IC Engines Practice Set-1

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

Average pressure

Maximum pressure developed

Instantaneous pressure at any instant

Minimum pressure

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

Twice

Equal to

Four-times

One-half

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

Supercharging

Detonation

Turbulence

Pre-ignition

4. An engine indicator is used to determine the following

Temperature

Speed

Volume of cylinder

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

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

All of these

Arrangement of the cylinders

Number of cylinders

Design of crankshaft

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

May open and close anywhere

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

Opens at bottom dead centre and closes at top dead centre

7. In compression ignition engines, swirl denotes a

Rotary motion of the gases in the chamber

Haphazard motion of the gases in the chamber

Radial motion of the gases in the chamber

None of the above

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

Decrease parabolically

Increase linearly

Increase parabolically

Decrease linearly

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

May start and end anywhere

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

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

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

10. 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

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

20 kg/cm

35 kg/cm

12 kg/cm

6 kg/cm

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

Same

May be more or less depending on engine capacity

Less

More

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

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

May start and end anywhere

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

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

14. Supercharging is the process of

Providing forced cooling air

Injecting excess fuel for raising more loads

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

15. 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 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

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

None of these

Decrease

Remain same

Increase

17. 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

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

(C) Both (A) and (B)

(B) Increasing the engine speed

(A) Retarding the spark

(D) None of these

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

500-1000°C

1500-2000°C

2000-2500°C

1000-1500°C

20. Pick up the wrong statement about supercharging

Supercharging reduces knocking in diesel engines

There can be limited supercharging in petrol engines because of detonation

Supercharging results in fuel economy

Supercharging at high altitudes is essential

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21. Pour point of fuel oil is the

Temperature at which it solidifies or congeals

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

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

Supercharging

Turbulence

Pre-ignition

Scavenging

23. Pick up the false statement

High speed compression engines operate on dual combustion cycle

S.I. engines are quality governed engines

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

Thermal efficiency of diesel engine is about 34%

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

Higher viscosity

High self ignition temperature

All of these

Low volatility

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

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

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

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

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

Opens at top dead center and closes at bottom dead center

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

Auto-ignition

Ignition delay

Detonation

Pre-ignition

28. The ignition quality of petrol is expressed by

Cetane number

Calorific value

All of these

Octane number

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

9: 1

15: 1

12: 1

6: 1

30. 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})

1- r^{γ - 1}

None of these

1+ r^{γ - 1}

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

Air and lub oil

Fuel alone

Air alone

Air and fuel

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

Turbulence

Carburetion

Delay period

Supercharging

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

Remain same

Increase up to certain limit and then decrease

Increase

Decrease

34. 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

35. Compression ratio of I.C. Engines is

Swept volume/cylinder volume

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

Ratio of pressure after compression and before compression

Volume displaced by piston per stroke and clearance volume in cylinder

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

Scavenging

Polymerisation

Supercharging

Detonation

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

Below the piston

There is no such criterion

Between the pistons

Above the piston

38. 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

39. A stoichiometric air-fuel ratio is

Lean mixture

Chemically correct mixture

Rich mixture for idling

Rich mixture for over loads

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

Kerosene

Diesel

Fuel oil

Gasoline

IC Engines Practice Set-1

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