What type of pump is categorized as a positive displacement pump?

A positive displacement pump operates by trapping a fixed amount of fluid and forcing it into the discharge pipe. This type of pump is characterized by its ability to maintain a constant flow rate, even against varying pressures. The rotary pump, which is recognized as a type of positive displacement pump, moves fluid by trapping it between the rotating elements and the chamber walls, thereby creating suction and pushing the fluid out.

In rotary pumps, components such as gears or lobes rotate within a casing to create the necessary volume displacement. This mechanism allows for smooth and continuous flow, making rotary pumps useful in applications where consistent pressure and flow are required.

In contrast, centrifugal and turbine pumps rely on rotating impellers to impart kinetic energy to the fluid, causing it to flow. These pumps depend on the speed of rotation and the fluid's characteristics, meaning their flow rates can vary with changes in system pressure. Piston pumps also are a type of positive displacement pump but are specifically designed to use a piston mechanism to move fluid, which is slightly different from the rotary action of the chosen answer.

Thus, the classification of the rotary pump as a positive displacement pump highlights its unique operational mechanism that ensures a steady flow rate regardless of pressure conditions.