Device and method for visualizing flow field in nozzle based on Reynolds experiment

Abstract

The invention relates to a nozzle internal flow field visualization device and method based on a Reynolds experiment, and the device comprises a transparent nozzle, a liquid container, a pressure sensor, a high-speed camera and a processor, and the side part, close to the water inlet end of the transparent nozzle, of the transparent nozzle is provided with at least one interface and / or is connected with at least one needle tube. Colored liquid communicated with the connector or the needle tube is arranged in the liquid container, the pressure sensor is used for monitoring the internal pressure of the liquid container and feeding back the internal pressure to the processor, the colored liquid is sprayed out of the transparent spray head along the water flow track, and the high-speed camera captures a flow line of a flow field in the transparent spray head. The processor calculates the flow velocity of the fluid in the transparent nozzle in real time based on the internal pressure of the liquid container and the density of the colored liquid, visualization of a flow field and fluid flow lines in the nozzle can be achieved, the flow velocity can be measured simply, efficiently and accurately at low cost, and the flow lines and the flow velocity of the fluid at different radial positions in the transparent nozzle can be observed. The system has the characteristics of simple structure, low cost, strong real-time performance and easiness in maintenance.

Description

Technical Field

[0001] The present invention belongs to the technical field of visualization testing of the nozzle flow field, and particularly relates to a visualization device and method for the internal flow field of a nozzle based on the Reynolds experiment. Background Art

[0002] The research on the visualization of the nozzle flow field is an important field in fluid mechanics and engineering applications. By visualizing the flow velocity and flow field inside the nozzle, the flow path, velocity distribution, and vortex phenomena of the fluid inside the nozzle can be directly observed, which can be used to optimize the design of irrigation nozzles, improve the nozzle performance, verify and improve the theoretical models of fluid mechanics, etc. The existing visualization methods for the nozzle flow field include Particle Image Velocimetry (PIV), Laser Induced Fluorescence (LIF), high-speed photography technology, etc. PIV obtains the flow field velocity distribution by tracking the movement of tiny particles in the fluid, and LIF studies the fluid mixing and concentration distribution by adding fluorescent dyes to the fluid and irradiating with a laser to observe the fluorescence response. However, the experimental devices of traditional PIV and LIF methods are complex, have high requirements for data processing, and are costly to use and maintain. In contrast, although high-speed photography has the advantages of extremely high resolution, strong intuitiveness, and relatively simple operation, the existing high-speed photography technology mainly uses high-speed cameras to capture and record fast-changing phenomena such as spray, jet, and bubble dynamics, and it is still impossible to see the internal flow field and fluid streamlines of the nozzle. Therefore, it is necessary to develop a visualization device and method for the internal flow field of a nozzle, which can not only visualize the internal flow field and flow velocity of the nozzle, but also simplify the experimental device, reduce the experimental and maintenance costs, and provide an intuitive means for researchers to deeply explore the laws of fluid motion.

[0003] The Reynolds experiment is a fluid mechanics experiment that studies the flow states of fluids under different conditions and their transitions. It mainly consists of a water tank, a glass tube, a container for colored liquid, a valve, etc. The water tank is used to provide a stable water flow, the glass tube is the channel for the water flow, and the container for colored liquid is connected to the glass tube through a thin tube, and the colored liquid can be injected into the water flow to observe the behavior of the water flow in the glass tube. However, compared with the glass tube, the internal space structure size of the nozzle application scenario is usually small, and the fluid flow velocity inside the nozzle is usually high. While the traditional method usually directly measures the flow velocity using an optical sensor or a flowmeter, on the one hand, the structure of the flowmeter is complex, which leads to problems such as complex equipment, high cost, or interference with fluid flow in the measurement of the flow velocity, and direct application will affect the visualization of the internal flow field streamlines of the nozzle and the measurement accuracy. On the other hand, in order to deeply understand the complex characteristics of the nozzle flow field, reveal the internal laws of the flow field, and provide experimental support for theoretical research and nozzle optimization design, it is also necessary to measure the flow rate and flow velocity at different positions. The existing flow measurement devices and methods can only measure the flow velocity in the flow channel and are not convenient for measuring the flow velocity at different positions of the internal jet of the nozzle, which brings challenges to the analysis of complex flow states. Summary of the Invention

[0004] The present invention aims to solve at least one of the above technical problems to some extent. The present invention provides a visualization device and method for the internal flow field of a nozzle based on the Reynolds experiment, which can realize the visualization of the internal flow field and fluid streamlines of the nozzle, has a simple structure, low cost, strong real-time performance, and is easy to maintain. At the same time, it can measure the flow velocity simply, efficiently, accurately, and at low cost, providing an intuitive means for R & D personnel to deeply explore the laws of fluid motion.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0006] A visualization device for the internal flow field of a nozzle based on the Reynolds experiment includes a transparent nozzle, a liquid container, a pressure sensor, a high-speed camera, and a processor. The transparent nozzle is connected to a water inlet device. At least one interface is provided on the side of the transparent nozzle near the water inlet end and / or at least one syringe is connected. A colored liquid is provided in the liquid container and is communicated with the interface or the syringe. The pressure sensor is used to monitor the internal pressure of the liquid container and feedback it to the processor. The viewing range of the high-speed camera covers the entire internal flow field of the transparent nozzle. The processor is used to calculate the fluid flow velocity in the transparent nozzle based on the internal pressure of the liquid container and the density of the colored liquid.

[0007] In a preferred technical solution, the water inlet device includes a water tank, a water inlet pipe connecting the water tank and the transparent nozzle. A water pump, a flow meter, and a first valve are provided on the water inlet pipe. Water can be pumped by the water pump, and the flow rate and pressure of the water pump can be adjusted by the flow meter to meet the preset values. The flow rate and pressure settings of the nozzle can be adjusted by the valve to ensure that the transparent nozzle is set under predetermined working conditions.

[0008] In a preferred technical solution, there are multiple interfaces. The multiple interfaces are arranged at intervals circumferentially around the transparent nozzle. The specific number and position of the interfaces can be set according to requirements to measure the streamlines and fluid flow velocities at different radial positions inside the transparent nozzle.

[0009] In a preferred technical solution, the transparent nozzle is provided with an annular disc, and multiple interfaces are arranged at intervals on the annular disc, which is more convenient for the manufacture and assembly of the transparent nozzle.

[0010] In a preferred technical solution, the transparent nozzle is slidably connected to the syringe. An adjusting mechanism is provided on the liquid container. The adjusting mechanism is used to drive the syringe to reciprocate radially along the transparent nozzle and adjust the depth of insertion of the syringe into the transparent nozzle to measure the streamlines and fluid flow velocities at different radial positions inside the transparent nozzle.

[0011] In a preferred technical solution, a second valve is provided between the liquid container and the interface or between the liquid container and the syringe. The second valve can adopt a one-way flow valve, which is used to control the flow rate of the colored liquid entering the transparent nozzle and can be closed when replacing the liquid container.

[0012] In a preferred technical solution, the liquid container is transparent and is provided with scales for directly observing the amount of colored liquid in the liquid container so as to replenish the colored liquid in a timely manner.

[0013] In a preferred technical solution, a hydrodynamic model of the liquid container - nozzle system is established based on Bernoulli's equation, and the processor is used to, according to the hydrodynamic model: calculate the fluid flow velocity in the transparent nozzle. In the formula, P1 is the internal pressure of the liquid container measured by the pressure sensor (Pa), ρ is the density of the colored liquid (kg / m 3 ³), and v2 is the fluid flow velocity in the transparent nozzle (m / s).

[0014] A method for visualizing the internal flow field of a nozzle based on the Reynolds experiment. Based on the device for visualizing the internal flow field of a nozzle based on the Reynolds experiment described in any one of the above, the method includes:

[0015] Supply water to the transparent nozzle through the water inlet device so that the colored liquid is ejected from the transparent nozzle along the water flow trajectory. Capture the streamlines of the internal flow field of the transparent nozzle through a high - speed camera and store them. The processor calculates the fluid flow velocity in the transparent nozzle in real - time based on the internal pressure of the liquid container and the density of the colored liquid.

[0016] In a preferred technical solution, the transparent nozzle is manufactured by 3D - printing photocurable resin, and the refractive index difference between the transparent nozzle and the colored liquid is ≤0.2.

[0017] In a preferred technical solution, the wall - thickness tolerance of the transparent nozzle is ±0.05 mm.

[0018] In a preferred technical solution, the light transmittance of the photocurable resin is ≥90%, and the haze is ≤5%.

[0019] In a preferred technical solution, the colored liquid is ink.

[0020] In a preferred technical solution, by connecting the liquid container to interfaces at different positions, observe the streamlines and fluid flow velocities at different radial positions in the transparent nozzle.

[0021] In a preferred technical solution, by adjusting the depth of insertion of the syringe along the radial direction of the transparent nozzle into the transparent nozzle, observe the streamlines and fluid flow velocities at different radial positions in the transparent nozzle.

[0022] The application of the above - mentioned method for visualizing the internal flow field of a nozzle based on the Reynolds experiment includes combining the streamlines of the internal flow field of the transparent nozzle recorded by the high - speed camera and the fluid flow velocity in the transparent nozzle recorded by the processor to evaluate the nozzle performance and flow velocity, and adjusting the settings of the transparent nozzle or the working state of the water pump when necessary.

[0023] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0024] (1) Based on the Reynolds experiment, the present invention sprays a colored liquid along the flow path from a transparent nozzle, and combines a high-speed camera to capture the streamlines of the internal flow field of the transparent nozzle. Compared with the traditional PIV and LIF methods, the high-speed camera has lower cost and is easier to maintain, with simple structure, low cost, and strong real-time performance. At the same time, it solves the problem that the internal flow field cannot be seen in the traditional nozzle experiment, providing an intuitive means for researchers to deeply explore the laws of fluid motion.

[0025] (2) The present invention uses a high-precision pressure sensor to real-time monitor the internal pressure of the liquid container. The processor can calculate the fluid velocity inside the transparent nozzle based on the internal pressure of the liquid container and the density of the colored liquid, and establish a fluid mechanics model and measure the fluid velocity inside the transparent nozzle based on the Bernoulli equation. Only a single pressure sensor is required, without additional flow measurement devices, reducing the system complexity, and solving the problems of high system complexity, large measurement interference, and high cost caused by the use of flow meters or optical sensors in the prior art. It can measure the flow velocity simply, efficiently, accurately, and at low cost.

[0026] (3) The present invention provides a dual-mode observation scheme: through a non-invasive design in which the liquid container is connected to interfaces at different positions, or by adjusting the depth of the syringe inserted radially into the transparent nozzle along the transparent nozzle, it not only avoids the interference of flow velocity measurement on the flow of the colored liquid and improves the measurement accuracy, but also can observe the streamlines and fluid velocities at different radial positions inside the transparent nozzle, which is applicable to fields such as the optimization of nozzles for irrigation and industrial inkjet devices, is conducive to significantly reducing the hardware cost, and has good market application prospects. Description of the Drawings

[0027] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0028] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0029] Figure 2 is a mark of the cross-sectional area and height difference between the transparent nozzle and the liquid container in Embodiment 1 of the present invention;

[0030] Figure 3 is a top view of the annular wheel in Embodiment 1 of the present invention;

[0031] Figure 4 is a front view of the annular wheel in Embodiment 1 of the present invention;

[0032] Figure 5 is a schematic structural diagram of the liquid container in Embodiment 1 of the present invention;

[0033] Figure 6 is an effect diagram of the simulated streamlines in the simulation experiment of Embodiment 2 of the present invention;

[0034] Reference signs in the figure: water tank 1, water pump 2, flowmeter 3, first valve 4, annular disc 5, interfaces 501, 502, transparent nozzle 6, syringe 7, liquid container 8, high-speed camera 9, processor 10, water inlet pipe 11, slider 801, sliding hole 802, second valve 803, scale 804, colored liquid 805, pressure sensor 806; A1 is the cross-sectional area of the liquid container, A2 is the cross-sectional area of the transparent nozzle, h1 is the height of the transparent nozzle, and h2 is the height of the liquid container. Detailed implementation mode

[0035] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0036] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by terms such as "height", "thickness", "upper", "lower", "radial", "vertical", "horizontal", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "plurality" and "several" is two or more, unless otherwise specifically defined.

[0037] In the present invention, unless otherwise clearly specified and defined, terms such as "connected", "connected to", "fixed" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0038] Embodiment 1:

[0039] As Figure 1As shown, a preferred embodiment of the visualization device for the internal flow field of the nozzle based on the Reynolds experiment of the present invention is provided. The visualization device for the internal flow field of the nozzle based on the Reynolds experiment includes a transparent nozzle 6, a liquid container 8, a pressure sensor 806, a high-speed camera 9, and a processor 10. The transparent nozzle 6 is connected to a water inlet device. At least one interface 501 is provided on the side of the transparent nozzle 6 near the water inlet end and / or at least one syringe 7 is connected. A colored liquid 805 communicating with the interface 501 or the syringe 7 is provided in the liquid container 8. The pressure sensor 806 is used to monitor the internal pressure of the liquid container 8 and feedback it to the processor 10. The viewing range of the high-speed camera 9 covers the entire internal flow field of the transparent nozzle 6. The processor 10 is used to calculate the fluid velocity in the transparent nozzle 6 based on the internal pressure of the liquid container 8 and the density of the colored liquid 805.

[0040] Aiming at the problems of the complex experimental devices, high requirements for data processing, high use and maintenance costs of the traditional PIV and LIF methods, the above device is designed based on the Reynolds experiment. It can supply water to the transparent nozzle 6 through the water inlet device, so that the colored liquid 805 is ejected from the transparent nozzle 6 along the water flow trajectory. The high-speed camera 9 captures the streamlines of the internal flow field of the transparent nozzle 6 and stores them. The processor 10 calculates the fluid velocity in the transparent nozzle 6 in real time based on the internal pressure of the liquid container 8 and the density of the colored liquid 805. The high-speed camera 9 can capture transient phenomena within an extremely short time and record thousands or even millions of frames of images per second. The operation is relatively simple. By ejecting the colored liquid 805 from the transparent nozzle 6 along the water flow trajectory, the internal streamlines of the nozzle can be observed without using PIV. The device structure is simplified, the cost is lower, and it is easy to maintain. It also solves the problem that the existing high-speed camera 9 cannot see the internal flow field of the nozzle and the visualization of fluid streamlines.

[0041] On this basis, by monitoring the internal pressure of the liquid container 8 with the pressure sensor 806 and feedbacking it to the processor 10, an indirect flow velocity measurement structure based on the change of the internal pressure of the liquid container 8 and the density of the colored liquid 805 is proposed. Only a single pressure sensor 806 is required, and no additional flow measurement device is needed, which can reduce the system complexity, avoid the interference of the traditional flowmeter 3 on the flow of the colored liquid 805, avoid affecting the visualization monitoring of the internal flow field streamlines of the nozzle, and improve the measurement accuracy and data reliability; only one interface 501 or only one syringe 7 can be used. By connecting the interface 501 to the liquid container 8 or connecting the syringe 7 to the liquid container 8, the fluid velocity in the transparent nozzle 6 can be obtained; the interface 501 and the syringe 7 can be used simultaneously, or multiple interfaces 501 at different positions, or multiple syringes 7 at different positions. By connecting the liquid container 8 to the interfaces 501 and syringes 7 at different positions, the streamlines and fluid velocities at different radial positions in the transparent nozzle 6 can be observed, and the flow velocity can be measured simply, efficiently, accurately, and at low cost, providing an intuitive means for researchers to deeply explore the laws of fluid motion.

[0042] Further, the water inlet device includes a water tank 1 and a water inlet pipe 11 connecting the water tank 1 and the transparent nozzle 6. A water pump 2, a flow meter 3, and a first valve 4 are provided on the water inlet pipe 11. Water can be pumped by the water pump 2. For example: as Figure 1 shown, the water tank 1, the water pump 2, the flow meter 3, the first valve 4, and the transparent nozzle 6 are sequentially connected through the water inlet pipe 11. Then, the water pump 2 can pump the water in the water tank 1 into the transparent nozzle 6 through the water inlet pipe 11 and spray it out. According to the research conditions of the internal flow field of the nozzle, during the process, the flow rate and pressure of the water pump 2 are adjusted by the flow meter 3 to meet the preset values, and the flow rate and pressure of the nozzle are set by the valve to ensure that the transparent nozzle 6 is set under the predetermined working conditions.

[0043] Further, the high-speed camera 9 is supported on the ground by a bracket. For example: as Figure 1 shown, the high-speed camera 9 is installed in front of the transparent nozzle 6 through a bracket and aligned with the transparent nozzle 6 to ensure that the viewing range of the high-speed camera 9 covers the entire internal flow field of the transparent nozzle 6. The processor 10 uses a computer, and the colored liquid 805 uses ink. The signals of the high-speed camera 9 and the pressure sensor 806 are connected to the computer, and the computer records the flow trajectory of the ink line inside the transparent nozzle 6 obtained by the high-speed camera 9. According to the feedback of the pressure sensor 806, the fluid flow rate inside the transparent nozzle 6 is calculated in real time, that is, the water flow rate of the internal flow field of the nozzle is obtained, which has the characteristics of high time resolution, simple and intuitive, low cost, and easy to maintain.

[0044] Further, there are multiple interfaces 501. The multiple interfaces 501 are circumferentially spaced around the transparent nozzle 6. The specific number and position of the interfaces 501 can be set according to requirements to measure the streamlines and fluid flow rates at different radial positions inside the transparent nozzle 6. Multiple interfaces 501 can be formed by opening holes at corresponding positions on the side of the transparent nozzle 6, or as Figure 1 、 Figure 3 and Figure 4 shown, the transparent nozzle 6 is provided with an annular disk 5. The annular disk 5 is a separately processed pipe fitting. Multiple interfaces 501 are spaced on the annular disk 5. The annular disk 5 can be assembled with the outlet end of the water inlet pipe 11 and the lower part of the main body of the transparent nozzle 6 through 502, which is more convenient for the manufacture and assembly of the transparent nozzle 6. By connecting the liquid container 8 to the interfaces 501 at different positions, the streamlines and fluid flow rates at different radial positions inside the transparent nozzle 6 are observed. This non-invasive design, compared with inserting the syringe needle 7 into the nozzle, does not need to change the nozzle model, the nozzle type can be replaced at any time, and it can further avoid interfering with the flow of the colored liquid 805 and improve the measurement accuracy.

[0045] Further, the transparent nozzle 6 is slidably connected to the syringe needle 7, and an adjusting mechanism is provided on the liquid container 8. The adjusting mechanism is used to drive the syringe needle 7 to reciprocate radially with respect to the transparent nozzle 6 and adjust the depth of insertion of the syringe needle 7 into the transparent nozzle 6. For example, as Figure 2 , Figure 5 shown, one end of the syringe needle 7 can be inserted into the transparent nozzle 6, and the other end of the syringe needle 7 is inserted into the liquid container 8. The adjusting mechanism is a slider 801. A sliding hole 802 is provided on the liquid container 8 along the radial direction of the transparent nozzle 6. One end of the slider 801 is connected to the syringe needle 7, and the other end of the slider 801 extends out of the sliding hole 802. Then, the slider 801 can be pushed to slide along the sliding hole 802 to adjust the depth of insertion of the syringe needle 7 into the transparent nozzle 6, and change the position where the colored solution accesses the transparent nozzle 6, so as to measure the streamlines and fluid flow velocities at different radial positions inside the transparent nozzle 6. Since the syringe needle 7 is relatively small in size compared to the nozzle and the position inserted into the lower end of the transparent nozzle 6 is relatively concealed, it is not directly exposed in the main flow field of the transparent nozzle 6 like the flowmeter 3 such as a Pitot tube, thus ensuring the stability of the main streamline of the transparent nozzle 6, and further increasing the flexibility and efficiency of observation and debugging compared to the interface 501 structure.

[0046] Further, a second valve 803 is provided between the liquid container 8 and the interface 501 or between the liquid container 8 and the syringe needle 7. For example, as Figure 5 shown, the second valve 803 can be a one-way flow valve, which is used to control the flow rate of the colored liquid 805 entering the transparent nozzle 6. The colored liquid 805 enters the transparent nozzle 6 due to the concentration difference between the internal and external liquids, and this process is controllable. The second valve 803 can be closed when replacing the liquid container 8.

[0047] Further, the liquid container 8 is transparent, and a scale 804 is provided on the liquid container 8. For example, as Figure 5 shown, the scale 804 can be used to directly observe the amount of the colored liquid 805 in the liquid container 8, so as to replenish the colored liquid 805 in a timely manner.

[0048] Further, a hydrodynamic model of the liquid container 8 - nozzle system is established based on the Bernoulli equation, and a mathematical relationship between pressure and flow velocity is established through theoretical derivation. The processor 10 is used to calculate the fluid flow velocity inside the transparent nozzle 6 according to the hydrodynamic model: where P1 is the internal pressure of the liquid container 8 measured by the pressure sensor 806 (Pa), ρ is the density of the colored liquid 805 (kg / m 3 ), and v2 is the fluid flow velocity inside the transparent nozzle 6 (m / s 3 ).

[0049] To make the technical solution of the present invention clearer, the following is for the hydrodynamic model: Provide a more detailed explanation of the derivation process, covering the basic theories of fluid mechanics, the physical basis of the assumptions, and the complete steps of the mathematical derivation:

[0050] For an incompressible fluid with a constant density ρ, in steady-state flow, the Bernoulli equation describes the conservation of energy, and the mass flow rate through any cross-section is equal. Thus, we have: A1v1 = A2v2; where A1 is the cross-sectional area of the liquid container 8 (m 2 ), A2 is the cross-sectional area of the transparent nozzle 6 (m 2 ), v1 is the flow velocity of the colored liquid 805 in the liquid container 8 (m / s), and v2 is the flow velocity of the fluid in the transparent nozzle 6 (m / s).

[0051] Since the cross-sectional area A1 of the liquid container 8 is much larger than the cross-sectional area A2 of the transparent nozzle 6, according to the continuity equation, the flow velocity v1 of the colored liquid 805 in the liquid container 8 is much smaller than the flow velocity v2 of the fluid in the transparent nozzle 6, and it can be approximated as v1 ≈ 0.

[0052] Describe the conservation of mechanical energy of an ideal fluid along a streamline using the Bernoulli equation:

[0053]

[0054] Among them: In the formula, P1 is the internal pressure of the liquid container 8 measured by the pressure sensor 806 (Pa), ρ is the density of the colored liquid 805 (kg / m 3 ), v1 is the flow velocity of the colored liquid 805 in the liquid container 8 (m / s), v1 is approximately equal to 0, P2 is the outlet pressure of the transparent nozzle 6 (Pa), which is close to the atmospheric pressure and can be ignored, v2 is the flow velocity of the fluid in the transparent nozzle 6 (m / s), as Figure 2 shown, h1 is the height of the transparent nozzle 6 (m), h2 is the height of the liquid container 8 (m), ΔP loss is the pressure loss caused by viscous resistance (Pa), and ΔP loss can be ignored in short-distance and low-viscosity fluids.

[0055] Substitute the assumed conditions to obtain:

[0056] When the height difference Δh between the transparent nozzle 6 and the liquid container 8 is small, the gravitational potential energy term ρgΔh is much smaller than the pressure energy term P1, that is, Δh = h1 - h2 ≈ 0, and the equation is simplified to: Simplify the equation to obtain the calculation formula for the flow velocity v2 of the fluid in the transparent nozzle 6: Among them, P1 is the internal pressure of the liquid container 8 measured by the pressure sensor 806 (Pa), ρ is the density of the colored liquid 805 (kg / m 3 ), and v2 is the flow velocity of the fluid in the transparent nozzle 6 (m / s).

[0057] The pressure inside the liquid container is monitored in real time through a single-point pressure sensor 806. For example, the pressure sensor 806 is installed at the inner bottom of the liquid container 8. By combining with a fluid mechanics model to calculate the fluid velocity inside the transparent nozzle 6, the fluid velocity inside the transparent nozzle 6 can be continuously measured without affecting the visualization observation of the internal flow field of the transparent nozzle 6. It has the advantages of simple structure, low cost, and strong real-time performance. The calculation process is simple and efficient. Combining with high-speed photography for fluid streamline recording, it meets the conditions of visualizing the internal flow field and fluid velocity with relatively low cost, and can significantly reduce the hardware cost.

[0058] Embodiment 2:

[0059] A preferred implementation manner of the method for visualizing the internal flow field of the nozzle based on the Reynolds experiment of the present invention. Based on the device for visualizing the internal flow field of the nozzle based on the Reynolds experiment described in Embodiment 1, the method includes the following steps:

[0060] Step 1. Debugging before observation. Specifically:

[0061] The transparent nozzle 6 is manufactured by 3D printing photocurable resin, and the refractive index difference between the transparent nozzle 6 and the colored liquid 805 is ≤0.2. For example, the light transmittance of the photocurable resin is ≥90%, and the haze is ≤5%. A rocker nozzle is selected as the experimental nozzle, and the wall thickness tolerance of the rocker nozzle is ±0.05 mm.

[0062] Water is injected into the water tank 1, the water pump 2 is turned on and the working state of the water pump 2 is gradually adjusted to reach the required water flow rate. Through the flowmeter 3, it is ensured that the flow rate and pressure of the water pump 2 meet the preset values. The first valve 4 is used to adjust the flow rate and pressure settings of the transparent nozzle 6 to ensure that the transparent nozzle 6 is set under the predetermined working conditions.

[0063] Taking the colored liquid 805 as ink as an example, the ink is filled into the liquid container 8 for providing ink lines. There are two ways to provide ink lines. One is: connecting the syringe 7 with the liquid container 8, and the syringe 7 is inserted into the side of the transparent nozzle 6 from near the water inlet end of the transparent nozzle 6; the other is: opening a hole on the side of the transparent nozzle 6 near the water inlet end or forming an interface 501 by the annular wheel 5, connecting the interface 501 with the liquid container 8, and ensuring that the syringe 7 and the liquid container 8 are correctly installed.

[0064] The high-speed camera 9 is installed in front of the nozzle and aligned with the transparent nozzle 6 to ensure that the viewing range of the high-speed camera 9 covers the entire internal flow field of the transparent nozzle 6, and a suitable frame rate is set, with the number of frames per second ≥1000 fps; using a computer as the processor 10, connecting the computer with the high-speed camera 9, connecting the computer with the pressure sensor 806, and setting a fluid mechanics model in the computer:

[0065] Step 2: Supply water to the transparent nozzle 6 through the water inlet device, so that the colored liquid 805 is ejected from the transparent nozzle 6 along the water flow trajectory. Capture the streamline of the internal flow field of the transparent nozzle 6 with the high-speed camera 9 and store it. The processor 10 calculates the fluid velocity inside the transparent nozzle 6 in real time based on the internal pressure of the liquid container 8 and the density of the colored liquid 805. Specifically:

[0066] Start the visualization device for the internal flow field of the nozzle based on the Reynolds experiment. When the transparent nozzle 6 is working properly, the ink line flows out of the transparent nozzle 6 along the water flow trajectory. Record the flow trajectory of the ink line inside the transparent nozzle 6 with the high-speed camera 9 and feedback it to the computer. The pressure sensor 806 accurately measures the pressure change inside the liquid container 8. As the ink line is ejected with the water flow, transmit the real-time data of the internal pressure of the liquid container 8 to the computer. The computer calculates the fluid velocity inside the transparent nozzle 6 in the current state according to the fluid mechanics model.

[0067] Provide a dual-mode observation scheme: After one test, by changing the connection position of the liquid container 8, that is, connecting the liquid container 8 to the interfaces 501 at different positions, the ink line can enter the inside of the transparent nozzle 6 from different radial positions of the transparent nozzle 6, and observe the streamline and fluid velocity inside the transparent nozzle 6 in each state respectively. That is, measure the ink lines at different positions inside the transparent nozzle 6. After recording, storing and summarizing, the streamline and fluid velocity at different radial positions inside the transparent nozzle 6 can be obtained.

[0068] Or after one test, by adjusting the depth of the syringe 7 inserted into the transparent nozzle 6 along the radial direction of the transparent nozzle 6, the ink line can enter the inside of the transparent nozzle 6 from different radial positions of the transparent nozzle 6, and observe the streamline and fluid velocity inside the transparent nozzle 6 in each state respectively. That is, measure the ink lines at different positions inside the transparent nozzle 6. After recording, storing and summarizing, the streamline and fluid velocity at different radial positions inside the transparent nozzle 6 can be obtained.

[0069] To further verify the feasibility of the visualization method for the internal flow field of the nozzle based on the Reynolds experiment, a simulation experiment on the internal flow field of the nozzle was carried out based on CFD. The standard turbulence model was used to capture the vortex structure inside the nozzle. Virtual tracer particles were injected 10 mm upstream of the outlet to simulate the ink injection of the syringe 7. The flow trajectory was displayed through trace rendering, and the Figure 6 simulation experiment simulation streamline effect diagram as shown was obtained. It can be seen from Figure 6 that with the help of the trace rendering technology, the flow trajectory of the particles inside the nozzle is clearly presented, which proves the feasibility of the visualization device and method for the internal flow field of the nozzle based on the Reynolds experiment. Through the analysis of the simulation results, it is proved that the assumption that the outlet pressure P2≈0 of the transparent nozzle 6 is reasonable.

[0070] The above-mentioned visualization method of the internal flow field of the nozzle based on the Reynolds experiment can effectively solve the problems that the internal flow field of traditional nozzles cannot be seen and the cost of tracer particles such as PIV is high, and can effectively improve the flow velocity measurement accuracy, and grasp the performance and efficiency of the nozzle during operation in real time, so as to provide an important basis for improving the main performance indicators of the nozzle such as the spraying range.

[0071] The application of the above-mentioned visualization method of the internal flow field of the nozzle based on the Reynolds experiment includes combining the streamline of the internal flow field of the transparent nozzle 6 recorded by the high-speed camera 9 and the fluid flow velocity in the transparent nozzle 6 recorded by the processor 10 to evaluate the nozzle performance and flow velocity; for example: in an inkjet printing or microfluidic injection system, accurately controlling the ink injection speed is crucial for printing quality or fluid manipulation. With the visualization method of the internal flow field of the nozzle based on the Reynolds experiment, the clear streamline recorded by the high-speed camera can intuitively judge whether there is turbulence or abnormal flow of the ink inside the nozzle, avoid uneven ink droplet sizes caused by flow disorders, and evaluate the nozzle flow velocity by measuring the streamline and flow velocity at different positions of the internal jet of the nozzle, which can provide a quantitative basis for adjusting printing parameters and optimizing the nozzle design of industrial inkjet devices.

[0072] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for visualizing the flow field inside a nozzle based on the Reynolds experiment, characterized in that: The invention comprises a transparent nozzle (6), a liquid container (8), a pressure sensor (806), a high-speed camera (9) and a processor (10), wherein the transparent nozzle (6) is connected to a water inlet device, and the side of the transparent nozzle (6) close to the water inlet end of the transparent nozzle (6) is provided with at least one interface (501) and / or connected to at least one needle tube (7), and the liquid container (8) is provided with a colored liquid (805) connected to the interface (501) or the needle tube (7), the pressure sensor (806) is used to monitor the internal pressure of the liquid container (8) and feed back to the processor (10), the viewing range of the high-speed camera (9) covers the entire internal flow field of the transparent nozzle (6), and the processor (10) is used to calculate the flow rate of the fluid in the transparent nozzle (6) based on the internal pressure of the liquid container (8) and the density of the colored liquid (805).

2. The device for visualizing the flow field inside a nozzle based on the Reynolds experiment according to claim 1, characterized in that: The water inlet device comprises a water tank (1), a water inlet pipe (11) connecting the water tank (1) and a transparent nozzle (6), and the water inlet pipe (11) is provided with a water pump (2), a flow meter (3) and a first valve (4).

3. The device for visualizing the flow field inside a nozzle based on the Reynolds experiment according to claim 1, characterized in that: A plurality of interfaces (501) are arranged at intervals in the circumferential direction around the transparent nozzle (6).

4. The device for visualizing the flow field inside a nozzle based on the Reynolds experiment according to claim 1, characterized in that: The transparent nozzle (6) is slidably connected to the needle tube (7), and the liquid container (8) is provided with an adjustment mechanism, which is used to drive the needle tube (7) to reciprocate along the radial direction of the transparent nozzle (6) and adjust the depth of the needle tube (7) inserted into the transparent nozzle (6).

5. The device for visualizing flow field in a nozzle based on Reynolds experiment according to claim 1, characterized in that: A second valve (803) is provided between the liquid container (8) and the interface (501) or between the liquid container (8) and the needle tube (7).

6. The device for visualizing flow field in a nozzle based on Reynolds experiment according to claim 1, characterized in that: The processor (10) is used for: Calculate the flow rate of the fluid in the transparent nozzle (6), where P1 is the internal pressure (Pa) of the liquid container (8) measured by the pressure sensor (806), and ρ is the density (kg / m 3 ), v2 is the flow rate (m / s) of the fluid in the transparent nozzle (6).

7. A method for visualizing the flow field inside a nozzle based on Reynolds experiment, characterized in that: The device for visualizing flow field in a nozzle based on the Reynolds experiment according to any one of claims 1 to 6, and the method thereof comprises: The transparent nozzle (6) is supplied with water through a water inlet device, so that the colored liquid (805) is ejected from the transparent nozzle (6) along a water flow trajectory, and the streamlines of the flow field in the transparent nozzle (6) are captured and stored by a high-speed camera (9). The processor (10) calculates the flow rate of the fluid in the transparent nozzle (6) in real time based on the internal pressure of the liquid container (8) and the density of the colored liquid (805).

8. The method for visualizing the flow field inside a nozzle based on the Reynolds experiment according to claim 7, characterized in that: A transparent nozzle (6) is manufactured using 3D printing light-curing resin, and the refractive index difference between the transparent nozzle (6) and the colored liquid (805) is ≤0.

2.

9. The method for visualizing the flow field inside a nozzle based on the Reynolds experiment according to claim 7, characterized in that: The liquid container (8) is connected to the interfaces (501) at different positions to observe the streamlines and fluid flow rates at different radial positions in the transparent nozzle (6).

10. The method for visualizing the flow field inside a nozzle based on the Reynolds experiment according to claim 7, characterized in that: By adjusting the depth of the needle tube (7) inserted into the transparent nozzle (6) along the radial direction of the transparent nozzle (6), the streamlines and fluid flow rates at different radial positions in the transparent nozzle (6) are observed.

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