Axial fan is a common ventilation equipment, widely used in industry, agriculture, construction and other fields. The following is a detailed analysis of its working principle and structure:
Working Principle
The working principle of axial fan is based on the axial thrust generated when the impeller rotates. When the motor drives the impeller to rotate, the blades on the impeller push the air so that the air flows in the direction of the fan's axis. Specifically, as the blades rotate, their inclined surfaces interact with the air, exerting an oblique force on the air, which can be broken down into an axial thrust and a force that rotates the air. The axial thrust causes the air to flow along the axis of the fan, forming an axial airflow, thus realising functions such as ventilation or heat dissipation; while the force that rotates the air will cause energy loss to a certain extent, but usually through the reasonable design of blade shapes and angles, this loss can be controlled within a small range.
Structure Analysis
Impeller: It is the core component of the axial fan and consists of several blades and hub. The blades are usually made of aerospace aluminium alloy or high-strength engineering plastics, which have good strength and corrosion resistance. The shape and angle of the blades have a key impact on the performance of the fan, and common blade shapes include backward tilting, forward tilting and radial. Backward tilted blades have higher efficiency and lower noise, and are suitable for applications with higher noise requirements; forward tilted blades can produce a larger air volume under the same size and speed, but have relatively lower efficiency and higher noise; radial blades are in between. The hub is used to connect the blades and the motor shaft, usually made of cast iron or cast aluminium, with high strength and rigidity.
Motor: Provides power for the axial fan, usually a three-phase asynchronous motor or DC motor. Three-phase asynchronous motor has the advantages of simple structure, reliable operation, easy maintenance, etc., widely used in industrial fields; DC motors have the advantages of good speed performance, high efficiency, etc., commonly used in occasions with high requirements for speed control, such as some electronic equipment cooling fan. The power size of the motor is selected according to the size of the fan, wind volume and wind pressure requirements, the greater the power, the greater the speed and wind volume of the fan.
Shell: mainly play a protective and supportive role, but also play a certain role in guiding the airflow. The shell is usually made of thin steel plate or aluminium alloy, with good strength and sealing. The shape and structural design of the casing will affect the airflow distribution and noise level of the fan. Some high-performance Axial fans will be designed with a deflector or noise reduction device on the casing to optimise airflow and reduce noise.
Protective mesh: Installed at the air inlet and outlet of the fan, it is used to prevent debris from entering the fan and damaging the impeller or motor, and also protects the safety of personnel by preventing fingers and other parts of the body from coming into contact with the rotating impeller. The protective mesh is usually made of wire mesh or plastic mesh, and its mesh size is determined according to the environment and requirements of the fan.
In addition, some axial fans may be equipped with auxiliary components such as speed regulators, vibration damping devices, and control systems to meet different usage requirements and to improve the performance and reliability of the fan.
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