Fluid filters

Abstract

We provide a new fluid filter that utilizes fluid flow. [Solution] The fluid filter comprises side walls 10 and 12 that form a flow path and a separation wall 11 formed between them. A turbulence generation mechanism 14 is provided in a portion of the region from the end of the separation wall 11 to the side wall 10, and the turbulence 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 and 12 as F1, and becomes F2 after passing through the filter region 24 and the rest as F3. Large particles PL mixed in the fluid are pushed back by the turbulence and cannot pass through the filter region 24, but for small particles PS, the force they receive from the flow is greater than the force from the turbulence and they can pass through the filter region 24. By utilizing turbulence in this way, a filtering effect can be obtained without using filter materials such as mesh, and the filtering effect can be adjusted by controlling the turbulence intensity.

Description

Technical Field

[0001] The present invention relates to a fluid filter for removing particles in a fluid.

Background Art

[0002] Conventionally, as a fluid filter for separating, removing, or filtering particles of a specific size mixed in a fluid, those using a filter medium such as a metal mesh, a filter cloth, or a non-woven fabric laminate have been used. However, these filters have problems such as clogging, the size of particles that can be separated, etc. being fixed by the filter, and there being a limit to the fineness of the particles that can be separated, and a filter based on a new principle has been desired. On the other hand, although 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 of flowing clean air over the surface of a semiconductor wafer to form a laminar boundary layer and a turbulent boundary layer to prevent floating fine particles from descending onto the semiconductor substrate. Further, Patent Document 2 discloses a technique of flowing a supercritical fluid over the surface of a wafer in a cleaning process of a semiconductor wafer, separating contaminants on the wafer by making it into a turbulent state, and then transporting the contaminants downstream by making it into a laminar state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a new fluid filter that utilizes the flow of a fluid, based on the problems in conventional filters and the technical level regarding the utilization of fluids. [Means for solving the problem]

[0005] The present invention A fluid filter for filtering particles in a fluid, A first flow channel through which the fluid containing the aforementioned particles flows, In the filter region at the end of the first flow channel, a turbulence generation mechanism is provided to generate turbulence in the fluid, The fluid filter can be further comprising a second flow path section for passing the fluid that has passed through the filter region.

[0006] The inventors discovered that when an interface with varying turbulence intensity exists within a flow, a filtering effect occurs, where particles in the fluid are separated into those that pass through the interface and those that do not. According to the present invention, turbulence can be generated in the filtering region, and the aforementioned interface can be intentionally created within the flow, thereby enabling it to function as a filter for filtering particles in the fluid.

[0007] The fluids used in this invention can include a variety of viscous fluids such as water, seawater, oil, air, gas, liquid crystal, plasma, ionic fluid, dielectric fluid, and fluid metal. Multiple types of fluids may be mixed together. In this invention, the shape, dimensions, and other properties of the filter region can be determined arbitrarily.

[0008] Furthermore, various turbulence generation mechanisms can be used in this invention. The fluid may be agitated using 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 electric convection. Alternatively, the fluid may be agitated using opposing propellers, rotating bodies, etc. The number, arrangement, and orientation of the rotation axes of the opposing propellers, etc., can be determined arbitrarily. The fluid may be agitated by a mechanism that injects fluid into the filter area. The arrangement and number of injection nozzles for injecting the fluid can be determined arbitrarily. A mechanism for injecting a jacuzzi, or bubbles, may be provided in the filter area. In this case as well, the arrangement and number of injection nozzles can be determined arbitrarily. Turbulence may be generated by thermal convection by heating the filter region. When using charged fluids such as ionic fluids, an AC or DC voltage may be applied to the filter stream. Ion beams, electron beams, etc., may also be irradiated. A mechanism for generating waves may be provided in the filter region. Turbulence may be generated by the flow within the pipe.

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

[0010] The interface of the filter region refers to a surface where the turbulence intensity changes somewhat abruptly, and is not necessarily limited to cases where the flow changes from laminar to turbulent. For example, it may be possible to generate turbulence that is sufficiently stronger than weak turbulence. However, according to the above embodiment, since the upstream side is laminar flow, the turbulence strength at the interface acts effectively, which has the advantage of effectively obtaining the filtering effect of the present invention. Various methods can be used to create a laminar flow on the upstream side, such as using flow straightening plates.

[0011] In the present invention, further, The system may also include a third flow path for fluid that does not pass through the filter region.

[0012] This allows for the effective removal of particles and other materials that did not pass through the filter area. However, the present invention does not exclude configurations that do not include the third flow path section described above. For example, all fluid flowing from the first flow path section may flow into the filter area.

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

[0014] By doing so, the size of the particles that can be filtered in the filter region, that is, the filtering performance can be changed. Generally, in a filter using a filtering material such as a mesh, the filtering performance is fixed, whereas according to the present invention, since the filtering performance can be made variable, the usefulness of the fluid filter can be greatly improved. As described above, various mechanisms can be applied to the turbulent flow generating mechanism, and the method of adjusting the turbulent flow intensity can also be a method according to the type of the mechanism to be applied.

[0015] When adjusting the turbulent flow intensity in this way, it may be provided with a control unit that controls the turbulent flow generating mechanism so that the turbulent flow intensity is determined according to the size of the particles to pass through the filter region.

[0016] By doing so, the filtering effect can be controlled so as to filter particles of a desired size. In this case, various control methods can also be employed. For example, based on an equation for determining the size of the particles passing through the filter region, the turbulent flow intensity may be analytically calculated and controlled so as to achieve it. Also, a map or table showing the relationship between the size of the particles passing through the filter region and the turbulent flow intensity may be prepared in advance, and the turbulent flow intensity may be controlled based on this. Furthermore, the average particle size after passing through the filter region may be measured, and the turbulent flow intensity may be controlled by feedback control so that this becomes the desired size. In addition, various methods can be employed.

[0017] The various features of the present invention described above do not necessarily have to be all present, and some may be omitted or combined as appropriate. Furthermore, the present invention may be configured not only as a fluid filter, but also as a filtration method for filtering particles in a fluid. Moreover, it can be configured in various forms, such as a control method for controlling turbulence intensity, or a computer program for realizing such control by computer. [Brief explanation of the drawing]

[0018] [Figure 1] This is an explanatory diagram illustrating the structure of a fluid filter as an example. [Figure 2] This is an explanatory diagram illustrating how larger particles cannot pass through an interface. [Figure 3] This is an explanatory diagram showing how small particles pass through an interface. [Figure 4] This is an explanatory diagram showing the relationship between turbulence intensity and filtering effect. [Figure 5] This is a flowchart of the turbulence control process. [Modes for carrying out the invention]

[0019] The following describes embodiments of the present invention. Figure 1 is a schematic diagram illustrating the structure of a fluid filter as an example. Figure 1(a) shows a plan view. The fluid filter of the embodiment includes side walls 10 and 12 that form a flow path and a separation wall 11 formed between them. A turbulence generation mechanism 14 for generating turbulence is provided in a portion of the region from the end of the separation wall 11 to the side wall 10. The region where turbulence is generated by the turbulence generation mechanism 14 becomes the filter region 24, which provides a filtering effect that filters out only particles of a predetermined size or smaller.

[0020] The fluid flows from upstream through the channel between the side walls 10 and 12, as flow F1. The portion of flow F1 that reaches the filter region 24, i.e., the lightly grayed-out portion in the figure, is the first channel section 21. A portion of flow F1 passes through the filter region 24 and flows through a second flow channel section 22, which consists of side walls 10 and separation walls 11, as in flow F2. The remaining portion does not pass through the filter region 24 and flows through a third flow channel section 23, which consists of side walls 12 and separation walls 11, as in flow F3.

[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 schematically shown, but the fluid may contain particles of other sizes as well. In the first flow channel section 21, particles PS and PL are mixed, but due to the filtering effect, particles PL cannot pass through the filter region 24, so only particles PS are mixed into the second flow channel section 22. On the other hand, particles PL that cannot pass through the filter region 24 flow out into the third flow channel section 23. Since fluid that does not pass through the filter region 24 also flows through the third flow channel section 23, small particles PS will also be mixed in there.

[0022] Figure 1(b) schematically shows the cross-sectional structure of the portion where the turbulence generation mechanism 14 is provided. The turbulence generation mechanism 14 can take various configurations, but in this embodiment, a mechanism is applied that generates turbulence by creating liquid crystal electroconvection in the filter region 24 by applying a voltage in a direction perpendicular to the flow. Accordingly, 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 aforementioned convection occurs, and turbulence is generated. The turbulence intensity can be adjusted by controlling the voltage between electrodes 14U and 14L. In the diagram, turbulence is shown with arrows indicating the generation of numerous vortices, but this is a schematic representation, and turbulence in this invention is not necessarily limited to such vortices.

[0023] Since the turbulence generation mechanism 14 in the embodiment is a mechanism that can adjust the turbulence intensity, the fluid filter in the embodiment is provided with a control device 15 that controls the turbulence generation mechanism 14. When the control device 15 receives a request for the size of particles to pass through the filter region 24, it calculates the turbulence intensity required to achieve the filtering effect and controls the turbulence generation mechanism 14 accordingly. The control device 15 may be configured using hardware such as an ASIC, but it may also be configured in software by installing a computer program to implement the above-described control functions on a computer equipped with a CPU and memory.

[0024] As shown in Figure 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 particles PL that could not pass through the filter region 24 can easily flow out along the filter region 24 into the third flow channel 23. Angle A can be determined arbitrarily. It is acceptable to set A = 90 degrees, that is, to set the filter area perpendicular to the side wall 10.

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

[0026] In the fluid filter of the embodiment, the flow F1 in the first flow channel 21 may be turbulent. 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 a filtering effect, it is preferable that the flow F1 is laminar. From this viewpoint, the first flow channel 21 may be provided with a flow straightening plate or other mechanism for laminarizing the flow F1.

[0027] Figure 2 is an explanatory diagram illustrating how larger particles cannot pass through the interface. Figures 2(a) to 2(c) show the behavior over time when a fluid containing particles of various sizes is flowed through a filter region with turbulence induced by liquid crystal electric convection. In each photograph, the darker gray area in the upper right is filter area 24. Below that is the upstream flow F1 of filter area 24. Figure 2(a) shows that a relatively large particle PL1 is approaching the filter region 24. Then, in Figure 2(b) at the next time step, we can see that particle PL1 is in contact with the interface of the filter region 24. Looking at Figure 2(c) at the following time step, we can see that particle PL1 is moving along the interface of the filter region 24 and is not entering the interior of the filter region 24. In other words, it is confirmed that such a large particle PL1 is being filtered out by the filter region 24. On the other hand, as shown in Figure 2(c), it can be confirmed that the relatively small particles PS1 penetrate into the filter region 24. These particles will then flow downstream after passing through the filter region 24.

[0028] Figure 3 is an explanatory diagram illustrating how small particles pass through an interface. The diagrams are shown in order from Figure 3(a) to Figure 3(c) as time progresses. In each photograph, the darker gray area in the lower left is the filter area 24. The area to the upper right of that is the flow F2 after passing through the filter area 24. Figure 3(a) shows that relatively small particles PS2 are approaching the interface from inside the filter region 24. Then, in Figure 3(b) at the next time step, we can see that the particles PS2 are attempting to move away from the interface. Looking at Figure 3(c) at the following time step, we can see that the particles PS2 have moved away from the interface of the filter region 24 and are flowing downstream. In other words, it can be confirmed that particles PS2 of this size can pass through the filter region 24.

[0029] Thus, it was experimentally confirmed that the fluid filter of this embodiment exhibits a filtering effect by generating turbulence in the filter region 24. This filtering effect depends on the intensity of the turbulence.

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

number

[0031] Figure 4(b) shows P when the turbulence intensity is varied. block This shows the change in P. 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, P block It is increasing rapidly and qualitatively shows the same trend as curve C1. Also, as the turbulence intensity ε decreases, the filterable particle size (P block It can be seen that the particle size φc) is larger when = 0.5.

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

[0033] In this embodiment, the theory behind the filtering effect is not fully understood, but it is thought to be due to the relative magnitudes of the Stokes effect and Reynolds stress acting on the particles, as shown below. The force F acting on a particle in a fluid is given by the following equation:

number

[0034] Here, μ: viscosity coefficient a: Particle radius U: Average fluid velocity u: Particle flow velocity u x Fluctuation component of fluid velocity ρ: density of the fluid That is the case.

[0035] The first term on the right-hand side of the above equation represents the Stokes drag, that is, the force with which the fluid pushes the particle in the direction of the flow velocity. The second term on the right-hand side represents the Reynolds stress, that is, the force acting in the direction of pushing the particle out of the interface due to the velocity gradient at the turbulent interface. Therefore, if the particle size satisfies the relationship Stokes drag > Reynolds stress, the particle will enter the filter region. Conversely, if the particle size satisfies the relationship Stokes drag < Reynolds stress, the particle will be filtered out in the filter region. The particle size at which Stokes drag = Reynolds stress can be called the threshold φc that separates the two. Since Stokes drag is proportional to the first power of particle radius a, while Reynolds stress is proportional to the cube of particle radius a, it can be seen that as particle size increases, Reynolds stress tends to increase rapidly. Furthermore, since Reynolds stress increases with increasing turbulence intensity, it can be seen that the particle radius corresponding to the threshold tends to decrease. From this, it can be said that the above formula is consistent with the trend shown in Figure 4.

[0036] Next, we determine the threshold particle radius φc in the above equation. For this particle, assuming that the Stokes effect and Reynolds stress are balanced at the interface, F=0. As a result, the particle velocity u=0. Under these conditions, the particle radius φc is obtained by calculating the following equation.

number

[0037] In other words, the threshold particle radius φc depends on the flow velocity U and the turbulence intensity. Conversely, if the threshold particle radius φc passing through the filter region is given as a requirement, a relationship between the flow velocity U and the turbulence intensity that satisfies it can be obtained.

[0038] Finally, based on the above, the control process by which the control device 15 (see Figure 1) controls the turbulence generation mechanism 14 in the fluid filter of the embodiment will be described. Figure 5 is a flowchart of the turbulence control process. This control process begins when the fluid filter is activated.

[0039] When the control device 15 starts processing, it receives input for the required particle size to be filtered (step S10). Here, the operator inputs the particle radius φc as described earlier. Input can be done in various ways. Numerical values ​​may be entered using a keyboard, or the particle size may be indicated using a graphics user interface. Mechanical input devices such as dials may also be used.

[0040] When a required value for 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 set analytically based on the equation shown in Equation 2. Alternatively, a map or table like the one in Figure 4(c) may be stored in advance, and the turbulence intensity may be set by referring to it. Then, the control device 15 controls the turbulence generation mechanism so that the set turbulence intensity is achieved (step S12).

[0041] By executing the above process until completion, a filtering effect corresponding to the required value can be achieved. Furthermore, the filtering effect may be adjustable by changing the required value in step S10 while the fluid filter is operating.

[0042] The turbulence control process described in Figure 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 turbulence generation mechanism may be feedback-controlled so that this approaches the required value. Furthermore, the turbulence control process shown in Figure 5 may be omitted if the filter effect is fixed during operation. Even when the filter effect is variable, the operator may manually adjust the turbulence intensity in the turbulence generation mechanism.

[0043] The fluid filter of the embodiment described above can avoid problems such as clogging of filter materials such as mesh. Furthermore, the filtering effect can be adjusted by adjusting the turbulence intensity, thereby providing a highly useful filter.

[0044] The various features described in the examples do not necessarily need to be present in their entirety; some may be omitted or combined as appropriate. Furthermore, the present invention can be configured in various ways beyond the examples. For example, the turbulence generation mechanism can take on various configurations other than those in the examples. [Industrial applicability]

[0045] This 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 channel 22 Second flow channel 23 Third flow channel 24 Filter Region

Claims

1. A fluid filter for filtering particles in a fluid, A first flow channel through which the fluid containing the aforementioned particles flows, In the filter region at the end of the first flow channel, a turbulence generation mechanism is provided to generate turbulence in the fluid, A fluid filter comprising a second flow channel through which the fluid that has passed through the filter region flows.

2. A fluid filter according to claim 1, The fluid in the first flow channel is a fluid filter that flows in a laminar manner.

3. A fluid filter according to claim 1, further, A fluid filter comprising a third flow path section for which fluid that does not pass through the aforementioned filter region flows.

4. A fluid filter according to claim 1, The aforementioned turbulence generation mechanism is a fluid filter with a mechanism capable of adjusting the turbulence intensity.

5. A fluid filter according to claim 4, A fluid filter comprising a control unit that controls the turbulence generation mechanism so that the turbulence intensity is determined according to the size of the particles to be passed through the filter region.

6. A filtration method for filtering particles in a fluid, (a) A step of flowing the fluid containing the particles into the first flow channel, (b) A step of generating turbulence in the fluid in the filter region at the end of the first flow channel, (c) A filtration method comprising the step of flowing the fluid that has passed through the filter region into a second flow channel.

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