JPH0470077B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an aeration device installed in a tank for storing wastewater, such as a sewage treatment plant, a pump well in a pump station, or an underground drainage tank in a building. [Prior Art] The aeration principle of this aeration device is an application of Bernoulli's theorem, and Bernoulli's theorem is expressed by equation (1). P/r+V ² /2g+Z=H (=constant)...(1
) P: Pressure at one point on the streamline V: Flow velocity Z: Height from the reference water surface (1) The first term in equation (1) represents pressure energy, the second term represents velocity energy, and the third term represents potential energy,
This shows that the sum of the three components is constant in fluid motion. This aeration device increases the velocity energy by increasing the flow velocity at the tip of the stirring blade, and as the potential energy is considered to be approximately constant, the pressure energy decreases and becomes negative pressure. This negative pressure allows for self-supply of air. As shown in FIG. 5, the negative pressure is greatest at the rotation center of the stirring blade and decreases as it moves away from the center. This indicates that the velocity at the center of rotation is the greatest, and that the water flow is radially diffused from the center. Here each number indicates mmAq. As this type of aeration device, Japanese Patent Application Laid-Open No. 62-68590
The one described in the above publication is publicly known. This aeration device is easy to install at the bottom of the tank, and has the advantage of sucking scum from the top of the draft tube and dispersing it with stirring blades. however,
Even with such an excellent device, in the embodiment in which the air outlet is provided on the wall of the draft tube, a sufficient flow velocity cannot be obtained in the vicinity of the air outlet, resulting in insufficient air supply. In order to obtain a sufficient flow velocity near the air outlet, if the stirring blade and the air outlet, ie, the draft tube, were placed close together, there was a risk that foreign matter would become clogged between them. The inventors solved this problem by changing the location of the air outlet of the air pipe from the wall of the draft tube to the notch at the center of rotation of the stirring blade, allowing the movement of contaminants between the draft tube and the stirring blade. The problem was solved by creating a space. However, even in this case, there is a risk that long fibrous contaminants such as pante yeast may become entangled in the air pipe. As shown in Figure 6, the entangled foreign matter is moved toward the center of the stirring blade as described above and the pressure is decreasing, so the fluid moves from the higher pressure side to the lower pressure side, that is, towards the center of the stirring blade. There was a risk that it would be pushed away by the force F and interfere with the stirring blade or block the air outlet. Furthermore, since the water flow caused by the stirring blades spreads radially from the center of rotation of the stirring blades, the speed decreases from the center of the stirring blades to the air pipe outlet, and the negative pressure tends to decrease accordingly. [Problems to be Solved by the Invention] The present invention prevents the above-mentioned impurities in wastewater from interfering with the stirring blades and blocking the air pipe outlet, and also increases the flow velocity at the position of the air pipe outlet. The purpose is to increase the negative pressure and improve the air supply capacity accordingly. [Means for Solving the Problems] The present invention was made to achieve the above object, and consists of an underwater motor, a drive shaft coupled to the underwater motor shaft, and a helical blade attached near the tip of the drive shaft. In an aeration device comprising a formed stirring blade, an air release port provided in a notch at the center of rotation of the stirring blade, and a draft tube surrounding the stirring blade, on the downstream side of the air release port, and The gist is that a disk having the same diameter or a slightly smaller diameter than the outer diameter of the stirring blade is provided near the tip of the stirring blade. [Operation] By providing the above member, even if foreign matter becomes entangled in the air pipe, the foreign matter will be blocked by the member and will not reach the stirring blades and the air outlet. Furthermore, when the aeration device is stopped, the member can prevent the intrusion of foreign substances in the wastewater flowing back toward the center of rotation of the stirring blade. In addition, in the past, the water flow spread radially from the center of rotation of the stirring blade to the fluid whose front was open, reducing the flow velocity, but by narrowing the discharge port with the above-mentioned member, it is possible to suppress diffusion as much as possible, increasing the flow velocity. can increase the negative pressure at the air pipe outlet position. [Example] Hereinafter, an example of the aeration device of the present invention will be described based on the drawings. In the figure, reference numeral 1 denotes a drainage tank provided at the lowest floor of a building to have a required volume, and an aeration device 3 is installed at a required position on the bottom 2 of this drainage tank 1. This aeration device 3 consists of a submersible motor 4, a stirring blade 5, a draft tube 6, and an air pipe 7. The draft tube 6 has an upper end 6a that expands in a truss shape,
The lower part 6b is bent into an L-shape along the bottom of the tank, and is integrated with the submersible motor 4. Inside the draft tube 6 is a drive shaft 9 connected to the shaft of the motor 4, and a spiral stirring blade 5 is attached to the tip of the drive shaft 9. The air pipe 7 has an air outlet 7a at its tip, and the air outlet 7a is installed so as to be located at the center of rotation of the stirring blade 5 and at the notch of the stirring blade 5. The upper end of the air pipe 7 is always open to the atmosphere even if the water level fluctuates, and serves as an intake port. Air pipe 7
extends downstream for a predetermined length from the notch of the stirring blade 5 along its center of rotation, and then extends within 300 degrees below the circumferential surface of the draft tube 6. By doing this, the air pipe 7
It is possible to remove foreign matter so that it does not get entangled with the air outlet 7.
It does not interfere with a. A cylindrical shaft cover 8 is fitted around the outer periphery of the drive shaft 9. This shaft cover 8 protrudes into the draft tube 6, and the tip of the shaft cover 8 is close to the position where the vane of the stirring blade 5 starts, that is, the starting end of the stirring blade 5. By covering the drive shaft 9 with the shaft cover 8, it is possible to prevent fibrous contaminants from becoming entangled with the rotating parts of the aeration device, particularly on the outer peripheral surface of the drive shaft. A blocking member 7b is attached near the air outlet 7a of the air pipe 7. FIG. 3 shows the details of the mounting position. The blocking member 7b is a disc-shaped plate, and its outer diameter d is the same as the outer diameter D of the screw. Further, the air release port 7a is located at the position where the vane of the stirring blade 5 ends, that is, at the notch inside the end of the stirring blade 5, but the blocking member 7b is located downstream of the end of the stirring blade 5, that is, at a predetermined distance l. separated from each other. This distance l is suitably 1 to 5 mm. The following table shows the results of an experiment comparing the effect of this example with the case where no blocking member is provided.

[Table] That is, according to this example, an air supply amount that was approximately 27% higher than that of the conventional method was secured, and there was no phenomenon in which entangled contaminants interfered with the stirring blade or blocked the air outlet. FIG. 4 is a drawing showing another embodiment. In this figure, the blocking member is constituted by a large-diameter pipe 7c instead of the disk 7b as shown in FIG. 3. According to this embodiment, in addition to preventing fibrous contaminants from getting entangled in the air outlet 7a as in the previous embodiment,
An air pipe 7 that crosses the water flow inside the draft tube 6
This makes it possible to prevent foreign matter from getting entangled in the container. Furthermore, although not shown, the blocking member may of course be a cone-shaped object.

[Brief explanation of the drawing]

Figure 1 is a front view showing one embodiment of the present invention, Figure 2 is a front view showing one embodiment of the present invention;
3 is a plan view of the same, FIG. 4 is a plan view showing another embodiment of the present invention, FIG. 5 is a negative pressure distribution diagram at the tip of the stirring blade, and FIG. 6 is a diagram of the air pipe. FIG. 3 is a diagram showing a state in which foreign matter is entangled. 4 is a submersible motor, 5 is a stirring blade, 6 is a draft tube, and 7 is an air pipe.

Claims (1)

[Claims] 1. An underwater motor, a drive shaft connected to the underwater motor shaft, an agitation blade formed by a spiral blade attached near the tip of the drive shaft, and a notch in the center of rotation of the agitation blade. In an aeration device equipped with an air release port and a draft tube surrounding a stirring blade, a draft tube having the same outer diameter as the stirring blade is installed downstream of the air release port and near the tip of the stirring blade. An aeration device characterized by being provided with a disk having a small diameter or a slightly small diameter.