What does the skirt of a trunk-type piston receive?

The skirt of a trunk-type piston is designed to receive the side thrust generated during the operation of the engine. This side thrust arises from the movement of the crank and connecting rod, which converts the linear motion of the piston into rotational motion. As the piston moves within the cylinder, the angle of the connecting rod changes, leading to lateral forces that are exerted against the cylinder walls. The skirt of the piston acts as a support structure that helps manage these forces, allowing the piston to maintain stability and alignment within the cylinder, which is crucial for efficient engine operation and reducing wear on the cylinder walls.

In contrast, the other options do not pertain to the primary function of the skirt. The skirt is not responsible for receiving fuel or air for combustion or cooling, as those functions are typically managed by different components of the engine system. Additionally, while lubrication is important, the skirt itself does not specifically receive excess oil; rather, oil is delivered to various engine components through different mechanisms designed for lubrication.