IC Engines Practice Set-1

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

Air alone

Fuel alone

Air and fuel

Air and lub oil

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

There is no such criterion

Between the pistons

Above the piston

Below the piston

3. In compression ignition engines, swirl denotes a

None of the above

Radial motion of the gases in the chamber

Haphazard motion of the gases in the chamber

Rotary motion of the gases in the chamber

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

Decrease

Increase

None of these

Remain same

5. 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

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

May start and end anywhere

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

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

7. Supercharging is the process of

Supplying compressed air to remove combustion products fully

Providing forced cooling air

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

8. 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

9. An engine indicator is used to determine the following

Speed

Volume of cylinder

Temperature

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

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

Very high

High

Low

Very low

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

May be more or less depending on engine capacity

Same

More

Less

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

Supercharging

Pre-ignition

Detonation

Turbulence

13. Compression ratio of I.C. Engines is

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

Swept volume/cylinder volume

Ratio of pressure after compression and before compression

14. A stoichiometric air-fuel ratio is

Rich mixture for idling

Lean mixture

Rich mixture for over loads

Chemically correct mixture

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

Average pressure

Maximum pressure developed

Instantaneous pressure at any instant

Minimum pressure

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

Turbulence

Carburetion

Supercharging

Delay period

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

Number of cylinders

Design of crankshaft

Arrangement of the cylinders

All of these

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

Ignition delay

Pre-ignition

Auto-ignition

Detonation

19. 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}

None of these

1 - (1/r^{γ - 1})

1- r^{γ - 1}

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

Diesel

Gasoline

Kerosene

Fuel oil

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

Supercharging

Scavenging

Pre-ignition

Turbulence

22. The ignition quality of petrol is expressed by

Calorific value

Cetane number

Octane number

All of these

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

6: 1

12: 1

15: 1

9: 1

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

Increase up to certain limit and then decrease

Increase

Decrease

Remain same

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

One-half

Twice

Four-times

Equal to

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

Paraffin, aromatic, napthene

Paraffin, napthene, aromatic

Napthene, aromatics, paraffin

Napthene, paraffin, aromatic

27. Pick up the wrong statement about supercharging

Supercharging reduces knocking in diesel engines

Supercharging at high altitudes is essential

There can be limited supercharging in petrol engines because of detonation

Supercharging results in fuel economy

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

500-1000°C

1000-1500°C

2000-2500°C

1500-2000°C

29. 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

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

Temperature at which it solidifies or congeals

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

Polymerisation

Supercharging

Scavenging

Detonation

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

(D) None of these

(B) Increasing the engine speed

(A) Retarding the spark

(C) Both (A) and (B)

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

All of these

Low volatility

Higher viscosity

High self ignition temperature

33. 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

34. Detonation is harmful due to

None of the above

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

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

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

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

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

36. 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

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

35 kg/cm

6 kg/cm

12 kg/cm

20 kg/cm

38. 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

39. 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° after bottom dead centre and closes at 10° before top dead centre

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

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

Decrease linearly

Increase linearly

Decrease parabolically

Increase parabolically

IC Engines Practice Set-1

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