JP2000257587A - Axial flow fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an efficiency of a jet fan by minimizing change of the flow direction of a first stage outlet, and providing the maximum level of a work allocation on the first stage, in the relation of the straightening direction between front and rear impellers, in a two stage axial flow fan for blowing wind in both front and rear directions called as a jet fan. SOLUTION: When an electric motor 2 is driven, impellers 1 attached to a shaft 3 is rotated, and thereby, a fluid (air) flows from an inlet of a silencer case 4. The flow-in fluid does not have a circumferential direction speed component in absolute velocity. The fluid flows toward blades 100 of an upstream side impeller 1, and flows out from the blades 100 by applying work. This flow-out fluid has a circumferential direction speed component in absolute velocity. In this time, in the case where two pipe shaped stays 9 are used on a shaft cross section between the impellers 1, in the fluid which flows out from the upstream side impeller 1, almost circumferential component of the absolute velocity is not reduced. When the fluid is entered into a downstream side impeller 1, there is almost notching the relative velocity serving the impeller 1 as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial blower called a jet fan, and more particularly to a flow rectifier between two impellers for the purpose of increasing the efficiency of a two-stage axial blower capable of blowing in both front and rear directions. The present invention relates to a method and an impeller cascade design method.

[0002]

2. Description of the Related Art An axial blower called a jet fan is used for ventilation of a road tunnel and is arranged on a ceiling of the tunnel. Therefore, in order to minimize maintenance, the structure is made simpler. Also, in general, the flow in the tunnel is not limited to being determined in one direction, so there is a structural limitation that a jet must be blown with the same performance in both directions.

FIG. 1 shows the structure of a two-stage jet fan that can blow air in both front and rear directions. Impeller 1 for jet fan
This is directly connected to the shaft 3 of the electric motor 2, and the electric motor 2 is attached to a cylindrical silencer casing 4 by a stay 5.
Has been fixed by. The impeller 1 has wings 100 that give work to the fluid (air in the case of a jet fan). The two-stage jet fan is provided with two impellers 1 before and after the electric motor 2.

[0004] An inner cylinder 6 for rectification is provided at the front and rear portions of the impeller, and is fixed to a silencer casing 4 by stays 7 and 8 like the electric motor 2.

In the conventional jet fan, the stays 5, 7, 8 for fixing the electric motor 2 and the inner cylinder 6 have a plate-like shape in the meridional plane in order to rectify the flow in the axial direction. Was. As a known example, there is a sectional view between two front and rear impellers of a two-stage jet fan capable of blowing air in both front and rear directions in FIG.

[0006] In this arrangement, in addition to supporting the motor, a stay for commutation is provided at an axial position between the two impellers to which the motor 2 is attached. If the jet fan blows out in only one direction, the work between the front and rear impellers can be efficiently performed by making the stay between the impellers an appropriate blade shape.

However, in the case of a jet fan that blows out a jet flow in both front and rear directions, it is necessary to be able to blow out the jet flow in both front and rear directions with the same performance. The shape of the stay between the vehicles must be a plate in the meridional plane direction as shown in the cross-sectional view between the impellers in FIG.

[0008]

When the stay 5 between the impellers for rectifying the flow as a stationary blade between the impellers is arranged in the meridional plane, the stay forcibly eliminates the circumferential component of the flow between the impellers. Due to the work, the work distribution of the front (first stage) impeller and the rear (second stage) impeller can be almost evenly distributed.
The overall workload has increased. However, it did not always improve in terms of efficiency. Therefore, it is conceivable to make a difference in the work distribution between the front and rear impellers when the total work amount is sufficient, that is, to increase the efficiency by appropriately reducing the work distribution of the subsequent (second stage) impeller. Was.

When the work distribution of the front and rear impellers is differentiated, the blades in the case where the work distribution of the conventional (first-stage) impeller and the rear (second-stage) impeller are substantially equalized. It was natural that the cascade of the car was not optimal. It has been considered that efficiency can be increased by appropriately distributing the work distribution according to the radial position of the wing 100.

[0010]

SUMMARY OF THE INVENTION The present invention provides a method for rectifying the flow between the front and rear impellers of a two-stage axial blower capable of blowing air in both front and rear directions called a jet fan.
A high efficiency of a two-stage jet fan capable of appropriately allocating the work of the front and rear impellers and blowing air in both front and rear directions is realized.

In addition, by appropriately performing the flow rectification method between the impellers, the work distribution between the front and rear impellers is appropriately performed, and the work distribution in the radial direction of the blades of the impellers is appropriately performed, so that the jet fan is further improved. Achieve high efficiency.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Comparing a two-stage jet fan according to the present invention shown in FIG. The structure of the stay between the impellers including the stay 5 fixing the casing 4 is a plate-like shape in the meridional plane in order to rectify the flow in the axial direction. It is the same for a jet fan.

As an embodiment of the present invention, FIG.
2 is a cross-sectional view of a two-stage jet fan that can blow air in both front and rear directions between two front and rear impellers.

A comparison of the sectional view between the impellers of FIG. 2 of Japanese Utility Model Laid-Open No. 7-8599 as an example of a conventional jet fan shows a conventional sectional view of the cross-sectional view between the impellers of FIG. The shape of the stay is plate-like in the meridional direction,
The shape of the stay 9 in FIG. 2 according to the embodiment of the present invention is a shape in which the electric motor 2 is supported by two pipes in the axial cross section.

When the electric motor 2 is rotated, the impeller 1 directly attached to the shaft 3 of the electric motor is rotated, so that fluid (air) flows from the inlet of the silencer case 4. The absolute velocity of the flowing fluid has no circumferential velocity component. This fluid is the blade 1 of the impeller 1 (a) on the upstream side.
Wing 100 of impeller 1 (a) flowing toward 00 (a)
(A) is given work and comes out. The absolute velocity of the emerging fluid generally has a circumferential component.

If the fluid coming out of the blade 100 (a) of the impeller 1 (a) is not reduced in the circumferential component of its absolute velocity, the fluid of the blade 100 (a) of the downstream impeller 1 (b) is not changed.
If it flows into (b), since the rotation speed (speed) of the impeller 1 (b) is the same as the rotation speed (speed) of the impeller 1 (a), the blade of the impeller 1 (b) of this flow The relative speed based on 100 (b) becomes 0, and the impeller 1 (b) wing 1
At 00 (b), no work is given.

In the case where a conventional plate-like stay in the meridional direction between the impellers is used, the wing 100 of the impeller 1 (a) is used.
Since the fluid coming out of (a) acts to reduce the circumferential component of its absolute velocity, this fluid is impeller 1 (b)
When entering the wing 100 (b) of the impeller 1 (b)
This fluid has a relative speed with reference to (b), and this fluid receives work from the blade 100 (b) of the impeller 1 (b).

According to the result of the experiment, when the conventional plate-shaped stay in the meridional direction between the impellers is used, the impeller 1 is used.
The distribution of the work given to the fluids of (a) and the impeller 1 (b) is approximately 50% each.

On the other hand, when two pipe-shaped stays 9 are used in the axial cross section of FIG. 2 between the impellers according to the embodiment of the present invention, the fluid coming out of the impeller 1 (a) has its absolute velocity. Is hardly reduced, and when this fluid enters the impeller 1 (b), there is almost no relative speed with respect to the impeller 1 (b).

According to the result of the experiment, when the pipe-shaped stay 9 between the impellers according to the embodiment of the present invention is used, the impeller 1 is used.
The distribution of the work given to the fluids of (a) (first stage impeller) and impeller 1 (b) (second stage impeller) is 95% and 5%, respectively.
%. The experimental results of the efficiency show that the pipe-shaped stay 9 between the impellers according to the embodiment of the present invention is 64% in the case of using the plate-like stay in the meridional direction between the conventional impellers.
Is 68%, the embodiment of the present invention can be more efficient than the conventional case. This is because the total work given to the fluid is smaller in the present embodiment than in the case of using the conventional plate-like stay, but in the present embodiment, the shaft power is smaller than the decrease in the work given to the fluid. Is considered to be large.

When two stays 9 are arranged in parallel as shown in FIG. 2, if the outer diameter of the stay 9 is small, vibration may be caused by rotation of the impeller. When such a case is conceivable, vibration can be suppressed by inclining the pipe-shaped stay 9 and inserting two wire ribs 12 as shown in FIGS. 6 (a) and 6 (b).

In this embodiment, the shape of the stay 9 is 2
Although it is a pipe-shaped book, it is not necessary to have this shape in the gist of the present invention, and the circumferential component of the absolute velocity of the flow between the two front and rear impellers is the flow immediately after emerging from the upstream impeller. The same effect can be obtained in any shape as long as the shape can be maintained close to the circumferential component of the absolute velocity.

FIG. 3 is a cross-sectional view of an impeller that supports the motor 2 with a wire 10 as thin as possible having sufficient strength to support the motor 2. FIG. 4 is a cross-sectional view of an impeller in which a plate-like stay 11 supporting the electric motor 2 is meshed so that a fluid can pass in a thickness direction of the plate. These FIGS. 3 and 4
2, the circumferential component of the absolute velocity of the flow between the two front and rear impellers is the circumferential component of the absolute velocity of the flow immediately after coming out of the upstream impeller, as in the embodiment of FIG. The same effect as in the above embodiment can be obtained by maintaining the state close to the above.

The efficiency is further improved by optimizing the airfoil in combination with the method of appropriately performing the work distribution of the two-stage impeller in the present invention. FIG. 5 shows blades 100 (a) of an impeller 1 (a) (first-stage impeller) when two pipe-shaped stays 9 are used in the axial section of FIG. 2 between the impellers of the embodiment of the present invention. )
And a graph of the radial distribution of the work performed by the blade 100 (b) of the impeller 1 (b) (second stage impeller).

Although the conventional wing has a substantially constant work from the root of the impeller to the tip of the wing, the work is distributed more toward the tip of the wing in accordance with the above embodiment, and the wing of the wing is increased. This is the result of an experiment in which the distribution of work at the base of the car was reduced. According to the results of this experiment, the efficiency was 73%, which is higher than that of using only the stay 9 between the impellers.

[0026]

According to the present invention, it is possible to manufacture a two-stage jet fan having an efficient reversible motor in the rotating direction and having low power consumption and capable of blowing air in both directions.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a two-stage jet fan capable of blowing air in both front and rear directions.

FIG. 2 is a cross-sectional view of a two-stage jet fan capable of blowing air in both front and rear directions according to an embodiment of the present invention, between two front and rear impellers.

FIG. 3 is a cross-sectional view of an impeller supporting a motor 2 with a thin wire 10;

FIG. 4 is a cross-sectional view of an impeller that supports the electric motor 2 with a stay 11 of a mesh plate.

FIG. 5 is a cross-sectional view between the impellers according to the embodiment of the present invention. FIG. 5 is a cross-sectional view of the shaft of FIG. 2 in which two pipe-shaped stays 9 are used. Graph of the radial distribution of work performed by the wings of the impeller.

6 (a) and 6 (b) are cross-sectional views of the stay 9 of FIG.
Right front view of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Impeller, 2 ... Electric motor, 3 ... Electric motor shaft, 4 ... Silencer casing, 5, 7, 8 ... Stay, 6 ... Inner cylinder, 9
... stay (pipe-shaped), 10 ... wire stay, 11 ... mesh plate stay, 12 ... wire rib, 100 ... wing.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Tanaka 603, Kandamachi, Tsuchiura-shi, Ibaraki F-term in Tsuchiura Plant, Hitachi Ltd. (Reference) 3H032 CA04 CA08 CA09 NA06

Claims (3)

[Claims] A rectifying direction between two impellers of a two-stage axial fan, which is a jet fan having a rotational direction reversible motor and capable of blowing air in both front and rear directions, minimizes the change in the flow direction at the outlet of the first stage. An axial flow fan characterized by maximizing the work distribution of the first stage impeller and the second stage impeller by limiting the work distribution to the first stage. 2. An axial flow fan according to claim 1, wherein the blade shape of said impeller is improved by increasing the work distribution at the blade tip and decreasing the work distribution at the blade root. An axial fan characterized by its design. 3. A reversible motor in the direction of rotation is provided between two impellers having a plurality of blades in a cylindrical casing,
By simultaneously rotating the two impellers with the electric motor, the jetting direction of the jet can be switched bidirectionally, and the electric motor is mounted on the casing with a small-diameter stay. An axial fan characterized by being reinforced with small-diameter stay wires to suppress vibration.