Which type of valve features a round core?

A rotary valve is designed with a round core that rotates to control the flow of fluid through a system. This unique design allows the valve to effectively regulate flow direction and volume with smooth operation and minimal pressure drop. The round core can be rotated to open or close the flow path without obstructing the flow, which is essential in applications requiring precise control.

In contrast, other valves have different configurations suited for specific tasks. For instance, a gate valve features a wedge-shaped gate that moves perpendicular to the flow direction and is primarily used to start or stop fluid flow rather than regulate it. A ball valve utilizes a spherical ball as the core that rotates within the valve body but does not pivot as a rotary valve does, rather it seals or allows flow based on the ball's position. A check valve allows fluid to flow in one direction only, typically using a swing mechanism or a disc, and does not involve rotational movement of a core to control flow. Thus, the distinctive rotating mechanism and round core of a rotary valve set it apart and make it the correct response for this question.