Question 56 DDE01 - Designated Duty Engineer - Unlimited HP

The Correct Answer is D **Explanation for D (Charge air cooler):** Component labeled "3" is situated immediately downstream of the turbocharger's compressor outlet (where compressed air is hot) and immediately before the engine's intake manifold (or charge air manifold). Its physical structure, typically involving finned tubes or a heat exchanger core, indicates its function: to cool the pressurized air coming from the turbocharger. This cooling process increases the density of the air entering the cylinders, improving combustion efficiency and power output. In marine diesel applications, this component is often cooled by river water or a separate closed-loop cooling system, confirming its role as a **Charge air cooler** (CAC), sometimes referred to as an intercooler or aftercooler. **Explanation for Incorrect Options:** * **A) Exhaust manifold:** The exhaust manifold collects hot exhaust gases exiting the cylinders and directs them to the turbocharger turbine (or directly to the exhaust stack). Component 3 handles compressed *intake* air, not hot *exhaust* gas. * **B) Charge air manifold:** The charge air manifold (or intake manifold) is the piping that distributes the cooled, pressurized air (coming *out* of component 3) evenly to the individual engine cylinders' intake ports. Component 3 is the device that *conditions* the air before it enters the manifold. * **C) Wet muffler:** A muffler reduces noise. A *wet* muffler typically uses water injection to cool and silence the exhaust gases *after* they leave the engine or turbocharger. Component 3 is part of the intake air path, not the exhaust path, and its primary function is thermal exchange (cooling), not noise reduction.