Question 11 QMED01 - Junior Engineer

The Correct Answer is C ### Why Option C is Correct: Fuel injection systems are fundamentally designed to perform three primary tasks: 1. **Meter fuel:** Precisely control the amount of fuel delivered (ensuring the correct air/fuel ratio). 2. **Atomize fuel:** Break the liquid fuel into a fine mist (small droplets) for rapid vaporization and mixing. 3. **Inject fuel at the proper time (Timing):** Deliver the metered and atomized fuel into the intake manifold (Port Injection) or directly into the cylinder (Direct Injection) exactly when required by the engine cycle. For spark-ignited engines, this timing is crucial for combustion efficiency and emission control, usually occurring when the intake valve is open. For diesel engines, precise timing determines the start of combustion. Therefore, accurate **timing** is the essential third primary function alongside metering and atomization. ### Why Other Options Are Incorrect: **A) create turbulence in the combustion chamber:** While turbulence (or swirl/tumble) is desirable for good mixing and faster combustion, it is primarily a function of the **intake port and piston crown design**, not the fuel injection system itself. The injector's spray pattern may influence local turbulence, but its primary function is not to create overall chamber turbulence. **B) aid in completing cylinder scavenging:** Scavenging (the process of pushing exhaust gases out and drawing fresh charge in) is a function of the **valve timing, valve overlap, and exhaust system design**, particularly in two-stroke engines. The fuel injection system plays no direct role in completing this process. **D) minimize fuel penetration into the cylinder:** This is not a universal goal. While excessive fuel penetration (impingement on piston or cylinder walls) is generally undesirable in gasoline direct injection (GDI) engines, the injector's design is focused on achieving the *correct* spray pattern and penetration depth to ensure optimal mixing and vaporization, not simply minimizing penetration. Furthermore, minimizing penetration is a technical detail related to atomization and spray targeting, not one of the three foundational primary purposes of the system. The fundamental primary function related to delivery is timing.