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What is the correct answer?

4

The thermal efficiency of diesel engines is about

A. 15 %

B. 30 %

C. 50 %

D. 70 %

Correct Answer :

D. 70 %


Related Questions

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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 spark ignition engines are governed by

A. Hit and miss governing

B. Qualitative governing

C. Quantitative governing

D. Combination of (B) and (C)

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4

In a four stroke cycle engine, the sequence of operations is

A. Suction, compression, expansion and exhaust

B. Suction, expansion, compression and exhaust

C. Expansion, compression, suction and exhaust

D. Compression, expansion, suction and exhaust

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4

A diesel engine as compared to petrol engine (both running and rated load) is

A. More efficient

B. Less efficient

C. Equally efficient

D. Other factors will decide it

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4

In petrol engine, using a fixed octane rating fuel and fixed compression ratio, supercharging will _________ the knocking tendency.

A. Not effected

B. Decrease

C. Increase

D. None of these

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4

If the intake air temperature of I.C. engine increases, its efficiency will

A. Increase

B. Decrease

C. Remain same

D. None of these

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4

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

A. Equal to

B. One-half

C. Twice

D. Four-times

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4

The output of a diesel engine can be increased without increasing the engine revolution or size in following way

A. Feeding more fuel

B. Heating incoming air

C. Scavenging

D. Supercharging

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4

A petrol engine has compression ratio from

A. 6 to 10

B. 10 to 15

C. 15 to 25

D. 25 to 40

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4

Which of the following is false statement? Some of the methods used to reduce diesel smoke are as follows

A. Using additives in the fuel

B. Increasing the compression ratio

C. Adherence to proper fuel specification

D. Avoidance of overloading

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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

A mixture containing 65% of iso-octane and 35% of normal heptane will have

A. Cetane number 65

B. Octane number 65

C. Cetane number 35

D. Octane number 35

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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 thermal efficiency of petrol and gas engines is about

A. 15 %

B. 30 %

C. 50 %

D. 70 %

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4

In a petrol engine, the fuel supplied to the engine cylinder is mixed with required quantity of air and the mixture is ignited with a

A. Fuel pump

B. Fuel injector

C. Spark plug

D. None of these

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4

The working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft

A. 1/2

B. 1

C. 2

D. 4

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4

A 5 BHP engine running at full load would consume diesel of the order of

A. 0.3 kg/hr

B. 1 kg/hr

C. 3 kg/hr

D. 5 kg/hr

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4

Which of the following fuel has little tendency towards detonation?

A. Benzene

B. Iso-octane

C. Normal heptane

D. Alcohol

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4

Which of the following statement is correct regarding petrol engines?

A. A fine fuel spray mixed with air is ignited by the heat of compression which is at a high pressure

B. The fuel supplied to the engine cylinder is mixed with necessary amount of air and the mixture in ignited with the help of a spark plug

C. The fuel is first evaporated after passing through a carburettor and is mixed with air before ignition

D. All of the above

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4

Installation of supercharger on a four cycle diesel engine can result in the following percentage increase in power

A. Up to 35%

B. Up to 50%

C. Up to 75%

D. Up to 100%

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4

It the temperature of intake air in IC engines is lowered, then its efficiency will

A. Increase

B. Decrease

C. Remain same

D. Increase up to certain limit and then decrease

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4

The maximum propulsive efficiency of a turbojet engine is at a speed of

A. 1000 km/h

B. 2000 km/h

C. 2400 km/h

D. 3000 km/h

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4

The sensing element in the control system of nuclear reactors measures the _________ of the neutron flux in the reactor.

A. Temperature

B. Volume

C. Density

D. None of these

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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

The brake power (B.P.) of the engine is given by (where W = Brake load or dead load in newtons, l = Length of arm in metres, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Dia. of brake drum in metres, and d = Dia. of rope in metres)

A. B.P = (Wl × 2πN)/60 watts

B. B.P = [(W - S) πDN]/60 watts

C. B.P = [(W - S) π (D + d) N]/60 watts

D. All of these

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4

The knocking tendency in compression ignition engines for a given fuel will be

A. Enhanced by decreasing compression ratio

B. Enhanced by increasing compression ratio

C. Dependent on other factors

D. None of the above

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4

Stoichiometric ratio is

A. Chemically correct air-fuel ratio by weight

B. Chemically correct air-fuel ratio by volume

C. Actual air-fuel ratio for maximum efficiency

D. None of the above

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4

In a naturally aspirated diesel engine, the air is supplied by

A. A supercharger

B. A centrifugal blower

C. A vacuum chamber

D. An injection tube

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4

The ratio of the brake power to the indicated power is called

A. Mechanical efficiency

B. Overall efficiency

C. Indicated thermal efficiency

D. Volumetric efficiency

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4

The thermal efficiency of a standard Otto cycle for a compression ratio of 5.5 will be

A. 25 %

B. 50 %

C. 70 %

D. 100 %