Question 4 UFIV02 - Assistant Engineer - UFIV

The Correct Answer is A **Explanation for Option A (Correct):** Option A states: "This is a pushrod operated overhead valve engine, with wet cylinder liners and conventional connecting rods." This is correct based on the typical characteristics of the illustrated engine type (Illustration MO-0005 typically depicts a common, medium-speed, four-stroke propulsion diesel engine, such as a CAT or similar model, often used in fishing trawlers). 1. **Pushrod Operated Overhead Valve Engine (OHV):** The illustration usually shows the camshaft located in the engine block, operating tappets, pushrods, and rocker arms to actuate the valves in the cylinder head. This configuration defines a pushrod operated OHV engine. 2. **Wet Cylinder Liners:** In most medium-speed four-stroke engines of this size and application (especially those built for rugged marine use), the cylinder liners are designed as "wet liners." A wet liner is directly exposed to the jacket cooling water, meaning the cooling water contacts the outer surface of the liner itself. 3. **Conventional Connecting Rods:** These engines typically utilize standard, one-piece connecting rods that connect the piston pin to the crankpin (sometimes called "conventional" or "standard" connecting rods, in contrast to specialized types like articulated or marine-type rods used in very large slow-speed engines). **Explanation for Incorrect Options:** **B) This is a pushrod operated overhead valve engine, with jacketed cylinder liners and articulated connecting rods.** * **Jacketed Liners (Incorrect):** While the engine uses a cooling jacket, the liner itself is a *wet* liner, meaning it forms the inner wall of the cooling jacket, rather than being a dry liner surrounded by a separate, permanent cooling jacket (which is implied by "jacketed liners" in some contexts, or refers specifically to dry liners). * **Articulated Connecting Rods (Incorrect):** Articulated connecting rods are used almost exclusively in V-type engines (or master/slave rod configurations) where two pistons share a single crank pin. Trawlers often use inline engines, and the illustration typically shows an inline configuration with conventional rods. **C) This is an overhead cam engine, with wet cylinder liners and conventional connecting rods.** * **Overhead Cam (Incorrect):** An overhead cam (OHC) engine places the camshaft directly in or above the cylinder head. The illustrated engine type (pushrod OHV) has its camshaft located in the engine block, utilizing pushrods to operate the valves, making it distinct from an OHC design. **D) This is an overhead cam engine, with jacketed cylinder liners and marine-type connecting rods.** * **Overhead Cam (Incorrect):** As stated above, this engine uses pushrods. * **Marine-Type Connecting Rods (Incorrect):** "Marine-type" connecting rods often refers to the specialized, segmented, large-diameter rods used in large, slow-speed, two-stroke crosshead engines, which feature a separate crosshead bearing and piston rod. This medium-speed trunk piston engine uses conventional connecting rods.