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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

Correct Answer :

B. Decrease


Related Questions

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4

All heat engines utilize

A. Low heat value of oil

B. High heat value of oil

C. Net calorific value of oil

D. Calorific value of fuel

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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

A diesel engine, during suction stroke, draws

A. Air only

B. Diesel only

C. A mixture of diesel and air

D. None of these

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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

Morse test can be conducted for

A. Petrol engines

B. Diesel engines

C. Multi cylinder engines

D. All of these

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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

An hmh flame speed is obtained in diesel engine when air fuel ratio is

A. Uniform throughout the mixture

B. Chemically correct mixture

C. About 35% of rich mixture

D. About 10% of rich mixture

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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 increase in intake temperature of internal combustion engines will _________ efficiency.

A. Have no effect on

B. Increase

C. Decrease

D. None of these

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4

A two stroke cycle engine gives ________ the number of power strokes as compared to the four stroke cycle engine, at the same engine speed.

A. Half

B. Same

C. Double

D. Four times

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4

The specific fuel consumption of a petrol engine compared to diesel engine of same H.P. is

A. Same

B. More

C. Less

D. Less or more depending on operating conditions

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4

The volumetric efficiency of a well designed engine may be

A. 30 to 40 %

B. 40 to 60 %

C. 60 to 70 %

D. 75 to 90 %

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4

The compensating jet in a carburettor supplies almost constant amount of petrol at all speeds because the

A. Jet area is automatically varied depending on the suction

B. The flow from the main jet is diverted to the compensating jet with increase in speed

C. The diameter of the jet is constant and the discharge coefficient is invariant

D. Flow is produced due to the static head in the float chamber

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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

If the compression ratio of an engine working on Otto cycle is increased from 5 to 7, the percentage increase in efficiency will be

A. 2 %

B. 4 %

C. 8 %

D. 14 %

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4

For maximum power generation, the air fuel ratio for a petrol engine for vehicles, is of the order of

A. 9 : 1

B. 12 : 1

C. 15 : 1

D. 18 : 1

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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

A diesel 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

In petrol engines, the delay period is of the order of

A. 0.001 second

B. 0.002 second

C. 0.003 second

D. 0.004 second

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4

In a four stroke cycle petrol engine, the inlet valve

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

B. Opens at 20° before top dead centre and closes at 40° after bottom dead centre

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

D. May open or close anywhere

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4

Diesel fuel, compared to petrol is

A. Less difficult to ignite

B. Just about the same difficult to ignite

C. More difficult to ignite

D. Highly ignitable

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4

An engine indicator is used to determine the following

A. Speed

B. Temperature

C. Volume of cylinder

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

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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

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

A carburettor is used to supply

A. Petrol, air and lubricating oil

B. Air and diesel

C. Petrol and lubricating oil

D. Petrol and air

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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

Iso-octane (C8H18) has octane number of

A. 0

B. 50

C. 100

D. 120

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4

The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is

A. Same

B. Less

C. More

D. More or less depending on power rating

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4

The advancing of spark timing in spark ignition engines will _________ knocking tendency.

A. Increase

B. Reduce

C. Not effect

D. None of these

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4

The scavenging efficiency of a four stroke cycle diesel engine is

A. Below 50%

B. Between 50 and 85%

C. Between 85 and 95%

D. Between 95 and 100%