JPH07279896A - Axal flow fan - Google Patents

Abstract

PURPOSE:To prevent lowering of efficiency even at a high flow rate by preventing a rotor blade from stalling. CONSTITUTION:In an axial flow fan incorporating a circulating passage 5c outside of a passage extending the leading edges of variable angle inlet guide vanes to the leading edged of rotor blades, a closing plate 9 is driven by means (a small gear 7 and a rack 8) for associating variation in the angle of the inlet guide vanes 3 in accordance with a flow rate, so as to open and close the inlet of the rotor blade side leading edge part of the circulating passage 5c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an inlet guide vane whose angle can be changed on the upstream side of a rotor blade, and a circulation passage outside the passage from the front end portion of the rotor blade to the front end portion of the inlet guide blade. The present invention relates to an axial fan provided with.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view of a main part of a conventional axial flow fan. A rotor blade 2 is attached around the rotor 1, and an inlet guide vane 3 is provided in a main flow passage 5m between a casing 5 on the upstream side of the rotor blade 2 and a boss casing 5b so that an angle can be changed by a guide vane shaft 4. ing. From the front end of the rotor blade 2 to the inlet guide blade 3
A circulation flow path 5c is formed between the inner casing 5i and the outer casing 5o on the outer periphery up to the front end of the main flow path 5m at the front end of the moving blade 2 and the front end of the inlet guide vane 3 to the main flow path 5m. . A rectifying vane 6 is provided at the end of the circulation passage 5c on the front end side of the moving blade 2.

In FIG. 4, when the rotor 1 rotates the rotor blades 2, a main airflow flowing from left to right is generated in the main flow path 5m. The angle of the inlet guide vane 3 is changed and set by the guide vane shaft 4 according to the flow rate and the pressure difference, and operation is performed so that the maximum efficiency is obtained. When the axial fan has a large pressure difference and operates at a small flow rate, a stall phenomenon occurs from the tip of the moving blade 2 and the entire flow becomes unstable, so the air flow that tries to flow backward from the tip of the moving blade 2. Is spilled into the circulation flow path 5c and rectified and circulated by the rectification vanes 6 to prevent stall, and it is possible to operate with a stable flow even when the pressure difference is large and the flow rate is small.

[0004]

As described above, the conventional axial flow fan can be operated with a stable flow even when the pressure difference is large and the flow rate is small, but it is also possible when the flow rate is large and the pressure difference is small. , The circulation passage 5 from the tip of the rotor blade 2 by centrifugal force
There is a flow of air that escapes into c, which causes a problem that the efficiency is slightly reduced at a large flow rate.

The present invention has been made in order to solve the above problems, and an axial fan capable of preventing stalls and operating in a stable flow and having no decrease in efficiency even at a large flow rate is provided. The purpose is to get.

[0006]

The axial fan according to the present invention is driven by interlocking means interlocking with the change of the angle of the inlet guide vane corresponding to the large or small flow rate, and the circulating vane front end side of the circulating flow passage. The opening and closing plates are provided to close or open the respective entrances.

[0007]

The opening / closing plate of the axial fan according to the present invention is driven by the interlocking means interlocking with the change of the angle of the inlet guide vanes, and the inlet on the rotor blade front end side of the circulation passage corresponds to the large or small flow rate. Respectively closed or opened. Therefore, when the flow rate is small, the inlet of the circulation passage opens, and the stall is prevented from occurring due to the overpressured air flow escaping from the blade tip into the circulation passage, and the overall flow of the fluid is stable. You can drive. Further, when the flow rate is large, the inlet of the circulation flow passage is closed, and there is no wasted air flow escaping from the blade tip to the circulation flow passage, and there is no reduction in efficiency.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1A and 1B show an axial fan according to an embodiment of the present invention, wherein FIG. 1A is a semi-longitudinal sectional view, and FIG. 1B is a partial transverse sectional view of a circulation passage. In FIG. 1, 1 is a rotor, 2 is a moving blade, 3
Is an inlet guide vane, 4 is a guide vane axis, 5 is a casing, and 6 is a rectifying vane. The rotor 1 is rotationally driven by drive means such as an electric motor (not shown). The rotor blades 2 are attached to the outer periphery of the rotor 1 side by side at equal intervals. The inlet guide vane 3 is supported on the upstream side of the moving vane 2 by a guide vane shaft 4 supported by a casing 5, and the angle adjustment can be set by rotating the guide vane shaft 4. Moving blade 2 of casing 5
From the front end of the inlet guide vane 3 to the front end of the inlet guide vane 3 has a double structure of an inner casing 5i and an outer casing 5o, and a main flow path 5m is formed in the inner casing 5i between the inner casing 5i and the boss casing 5b. Has been done. At both ends of the inner casing 5i, holes are opened in the main passage 5m along the entire circumference, and a circulation passage 5c is formed between the inner casing 5i and the outer casing 5o. The rectifying vanes 6 are provided at the end of the circulation passage 5c on the rotor blade 2 side, and are formed in a shape that rectifies the swirling flow entering the circulation passage 5c into an axial flow.

In FIG. 1, a small gear 7 is attached to the guide vane shaft 4 and is rotatable with the guide vane shaft 4.
A rack 8 meshes with the small gear 7, and is provided so as to be movable in the axial direction. Reference numeral 9 denotes an opening / closing plate, which is attached to the moving blade 2 side of the rack 8 and formed in an annular band plate shape so as to move in the axial direction together with the rack 8 to open / close the moving blade 2 side opening of the circulation channel 5c. Has been done.

Next, the operation of the embodiment shown in FIG. 1 will be described. The rotor 1 is driven by a driving unit such as an electric motor (not shown).
When the rotor blade 2 is driven to rotate together with the rotor blade 2,
Drive the fluid inside to move from left to right in the figure. If the pressure difference between the fluids before and after the moving blade 2 is small, the flow rate is large, and if the pressure difference is large, the flow rate is small. When the pressure difference is small and the flow rate is large, the direction of the fluid flowing into 2 is set so that the inlet guide vanes 3 are oriented substantially parallel to the axial direction as shown in FIGS. 2 (A) and 3 (A). Is made to flow in a large amount in the axial direction, and when the pressure difference is large and the flow rate is small, as shown in FIGS. 2 (B) and 3 (B), the inlet guide vanes 3 are inclined at an angle from the axial direction. The flow is swirled to reduce the flow rate, but the force exerted on the fluid of the moving blade 2 is increased.

As shown in FIGS. 2B and 3B,
When the inlet guide vane 3 is inclined from the axial direction at a small flow rate, the rack 8 meshing with the small gear 7 fixed to the guide vane shaft 4 moves to the left in the figure and is fixed to the rack 8. The open / close plate 9 also moves to the left and reaches a position where the inlet of the circulation passage 5c on the moving blade 2 side can be opened. At this time, the hydrodynamic load on the moving blade 2 is large and stall occurs from the tip of the moving blade 2, but the inlet of the circulating passage 5c on the moving blade 2 side is opened. Since a part of the fluid escapes from the tip of the moving blade 2 into the circulation channel 5c by the centrifugal force, the moving blade 2
The fluid load of is reduced, backflow is eliminated, and stall is prevented. With respect to the fluid that has entered the circulation flow path 5c, the swirling motion is rectified by the rectifying vane 6 into an axial motion, and thus the fluid shown in FIG.
Cycle as shown by the arrow.

As shown in FIGS. 2 (A) and 3 (A),
When the inlet guide vane 3 becomes parallel to the axial direction at a large flow rate, the rack 8 meshing with the small gear 7 fixed to the guide vane shaft 4 moves to the right in the figure and is fixed to the rack 8. The opening / closing plate 9 also moves to the right and reaches a position where the inlet of the circulation passage 5c on the moving blade 2 side is closed. At this time, in the conventional axial fan in which the inlet of the circulation passage 5c is always open, the fluid that has escaped from the tip of the moving blade 2 by the centrifugal force enters the circulation passage 5c and circulates, resulting in a wasteful flow. However, in this axial fan, since the opening / closing plate 9 closes the inlet of the circulation passage 5c on the moving blade 2 side, there is no wasteful flow that enters the circulation passage 5c and circulates, and the opening / closing plate 9 An efficiency improvement of about 2% was obtained as compared with the conventional one having no.

In the above embodiment, the small gear 7 and the rack 8 are used as the interlocking means for driving the opening / closing plate 9. However, for example, a link mechanism for connecting the guide vane shaft 4 and the opening / closing plate 9 with a link. Alternatively, a means such as a cam mechanism for driving the opening / closing plate 9 by attaching a cam to the guide blade shaft 4 may be adopted.

[0014]

As described above, according to the present invention, the opening / closing plate interlocking with the change of the angle of the inlet guide vanes opens the inlet of the circulation passage to circulate the air flow at the tip of the moving blade at a small flow rate. By escaping into the passage, stall can be prevented and a stable flow can be achieved, and at the time of a large flow rate, the inlet of the circulation flow passage is closed, so there is no useless flow flowing into the circulation flow passage. An improvement in efficiency can be obtained compared to.

[Brief description of drawings]

FIG. 1 shows an axial fan according to an embodiment of the present invention,
(A) is a semi-longitudinal sectional view, and (B) is a partial transverse sectional view of the circulation channel.

FIG. 2 (A) of an axial fan according to an embodiment of the present invention.
Is a vertical cross-sectional view of a main part in a large flow rate state, and (B) is a vertical cross-sectional view of a main part in a small flow rate state.

FIG. 3 (A) of an axial fan according to an embodiment of the present invention.
FIG. 3B is a plan view of the circulation flow path in the high flow rate state, and FIG. 6B is a plan view of the circulation flow path in the low flow rate state.

FIG. 4 shows a conventional axial flow fan, (A) is a semi-longitudinal sectional view, and (B) is a partial transverse sectional view of a circulation passage.

[Explanation of symbols]

1: rotor, 2: moving blade, 3: inlet guide vane, 4: guide vane shaft, 5: casing, 5c: circulation flow path, 6: straightening vane, 7: small gear, 8: rack, 9: open / close plate.

Claims (1)

[Claims] 1. An axial flow fan in which a circulation flow path is provided outside a flow path from a front end portion of an inlet guide vane whose angle can be changed to a front end portion of a moving blade, the inlet corresponding to a large or small flow rate. An axial fan provided with an opening / closing plate which is driven by an interlocking device that interlocks with an angle change of a guide vane to close or open an inlet on the front end side of the moving vane of the circulation passage.