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Current Affairs January 2024

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4

Detonation is harmful due to

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

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

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

D. None of the above

Correct Answer :

D. None of the above


Related Questions

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4

The knocking tendency in spark ignition engines may be decreased by

A. Controlling the air-fuel mixture

B. Controlling the ignition timing

C. Controlling the exhaust temperature

D. Reducing the compression ratio

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4

A petrol engine, during suction stroke draws

A. Air only

B. Petrol only

C. A mixture of petrol and air

D. None of these

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4

The injection pressure in a diesel engine is about

A. 10 bar

B. 100 bar

C. 150 bar

D. 500 bar

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4

Which of the following statement is wrong?

A. A four stroke cycle engine develops twice the power as that of a two stroke cycle engine

B. For the same power developed, a four stroke cycle engine is lighter, less bulky and occupies less floor area

C. The petrol engines are costly than diesel engines

D. All of the above

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4

The higher combustion chamber wall temperature in compression ignition engines will _________ knocking tendency.

A. Increase

B. Reduce

C. Not effect

D. None of these

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4

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

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4

A diesel engine has

A. 1 valve

B. 2 valves

C. 3 valves

D. 4 valves

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4

Scavenging is usually done to increase

A. Thermal efficiency

B. Speed

C. Power output

D. Fuel consumption

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4

The _________ engines can work on very lean mixture of fuel.

A. Spark ignition

B. Compression ignition

C. Both (A) and (B)

D. None of these

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4

In the crankcase method of scavenging, the air pressure is produced by

A. Supercharger

B. Centrifugal pump

C. Natural aspirator

D. Movement of engine piston

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4

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

A. Supercharging

B. Carburetion

C. Turbulence

D. Delay period

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4

The cetane (C16H34) which is a straight chain paraffin, is assigned a cetane number of

A. 0

B. 50

C. 100

D. 120

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4

Which of the following statements is correct?

A. All the irreversible engines have same efficiency

B. All the reversible engines have same efficiency

C. Both Rankine and Carnot cycles have same efficiency between same temperature limits

D. All reversible engines working between same temperature limits have same efficiency

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4

When crude oil is heated, then which of the following hydrocarbon is given off first?

A. Kerosene

B. Gasoline

C. Paraffin

D. Natural gas

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4

A stoichiometric air-fuel ratio is

A. Chemically correct mixture

B. Lean mixture

C. Rich mixture for idling

D. Rich mixture for over loads

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4

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

A. Diesel

B. Kerosene

C. Fuel oil

D. Gasoline

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4

Supercharging is the process of

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

B. Providing forced cooling air

C. Injecting excess fuel for raising more loads

D. Supplying compressed air to remove combustion products fully

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4

The normal heptane (C7H16) is given a rating of ________ octane number.

A. 0

B. 50

C. 100

D. 120

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4

The two reference fuels used for cetane rating are

A. Cetane and iso-octane

B. Cetane and alpha-methyl naphthalene

C. Cetane and normal heptane

D. Cetane and tetra ethyl lead

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4

The knocking in spark ignition engines can be reduced by

A. Retarding the spark

B. Increasing the engine speed

C. Both (A) and (B)

D. None of these

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4

Solid fuel fabricated into various small shapes, which are assembled to form fuel elements, is in the form of

A. Plates

B. Pallets

C. Pins

D. All of these

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4

In a coil ignition system of petrol engines, a condenser is connected across the contact breaker in order to

A. Prevent sparking across the gap between the points

B. Cause more rapid break of the primary current, giving a higher voltage in the secondary circuit

C. Both (A) and (B)

D. None of the above

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4

The theoretically correct mixture of air and petrol is

A. 10 : 1

B. 15 : 1

C. 20 : 1

D. 25 : 1

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4

High speed compression engines operate on

A. Otto cycle

B. Diesel cycle

C. Dual combustion cycle

D. All of these

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4

A diesel engine is _________ as compared to petrol engine, both running at rated load.

A. Equally efficient

B. Less efficient

C. More efficient

D. None of these

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4

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

A. Air alone

B. Air and fuel

C. Air and lub oil

D. Fuel alone

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4

The air-fuel ratio of the petrol engine is controlled by

A. Fuel pump

B. Governor

C. Injector

D. Carburettor

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4

A fuel of an octane number rating of 75 matches in knocking intensity as a mixture of

A. 75% iso-octane and 25% normal heptane

B. 75% normal heptane and 25% iso-octane

C. 75% petrol and 25% diesel

D. 75% diesel and 25% petrol

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4

The knock in diesel engine occurs due to

A. Instantaneous and rapid burning of the first part of the charge

B. Instantaneous auto ignition of last part of charge

C. Delayed burning of the first part of the charge

D. Reduction of delay period

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4

Which one of the following event would reduce volumetric efficiency of a vertical compression ignition engine?

A. Inlet valve closing after bottom dead centre

B. Inlet valve closing before bottom dead centre

C. Inlet valve opening before top dead centre

D. Exhaust valve closing after top dead centre