ratio of pressure after compression and before compression

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

35. 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 10° after top dead center and closes 20° before the bottom dead center

May open or close anywhere

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

36. The ignition quality of petrol is expressed by

All of these

Cetane number

Octane number

Calorific value

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

Same

Less

More

May be more or less depending on engine capacity

38. An engine indicator is used to determine the following

Temperature

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

Volume of cylinder

Speed

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

Between the pistons

Below the piston

Above the piston

There is no such criterion

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

(C) Both (A) and (B)

(B) Increasing the engine speed

(D) None of these

(A) Retarding the spark

IC Engines Practice Set-1

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