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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

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

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

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

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

Napthene, aromatics, paraffin

Paraffin, aromatic, napthene

Paraffin, napthene, aromatic

Napthene, paraffin, aromatic

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

Below the piston

Above the piston

Between the pistons

There is no such criterion

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

(C) Both (A) and (B)

(A) Retarding the spark

(D) None of these

(B) Increasing the engine speed

6. Supercharging is the process of

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

Supplying compressed air to remove combustion products fully

Injecting excess fuel for raising more loads

Providing forced cooling air

7. 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

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

Arrangement of the cylinders

Design of crankshaft

All of these

Number of cylinders

9. An engine indicator is used to determine the following

Speed

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

Temperature

Volume of cylinder

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

Decrease parabolically

Decrease linearly

Increase parabolically

Increase linearly

Page 2 of 4

11. Pick up the wrong statement about supercharging

Supercharging reduces knocking in diesel engines

Supercharging results in fuel economy

Supercharging at high altitudes is essential

There can be limited supercharging in petrol engines because of detonation

12. 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}

1+ r^{γ - 1}

None of these

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

First a big explosion followed by a mil explosion

First a mild explosion followed by a bi explosion

Never occurs

Both mild and big explosions occurs simultaneously

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

Detonation

Turbulence

Pre-ignition

Supercharging

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

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

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

Increase

Decrease

None of these

Remain same

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

Fuel oil

Kerosene

Gasoline

Diesel

18. In compression ignition engines, swirl denotes a

None of the above

Rotary motion of the gases in the chamber

Haphazard motion of the gases in the chamber

Radial motion of the gases in the chamber

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

May start and end anywhere

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

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

20. Compression ratio of I.C. Engines is

Swept volume/cylinder volume

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

Ratio of pressure after compression and before compression

Page 3 of 4

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

Less

More

May be more or less depending on engine capacity

Same

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

Supercharging

Polymerisation

Detonation

Scavenging

23. Pour point of fuel oil is the

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

Temperature at which it solidifies or congeals

It catches fire without external aid

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

Pre-ignition

Turbulence

Scavenging

Supercharging

25. A stoichiometric air-fuel ratio is

Rich mixture for idling

Rich mixture for over loads

Lean mixture

Chemically correct mixture

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

20 kg/cm

6 kg/cm

35 kg/cm

12 kg/cm

27. 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° after bottom dead centre and ends at 30° before top dead centre

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

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

Maximum pressure developed

Minimum pressure

Average pressure

Instantaneous pressure at any instant

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

May open or close anywhere

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

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

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

2000-2500°C

1000-1500°C

1500-2000°C

500-1000°C

Page 4 of 4

31. Pick up the false statement

S.I. engines are quality governed engines

High speed compression engines operate on dual combustion cycle

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

Thermal efficiency of diesel engine is about 34%

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

Carburetion

Supercharging

Turbulence

Delay period

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

All of these

Low volatility

High self ignition temperature

Higher viscosity

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

Air and fuel

Air and lub oil

Air alone

Fuel alone

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

Detonation

Ignition delay

Pre-ignition

Auto-ignition

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

12: 1

15: 1

9: 1

6: 1

37. 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

One-half

Four-times

38. 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 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

39. The ignition quality of petrol is expressed by

Cetane number

Octane number

All of these

Calorific value

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

Remain same

Increase

Decrease

Increase up to certain limit and then decrease

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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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