Working Principle of Portable Axial Flow Fans

Working Principle of Portable Axial Flow Fans

1. Explanation of Terms: Blade Profile and Blade Grid Portable axial flow fans primarily consist of multiple components including the impeller and impeller housing. Let the impeller outer diameter be d and the impeller diameter be d. Currently, the impeller of a portable axial flow fan is formed by unfolding the cross-section of a cylinder with radius r (less than d/2 and greater than D/2) onto a plane. The cross-section of blades within a blade grid is termed the blade profile. An equidistant arrangement of blades sharing the same profile constitutes a blade grid. When expanded, a blade grid aligns into a straight line, referred to as a straight blade grid. The front end of a movable axial fan is termed the leading edge, while the rear end is the trailing edge. The straight lines connecting the leading and trailing edges are called chord lines, with chord length b. The line passing through the center—specifically, the connection between the center of the circle inscribed on the upper surface of the airfoil and the center of the lower surface—is known as the center arc or centerline of the airfoil. The distance from the chord to the centerline is called the deflection, with its maximum value being the maximum deflection f. The distance between the upper and lower surfaces of the airfoil in the normal direction to the chord length is called the thickness, with its maximum value being the maximum thickness δ. The angle between the inflow velocity v and the chord is called the impact angle I. The circumferential distance between adjacent airfoils in the blade array is called the grid distance t, which should equal 2nr/z, where n is the radius of the cylindrical segment and z is the number of blades. The ratio of chord length to pitch is termed the blade pitch density, which generally increases gradually from the blade trailing edge toward the impeller center. The angle α between the chord line and the impeller circumferential direction is called the blade pitch angle. For movable axial fans, the installation angle varies along the blade height, so the installation angle refers to the value at the impeller's mean radius. The angle RIg between the tangent to the leading edge centerline of the airfoil and the direction of the circumferential velocity is called the blade inlet installation angle. The angle R2g between the tangent to the trailing edge centerline and the tangential velocity direction is called the blade outlet installation angle. The difference between the blade outlet installation angle and the blade inlet installation angle is termed the airfoil curvature angle. The angle between the overall direction of airflow entering the blade grid and the tangential velocity is called the inlet angle. The blade inlet installation angle is referred to as the blade inlet angle. Distinction from the nozzle: This is called the airflow impact angle I, where I = α. -91. The angle between the direction of airflow exiting the blade grid and the direction of the tangential velocity is the exit angle. The difference between the blade exit angle R2 and the tangential velocity is called the airflow exit lag angle S, where S = TH1 - A2. The difference between the airflow exit angle θ2 and the airflow entry angle θ1 is called the airflow turning angle: E = R2.