Internal Combustion Engines (I.C. Engines) MCQ Questions & Answers

31

The mean effective pressure obtained from engine indicator indicates the

A) Maximum pressure developed B) Minimum pressure C) Instantaneous pressure at any instant D) Average pressure

Discuss

Answer & Solution

Answer: Option D

Solution:

The mean effective pressure obtained from engine indicator indicates the Average pressure

32

The accumulation of carbon in a cylinder results in increase of

A) Clearance volume B) Volumetric efficiency C) Ignition time D) Effective compression ratio

Discuss

Answer & Solution

Answer: Option D

Solution:

The accumulation of carbon in a cylinder results in increase of Effective compression ratio. -Decreased fuel efficiency -Decreased compression -Increased exhaust pollutants -Decreased oil life -Decreased ring life -Decreased spark plug life

33

If V₁ is the jet velocity and V₀ is the vehicle velocity, then propulsive efficiency of a turbojet engine is

A) $$\frac{{{{\text{V}}_1}}}{{{{\text{V}}_0} + {{\text{V}}_1}}}$$ B) $$\frac{{{{\text{V}}_0}}}{{{{\text{V}}_0} + {{\text{V}}_1}}}$$ C) $$\frac{{2{{\text{V}}_0}}}{{{{\text{V}}_0} + {{\text{V}}_1}}}$$ D) $$\frac{{2{{\text{V}}_1}}}{{{{\text{V}}_0} + {{\text{V}}_1}}}$$

Discuss

Answer & Solution

Answer: Option C

Solution:

If V₁ is the jet velocity and V₀ is the vehicle velocity, then propulsive efficiency of a turbojet engine is $$\frac{{2{{\text{V}}_0}}}{{{{\text{V}}_0} + {{\text{V}}_1}}}$$

34

Which of the following is false statement?
Excess quantities of sulphur in diesel fuel are Objectionable because it may cause the following

A) Piston ring and cylinder wear B) Formation of hard coating on piston skirts C) Oil sludge in the engine crank case D) Detonation

Discuss

Answer & Solution

Answer: Option D

Solution:

Excess quantities of sulphur in diesel fuel are Objectionable because it may cause Detonation

35

The basic requirement of a good combustion chamber is

A) Minimum turbulence B) Low compression ratio C) High thermal efficiency and power output D) Low volumetric efficiency

Discuss

Answer & Solution

Answer: Option C

Solution:

The basic requirement of a good combustion chamber is High thermal efficiency and power output. -High power output. -High thermal efficiency -low specific fuel consumption. -Smooth engine operation.

36

Crankcase explosion in I.C. engines usually occurs as

A) First a mild explosion followed by a bi explosion B) First a big explosion followed by a mil explosion C) Both mild and big explosions occurs simultaneously D) Never occurs

Discuss

Answer & Solution

Answer: Option A

Solution:

Crankcase explosion in I.C. engines usually occurs as First a mild explosion followed by a bi explosion. Crankcase explosions are also the result of high operating temperatures of the engine. The main cause of crankcase explosions are the development of hot spots at various places in the crankcase. Due to the reciprocating motion of the piston the lubricating oil in the crankcase is splashed in the air.

37

The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will

A) Increase B) Decrease C) Be independent D) May increase or decrease depending on other factors

Discuss

Answer & Solution

Answer: Option B

Solution:

The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will Decrease. The compression ratio is the ratio of the volume of the cylinder and the combustion chamber when the piston is at the bottom, and the volume of the combustion chamber when the piston is at the top. Automotive engineers can improve fuel efficiency and fuel economy by designing engines with high compression ratios.

38

Which is more viscous lube oil?

A) SEA 30 B) SAE 50 C) SAE 70 D) SAE 80

Discuss

Answer & Solution

Answer: Option D

Solution:

SAE 80 is more viscous lube oil

39

The reflectivity depends upon

A) Geometry of the reflector B) Energy of neutrons C) Properties of the reflector D) All of these

Discuss

Answer & Solution

Answer: Option D

Solution:

The reflectivity depends upon - Geometry of the reflector -Energy of neutrons - Properties of the reflector

40

Which of the following fuel has little tendency towards detonation?

A) Benzene B) Iso-octane C) Normal heptane D) Alcohol

Discuss

Answer & Solution

Answer: Option B

Solution:

Iso-octane has little tendency towards detonation. gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90. Because some fuels are more knock-resistant than iso-octane, the definition has been extended to allow for octane numbers higher than 100.

Internal Combustion Engines (I.C. Engines) MCQ Questions &amp; Answers | Mechanical Engineering

Internal Combustion Engines (I.C. Engines) MCQ Questions & Answers | Mechanical Engineering