JPH0270997A - Centrifugal blower - Google Patents

Abstract

PURPOSE:To improve aerodynamic performance and to reduce the generation of fluid noise by a method wherein at a cross section when a blade plate is cut by means of each plane crossing the rotary shaft of an impeller at right angles, the blade inlet size of the blade plate is gradually increased from a cross section in the vicinity of a main plate toward a cross section in the vicinity of a side plate. CONSTITUTION:A blade plate 9 has a blade inlet size D1 which is gradually increased from a main plate part 10 toward a side plate part 11. Since at each cross section, a blade front edge 13 is positioned in the vicinity of a blade back line 12 of a shape H in cross section of the fundamental blade of the main plate part 10, a blade inlet angle is gradually decreased from the main plate part toward the side plate part. Meanwhile, in an air flow flowing in an impeller 8, when it flows in between blade plates 9, there is a tendency for an inflow angle to increase at the main plate part 10 and to decrease at the side plate part 11 and therefore, the tendency of distribution of a blade inlet angle coincides with that of distribution of an air flow inflow angle. This constitution prevents production of wide displacement between the blade inlet angle and the air flow inflow angle at each cross section of the blade plate 9, and prevents peeling of an inflow air flow.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a centrifugal blower used in an air conditioner or the like, and particularly to improvement of its aerodynamic performance and reduction in noise.

BACKGROUND OF THE INVENTION Conventionally, centrifugal blowers have been widely used as blowers for air conditioners and the like, and there has been a great deal of interest in the noise caused by the blowers.

Therefore, a method has been taken in which the cross-sectional shape of the blades of the impeller is formed into an airfoil shape to reduce fluid noise.

The conventional centrifugal blower as described above will be described below with reference to the drawings.

FIG. 6 shows the structure of a conventional centrifugal blower. In FIG. 5, reference numeral 1 denotes a plastic impeller, which includes a plurality of blade plates 2 having an airfoil cross-sectional shape, a main plate 3 formed integrally with the blade plates, and an end surface of the blade plates 2 on the side opposite to the main plate. It is composed of side plates 4 fixed by welding. 6 is an electric motor directly connected to the impeller 1, and is fixed to a casing 6 that houses the impeller 1 and the electric motor 5. 7 is a suction bell mouth fitted into the casing eK and the installed girder suction port 6a.

FIG. 6 shows the cross-sectional shape of the blade plate 2 taken along planes D-D, E-E, and F-F perpendicular to the rotation axis of the impeller 1, and the blades have substantially the same cross-sectional shape. ing.

Also, β is the inflow angle of the airflow, and β1 is the feather ○ This is the root entrance angle.

The operation of the centrifugal blower configured as above will be described below.

First, when the impeller 1 is rotated by the driving force of the electric motor 5, air is introduced into the impeller 1 via the suction bell mouth 7, and as it passes between the plurality of blade plates 2, it applies static pressure and dynamic pressure. and is discharged from the impeller 1 into the casing 6. Thereafter, a part of the dynamic pressure is converted into static pressure within the casing θ and is discharged outside the casing θ to perform a blowing action.

At this time, as shown in Fig. 7, the inflow angle β of the airflow flowing into the impeller 1 differs depending on the same axial position within the impeller, and is generally smaller on the side plate side than on the main plate side. be. Therefore, the relationship between the blade population angle β and the airflow inflow angle β is as shown in Figure 8.
Q: Sea urchin is inconsistent in most positions. However, since the cross-sectional shape of the blade plate 2 is wing-shaped, the blade population angle β
Range 1 where the difference between and the airflow inflow angle β is small
.

In the area (hatched area in the figure), the airflow flows along the surface of the vane plate 2.

However, in areas other than the above, the blade population angle β and airflow inflow angle β. Since the difference between the blade plate 2 and In the side cross section, the airflow separates on the blade back surface 2b side of the blade plate 2.

Such separation of airflow around the vane plate 2 causes deterioration of fluid efficiency, deterioration of aerodynamic performance, and increase of fluid noise.

Problems to be Solved by the Invention As described above, in the conventional centrifugal blower, the flow tends to separate at the blade ventral surface 2a and the blade rear surface 2b at the main plate 3 side and side plate 4 side of the blade plate 2 formed into an airfoil shape. Therefore, there were problems such as deterioration of aerodynamic performance and increase of fluid noise.

In view of the above-mentioned problems, the present invention provides a low-noise centrifugal blower that prevents separation of the airflow when the airflow that flows into the impeller 1 flows between the blade plates 2, has high aerodynamic performance, and has low fluid noise. The purpose is to provide

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention aims to change the blade inlet diameter of the blade plate from the cross section near the main plate to the side plate in a cross section when the blade plate is cut along each plane perpendicular to the rotation axis of the impeller. While gradually expanding toward the nearby cross section, the blade back surface line is approximately the same in each cross section, with the blade plate cross section shape near the main plate as the standard blade shape,
The blade shape is formed by bringing the blade leading edge of each section close to the blade back line of the reference blade shape.

Function: Therefore, while maintaining the cross-sectional shape of each blade plate in the shape of an airfoil, the blade population angle gradually decreases from the cross section near the main plate to the cross section near the side plate, and the difference between the blade population angle and the airflow inflow angle in each cross section increases. This suppresses separation of the airflow when the airflow that flows into the impeller flows between the blade plates. Therefore, fluid efficiency is improved, aerodynamic performance is improved, and fluid noise is reduced.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. Incidentally, in order to avoid duplication, the same parts as in the conventional example are given the same numbers and the description thereof will be omitted.

FIG. 1 shows the structure of a centrifugal blower in an embodiment of the present invention.

8 is a plastic impeller, which is composed of a plurality of blades.

FIG. 2 is a cross-sectional view of the main part of the impeller 8 taken along a plane including the rotation axis, and shows the blade inlet diameter D1 of the blade plate 9 relative to the diameter D1a of the main plate cross-section and the diameter D1b of the side plate cross-section. D1
b=1.16×D1a, and the blade inlet diameter D1 is gradually expanded from the main plate part to the side plate part. Further, the inlet diameter D0 of the side plate 11 is made substantially the same as the blade inlet diameter D1b of the side plate portion of the blade plate 11.

FIG. 3 is a sectional view of the blade plate when the impeller 8 is cut along a plane perpendicular to the rotation axis.

The blade plate 9 has a cross-sectional shape H at the main plate portion as a basic blade shape,
The wing dorsal line 12 is substantially the same in each section, and in each section, the wing leading edge 13 is set close to the wing dorsal line 12 of the basic wing cross-sectional shape H, and the wing ventral line 14 is set close to the wing dorsal line 12 in each cross section. trailing edge 16
are connected by a smooth curve.

The operation of the centrifugal blower configured as above will be explained below.

In the blade plate 9, the blade inlet diameter D1 increases from the main plate part to the side plate part, and the blade leading edge 13 in each cross section is brought close to the blade back line 12 of the basic blade cross-sectional shape H of the main plate part. The entrance angle β1 gradually decreases from the main plate portion to the side plate portions. On the other hand, when the airflow that has entered the impeller 8 flows between the blade plates 9, the airflow has an inflow angle β at the main plate portion. is large, and the inflow angle is β at the side plate. has a tendency to become smaller, so the blade entrance angle β1
distribution and airflow inflow angle β. The trends of the distributions match. Therefore, in each cross section of the blade plate 9, the blade population angle β1 and the airflow inflow angle β. This eliminates large deviations in the flow rate and prevents separation of the incoming airflow.

Figure 4 shows the aerodynamic characteristics and noise characteristics.
Compared to conventional centrifugal blowers, it has higher static pressure and lower noise except in small flow areas, improves aerodynamic performance over a wide range of operating points, and reduces fluid noise. In addition, in FIG. 4, a solid line shows an example of the present invention, and a broken line shows a conventional example.

Moreover, since each cross-sectional shape of the blade plate 9 is all included in the basic blade cross-sectional shape H of the main plate portion, even when the blade plate 9 and the main plate 1o are integrally molded by injection molding or the like, they can be easily removed from the mold. This has great practical effects, such as being able to create a structure with high productivity.

Effects of the Invention As described above, the centrifugal blower of the present invention has a cross section when the blade plate is cut along each plane perpendicular to the rotation axis of the impeller.
The diameter of the blade inlet of the blade plate is gradually expanded from the cross section near the main plate to the cross section near the side plate, and the cross-sectional shape of the blade plate near the main plate is taken as the standard blade shape, and the blade back line is approximately the same in each cross section, and the leading edge of the blade is Since the shape of the vane is formed close to the blade dorsal line of the reference vane shape, separation of the incoming airflow at the inlet of the vane is suppressed, improving aerodynamic performance and reducing fluid noise. There is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a centrifugal blower according to an embodiment of the present invention;
Fig. 2 is a cross-sectional view of the main part of the impeller shown in Fig. 1, Fig. 3 is a cross-sectional view of the A-C cross section of Fig. 2 superimposed, and Fig. 4 is a diagram of aerodynamic performance and noise performance characteristics according to this embodiment. , Fig. 5 is a sectional view of a conventional centrifugal blower, Fig. 6 is a sectional view taken along line D-F in Fig.
The figure shows the distribution characteristics of the airflow inlet angle at the vane inlet in the conventional example, Figure 8 is a schematic diagram of the flow at the D-D cross section in Figure 5, and Figure 9 shows the flow at the F-F cross section in Figure 6. Model % formula % Agent's name Patent attorney Shigetaka Awano and 1 other person Figure 1: Quantity? Vane plate 13-- 1 iFl weave diagram

Claims (1)

[Claims] An impeller is constituted by a plurality of blade plates, a main plate to which the blade plates are fixed, and a side plate fixed to the end surface of the blade plate on the side opposite to the main plate, and the blade plate is fixed in each plane perpendicular to the rotation axis of the impeller. In the cross section when cut, the blade inlet diameter of the blade plate is gradually expanded from the main plate section to the side plate section, and the blade back line is set in each cross section using the cross-sectional shape of the main plate section of the blade plate as the standard blade shape. A centrifugal blower in which the blade shapes are substantially the same and each cross section has a blade leading edge close to a blade back line of the reference blade shape.