Exam Question

### (a) The Mechanism of Combustion and Factors for Good Combustion
#### Mechanism of Combustion
Combustion is a rapid exothermic chemical reaction involving a fuel and an oxidant, usually atmospheric oxygen, to produce heat. In a boiler furnace, the chemical energy stored in the fuel oil is converted into thermal energy, which is then transferred to the water/steam in the boiler tubes. The process for heavy fuel oil involves several stages:
1. **Atomization**: The high-pressure, pre-heated viscous fuel is forced through a specially designed burner nozzle (atomizer), which breaks the liquid fuel into a fine mist of microscopic droplets. This vastly increases the surface-area-to-volume ratio, facilitating rapid evaporation and mixing with air.