Question 32 MODE02 - Assistant MODU Engineer

The Correct Answer is A **Explanation for Option A (Constant pressure):** The **constant pressure** turbocharging method uses a large exhaust manifold and often a common collector that dampens the pressure pulsations arriving from the individual cylinders. By maintaining a large, relatively steady volume of exhaust gas before the turbine, the system smooths out the pressure and velocity fluctuations (pulses) inherent in the engine's exhaust cycle (where pressure peaks occur when exhaust valves open). The goal of this system is to deliver the exhaust gases to the turbine inlet at a **fairly uniform velocity and pressure**, maximizing the steady-state thermal energy transfer to the turbine wheel. This method is typically favored in large, slower-speed diesel engines (like those found in marine or power generation applications). **Why the other options are incorrect:** * **B) Pulse pressure:** This method relies specifically on exploiting the high-kinetic energy and high-pressure peaks (pulses) that occur immediately after the exhaust valve opens. The manifold runners are kept short and of small volume to preserve these distinct pulses and direct them rapidly to the turbine. Therefore, this method delivers the exhaust gases to the turbine with highly non-uniform (pulsating) pressure and velocity, which is the opposite of what the question describes. * **C) Constant velocity:** While engineers strive for efficient velocity utilization, "Constant velocity" is not a standard, recognized turbocharging method or system classification in the same way that Constant Pressure and Pulse Pressure are. The design principle that achieves uniform velocity and pressure is referred to as the constant pressure system. * **D) Axial flow:** Axial flow describes the direction in which the gas moves relative to the turbine wheel (parallel to the axis of rotation). This is a description of the **turbine type**, not a description of the manifold design or the method used to manage the pressure and velocity characteristics of the exhaust gas before it reaches the turbine.