Impeller

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Impeller 2

Pump Impellers-1

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Impellerrad

Mixing - flusso assiale e radiale

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Washing machine agitator

Impeller

An impeller is a rotor used to increase (or decrease in case of turbines) the pressure and flow of a fluid. It is the rotating component of a centrifugal pump, blower, or other fluid dynamics machinery that moves fluid through a system. Impellers are typically found in applications ranging from water pumping to aeration, and from heating, ventilation, and air conditioning systems (HVAC) to gas turbines.

Design and Function

The design of an impeller affects its efficiency and performance in fluid movement. Impellers can be designed with various numbers of blades, shapes, and sizes, depending on the application. The two main types of impeller based on their flow direction are:

• Axial-flow impeller: Moves the fluid parallel to the impeller's rotation axis.
• Radial-flow impeller: Moves the fluid perpendicular to the impeller's rotation axis.

Additionally, impellers can be categorized by their specific design:

• Open impeller: Has blades attached to a hub without a sidewall, making it easier to clean and maintain. Suitable for applications involving solid particles in the fluid.
• Semi-open impeller: Has blades with a partial sidewall on one side, offering a compromise between efficiency and ease of maintenance.
• Closed impeller: Has blades enclosed between two sidewalls, making it the most efficient design for clear liquids.

Materials

Impellers are made from a variety of materials, including plastics, metals, and rubber, depending on the fluid's nature, the application's temperature, and the pressure requirements. Common materials include stainless steel for corrosive or high-temperature applications, bronze for water pumping, and plastics for chemical processing.

Applications

Impellers are used in a wide range of applications, including:

• Water pumps for irrigation, water supply, and flood control.
• Chemical processing equipment for mixing and pumping chemicals.
• HVAC systems for circulating air and refrigerants.
• Power generation in gas turbines and steam turbines.
• Marine propulsion in boats and ships through water jets and propellers.

Maintenance

Regular maintenance of impellers is crucial for the efficient operation of the machinery they are part of. Maintenance tasks may include inspection for wear and damage, cleaning to remove any debris or buildup, and replacement if the impeller is beyond repair. Proper maintenance ensures the longevity of the impeller and the machinery it operates within.

Challenges

Designing impellers involves overcoming challenges such as cavitation, erosion, and vibration. Cavitation occurs when the local fluid pressure falls below the vapor pressure, leading to the formation of vapor bubbles, which can cause damage when they collapse. Erosion can occur from particles in the fluid hitting the impeller surface. Vibration can be caused by imbalances in the impeller or misalignment with the pump shaft, leading to wear and potential failure.