JPH04159498A - Impeller of multiblade fan - Google Patents

Abstract

PURPOSE:To obtain lowness of noise while holding conventional performance by setting a flow path width between blades to an optimum value while an outlet angle of the blade in an impeller to an optimum angle in pressure and negative pressure surface sides. CONSTITUTION:In an impeller 3, an air intake port 5 is formed in one axial line direction of the impeller further to close the other by a wall (main plate) 6 and also a boss 7 is mounted to the impeller so as to connect a shaft for driving the impeller rotated. A reinforcing ring 8 is mounted to a blade peripheral side in an air intake port side. Further, a blade 9 is mounted vertically to the main plate 6 to generate a pressure difference by a speed difference between internal and external diameters. Here, an outlet angle beta2 of a pressure surface is set to 140 to 160 deg., further an angle of a negative pressure surface is set to 170 to 180 deg., respectively. On the other hand, ratio (S2/S1) of an impeller inlet part flow path width S1 to an impeller outlet part flow path width S2 is set to 0.6 to 0.65.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-blade fan having forward-moving blades, and more particularly to a blade shape that is effective in reducing noise and increasing efficiency of the multi-blade fan.

[Conventional technology]

The conventional multi-blade fan with forward-moving blades was developed in 1986-4.
As described in Publication No. 9704, the arrangement of adjacent blades is as follows:
One part or the entire blade is arranged at equal intervals,
Its shape was composed of a circular arc, and its thickness was constant. Furthermore, as described in Japanese Utility Model Application Publication No. 53-31206, there are multi-blade fans in which the blades are shaped like airfoils instead of having a different thickness in order to improve aerodynamic performance or reduce noise. Are listed.

[Problem to be solved by the invention]

The prior art described in the above-mentioned Japanese Utility Model Application Publication No. 50-49704 is as follows:
The blades are all flat plate blades with the same thickness, and have a shape in which the entrance angle β1 and the exit angle β2 of the blades are determined and connected by a circular arc.

However, nothing is described about the channel width ratio between the blades. Also, from theory etc., the blade inlet angle β, =
90°, and the blade exit angle β2 = 180° is considered optimal, and the blade is drawn by connecting the curved line with a circular arc so that β = 90° and β2 = 180°. Since the shape is determined, it is not the optimal shape for the flow between the blades.

As a result, flow collision loss at the outlet of the blade, separation phenomenon on the suction surface of the blade, turbulence at the outlet of the blade, etc. occur, resulting in problems such as a decrease in aerodynamic performance and an increase in noise in the blower.

On the other hand, in order to solve the above-mentioned problems with flat blades,
As described in 3-31206, this is an example in which the shape of the blades is determined so that the shape of the flow path between the blades is the optimum value, but according to this, only the flow path is determined, and there is no mention of the optimal exit angle. . Moreover, it is quite difficult to manufacture such an impeller from the viewpoint of strength and other reasons when using an integrally molded impeller.

The present invention aims to improve fan efficiency and reduce noise by determining optimal blade inlet/outlet angles and flow path shapes, which are the problems of the prior art.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a multi-blade impeller molded integrally with plastic, with a blade exit angle on the pressure surface side of 140° to 16°. In addition, the exit angle of the blade on the suction side is set to 170° to 180° to reduce noise while maintaining maximum aerodynamic performance.

Further, the shape is such that the ratio of the outlet width to the inlet width of the flow path between the blades is maintained at an optimum level while maintaining the above-mentioned blade exit angle.

[Effect]

In conventional flat plate blades, the optimum blade entrance angle β and blade exit angle β2 are 90° and 180° based on theory and the like. In this case, the reference for each angle is basically based on the pressure surface, but it is the same even when the negative pressure surface is used as the reference.

According to the present invention, the exit angle β2 of the pressure surface is set to 140° to
The angle of the 16° negative pressure surface is set to 170° to 180°, which gives the conventional pressure exit angle, and further reduces the mixing loss at the outlet of the blade, thereby achieving the effect of reducing noise.

On the other hand, the flow path width S at the blade inlet and the flow path l1li at the blade outlet
By setting the ratio with iS2 (S2/S) to 0.6 to 0.65, the relative speed on the exit side of the blade is made slower than before, thereby aiming to improve performance.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

Figure 1 is a detailed view of the blade shape of the impeller of the present invention, Figure 2 is a front view of an impeller incorporating the blade shape of the present invention, Figure 3 is a side view of Figure 2, and Figure 4 is the main view of the impeller. FIG. 5 is a perspective view of the impeller of the invention housed in a case, FIG. 5 is a cross-sectional view thereof, and FIG. 6 is a conventional impeller shape.

As shown in FIG. 4, the centrifugal blower 1 has a substantially cylindrical impeller 3 housed inside a case 2. The impeller 3 is directly connected to a motor 1o, and the motor 10 rotates. The air taken in from the center of the impeller is guided in a spiral shape inside the case 2 and is blown out from the air outlet 4.

The overall view of the impeller will be explained with reference to FIG.

This example is an example in which a synthetic resin material is integrally molded using a mold. The impeller 3 has an air intake 5 formed on one side in the axial direction thereof, and the other side is blocked by a wall (main plate) 6, and a shaft for rotationally driving the impeller is formed. A boss 7 is attached for connection.

Further, a reinforcing ring 8 is attached to the outer circumferential side of the blade on the air intake side. This reinforcing ring prevents the blade from deforming toward the outer circumference due to centrifugal force. The blade 9 is attached perpendicularly to the main plate 6, and generates a pressure difference due to the speed difference between the inner and outer diameters. As the impeller 3 rotates, air flows in from the reinforcing ring 8 side, changes direction vertically from the inner diameter side of the impeller to the outer diameter side, passes through a separate space, and is discharged to the outer periphery of the impeller.

Moreover, the impeller made of integrally molded plastic had to be a conventional flat blade as shown in FIG. 5 for strength reasons. In this example, the plate thickness is the same from the blade inlet side to the blade outlet side. In this case, the entrance angle β□ is 90°
, the exit angle β2 is set at 180°. This method of determining the angle reference is the same for the pressure surface or the negative pressure surface. This angle is determined to be the optimum value based on theory or experimentation; for example, as β2 becomes 170' or 160°, the performance deteriorates and the noise increases.

Here, the shape of the blade of the present invention will be explained using FIG. 7. The blade inlet angle β and the outlet angle β2 are based on the suction side. The number of blades is Z=4 in this example.
3 pieces, blade outer diameter φD2=140m+, blade inner diameter φD
□=120m.

Next, the shape of one blade will be explained in detail. The outer diameter of the blade is 43
Draw a circle centered on the point on the line from the equally divided points to the center of the outer diameter of the blade. Draw a tangent to the circle from the center of the outer diameter of the blade to the point of the inner diameter of the blade. This forms the shape of the blade on the negative pressure side of the blade. This circular arc on the negative pressure side has a thickness t (1.5IIlo in this example) to create the shape on the pressure side. As a result, the entrance angle β1=90°, the exit angle β
A blade shape of 2=180′ and plate thickness t=1.5 on was formed. This is the blade shape of a conventional impeller, and in the present invention, a 30° tangent is drawn from the arc on the pressure side, and the outlet angle β2+ on the pressure side is set to 150°.

On the other hand, the exit angle β2- on the negative pressure side is 1806 as before.
It remains as it is.

The method of determining the shape in this embodiment has been described with reference to the suction surface, but the reference line may be on the blade pressure surface side instead of the blade suction surface side, or may be the center line of the blade plate thickness. Next, a method for determining the flow path will be described using FIG. 6. The line connecting the position of the pressure surface on the inner diameter side of the blade and the shortest point on the negative pressure surface of the adjacent blade is defined as the blade inlet channel width S□. On the other hand, on the outlet side, similarly, draw a line connecting the shortest point on the suction surface of the adjacent blade from the position on the blade outer diameter side of the blade pressure surface to the blade outlet flow path width S.
2.

Ratio S2/S1 of the inlet channel width S and outlet channel width S2
The blade shape is determined so as to set the value to 0.6 to 0.65. In this case, if the blade is a flat plate as shown in Fig. 8, the inlet channel width S1
Since the ratio of the outlet flow path width S2 to the outlet flow path width S2 is only about 0.5 to 0.55, it has an airfoil shape as shown in FIG.

The blade shape of the present invention will be explained using FIG.

First, the pressure surface line will be explained. The entrance angle β of the blade is 90° as in the conventional case.

On the other hand, the blade exit angle β2+ is 150°. The way the line is drawn between the outlet and the inlet is the same as described above.

Next, we will explain how to draw the line on the negative pressure surface.

A circular arc is drawn so that the blade exit angle β2+ is 180°.

As a result, the shortest distance between the outlet of the pressure surface and the negative pressure surface is defined as the blade outlet flow path width S2.

A circle 1.6 times larger than this blade outlet channel width S2 is drawn at the blade pressure surface inlet. Smoothly connect the arcs drawn from the blade outlet so that they touch this circle. The diameter of the circle mentioned above is defined as the blade inlet flow path @S. Furthermore, connect the inner diameter position of the blade pressure surface and the line drawn on the negative pressure surface with an R. The blade inlet channel width S□ and the blade outlet channel width S2 are made to gradually connect.

Regarding the above blade shapes, experimental results comparing conventional impellers will be explained using FIGS. 9 and 10. 9th
As can be seen from the figure, the conventional flat blade (inlet angle β1 = 9
0°, exit angle β2 = 180'), and set the blade pressure side exit angle β2+ to 150° suction side exit angle β2-.
Although the aerodynamic performance of the blade with the angle of 180 degrees is the same as that of conventional blades, the noise is reduced by 2 dB. This β
For 2+, the noise is the lowest between 140° and 160°, and when β2+ is made even smaller than 140°, both noise and performance deteriorate rapidly.

Moreover, the results of performance and specific noise with respect to the inlet/outlet channel width ratio are shown in FIG. From this figure, S2/S1 is 0.6 to 0.
65, the effect of dramatically improving performance and specific noise level was obtained.

〔Effect of the invention〕

According to the present invention, the exit angle of the blades of the impeller is set to the optimum angle on the pressure side and the suction side, and in addition, the optimum value of the width of the flow path between the blades is found, which makes it possible to It is possible to achieve the effect of reducing noise while maintaining performance.

[Brief explanation of drawings]

FIG. 1 is a front view showing the blade shape of an embodiment of the present invention, FIG. 2 is a front view of the impeller, FIG. 3 is a longitudinal sectional view of the impeller, and FIG. 4 is the impeller of the present invention. 511' is a vertical sectional view taken along arrows A-B-C in FIG. 4, FIG. 6 is a front view showing the conventional blade shape, and FIGS. 7 and 8 are FIG. 9 shows the blade shape of the present invention, respectively.
The figure shows performance and noise measurement results, and FIG. 10 shows the performance results with respect to channel width ratio. DESCRIPTION OF SYMBOLS 1... Centrifugal blower, 2... Case, 3... Impeller, 9... Vane, 10... Motor. , 2- Agent Patent attorney Katsuo Ogawa 1-" °〈 '81 Figure 2 Figure box direction collection 3 Not illustrated 4 Figure name Sl!l ¥, bffi ¥3 l thirst〃 q Figure IwM t40' t2o0 1000 yr 艮Pressure surface turtle support β2 position 10 1￥1 S, 13゜

Claims (3)

[Claims] 1. In a multi-blade impeller that can be integrally molded from plastic, a plurality of blades parallel to the axis and whose length does not change are vertically attached to the main plate, and the outer diameter of the suction side of the blades is supported by a reinforcing ring. An impeller for a multi-blade fan characterized in that, when the exit angle of the pressure surface is β_2, the exit angle β_2_p of the pressure surface is 140° to 160°. 2. When the exit angle of the blades of the impeller is β_2,
The impeller for a multi-blade fan according to claim 1, wherein the exit angle β_2_n of the suction surface is 170° to 180°. 3. The multi-blade fan impeller according to claim 1, wherein the ratio of the outlet width to the inlet width of the air passage constituted by adjacent blades is 0.60 to 0.65.