JPH0551798B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a mixed flow fan.

BACKGROUND OF THE INVENTION In recent years, mixed flow fans have been widely used in air conditioning, heating equipment, electronic equipment cooling, ventilation fans, etc. However, on the other hand, they have become a major source of noise. These devices are often used in places that are close to living spaces, and there is a strong demand for lower noise levels due to recent neighborhood noise issues.

An example of the conventional fan mentioned above will be described below with reference to the drawings.

Conventionally, a propeller fan having a simple guide, as shown in FIGS. 6 and 7, includes an impeller 3 having a plurality of blades 2 attached to the outer circumference of a cylindrical hub 1, and this impeller 3. A flat guide 6 is provided on the outer periphery of the pipe so as to partition a suction part 4 and a discharge part 5 (Japanese Patent Application Laid-Open No. 1986-1999).
No. 156998).

In general, this type of fan has a forward tilt angle θ in the direction of rotation on the blade surface, which increases the nz noise (frequency f is the product of the rotational speed n and the number of blades z) due to pulsating interference between the blades and surrounding resistance objects. It is considered that a major effect is to attenuate the rotational noise (expressed by

However, when the blade surface is tilted forward in the direction of rotation, the following problems occur.

Important specifications that determine the basic performance of an impeller include the inlet and outlet angles of the blades, and the chord length.

Therefore, the basic wing surface shape that satisfies the target performance is the 8th.
Assume that it is determined as shown in the figure. Here, if θ is the optimal forward inclination angle that reduces noise, the 8th
The wing surface shown in the figure can be tilted forward by θ and designed into the shape shown in FIG. 9. Also, when comparing the side shapes of the cross section passing through line B'-B' in the radial direction, as shown in Fig. 10, the one in Fig. 9 has a shape inclined in the blowing direction, and this inclination is determined by the forward inclination angle. , which affects the radial flow and thus changes the basic performance of the impeller. Although it is necessary to make modifications to prevent this, this greatly complicates the design of the impeller and significantly hinders the optimal selection of basic performance and forward inclination angle.

Therefore, as one plan to solve the above problem, as shown in FIG. 11, a plurality of blades 2 that generate diagonal flow acceleration are planted on the peripheral wall surface of a truncated cone-shaped hub portion 1. It is conceivable to attach a triangular plate 5 to the lost end of the blade leading edge 3 in a mixed flow fan.

This will enable a simple design and attenuate nz sound (rotational noise whose frequency f is expressed by the product of the number of rotations n and the number of blades z) without interfering with basic performance.

Problems to be solved by the invention However, for such fans,
When air flows at high speed, the flow tends to separate near the triangular plate, so how to determine the shape and dimensions of the triangular plate is a very important issue in improving the noise characteristics of the blower.

Means for Solving the Problems In order to solve the above problems, the mixed flow fan of the present invention has optimized the shape and dimensions of a triangular flat plate that is in close contact with the tip of the leading edge of the blade.

Effects According to the present invention, with the above-described configuration, when the air flow sucked into the fan collides with the end face of the triangular flat plate, the air flow is optimal in terms of the performance of each shape and dimension of the triangular flat plate, so that the air flow is separated. It is difficult for this to occur, and the flow begins to flow along the wing surface.

Embodiment Hereinafter, a mixed flow fan according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a plan view of essential parts of a mixed flow fan in a first embodiment of the present invention.

In the figure, 1 is a truncated conical hub, 2 is a blade attached to the outer periphery of the hub 1, 3 is a front edge of the blade,
Reference numeral 4 indicates a rear edge of the blade, 5 a triangular flat plate, and 6 an arrow indicating the direction of rotation. FIG. 2 is an enlarged view of the triangular flat plate 5 in FIG. 1.

As described above, according to this embodiment, the blade leading edge 3
By optimizing the shape and dimensions of the triangular flat plate 5 that is in close contact with the triangular flat plate 5, the flow of suction air that collides with the end face of the triangular flat plate 5 will not cause separation there.
Noise characteristics can be improved.

FIGS. 3, 4, and 5 are graphs showing the relationship between representative dimension ratios and noise characteristics of a triangular flat plate when the operating point is kept constant.

Here, l is the dimension of the base of the triangular flat plate 5, L is the length of the leading edge of the blade, h is the height of the triangular flat plate 5, and H is the extension of the base line of the height h to the leading edge of the blade. shows the distance.

From this graph, the optimal size range for each is
At least 0.2≦1/L≦0.4, 0.7≦h/H≦1.1
It can be seen that it exists in the range of 100°≦β≦120°.

Effects of the Invention As described above, the present invention optimizes the shape and dimensions of the triangular flat plate that is brought into close contact with the tip of the leading edge of the blade, thereby making it difficult for the air flow to separate at the triangular flat plate, and It is possible to promote flow along the surface and reduce high frequency noise caused by separation and vortex flow.

[Brief explanation of the drawing]

Fig. 1 is a plan view of essential parts of a mixed flow fan in an embodiment of the present invention, Fig. 2 is an enlarged view of a triangular flat plate portion in the same mixed flow fan, and Figs. Characteristic diagrams showing noise characteristics with respect to major dimension ratios. Figures 6 and 7 are longitudinal cross-sectional views and back views of conventional examples of propeller fans. Figure 8 is a plan view of main parts of conventional mixed flow fans. Figure 9 is a plan view of the main parts of the mixed flow fan with the forward inclination angle θ in Figure 8, Figure 10 is the line BB in Figures 7 and 8;
FIG. 11, a sectional view taken along line B'-B', is an explanatory diagram of one solution to the conventional example. DESCRIPTION OF SYMBOLS 1... Hub part, 2... Impeller, 3... Blade front edge part, 4... Blade rear edge part, 5... Triangular flat plate, 6...
…Direction of rotation.

Claims (1)

[Claims] 1. A truncated conical hub for receiving power from the outside and a plurality of blades arranged around the hub, the leading edge of the blade having a substantially straight shape when viewed from the rotational direction. At the leading edge of each blade of the mixed flow fan, which is the target, a triangular flat plate with a thickness almost the same as the blade thickness is placed.
It is integrally molded so as to be extrapolated from the leading edge in the direction of rotation,
one side of the flat plate substantially follows the outer circumference of the fan;
The other side is H, which is the length of a perpendicular drawn from the outer apex of the trailing edge of the blade to the leading edge of the blade in the reverse rotation direction in a mixed flow fan that is placed close to the outer periphery of the leading edge of the blade.
The length of the leading edge of the blade is L, the length of the side of the triangular flat plate that is in close contact with the leading edge of the blade is l, the height of the triangular flat plate with the side l as the lower side is h, and the three sides of the triangular flat plate. When the angle between the side located closer to the inner circumference and the front edge is β, the triangular plate is set so that 0.2≦1/L≦0.4 0.7≦h/H≦1.1 100°≦β≦120° Diagonal flow fan.