Technical Standards and Safety Authority (TSSA) G3 Practice Exam

What happens to combustion efficiency if there's an excess of air during burning?

1. It improves significantly

2. It decreases

3. It remains the same

4. It is unaffected

The correct answer is: It decreases

When there is an excess of air during the combustion process, the combustion efficiency decreases. This is primarily because the additional air dilutes the fuel-to-air mixture, resulting in incomplete combustion. The presence of excess air can lead to a scenario where there is not enough fuel to completely react with the oxygen present, leading to the formation of combustion byproducts, such as unburned hydrocarbons and carbon monoxide. Moreover, in a situation with excess air, some of the heat produced during combustion is used to heat the additional air rather than being fully utilized for the intended heating purpose. This means that while the combustion may produce more energy, a portion of that energy is not effectively used, thus reducing overall efficiency. For effective combustion efficiency, an optimal balance of fuel and air is crucial to ensure that combustion occurs at the ideal stoichiometric ratio. Deviations from this ratio either way can lead to inefficiencies, but excess air specifically tends to lower the combustion efficiency.