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4

The fuel valve in a four stroke cycle diesel engine

A. Opens at 15° after top dead centre and closes at 20° before bottom dead centre

B. Opens at 15° before top dead centre and closes at 20° after top dead centre

C. Opens at top dead centre and closes at bottom dead centre

D. May open and close anywhere

Correct Answer :

B. Opens at 15° before top dead centre and closes at 20° after top dead centre


Related Questions

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4

The pressure and temperature at the end of compression stroke in a petrol engine are of the order of

A. 4-6 kg/cm² and 200-250°C

B. 6-12 kg/cm² and 250-350°C

C. 12-20 kg/cm² and 350-450°C

D. 20-30 kg/cm² and 450-500°C

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4

The correct sequence of the decreasing order of brake thermal efficiency of the three given basic types of engines is

A. Four stroke C.I. engine, four stroke S.I. engine, two stroke S.I. engine

B. Four stroke S.I. engine, four stroke C.I. engine, two stroke S.I. engine

C. Four stroke C.I. engine, two stroke S.I. engine, four stroke S.I. engine

D. Two stroke S.I. engine, four stroke S.I. engine, four stroke C.I. engine

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4

The fuel in diesel engine is normally injected at pressure of

A. 5-10 kg/cm²

B. 20-25 kg/cm²

C. 60-80 kg/cm²

D. 90-130 kg/cm²

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4

The combustion in compression ignition engines is

A. Homogeneous

B. Heterogeneous

C. Both (A) and (B)

D. None of these

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4

In a typical medium speed 4-stroke cycle diesel engines

A. Exhaust valve opens at 35° before bottom dead centre and closes at 20° after top dead centre

B. Exhaust valve opens at bottom dead centre and closes at top dead centre

C. Exhaust valve opens just after bottom dead centre and closes just before top dead centre

D. May open and close anywhere

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4

Which of the following statement is correct regarding normal cetane?

A. It is a standard fuel used for knock rating of diesel engines

B. Its chemical name is normal hexadecane

C. It has long carbon chain structure

D. All of the above

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4

Alpha-methyl-naphthalene (C₁₁ H₁₀) has a cetane number of

A. 0

B. 50

C. 100

D. 120

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4

If the compression ratio in I.C. engine increases, then its thermal efficiency will

A. Decrease

B. Increase

C. Remain same

D. None of these

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4

The octane number of petrol, generally available, is

A. 20 to 40

B. 40 to 60

C. 60 to 80

D. 80 to 100

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4

Scavenging air in diesel engine means

A. Air used for combustion sent under pressure

B. Forced air for cooling cylinder

C. Burnt air containing products of combustion

D. Air used for forcing burnt gases out of engine's cylinder during the exhaust period

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4

Engine pistons are usually made of aluminium alloy because it

A. Is lighter

B. Wear is less

C. Absorbs shocks

D. Is stronger

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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

In diesel engine the diesel fuel injected into cylinder would burn instantly at about compressed air temperature of

A. 250°C

B. 500°C

C. 1000°C

D. 2000°C

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4

The increase of cooling water temperature in petrol engine will __________ the knocking tendency.

A. Not effect

B. Decrease

C. Increase

D. None of these

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4

A spark plug gap is kept from

A. 0.3 to 0.7 mm

B. 0.2 to 0.8 mm

C. 0.4 to 0.9 mm

D. 0.6 to 1.0 mm

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4

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

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4

Which of the following does not relate to a compression ignition engine?

A. Fuel pump

B. Fuel injector

C. Governor

D. Carburettor

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4

Volatility of diesel fuel oil is

A. 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

B. Temperature at which it solidifies or congeals

C. It catches fire without external aid

D. Indicated by 90% distillation temperature, i.e., when 90% of sample oil has distilled off

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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

The reference fuels for knock rating of spark ignition engines would include

A. Iso-octane and alpha-methyl naphthalene

B. Normal octane and aniline

C. Isooctane and normal hexane

D. Normal heptane and isooctane

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4

The function of a distributor in a coil ignition system of I.C. engines is

A. To distribute spark

B. To distribute power

C. To distribute current

D. To time the spark

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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

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

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

In case of gas turbines, the gaseous fuel consumption guarantees are based on

A. High heat value

B. Low heat value

C. Net calorific value

D. Calorific value

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4

The calorific value of gaseous fuels is expressed in terms of

A. kcal

B. kcal/kg

C. kcal/m²

D. kcal/m3

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4

In a diesel engine, the fuel is ignited by

A. Spark

B. Injected fuel

C. Heat resulting from compressing air that is supplied for combustion

D. Ignition

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4

In a petrol engine, the mixture has the lowest pressure at the

A. Beginning of suction stroke

B. End of suction stroke

C. End of compression stroke

D. None of these

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4

A fuel of cetane number 40 has the same ignition quality as a mixture of

A. 40% cetane and 60% alpha methyl naphthalene

B. 40% alpha methyl naphthalene and 60% cetane

C. 40% petrol and 60% diesel

D. 40% diesel and 60% petrol

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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