Working fluid circulation system with backwashing function

Abstract

The invention relates to a working fluid circulation system with a backwashing function, the working fluid circulation system comprises a sewage tank, a backwashing filter element, a clean water tank, a booster pump and a water using module which are sequentially connected through a circulation water path, the backwashing filter element comprises a shell, a filter screen arranged in the shell, a first valve and a second valve, and the shell is provided with a water inlet, a water outlet and a drain outlet; the internal space of the shell is divided into three parts by the filter screen, the first valve and the second valve, when the backwashing filter element is in a filtering mode, the second valve and the drain outlet are closed, and water flow enters from the water inlet, flows through the first valve and the filter screen and then is discharged from the water outlet; when the backwash filter element is in a backwash mode, the first valve and the water outlet are closed, water flow enters from the water inlet, flows through the second valve and the filter screen and then is discharged from the drain outlet, the direction of the water flow flowing through the filter screen is opposite to the filtering mode, attachments on the surface of the filter screen can be efficiently stripped through the water flow, and finally the attachments are thoroughly discharged from the system through the opened drain outlet. And cleaning of the filter screen is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of working fluid circulation, and in particular to a working fluid circulation system with a backwashing function. Background Art

[0002] Taking EDM technology as an example, the working fluid circulation system is a core component that ensures the smooth operation of the machining process. This system not only plays the critical role of establishing a stable discharge channel during machining to ensure continuity and efficiency, but also fulfills the important functions of cooling and dissipating heat. Its performance directly affects machining accuracy, equipment life, and production efficiency.

[0003] However, the working fluid circulation systems currently used in EDM machines face technical bottlenecks that urgently need to be addressed. Filter blockage is a common technical challenge during system operation. Traditional solutions rely on regular filter replacement or manual backwashing, but this approach results in significant resource waste, low system efficiency, and significantly increased maintenance costs. Summary of the Invention

[0004] In view of this, an object of the present invention is to provide a working fluid circulation system with a backwash function, so as to solve the problems in the prior art to a certain extent.

[0005] According to a first aspect of an embodiment of the present invention, there is provided a working fluid circulation system with a backwash function, characterized in that it comprises:

[0006] A sewage tank, a backwash filter element, a clean water tank, a booster pump and a water module connected in sequence by water channels, wherein the water outlet of the water module is connected to the water inlet of the sewage tank;

[0007] The water outlet of the sewage tank is connected to the water inlet of the backwash filter element; the water inlet of the clean water tank is connected to the water outlet of the backwash filter element;

[0008] The backwash filter element includes: a shell, a filter screen, a first valve and a second valve arranged inside the shell, and the shell is provided with a water inlet, a water outlet and a sewage outlet; the filter screen, the first valve and the second valve divide the space inside the shell into three parts, when the backwash filter element is in the filtering mode, the water inlet is opened, the water outlet is opened, the sewage outlet is closed, the first valve is opened, the second valve is closed, water flows into the water inlet, flows through the first valve and the filter screen, and is discharged from the water outlet; when the backwash filter element is in the backwash mode, the water inlet is opened, the water outlet is closed, the sewage outlet is opened, the first valve is closed, the second valve is opened, water flows into the water inlet, flows through the second valve and the filter screen, and is discharged from the sewage outlet.

[0009] Preferably, the working fluid circulation system with backwash function further comprises:

[0010] A liquid level sensor disposed inside the sewage tank, a liquid level sensor disposed inside the clean water tank, and a valve controller;

[0011] The water outlet of the sewage tank is installed near the bottom of the water tank and connected to the water inlet of the backwash filter element; the water inlet of the clean water tank is installed near the bottom of the water tank and connected to the water outlet of the backwash filter element;

[0012] The valve controller is used to control the opening and closing states of the first valve and the second valve according to data collected by the liquid level sensor.

[0013] Preferably, the valve controller controls the opening and closing states of the first valve and the second valve according to the data collected by the liquid level sensor, including:

[0014] The liquid level height of the sewage tank and the liquid level height of the clean water tank are smoothed according to the sliding window smoothing formula. The formula is as follows:

[0015]

[0016] in Indicates the liquid level of the clean water tank after smoothing, represents the liquid level of the return water tank after smoothing, N is the size of the sliding window, i is the number of current windows, t is the current time, h1(i) is the liquid level of the clean water tank at the time of window i; h2(i) is the liquid level of the return water tank at the time of window i;

[0017] The pressure difference is calculated based on the liquid level of the smoothed sewage tank and the liquid level of the clean water tank. The formula is as follows:

[0018]

[0019] Where ΔP is the pressure difference, ρ1 is the density of the liquid in the clean water tank, ρ2 is the density of the liquid in the return water tank, and g is the acceleration due to gravity;

[0020] The current permeability k of the filter element is calculated based on the pressure difference, and the formula is as follows:

[0021]

[0022] Where μ is the dynamic viscosity of the fluid, L is the length of the filter element, ΔP filter Equal to ΔP, A is the cross-sectional area of ​​the filter element, and v represents the average flow velocity of the fluid flowing in the filter element;

[0023] The permeability k is smoothed by sliding window using the following formula:

[0024]

[0025] is the permeability after smoothing, N is the size of the sliding window, i represents the current window number, and k(i) is the permeability at the moment of window i;

[0026] If the current smoothed permeability of the filter element is lower than the first permeability threshold, the backwash filter element is controlled to change from the filtering mode to the backwash mode for a preset time.

[0027] Preferably, the working fluid circulation system with backwash function further comprises:

[0028] The amount of water in the clean water tank is calculated based on the liquid level and cross-sectional area of ​​the clean water tank. The formula is:

[0029] V(t)=B*h1(t)

[0030] V(t) is the amount of water in the clean water tank at time t, B is the cross-sectional area of ​​the clean water tank, and h1(t) is the liquid level of the clean water tank at time t;

[0031] If the current permeability of the filter element is higher than the first permeability threshold, but the water volume in the clean water tank is less than the sum of the water volume required within the preset backwash time and the constant water volume, the backwash filter element is controlled to change from filtration mode to backwash mode for the preset time.

[0032] Preferably, the working fluid circulation system with backwash function further comprises: calculating the rate of change of permeability per unit time

[0033] If the rate of change of the permeability per unit time is greater than a preset rate, the first permeability threshold is changed to a second permeability threshold, and the second permeability threshold is lower than the first permeability threshold.

[0034] Preferably, the working fluid circulation system with backwash function further comprises:

[0035] heat exchangers and cooling units;

[0036] The water channel of the heat exchanger is connected to the clean water tank through two water pipes;

[0037] The heat-conducting structure inside the heat exchanger is connected to the cooling unit so that the cooling unit processes the heat transferred from the heat exchanger.

[0038] Preferably, the working fluid circulation system with backwash function further comprises:

[0039] A sterilization module, wherein the water inlet of the sterilization module is connected to the water outlet of the booster pump, and the water outlet of the sterilization module is connected to the clean water tank.

[0040] Preferably, the working fluid circulation system with backwash function further comprises:

[0041] The second filter module is arranged between the booster pump and the water module; the water inlet of the second filter module is connected to the water outlet of the booster pump, and the water outlet of the second filter module is connected to the water inlet of the water module.

[0042] Preferably, the second filter module is a magnetic filter or a deionizing resin.

[0043] Preferably, the working fluid circulation system with backwash function further comprises:

[0044] The flow regulating valve is arranged between the boosting pump and the second filter module, the water inlet of the flow regulating valve is connected to the water outlet of the boosting pump, and the water outlet of the flow regulating valve is connected to the water inlet of the second filter module.

[0045] The technical solutions provided by the embodiments of the present invention may have the following beneficial effects:

[0046] It can be understood that the technical solution shown in the present invention relates to a working fluid circulation system with a backwash function, including a sewage tank, a backwash filter element, a clean water tank, a booster pump and a water module connected in sequence by a circulating water circuit. The backwash filter element includes: a shell, a filter screen, a first valve and a second valve arranged inside the shell, and the shell is provided with a water inlet, a water outlet and a sewage outlet; the filter screen, the first valve and the second valve divide the space inside the shell into three parts. When the backwash filter element is in the filtering mode, the second valve and the sewage outlet are closed, and water flows into the water inlet, flows through the first valve and the filter screen, and is discharged from the water outlet; when the backwash filter element is in the backwash mode, the first valve and the water outlet are closed, and water flows into the water inlet, flows through the second valve and the filter screen, and is discharged from the sewage outlet. The direction of water flowing through the filter screen is opposite to that in the filtering mode, and the water flow can efficiently peel off the attachments on the surface of the filter screen, and finally completely discharge the system through the opened sewage outlet, completing the cleaning of the filter screen. There is no need for manual disassembly and cleaning of the filter screen, and the system has high operating efficiency.

[0047] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0049] Figure 1 is a schematic block diagram of a working fluid circulation system with a backwash function according to an exemplary embodiment;

[0050] Figure 2 is a cross-sectional schematic diagram of a backwash filter element according to an exemplary embodiment;

[0051] Figure 3 is a backwashing flow chart according to an exemplary embodiment;

[0052] Figure 4 1 is a schematic diagram of a working fluid circulation system with a backwash function for rough machining according to an exemplary embodiment;

[0053] Figure 5 The figure is a schematic diagram of a working fluid circulation system with a backwash function for fine machining according to an exemplary embodiment. DETAILED DESCRIPTION

[0054] Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent like or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present invention, as detailed in the appended claims.

[0055] In one embodiment, Figure 1 is a schematic block diagram of a working fluid circulation system with backwashing function according to an exemplary embodiment. Figure 1 , providing a working fluid circulation system with backwash function, comprising:

[0056] A sewage tank, a backwash filter element, a clean water tank, a booster pump and a water module connected in sequence by water channels, wherein the water outlet of the water module is connected to the water inlet of the sewage tank;

[0057] The water outlet of the sewage tank is connected to the water inlet of the backwash filter element; the water inlet of the clean water tank is connected to the water outlet of the backwash filter element;

[0058] The backwash filter element includes: a shell, a filter screen, a first valve and a second valve arranged inside the shell, and the shell is provided with a water inlet, a water outlet and a sewage outlet; the filter screen, the first valve and the second valve divide the space inside the shell into three parts, when the backwash filter element is in the filtering mode, the water inlet is opened, the water outlet is opened, the sewage outlet is closed, the first valve is opened, the second valve is closed, water flows into the water inlet, flows through the first valve and the filter screen, and is discharged from the water outlet; when the backwash filter element is in the backwash mode, the water inlet is opened, the water outlet is closed, the sewage outlet is opened, the first valve is closed, the second valve is opened, water flows into the water inlet, flows through the second valve and the filter screen, and is discharged from the sewage outlet.

[0059] In specific practice, Figure 2 A cross-sectional schematic diagram of a backwash filter element is shown, see Figure 2 The backwash filter element is a cylinder with a cylindrical filter screen inside. Three valves are provided on the inside of the shell near the water inlet. Valve No. 1 corresponds to the first valve, and valves No. 2 and No. 3 together constitute the second valve, dividing the space inside the shell into three parts. The first part is from the water inlet to the valve, the second part is inside the filter screen, and the third part is from the shell to the filter screen.

[0060] In the filtering mode, valve No. 1 (the first valve) is open, valves No. 2 and No. 3 (the second valves) are closed, and the water flow direction is Figure 2 In the direction of the solid arrow, water flows through the first valve and enters the second space from the first space. Since the sewage outlet is closed, the water flows through the filter screen and enters the third space and flows out from the outlet. When passing through the filter screen, impurities in the water flow will remain on the inside of the filter screen, thereby playing a filtering role.

[0061] When the filter needs to be backwashed, valve No. 1 (the first valve) is closed, and valves No. 2 and No. 3 (the second valves) are opened. At this time, the water flow direction is Figure 2 In the direction of the dotted arrow, water flows through valves No. 2 and No. 3, and enters the third space from the first space. Since the outlet is closed, the water flows through the filter and enters the second space. When passing through the filter, the water flow will wash away the impurities inside the filter and peel off the surface attachments, and finally flow through the filter and be discharged from the sewage outlet.

[0062] Figure 2 The valve is designed as an electric steering valve, and valves No. 1, 2 and 3 are designed as guide plates. When in filtering mode, guide plate No. 1 is opened, and guide plates No. 2 and 3 are closed. When the electric steering valve is pressed, the three guide plates rotate 90° at the same time, guide plates No. 2 and 3 are opened, and guide plate No. 1 is closed.

[0063] It can be understood that the technical solution shown in the present invention relates to a working fluid circulation system with a backwash function, including a sewage tank, a backwash filter element, a clean water tank, a booster pump and a water module connected in sequence by a circulating water circuit. The backwash filter element includes: a shell, a filter screen, a first valve and a second valve arranged inside the shell, and the shell is provided with a water inlet, a water outlet and a sewage outlet; the filter screen, the first valve and the second valve divide the space inside the shell into three parts. When the backwash filter element is in the filtering mode, the second valve and the sewage outlet are closed, and water flows into the water inlet, flows through the first valve and the filter screen, and is discharged from the water outlet; when the backwash filter element is in the backwash mode, the first valve and the water outlet are closed, and water flows into the water inlet, flows through the second valve and the filter screen, and is discharged from the sewage outlet. The direction of water flowing through the filter screen is opposite to that in the filtering mode, and the water flow can efficiently peel off the attachments on the surface of the filter screen, and finally completely discharge the system through the opened sewage outlet, completing the cleaning of the filter screen. There is no need for manual disassembly and cleaning of the filter screen, and the system has high operating efficiency.

[0064] In another embodiment, it should be noted that the automatic backwashing function can be realized by adding a liquid level sensor and a controller. The working fluid circulation system with the backwashing function further includes:

[0065] A liquid level sensor is arranged inside the sewage tank, a liquid level sensor is arranged inside the clean water tank, and a valve controller.

[0066] The sewage tank's outlet is mounted near the tank's bottom and connected to the backwash filter's water inlet. The clean water tank's inlet is mounted near the tank's bottom and connected to the backwash filter's water outlet. The sewage tank, backwash filter, and clean water tank form a U-shaped connecting tube. The valve controller controls the opening and closing of the first and second valves based on data collected by the liquid level sensor.

[0067] Ideally, the liquid levels in the wastewater tank and clean water tank should remain consistent. However, as filtration continues, the filter element gradually becomes clogged, resulting in a decrease in the amount of filtered water. Furthermore, the difference in liquid levels between the return and clean water tanks increases, necessitating backwashing. The valve controller automatically controls the opening and closing of the first and second valves based on the liquid levels in the wastewater and clean water tanks, switching the backwash filter element between filtration and backwash modes.

[0068] It should be noted that the valve controller controls the opening and closing states of the first valve and the second valve according to the data collected by the liquid level sensor, including:

[0069] A pressure differential is calculated based on the liquid levels in the sewage tank and the clean water tank, and the current permeability of the filter element is calculated based on the pressure differential. If the current permeability of the filter element is lower than a first permeability threshold, the backwash filter element is controlled to switch from a filtration mode to a backwash mode for a preset time.

[0070] In practice, see Figure 3 , the current pressure difference can be calculated by the formula ΔP=ρgΔh, where ΔP is the pressure difference, ρ is the density of the liquid, g is the acceleration of gravity, and Δh is the height difference between the liquid levels in the return water tank and the clean water tank.

[0071] In order to reduce the fluctuation of liquid level data, the liquid level data of the return water tank and the clean water tank are smoothed: the liquid level data h1(t) (liquid level height of the clean water tank) and h2(t) (liquid level height of the return water tank) at the corresponding time t are recorded and calculated according to the sliding window smoothing formula:

[0072]

[0073] in and Respectively represent the liquid levels of the clean water tank and the return water tank after smoothing, N is the size of the sliding window, and i represents the current window number. The formula for calculating the pressure after smoothing is:

[0074]

[0075] ρ1 is the density of the liquid in the clean water tank, ρ2 is the density of the liquid in the return water tank, h2 is the height of the liquid level in the return water tank, and h1 is the height of the liquid level in the clean water tank.

[0076] According to Darcy's law, the permeability k of the filter element can be expressed as:

[0077]

[0078] Where μ is the dynamic viscosity of the fluid, L is the length of the filter element, ΔP filter Approximately equal to ΔP, A is the cross-sectional area of ​​the filter element, and v represents the average flow velocity of the fluid flowing in the filter element. v can be calculated from the flow rate Q measured by the flow meter and the cross-sectional area A of the filter element:

[0079]

[0080] In order to avoid the calculation error of permeability k and thus affect the backwash, k is smoothed by sliding window:

[0081]

[0082] Where N is the size of the sliding window and i represents the current window number.

[0083] When the smoothed permeability Below the set permeability threshold k threshold , the backwash process is triggered.

[0084] Due to the complex working conditions of the working fluid circulation system, the filter element will also start backwashing when the following two special situations occur.

[0085] The first special case is that the amount of water in the clean water tank is too little. The working fluid circulation system with backwash function also includes:

[0086] The water volume in the clean water tank is calculated based on the tank's liquid level and cross-sectional area. If the filter element's current permeability is higher than a first permeability threshold, but the water volume in the clean water tank is less than the sum of the required water volume within the preset backwash time and the constant water volume, the backwash filter element is controlled to switch from filtration mode to backwash mode for the preset time.

[0087] Clean water tank water volume V(t) = B*h1(t), B is the cross-sectional area of ​​the clean water tank, L is the constant water volume. According to the size of the filter element and the backwash time requirement, estimate the water volume V required for each backwash m When the water volume in the clean water tank V(t) <V m +L, the backwash process is triggered. The constant water volume L refers to the reserved safety water volume to ensure that the water tank will not be empty.

[0088] The second special case is that the permeability changes abnormally. The working fluid circulation system with backwash function also includes: calculating the rate of change of permeability per unit time

[0089] The rate of change of permeability per unit time reflects the clogging speed of the filter element:

[0090]

[0091] where Δt is the time interval.

[0092] according to The filter element blockage status is divided into the following categories, low-speed blockage: Smaller, the filter element will clog more slowly. Medium speed clogging: Medium, the filter element is blocked at a moderate speed, which is in line with the normal blocking rate. High speed blocking: Larger filter elements clog faster.

[0093] If the rate of change of the permeability per unit time is greater than the preset rate, it means that the vehicle is currently in a high-speed blockage state, and the first permeability threshold is changed to a second permeability threshold, which is lower than the first permeability threshold.

[0094] When the filter element is blocked at high speed, the threshold k should be appropriately lowered. threshold Trigger backwash early.

[0095] It is understood that this structure has the following three advantages: (1) The connection between the return water tank and the clean water tank adopts a U-shaped tube design. By utilizing the principle of fluid dynamics, the liquid in the return water tank flows naturally into the clean water tank through the pressure difference without the need for additional pumping equipment, thereby saving energy consumption. (2) The U-shaped tube structure is based on the principle of communicating vessels, so that under static conditions, the liquid level heights in the two water tanks are automatically adjusted to be equal. When the liquid level is unbalanced, backwashing can be performed to balance the liquid levels on both sides again, realizing automatic balance control of the liquid level and ensuring the stability of the system. (3) The backwash filter element structure, this two-way flushing mode, can effectively remove surface attachments and finally completely discharge the system through the open drain port, completing a fully automatic cleaning cycle. (4) The system can automatically determine when to backwash. When the liquid level difference continues to increase and exceeds the preset safety range, the system will automatically start the backwash program without manual intervention. In addition, the system can also predict the clogging trend of the filter element based on the water volume and operating status in the water tank and perform backwashing in advance, thereby further extending the service life of the filter element and reducing maintenance frequency and cost.

[0096] In a specific embodiment, a working fluid circulation system with backwash function for rough machining is provided, which can be specifically Figure 4 For example, the system is designed to achieve a filtration accuracy of less than 100 microns. PP cotton is used in the primary filtration stage to remove large particles of impurities from the working fluid. The working fluid circulates through a water pump and pipes, simplifying the system structure and eliminating the need for disinfection or constant temperature. This reduces operating costs and meets the economic and practical requirements of rough processing.

[0097] The dimensions of the water tank in this embodiment are 300 mm long, 300 mm wide, and 1000 mm high. The diameter of the pipe between the two water tanks is 50 mm. The backwash filter element has a length of L = 0.3 m and a cross-sectional area of ​​A = 0.05 m. 2 . Permeability threshold k threshold =5.0×10 -10 m 2 In the initial state, the liquid level of the two water tanks is 500mm, and the system working flow rate is 6L / min.

[0098] Calculated according to the flow rate formula: The system working flow rate Q = 6.0 L / min = 1.0 × 10 -4 m 3 / s, cross-sectional area A = 0.05m 2 .

[0099] Assume the liquid level difference is Δh(t), and initially Δh(0) = 0. As time goes by, the return tank level h2(t) rises, and the clean water tank level h1(t) drops. The rate of change of the liquid level caused by the flow rate Q is: Where B is the cross-sectional area of ​​the water tank, which is 0.09 m 2 .

[0100] The liquid level height difference is Δh(t)=h2(t)-h1(t)=2.222×t×10 -3 m, where h2(t) = 0.5 + 1.111 × t × 10 -3 , h1(t)=0.5-1.111×t×10 -3 .

[0101] The pressure on the left and right sides of the filter element ΔP(t)=ρ2gh2(t)-ρ1gh1(t)=1100×9.81×(0.5+

[0102] 1.111×10 -3 ×t)-1000×9.81×(0.5-1.111×10 -3 × t) = 9.81 × (50 + 2.333 × 10 - 3 t)Pa.

[0103] Calculate filter element permeability based on Darcy's law Where μ = 0.001 Pa·s is the dynamic viscosity of the fluid, L = 0.3 m is the length of the filter element, and the pressure on the left and right sides of the filter element ΔP(t) = 9.81×(50+2.333×10 -3 t)Pa, A=0.05m 2 is the cross-sectional area of ​​the filter element, v = 2.0 × 10 -3 It represents the average flow rate of the fluid flowing in the filter element.

[0104] The permeability threshold of the filter element is k threshold =5.0×10 -10 m 2 , when the filter element reaches the threshold, backwashing is required. Assume k(t) = 5.0×10 -10 It can be concluded that The solution is t ≈ 29,000 seconds = 8.06 hours. The system will reach the permeability threshold in about 8.06 hours, triggering the backwash process.

[0105] In another embodiment, see Figure 5 , the working fluid circulation system with backwash function further includes:

[0106] Heat exchanger and cooling unit; the water channel of the heat exchanger is connected to the clean water tank through two water pipes; the heat-conducting structure inside the heat exchanger is connected to the cooling unit, so that the cooling unit processes the heat transferred from the heat exchanger.

[0107] The heat exchanger and cooling unit utilizes a Lichen LC-LTC-5 / 10 low-temperature cooling circulator. This module regulates the working fluid temperature, ensuring it circulates within an optimal temperature range. This module helps maintain a balanced temperature in the processing area, preventing overheating and improving processing efficiency and quality.

[0108] In another embodiment, see Figure 5 The working fluid circulation system with backwash function also includes: a sterilization module ( Figure 5 The water inlet of the sterilization module is connected to the water outlet of the booster pump, and the water outlet of the sterilization module is connected to the clean water tank.

[0109] In another embodiment, see Figure 5 , the working fluid circulation system with backwash function further includes:

[0110] The second filter module is disposed between the booster pump and the water module. The water inlet of the second filter module is connected to the water outlet of the booster pump, and the water outlet of the second filter module is connected to the water inlet of the water module. The second filter module is a magnetic filter or a deionized resin.

[0111] The backwash filter, sterilization module, and secondary filtration module together constitute the filtration system, which removes impurities and particles from the working fluid, improving its cleanliness, protecting machine tools, and extending the service life of the working fluid. The filtration system utilizes a modular design and features a backwash filter element, allowing for flexible replacement of filter media such as PP cotton, UF ultrafiltration, deionization resin, and magnetic filters to meet diverse processing requirements. This design enhances the system's adaptability and flexibility, allowing users to select and configure the appropriate filter media based on specific processing conditions and quality requirements.

[0112] During the initial filtration phase, the filtration system collects wastewater generated during machine tool processing from the wastewater tank. This wastewater first passes through a backwash filter element, primarily to remove large impurities such as metal shavings and larger dust particles. As the filtration process continues, the filter element may gradually become clogged, resulting in a difference in the liquid level on the left and right sides of the U-shaped tube. Monitors installed in both tanks provide real-time monitoring of the liquid level and density in the wastewater and clean water tanks. A backwash algorithm calculates the current permeability threshold k and the backwash cycle. If the calculated value falls below this threshold, the filter element may be severely clogged, necessitating a backwash. Backwashing, performed through the backwash filter element, is crucial for improving EDM accuracy and extending machine tool life. The working fluid, after initial filtration, then flows into a clean water tank for storage. From the clean water tank, the working fluid flows by gravity into a heat exchanger, which regulates the working fluid temperature to meet the precise temperature conditions required for EDM. The heat exchanger is connected to the clean water tank through a pipe to form a communicating vessel structure, ensuring that the cooled working fluid automatically flows back to the clean water tank to maintain the continuous operation of the circulation system.

[0113] During the secondary treatment and distribution phase, a booster pump draws working fluid from the clean water tank and distributes it to two paths. One path is a circulating sterilization path, where the working fluid undergoes UV sterilization treatment to eliminate potential microbial contamination and ensure the hygienic safety of the working fluid. The treated working fluid then returns to the clean water tank, ready for the next cycle.

[0114] The other path is the supply path to the machine tool. Here, the working fluid is treated with deionized resin to further increase the water's resistivity and remove ions, ensuring that the working fluid's conductivity meets the requirements for EDM machining. This step is crucial for preventing arcing during machining and improving machining quality. The deionized working fluid is ultimately delivered to the EDM machine tool, where it cools and cleans the machining area, removing heat and debris generated during machining, and ensuring machining stability and part precision.

[0115] The three separate filter modules not only enable the selection of the most appropriate filter media based on specific filtration needs, thus avoiding overinvestment and waste of resources, but also, when a filter media needs to be replaced or upgraded, only that module needs to be operated on, without having to replace the entire system, thus reducing long-term operating and maintenance costs. The modular design simplifies the maintenance and upgrade process, allowing for quick and economical repairs or replacements of specific filter media, reducing system downtime. At the same time, as technology advances, users can easily introduce new technologies or upgrade existing modules, including backwash filter elements, to improve system performance, ensuring the system remains at the forefront of technology while protecting the initial investment. The automated cleaning function of the backwash filter element further reduces maintenance workload and improves system reliability and efficiency.

[0116] In another embodiment, see Figure 5 The working fluid circulation system with backwash function also includes: a flow regulating valve, which is arranged between the booster pump and the second filter module, the water inlet of the flow regulating valve is connected to the water outlet of the booster pump, and the water outlet of the flow regulating valve is connected to the water inlet of the second filter module.

[0117] In addition, it also includes manual control valves and liquid level switches to adjust and control the flow, liquid level and circulation process of the working fluid. The supply and circulation of the working fluid can be adjusted automatically or manually according to processing requirements.

[0118] In a specific embodiment, a refined working fluid circulation system with backwash function is provided, which can be specifically Figure 5 For example, a sterilization module is added to ensure the sterility of the water. At the same time, a flow control valve is added, and the flow rate is required to be highly stable to ensure the stability of the processing process. The dimensions of the water tank in this embodiment are 200 mm long, 200 mm wide, and 800 mm high, and the diameter of the pipe between the two water tanks is 50 mm. The heat exchanger is placed under the clean water tank and is connected to the clean water tank through two hard pipes with a diameter of 50 mm on the left and right to achieve effective heat exchange. In this system, the filter element used in the primary filtration stage is a UF ultrafiltration filter. The filter element length L = 0.2 m, and the cross-sectional area A = 0.05 m 2 . Permeability threshold k threshokd =1.0×10 -10 m 2 In the initial state, the liquid level of the two water tanks is 400mm, and the system working flow rate is 5L / min.

[0119] Calculated according to the flow rate formula: The system working flow rate Q = 5L / min = 8.33×10 -5 m 3 / s, cross-sectional area A = 0.05m 2 .

[0120] Assume the liquid level difference is Δh(t), and initially Δh(0) = 0. As time passes, the return tank level h2(t) rises, and the clean water tank level h1(t) drops. The rate of change of the liquid level due to the flow rate q is:

[0121] Where B is the cross-sectional area of ​​the clean water tank, which is 0.04m 2 .

[0122] The liquid level height difference is Δh(t)=h2(t)-h1(t)=2×2.0825×10 -3 ×t=4.165×t×10 -3 m.

[0123] The pressure on the left and right sides of the filter element ΔP(t)=ρ2gh2(t)-ρ1gh1(t)=1050×9.81×(0.4+

[0124] 2.0825×10 -3 ×t)-1000×9.81×(0.4-2.0825×10 -3 ×t)=9.81×

[0125] (20+4.2691×10 -3 t)Pa, where h2(t)=0.4+2.0825×t×10 -3 , h1(t)=0.4-2.0825×t×10 -3 .

[0126] Calculate filter element permeability based on Darcy's law Where μ = 0.001 Pa·s is the dynamic viscosity of the fluid, L = 0.2 m is the length of the filter element, and the pressure on the left and right sides of the filter element ΔP(t) = 9.81×(20+4.2691×10 -3 t)Pa, A=0.05m 2 is the cross-sectional area of ​​the filter element, v = 1.66 × 10 -3 It represents the average flow rate of the fluid flowing in the filter element.

[0127] The permeability threshold of the filter element is k threshold =1.0×10 -10 m 2 , when the filter element reaches the threshold, backwashing is required. Assume k(t) = 1.0×10 -10 It can be concluded that The solution is It is calculated that the system will reach the permeability threshold in approximately 12.5 hours, triggering the backwash process.

[0128] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0129] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is at least two.

[0130] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0131] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0132] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0133] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing module, or each unit may exist physically separately, or two or more units may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or in the form of software functional modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they may also be stored in a computer-readable storage medium.

[0134] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0135] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0136] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A working fluid circulation system with backwash function, characterized in that: include: A sewage tank, a backwash filter element, a clean water tank, a booster pump and a water module connected in sequence by water channels, wherein the water outlet of the water module is connected to the water inlet of the sewage tank; The water outlet of the sewage tank is connected to the water inlet of the backwash filter element; the water inlet of the clean water tank is connected to the water outlet of the backwash filter element; The backwash filter element includes: a shell, a filter screen, a first valve and a second valve arranged inside the shell, and the shell is provided with a water inlet, a water outlet and a sewage outlet; the filter screen, the first valve and the second valve divide the space inside the shell into three parts, when the backwash filter element is in the filtering mode, the water inlet is opened, the water outlet is opened, the sewage outlet is closed, the first valve is opened, the second valve is closed, water flows into the water inlet, flows through the first valve and the filter screen, and is discharged from the water outlet; when the backwash filter element is in the backwash mode, the water inlet is opened, the water outlet is closed, the sewage outlet is opened, the first valve is closed, the second valve is opened, water flows into the water inlet, flows through the second valve and the filter screen, and is discharged from the sewage outlet.

2. The working fluid circulation system with backwash function according to claim 1, characterized in that: Also includes: A liquid level sensor disposed inside the sewage tank, a liquid level sensor disposed inside the clean water tank, and a valve controller; The water outlet of the sewage tank is installed near the bottom of the water tank and connected to the water inlet of the backwash filter element; the water inlet of the clean water tank is installed near the bottom of the water tank and connected to the water outlet of the backwash filter element; The valve controller is used to control the opening and closing states of the first valve and the second valve according to data collected by the liquid level sensor.

3. The working fluid circulation system with backwash function according to claim 2, characterized in that: The valve controller controls the opening and closing states of the first valve and the second valve according to the data collected by the liquid level sensor, including: The liquid level height of the sewage tank and the liquid level height of the clean water tank are smoothed according to the sliding window smoothing formula. The formula is as follows: in Indicates the liquid level of the clean water tank after smoothing, represents the liquid level of the return water tank after smoothing, N is the size of the sliding window, i is the current window number, t is the current time, h1(i) is the liquid level of the clean water tank at the time of window i; h2(j) is the liquid level of the return water tank at the time of window i; The pressure difference is calculated based on the liquid level of the smoothed sewage tank and the liquid level of the clean water tank. The formula is as follows: Where ΔP is the pressure difference, ρ1 is the density of the liquid in the clean water tank, ρ2 is the density of the liquid in the return water tank, and g is the acceleration due to gravity; The current permeability k of the filter element is calculated based on the pressure difference, and the formula is as follows: Where μ is the dynamic viscosity of the fluid, L is the length of the filter element, ΔP filter Equal to ΔP, A is the cross-sectional area of ​​the filter element, and v represents the average flow velocity of the fluid flowing in the filter element; The permeability k is smoothed by sliding window using the following formula: is the permeability after smoothing, N is the size of the sliding window, i represents the current window number, and k(i) is the permeability at the moment of window i; If the current smoothed permeability of the filter element is lower than the first permeability threshold, the backwash filter element is controlled to change from the filtering mode to the backwash mode for a preset time.

4. The working fluid circulation system with backwash function according to claim 3, characterized in that: Also includes: The amount of water in the clean water tank is calculated based on the liquid level and cross-sectional area of ​​the clean water tank. The formula is: V(t)=B*h1(t) V(t) is the amount of water in the clean water tank at time t, B is the cross-sectional area of ​​the clean water tank, and h1(t) is the liquid level of the clean water tank at time t; If the current permeability of the filter element is higher than the first permeability threshold, but the amount of water in the clean water tank is less than the sum of the water required within the preset backwash time and the constant water volume, the backwash filter element is controlled to change from filtration mode to backwash mode for the preset time.

5. The working fluid circulation system with backwash function according to claim 3, characterized in that: Also includes: Calculate the rate of change of permeability per unit time If the rate of change of the permeability per unit time is greater than a preset rate, the first permeability threshold is changed to a second permeability threshold, and the second permeability threshold is lower than the first permeability threshold.

6. The working fluid circulation system with backwash function according to any one of claims 1 to 5, characterized in that: Also includes: heat exchangers and cooling units; The water channel of the heat exchanger is connected to the clean water tank through two water pipes; The heat-conducting structure inside the heat exchanger is connected to the cooling unit so that the cooling unit processes the heat transferred from the heat exchanger.

7. The working fluid circulation system with backwash function according to any one of claims 1 to 5, characterized in that: Also includes: A sterilization module, wherein the water inlet of the sterilization module is connected to the water outlet of the booster pump, and the water outlet of the sterilization module is connected to the clean water tank.

8. The working fluid circulation system with backwash function according to any one of claims 1 to 5, characterized in that: Also includes: The second filter module is arranged between the booster pump and the water module; The water inlet of the second filter module is connected to the water outlet of the booster pump, and the water outlet of the second filter module is connected to the water inlet of the water module.

9. The working fluid circulation system with backwash function according to claim 8, characterized in that: The second filter module is a magnetic filter or a deionizing resin.

10. The working fluid circulation system with backwash function according to claim 8, characterized in that: Also includes: The flow regulating valve is arranged between the boosting pump and the second filter module, the water inlet of the flow regulating valve is connected to the water outlet of the boosting pump, and the water outlet of the flow regulating valve is connected to the water inlet of the second filter module.

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