impellers

An impeller is a rotating disc or hub with blades used to impart energy to a fluid. It is a core component of many turbomachines, including pumps, compressors, and turbines. In pumps, the impeller adds kinetic energy to the fluid, creating flow and pressure. In turbines, it extracts energy from a moving fluid.

Impellers are classified by flow type: radial (centrifugal) impellers push fluid outward from the center; axial impellers move fluid parallel to the axis; mixed-flow lie between. Blade geometry varies: backward-curved blades common in pumps for efficiency; forward-curved blades used for higher flow at lower head but less efficient; straight vanes sometimes used for simple applications.

Key design features include the hub, shroud, and blades set on a root and disposed around an eye. Performance is described by head, flow rate, efficiency, and power. The impeller works with the casing or volute to convert kinetic energy into pressure. The geometry of the blades and their angle influence the flow path and losses, linking to overall efficiency and noise.

Applications span water supply pumps, drainage, HVAC fans and blowers, turbomachinery, automotive turbochargers, jet engines, and hydroelectric turbines. Impellers are used wherever energy is transferred between a fluid and a rotating element.

Materials and manufacturing vary with requirements. Metals such as steel, stainless steel, and aluminum are common; composites and ceramics are used for specialized high-temperature or high-wear conditions. Manufacturing methods include casting, forging, machining, welding, and increasingly additive manufacturing.

Operation and maintenance considerations include cavitation prevention, surge control, erosion and corrosion management, and balancing to reduce vibration. Proper alignment, clearances with the casing, and periodic inspection or replacement of worn parts are important for reliable performance.