Exam Question

### 1. Necessity of Heating Heavy Fuel Oil (HFO)
Heavy Fuel Oil (HFO), as the name suggests, is a residual fuel with high density, viscosity, and a complex molecular structure. Heating HFO before injection into an engine cylinder is critical for the following fundamental reasons:
* **Viscosity Reduction for Atomization:** The primary objective is to reduce the fuel's viscosity to a specific range, typically **12-14 centistokes (cSt)** at the point of injection. Viscosity is a fluid's resistance to flow. At ambient temperatures, HFO is extremely viscous, almost semi-solid, making it impossible to pump effectively, let alone inject.
* **Atomization:** For efficient and complete combustion, fuel must be injected into the cylinder as a fine mist of tiny droplets, a process called atomization. This vastly increases the surface area of the fuel exposed to the hot, compressed air, allowing for rapid evaporation and mixing.