JPH01300099A - Axial flow fan - Google Patents

Abstract

PURPOSE:To provide an axial flow fan generating less noise by arranging semispherical thick part of 1-1.5% radius of curvature on a back face side of front edge of circumferential section of blade within D/2 or more from an outer dia. D, at the periperal length of 2 within D/2 or more from an outer dia. D, at the periperal length of 2-10% with respect to the length of bow- string-shaped member. CONSTITUTION:A blade 16 of axial flow fan 12 is constituted such that the circumferential section thereof is in an area of D/2 or more from an outer dia. D and a semispherical thick part 17 having 1-5% diameter of curvature in the circumferential length of 2-10% with respect to the length l of a bowstring-shaped member is arranged at a front edge 4. When the fan 12 is rotated, intaken air generates turburance at the rear of filter or lattice and flows in with respect to a blade 16, having various flow-in angle ALPHA. This time, separation is apt to generate at the rear side 5 of the front edge 4 of blade 16, but due to the thick part 17, it is possible to minimize the generation of separation and noise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an axial fan used in ventilation and blowing equipment.

BACKGROUND OF THE INVENTION Conventionally, in this type of axial fan, as shown in FIG. The airfoil was configured so that only the chord length l varied depending on the change in radial position, and the curvature and wall thickness were changed in proportion to the chord length l.

Problems to be Solved by the Invention The conventional axial flow fan 7 described above is designed to provide collisionless flow during operation as shown in FIG. 4S when there is nothing in the suction port 1 as shown in FIG. However, as shown in FIG. 6, when a grid or filter 2 is provided at the suction port 1, the absolute velocity CM on the downstream side of the grid or filter 2 is not parallel to the axial direction, so the blade 3, the flow flows in with an inflow angle α rather than without collision. This inlet angle blur is all different for each blade and radial position because the flow behind the grid or filter 2 is not uniform. Therefore, it is not possible to design in advance so that collisionless flow occurs at any location on the blade 3.

When the inflow angle α exists, there is a problem in that a large separation flow 6 is generated on the rear side 5 at the leading edge 4 of the blade 3, and the noise increases rapidly.

The present invention has been made in consideration of the above-mentioned conventional problems, and an object of the present invention is to provide an axial flow fan with low noise.

Means for Solving the Problem In order to solve this problem, the present invention provides a
A semicircular thick part with a circumferential length of 2 to 10 inches and a radius of curvature of 1 inch to 6 inches relative to the chord length is provided on the back side of the leading edge of the circumferential cross section of the blade within the above range. This is an axial fan configuration.

With this configuration, even though the air sucked through the grid and filter is turbulent, the thick part provided on the back side of the leading edge of the blade suppresses the separation flow and reduces noise. That will happen.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 2. Note that the same numbers are given to the same parts as in the conventional example, and detailed explanations are omitted. In the figure, reference numeral 11 denotes a blower or a ventilation fan, and the suction port 1 is provided with a grid or filter 2. Reference numeral 12 denotes an axial fan, which is connected to a shaft 16 of an electric motor 14 installed inside the main body 13. The blades 16 of the axial fan 12 have a circumferential cross section of the blade 1e in a range of D/2 or more from the outer diameter.
As shown in the figure, 2% to 10% of the chord length l is placed on the back side 5 of the leading edge 4.
% and a radius of curvature of 1% to 6 inches.

This thick portion 17 is located at a distance D from the outer diameter of the axial fan 12.
It is provided with a size proportional to the chord length l of each radial position in a range of /2 or more.

In the above configuration, the electric motor 14 causes the axial fan 12 to
When the fan 12 rotates, the air sucked through the grid or filter 2 is turbulent at the rear of the grid or filter 2 and flows into the blades 16 of the axial fan 12 with various inlet angles d. At this time, peeling tends to occur on the back side 6 of the leading edge 4 of the blade 16, but since the thick portion 17 is provided, the peeling is small and the generation of noise is small. Note that FIG. 6 shows changes in air volume and noise when the size of the thick wall portion 17 is changed. Based on this, the optimum shape of the thick portion 17 was determined. Further, the noise due to disturbance at the tip increases as the circumferential speed increases, and the magnitude of the generated sound is proportional to the sixth power of the circumferential speed. Therefore, the sound is determined by the circumferential speed, and for an impeller with a certain blade outer diameter,
Regardless of the size of the outer diameter of the hub 8, it is necessary to determine the range in which the thick part 17 is formed with respect to the outer diameter of the impeller.As a result of experiments, it is determined that it should be set within a range of % or less relative to the outer diameter of the impeller. That had no effect.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, when a grid or filter is attached to the suction port of a ventilation fan or blower, flow separation at the leading edge of the blade of an axial flow of 7 am can be reduced. This is to reduce noise.

Figure 2 is a cross-sectional view of a coaxial flow fan, Figure 3 a
rc is a cross-sectional view of a blade of a conventional axial fan, Fig. 4a
is a cross-sectional view when there is no grid or filter at the suction port of the coaxial fan, Figure 4 is a diagram explaining the flow of the incoming air of the coaxial fan, and Figure 5 is a cross-sectional view when there is no grid or filter at the suction port of the coaxial fan. FIG. 6 is a cross-sectional view when there is a filter, and FIG. 6 is a diagram explaining the flow of incoming air from a coaxial flow fan. FIG. 6 is a diagram showing the relationship between the shape of the thick wall portion and performance.

4...Front edge, 6...Back side, 12...
...Axial fan, 16...Blade, 17
・・・・・・Thick part.

Name of agent: Patent attorney Toshio Nakao and 1 other person
4 Figure 6

Claims (1)

[Claims] A circumferential length of 2% to 10% of the chord length and a curvature of 1% to 5% on the back side of the leading edge of the circumferential cross section of the blade within the range of D/2 or more from the outer diameter D. An axial fan with a semi-circular thick wall.