Question 33 AEL01 - Assistant Engineer - Limited

The Correct Answer is D. **Explanation for Option D (design of the combustion chamber):** The primary function of a fuel injector nozzle is to atomize the fuel and distribute it correctly within the compressed air inside the cylinder to ensure efficient and complete combustion. The geometry of the spray (including the number, size, and angle of the orifices) must be precisely tailored to the specific shape and size of the combustion chamber. Different engine types utilize different combustion chamber designs (e.g., direct injection diesel engines might use bowl-in-piston designs, while some gasoline engines use various dome or wedge shapes). The nozzle's spray pattern must match the airflow and volume of the chamber to avoid impingement on the piston or cylinder walls, maximize air-fuel mixing, and promote rapid flame propagation. Therefore, the **design of the combustion chamber** is the determining factor for the nozzle's orifice arrangement. **Why the other options are incorrect:** * **A) type of piston rings:** Piston rings are crucial for sealing the combustion chamber and controlling oil consumption, but their design (e.g., number or shape) has no direct influence on the required fuel spray pattern or nozzle orifice arrangement. * **B) pressure of the fuel system:** While fuel system pressure is vital for achieving proper atomization (higher pressure generally means finer droplets), the pressure level determines the necessary orifice diameter and injection force, not the **number and placement** of the holes (the spray *pattern*). The pattern is determined by the space (the combustion chamber) the fuel needs to fill. * **C) size of the pump plunger spring:** The size and stiffness of the fuel pump plunger spring influence the pressure profile and timing within a mechanical injection pump, but they are components of the fuel delivery system and do not dictate the required geometrical configuration of the spray pattern needed for optimal combustion in the cylinder.