PIV (Particle Image Velocimetry) technology-based partition flocculation basin parameter optimization method

Abstract

The invention discloses a method for optimizing parameters of a partition flocculation basin based on a PIV (Particle Image Velocimetry) technology. Flocculation tests under different blade vortex generator numbers and arc-shaped blade angles are carried out in the partition plate flocculation basin, and detection is carried out through the PIV system assembly. Analyzing and calculating the morphological parameters of the maximum energetic vortex in each gallery provided with the blade vortex generator, the vortex density of the blade side wall area and the average particle size of the flocculating constituent through a detection result, and then establishing a mathematical model of the average particle size of the flocculating constituent, the morphological parameters, the vortex density, the number of the vortex generators and the angle of the arc-shaped blade; and finally, according to the established mathematical model, obtaining the optimal number of the blade vortex generators and the angle of the arc-shaped blades corresponding to the maximum average particle size of the flocculating constituent in each gallery provided with the blade vortex generators through an optimization algorithm. According to the method, the structural parameters of the partition flocculation basin are optimized, and the optimization result is relatively high in accuracy.

Description

Technical Field

[0001] The present invention belongs to the field of optimizing the parameters of a flocculation tank, and particularly relates to a method for optimizing the parameters of a baffle flocculation tank based on PIV technology. Background Art

[0002] "Water treatment" is a process of conditioning water quality such as sedimentation, filtration, coagulation, flocculation, corrosion inhibition, and scale inhibition of water by physical, chemical, and biological means to remove some harmful substances that are unnecessary for production and life. Among them, flocculation is an operation in which suspended particles in water are aggregated and enlarged by a flocculant, or flocs are formed to accelerate the sedimentation of harmful substances to achieve the purpose of solid-liquid separation. In the initial stage of flocculation, small-scale and high-intensity vortices are beneficial to increasing the number of collisions between small-scale flocculation nuclei and raw water colloid impurities. However, as the flocculation process develops, when the scale of the flocs is larger than the scale of the vortices, they will be affected by the vortex shear force and are easily chopped up, which is not conducive to the later sedimentation of the flocs. At this time, it is necessary for the vortex scale in the fluid to be as large as possible larger than the scale of the flocs, so that it can not only improve the capture ability of the flocs in water, but also ensure that the already formed flocs are not chopped up and continue to grow, creating good conditions for the later sedimentation of the flocs. In view of the importance of turbulent vortices in the flocculation process, it is necessary to conduct a detailed study on them. Different scales of vortices will be generated when the fluid flows through curved or flat surfaces of different shapes. If a reverse-order vortex structure of the fluid conducive to the flocculation process is to be constructed to optimize the flocculation process in the flocculation tank, the primary problem is how to control the vortex size and the realization of vortex parameters. And the vortex size and vortex parameters are related to the internal structure parameters of the flocculation tank. Therefore, in order to optimize the flocculation process, it is necessary to optimize the internal structure parameters of the flocculation tank. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and propose a method for optimizing the parameters of a baffle flocculation tank based on PIV technology.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for optimizing the parameters of a baffle flocculation tank based on PIV technology of the present invention is as follows:

[0006] Step 1: Build an experimental platform for a baffle flocculation tank. Set the initial number of blade vortex generators in the corridor equipped with blade vortex generators in the baffle flocculation tank and the angles of each arc-shaped blade on each blade vortex generator. The angle of the arc-shaped blade is represented by the included angle between the chord of the concave surface of the arc-shaped blade and the length direction of the corridor. Among them, the flocculation tank body in the baffle flocculation tank is divided into n + 1 corridors and one sedimentation tank by n corridor baffles and one sedimentation baffle arranged in sequence along the fluid direction, where n ≥ 3. And blade vortex generators are installed in the first n corridors along the fluid direction. The angles of each arc-shaped blade of each blade vortex generator are the same. The number of blade vortex generators in each corridor equipped with blade vortex generators decreases from more to less along the fluid direction, and the interval between adjacent two blade vortex generators increases from small to large along the fluid direction. The angles of each arc-shaped blade located in the same corridor are all controlled by a blade angle adjustment device.

[0007] Step 2: Set the flow rate of the raw water to be flocculated entering the flocculation tank body, conduct a flocculation test, and use a PIV system for detection. Through the analysis and calculation of the detection results, obtain the morphological parameters of the maximum energy-containing vortex in each corridor equipped with blade vortex generators, as well as the density of vortices in the blade sidewall area and the average floc diameter D. The morphological parameters include vortex scale L, Reynolds number R eL and Strouhal number S tl .

[0008] Step 3: Add the same number of blade vortex generators to each corridor equipped with blade vortex generators, and increase the angle θ of each arc-shaped blade, and then repeat Step 2.

[0009] Step 4: Repeat Step 3 until the flocculation test is completed for the preset number of times.

[0010] Step 5: Establish a mathematical model of the average floc diameter D with respect to the vortex scale L, Reynolds number R eL , Strouhal number S tl , vortex density ρ, the number of vortex generators N, and the angle θ of the arc-shaped blade according to the test results of Step 4.

[0011] Step 6: Analyze through an optimization algorithm according to the mathematical model in Step 5 to obtain the optimal number N of blade vortex generators and the angle θ of the arc-shaped blade corresponding to maximizing the average floc diameter D in each corridor equipped with blade vortex generators.

[0012] Preferably, the angles of the arc-shaped blades in each flocculation test change in an arithmetic progression with a non-zero common difference.

[0013] More preferably, the angles θ of the arc-shaped blades in each measurement test are taken as 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, and 150° in sequence.

[0014] Preferably, the partition flocculation tank is composed of a flocculation tank body, a corridor partition, a sedimentation partition, a blade vortex generator, and a blade angle adjusting device. The two ends of the flocculation tank body are respectively fixedly connected with a water inlet pipe and a water outlet pipe. Inside the flocculation tank body, n corridor partitions and one sedimentation partition are fixedly arranged at intervals along the fluid direction, where n≥3, and the sedimentation partition is closer to the water outlet pipe than each corridor partition. A plurality of diversion holes arranged in an array are formed on the sedimentation partition. Openings are formed at different ends of every two adjacent corridor partitions, and the opening of the corridor partition close to the water inlet pipe is located at a different end of the corridor partition from the water inlet pipe. The n corridor partitions and one sedimentation partition divide the flocculation tank body into n + 1 corridors and one sedimentation tank, and the sedimentation tank is communicated with the water outlet pipe. In the first n corridors along the fluid direction, there are respectively N1, N2, …, N n blades vortex generators, where N1≥N2≥L≥N n ≥2, and in each corridor provided with a blades vortex generator, the blades vortex generators are arranged at equal intervals along the length of the corridor; the blades vortex generator includes an arc-shaped blade and a bottom plate. Between two horizontally and parallelly arranged bottom plates, a plurality of vertically and equally spaced arc-shaped blades are provided. The two ends of the arc-shaped blade are respectively hinged to the two bottom plates. The bottom plate located below is detachably fixed to the bottom surface of the flocculation tank body, and the two ends of the bottom plate located above are detachably fixed to the flocculation tank body and the corridor partition or two adjacent corridor partitions. In each corridor provided with a blades vortex generator, each arc-shaped blade is synchronously driven to rotate by a blade angle adjusting device.

[0015] More preferably, the blade angle adjusting device includes a movable rod, a connecting rod, and a set of swing rods. The set of swing rods is provided with a plurality of swing rods arranged at equal intervals and is composed of a plurality of horizontally parallel and equally spaced swing rods. The movable rod is provided with a plurality of horizontally parallel and equally spaced ones. The number of the set of swing rods and the movable rod is equal to the number of the blades vortex generators in the same corridor. The number of swing rods in each set of swing rods is equal to the number of arc-shaped blades in the blades vortex generators in the same corridor. One end of each swing rod in each set of swing rods is fixed to the upper ends of each arc-shaped blade in a blades vortex generator in the same corridor, and the other end is hinged to a movable rod. Each movable rod is hinged to a connecting rod, and a plurality of vertically and spaced handles are fixed on the connecting rod.

[0016] The present invention has the following beneficial effects:

[0017] The present invention realizes the optimization of the structural parameters of the baffle flocculation tank, and the optimization result has a high accuracy. Specifically, the present invention conducts flocculation tests under different numbers of vane vortex generators and arc vane angles in the baffle flocculation tank to obtain the morphological parameters of the maximum energy-containing vortices in each corridor equipped with vane vortex generators, the density of vortices in the vane sidewall region, and the average floc diameter. Then, according to the test results, a mathematical model of the average floc diameter with respect to the morphological parameters, vortex density, number of vortex generators, and arc vane angle is established. Finally, based on the established mathematical model, an optimization algorithm is used to obtain the optimal number of vane vortex generators and arc vane angles corresponding to the maximum average floc diameter in each corridor equipped with vane vortex generators, thereby realizing the optimization of the structural parameters of the baffle flocculation tank. Further, in the present invention, a PIV system component is used for detection during the flocculation test, and the accuracy of the test results is high, which further makes the optimization result have a high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of the overall structure of the baffle flocculation tank in the present invention;

[0019] Figure 2 is a schematic diagram of the structure of the vane vortex generator and part of the vane angle adjustment device in the present invention;

[0020] Figure 3 is a schematic diagram of the structure of the PIV system component in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following further describes the present invention with reference to the drawings.

[0022] A method for optimizing the parameters of a baffle flocculation tank based on PIV technology according to the present invention is as follows:

[0023] Step 1: Build an experimental platform for the baffle flocculation tank. The experimental platform for the baffle flocculation tank consists of a baffle flocculation tank and a PIV system component. The PIV system component is used to detect the fluid flow field in the baffle flocculation tank. Set the initial number of vane vortex generators in the corridor of the baffle flocculation tank equipped with vane vortex generators and the angle of each arc vane on each vane vortex generator. The angle of the arc vane is represented by the included angle between the chord of the concave surface of the arc vane and the length direction of the corridor.

[0024] Among them, as Figure 1 and Figure 2As shown in the figure, the baffle flocculation tank is composed of a flocculation tank body 1, a corridor baffle 2, a sedimentation baffle, a vane vortex generator 5 and a vane angle adjustment device 9. The two ends of the flocculation tank body are fixedly connected with a water inlet pipe 4 and a water outlet pipe 3 respectively. Inside the flocculation tank body 1, n corridor baffles 2 and a sedimentation baffle are fixedly arranged at intervals along the fluid direction (from the water inlet pipe to the water outlet pipe), where n≥3, and the sedimentation baffle is closer to the water outlet pipe 3 than each corridor baffle 2. A plurality of diversion holes arranged in an array are opened on the sedimentation baffle. Openings are provided at different ends of every two adjacent corridor baffles 2, and the opening of the corridor baffle 2 close to the water inlet pipe 4 is at a different end from the water inlet pipe. The n corridor baffles 2 and a sedimentation baffle divide the flocculation tank body 1 into n + 1 corridors and a sedimentation tank, and the sedimentation tank is communicated with the water outlet pipe 3. In the first n corridors along the fluid direction, there are N1, N2, …, N n vane vortex generators 5 respectively, where N1≥N2≥L≥N n ≥2, and in each corridor with a vane vortex generator, the vane vortex generators are arranged at equal intervals along the length of the corridor; the vane vortex generator includes a bottom plate 6 and an arc-shaped vane 10. Between two horizontally and parallel bottom plates, a plurality of vertically and equally spaced arc-shaped vanes are provided. The two ends of the arc-shaped vane are respectively hinged to the two bottom plates. The bottom plate located below is detachably fixed to the bottom surface of the flocculation tank body, and the two ends of the bottom plate located above are detachably fixed to the flocculation tank body and the corridor baffle or two adjacent corridor baffles. In each corridor with a vane vortex generator, each arc-shaped vane is synchronously driven to rotate by a vane angle adjustment device. Among them, the number of vane vortex generators in each corridor with a vane vortex generator decreases from more to less along the fluid direction, and the interval between two adjacent vane vortex generators in each corridor increases from small to large along the fluid direction, so as to form small-scale and high-intensity vortices in the early stage of flocculation and large-scale and low-intensity vortices in the later stage, which is beneficial to flocculation.

[0025] Step 2: Set the flow rate of the raw water to be flocculated in the water inlet pipe, conduct a flocculation test, and use the PIV system components for detection. Through the analysis and calculation of the detection results, the morphological parameters of the maximum energy-containing vortices in each corridor with a vane vortex generator and the density ρ of the vortices in the vane sidewall area and the average diameter D of the flocs are obtained. The morphological parameters include the vortex scale L, the Reynolds number R eL and the Strouhal number S tl . Among them, as Figure 3As shown in the figure, the components of the PIV system include a computer, a CCD (charge-coupled device), a synchronizer, a laser, an optical arm, and optical elements. The computer is used to control the test process, process image data, and analyze the results. The CCD is an image sensor used to capture images of the experimental area (the image of the fluid flow area in the baffle flocculation tank, where tracer particles are scattered). The synchronizer is used to synchronize the laser and the CCD to ensure that images are captured at the appropriate moment. The laser is used to generate laser light to illuminate the tracer particles in the experimental area. The optical arm is the path for guiding the laser beam. The optical elements include lenses and mirrors, which are used to adjust the properties and path of the laser beam.

[0026] Step 3: Add the same number of blade vortex generators to each corridor equipped with blade vortex generators, and increase the angle θ of each arc-shaped blade, and then repeat Step 2.

[0027] Step 4: Repeat Step 3 until the flocculation test is completed for a preset number of times. Among them, the arc-shaped blade angles in each flocculation test change in an arithmetic progression with a non-zero common difference. In this embodiment, the angles θ of the arc-shaped blades in each measurement test are taken as 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, and 150° in sequence.

[0028] Step 5: Establish a mathematical model of the average floc diameter D with respect to the vortex scale L, Reynolds number R eL , Strouhal number S tl , vortex density ρ, the number N of vortex generators, and the arc-shaped blade angle θ.

[0029] Step 6: Analyze through an optimization algorithm according to the mathematical model in Step 5 to obtain the optimal number N of blade vortex generators and the arc-shaped blade angle θ corresponding to maximizing the average floc diameter D in each corridor equipped with blade vortex generators.

[0030] As a preferred embodiment, the blade angle adjusting device 9 includes a connecting rod 7, a movable rod 11, and a set of swing rods. The set of swing rods is provided with a plurality of equally spaced ones and is composed of a plurality of horizontally parallel and equally spaced swing rods. The movable rod 11 is provided with a plurality of horizontally parallel and equally spaced ones. The number of the set of swing rods and the movable rod 11 is equal to the number of blade vortex generators 5 in the same corridor. The number of swing rods in each set of swing rods is equal to the number of arc-shaped blades in the blade vortex generators 5 in the same corridor. One end of each swing rod in each set of swing rods is fixed to the upper ends of the arc-shaped blades of one blade vortex generator 5 in the same corridor, and the other ends are all hinged to a movable rod 11. Each movable rod 11 is hinged to a connecting rod 7. A plurality of vertically and spaced handles 8 are fixed on the connecting rod 7.

Claims

1. A method for optimizing the parameters of a baffle flocculation tank based on PIV technology, characterized in that: The details are as follows: Step 1: Build an experimental platform for a baffle flocculation tank. Set the initial number of blade vortex generators in the corridor with blade vortex generators in the baffle flocculation tank and the angles of each arc-shaped blade on each blade vortex generator. The angle of the arc-shaped blade is represented by the included angle between the chord of the concave surface of the arc-shaped blade and the length direction of the corridor. Among them, the flocculation tank body in the baffle flocculation tank is divided into n + 1 corridors and a sedimentation tank by n corridor baffles and one sedimentation baffle arranged in sequence along the fluid direction, where n ≥ 3. And blade vortex generators are installed in the first n corridors along the fluid direction. The angles of each arc-shaped blade of each blade vortex generator are the same. The number of blade vortex generators in the corridors with blade vortex generators decreases from more to less along the fluid direction, and the interval between adjacent two blade vortex generators increases from small to large along the fluid direction. The angles of each arc-shaped blade in the same corridor are all controlled by a blade angle adjusting device. Step 2: Set the flow rate of the raw water to be flocculated entering the flocculation tank body, conduct flocculation tests, and use the PIV system components for detection. Through the analysis and calculation of the detection results, obtain the morphological parameters of the maximum energy-containing vortices in each corridor equipped with blade vortex generators, as well as the density ρ of the vortices in the blade sidewall region and the average diameter D of the flocs. The morphological parameters include the vortex scale L, the Reynolds number R eL and the Strouhal number S tl ; Step 3: Add the same number of blade vortex generators to each corridor with blade vortex generators, and increase the angle θ of each arc-shaped blade, and then repeat Step 2. Step 4: Repeat Step 3 until the flocculation test is completed for the preset number of times. Step 5. Establish a mathematical model for the average diameter D of flocs, the vortex scale L, the Reynolds number R eL , the Strouhal number S tl , the vortex density ρ, the number N of vortex generators, and the angle θ of the arc-shaped blade; Step 6: Analyze through an optimization algorithm according to the mathematical model in Step 5 to obtain the optimal number N of blade vortex generators and the arc-shaped blade angle θ corresponding to the maximum average diameter D of the flocs in each corridor with blade vortex generators.

2. The parameter optimization method of a baffle flocculation tank implemented based on PIV technology according to claim 1, wherein: The arc-shaped blade angles in each flocculation test change in an arithmetic progression with a non-zero common difference.

3. The parameter optimization method for a baffle flocculation tank implemented based on PIV technology according to claim 2, characterized in that: In each measurement test, the angle θ of the arc-shaped blade takes 15°, 30°, 45°, 60°, 75°, 90°, 105°, 120°, 135°, and 150° in sequence.

4. A method for optimizing the parameters of a baffle flocculation tank implemented based on PIV technology according to claim 1, characterized in that: The partition flocculation tank is composed of a flocculation tank body, a corridor partition, a sedimentation partition, a blade vortex generator, and a blade angle adjustment device. The two ends of the flocculation tank body are fixedly connected with a water inlet pipe and a water outlet pipe respectively. Inside the flocculation tank body, n corridor partitions and one sedimentation partition are fixedly arranged at intervals along the fluid direction, where n≥3, and the sedimentation partition is closer to the water outlet pipe than each corridor partition. A plurality of diversion holes arranged in an array are formed on the sedimentation partition. Openings are formed at different ends of every two adjacent corridor partitions, and the opening of the corridor partition close to the water inlet pipe is at a different end of the corridor partition from the water inlet pipe. The n corridor partitions and one sedimentation partition divide the flocculation tank body into n + 1 corridors and one sedimentation tank, and the sedimentation tank is communicated with the water outlet pipe. In the first n corridors along the fluid direction, there are N1, N2, …, N n blade vortex generators respectively, where N1≥N2≥L≥N n ≥2, and in each corridor where there is a blade vortex generator, the blade vortex generators are arranged at equal intervals along the length of the corridor; the blade vortex generator includes an arc-shaped blade and a bottom plate. Between two horizontally and parallel bottom plates, a plurality of vertically and equally spaced arc-shaped blades are arranged. The two ends of the arc-shaped blade are respectively hinged to the two bottom plates. The bottom plate located below is detachably fixed to the bottom surface of the flocculation tank body, and the two ends of the bottom plate located above are detachably fixed to the flocculation tank body and the corridor partition or two adjacent corridor partitions. In each corridor where there is a blade vortex generator, each arc-shaped blade is synchronously driven to rotate by a blade angle adjustment device.

5. The parameter optimization method of a baffle flocculation tank implemented based on PIV technology according to claim 4, characterized in that: The blade angle adjusting device includes a movable rod, a connecting rod, and a set of swing rods. There are multiple sets of swing rods arranged at equal distances, and each set is composed of multiple swing rods arranged horizontally, parallel, and at equal distances. There are multiple movable rods arranged horizontally, parallel, and at equal distances. The number of sets of swing rods and movable rods is equal to the number of blade vortex generators in the same corridor. The number of swing rods in each set of swing rods is equal to the number of arc-shaped blades in the blade vortex generators in the same corridor. One end of each swing rod in each set of swing rods is fixed to the upper ends of each arc-shaped blade in a blade vortex generator in the same corridor, and the other end is hinged to a movable rod. Each movable rod is hinged to a connecting rod, and several vertically arranged and spaced handles are fixed on the connecting rod.

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