Presence of nitrogen in combustion air does not reduce the

Oxygen content below __________ percent in air contaminated with nitrogen does not support combustion and is unsafe for humane exposure.

A

18

B

16

C

14

D

12

Use of excess of combustion air in the combustion of fuels results in

A

Heat losses

B

Long flame

C

Condensation of water vapour from the fuel gas

D

None of these

Deficiency of combustion air during combustion of a gaseous fuel

A

Lengthens the flame

B

Causes heat loss of fuel by its partial combustion

C

Both A & B

D

Shortens the flame

Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature?

A

Calorific value of the fuel

B

Flame temperature achieved

C

Speed of combustion of fuel

D

Heat transfer rate to the stock in the furnace

The most commonly used combustion system manufactured in India for the thermal power plant boilers is the __________ combustion system.

A

Pulverised fuel

B

Travelling grate stoker firing

C

Circulating fluidised bed

D

Fluidised bed

The combustion efficiency of a gas turbine using perfect combustion chamber is of the order of

A

75%

B

85%

C

90%

D

99%

In an internal combustion engine, the process of removing the burnt gases from the combustion chamber of the engine cylinder is known as

A

Scavenging

B

Detonation

C

Supercharging

D

Polymerisation

The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is

A

More

B

Less

C

Same

D

May be more or less depending on engine capacity

Air/fuel ratio by weight for combustion of methane with theoretical quantity of air will be about

A

9:1

B

17 : 1

C

23 : 1

D

29 : 1

Air/fuel ratio on molar (volume) basis for combustion of methane with theoretical quantity of air with be

A

9.5:1

B

12.5:1

C

15.5 :1

D

18.5 : 1

Presence of nitrogen in combustion air does not reduce the

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