What type of impeller is the most efficient for developing the highest pressure?

The most efficient type of impeller for developing the highest pressure is the closed impeller. Closed impellers consist of a shroud on both the inlet and outlet sides, providing a confined space for the fluid to accelerate as it passes through the impeller. This design minimizes leakage and turbulence within the impeller, allowing for more effective energy transfer from the impeller to the fluid.

The closed configuration enables the fluid to be directed efficiently, leading to higher velocity and increased pressure at the outlet. This is essential in applications requiring significant pressure gains, such as in water and fuel systems maintenance. The design of closed impellers also tends to allow for better performance across a range of flow conditions, making them versatile and reliable for high-pressure applications.

In contrast, open impellers lack the shroud on the outlet side, which can lead to less efficient operation due to higher turbulence and potential flow recirculation. Semi-open impellers have a partial shroud, offering some advantages over open designs but still do not match the pressure-generating capability of a fully closed impeller. The combination impeller, which can feature both open and closed elements, may offer versatility, but it typically does not reach the same efficiency in pressure generation as a closed impeller.