Question 21 DDE04 - Designated Duty Engineer - 1000-4000 HP

The Correct Answer is D **Explanation for Option D (Viscosity):** Centistokes (cSt) is the unit used to measure kinematic viscosity. Viscosity is a fundamental property of diesel fuels (both marine gas oil and heavy fuel oil) and is defined as the fluid's resistance to flow. It is a critical parameter for proper fuel handling (pumping, filtration) and, most importantly, for effective injection and atomization in diesel engines. The viscosity of the fuel must be managed (often by heating) to ensure it meets the specifications required by the engine's fuel injection equipment. **Explanation of Incorrect Options:** * **A) Heating value:** Heating value, or calorific value, measures the energy content of the fuel and is typically expressed in units such as Joules per kilogram (J/kg) or British Thermal Units per pound (BTU/lb). * **B) Density:** Density is the mass per unit volume of the fuel and is typically expressed in kilograms per cubic meter ($\text{kg/m}^3$) or grams per milliliter (g/mL). * **C) Cetane rating:** Cetane rating is a measure of the ignition quality of the fuel (how quickly and cleanly it ignites after injection). It is expressed as a dimensionless number (e.g., Cetane Number 45).