IC Engines Practice Set-1

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1. 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

2. 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

3. 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

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

Low

Very low

Very high

High

5. Pick up the wrong statement about supercharging

Supercharging at high altitudes is essential

Supercharging results in fuel economy

There can be limited supercharging in petrol engines because of detonation

Supercharging reduces knocking in diesel engines

6. Pour point of fuel oil is the

Temperature at which it solidifies or congeals

It catches fire without external aid

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

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

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

Auto-ignition

Detonation

Ignition delay

Pre-ignition

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

Napthene, paraffin, aromatic

Paraffin, napthene, aromatic

Napthene, aromatics, paraffin

Paraffin, aromatic, napthene

9. 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

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

Supercharging

Pre-ignition

Turbulence

Detonation

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

Average pressure

Instantaneous pressure at any instant

Maximum pressure developed

Minimum pressure

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

Diesel

Gasoline

Fuel oil

Kerosene

13. 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 bottom dead centre and closes at top dead centre

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

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

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

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

None of these

Remain same

Decrease

Increase

16. Pick up the false statement

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%

High speed compression engines operate on dual combustion cycle

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

500-1000°C

2000-2500°C

1000-1500°C

1500-2000°C

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

(D) None of these

(C) Both (A) and (B)

(A) Retarding the spark

(B) Increasing the engine speed

19. 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

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

May open or close anywhere

Opens at top dead center and closes at bottom dead center

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

Increase

Increase up to certain limit and then decrease

Remain same

Decrease

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21. 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

22. An engine indicator is used to determine the following

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

Temperature

Speed

Volume of cylinder

23. 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

24. Detonation is harmful due to

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

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

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

Less

Same

More

May be more or less depending on engine capacity

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

Number of cylinders

Arrangement of the cylinders

Design of crankshaft

All of these

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

Both mild and big explosions occurs simultaneously

First a mild explosion followed by a bi explosion

Never occurs

First a big explosion followed by a mil explosion

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

Increase parabolically

Decrease linearly

Increase linearly

Decrease parabolically

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

Air and fuel

Air alone

Fuel alone

Air and lub oil

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

Turbulence

Scavenging

Pre-ignition

Supercharging

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31. The ignition quality of petrol is expressed by

Cetane number

Octane number

Calorific value

All of these

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

6: 1

9: 1

12: 1

15: 1

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

Supercharging

Scavenging

Polymerisation

Detonation

34. 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

35. Compression ratio of I.C. Engines is

Ratio of pressure after compression and before compression

Volume displaced by piston per stroke and clearance volume in cylinder

Swept volume/cylinder volume

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

36. 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

37. A stoichiometric air-fuel ratio is

Rich mixture for idling

Rich mixture for over loads

Chemically correct mixture

Lean mixture

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

Carburetion

Supercharging

Delay period

Turbulence

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

Low volatility

High self ignition temperature

Higher viscosity

All of these

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

6 kg/cm

20 kg/cm

12 kg/cm

35 kg/cm

IC Engines Practice Set-1

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