What type of pump allows fluid output to vary with system demand?

A variable displacement pump is designed to adjust its output flow based on the system's demand, making it ideal for applications where fluid needs fluctuate. This type of pump utilizes mechanisms, such as swashplates or pistons that change position, to vary the size of the pumping chamber, enabling it to increase or decrease flow as required. This feature makes variable displacement pumps particularly useful in hydraulic systems, where efficiency and responsiveness to changing loads are crucial for optimal performance.

In contrast, constant displacement pumps maintain a fixed output regardless of system demand. Therefore, they do not adapt to changing conditions, which can lead to inefficiencies or a need for additional controlling mechanisms to manage flow.

Gear type pumps are typically fixed displacement pumps and offer a consistent flow rate, making them suitable for applications requiring a steady supply of fluid rather than varying demand.

Piston type pumps can also be designed for either constant or variable displacement, but without the additional mechanisms typically found in variable displacement designs, they may not inherently adjust their output in response to system demands. Thus, while piston pumps can function in both ways, not all are configured for variable displacement, emphasizing why the correct choice is specifically the variable displacement pump.