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IC Engines
0

IC Engines Practice Set-1

September 5, 2021

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Page 1 of 4

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

Equal to

One-half

Twice

Four-times

2. The ignition quality of petrol is expressed by

Octane number

Calorific value

All of these

Cetane number

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

Gasoline

Diesel

Fuel oil

Kerosene

4. An engine indicator is used to determine the following

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

Speed

Temperature

Volume of cylinder

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

(B) Increasing the engine speed

(A) Retarding the spark

(D) None of these

(C) Both (A) and (B)

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

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

May start and end anywhere

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

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

Napthene, aromatics, paraffin

Napthene, paraffin, aromatic

Paraffin, napthene, aromatic

Paraffin, aromatic, napthene

8. 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

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

All of these

Arrangement of the cylinders

Number of cylinders

Design of crankshaft

10. Supercharging is the process of

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

Providing forced cooling air

Injecting excess fuel for raising more loads

Page 2 of 4

11. Compression ratio of I.C. Engines is

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

Ratio of pressure after compression and before compression

Swept volume/cylinder volume

Volume displaced by piston per stroke and clearance volume in cylinder

12. The air standard efficiency of an I.C. engine is given by (where r = Compression ratio, and γ = Ratio of specific heats)

None of these

1- r^{γ - 1}

1+ r^{γ - 1}

1 - (1/r^{γ - 1})

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

Air and fuel

Air alone

Air and lub oil

Fuel alone

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

Same

More

Less

May be more or less depending on engine capacity

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

Increase up to certain limit and then decrease

Increase

Remain same

Decrease

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

6: 1

9: 1

15: 1

12: 1

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

Delay period

Supercharging

Carburetion

Turbulence

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

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

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

May start and end anywhere

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

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

Minimum pressure

Average pressure

Maximum pressure developed

Instantaneous pressure at any instant

20. 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.

Page 3 of 4

21. Detonation is harmful due to

High intensity of knock causes crankshaft vibration and the engine runs rough

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

None of the above

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

Pre-ignition

Detonation

Auto-ignition

Ignition delay

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

Decrease linearly

Increase linearly

Decrease parabolically

Increase parabolically

24. Pick up the wrong statement about supercharging

There can be limited supercharging in petrol engines because of detonation

Supercharging reduces knocking in diesel engines

Supercharging at high altitudes is essential

Supercharging results in fuel economy

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

12 kg/cm

20 kg/cm

35 kg/cm

6 kg/cm

26. Pour point of fuel oil is the

It catches fire without external aid

Temperature at which it solidifies or congeals

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

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

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

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

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

Detonation

Turbulence

Pre-ignition

Supercharging

29. Pick up the false statement

Thermal efficiency of diesel engine is about 34%

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

30. A stoichiometric air-fuel ratio is

Lean mixture

Rich mixture for over loads

Rich mixture for idling

Chemically correct mixture

Page 4 of 4

31. 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

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

Between the pistons

There is no such criterion

Below the piston

Above the piston

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

1500-2000°C

1000-1500°C

500-1000°C

2000-2500°C

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

Decrease

Remain same

Increase

None of these

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

Low

Very low

High

Very high

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

Never occurs

Both mild and big explosions occurs simultaneously

First a big explosion followed by a mil explosion

First a mild explosion followed by a bi explosion

37. 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

May open and close anywhere

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

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

Turbulence

Supercharging

Pre-ignition

Scavenging

39. 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

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

Higher viscosity

Low volatility

High self ignition temperature

All of these

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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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