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IC Engines
0

IC Engines Practice Set-1

September 5, 2021

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Page 1 of 4

1. 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

None of the above

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

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

Scavenging

Pre-ignition

Supercharging

Turbulence

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

12: 1

15: 1

6: 1

9: 1

4. 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

Less

More

Same

5. The ignition quality of petrol is expressed by

Octane number

All of these

Cetane number

Calorific value

6. 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

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

Turbulence

Detonation

Pre-ignition

Supercharging

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

First a big explosion followed by a mil explosion

Both mild and big explosions occurs simultaneously

First a mild explosion followed by a bi explosion

Never occurs

9. 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

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

High self ignition temperature

Higher viscosity

Low volatility

All of these

Page 2 of 4

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

Decrease parabolically

Increase linearly

Increase parabolically

Decrease linearly

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

(D) None of these

(A) Retarding the spark

(B) Increasing the engine speed

(C) Both (A) and (B)

13. An engine indicator is used to determine the following

Speed

Temperature

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

Volume of cylinder

14. Supercharging is the process of

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

Providing forced cooling air

Supplying compressed air to remove combustion products fully

Injecting excess fuel for raising more loads

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

Paraffin, aromatic, napthene

Napthene, paraffin, aromatic

Napthene, aromatics, paraffin

Paraffin, napthene, aromatic

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

Gasoline

Fuel oil

Kerosene

Diesel

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

Turbulence

Carburetion

Supercharging

Delay period

18. 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

19. 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

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

Auto-ignition

Pre-ignition

Detonation

Ignition delay

Page 3 of 4

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

Very low

Very high

Low

High

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

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

23. Compression ratio of I.C. Engines is

Ratio of pressure after compression and before compression

Swept volume/cylinder volume

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

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

Twice

One-half

Four-times

Equal to

25. 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

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

May start and end anywhere

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

26. 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

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

Air and lub oil

Air and fuel

Fuel alone

Air alone

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

Maximum pressure developed

Instantaneous pressure at any instant

Average pressure

Minimum pressure

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

1500-2000°C

500-1000°C

1000-1500°C

2000-2500°C

30. Pick up the wrong statement about supercharging

There can be limited supercharging in petrol engines because of detonation

Supercharging results in fuel economy

Supercharging reduces knocking in diesel engines

Supercharging at high altitudes is essential

Page 4 of 4

31. A stoichiometric air-fuel ratio is

Rich mixture for idling

Rich mixture for over loads

Lean mixture

Chemically correct mixture

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

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

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

May start and end anywhere

33. 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

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

May open and close anywhere

34. Pick up the false statement

Thermal efficiency of diesel engine is about 34%

High speed compression engines operate on dual combustion cycle

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

S.I. engines are quality governed engines

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

Design of crankshaft

Number of cylinders

All of these

Arrangement of the cylinders

36. 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 diesel engine running at 750 r.p.m.

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

37. In compression ignition engines, swirl denotes a

Rotary motion of the gases in the chamber

None of the above

Haphazard motion of the gases in the chamber

Radial motion of the gases in the chamber

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

6 kg/cm

35 kg/cm

12 kg/cm

20 kg/cm

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

Between the pistons

Below the piston

There is no such criterion

Above the piston

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

Increase

Decrease

None of these

Remain same

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A Demrot is the founder of VideRime Online Learning, a leading engineering website. He did his BE Civil and M.Tech Structure from RGPV University, Bhopal and has been working as an Assistant Professor in a reputed college.

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