IC Engines and Nuclear Power Plants for practice

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IC Engines and Nuclear Power Plants Paper Set 3

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The basic requirement of a good combustion chamber is

1 Minimum turbulence

2 Low compression ratio

3 High thermal efficiency and power output

4 Low volumetric efficiency

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

1 75% iso-octane and 25% normal heptane

2 75% normal heptane and 25% iso-octane

3 75% petrol and 25% diesel

4 75% diesel and 25% petrol

The air-fuel ratio in petrol engines is controlled by

1 Controlling valve opening/closing

2 Governing

3 Injection

4 Carburetion

In a typical medium speed 4-stroke cycle diesel engines

1 Exhaust valve opens at 35° before bottom dead center and closes at 20° after top dead center

2 Exhaust valve opens at bottom dead center and closes at top dead center

3 Exhaust valve opens just after bottom dead center and closes just before top dead cente

4 May open and close anywhere

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

1 feeding more fuel

2 increasing flywheel size

3 heating incoming air

4 scavenging

5 supercharging

If one cylinder of a diesel engine receives more fuel than the others, then for that cylinder the

1 exhaust will be smoky

2 piston rings would stick into piston grooves

3 exhaust temperature will be high

4 engine starts overheating

5 scavenging occurs

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

1 increase

2 decrease

3 remain same

4 unpredictable

5 depend on other factors

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

1 same

2 less

3 more

4 more or less depending on power rating

5 unpredictable

Compression ratio of LC. engines is

1 the ratio of volumes of air in cylinder before compression stroke and after compression stroke

2 volume displaced by piston per stroke and clearance volume in cylinder

3 ratio of pressure after compression and before compression

4 Swept volume/cylinder volume

5 cylinder volume/swept volume.

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 meters, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Dia. of brake drum in meters, and d = Dia. of rope in meters)

1 B.P = (Wl × 2πN)/60 watts

2 B.P = [(W - S) πDN]/60 watts

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

4 All of these

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

1 Supercharger

2 Centrifugal pump

3 Natural aspirator

4 Movement of engine piston

Flash point of fuel oil is

1 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

2 Temperature at which it solidifies or congeals

3 Temperature at which it catches fire without external aid

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

The probability of knocking in diesel engines is increased by

1 High self ignition temperature

2 Low volatility

3 Higher viscosity

4 All of these

The ignition quality of petrol is expressed by

1 Cetane number

2 Octane number

3 Calorific value

4 All of these

In a four stroke cycle diesel engine, the exhaust valve

1 Opens at 30° before bottom dead centre and closes at 10° after top dead centre

2 Opens at 30° after bottom dead centre and closes at 10° before top dead centre

3 Opens at bottom dead centre and closes at top dead centre

4 May open and close anywhere

Scavenging air in diesel engine means

1 air used for combustion sent under pres-sure

2 forced air for cooling cylinder

3 burnt air containing products of combustion

4 air used for forcing burnt gases out of engine's cylinder during the exhaust period

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

1 4 - 6 kg/cm2 and 200 - 250°

2 6 - 12 kg/cm2 and 250 - 350°C

3 12 - 20 kg/cm2 and 350 - 450°C

4 20 - 30 kg/cm2 and 450 - 500°C

5 30 - 40 kg/cm2 and 500 - 700°C