Question 3 QMED01 - Junior Engineer

The Correct Answer is A **Explanation of Option A (Correct):** The primary function of the intake system (or air induction system) in any internal combustion engine, including a diesel engine, is to draw in atmospheric air, filter it (ensuring it is clean), and deliver it to the engine cylinders. Diesel combustion relies solely on compressed air being heated to a high temperature, into which fuel is then injected. Therefore, ensuring an adequate supply of clean air is essential for **combustion**. Furthermore, in large diesel engines (especially two-stroke engines) or turbocharged four-stroke engines, the air provided by the intake system also plays a crucial role in **scavenging**—the process of forcing residual exhaust gases out of the cylinder before the next compression stroke begins. **Explanation of Incorrect Options:** * **B) The intake system's function is to ensure an adequate supply of clean lubricating oil to support engine lubrication.** This is the function of the **lubrication system** (oil pump, oil cooler, filters, etc.), not the intake (air induction) system. * **C) The intake system's function is to ensure an adequate supply of clean sea water to support engine cooling.** This is the function of the **cooling water system** (pumps, heat exchangers, filters/strainers), not the intake system. * **D) The intake system's function is to ensure an adequate supply of clean air to support engine crankcase ventilation.** While fresh air often plays a role in crankcase ventilation (PCV systems), the primary and essential function of the main engine intake system is supporting **combustion and scavenging**, not merely ventilating the crankcase. Crankcase ventilation is a secondary requirement handled by a specific, separate subsystem.