JPH08309384A - Screw type aerator - Google Patents

Abstract

PURPOSE: To provide a screw type aerator of high aeration performance and a simple structure and easy to manufacture. CONSTITUTION: One or a plurality of hellically-formed plate-shaped blades 4 are installed at the end of a hollow shaft 3 rotated by a driving motor and having an opening 3b formed at the end of the shaft, and the length of a bonding section 41 for bonding the blade 4 and the hollow shaft 3 is formed three times as much as the maximum height (hmax) of the blade or over, and the angle (α) formed by the bonding section 41 and the circumferential direction of the hollow shaft 3 is made constant and set in the range of 30 deg.-80 deg., while the ratio (d/Dmax) between the outer diameter (d) of the hollow shaft 3 and the maximum outer diameter (Dmax) of the blade 4 is set in the range of 0.20-0.55.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies air (oxygen) into wastewater by stirring the wastewater to generate a negative pressure,
More specifically, the present invention relates to a screw-type aerator that performs aeration, in which one or more spiral plate-shaped blades are provided at the tip of a hollow shaft that is rotated by a drive motor and has an opening at the shaft end. It relates to a screw type aerator.

[0002]

2. Description of the Related Art As a screw type aerator which is rotated by a drive motor and has a blade formed in a spiral shape at the tip of a hollow shaft having an opening at the shaft end, for example, Japanese Patent Publication No. 56-21452. The ones described are known.

In the case of this screw type aerator, as shown in FIGS. 10 and 11 (a) to (e), the pitch P of the blades P
Is smaller at the screw outlet (the angle (α) formed by the circumferential direction of the hollow shaft and the joint between the blade and the hollow shaft is smaller at the screw outlet).

By the way, when the angle (α) formed by the circumferential direction of the hollow shaft and the joint between the blade and the hollow shaft is made smaller toward the screw outlet, as shown in FIG. Absolute velocity (V) does not rise and a large negative pressure cannot be generated. Therefore, the amount of air supplied to the dirty water through the hollow shaft is small. Also,
Since the absolute velocity (V) of the water flow at the screw outlet does not rise, the agitation power of the waste water is small, and the water in which oxygen is dissolved cannot be sent deep and far into the aeration tank.

Further, in order to increase the absolute velocity (V) of the water flow at the screw outlet, it is necessary to increase the angle (α) formed by the joint between the blade and the hollow shaft and the circumferential direction of the hollow shaft. However, in this case, in the conventional screw type aerator, the angle (α) formed by the circumferential direction of the hollow shaft and the joint between the blade and the hollow shaft at the screw inlet is necessarily large. By the way, since there is no swirl component in the flow at the screw inlet, if the angle (α) formed by the circumferential direction of the hollow shaft and the joint between the blade and the hollow shaft at the screw inlet becomes large, There was a problem that the fluid loss becomes large.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the conventional screw type aerators described above, and provides a screw type aerator with high aeration performance, simple structure, and easy manufacture. To aim. Another object of the present invention is to provide a screw type aerator in which the fluid loss at the screw inlet is small.

[0007]

In order to achieve the above object, the present invention forms one or a plurality of spirals at the tip of a hollow shaft which is rotated by a drive motor and has an opening at the shaft end. In a screw type aerator provided with a plate-shaped blade, the length of the joint between the blade and the hollow shaft is set to three times or more of the maximum height (hmax) of the blade, and the circumferential direction of the joint and the hollow shaft is increased. The angle (α) formed by is set to a constant value in the range of 30 degrees to 80 degrees, and the ratio (d / Dmax) between the outer diameter (d) of the hollow shaft and the maximum outer diameter (Dmax) of the blade is 0. 20 ~
The point is that the range is set to 0.55.

In this case, it is desirable to form the outer diameter of the blade in the vicinity of the screw inlet portion smaller than that of the other portions.

[0009]

According to the screw type aerator of the present invention, the angle (α) formed by the joint between the blade and the hollow shaft and the circumferential direction of the hollow shaft
Since the screw has a constant structure, the screw structure is simple and easy to manufacture. Moreover, the angle (α) formed by the circumferential direction of the joint and the hollow shaft is set in the range of 30 to 80 degrees, and the hollow shaft is Since the ratio (d / Dmax) between the outer diameter (d) of the blade and the maximum outer diameter (Dmax) of the blade was set in the range of 0.20 to 0.55, the length of the joint between the blade and the hollow shaft was Coupled with the fact that the maximum height of the blades is 3 times or more, the absolute velocity of the water flow at the screw outlet is increased, a large negative pressure is generated, and a large amount of air is supplied into the wastewater through the hollow shaft. You can Further, since the absolute velocity of the water flow at the screw outlet is increased, the agitation power of the waste water is large, and the water in which oxygen is dissolved can be sent deep and far into the aeration tank.

Further, by forming the outer diameter of the blade in the vicinity of the screw inlet portion smaller than that of the other portion,
Fluid loss at the screw inlet can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The screw type aerator of the present invention will be described below with reference to the illustrated embodiments. 1 to 4 show a first embodiment of the screw type aerator of the present invention. This screw type aerator 1 is arranged in an aeration tank or the like of a sewage treatment plant, and is rotated by a drive motor 2 to provide one or a plurality of pieces at the tip of a hollow shaft 3 having an opening 3b at the shaft end. A screw 5 is configured by providing a plate-shaped blade 4 formed in a spiral shape.
An intake hole 3a is formed in the base end of the hollow shaft 3, and the drive motor 2 rotates the screw 5 in the dirty water via the hollow shaft 3 to generate a negative pressure in the dirty water in the front region of the screw 5. As a result, air is sucked from the intake hole 3a, and the sucked air is supplied into the dirty water from the opening 3b formed at the shaft end of the hollow shaft 3.

The screw 5 is constructed by welding three independent plate-shaped blades 4 bent by a press or the like to the hollow shaft 3 in a spiral shape without contacting each other at substantially equal intervals. In this case, the number of blades of the screw is not limited to three, and may be one or two or more, and the method of fixing the blade and the hollow shaft is not limited to welding. Any mechanical fixing method can be adopted.

In this case, in order to obtain a predetermined aeration performance, the length of the joint portion 41 of the blade 4 with the hollow shaft 3 (the blade 4
The total length of the joint portion from the base end portion 4a to the tip end portion 4b) of 3 times or more of the maximum height (hmax) of the blade 4,
The ratio (d / Dmax) between the outer diameter (d) of the hollow shaft 3 and the maximum outer diameter (Dmax) of the blade 4 is also clear from FIG. 6 showing the relationship between this ratio (d / Dmax) and the aeration performance. Like 0.20
The amount of air supplied is set to be in the range of 0.55 (0.44 in the present embodiment) ((d / Dmax) is less than 0.20, and supplied if it is greater than 0.55. The amount of water discharged is reduced, and the aeration performance decreases in any case. (In this figure, when the aeration performance is less than 0.8, it indicates a state where it cannot be used as a normal aerator.) In order to increase the strength of the screw 5, it is preferable that the amount of protrusion (t) of the tip 4b of the blade 4 from the opening 3b formed at the shaft end of the hollow shaft 3 be equal to the maximum height (hmax) of the blade 4. 5 times or less.

The angle (α) (hereinafter referred to as the angle (α)) formed by the joint portion 41 between the blade 4 and the hollow shaft 3 and the hollow shaft 3 is the angle (α) and the aeration performance. As is clear from FIG. 7, which shows the relationship of No. 3, it is necessary to set the range of 30 degrees to 80 degrees. In this figure, when the aeration performance is less than 0.8, it cannot be used as a normal aerator. The angle (β) formed by the outer edge 42 of the blade 4 and the circumferential direction of the hollow shaft 3 (hereinafter referred to as the angle (β)) increases the absolute velocity of the water flow at the screw outlet portion 5b, so It is desirable to configure so as to enlarge at 5b.

The angle (α) formed by the joint portion 41 of the blade 4 and the hollow shaft 3 and the hollow shaft in the circumferential direction is constant and is 30 ° to 8 °.
By setting the range to 0 degree, as compared with the case of the conventional screw type aerator shown in FIG. 5 (a), the fluid loss at the screw inlet portion is not increased, and FIG.
By increasing the absolute velocity (V) of the water flow at the screw outlet as shown in Fig. 5, a large negative pressure can be generated in the opening 3b formed at the shaft end of the hollow shaft 3 of the screw 5, and A large amount of air can be sent to.

By the way, if the angle (α) of the screw outlet portion 5b is increased in order to increase the absolute velocity of the water flow at the screw outlet portion 5b, the (angle (α)) of the screw inlet portion 5a also becomes larger and the screw inlet portion 5a becomes larger. The fluid loss in the portion 5a will increase. This will be described more specifically with reference to FIG. FIG. 8 shows a speed triangle when the angle (α) between the screw inlet portion 5a and the screw outlet portion 5b is set to 55 degrees. As is clear from this figure, the relative inflow angle of the screw inlet portion 5a is set to the angle (α).
In order to match with, the peripheral speed must be about 50% of the peripheral speed of the screw outlet portion 5b. Therefore, it is preferable to form the outer diameter of the blade 4 in the vicinity of the screw inlet portion 5a smaller than other portions as shown in the rotational projection view of the screw 5 shown in FIG. It is possible to reduce the fluid loss at.

When the screw 5 is rotated in the dirty water, the flow escaping in the radial direction of the screw 5 is reduced and the absolute velocity of the water flow at the screw outlet 5b is increased, so as shown in FIG. 2 (a). It is desirable that the outer edge 42 of the blade 4 is bent in the direction in which the hollow shaft 4 rotates in a cross section orthogonal to the hollow shaft 3.

FIG. 9 shows the second screw type aerator of the present invention.
An example will be described. In this embodiment, the blade 4 at the tip of the hollow shaft 3 is used.
The notch 3c is formed in the vicinity of the negative pressure surface side, so that the air can be sucked into the dirty water from the notch 3c and the air can be more smoothly supplied into the dirty water. The rest of the configuration of this embodiment is the same as that of the first embodiment of the screw type aerator of the present invention.

[0019]

According to the screw type aerator of the present invention,
The absolute velocity of the water flow at the screw outlet can be increased to generate a large negative pressure to supply a large amount of air into the wastewater through the hollow shaft. Since it is increased, the stirring power of sewage is large,
Since water in which oxygen is dissolved can be sent deep and far into the aeration tank, the aeration performance of the screw type aerator can be enhanced. Further, since the screw type aerator of the present invention has a simple screw structure and is easy to manufacture,
The manufacturing cost of the screw type aerator can be reduced.

Further, if the outer diameter of the blade in the vicinity of the screw inlet is made smaller than that of the other portion, in order to increase the absolute velocity of the water flow at the screw outlet, the blade is connected to the hollow shaft and the hollow portion. Even if the angle (α) formed by the circumferential direction of the shaft is set to be large, the fluid loss at the screw inlet can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a screw of a first embodiment of a screw type aerator of the present invention.

2 (a) is a sectional view taken along the line II of FIG. 1, and FIG. 2 (b) is the same II-.
It is a II sectional view.

FIG. 3 is a rotational projection view of a screw.

FIG. 4 is a view showing a screw type aerator of the present invention.

FIG. 5 is a diagram showing a relationship between a blade angle of a screw and a speed triangle.

FIG. 6 shows the outer diameter (d) of the hollow shaft and the maximum outer diameter (Dma) of the blade.
It is a figure which shows the ratio (d / Dmax) with x), and the relationship of aeration performance.

FIG. 7 is a diagram showing a relationship between an angle (α) and aeration performance.

FIG. 8 is a diagram showing a relationship between an angle (α) and a velocity triangle.

FIG. 9 (a) is a diagram showing a screw of a second embodiment of the screw type aerator of the present invention, and FIG. 9 (b) is its III-I.
It is a II sectional view.

10A is a diagram showing a screw of a conventional screw type aerator, and FIG. 10B is a sectional view taken along line VI-VI thereof.

FIG. 11 is a view showing a screw of a conventional screw type aerator.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Screw type aerator 2 Drive motor 3 Hollow shaft 3a Intake hole 3b Opening 3c Notch 4 Blade 4a Blade base end 4b Blade tip 41 Joint with blade hollow shaft 42 Blade outer edge 5 Screw 5a Screw Inlet 5b Screw outlet Dmax Maximum outer diameter of blade d Outer diameter of hollow shaft hmax Maximum height of blade t Maximum amount of protrusion of blade tip from opening of shaft end of hollow shaft α Joint of blade with hollow shaft Angle between the hollow shaft and the circumferential direction of the hollow shaft β Angle between the outer edge of the blade and the circumferential direction of the hollow shaft

Claims (2)

[Claims] 1. A screw type aerator in which one or a plurality of spiral plate-shaped blades are provided at the tip of a hollow shaft which is rotated by a drive motor and has an opening at the shaft end. The length of the joint between the hollow shaft and the hollow shaft is 3 times or more of the maximum height (hmax) of the blade, and the angle (α) formed by the circumferential direction between the joint and the hollow shaft is constant and 30 ° to 80 °. And the ratio (d / Dmax) of the outer diameter (d) of the hollow shaft and the maximum outer diameter (Dmax) of the blade is set to 0.20.
A screw type aerator characterized by being set in a range of 0.55. 2. The screw type aerator according to claim 1, wherein the outer diameter of the blade in the vicinity of the screw inlet is smaller than that of the other portion.