JPH0450478Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a single-suction type centrifugal blower that prevents discharge pressure and efficiency from decreasing within a local air volume range.

(Prior Art) As a conventional single-suction type centrifugal blower, there is one shown in FIGS. 1 and 2. The centrifugal blower 1 shown in FIGS. 1 and 2 includes a scroll-shaped casing 2 that is manufactured at low cost by welding steel plates, etc., and is connected to the leeward side of a flow path 3 that is approximately rectangular in cross section and is formed by this casing 2. It has a discharge pipe 4. The casing 2 includes a scroll portion 5 forming a scroll curve, side plates 6 and 7,
It consists of a suction pipe 8 disposed on one side plate. Further, an impeller 11 is fixed to the tip of a cantilever support shaft 10 supported by a bearing 9, and this impeller 11 is located closer to the side plate 6 on the bearing 9 side than the center of the flow path 3 formed by the casing 2. They are arranged side by side, and a large space is provided between the impeller 11 and the side plate 7 on the suction pipe 8 side. The reason why the impeller 11 is arranged unevenly is to reduce the oscillation vibration of the impeller 11 by shortening the overhang length of the cantilever support shaft 10, and to reduce the vibration of the air generated in the flow path 3. This is to stabilize the next flow (air flow indicated by arrow A in FIG. 1). This secondary air flow A occurs for the following reasons. That is, if there is a space between the impeller 11 and the side plates 6 and 7, the impeller 1
The high-speed flow discharged from the scroll member 1 flows not only toward the scroll portion 5 but also toward the side plates 6 and 7 due to the diffusion effect in a swirling manner. The flow toward the side plates 6, 7 is caused by the side plates 6, 7 and the impeller 11.
It forms a spiral shape that revolves between the shroud and the side wall of the shroud. Furthermore, the air sucked in in the axial direction from the suction pipe 8 is converted into a radial flow in the impeller 11, but due to the velocity component toward the bearing 9 side in the axial direction, the shroud on the bearing 9 side of the impeller 11 is It hits the inner wall and is bounced back, and is discharged from the impeller 11 in a diagonal direction toward the suction pipe 8 in a high-speed flow. Due to the velocity component of this high-speed flow toward the suction pipe 8 side, air tends to flow from the bearing 9 side to the suction pipe 8 side within the flow path 3 . Incidentally, the spiral flow generated in the space between the shroud of the impeller 11 and the side plates 6 and 7 tends to disturb the flow along the scroll portion 5 in the flow path 3. Therefore, the impeller 11 is attached to the side plate 6 on the side of the bearing 9.
The space between the impeller 11 and the side plate 6 on the side of the bearing 9 is narrowed to reduce the spiral flow generated therebetween, and the space between the impeller 11 and the side plate 7 on the suction pipe 8 side is narrowed. The spiral air flow between the impeller 11 and the side plates 6 and 7 is stabilized by increasing the space and increasing the radius of the spiral that occurs therebetween. As a result, a secondary flow A is generated due to the spiral flow between the impeller 11 and the side plate 7 and the velocity component of the high-speed flow discharged from the impeller 11 toward the suction pipe 8 side.

In the case of blowers with high discharge pressure, the cross-sectional shape of the flow path in the casing is configured into a trapezoid or circle that gradually expands from the outer diameter of the impeller, so that there is no space between the side plate of the casing and the impeller. is not provided. In order to efficiently convert the kinetic energy of the high-speed flow discharged from the impeller into pressure energy, the casing has a structure that does not generate secondary flows.

(Problem to be solved by the invention) By the way, in order to reduce the size and weight of the above-mentioned single-suction type centrifugal blower 1, it is necessary to increase the exit angle of the blades of the impeller 11 and reduce the outer diameter of the impeller 11. At the same time, it is necessary to reduce the diameter of the scroll curve formed by the scroll portion 5 of the casing 2.

However, when the diameter of the scroll portion 5 is reduced to make it more compact, the cross-sectional area of the flow path 3 near the throat portion 12 at the end of scroll winding becomes smaller, and as shown by the solid line in FIG. 5, the local flow path coefficient decreases. A drawback occurred in that both the head coefficient h _t and the total pressure efficiency η _t decreased with respect to q. That is, the discharge pressure and efficiency decrease within a local air volume range of the centrifugal blower 1.
In particular, if this local air volume range occurs near the maximum efficiency point of the centrifugal blower 1, the centrifugal blower 1
Depending on the operating conditions, the above-mentioned discharge pressure and efficiency may be reduced depending on the operating conditions, which is a very serious drawback from the viewpoint of energy saving.

Therefore, the inventor of the present invention proposed that the air flow between point B near the side plate 7 of the flow path 3 near the throat 12 at the end of scroll winding and point C near the side plate 6 (points B and C are shown in FIG. 1). When the flow velocity was measured, as shown by the solid line in Figure 6, the flow coefficient q in the local range was found to be between points B and C.
It was found that the difference in flow velocity between the point and the point suddenly becomes significantly large, and it coincides with the flow coefficient q in the range where the discharge pressure and efficiency decrease. This is achieved by downsizing the casing 2 of the single-suction type centrifugal blower 1.
Both the main flow and the secondary flow A flowing toward the discharge pipe 4 along the scroll portion 5 increase in speed, and flow toward the side plate 7 on the suction pipe 8 side in the flow path 3 on the discharge pipe 4 side near the throat 12 at the end of the scroll winding. This is thought to be because the drift of the current becomes significant.

The purpose of the present invention is to improve the drawbacks of conventional centrifugal blowers, and to provide a centrifugal blower that does not reduce discharge pressure and efficiency within a local air volume range. .

(Means for Solving the Problems) In order to achieve this object, the centrifugal blower of the present invention is provided with a scroll-shaped casing having a substantially rectangular flow path cross section, and an impeller and a side plate of the casing on the suction pipe side. In a single-suction type centrifugal blower having a space between the ends of the scroll, a discharge port of the impeller is parallel to the side plate in the flow path near the throat at the end of the scroll winding, and is on the suction pipe side with respect to the impeller. A current plate is disposed nearby, and the flow path in a section near the throat is divided by the current plate into a discharge side of the impeller and a space side on the suction pipe side on a plane parallel to the side plate. It is configured.

(Function) Since the flow path is divided by a rectifying plate into the discharge side where discharge is discharged from the impeller and the space side between the impeller and the side plate on the suction pipe side of the casing, the flow path is discharged from the impeller and due to the diffusion effect. The rectifying plate restricts the flow that swirls toward the side plate, and also restricts the diagonal discharge of the high-speed flow due to the axial velocity of the high-speed flow discharged from the impeller.
As a result, the secondary flow A is suppressed, and the flow velocity is prevented from being significantly biased depending on the position within the flow path.

(Example) The present invention will be described below with reference to FIGS. 3 and 4. FIG. 3 is a cross-sectional view of one embodiment of the single-suction type centrifugal blower of the present invention, and FIG.
It is a YY' cross-sectional view of the centrifugal blower shown in the figure. In FIGS. 3 and 4, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals, and redundant explanation will be omitted.

In the single-suction type centrifugal blower 1' shown in FIGS. 3 and 4, the flow path 3 of the casing 2 is
A rectifier plate 13 divided parallel to the side plates 6 and 7 is disposed in a section spanning from the windward side to the leeward side discharge pipe 4, straddling the scroll winding end throat 12.
Further, the current plate 13 is arranged slightly closer to the side plate 7 on the side of the suction pipe 8 than the impeller 11, so that it is not directly exposed to the high-speed flow discharged from the impeller 11. The current plate 13 allows the flow path 3 to be connected to the discharge side where the air is discharged from the impeller 11 in the vicinity of the throat 12 at the end of scroll winding, and the impeller 11 and the suction pipe 8 in the dividing plane parallel to the side plates 6 and 7. It is completely divided into two parts: the space between the side plate 7 on the side and the space side.

In this configuration, the rectifying plate 13 regulates the flow discharged from the impeller 11 and swirling toward the side plate 7 side due to the diffusion effect, and the high-speed flow discharged from the impeller 11 is controlled by the side plate on the suction pipe 8 side. Discharge of the high-speed flow in an oblique direction due to the velocity component in the axial direction toward 7 is restricted. As a result, the secondary flow A is significantly suppressed, and significant drift toward the side plate 7 is prevented.

Therefore, point B near the side plate 7 and point C near the side plate 6 of the flow path 3, which is divided into two into the discharge side and the space side (points B and C are shown in Fig. 3).
If we measure the air flow velocity between points B and C, the difference in flow velocity between points B and C will be reduced compared to the conventional method, as shown by the broken line in Fig. 6, in the local range of flow coefficient q.
Further, the difference in flow velocity does not change suddenly. Therefore, as shown by the broken line in Fig. 5, the head coefficient h _t and the total pressure efficiency η _t change smoothly with respect to the change in the flow coefficient q, and the centrifugal blower 1' is able to discharge air within a local air volume range. Pressure and efficiency will not decrease.

Further, the current plate 13 is arranged so that the impeller 11 is not directly exposed to the high-speed flow discharged from the impeller 11.
Since it is arranged slightly closer to the side plate 7 on the side of the suction pipe 8 than 1, dust adhesion and friction to the rectifying plate 13 are reduced, and the rectifying plate 13 prevents the discharge of high-speed flow from the impeller 11. There will be no hindrance.

In the above embodiment, the edge 13a of the current plate 13 is formed in a straight line close to the outer diameter of the impeller 11, but as shown in FIG.
The edge 14a of the impeller 11 may be formed into an arc shape that approximates the outer shape of the impeller 11, and the flow path 3 can be divided into two parts more completely, and the difference in flow velocity depending on the position of the flow path 3 can be reduced. can.

Furthermore, as shown in FIG.
5 and 15 may be arranged to divide the flow path 3 into three by a dividing plane parallel to the side plates 6 and 7. When the impeller 11 is arranged at the center of the casing 2, the two rectifying plates 15, 15 are arranged on both sides of the impeller 11, which is suitable for reducing the difference in flow velocity depending on the position of the flow path 3. It is.

(Effects of the invention) As explained above, according to the centrifugal blower of the invention, the rectifying plate can suppress the secondary flow generated in the flow path in the vicinity of the throat at the end of the scroll winding, and the position of the flow path The difference in flow velocity due to
Air can flow evenly throughout the flow path. As a result, it is possible to eliminate the sudden drop in discharge pressure and efficiency in a localized air volume range that occurs in conventional devices, and it is possible to easily reduce the size and weight of the single-suction type centrifugal blower. Moreover, since the current plate is not directly exposed to the high-speed flow discharged from the impeller, there is less dust adhesion to the current plate and wear of the current plate, and the current plate prevents high-speed flow from being discharged. It has excellent effects such as no problems.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional single-suction type centrifugal blower, Fig. 2 is a cross-sectional view taken along line X-X' of the centrifugal blower in Fig. 1, and Fig. 3 is a cross-sectional view of the single-suction type centrifugal blower of the present invention. FIG. 4 is a sectional view of an embodiment of a centrifugal blower, and FIG. 4 is a Y-Y′ cross-sectional view of the centrifugal blower shown in _{FIG .} FIG. 6 is a characteristic diagram showing flow rate versus flow coefficient q, and FIGS. 7 and 8 are diagrams showing other embodiments of the centrifugal blower of the present invention, respectively. 1,1'...Centrifugal blower, 2...Casing,
3... Channel, 5... Scroll portion, 6, 7... Side plate, 11... Impeller, 12... Throat at the end of scroll winding, 13, 14, 15... Rectifier plate.

Claims (1)

[Claims for Utility Model Registration] (1) In a single-suction type centrifugal blower comprising a scroll-type casing with a substantially rectangular flow passage cross section, and having a space between an impeller and a side plate of the casing on the suction pipe side. , a rectifying plate is disposed in the flow path near the throat at the end of the scroll winding, parallel to the side plate, and near the discharge port of the impeller on the suction pipe side with respect to the impeller; A centrifugal blower characterized in that the flow path in a section near the throat is divided by a plane parallel to the side plate into a discharge side of the impeller and a space side on the suction pipe side. (2) The centrifugal blower according to claim 1, wherein the baffle plate is disposed straddling the end throat of the scroll.