Characteristics of Combustion work sheet 1

Which two factors primarily affect the heat released from a burner when using a particular gas, according to the Wobbe number?

• The calorific value and the specific gravity

• The injector size and the gas pressure

• The flame speed and the ventilation rate

• The oxygen content and the burner shape

Which family of gases covers natural gases?

• Family 1

• Family 2

• Family 3

• Family 4

What is the approximate flame speed of natural gas?

• 0.16 m/sec

• 0.36 m/sec

• 1.00 m/sec

• 0.50 m/sec

If the oxygen required for combustion is reduced due to contamination with CO₂, what is the likely result?

• Complete combustion will occur

• Incomplete combustion will take place

• The flame speed will increase

• The calorific value will rise

A person exposed to carbon monoxide shows symptoms such as flushed skin, headache, breathlessness, and palpitations. According to the table, what is the likely percentage saturation of haemoglobin with carbon monoxide?

• 0 to 10%

• 10 to 20%

• 30 to 40%

• 70% and above

Which type of flame is most commonly used in gas burners and is partially aerated?

• Pre-aerated flame

• Diffusion flame

• Blue flame

• Candle flame

What is the main function of the fan in a forced draught full pre-mix burner?

• To cool the burner

• To move air through a venturi

• To ignite the gas

• To filter the gas

Which of the following is a visual sign of incomplete combustion in a gas appliance?

• Blue flames inside the appliance

• Staining around the appliance

• Clean glass surfaces

• No odor from the appliance

Explain why yellow flames inside a gas appliance indicate incomplete combustion. Use evidence from the visual signs described.

• Yellow flames mean the appliance is overheating.

• Yellow flames indicate the flame is not burning completely, which is a sign of incomplete combustion.

• Yellow flames show the appliance is using too much gas.

• Yellow flames are a sign of proper combustion.

A technician observes both staining around a gas appliance and yellow flames inside it. What should be the technician’s next step, based on the causes of incomplete combustion?

• Ignore the signs and continue operation

• Check for insufficient air for combustion, overgassing, undergassing, flame impingement, and vibration

• Increase the gas supply without checking anything else

• Clean the appliance and restart it