Gas micro-flow measurement and control device and installation method thereof

Abstract

The invention discloses a gas micro-flow measurement and control device and an installation method thereof, and belongs to the technical field of gas flow measurement and control. The measurement and control device comprises a vortex shedding flowmeter, a pneumatic control valve and a controller. The vortex shedding flowmeter is arranged on a gas circulation pipeline and used for measuring gas flow, the vortex shedding flowmeter comprises a measuring pipe, and the value range of the caliber of the measuring pipe is [6, 8] mm. And the pneumatic adjusting valve is arranged on a gas circulation pipeline and is used for adjusting the flow of the gas. And the controller is electrically connected with the vortex shedding flowmeter and the pneumatic control valve, and is used for receiving a measurement result of the vortex shedding flowmeter and controlling the opening degree of the pneumatic control valve. The device can solve the problems that the micro flow of the high-temperature gas cannot be effectively measured and controlled, the measurement result is inaccurate, and the control of the regulating valve is unstable in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of gas flow measurement and control, and specifically relates to a gas micro-flow measurement and control device and an installation method thereof. Background Art

[0002] As shown in Table 1, there are many ways to measure gas flow, such as differential pressure flowmeter, vortex flowmeter, Coriolis mass flowmeter, and rotor flowmeter. The above flowmeters combined with electric control valves are common ways to achieve gas flow control. Among them, the thermal mass flow controller comes with a control valve body to achieve flow control.

[0003] Table 1 Gas flow measurement method

[0004]

[0005] However, in the scenario of measuring the small flow rate of high-temperature steam (such as 170°C), the above flow meter combined with the electric control valve cannot effectively measure and control the high-temperature steam flow, and there are a series of problems such as inaccurate measurement results and unstable control of the control valve.

[0006] (1) The measurement results of small flow rates are inaccurate.

[0007] First of all, low Reynolds number is a notable feature of micro flow. Reynolds number Re is a dimensionless parameter that characterizes the ratio of fluid inertia force and viscosity force, and Re≤2300 is laminar flow. Generally, pipeline flow is turbulent flow, and existing flow meters are also designed for turbulent flow dynamics. However, micro flow meters are often in laminar flow (for example, the inner diameter of the pipe is 6mm, the flow rate is 0.05L / min, and Re is 1800) or laminar / turbulent transition zone flow due to their small pipe diameter. Micro flow measurement is greatly affected by fluid changes during use.

[0008] Secondly, in the actual measurement process, the performance of the regulating valve also causes the instability of the flow rate due to the need to control the tiny flow of gas. There is a close relationship between the volume and pressure of the gas. When the pressure of the gas output is unstable, the continuous on-off action of the regulating valve, the throttling and release are constantly rotated, and the pressure fluctuation of the gas will also change significantly, making the detection more difficult. This amplification will be superimposed on the regulating valve. Therefore, in the actual use process, a little parameter fluctuation will cause a long-term fluctuation adjustment of the output flow.

[0009] Similarly, gas measuring instruments are usually calibrated with air during instrument calibration. Usually for medium and large diameter flow meters, if it is known that some physical properties of the actual measured fluid and the calibration fluid are different and the indication changes regularly, it is often corrected with an appropriate coefficient. However, some micro flow meters are greatly affected by fluid properties such as viscosity, resulting in poor performance even if they are calibrated with air because the medium is different from the calibration medium in actual use.

[0010] The above reasons all lead to inaccurate measurement results of small flows.

[0011] (2) The control of the regulating valve is unstable.

[0012] As the core component of flow control, the quality and performance of the regulating valve determine the effect of the control output. However, in the process of micro-flow measurement and control, due to the small diameter of the pipe and the small diameter, a small deviation in the execution of the actuator will cause a large change in the control output.

[0013] In actual use, it often happens that the actuator shows that it is only 5% open, and the flow has already reached the normal flow. If it is slightly closed, the flow drops sharply or even stops. Therefore, unstable control of the regulating valve will also affect the accuracy of the measurement results.

[0014] Among them, the thermal mass flow controller is the only device that can realize flow control with its own matching regulating valve. However, the control mode implemented by its configuration is a thermal gas measurement device combined with an electric regulating valve. This structure also causes its use limitations: the thermal measurement principle has a slow response speed; if the measured gas deposits a scale layer on the pipe wall and sensor, it will affect the measurement value; the use of pulsating flow will be restricted; the change of the measured gas composition has a great impact on its measurement. The regulating valve of the controller is an electric regulating valve, which has requirements for the temperature of the medium and cannot exceed 70°C. The interface is mostly threaded connection, and the structural protection level is also relatively low. Therefore, the upgrade and improvement of the regulating valve for high-temperature gas micro-flow measurement and control is also an urgent problem to be solved. Summary of the invention

[0015] The technical problem to be solved by the present invention is to provide a gas micro-flow measurement and control device and an installation method thereof in view of the above-mentioned deficiencies in the prior art, which can measure and control the micro-flow of high-temperature steam and has the advantages of accurate measurement results and high control precision.

[0016] In a first aspect, the present invention provides a device for measuring and controlling a small gas flow rate, comprising a vortex flowmeter, a pneumatic regulating valve, and a controller.

[0017] The vortex flowmeter is installed on a gas-circulating pipeline and is used to measure the gas flow rate. The vortex flowmeter includes a measuring tube, and the diameter of the measuring tube ranges from [6, 8] mm.

[0018] Pneumatic regulating valves are installed on gas-circulating pipelines to adjust the flow rate of gas.

[0019] The controller is electrically connected to the vortex flowmeter and the pneumatic regulating valve, and is used for receiving the measurement result of the vortex flowmeter and controlling the opening of the pneumatic regulating valve.

[0020] Preferably, the controller adopts a fuzzy PID based

[0021] A controller that uses the Proportional-Integral-Derivative (PID) control algorithm.

[0022] Preferably, the vortex flowmeter further comprises a vortex sensor and a vortex generator. The probe of the vortex sensor is parallel to the conical surface of the vortex generator, and the installation position of the probe of the vortex sensor is set within the range of [1.5h, 2.1h] from the oncoming surface, where h is the equivalent diameter of the pipeline through which the gas flows.

[0023] Preferably, the probe of the vortex sensor is a piezoelectric ceramic probe.

[0024] Preferably, the controller comprises a signal extraction unit, which is used to extract the measurement results of the vortex flowmeter based on HHT time-frequency analysis, and to perform adaptive filtering and instantaneous frequency statistics on the extracted measurement results based on empirical mode decomposition (EMD).

[0025] Preferably, the controller comprises a control unit, which is used to control the opening of the pneumatic regulating valve based on a pneumatic proportional servo system.

[0026] The pneumatic control valve adopts a needle valve core so that the flow characteristics of the pneumatic control valve meet the equal percentage characteristics.

[0027] Preferably, the controller includes a touch display screen, which is used to display the measurement result of the vortex flowmeter and receive the flow control target value.

[0028] In a second aspect, the present invention also provides a method for installing a gas micro-flow measurement and control device, comprising: installing a vortex flowmeter on a gas circulation pipeline, wherein the diameter of the measuring tube of the vortex flowmeter is within a value range of [6, 8] mm; installing a pneumatic control valve on the gas circulation pipeline; and electrically connecting a controller to the vortex flowmeter and the pneumatic control valve.

[0029] Preferably, the vortex flowmeter comprises a vortex sensor and a vortex generator, and the vortex generator comprises a trapezoidal column vortex generator.

[0030] Before installing the vortex flowmeter on the pipeline through which gas flows, the installation method further includes: determining the installation position of the probe of the vortex sensor.

[0031] Determining the installation position of the probe of the vortex sensor includes: conducting experiments on trapezoidal column vortex generators of different sizes in two-dimensional and three-dimensional flow fields respectively; determining the installation position of the probe of the vortex sensor based on the signal characteristics of the pressure signal and the velocity signal at different positions, wherein the signal characteristics include at least one of the following: signal strength, signal-to-noise ratio, and linearity.

[0032] Preferably, before installing the pneumatic regulating valve on a pipeline through which gas flows, the installation method further comprises: determining the size of the needle valve core.

[0033] Determining the size of the needle valve core includes: establishing a three-dimensional model of the pneumatic control valve based on simulation software, the three-dimensional model including an initial valve core; meshing the three-dimensional model; performing simulation calculations on the meshed three-dimensional model under different valve openings to obtain a flow characteristic curve of the three-dimensional model; optimizing the initial valve core profile based on the flow characteristic curve to obtain the size of the needle valve core.

[0034] The present invention provides a gas micro-flow measurement and control device and an installation method thereof, which adopts a vortex flowmeter capable of measuring high-temperature media, optimizes the design of the measuring tube caliber of the vortex flowmeter, and adopts a high-temperature resistant pneumatic regulating valve to adjust the gas flow rate, and then controls the opening of the pneumatic regulating valve based on the measurement result of the vortex flowmeter based on the controller, thereby realizing the measurement and control of the micro-flow of high-temperature steam. Since the measuring tube caliber of the vortex flowmeter is optimized and the pneumatic regulating valve has fast response speed, good linear characteristics and low flow characteristics, the micro-flow of high-temperature steam can be accurately measured and stably controlled. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the structure of a gas micro-flow measurement and control device according to Embodiment 1 of the present invention;

[0036] Figure 2 A schematic diagram of the control principle of a controller according to Embodiment 1 of the present invention;

[0037] Figure 3 A schematic diagram of a geometric model of a vortex flowmeter according to Embodiment 1 of the present invention;

[0038] Figure 4 is a curve diagram showing the relationship between pressure on the vortex generating body and time in Example 1 of the present invention;

[0039] Figure 5 This is a curve diagram showing the relationship between the pressure monitoring point position and the vibration intensity in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] It should be understood that the specific embodiments and drawings described herein are only used to explain the present invention rather than to limit the present invention.

[0042] It can be understood that, in the absence of conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other.

[0043] It can be understood that, for the convenience of description, the drawings of the present invention only show the parts related to the present invention, while the parts irrelevant to the present invention are not shown in the drawings.

[0044] It can be understood that each unit and module involved in the embodiments of the present invention may correspond to only one physical structure, or may be composed of multiple physical structures, or multiple units and modules may be integrated into one physical structure.

[0045] It can be understood that, without conflict, the functions and steps marked in the flowcharts and block diagrams of the present invention may occur in an order different from that marked in the drawings.

[0046] It is understood that the flowcharts and block diagrams of the present invention illustrate the possible architectures, functions, and operations of the systems, devices, equipment, and methods according to the various embodiments of the present invention. Each box in the flowchart or block diagram may represent a unit, module, program segment, or code, which contains executable instructions for implementing the specified functions. Moreover, each box or combination of boxes in the block diagram and flowchart may be implemented by a hardware-based system that implements the specified functions, or may be implemented by a combination of hardware and computer instructions.

[0047] It can be understood that the units and modules involved in the embodiments of the present invention can be implemented by software or hardware. For example, the units and modules can be located in a processor.

[0048] From Table 1, we can see that compared with other flowmeters, the vortex flowmeter has less pressure loss on the pipeline than the differential pressure flowmeter. In the case of small flow, the gas flow rate is too low, and the differential pressure value of the orifice plate after the differential pressure flowmeter is installed will also be too low, which requires extremely high measurement performance of the differential pressure transmitter. After calculation, the differential pressure value of the DN15 flowmeter is 10Pa when the flow rate is 10L. In this case, no differential pressure transmitter can meet the measurement requirements, and other environmental conditions and pipeline vibrations also have a great impact on the measurement.

[0049] Compared with the Coriolis mass flowmeter measurement method, although the vortex flowmeter measurement method does not have as high measurement accuracy as the Coriolis method, the Coriolis mass flowmeter for measuring small flow rates is an imported product, the cost is too high, and the subsequent after-sales maintenance is more difficult.

[0050] Thermal mass flow controllers have built-in control functions and are inherently superior in gas measurement. However, they also have obvious defects: the structure is mostly in the form of experimental equipment, with poor structural strength; high requirements for gas composition; and restrictions on the temperature of the medium, making it impossible to measure and control high-temperature gases.

[0051] Therefore, in some related technologies, the vortex flowmeter is used to measure the gas flow rate, and then the measurement signal is transmitted remotely to a control system such as a PLC (Programmable Logic Controller) or a DCS (Distributed Control System), and after being calculated by the control system, it is output to the electric control valve to adjust the opening to achieve the control of the gas flow rate. Since the electric control valve requires the temperature of the medium not to exceed 70°C, and the minimum diameter of the vortex flowmeter is 15 mm, it is impossible to measure and control the tiny flow of high-temperature steam, resulting in inaccurate measurement results. In addition, the remote transmission of the measurement signal causes the attenuation of the signal, which is easily interfered by other strong electrical signals, further affecting the control accuracy; the flow measurement and control valve control are generally too long due to the limitation of the entire control system program operation cycle. Therefore, in actual use, the flow measurement and control of the electric control valve are poorly coordinated and the control accuracy is low. Especially when there is a change in working conditions, the flow control often oscillates and fluctuates, affecting the stability of the process. The measurement and control device of this embodiment is used to solve the above problems.

[0052] Embodiment 1:

[0053] This embodiment provides a gas micro-flow measurement and control device, which is applied to the scenario of measuring the gas micro-flow, and is particularly suitable for the scenario of measuring the micro-flow of high-temperature steam.

[0054] like Figure 1 As shown, a gas micro-flow measurement and control device includes a vortex flowmeter, a pneumatic regulating valve, and a controller.

[0055] The vortex flowmeter is arranged on the pipeline through which the gas flows, and is used to measure the gas flow rate. The vortex flowmeter includes a measuring tube, and the range of the diameter of the measuring tube is [6, 8] mm. The pneumatic regulating valve is arranged on the pipeline through which the gas flows, and is used to adjust the flow rate of the gas. The controller is electrically connected to the vortex flowmeter and the pneumatic regulating valve, and is used to receive the measurement result of the vortex flowmeter and control the opening of the pneumatic regulating valve.

[0056] In this embodiment, the controller is used to obtain the measurement results of the vortex flowmeter for the gas micro-flow, and output the opening control instructions for the pneumatic control valve based on the flow control target value. The pneumatic control valve is used to perform the corresponding action of the valve opening according to the opening control instruction of the controller, thereby realizing the measurement and control of the gas micro-flow in the pipeline. Among them, the controller can be located in the local end, a non-remote PLC or DCS system, or it can be located in a remote PLC or DCS system. The gas micro-flow measurement and control device of this embodiment is achieved by developing a new vortex flowmeter with a small diameter (i.e., the range of the measuring tube diameter is [6, 8] mm), and integrating the integrated valve control method to realize the measurement and control of the gas micro-flow.

[0057] It is understandable that at the same flow value, the larger the diameter of the measuring tube, the lower the medium flow rate. When the flow rate is lower than the minimum flow rate of the flow meter, the flow meter cannot measure accurately. At present, the minimum diameter of the vortex flowmeter on the market is DN15. By redesigning the structure of the vortex flowmeter and reducing the diameter of its measuring tube to increase the flow rate of the medium in the measuring tube, the flow meter's lower limit flow measurement value can be effectively reduced.

[0058] Since the lower limit of the flow rate of the high-temperature steam medium in this embodiment is 0.5Kg / h, and the measurable flow rate range of the general gaseous medium of the vortex flowmeter is 5m / s-60m / s, when the medium flow rate is 5m / s, the flow rate of the measuring tube DN10 is 1.4137m 3 / h; the flow rate of DN8 is 0.9048m 3 / h; DN6 diameter is 0.5089m 3 / h. According to the calculation formula Vm = V*ρ, where Vm is the mass flow rate, V is the volume flow rate, and ρ is the medium density, it can be obtained that: at DN10 caliber, the density of steam should not be greater than 0.3536Kg / m 3 ; At DN8 diameter, the steam density should not be greater than 0.5526Kg / m 3 ; For DN6 diameter, the density of steam should not be greater than 0.9825Kg / m 3 By comparing the density of saturated steam and superheated steam, it can be seen that only when the diameter is DN8 or smaller can the flow rate of the high-temperature steam medium with a flow rate lower limit of 0.5Kg / h be measured. Therefore, the diameter of the measuring tube of the vortex flowmeter is improved to 6 mm, or 8 mm, or a value between (6, 8) mm, so that the high-temperature steam medium of this embodiment can be measured.

[0059] Optionally, the controller adopts a controller based on a fuzzy PID control algorithm.

[0060] In this embodiment, the controller based on the fuzzy PID control algorithm can achieve precise control of small flow rates, which is beneficial to improving the accuracy of flow measurement results. Compared with the traditional PID control algorithm, the fuzzy PID control algorithm of this embodiment has the following advantages: (1) Strong adaptability: The fuzzy PID control algorithm can adapt to various complex nonlinear systems. It uses fuzzy logic to deal with the uncertainty and changes of the system, so that when facing system parameter changes and external interference, it can automatically adjust the control parameters to maintain good control performance. (2) Good robustness: The fuzzy PID control algorithm has strong anti-interference ability and can maintain a stable control effect even when the dynamic characteristics of the system change. (3) High control accuracy. (4) Easy to implement: Compared with other complex control algorithms, the fuzzy PID control algorithm is relatively simple to implement, with a small amount of calculation, and is suitable for real-time control systems. (5) Easy to adjust parameters: The fuzzy PID controller uses fuzzy rules to adjust the PID parameters online, rather than relying on fixed gain values. This flexibility makes the fuzzy PID controller more effective in dealing with complex processes.

[0061] Most traditional measurement and control devices use PID controllers to achieve constant flow control during flow control. When the measurement accuracy and stability of the medium deteriorate, the output flow of the flow controller will fluctuate, affecting the subsequent process operation. In this embodiment, especially for media such as superheated steam, the density changes with the temperature and pressure, and accurate temperature and pressure compensation is required to determine the density, thereby calculating the mass flow. Therefore, in terms of constant flow control, the control motherboard of the controller is redesigned to comprehensively improve the data processing ability, computing ability, and storage ability of the controller, and introduce advanced dynamic compensation algorithms to improve the accuracy and stability of gas flow.

[0062] Among them, the implementation of the dynamic compensation algorithm:

[0063] Traditional PID control is the most commonly used control algorithm in control systems. The essence of PID regulation is to perform calculations according to the functional relationship of proportion, integration, and differentiation based on the input deviation value, and use the calculation results for output. In the PID controller, the selection of Kp value is determined by the response speed of the system. Increasing Kp can increase the response speed and reduce the steady-state deviation; however, too large a Kp value will produce a large overshoot and even make the system unstable; reducing Kp can reduce overshoot and improve stability, but too small a Kp will slow down the response speed and extend the adjustment time. Compared with the PID algorithm, the fuzzy controller has the characteristics of fast adjustment speed and good robustness, but the disadvantage of poor steady-state accuracy is also obvious. In this embodiment (such as Figure 2As shown in the figure, the above defects of the simple PID algorithm are overcome by using a composite PID control algorithm and a fuzzy control algorithm with dynamic compensation to achieve better accuracy and stability of flow control. In the measurement process of the measurement and control device, the flow measurement and flow control of the medium is a closed-loop process. The changes in the gas pressure and temperature in the process pipeline will directly affect the measurement effect. When the measurement fluctuates, the valve control system will make corresponding adjustments based on the changes in the measurement, causing the output of the entire gas flow to fluctuate. Figure 2 As shown, the controller of the fuzzy PID control algorithm of this embodiment includes a PID controller and a fuzzy controller, the actuator is a pneumatic control valve, and the measuring element is a vortex flowmeter. When the fuzzy controller is introduced, the flow data response error e and its rate of change (dE / dt) are continuously detected at each sampling moment, and then the correction amount of the PID parameter is obtained according to the established fuzzy rules, so that the PID controller can actively adjust the size of its own parameters according to the changes in the system response, thereby enhancing the dynamic response performance of the system and the robustness to external interference. This can avoid the single control parameters in the traditional PID control, and the inability to make reasonable compensation and strain to cope with the complex changes in working conditions, and can improve the stability and accuracy of the control output.

[0064] Optionally, the vortex flowmeter further includes a vortex sensor and a vortex generator. The probe of the vortex sensor is parallel to the conical surface of the vortex generator, and the installation position of the probe of the vortex sensor is set within the range of [1.5h, 2.1h] from the oncoming surface, where h is the equivalent diameter of the pipeline through which the gas flows. Figure 3 As shown, the vortex generator is a vortex street generator.

[0065] In some related technologies, the contact area between the probe and the fluid is large and is easily affected by fluid disturbances, resulting in poor stability of the measurement signal. The installation position of the probe is not scientific, resulting in low efficiency in measuring signal acquisition and inaccurate measurement results. In order to meet the needs of measuring small flow rates and improve the measurement accuracy of the vortex flowmeter, this embodiment determines the installation position of the probe through a simulation analysis method. Determining the installation position of the probe of the vortex sensor includes: conducting experiments on trapezoidal column vortex generators of different sizes in two-dimensional and three-dimensional flow fields respectively; determining the installation position of the probe of the vortex sensor based on the signal characteristics of the pressure signal and the velocity signal at different positions, wherein the signal characteristics include at least one of the following: signal strength, signal-to-noise ratio, and linearity.

[0066] Specifically, determining the installation position of the probe includes: performing a flow field simulation analysis on the existing probe structure based on CFD software.

[0067] Establish geometric model: Use CAD software (such as SolidWorks) to establish the calculation area model according to the actual diameter DN8 of the vortex flowmeter, such as Figure 3shown.

[0068] Meshing: Mesh the model, select automatic meshing, and set the initial meshing level. The minimum gap size is usually set to the distance between the vortex generator and the probe, such as 5mm. Select the default state for the remaining parameters, and then run the mesh solver to obtain the total number of fluid meshes.

[0069] Set simulation parameters: select internal flow field analysis, set the direction and magnitude of gravity acceleration, select transient analysis and set simulation time. Set simulation time to 10s and save interval to 0.05s; select water as the fluid medium, and its density is 998.2Kg / m 3 , kinematic viscosity is 1.003×10 -3 Pa·s; flow type is laminar flow and turbulent flow; set initial conditions according to flow type (laminar flow and turbulent flow), flow direction is x direction, and select turbulence intensity and turbulence length as turbulence parameters. Set multiple pressure monitoring points at different distances from the fluid inlet for subsequent post-processing.

[0070] Solution settings: Select the appropriate solver and time step, set the velocity, pressure and force as global targets, select the force on one side of the probe surface (for example, the positive z direction) as the surface target, and then run the solver.

[0071] Result analysis: Through simulation settings, when the fluid flows in the flow channel, vortices are generated alternately and regularly on both sides of the generator. The pressure acting on the vortex generator changes according to a certain periodic law.

[0072] By analyzing the dynamic pressure change curves at different pressure monitoring points, such as Figure 4 and Figure 5 As shown in the figure, the intensity of the dynamic pressure signal is different depending on the position of the pressure monitoring point. The basic rule of change is that as the distance from the frontal surface of the vortex generating body increases, the vortex signal intensity first increases and then decreases. It is found that when the distance from the frontal surface is about 1.5h-2.1h (h is the equivalent diameter of the flow channel), the vortex signal generated is the strongest, which is the best placement position for the sensor probe.

[0073] Optionally, the probe of the vortex sensor is a piezoelectric ceramic probe.

[0074] In this embodiment, four piezoelectric ceramic probes are used to eliminate the influence of external vibration on the measurement results.

[0075] Optionally, the controller includes a signal extraction unit. The signal extraction unit is used to extract the measurement results of the vortex flowmeter based on HHT time-frequency analysis, and to perform adaptive filtering and instantaneous frequency statistics on the extracted measurement results based on empirical mode decomposition (EMD).

[0076] In this embodiment, the turbulence, pulsation, instability and unevenness of the flow field of the flowing medium in the pipeline and the low-frequency swing noise of the fluid will have a great impact on the measurement results when measuring small flow rates, affecting the accuracy of the measurement results. Therefore, this embodiment introduces HHT time-frequency analysis in the signal extraction of the measurement results, and uses it as a means of adaptive filtering to filter out the noise components in the signal, and performs probability density statistics on the instantaneous frequency of each trend component, which is used as an empirical mode decomposition criterion. It has been verified through experiments that this method can greatly expand the measurement lower limit of the vortex flowmeter on the basis of ensuring linearity, which is conducive to improving the accuracy of the measurement results.

[0077] Optionally, the controller includes a control unit. The control unit is used to control the opening of the pneumatic control valve based on the pneumatic proportional servo system. The pneumatic control valve adopts a needle valve core so that the flow characteristic of the pneumatic control valve meets the equal percentage characteristic.

[0078] In order to solve the problem of unstable control of regulating valves in related technologies, this embodiment adopts a pneumatic regulating valve. At the same time, the opening of the pneumatic regulating valve is controlled based on a pneumatic proportional servo system, and the valve core of the pneumatic regulating valve is improved. A needle-shaped valve core is adopted to make the flow characteristics of the pneumatic regulating valve meet the equal percentage characteristics, thereby improving the control accuracy and further improving the accuracy of the measurement results.

[0079] For the control of the opening of the pneumatic regulating valve based on the pneumatic proportional servo system, the pneumatic proportional servo system has the characteristics of being able to achieve stable and continuous control of the pneumatic system, and it uses two control valves, servo valve and proportional valve. The output of the pneumatic proportional servo system is a continuous change system formed according to a certain proportion of the input, and finally controls the opening of the valve in the form of current, so as to achieve the purpose of controlling the flow. The system can achieve high control accuracy when the flow and pressure change continuously. Compared with other systems, the pneumatic proportional servo system has its own advantages, mainly the system has a high operating speed, can output large power, and has a long system life, so it has strong competitiveness in the field of industrial automation. The use of a pneumatic proportional servo system can not only reduce the time required for the drive system by 20%, but also reduce the vibration generated by the drive system during the braking and pneumatic process to a certain extent, thereby improving the quality of the product, reducing the loss of equipment, and improving the accuracy of the pneumatic proportional servo system in controlling the valve opening.

[0080] Regarding the improvement of the valve core, in the structure of the small-diameter regulating valve, the valve core part is of vital importance as a key component of flow control. Therefore, the structural form of the valve core is related to the quality of flow control. In this embodiment, the small-diameter regulating valve adopts a needle-shaped valve core. By applying simulation software, the curve is corrected point by point, and the structural design of the valve core is optimized so that the flow characteristics of the regulating valve reach the needle-shaped valve core structure of the cylinder with equal percentage characteristics, and the structure is optimized to obtain the size of the needle-shaped valve core to meet the control of small-diameter and tiny flows. Determining the size of the needle-shaped valve core includes: establishing a three-dimensional model of the pneumatic regulating valve based on the simulation software, the three-dimensional model includes an initial valve core; meshing the three-dimensional model; performing simulation calculations on the meshed three-dimensional model under different valve openings to obtain the flow characteristic curve of the three-dimensional model; optimizing the initial valve core profile based on the flow characteristic curve to obtain the size of the needle-shaped valve core.

[0081] Specifically, the simulation process for determining the needle valve core size includes:

[0082] Step S11, the valve core structure of the original design model adopts a simple conical structure. Simulate the regulating valve and establish a three-dimensional model: select models with openings of 20%, 40%, 60%, 80% and 100%, and connect straight pipe sections with a length of 10 times the inner diameter at both ends of the valve body; divide the overall three-dimensional simulation model into multiple parts, dissect the inside of the valve body into a grid structure, and set it to a relatively small size. This method is used to enhance the accuracy of iterative calculation during simulation.

[0083] Step S12, for the model, the inlet pressure is set to 100kP, and the outlet pressure is set to 0kPa. The ratio of the flow rate of the model at different openings to their respective maximum flow rates is calculated by simulation, and the flow curve of the model is plotted for comparison with the ideal value. At the same time, according to GB / T17213.10-2015, the deviation of each test flow coefficient from the value specified by the manufacturer in the flow characteristics is calculated to calculate the allowable deviation at different openings to optimize the valve core profile of the regulating valve, and finally complete the valve core profile design, that is, complete the needle valve core size design.

[0084] By optimizing the control valve core, a valve with characteristics that meet relevant national and international standards is designed, so that the flow characteristics of the control valve reach equal percentage characteristics, and the flow characteristics of each opening are within the allowable error range.

[0085] Optionally, the controller includes a touch display screen, which is used to display the measurement result of the vortex flowmeter and receive the flow control target value.

[0086] In this embodiment, the flow control target value refers to the target flow size set in the controller, which is the specific flow level that the measurement and control device hopes to maintain or achieve. The touch display screen facilitates local control. The vortex flowmeter, pneumatic control valve, and controller can be integrated into an integrated gas micro-flow measurement and control device, or a split gas micro-flow measurement and control device. The integrated measurement and control device uses integrated modular design, embedded technology and integration technology to reduce the size of the device, improve anti-interference performance and reliability, and introduce a microprocessor to make the measurement and control device a combination of hardware and software. It can make judgments, decisions, automatic corrections and compensations based on input signals, achieve precise control, and improve flow measurement accuracy.

[0087] The gas micro-flow measurement and control device provided in this embodiment adopts a vortex flowmeter that can measure high-temperature media, optimizes the design of the measuring tube diameter of the vortex flowmeter, and adopts a high-temperature resistant pneumatic control valve to adjust the flow of the gas, and then controls the opening of the pneumatic control valve based on the measurement result of the vortex flowmeter based on the controller, so that the flow of high-temperature steam can be measured and controlled. Due to the optimization design of the measuring tube diameter of the vortex flowmeter, and the pneumatic control valve has fast response speed, good linear characteristics and low flow characteristics, the micro-flow of high-temperature steam can be accurately measured. It solves the problems of traditional flowmeters such as difficulty in measuring small flow, low accuracy, large volume, and slow adaptability to working conditions, and provides an effective means for accurate measurement of small flow on the production line. In addition, the accuracy of the measurement results and the control accuracy are further improved by optimizing the control algorithm of the controller, determining the installation position of the probe of the vortex sensor, and improving the valve core of the pneumatic control valve.

[0088] Embodiment 2:

[0089] This embodiment provides an installation method of a gas micro-flow measurement and control device, which is applied to the gas micro-flow measurement and control device described in Embodiment 1. The installation method includes:

[0090] Step 201, installing a vortex flowmeter on a gas-circulating pipeline, wherein the diameter of the measuring tube of the vortex flowmeter is within a value range of [6, 8] mm.

[0091] Step 202, installing the pneumatic regulating valve on the pipeline through which the gas flows.

[0092] Step 203, electrically connecting the controller to the vortex flowmeter and the pneumatic regulating valve.

[0093] Optionally, the vortex flowmeter includes a vortex sensor and a vortex generator, and the vortex generator includes a trapezoidal column vortex generator.

[0094] Before installing the vortex flowmeter on the pipeline through which gas flows, the installation method further includes: determining the installation position of the probe of the vortex sensor.

[0095] Optionally, determining the installation position of the probe of the vortex sensor includes:

[0096] Experiments were conducted on trapezoidal cylindrical vortex generators of different sizes in two-dimensional and three-dimensional flow fields.

[0097] The probe installation position of the vortex sensor is determined based on the signal characteristics of the pressure signal and the velocity signal at different positions, wherein the signal characteristics include at least one of the following: signal strength, signal-to-noise ratio, and linearity.

[0098] Optionally, before installing the pneumatic regulating valve on a pipeline through which gas flows, the installation method further includes: determining the size of the needle valve core.

[0099] Optionally, determining the size of the needle valve core includes: establishing a three-dimensional model of the pneumatic control valve based on simulation software, the three-dimensional model including an initial valve core; meshing the three-dimensional model; performing simulation calculations on the meshed three-dimensional model under different valve openings to obtain a flow characteristic curve of the three-dimensional model; optimizing the initial valve core profile based on the flow characteristic curve to obtain the size of the needle valve core.

[0100] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A gas micro-flow measurement and control device, characterized in that: Including vortex flowmeter, pneumatic regulating valve, controller, The vortex flowmeter is installed on the gas flow pipeline to measure the gas flow. The vortex flowmeter includes a measuring tube, and the diameter of the measuring tube ranges from [6, 8] mm. Pneumatic regulating valve is installed on the gas flow pipeline to adjust the gas flow rate. The controller is electrically connected to the vortex flowmeter and the pneumatic regulating valve, and is used for receiving the measurement result of the vortex flowmeter and controlling the opening of the pneumatic regulating valve.

2. The device according to claim 1, characterized in that The controller adopts a controller based on fuzzy PID control algorithm.

3. The device according to claim 1, characterized in that The vortex flowmeter also includes a vortex sensor and a vortex generator. The probe of the vortex sensor is parallel to the conical surface of the vortex generator, and the installation position of the probe of the vortex sensor is set within the range of [1.5h, 2.1h] from the frontal surface, where h is the equivalent diameter of the pipeline through which the gas flows.

4. The device according to claim 3, characterized in that The probe of the vortex sensor adopts a piezoelectric ceramic probe.

5. The device according to claim 1, characterized in that The controller includes a signal extraction unit, The signal extraction unit is used to extract the measurement results of the vortex flowmeter based on HHT time-frequency analysis, and to perform adaptive filtering and instantaneous frequency statistics on the extracted measurement results based on empirical mode decomposition (EMD).

6. The device according to claim 1, characterized in that The controller includes a control unit, The control unit is used to control the opening of the pneumatic regulating valve based on the pneumatic proportional servo system. The pneumatic control valve adopts a needle valve core so that the flow characteristics of the pneumatic control valve meet the equal percentage characteristics.

7. The device according to claim 1, characterized in that The controller includes a touch screen display, The touch display is used to display the measurement results of the vortex flowmeter and receive the flow control target value.

8. A method for installing a gas micro-flow measurement and control device, characterized in that: include: The vortex flowmeter is installed on a gas flow pipe, wherein the diameter of the measuring pipe of the vortex flowmeter is within the value range of [6, 8] mm; Install the pneumatic regulating valve on the pipeline where the gas flows; The controller is electrically connected to the vortex flowmeter and the pneumatic regulating valve.

9. The installation method according to claim 8, characterized in that: The vortex flowmeter includes a vortex sensor and a vortex generator. The vortex generator includes a trapezoidal column vortex generator. Before installing the vortex flowmeter on the gas flow pipeline, the method further includes: determining the installation position of the probe of the vortex flowmeter, Determining the probe installation position of the vortex street sensor includes: Experiments were conducted on trapezoidal cylindrical vortex generators of different sizes in two-dimensional and three-dimensional flow fields. The probe installation position of the vortex sensor is determined based on the signal characteristics of the pressure signal and the velocity signal at different positions, wherein the signal characteristics include at least one of the following: signal strength, signal-to-noise ratio, and linearity.

10. The installation method according to claim 9, characterized in that: Before installing the pneumatic control valve on the gas flow pipeline, it also includes: determining the needle valve core size, Needle valve sizing includes: A three-dimensional model of a pneumatic control valve is established based on simulation software, wherein the three-dimensional model includes an initial valve core; Mesh the three-dimensional model; The three-dimensional model after meshing is simulated and calculated under different valve openings to obtain the flow characteristic curve of the three-dimensional model; The initial valve core profile is optimized based on the flow characteristic curve to obtain the needle valve core size.

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