A variable displacement rotary pump uses a component that moves from side to side to change the volume of the pump. What is this component?

The correct answer identifies the reaction ring as the component that moves side to side in a variable displacement rotary pump to adjust the volume of fluid being pumped. In this type of pump, the reaction ring plays a crucial role by altering the angle of the vanes or the displacement of the fluid chamber. This adjustment impacts how much fluid is pushed through the system, allowing for variable flow rates dependent on the system's needs.

Understanding the function of the reaction ring is key, as it enables the pump to adapt to different operational conditions by changing its displacement without the need for mechanical changes to the entire system. This flexibility is vital in applications where fluid demand may vary, facilitating better efficiency and responsiveness in hydraulic systems.

In contrast, while the slipper, cylinder block, and pintle are also parts of a rotary pump, they serve different functions. The slipper is typically involved in sliding against the cylinder block but does not change the volume directly. The cylinder block serves as the housing for the pump mechanism, providing structural support. The pintle may be used in other contexts or pump types but is not specifically responsible for the variable displacement function in rotary pumps.