Fluid Filters

Abstract

A new fluid filter utilizing the flow of fluid is provided. [Solution] The fluid filter includes side walls 10, 12 that form a flow path, and a separation wall 11 formed therebetween. A turbulence generating mechanism 14 is provided in a portion of the region extending from the end of the separation wall 11 to the side wall 10, and the turbulent region becomes a filter region 24 that filters only particles of a predetermined size or smaller. The fluid flows from upstream through the flow path between the side walls 10, 12 as F1, and becomes F2 that passes through the filter region 24 and F3 that remains. Large particles PL mixed in the fluid are pushed back by the turbulent flow and cannot pass through the filter region 24, but small particles PS are subjected to a force from the flow that is greater than the force due to the turbulent flow, and can pass through the filter region 24. By utilizing turbulence in this way, a filtering effect can be obtained without using a filter material such as a mesh, and the filtering effect can be adjusted by controlling the intensity of the turbulence.

Description

[Technical field]

[0001] The present invention relates to a fluid filter for removing particles from a fluid. [Background technology]

[0002] Conventionally, fluid filters that separate, remove, or filter particles of a specific size contained in a fluid use filtering materials such as metal mesh, filter cloth, laminated nonwoven fabric, etc. However, these filters have problems such as clogging, the size of particles that can be separated by the filter is fixed, and there is a limit to the fineness of particles that can be separated, so a filter based on a new principle has been desired. On the other hand, although it is not a filter itself, attempts have been made to remove very fine particles by utilizing the flow of a fluid. For example, Patent Document 1 discloses a technique in which clean air is made to flow over the surface of a semiconductor wafer, forming a laminar boundary layer and a turbulent boundary layer, thereby preventing suspended fine particles from falling onto the semiconductor substrate. Patent Document 2 discloses a technique in which, in a semiconductor wafer cleaning process, a supercritical fluid is made to flow over the surface of the wafer, creating a turbulent flow state to separate contaminants from the wafer, and then creating a laminar flow state to transport the contaminants downstream. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-190894 A [Patent Document 2] JP 2003-229397 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention takes into consideration the problems with conventional filters and the state of the art regarding the use of fluids, and aims to provide a new fluid filter that utilizes the flow of a fluid. [Means for solving the problem]

[0005] The present invention relates to A fluid filter for filtering particles in a fluid, comprising: a first flow path portion through which the fluid containing the particles flows; a turbulence generating mechanism that generates turbulence in the fluid in a filter region at an end of the first flow path portion; The fluid filter may further include a second flow path portion through which the fluid that has passed through the filter region flows.

[0006] The inventors discovered that when an interface where turbulence strength changes exists in a flow, a phenomenon occurs in which particles in the fluid are separated into those that pass through the interface and those that do not, that is, a filter effect occurs. According to the present invention, turbulence is generated in the filter region, and the above-mentioned interface can be intentionally generated in the flow, making it possible to function as a filter that filters particles in the fluid.

[0007] The fluid in the present invention may be any of various viscous fluids such as water, seawater, oil, air, gas, liquid crystal, plasma, ionic fluid, dielectric fluid, fluid metal, etc. A mixture of multiple types of fluids may also be used. In the present invention, the shape, dimensions, etc. of the filter region can be determined arbitrarily.

[0008] In the present invention, various mechanisms for generating turbulence can be used. The fluid may be agitated by a propeller. For example, in the filter region, turbulence may be generated by applying a voltage in a direction perpendicular to the flow to induce liquid crystal electroconvection. The fluid may also be agitated by opposed propellers, rotors, etc. The number, arrangement, and direction of the rotating shaft of the opposed propellers, etc. may be determined arbitrarily. The fluid may be agitated by a mechanism for injecting the fluid onto the filter region. The arrangement and number of the injection ports for injecting the fluid may be determined arbitrarily. A jacuzzi, i.e., a mechanism for spraying bubbles, may be provided in the filter area. In this case, too, the arrangement and number of the spray nozzles may be determined arbitrarily. The filter region may be heated to generate turbulence through thermal convection. When a charged fluid such as an ionic fluid is used, an AC or DC voltage may be applied to the filter flow area. An ion beam, an electron beam, or the like may be irradiated. A mechanism for generating wave motion may be provided in the filter region. Turbulence may be generated by flowing through a pipe.

[0009] In the present invention, The fluid in the first flow path portion may flow in a laminar manner.

[0010] The interface of the filter region refers to a surface where the turbulence strength changes suddenly to some extent, and is not necessarily limited to a case where the flow changes from laminar to turbulent. For example, a sufficiently stronger turbulence may be generated in response to a weak turbulence. However, according to the above embodiment, since the flow is laminar on the upstream side, the turbulence intensity at the interface acts effectively, and there is an advantage that the filter effect of the present invention can be effectively obtained. To make the flow laminar on the upstream side, various methods such as a flow straightening plate can be used.

[0011] In the present invention, further, The fluid supply device may further include a third flow path portion for allowing a fluid that does not pass through the filter region to flow.

[0012] This makes it possible to effectively carry out particles and the like that do not pass through the filter region. However, the present invention does not exclude a configuration that does not include the third flow path part. For example, all of the fluid that has flowed from the first flow path part may flow into the filter region.

[0013] In the present invention, The turbulence generating mechanism may be a mechanism capable of adjusting the turbulence intensity.

[0014] In this way, the size of particles that can be filtered in the filter region, i.e., the filtering performance, can be changed. Generally, filters using a filtering material such as a mesh have a fixed filtering performance, but according to the present invention, the filtering performance can be made variable, which greatly improves the usefulness of the fluid filter. As described above, various mechanisms can be applied as the turbulence generating mechanism, and the method for adjusting the turbulence intensity can also be a method according to the type of mechanism applied.

[0015] When adjusting the turbulence intensity in this way, The filter may further include a control unit for controlling the turbulence generating mechanism so as to provide a turbulence intensity determined according to the size of particles to be passed through the filter region.

[0016] In this way, the filtering effect can be controlled to filter particles of a desired size. In this case, various control methods can be used. For example, the turbulence intensity may be analytically calculated based on an equation that determines the size of particles that are allowed to pass through the filter region, and control may be performed to realize this. Also, a map or table showing the relationship between the size of particles to be passed through the filter region and the turbulence intensity may be prepared in advance, and the turbulence intensity may be controlled based on this. Furthermore, the average particle size after passing through the filter region may be measured, and the turbulence intensity may be controlled by feedback control so that this is a desired size. In addition, various other methods can be adopted.

[0017] The various features of the present invention described above do not necessarily have to be provided in their entirety, and some of them may be omitted or combined as appropriate. The present invention may also be configured as a filtering method for filtering particles in a fluid, in addition to a fluid filter. Furthermore, the present invention may be configured in various forms, such as a control method for controlling turbulence intensity, and a computer program for implementing such control by a computer. [Brief description of the drawings]

[0018] [Figure 1] 1 is an explanatory diagram illustrating a schematic structure of a fluid filter according to an embodiment of the present invention; [Diagram 2] FIG. 1 is an explanatory diagram showing how large particles cannot pass through an interface. [Diagram 3] FIG. 1 is an explanatory diagram showing how small particles pass through an interface. [Figure 4] FIG. 11 is an explanatory diagram showing the relationship between turbulence intensity and filter effect. [Diagram 5] 13 is a flowchart of a turbulent flow control process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Examples of the present invention will now be described. FIG. 1 is an explanatory diagram that illustrates a schematic structure of a fluid filter according to an embodiment of the present invention. A plan view is shown in Fig. 1(a). The fluid filter of the embodiment includes side walls 10 and 12 that form a flow path, and a separation wall 11 formed therebetween. A turbulence generating mechanism 14 for generating turbulence is provided in a portion of the region extending from the end of the separation wall 11 to the side wall 10. The region in which turbulence is generated by the turbulence generating mechanism 14 becomes a filter region 24, which exerts a filtering effect of filtering out only particles of a predetermined size or smaller.

[0020] The fluid flows from upstream as indicated by F1 through the flow path between the side walls 10 and 12. The portion of the flow F1 up to the filter region 24, i.e., the portion colored light gray in the figure, becomes the first flow path portion 21. A part of the flow F1 passes through the filter region 24 and flows, like the flow F2, in the second flow path section 22 that is composed of the side wall 10 and the separation wall 11. The remaining part does not pass through the filter region 24, but flows, like the flow F3, in the third flow path section 23 that is composed of the side wall 12 and the separation wall 11.

[0021] The fluid contains particles of various sizes. In the example shown in the figure, small particles PS that can pass through the filter region 24 and large particles PL that cannot pass through the filter region 24 are shown, but the fluid may contain particles of other sizes. In the first flow path section 21, the particles PS and PL are mixed, but because the filter effect prevents the particles PL from passing through the filter region 24, only the particles PS are mixed in the second flow path section 22. Meanwhile, the particles PL that cannot pass through the filter region 24 flow into the third flow path section 23. Note that, because the fluid that does not pass through the filter region 24 also flows in the third flow path section 23, small particles PS are also mixed in.

[0022] FIG. 1(b) shows a schematic cross-sectional structure of a portion where the turbulence generating mechanism 14 is provided. The turbulence generating mechanism 14 can have various configurations, but in the embodiment, a mechanism is applied in which a voltage is applied in a direction perpendicular to the flow in the filter region 24 to generate liquid crystal electrical convection to generate turbulence. Therefore, electrodes 14U and 14L are provided on the upper and lower surfaces of the flow path in the filter region 24. By applying a voltage between these electrodes, the above-mentioned convection occurs, generating turbulence. The turbulence intensity can be adjusted by controlling the voltage between the electrodes 14U and 14L. In the figure, the occurrence of turbulent flow is shown by arrows as numerous vortexes, but this is merely a schematic diagram, and the turbulent flow in the present invention is not necessarily limited to such vortex flows.

[0023] The turbulence generating mechanism 14 of the embodiment is a mechanism capable of adjusting the turbulence intensity, so the fluid filter of the embodiment is provided with a control device 15 that controls the turbulence generating mechanism 14. When the control device 15 receives a required value for the size of particles to be passed through the filter region 24, it calculates the turbulence intensity for achieving this filter effect and accordingly controls the turbulence generating mechanism 14. The control device 15 may be configured as hardware such as an ASIC, but may also be configured as software by installing a computer program for achieving the above-mentioned control functions in a computer equipped with a CPU and memory.

[0024] 1(a), in this embodiment, the filter region 24 is provided at an angle A with respect to the side wall 10. This has the advantage that the particles PL that cannot pass through the filter region 24 tend to flow along the filter region 24 into the third flow path portion 23. The angle A can be determined arbitrarily. It is also possible to set A=90 degrees, that is, to make the filter region perpendicular to the side wall 10.

[0025] 1(a), the third flow path section 23 may be omitted. In this case, particles PL that cannot pass through the filter region 24 will accumulate in the first flow path section 21, and it is therefore preferable to remove these particles at an appropriate timing or by an appropriate method.

[0026] In the fluid filter of the embodiment, the flow F1 in the first flow path section 21 may be a turbulent flow. This is because if the turbulence intensity generated in the filter region 24 is stronger than the turbulence of the flow F1, a filtering effect can be obtained at the interface of the filter region 24. However, in order to effectively obtain the filtering effect, it is preferable that the flow F1 is a laminar flow. From this viewpoint, the first flow path section 21 may be provided with a mechanism for laminarizing the flow F1, such as a straightening plate.

[0027] Fig. 2 is an explanatory diagram showing how large particles cannot pass through the interface. Fig. 2(a) to Fig. 2(c) show the state over time when a fluid containing particles of various sizes is passed through the filter region in a state where turbulence is generated in the filter region by liquid crystal electroconvection. In each photograph, the dark gray area in the upper right corner is the filter area 24. Below that is the flow F1 upstream of the filter area 24. 2(a), it can be seen that a relatively large particle PL1 approaches the filter region 24. Then, in FIG. 2(b) at the next time, it can be seen that the particle PL1 contacts the interface of the filter region 24. Looking at FIG. 2(c) at the next time, it can be seen that the particle PL1 moves along the interface of the filter region 24 and does not enter the inside of the filter region 24. In other words, it can be confirmed that such a large particle PL1 is filtered by the filter region 24. 2(c), it is confirmed that the particles PS1, which are relatively small in size, have entered the inside of the filter region 24. These particles pass through the filter region 24 and flow out downstream.

[0028] 3 is an explanatory diagram showing how small particles pass through an interface, shown in the order of FIG. 3(a) to FIG. 3(c) over time. In each photograph, the dark gray area at the bottom left is the filter area 24. The area to the upper right is the flow F2 after passing through the filter area 24. In Fig. 3(a), it can be seen that a relatively small particle PS2 is approaching the interface from inside the filter region 24. Then, in Fig. 3(b) at the next time, it can be seen that the particle PS2 is about to leave the interface. Looking at Fig. 3(c) at the next time, it can be seen that the particle PS2 has left the interface of the filter region 24 and is flowing downstream. In other words, it can be seen that such a small particle PS2 can pass through the filter region 24.

[0029] In this way, it has been experimentally confirmed that the fluid filter of the embodiment exhibits a filtering effect by generating turbulence in the filter region 24. This filtering effect depends on the strength of the turbulence.

[0030] FIG. 4 is an explanatory diagram showing the relationship between turbulence intensity and the filter effect. 4(a) shows the relationship between particle size and the percentage of particles filtered through the filter region 24 under the condition of turbulence intensity ε=35. The turbulence intensity ε is defined as follows.

number

[0031] Figure 4(b) shows the relationship between P and turbulence intensity. block The results for turbulence intensities ε = 24, 15, and 8 are given by curves C2, C3, and C4, respectively. Curves C2 to C4 show that when the particle size reaches a certain value, the P block increases sharply, qualitatively showing the same trend as curve C1. In addition, as the turbulence intensity ε decreases, the filterable particle size (P block It can be seen that the particle diameter φc) when = 0.5 is larger.

[0032] Figure 4(c) shows the relationship between the turbulence intensity ε and the filterable particle diameter φc, based on Figure 4(b). As shown in the figure, it can be seen that as the turbulence intensity ε increases, the filterable particle diameter φc decreases. In other words, it can be said that the fluid filter of the embodiment can change its filtering effect by changing the turbulence intensity.

[0033] In this embodiment, the theory behind the filter effect has not been completely elucidated, but it is believed to be due to the magnitude relationship between the Stokes effect and the Reynolds stress acting on the particles, as will be described below. The force F acting on a particle in a fluid is given by:

number

[0034] Where: μ: viscosity coefficient a: radius of particle U: Average flow velocity of the fluid u: particle flow velocity u x : Fluid velocity fluctuation component ρ: Fluid density It is.

[0035] The first term on the right-hand side of the above equation represents the Stokes drag, i.e., the force that the fluid exerts on the particle in the direction of the flow velocity. The second term on the right-hand side represents the Reynolds stress, i.e., the force that acts to push the particle away from the interface due to the velocity gradient at the interface in turbulent flow. Therefore, if the particle diameter is such that Stokes drag > Reynolds stress, the particle will enter the filter area. Conversely, if the particle diameter is such that Stokes drag < Reynolds stress, the particle will be filtered out in the filter area. The particle diameter at which Stokes drag = Reynolds stress is the threshold φc that separates the two. While the Stokes drag is proportional to the first power of the particle radius a, the Reynolds stress is proportional to the third power of the particle radius a, so it can be seen that the Reynolds stress tends to increase rapidly as the particle diameter increases. Also, since the Reynolds stress increases as the turbulence intensity increases, it can be seen that the particle radius equivalent to the threshold value tends to become smaller. From this, it can be said that the above equation matches the tendency shown in Figure 4.

[0036] Next, find the particle radius φc that is the threshold in the above equation. For this particle, if we consider that the Stokes force and the Reynolds stress are balanced at the interface, then F = 0. As a result, the particle velocity u = 0. Finding the particle radius φc under this condition gives the following equation.

number

[0037] In other words, it is clear that the threshold particle radius φc depends on the flow velocity U and the intensity of turbulence. Conversely, if the threshold particle radius φc that passes through the filter region is given as a required value, a relational expression between the flow velocity U and the intensity of turbulence that satisfies that value can be obtained.

[0038] Finally, based on the above, a control process in which the control device 15 (see FIG. 1) controls the turbulence generating mechanism 14 in the fluid filter of the embodiment will be described. 5 is a flowchart of the turbulence control process. When the fluid filter is operated, this control process starts.

[0039] When the process starts, the control device 15 inputs the required value of the particle diameter to be filtered (step S10). Here, the operator inputs the particle radius φc described above. The input can be performed in various ways. A keyboard or the like may be used to input the numerical value, or a graphic user interface may be used to indicate the particle size. A mechanical input device such as a dial may also be used.

[0040] When the required value of the particle radius φc is input, the control device 15 sets the turbulence intensity based on the required value (step S11). For example, it may be analytically set based on the formula shown in Equation 2. Also, a map or table such as that shown in FIG. 4(c) may be stored in advance, and the turbulence intensity may be set by referring to this. Then, the control device 15 controls the turbulence generating mechanism so as to realize the set turbulence intensity (step S12).

[0041] By executing the above process until completion, a filter effect according to the required value can be realized. Note that the filter effect may be adjusted by changing the required value in step S10 while the fluid filter is in operation.

[0042] The turbulent flow control process described in Fig. 5 may take other forms. For example, instead of steps S11 and S12, the average particle diameter downstream of the filter region may be measured, and the turbulent flow generating mechanism may be feedback-controlled so that the average particle diameter approaches a required value. In addition, the turbulence control process in Fig. 5 may be omitted when the filter effect is fixed. Even when the filter effect is variable, the operator may manually adjust the turbulence intensity in the turbulence generating mechanism.

[0043] According to the fluid filter of the embodiment described above, it is possible to avoid problems such as clogging of the filter material such as mesh. In addition, by adjusting the turbulence intensity, it is possible to adjust the filter effect, and it is possible to provide a highly useful filter.

[0044] The various features described in the embodiments do not necessarily have to be provided in their entirety, and some of them may be omitted or combined as appropriate. The present invention is not limited to the embodiments, and various modified examples are possible. For example, the turbulence generating mechanism may have various configurations other than those described in the embodiments. [Industrial Applicability]

[0045] The present invention can be used as a fluid filter. [Explanation of symbols]

[0046] 10, 12 side wall 11 Separation wall 14 Turbulence generation mechanism 14U, 14L electrode 15 Control device 21 First flow path section 22 Second flow path section 23 Third flow path section 24 Filter Area

Claims

1. A fluid filter for filtering particles in a fluid, comprising: a first flow path portion through which the fluid containing the particles flows; a turbulence generating mechanism that generates turbulence in the fluid in a filter region at an end of the first flow path portion to generate an interface where the turbulence intensity changes, thereby generating a filter effect at the interface without using a filter material; a second flow path portion through which the fluid that has passed through the filter region flows.

2. 2. The fluid filter according to claim 1, A fluid filter in which the fluid in the first flow path portion flows as a laminar flow.

3. 2. The fluid filter of claim 1, further comprising: A fluid filter comprising a third flow path portion through which fluid that does not pass through the filter region flows.

4. 2. The fluid filter according to claim 1, The turbulence generating mechanism is a fluid filter capable of adjusting turbulence intensity.

5. 5. The fluid filter according to claim 4, A fluid filter comprising: a control unit that controls the turbulence generating mechanism so that the turbulence intensity is determined according to the size of particles that are to pass through the filter region.

6. 1. A method for filtering particles in a fluid, comprising: (a) flowing a fluid having particles mixed therein through a first flow path portion; (b) generating turbulence in the fluid in a filter region at an end of the first flow path portion to generate an interface where turbulence intensity varies, thereby generating a filter effect at the interface without using a filter material; (c) directing the fluid that has passed through the filter region to a second flow path portion.

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