JPH05312192A - Axial flow fan - Google Patents

Abstract

PURPOSE:To enlarge operation range of a axial flow fan on the small flow side without deterioration of efficiency by providing a plurality of subsidiary blades of which height is lower than that of moving blades on side walls just behind the lower stream of the moving blades 2. CONSTITUTION:A moving blade 2 is fixed to a rotary shaft 1 and rotated. A stationary blade 3 is fixed on either or both of outside side wall 8 and/or inside side wall 9, and a large rate of received kinetic energy is converted to pressure by it. At this time, at the outlet of moving blade 2, the flow in the vicinity of the side walls 8,9, has less kinetic energy than a part apart from the side walls, but air speed in the circumferential direction is relatively high even just before generation of stall by action of the moving blade 2. Therefore, the flow of relative high speed in the circumferential direction is scooped with a plurality of subsidiary blades of which height are lower than that of the moving blade 2 and led toward the inlet angle of the stationary blade 3. Flow in the vicinty of the outlet of the moving blade 2 and in the vicinity of side walls 8,9 of the stationary blade 3 is increased by this action so as to restrain generation of stall. Further this effect is improved by approaching the inlet angle of the subsidiary blade 6 in parallel direction with the plane of rotation compared with the inlet angle of the stationary blade 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial fan that is frequently used for ventilation and air blowing.

[0002]

2. Description of the Related Art As a method for expanding the operating range on the low flow side of an axial fan, which is widely used for ventilation and ventilation, B. Eck's "Vuenchila Torren" Funften Neubeer Baitete Auflage Springer-Ferlag (B.Eck)
Written "Ventilatoren" Fuenftenneubearbeitete Auflag
e Splinger-Verlag 1972), page 318, FIG. 298 shows (1) a method in which the side wall at the tip end side of the moving blade inlet is enlarged outward and a circular ring is inserted in the enlarged portion to form a reflux flow path.
(2) A method of arranging a cylinder concentric with the rotating shaft of the moving blade on the tip side of the moving blade inlet. (3) It is stated that three effects of the method of disposing the stationary annular blade row inside the cylinder of (2) are large.

[0003]

Among the above-mentioned prior arts, (1) is accompanied by a decrease in maximum efficiency, while (2) and (3) are both complicated in structure, resulting in an increase in manufacturing cost and a decrease in reliability. Was unavoidable. It is an object of the present invention to realize an operation range expansion on the low flow rate side of an axial flow fan without causing a decrease in efficiency.

[0004]

In order to solve the above problems, the present invention provides a plurality of auxiliary blades having a height lower than that of the moving blades on the side walls immediately upstream and downstream of the moving blades. The auxiliary vane on the outer side wall immediately before the upstream of the moving blade is provided so as to have a pre-swirl in the rotational direction in the flow, and the auxiliary vane on the inner side wall is
It is provided so as to guide the flow in the axial direction. Immediately after the moving blade, the auxiliary blade is provided so as to guide the flow in the direction of the inlet angle of the stationary blade, and the inlet angle of the auxiliary blade is from the inlet angle of the stationary blade or the inlet angle of the stationary blade. Bring it closer to the direction parallel to the plane of rotation of the rotor blade.

[0005]

[Function] In many cases, the axial flow fan, which is often used for ventilation and ventilation, reduces the flow rate from the design point. When the flow rate exceeds a certain limit value, the blades stall and a large decrease in pressure rise and unstable phenomena occur. This causes generation and further large-scale backflow, which makes normal operation impossible. For this reason, a plurality of auxiliary blades, which are lower in height than the rotor blades, are installed on the side wall immediately downstream of the rotor blades so as to guide the flow in the direction of the stator blade inlet angle, and the flow inside the rotor blades is scooped from the downstream side. Prevent stall by. In addition, a plurality of low-profile auxiliary blades are provided on the side wall immediately upstream of the moving blade so that the flow has a pre-swirl in the rotation direction on the outer side wall, and the flow flows into the moving blade from the direction of the rotation axis on the inner side. Thus, the load on the tip side of the moving blade is reduced to prevent stall on the tip side of the moving blade. on the other hand,
At the root side of the moving blade, the moving blade surely gives kinetic energy to the flow to prevent stall at the root side of the moving blade. In this way, the stall of the axial fan is prevented and the operating range on the low flow rate side is expanded.

[0006]

FIG. 1 shows the first embodiment of the present invention.
1 shows a cross section including the axis of rotation of an axial fan. In FIG.
The moving blade 2 is fixed to the rotating shaft 1 and moves. The vane 3 is fixed to one or both of the outer side wall 8 and the inner side wall 9. As the flow 7 passes through the rotor blade 2, it receives kinetic energy, and when it passes through the stationary blade 3, a large proportion of the received kinetic energy is converted into pressure. On the inner and outer side walls 8 and 9 immediately downstream of the moving blade 2, a plurality of auxiliary blades 6 having a height lower than that of the moving blade 2 are provided so as to guide the flow in the direction of the stationary blade inlet angle as shown in FIG. The operation of the auxiliary wing 6 will be described below with reference to FIGS.

Generally, in an axial fan, as shown in FIG. 3, when the flow rate is decreased from the design point, the pressure rise reaches a maximum value at the flow rate C, and then, as shown by a curve B, once decreases. To increase again. In the state where the pressure rise increases from the decrease again, as shown in FIG. 4, a large-scale backflow region 10 is generated at the blade inlet tip side. Further, in some cases, a large-scale backflow region 11 is also generated on the root side of the moving blade outlet. The state in which the pressure rise is once reduced varies greatly from the state in which the flow is normal and no large-scale backflow occurs to the transition state shown in FIG. When the flow rate is smaller than the flow rate C, the tip side and the root side of the moving blade are in a stalled state. When the occurrence of the stalling is suppressed, the relationship between the flow rate and the pressure rise is as shown in A of FIG. 3, and the operation limit on the low flow rate side is C. To D
Expand to.

Since the flow in the gap between the tip side of the moving blade 2 and the side wall 8 cannot receive kinetic energy from the moving blade 2, the flow in the vicinity of the outer side wall 8 out of the flow flowing out of the moving blade 2 is the moving blade 2.
The stall is more likely to occur than the central portion in the height direction. The vane 3 is often attached to the outer sidewall 8. In this case, in the flow in the gap between the stationary blade 3 and the inner side wall 9, the rate of pressure increase due to the action of the stationary blade 3 is smaller than that in the central portion of the stationary blade 3, so that the load increases at the root of the moving blade 2 and stalls. Is likely to occur. Further, in the case of the axial flow fan, the axial distance between the moving blade 2 and the stationary blade 3 is extremely larger than that of the axial flow compressor in order to reduce noise. For this reason, the flow near the inner and outer side walls 8 and 9 of the flow flowing out of the moving blade 2 loses kinetic energy due to friction with the side wall before flowing into the stationary blade 3, so that the center of the stationary blade 3 in the height direction is reduced. The stall is more likely to occur as compared with the part of. At the design point, this tendency is suppressed because the axial component of the flow is large, but when the flow rate decreases, this tendency becomes stronger and stall occurs.

At the outlet of the rotor blade 2, the flow near the side walls 8 and 9 has less kinetic energy than the portion away from the side walls 8 and 9, but the action of the rotor blade 2 causes a stall in the circumferential velocity. It is relatively large even in the previous state. Therefore, the auxiliary wing 6 scoops out the flow having a relatively large circumferential velocity,
It is guided in the direction of the inlet angle of the stationary blade 3. By this action, the moving blade 2
Since the flow rate near the outlet of the nozzle and the vicinity of the side walls 8 and 9 inside and outside the stationary blade 3 increases, stall is suppressed from occurring. If the angle on the inlet side of the auxiliary blade 6 is closer to the direction parallel to the rotating surface of the rotor blade 2 than the angle of the stationary blade inlet as shown by the broken line in FIG. 2, the flow is scooped. The action becomes stronger and the stall is less likely to occur.

When the angle on the inlet side of the auxiliary blade is set to be close to the direction parallel to the rotating surface of the moving blade 2, a slight loss increase may occur, but the loss increase can be reduced by the following. ..

Generally, the tip side and the root side of a moving blade do not start to stall at the same time, and either one of them starts to stall first. Taking the case where the tip side stalls first, the auxiliary blade inlet angle of the outer side wall 8 is made closer to the direction parallel to the rotating surface of the moving blade than the auxiliary blade inlet angle of the inner side wall 9. If the root side stalls first, do the opposite. In this way, the increase in loss can be reduced without impairing the stall prevention effect.

Further, a strong vortex flows out from the tip side of the moving blade 2 due to the gap with the outer side wall 8, and from the root side of the moving blade 2 by the action of the wall boundary layer on the root side of the moving blade 2. , Although weaker than the tip side, the vortex also flows out. The kinetic energy of these vortices becomes a loss, but the auxiliary vanes 6 and 6a cut and suppress the outflowing vortices to reduce the loss of kinetic energy. Therefore, the pressure is sufficiently increased at the tip side and the root side of the stationary blade 3. Be done. When the pressure is sufficiently increased, the load on the tip side and the root side of the moving blade 2 does not become excessive, and from this point also, the auxiliary blades 6 and 6a have an action of preventing stall.

Further, since the auxiliary blades 6 and 6a are provided in the direction of the flow in a substantially normal state, and the flow rate passing through the auxiliary blades 6 and 6a is a part of the whole, there is almost no decrease in efficiency. It is also a big feature that it does not exist.

FIG. 5 shows a second embodiment of the present invention. In order to further enhance the control of stall, moving blades are provided on the inner and outer side walls 8 and 9 immediately upstream of the moving blade 2 of the first embodiment. A plurality of lower auxiliary wings 5, 5a are provided on the outer side wall 8 so as to have a slight pre-swirl in the direction of rotation 4, as shown in FIG. It is provided to guide in the direction. The effect of the aileron 5 on the outer side wall 8 is as follows.

At the tip of the moving blade, the flow flowing into the moving blade 2 due to the action of the auxiliary blade 5 has a pre-swirl in the rotation direction 4. For this reason, the relative inflow angle of the moving blade 2 is reduced, and it is difficult for the blade to stall. The operation of the auxiliary blade 5a on the inner side wall 9 is as follows.

Since the peripheral speed on the root side of the moving blade is smaller than that on the tip side, the action of giving kinetic energy to the flow is weaker than that on the tip side. Therefore, the warping of the airfoil is increased to compensate for the weakened action. There is. On the other hand, when the flow rate is small, the pressure rise in the fan is large as shown in Fig. 3, and the pressure at the fan outlet (stationary vane outlet) cannot reach the pressure on the root side of the moving blade compared to the tip side, and there is a strong tendency to stall. Become. In this state, when the pre-swirl in the rotation direction 4 occurs near the root of the blade due to the shape of the flow passage on the upstream side of the fan, the flow droop, the nonuniformity, etc., there is a tendency for the flow to stall due to a decrease in kinetic energy received from the blade 2. The increase exceeds the stall suppression effect due to the decrease in the relative inflow angle, and stall occurs. The plurality of auxiliary blades 5a provided on the inner side wall 9 ensure that the flow is from the direction of the rotation axis to the moving blades 2a.
Since the pre-swirl in the rotational direction 4 does not occur at the rotor blade root side inlet, the stall that occurs due to the above mechanism is suppressed.

FIG. 7 is a diagram showing a third embodiment of the present invention.
The auxiliary blade 6 is provided only on the outer side wall 8 immediately downstream of the moving blade. The feature of this embodiment is that the effect of expanding the operating range is slightly reduced, but the structure is simple.

FIG. 8 and FIG. 9 are views showing the arrangement of the auxiliary blade 6 arranged on the side wall immediately downstream of the moving blade on the cylindrical development surface corresponding to FIG. The embodiment shown in FIG. 8 is suitable when the number of the auxiliary blades 6 is larger than that of the stationary blades 3 to enhance the action of the auxiliary blades 6 as a blade row. Similarly, it is also effective to increase the number of auxiliary blades 5 arranged on the side wall immediately upstream of the moving blades more than that of the moving blades 2 or the stationary blades 3. The embodiment of FIG. 9 is suitable when the auxiliary blade 6 is integrated with the stationary blade 3 and the strength is emphasized.

10 and 11 are sectional views of an axial flow fan corresponding to FIG. 1 in still another embodiment. FIG. 10 shows the effect of increasing the height of the ends of the auxiliary blades 5, 5a, 6 close to the moving blade 2 to enhance the action of guiding the flow into or out of the moving blade 2. In this case, noise slightly increases due to interference between the moving blade 2 and the auxiliary blades 5 and 6. Figure 9
Is an embodiment of the aileron 6 for reducing the increase of noise,
Contrary to the embodiment of FIG. 10, the blade height on the side closer to the moving blade 2 is reduced.

[0020]

According to the present invention, it is possible to expand the operating range on the low flow rate side of the axial flow fan without lowering the efficiency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an axial fan according to the present invention.

FIG. 2 is a development view of a cylinder of a blade row of an axial flow fan of the present invention.

FIG. 3 is a flow rate pressure characteristic diagram of an axial flow fan.

FIG. 4 is a cross-sectional view showing a backflow inside the axial fan in a low flow rate region.

FIG. 5 is a cross-sectional view showing a second embodiment of the axial fan of the present invention.

FIG. 6 is a development view of a cylinder of a blade row of an axial fan according to a second embodiment of the present invention.

FIG. 7 is a sectional view showing a third embodiment of the axial fan of the present invention.

FIG. 8 is a development view of a cylinder of another embodiment of the blade cascade of the axial flow fan of the present invention.

FIG. 9 is a development view of a cylinder of another embodiment of the blade cascade of the axial flow fan of the present invention.

FIG. 10 is a sectional view showing a fifth embodiment of the axial flow fan of the present invention.

FIG. 11 is a sectional view showing a sixth embodiment of the axial fan of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotating shaft, 2 ... Moving blade, 3 ... Stationary blade, 5, 5a ... Auxiliary blade on the upstream side of a moving blade, 6 ... Auxiliary blade on the downstream side of a moving blade, 7 ... Flow, 8 ...
Outer side wall, 9 ... inner side wall.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Takada 603 Jinritsu-cho, Tsuchiura-shi, Ibaraki Prefecture Hiritsu Manufacturing Co., Ltd. Tsuchiura factory

Claims (1)

[Claims] 1. A plurality of auxiliary blades having a height lower than that of the moving blade are provided on one or both of the inner and outer side walls downstream of the moving blade so as to guide the flow in the direction of the inlet angle of the stationary blade. An axial flow fan characterized in that an inlet angle of the blade is closer to an inlet angle of the vane or a direction parallel to a rotating surface of the moving blade than an inlet angle of the vane.