JPH0458100A - Multiblade centrifugal fan - Google Patents

Abstract

PURPOSE:To prevent the reverse flow of air to the inside of an impeller by making the height of a reverse flow preventing plate provided on a fan casing side wall on the opposite side of an intake, in a circumferential direction close to the periphery of the impeller around a throat portion, nearly equal to the distance from the fan casing side wall on the opposite side of the intake to a main blade of the impeller. CONSTITUTION:A fan casing 2 is provided so as to enclose a cylindrical impeller 1 consisting of a large number of blades, and an intake 3 is provided on one side wall of the fan casing 2, and an outlet 4 is provided in a tangential direction on the circumference of the fan casing 2. A throat portion 5 is constructed on one brim of the outlet 4, and a rotation means 6 to rotate the impeller 1 is provided, and a reverse flow preventing plate 7 is provided on the side wall of the fan casing 2 on the opposite side of the intake 3. Where, the reverse flow preventing plate 7 is placed at least near to the throat portion 5 and in a circumferential direction close to the periphery of the impeller 1, and the height of the plate 7 is made to be nearly equal to the distance from the side wall of the fan casing 2 on the opposite side of the intake 3 to a main blade 9 of the impeller.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a multi-blade centrifugal fan with improved air blowing performance and further reduced noise caused by air blowing.

Conventional technology A multi-blade centrifugal fan is provided with a backflow prevention plate to prevent backflow from the outside to the inside of the impeller (for example, Japanese Patent Laid-Open No. 166796/1983).

A conventional multi-blade centrifugal fan will be explained below with reference to FIGS. 7 and 8.

In FIGS. 7 and 8, 11 is a multi-blade cylindrical impeller. 12 is a fan casing provided to surround the impeller 11, and the impeller 11 is provided on one side of the fan casing.
A circular inlet 13 is provided so as to be coaxial with the inlet.

14 is an outlet provided tangentially on the circumference of the fan casing, and the first class of the outlet 14 has a throat portion 1.
5 is formed.

Reference numeral 16 denotes a motor for driving an impeller, which is provided on the opposite side of the inlet 13 so as to be coaxial with the impeller 11.

Reference numeral 17 denotes a backflow prevention plate provided close to the outer circumferential surface of the blades of the impeller 11 around the throat portion 15 .

The backflow prevention plate 17 has a height substantially equal to the width of the blades of the impeller 11, and is therefore provided to substantially cover the outer peripheral surface of the impeller 11 around the throat portion 15.

Reference numeral 18 denotes a bent portion in which the upstream end of the backflow prevention plate 17 is bent toward the circumferential surface of the fan casing 12 .

In the above configuration, the impeller 1 is driven by the motor 16.
1 rotates, air is sucked in from the inlet 13 by the blower action of the impeller 11, and then pressurized by the blades of the impeller 11 and forced out of the system from the outlet 14. At this time, the inside of the impeller 11 has a low pressure and the outside has a high pressure. Especially, the pressure difference is the largest around the throat 15, and some of the air tries to flow back from the outside to the inside of the impeller 11 (the backflow The action of the prevention plate 17 prevents the backflow.Furthermore, the pressure impact on the backflow prevention plate 17 is alleviated by the bent portion 18, and the interference noise between the backflow prevention plate 17 and the impeller 11 is alleviated to some extent.

Problems to be Solved by the Invention However, with the above conventional configuration (the backflow prevention plate 17
has a height approximately equal to the width of the blades of the impeller 11, and therefore is provided to substantially cover the outer peripheral surface of the impeller 11 around the throat portion 15. This problem occurs because the flow of air is blocked by the backflow prevention plate 17, which reduces the air volume and significantly deteriorates the airflow characteristics.Also, this problem occurs because the blades of the impeller 11 and the backflow prevention plate 17 almost overlap. Although the interference noise caused by the bending is alleviated to some extent by providing the bending portion 18, it is not a sufficient solution. It is an object of the present invention to provide a multi-blade centrifugal fan that can increase the static pressure of the multi-blade centrifugal fan, improve the air volume characteristics, and improve the noise characteristics at the same time.

Means for Solving the Problem In order to achieve this object, a multi-blade centrifugal fan according to the present invention is provided with a fan casing surrounding a cylindrical impeller consisting of a large number of blades, an inlet is provided, an outlet is provided in a tangential direction on the circumference of the fan casing, a throat is formed at one edge of the outlet; a rotation means for rotating the impeller is provided; A backflow prevention plate is provided on the side surface of the fan casing, and the backflow prevention plate is installed at least near the throat and in the vicinity of the outer peripheral surface of the impeller in the circumferential direction from the side of the fan casing opposite to the inlet. The height is the same as the impeller main plate.

In this configuration, when the impeller is rotated by the motor (Table 1), the inside of the impeller has low pressure and the outside has high pressure, and the pressure difference is especially large around the throat. A portion of the air flows back into the impeller through the gap between the side of the fan casing on the opposite side of the inlet and the main plate of the impeller. The backflow prevention plate, which has approximately the same height as the above, prevents this.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3.

In the figure, reference numeral 1 denotes an impeller formed by arranging a large number of blades in a cylindrical shape, and the blades are forward-facing blades that are inclined in the direction of rotation shown by arrow A.

Reference numeral 2 denotes a fan casing provided surrounding the impeller, and one side thereof has a circular inlet opening with a size slightly smaller than the inner diameter of the blades of the impeller 1 so as to be coaxial with the impeller 1. 3 is provided.

Reference numeral 4 indicates an outlet provided tangentially on the circumference of the fan casing, and a throat portion 5 is formed at one edge of the outlet 4. Reference numeral 6 indicates an outlet opposite to the inlet 3. (iii) A motor for driving an impeller, which is provided coaxially with the impeller 1.

Reference numeral 7 denotes a backflow prevention plate that is provided in the vicinity of the throat portion 5, close to the outer circumferential surface of the blades of the impeller 1, and integrally formed with the fan casing side surface 8 on the side opposite to the inflow port 3 in the circumferential direction.

The backflow prevention plate 7 has a height approximately extending from the side surface 8 of the fan casing opposite to the inlet 3 to the main plate 9 of the impeller.

The operation of the multi-blade centrifugal fan configured as described above will be explained below. When the impeller 1 rotates due to the drive of the motor 6, air is sucked through the inlet 3 by the blower action of the multi-blade centrifugal fan. It is pressurized by the vanes of the wheel 1 and pumped out of the system through the outlet 4. At this time, the pressure inside the impeller 1 is low and the pressure outside is high, and the pressure difference especially around the throat 5 becomes large. Therefore, some of the air flows back inside the impeller 1 through the gap between the fan casing side surface 8 on the opposite side of the inlet and the impeller main plate 9, as shown by arrow B. However, the backflow prevention plate 7 prevents this from occurring.

FIG. 4 shows the relationship between the air volume Q and the rotational speed n of the multi-blade centrifugal fan having the conventional backflow prevention plate 17 shown in FIG. 7 and the multi-blade centrifugal fan having the backflow prevention plate 7 of the above embodiment. show. a
b shows the air volume characteristics of the multi-blade centrifugal fan equipped with the conventional backflow prevention plate 17, and b shows the air volume characteristics of the multi-blade centrifugal fan equipped with the backflow prevention plate 7 of this embodiment. As is clear from Figure 4
It can be seen that the air volume characteristics are improved compared to the case where the conventional backflow prevention plate 17 is used.

Figure 5 shows the relationship between sound dB and rotational speed n, where a is the conventional case and b is the case when the backflow prevention plate 7 of this embodiment is used.As expected, the sound characteristics are improved compared to the conventional one. .

FIG. 6 shows the relationship between the air volume Q and the pressure P of a multi-blade centrifugal fan without a backflow prevention plate and a multiblade centrifugal fan provided with the backflow prevention plate 7 of this embodiment.

b shows the P-Q characteristic of the multi-blade centrifugal fan equipped with the backflow prevention plate 7 of this embodiment, and C shows the P-Q characteristic of the multi-blade centrifugal fan without the backflow prevention plate.

As shown in FIG. 6, it can be seen that the static pressure can be increased in this embodiment as well as in the conventional multi-blade centrifugal fan equipped with the backflow prevention plate 17.

As described above, according to this embodiment, the blades of the impeller 1 around the throat portion 5 are located close to the outer peripheral surface of the blades in the circumferential direction! M. A backflow prevention plate 7 is provided integrally with the fan casing side surface 8 opposite to the inlet 3, and the backflow prevention plate 7 extends approximately from the fan casing side surface 8 opposite to the inlet port 3 to the impeller main plate 9. By having a height, the impeller 1
Fan casing side 8 opposite to inlet 3 from the outside of
It is possible to prevent the air from flowing back into the impeller 1 through the gap between the main plate 9 and the impeller 1 as shown by the arrow B, and therefore prevent the air from flowing inside the fan casing 2 as in the conventional example. The flow becomes smoother, the static pressure of the multi-blade centrifugal fan can be increased, and the wind noise and periodic flapping noise of the multi-blade centrifugal fan due to backflow can be reduced.

Furthermore, since the backflow prevention plate 7 has a height that extends from the side surface 8 of the fan casing opposite to the inflow port 3 to approximately the impeller main plate 9, the backflow prevention plate 7 has a height that extends from the fan casing side surface 8 on the opposite side to the inflow port 3 to approximately the impeller main plate 9.
This eliminates the possibility of covering the outer circumferential surface of the blades of the impeller 1, which allows air to flow out smoothly from the vicinity of the throat portion 5, thereby improving air volume characteristics.The blades of the impeller 1 and the backflow prevention plate 7 do not overlap, so there is no interference. There is no sound, and the noise of the multi-blade centrifugal fan can be reduced accordingly.

In this embodiment, a backflow prevention plate 7 is provided in the circumferential direction near the impeller 1 around the throat 5, but this is because the pressure difference is particularly large around the throat and backflow is likely to occur. There is a possibility of backflow to some extent in other areas near the impeller 1, so it is absolutely necessary to provide a backflow prevention plate in that area in the same way as the one around the throat, and this will reduce the blowing efficiency. However, the same effect as that of this embodiment can be obtained.

Effects of the Invention As described above, the multi-blade centrifugal fan of the present invention is provided with a backflow prevention plate on the side surface of the fan casing opposite to the inlet in the circumferential direction close to the outer peripheral surface of the impeller around at least the throat, and The backflow prevention plate has a height approximately from the side of the fan casing opposite to the inlet to the main plate of the impeller, so that it extends from the outside of the impeller to the side of the fan casing opposite to the inlet and the main plate of the impeller. It is possible to prevent air from flowing back into the impeller through the gap between the fan casing and the fan casing, thereby smoothing the air flow within the fan casing and increasing the static pressure of the multi-blade centrifugal fan. It is also possible to reduce the wind noise and periodic flapping noise of the multi-blade centrifugal fan due to backflow.

In addition, since the backflow prevention plate force (the height is approximately from the side of the fan casing opposite to the inlet to the impeller main plate), the backflow prevention plate covers the outer peripheral surface of the impeller blades as in the conventional case. As a result, air can flow out smoothly from the impeller blades around the throat, improving air volume characteristics.Also, since the impeller blades and the backflow prevention plate do not overlap, there will be no interference noise. The noise of the multi-blade centrifugal fan can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a front view of a multi-blade centrifugal fan equipped with a backflow prevention plate according to an embodiment of the present invention. FIG. 2 is a sectional view taken along line C-C in FIG. Figure 4 shows the relationship between air volume and rotational speed @ Figure 5 shows the relationship between sound and rotational speed @ Figure 6 shows the relationship between static pressure and air volume @ Figure 7 shows the conventional backflow prevention plate Front view of multi-blade centrifugal fan with
The figure is a sectional view taken along line E-E. ■・・・Impeller 2・・・・Fan casing Hisashi 3・
... Inflow port 4 ... Outflow port 5 ... Throat
6...Motor, 7...Backflow prevention plate, 8...
...Measuring the fan casing on the opposite side of the inlet 9...
・Name of the impeller Kaede agent Patent attorney Shigetaka Awano and 1 other person
Famous confectionery 1 bite) K in O Liquid white O Throat rabbit motor Gyakushoku Odome Denmoi 〇 to anti-t1111V's Fu7puke sink WniIO Rippo Shizukuo Go 4 Figure 3 Figure 6 Mouth 11 number n → Tan Responsibility Q+

Claims (1)

[Claims] An inlet is provided on one side of a fan casing that surrounds a cylindrical impeller consisting of a large number of blades, an outlet is provided in a tangential direction on the circumference of the fan casing, and a throat is provided at one edge of the outlet. a rotation means for rotating the impeller; a backflow prevention plate is provided on a side surface of the fan casing opposite to the inlet, and the backflow prevention plate is arranged at least near the throat and on the outer peripheral surface of the impeller. A multi-blade centrifugal fan characterized by having a height approximately in the circumferential direction from the side of the fan casing opposite to the inlet to the main plate of the impeller.