In a hydraulic system, what is the primary mechanism by which an impeller increases a fluid’s energy?

• A. It accelerates the fluid, converting rotational energy into head and flow energy.
• B. It increases the fluid’s viscosity.
• C. It cools the fluid.
• D. It reduces the pressure head.

Answer: (A)

The main idea is that an impeller adds energy to the fluid by transferring the motor’s rotational energy into the fluid’s hydraulic energy. As the impeller spins, it pushes and accelerates the fluid, increasing its velocity. In the surrounding diffuser or volute, part of that kinetic energy is converted into pressure energy, raising the fluid’s head and producing flow. This is how a hydraulic pump creates higher pressure and drives flow.

Increasing viscosity, cooling the fluid, or reducing the pressure head are not how an impeller works. It doesn’t purposefully raise viscosity or cool the fluid, and it does the opposite of reducing head—it raises the head (pressure) to move the fluid.