A gas micro-flow measuring and controlling device and a mounting method thereof

Abstract

The application discloses a kind of gas little flow's measurement and control device and its installation method, belong to gas flow measurement and control technical field.Measurement and control device includes vortex flowmeter, pneumatic regulating valve, controller.Vortex flowmeter, be located on the pipeline of gas flow, for measuring gas flow, vortex flowmeter includes measuring tube, the range of the value of measuring tube caliber is [6,8] millimeter.Pneumatic regulating valve, be located on the pipeline of gas flow, for adjusting the size of gas flow.Controller, with vortex flowmeter and pneumatic regulating valve electric connection, for receiving the measurement result of vortex flowmeter, and control pneumatic regulating valve opening degree.The device can solve the problem that related technology cannot effectively measure and control the little flow of high-temperature gas, and the measurement result is inaccurate, and the regulating valve control is unstable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas flow measurement and control, and particularly relates to a device for measuring and controlling micro gas flow and a mounting method thereof. BACKGROUND

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

[0003] Table 1: Gas flow measurement methods

[0004]

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

[0006] (1) Inaccurate measurement results of micro flow.

[0007] Firstly, low Reynolds number is a significant feature of micro flow. Reynolds number Re is a dimensionless parameter representing the ratio of inertial force and viscous force of fluid, and Re≤2300 is laminar flow. Generally, pipeline flow is turbulent flow, and existing flow instruments are designed for turbulent flow, while micro flow instruments are often in laminar flow (for example, pipe diameter 6mm, flow 0.05L / min, Re 1800) or laminar / turbulent transition flow due to small pipe diameter, and micro flow measurement is greatly affected by changes in fluid in use.

[0008] Secondly, in actual measurement process, due to the need to control the micro flow of gas, the performance of the regulating valve also causes the instability of the flow. There is a close relationship between the volume and pressure of gas, when the pressure of gas output is unstable, the regulating valve is constantly on and off, and the throttling and opening are constantly replaced, the pressure fluctuation of gas will also change significantly, causing the detection difficulty to be greater, and this amplification will be superimposed in the regulating valve. Therefore, in actual use, a little parameter fluctuation will cause long-term fluctuation adjustment of the output flow.

[0009] Similarly, during instrument calibration, gas measuring instruments are usually calibrated with air. Generally, for medium and large pipe diameter flow instruments, if the difference in some physical properties between the actual measuring fluid and the calibration fluid is known to have a regular change on the indicated value, an appropriate coefficient is often corrected. However, some micro flow instruments are greatly affected by fluid physical properties such as viscosity, resulting in that even if they are calibrated with air, the use effect will be poor due to the difference between the medium and the calibration medium.

[0010] The above reasons all result in inaccurate measurement of the micro flow.

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

[0012] The regulating valve is a core element for flow control, and its quality performance determines the control output effect. However, in the process of micro flow measurement and control, due to the small pipe diameter and small passage diameter, a small deviation in the execution process of the actuator will cause a great change in the control output.

[0013] In actual use, the actuator shows that only 5% is opened, the flow has been output to the normal flow, and a slight closing will cause a large decrease in the flow, or even no flow. Therefore, the unstable control of the regulating valve will also affect the accuracy of the measurement result.

[0014] Among them, the thermal mass flow controller is the only one with a matching regulating valve to realize the flow control device. However, the control mode realized by the configuration is a thermal gas measurement device combined with an electric regulating valve. This structure also causes its use limitation: the response speed of the thermal measurement principle is slow; the deposition of scale layer on the pipe wall and sensor will affect the measurement value; the use of pulsating flow will be limited; the change of the measured gas composition has a great influence on the measurement. The regulating valve of the controller is an electric regulating valve, which has a requirement for the temperature of the medium and cannot exceed 70 DEG C. The interface is mainly threaded connection, and the structure protection grade is also relatively low. Therefore, the upgrading and improvement of the regulating valve for the measurement and control of the micro flow of high-temperature gas is also an urgent problem to be solved. SUMMARY

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

[0016] In a first aspect, the present application provides a gas micro flow measurement and control device, comprising a vortex flowmeter, a pneumatic regulating valve and a controller.

[0017] The vortex flowmeter is arranged on a pipeline through which the gas flows, and is used for measuring the gas flow. The vortex flowmeter comprises a measuring pipe, and the diameter of the measuring pipe is in the range of [6, 8] millimeters.

[0018] The pneumatic regulating valve is arranged on the pipeline through which the gas flows, and is used for adjusting the size of the gas flow.

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

[0020] Preferably, the controller employs a controller based on fuzzy PID

[0021] (Proportional-Integral-Derivative, proportional-integral-derivative) 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 probe of the vortex sensor is installed at a position within a range of [1.5h, 2.1h] from the incident flow surface, where h is the equivalent diameter of the pipeline through which the gas flows.

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

[0024] Preferably, the controller comprises a signal extraction unit. The signal extraction unit is configured to extract 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. The control unit is configured to control the opening degree of the pneumatic regulating valve based on a pneumatic proportional servo system.

[0026] The pneumatic regulating valve employs a needle-shaped valve core to make the flow characteristics of the pneumatic regulating valve meet the equal percentage characteristics.

[0027] Preferably, the controller comprises a touch display screen. The touch display screen is configured to display the measurement results of the vortex flowmeter and receive a flow control target value.

[0028] In a second aspect, the present application further provides an installation method of a gas micro-flow measurement and control device, comprising: installing a vortex flowmeter on a pipeline through which a gas flows, wherein the measurement port diameter of the vortex flowmeter is within a value range of [6, 8] millimeters; installing a pneumatic regulating valve on the pipeline through which the gas flows; and electrically connecting a controller with the vortex flowmeter and the pneumatic regulating 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 the gas flows, the installation method further comprises: determining a probe installation position of the vortex sensor.

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

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

[0033] Determining the size of the needle-shaped valve core comprises: establishing a three-dimensional model of the pneumatic regulating valve based on simulation software, the three-dimensional model comprising an initial valve core; meshing the three-dimensional model; performing simulation calculation on the meshed three-dimensional model under different valve opening degrees to obtain a flow characteristic curve of the three-dimensional model; and optimizing the initial valve core profile based on the flow characteristic curve to obtain the size of the needle-shaped valve core.

[0034] The gas micro-flow measuring and controlling device and the installation method thereof provided by the application adopt a vortex flowmeter capable of measuring high-temperature medium, and the diameter of the measuring pipe of the vortex flowmeter is optimized and designed, and a high-temperature-resistant pneumatic regulating valve is used to regulate the size of the gas flow, and then the opening degree of the pneumatic regulating valve is controlled based on the controller according to the measurement result of the vortex flowmeter, so that the micro-flow of high-temperature steam can be measured and controlled. Since the diameter of the measuring pipe of the vortex flowmeter is optimized and designed, and since 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 DRAWINGS

[0035] Figure 1 FIG. 1 is a structural schematic diagram of a gas micro-flow measuring and controlling device according to Embodiment 1 of the application;

[0036] Figure 2 FIG. 2 is a control principle schematic diagram of a controller according to Embodiment 1 of the application;

[0037] Figure 3 FIG. 3 is a geometric model schematic diagram of a vortex flowmeter according to Embodiment 1 of the application;

[0038] Figure 4 FIG. 4 is a pressure-time relationship curve diagram of a vortex generator according to Embodiment 1 of the application;

[0039] Figure 5 FIG. 5 is a pressure monitoring point position-vibration intensity relationship curve diagram according to Embodiment 1 of the application. DETAILED DESCRIPTION

[0040] In order for those skilled in the art to better understand the technical solutions of the application, the following will further describe the embodiments of the application in detail with reference to the drawings.

[0041] It can be understood that the specific embodiments and drawings described herein are only used to explain the application, and are not a limitation on the application.

[0042] It can be understood that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

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

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

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

[0046] It can be understood that in the flowcharts and block diagrams of the present application, the architecture, functions and operations of possible implementations of the systems, devices, apparatuses and methods according to the embodiments of the present application are shown. Each block in the flowchart or block diagram can represent a unit, module, program segment, code, which contains executable instructions for implementing the specified functions. Moreover, each block or combination of blocks in the block diagram and flowchart can be implemented by a hardware-based system for implementing the specified functions, or 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 application can be implemented in the form of software or hardware, for example, the units and modules can be located in a processor.

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

[0049] Compared with the Coriolis force mass flowmeter measurement method, although the measurement method of the vortex flowmeter is not as accurate as the Coriolis force method, the Coriolis force mass flowmeter for measuring small flow has high cost because it is an imported product, and it is difficult to maintain after sale.

[0050] Thermal mass flow controller has control function, and has innate superiority in gas measurement. However, it also has obvious defects: the structure is mostly in the form of experimental equipment, and the structural strength is poor; the composition of the gas is required to be high; the temperature of the medium is limited, and the measurement and control of high-temperature gas cannot be realized.

[0051] Therefore, in some related technologies, a vortex flowmeter is used to measure the gas flow, and the measurement signal is transmitted to a control system such as a PLC (Programmable Logic Controller) or a DCS (Distributed Control System). After the control system is operated, the output is output to the electric regulating valve to adjust the opening degree, so as to realize the control of the gas flow. Since the electric regulating valve has a temperature requirement of not more than 70℃ for the medium, and the minimum diameter of the vortex flowmeter is 15mm, it is impossible to measure and control the small flow of high-temperature steam, resulting in inaccurate measurement results. In addition, the long-distance transmission of the measurement signal causes signal attenuation, which is easily disturbed by other strong electric signals, further affecting the control accuracy; the flow measurement and valve control are limited by the long running period of the entire control system program. Therefore, in actual use, the flow measurement and electric regulating valve control have poor coordination, low control accuracy, and especially when the working condition changes, the flow control often fluctuates, affecting the stability of the process. The measurement and control device of the embodiment is used to solve the above problems.

[0052] Embodiment 1

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

[0054] As shown in Figure 1 A gas small flow measurement and control device includes a vortex flowmeter, a pneumatic regulating valve, and a controller.

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

[0056] In the embodiment, the controller is configured to acquire a measurement result of the vortex flowmeter for the small gas flow, and output an opening degree control instruction of the pneumatic regulating valve based on a flow control target value, and the pneumatic regulating valve is configured to perform corresponding action of the valve opening degree according to the opening degree control instruction of the controller, so as to realize measurement and control of the small gas flow in the pipeline. The controller can be located in a local PLC or DCS system, or in a remote PLC or DCS system. The measurement and control device for the small gas flow in the embodiment can realize measurement and control of the small gas flow by developing a new vortex flowmeter with a small caliber (i.e., the caliber of the measurement tube is in the range of [6, 8] mm) and integrating valve control.

[0057] It can be understood that, at the same flow value, the larger the caliber of the measurement tube, the lower the flow rate of the medium, and when the flow rate is lower than the minimum flow rate of the flowmeter, the flowmeter cannot perform accurate measurement. At present, the minimum caliber of the vortex flowmeter on the market is DN15, and by redesigning the structure of the vortex flowmeter, the caliber of the measurement tube is reduced to increase the flow rate of the medium in the measurement tube, which can effectively reduce the lower limit of the flowmeter.

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

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

[0060] In this embodiment, the controller based on the fuzzy PID control algorithm can realize accurate control of the micro flow, which is beneficial to improve the accuracy of the flow measurement result. Compared with the traditional PID control algorithm, the fuzzy PID control algorithm of the 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 handle the uncertainty and changes of the system, so that it can automatically adjust the control parameters to maintain good control performance when facing system parameter changes and external disturbances. (2) Good robustness: the fuzzy PID control algorithm has strong anti-interference ability, and can maintain stable control effect even if the dynamic characteristics of the system change. (3) High control precision. (4) Easy to implement: compared with other complex control algorithms, the fuzzy PID control algorithm is relatively simple to implement, and the calculation amount is small, which is suitable for real-time control system. (5) Parameters are easy to adjust: the fuzzy PID controller adjusts the PID parameters online using fuzzy rules, not relying on fixed gain values. This flexibility makes the fuzzy PID controller more effective in dealing with complex processes.

[0061] The traditional measurement and control device mostly uses a PID controller to realize constant flow control when controlling flow. When the measurement accuracy and the stability of the medium deteriorate, the output flow of the flow controller will fluctuate, affecting the subsequent process operation. In this embodiment, especially for overheat steam and other media, the density changes with the change of temperature and pressure, and accurate temperature and pressure compensation is needed to determine the density, so as to calculate the mass flow. Therefore, in the constant flow control of the flow, the control mainboard of the controller is redesigned, the data processing capability, operation capability and storage capability of the controller are comprehensively improved, and an advanced dynamic compensation algorithm is introduced to improve the gas flow accuracy and stability.

[0062] The implementation of the dynamic compensation algorithm is as follows:

[0063] The traditional PID control is the most commonly used control algorithm in control systems. The essence of PID regulation is to perform proportional, integral, and differential function operations on the input deviation value, and use the operation result for output. In the PID controller, the selection of Kp value depends on the response speed of the system. Increasing Kp can improve the response speed and reduce the steady-state deviation; however, a too large Kp value will produce a large overshoot, and even make the system unstable; reducing Kp can reduce the overshoot and improve stability, but a too small Kp will slow down the response speed and prolong the regulation time. The fuzzy controller has the characteristics of fast regulation speed and good robustness compared with the PID algorithm, but the disadvantage of poor steady-state accuracy is also obvious. In this embodiment (for example Figure 2The PID control algorithm and the fuzzy control algorithm with dynamic compensation are used to overcome the defects of the simple PID algorithm to achieve better precision and stability of the flow control. In the measurement process of the measurement and control device, the flow measurement and flow control of the medium are a closed loop process. The changes of the gas pressure and temperature in the process pipeline directly affect the measurement effect. When the measurement fluctuates, the valve control system will make corresponding adjustments according to the measurement changes, so that the output of the entire gas flow will fluctuate and oscillate. Figure 2 As shown in the figure, the controller of the fuzzy PID control algorithm of the embodiment includes a PID controller and a fuzzy controller, the execution element is a pneumatic regulating valve, and the measurement element is a vortex flowmeter. When the fuzzy controller is introduced, the size of the flow data response error e and its change rate (dE / dt) is detected at each sampling time, and then the correction amount of the PID parameter is obtained according to the prepared fuzzy rule. In this way, the PID controller can actively adjust the size of its own parameter according to the change of the system response, thereby enhancing the dynamic response performance of the system and the robustness to external interference. In this way, the single PID control parameter in the traditional PID control can be avoided, and the reasonable compensation and response to the complex changes of the working conditions can be made, thereby improving the stability and precision 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 located within a range of [1.5h, 2.1h] from the incident flow surface, where h is the equivalent diameter of the gas flow pipeline. Figure 3 As shown in the figure, the vortex generator is a vortex generator.

[0065] In some related technologies, the contact area of the probe with the fluid is large, which is easily affected by the disturbance of the fluid, resulting in poor stability of the measurement signal. The installation position of the probe is not scientific, resulting in low measurement signal collection efficiency and inaccurate measurement results. In order to solve the demand for small flow measurement and improve the measurement accuracy of the vortex flowmeter, the installation position of the probe is determined by a simulation analysis method. Determining the installation position of the probe of the vortex sensor includes: performing experiments on vortex generators of different sizes in two-dimensional and three-dimensional flow fields; determining the installation position of the probe of the vortex sensor based on signal characteristics of pressure signals and velocity signals at different positions, wherein the signal characteristics include at least one of the following: signal intensity, signal-to-noise ratio, and linearity.

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

[0067] A geometric model is established: a CAD software (such as SolidWorks) is used to establish a calculation region model according to the actual diameter DN8 of the vortex flowmeter, as shown in the figure. Figure 3as shown.

[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, for example, 5 mm. The remaining parameters are selected in the default state, and then the mesh solver is run to obtain the total number of fluid meshes.

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

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

[0071] Result analysis: through the simulation setting, when the fluid flows in the flow passage, the vortexes are generated alternately and periodically on both sides of the vortex generator. The pressure acting on the vortex generator changes periodically.

[0072] By analyzing the dynamic pressure variation curves of different pressure monitoring points, as shown in Figure 4 and Figure 5 , the strength of the dynamic pressure signal is different at different positions of the pressure monitoring points. The basic change rule is that as the distance from the vortex generator increases, the vortex street signal strength first increases and then decreases. It is found that when the distance from the vortex generator is about 1.5h-2.1h (h is the equivalent diameter of the flow passage), the vortex street signal is the strongest, that is, the best placement position of the sensor probe.

[0073] Optionally, the probe of the vortex street sensor adopts 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 configured to extract measurement results of the vortex street flowmeter based on HHT time-frequency analysis, and perform adaptive filtering and instantaneous frequency statistics on the extracted measurement results based on empirical mode decomposition (EMD).

[0076] In the embodiment, the turbulence, pulsation, instability and non-uniformity of the flow field of the flow medium in the pipeline and the low-frequency swing noise of the fluid have a great influence on the measurement result when measuring a small flow, and affect the accuracy of the measurement result. Therefore, the HHT time-frequency analysis is introduced in the signal extraction of the measurement result in the embodiment, which is used as a means of adaptive filtering to filter out the noise components in the signal, and the probability density statistics of the instantaneous frequency of each trend component is used as an empirical mode decomposition criterion. Through experiments, it is verified that the method can greatly expand the lower limit of the vortex flowmeter measurement on the basis of ensuring linearity, which is conducive to improving the accuracy of the measurement result.

[0077] Optionally, the controller comprises a control unit. The control unit is configured to control the opening degree of the pneumatic regulating valve based on the pneumatic proportional servo system. The pneumatic regulating valve adopts a needle-shaped valve core, so that the flow characteristics of the pneumatic regulating valve meet the equal percentage characteristics.

[0078] In view of the unstable control of the regulating valve in the related art, the embodiment adopts a pneumatic regulating valve, and controls the opening degree of the pneumatic regulating valve based on a pneumatic proportional servo system. In addition, the valve core of the pneumatic regulating valve is improved, and a needle-shaped valve core is adopted, so that the flow characteristics of the pneumatic regulating valve meet the equal percentage characteristics, the control precision is improved, and the accuracy of the measurement result is improved.

[0079] In view of the unstable control of the regulating valve in the related art, the embodiment adopts a pneumatic regulating valve, and controls the opening degree of the pneumatic regulating valve based on a pneumatic proportional servo system. In addition, the valve core of the pneumatic regulating valve is improved, and a needle-shaped valve core is adopted, so that the flow characteristics of the pneumatic regulating valve meet the equal percentage characteristics, the control precision is improved, and the accuracy of the measurement result is improved.

[0080] The valve core is improved, in the structure of the small-diameter regulating valve, the valve core part is the key component for flow control. Therefore, the structure form of the valve core is related to the quality of flow control. In the embodiment, the small-diameter regulating valve adopts a needle-shaped valve core, the structure design of the valve core is optimized by applying the simulation software and correcting the curve point by point, so that the flow characteristics of the regulating valve meet the requirements of the equal percentage characteristic cylindrical needle-shaped valve core structure, and the size of the needle-shaped valve core is obtained to meet the control of small-diameter micro-flow. 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; the three-dimensional model is meshed; the three-dimensional model after meshing is simulated under different valve openings to obtain the flow characteristic curve of the three-dimensional model; and the initial valve core profile is optimized based on the flow characteristic curve to obtain the size of the needle-shaped valve core.

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

[0082] Step S11, the original design model valve core structure adopts a simple conical structure. The regulating valve is simulated to establish a three-dimensional model: selecting the opening degree of 20%, 40%, 60%, 80% and 100% of the model, connecting the straight pipe section with an inner diameter of 10 times the length at both ends of the valve body; the whole three-dimensional simulation model is divided into multiple parts, the valve body is dissected into a grid structure, and is set to a relatively small size, so as to enhance the accuracy of iterative calculation during simulation.

[0083] Step S12, for the model, the pressure at the inlet is set to 100kP, and the outlet pressure is set to 0kPa. The ratio of the flow of the model at different openings to their respective maximum flow is calculated by simulation, and the flow curve of the model is compared 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 characteristic is calculated to optimize the valve core profile of the regulating valve, and finally the valve core profile design is completed, that is, the size design of the needle-shaped valve core is completed.

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

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

[0086] In the embodiment, the flow control target value refers to the target flow size set in the controller, which is a 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 can be a split-type gas micro-flow measurement and control device. The integrated measurement and control device adopts embedded technology and integration technology through modular design, reduces the size of the device, improves the anti-interference performance and reliability, and introduces a microprocessor, so that the measurement and control device becomes a combination of hardware and software, can make judgments, decisions, automatic corrections and compensations according to input signals, realize precise control, and improve the flow measurement accuracy.

[0087] The gas micro-flow measurement and control device provided in the embodiment adopts a vortex flowmeter capable of measuring high-temperature medium, optimally designs the measuring pipe diameter of the vortex flowmeter, and adopts a high-temperature-resistant pneumatic control valve for adjusting the flow size of the gas, and then controls the opening of the pneumatic control valve based on the measurement result of the vortex flowmeter, so as to realize the measurement and control of the flow of high-temperature steam. Since the measuring pipe diameter of the vortex flowmeter is optimally designed, and the pneumatic control valve has fast response speed, good linear characteristic, and low flow characteristic, the accurate measurement of the micro-flow of high-temperature steam is realized. The problems of difficult measurement, low accuracy, large size, and slow adaptability to working condition changes of the traditional flowmeter are solved, and an effective means for accurate measurement of small flow of a production line is provided. In addition, the optimization of the control algorithm of the controller, the determination of the installation position of the probe of the vortex sensor, and the improvement of the valve core of the pneumatic control valve further improve the accuracy of the measurement result and the control accuracy.

[0088] Embodiment 2

[0089] The 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 in embodiment 1, and the installation method comprises the following steps.

[0090] In step 201, the vortex flowmeter is installed on the pipeline through which the gas flows, wherein the measuring pipe diameter of the vortex flowmeter is within the value range [6, 8] millimeters.

[0091] In step 202, the pneumatic control valve is installed on the pipeline through which the gas flows.

[0092] In step 203, the controller is electrically connected with the vortex flowmeter and the pneumatic control valve.

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

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

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

[0096] Experiments are conducted on vortex generators of trapezoidal columns of different sizes in two-dimensional and three-dimensional flow fields respectively;

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

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

[0099] Optionally, determining the size of the needle valve core comprises: establishing a three-dimensional model of the pneumatic control valve based on simulation software, the three-dimensional model comprising an initial valve core; performing meshing on the three-dimensional model; performing simulation calculation on the three-dimensional model after meshing at different valve opening degrees to obtain a flow characteristic curve of the three-dimensional model; and optimizing the profile of the initial valve core based on the flow characteristic curve to obtain the size of the needle valve core.

[0100] It can be understood that the above embodiments are only exemplary embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered to be within the protection scope of the present application.

Claims

1. A device for measuring and controlling minute gas flow rates, characterized in that, The vortex flowmeter, the pneumatic regulating valve, the controller, The vortex flowmeter is arranged on the pipeline through which the gas flows, and is used for measuring the flow of the gas. The vortex flowmeter comprises a measuring pipe, a vortex sensor and a vortex generator. The diameter of the measuring pipe is in the range of [6, 8] millimeters. 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 arranged in the range of [1.5h, 2.1h] from the incident flow surface. h is the equivalent diameter of the pipeline through which the gas flows. The probe of the vortex sensor is a piezoelectric ceramic probe. The vortex generator comprises a trapezoidal column vortex generator. The pneumatic regulating valve is arranged on the pipeline through which the gas flows, and is used for adjusting the flow of the gas. The pneumatic regulating valve adopts a needle-shaped valve core. The controller is electrically connected with the vortex flowmeter and the pneumatic regulating valve, and is used for receiving the measurement result of the vortex flowmeter and controlling the opening degree of the pneumatic regulating valve.

2. The apparatus of claim 1, wherein, The controller adopts a controller based on a fuzzy PID control algorithm.

3. The apparatus of claim 1, wherein, The controller comprises a signal extraction unit, The signal extraction unit is used for extracting the measurement result of the vortex flowmeter based on HHT time-frequency analysis, and is used for adaptively filtering and statistically analyzing the instantaneous frequency of the extracted measurement result based on empirical mode decomposition (EMD).

4. The apparatus of claim 1, wherein, The controller comprises a control unit, The control unit is used for controlling the opening degree of the pneumatic regulating valve based on a pneumatic proportional servo system.

5. The apparatus of claim 1, wherein, The controller comprises a touch display screen, The touch display screen is used for displaying the measurement result of the vortex flowmeter and receiving a flow control target value.

6. A method of installing a gas micro-flow measuring and controlling device, characterized by, The method comprises the following steps: The vortex flowmeter is arranged on the pipeline through which the gas flows. The vortex flowmeter comprises a measuring pipe, a vortex sensor and a vortex generator. The diameter of the measuring pipe is in the range of [6, 8] millimeters. 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 arranged in the range of [1.5h, 2.1h] from the incident flow surface. h is the equivalent diameter of the pipeline through which the gas flows. The probe of the vortex sensor is a piezoelectric ceramic probe. The vortex generator comprises a trapezoidal column vortex generator. The pneumatic regulating valve is arranged on the pipeline through which the gas flows. The pneumatic regulating valve adopts a needle-shaped valve core. The controller is electrically connected with the vortex flowmeter and the pneumatic regulating valve.

7. The installation method according to claim 6, wherein Before the vortex flowmeter is arranged on the pipeline through which the gas flows, the method further comprises the following step: determining the installation position of the probe of the vortex sensor, The method of determining the installation position of the probe of the vortex sensor comprises the following steps: Experiments are respectively conducted on trapezoidal column vortex generators of different sizes in two-dimensional and three-dimensional flow fields. The installation position of the probe of the vortex sensor is determined based on the signal characteristics of the pressure signal and the velocity signal at different positions. The signal characteristics include at least one of the following: signal intensity, signal-to-noise ratio and linearity.

8. The mounting method according to claim 7, wherein Before the pneumatic regulating valve is arranged on the pipeline through which the gas flows, the method further comprises the following step: determining the size of the needle-shaped valve core, The method of determining the size of the needle-shaped valve core comprises the following steps: A three-dimensional model of the pneumatic regulating valve is established based on simulation software. The three-dimensional model comprises an initial valve core. The three-dimensional model is meshed. The three-dimensional model after meshing is simulated under different valve opening degrees 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 size of the needle-shaped valve core.

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