A flowmeter calibration system and method with water division pressure stabilization function

Abstract

The application provides a flow meter calibration system and method with water distribution and pressure stabilization function, comprising a double-pump liquid supply module for providing basic flow, a water distribution and pressure stabilization module for stabilizing the flow provided by the double-pump liquid supply module, and a flow meter calibration module for calibrating the flow meter to be calibrated. The double-pump liquid supply module comprises a liquid storage tank and two liquid supply pumps connected in parallel to the liquid outlet of the liquid storage tank, wherein the two liquid supply pumps comprise a main pump and an auxiliary pump. A proportional valve is arranged on the pipeline at the end of the flow meter calibration module, and the proportional valve is used for adjusting the flow size through the flow meter calibration module. The application further comprises a controller which is signal-connected with the liquid supply pump and the proportional valve, respectively, and the controller is used for adjusting the rotating speed of the liquid supply pump according to the pressure feedback signal of the water distribution and pressure stabilization module, so as to stabilize the system pressure. The application realizes high-precision, high-efficiency and high-automation flow meter calibration.

Description

Technical Field

[0001] This invention belongs to the field of flow meter calibration technology, specifically relating to a flow meter calibration system and method with water separation and pressure stabilization functions. Background Technology

[0002] Flow metering is a fundamental technology in fields such as energy trade settlement, industrial process control, and environmental protection monitoring. According to national metrological verification regulations JJG 897-2013 "Ultrasonic Flow Meters" and JJG 643-2003 "Standard Meter Method Flow Standard Devices," the calibration of flow meters with an accuracy of 0.5 or higher must meet extremely stringent fluid environment requirements. Currently, domestic and international flow meter calibration techniques still generally have shortcomings.

[0003] Most existing flow meter calibration systems still rely on a passive pressure stabilization mode of "pressure stabilizing tank + mechanical pressure regulating valve". For example, Chinese patent CN107860444A discloses a liquid flow standard device and its calibration method, which uses a pressure stabilizing container (4) to eliminate pressure pulsation generated by the water pump. However, this scheme relies on a single pressure stabilizing container for passive pressure stabilization. Once the pre-charge pressure of the pressure stabilizing container is set, it cannot be adjusted online, and the system pressure cannot be actively adjusted according to changes in operating conditions. More importantly, the pressure pulsation generated by the water pump has a wide frequency band characteristic, including high-frequency pulsation generated by the passing frequency of the blades and low-frequency fluctuations caused by the inherent frequency of the pipeline system. A single pressure stabilizing container cannot effectively suppress the pulsation across the entire frequency band. The response time of the mechanical pressure regulating valve is usually between 0.5 and 2 seconds. When the valve opening changes or the branch switches, the system pressure will oscillate around the new set value for tens of seconds before stabilizing again. Passive pressure stabilization can only correct pressure fluctuations after the fact and cannot actively predict and compensate for disturbances in advance. When multiple branches switch simultaneously, the superposition of disturbances may cause the pressure overshoot to reach 5% to 10% of the set value, far exceeding the ±0.2% fluctuation range allowed by the 0.5-level calibration.

[0004] Therefore, there is an urgent need for a new flow meter calibration system and method to meet the stringent requirements for calibrating flow meters of grade 0.5 and above. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the above shortcomings, the present invention provides a flow meter calibration system and method with water separation and pressure stabilization functions, which integrates functions such as water separation, pressure stabilization, vibration reduction and pressure sensing, and adopts a control strategy of active pressure closed-loop control and flow feedforward compensation to achieve high-precision, high-efficiency and highly automated flow meter calibration.

[0006] Technical Solution: To achieve the above objectives, this invention provides a flow meter calibration system with a water distribution and pressure stabilization function, comprising: a dual-pump liquid supply module for providing a base flow rate; a water distribution and pressure stabilization module for distributing and stabilizing the fluid supplied by the dual-pump liquid supply module; and a flow meter calibration module for calibrating the flow meter to be calibrated. The dual-pump liquid supply module includes a storage tank and two supply pumps connected in parallel to the liquid inlet of the storage tank. The two supply pumps include a main pump and an auxiliary pump. The main pump is a variable frequency screw pump, used to output a pulse-free base flow rate. The auxiliary pump is a variable frequency plunger pump, used for fine-tuning and flow feedforward compensation at a small displacement based on the base flow rate. The two pumps work together to optimize the system's effective adjustment range and response speed. A proportional valve is provided on the end pipeline of the flow meter calibration module, used to adjust the flow rate passing through the flow meter calibration module. A controller is also included, connected to both the supply pumps and the proportional valve. The controller adjusts the speed of the supply pumps based on the pressure feedback signal from the water distribution and pressure stabilization module to stabilize the system pressure.

[0007] Furthermore, in the aforementioned flowmeter calibration system with water distribution and pressure stabilization function, the water distribution and pressure stabilization module includes a tank, a pressure stabilizing buffer tank, and a diaphragm damper. The tank contains a buffer pressure stabilizing chamber and several water distribution chambers. The inlets of the buffer pressure stabilizing chambers are connected to two liquid supply pumps, and the outlets of the water distribution chambers are connected to the flowmeter calibration module. A diaphragm damper is installed on the tank and is connected to the buffer pressure stabilizing chamber to absorb high-frequency flow pulsations generated by the liquid supply pumps. The pressure stabilizing buffer tank is connected to the buffer pressure stabilizing chamber and is used to absorb low-frequency pressure fluctuations. The cutoff frequency of the diaphragm damper is higher than that of the pressure stabilizing buffer tank, and the two complement each other across the entire frequency range to suppress high-frequency pulsations and low-frequency fluctuations. A pressure sensor connected to the controller signal is directly inserted into the wall of the buffer pressure stabilizing chamber to collect the pressure signal of the buffer pressure stabilizing chamber and send the signal to the controller.

[0008] Furthermore, in the aforementioned flowmeter calibration system with water separation and pressure stabilization function, the flowmeter calibration module includes a standard flowmeter and a flowmeter to be calibrated, arranged sequentially along the pipeline. The flowmeter to be calibrated is connected to a proportional valve via a pipeline, and the proportional valve is connected to a storage tank via a return pipe, used to return the fluid to the storage tank. The standard flowmeter is a Coriolis mass flowmeter, and the flowmeter to be calibrated is a piezoelectric ceramic vortex water flow sensor. The Coriolis mass flowmeter, as the standard meter, has extremely high measurement accuracy (up to 0.1 grade and above), and can directly measure mass flow rate, providing a reliable measurement benchmark for calibration.

[0009] Furthermore, in the aforementioned flowmeter calibration system with water distribution and pressure stabilization function, a first pressure gauge and a second pressure gauge are installed on the pipelines on both sides of the standard flowmeter, and a third pressure gauge is installed on the pipeline of the flowmeter to be calibrated on the side furthest from the standard flowmeter. By arranging these three pressure gauges, the pressure loss between the standard flowmeter and the flowmeter to be calibrated can be corrected, eliminating flow measurement deviations caused by pipeline pressure drop.

[0010] Furthermore, in the aforementioned flowmeter calibration system with water separation and pressure stabilization function, the flowmeter to be calibrated is installed on a separable pipe assembly. The separable pipe assembly includes a fixed base plate arranged along the pipe extension direction. At least two fixed seats are installed on the fixed base plate near the standard flowmeter, and a fixed pipe containing the standard flowmeter is fixed on each fixed seat. A second pressure gauge is installed on the fixed pipe. A sliding plate and a reciprocating drive mechanism are provided on the fixed base plate away from the standard flowmeter. The sliding plate is slidably connected to the fixed base plate via a slide rail mechanism, and the drive unit of the reciprocating drive mechanism is driven by the sliding plate. A movable pipe is fixed to the surface of the sliding plate. The reciprocating drive mechanism drives the sliding plate to reciprocate, causing the fixed pipe and the movable pipe to move closer together or separate. The inlet and outlet of the flowmeter to be calibrated are connected to the fixed pipe and the movable pipe, respectively.

[0011] The above design makes the clamping and disassembly of the flow meter to be calibrated extremely convenient. The operator only needs to place the flow meter to be calibrated between the fixed pipe and the movable pipe, and use the reciprocating drive mechanism to push the slide plate to bring the movable pipe closer to the fixed pipe. The flow meter to be calibrated and the pipeline connection can be completed by using the quick coupling. After calibration, the operation can be reversed for quick disassembly, which improves the efficiency of batch calibration.

[0012] Furthermore, in the aforementioned flowmeter calibration system with water distribution and pressure stabilization function, the reciprocating drive mechanism includes a base fixed to the end of a fixed base plate. A drive rod is slidably connected to the base via a sliding sleeve. The drive rod extends towards and connects to the sliding plate. A hinge seat is provided on the side of the base away from the sliding plate, and the hinge seat is hinged to the sliding sleeve. A handle is hinged to the hinge seat, and the handle is hinged to the end of the drive rod. The handle includes a hinge portion hinged to the drive rod and a force-applying portion, the hinge portion and the force-applying portion being integrally arranged at an angle.

[0013] Furthermore, in the aforementioned flowmeter calibration system with water distribution and pressure stabilization function, each water distribution chamber corresponds to a flowmeter calibration module. The proportional valves of each flowmeter calibration module are configured to switch sequentially at preset time intervals to avoid the superposition of disturbances from multiple channels. The water distribution chambers are isolated from each other by partitions, and pressure disturbances in any branch are attenuated within that branch's water distribution chamber, reducing interference to other branch water distribution chambers and achieving fluid dynamic decoupling between the branches.

[0014] Furthermore, in the aforementioned flowmeter calibration system with water distribution and pressure stabilization function, the flowmeter calibration module comprises at least three sets, with the pipe diameters of the at least three sets of flowmeter calibration modules arranged in ascending order, and the inlets of the three sets of flowmeter calibration modules respectively connected to the outlet of the water distribution chamber. By setting multiple sets of flowmeter calibration modules with different pipe diameters, the calibration requirements of flowmeters of different diameters can be met simultaneously, expanding the applicability of the system.

[0015] Furthermore, in the aforementioned flowmeter calibration system with water separation and pressure stabilization function, the flowmeter calibration module 3 is equipped with an air purging device on its pipeline to remove residual air from the pipeline. This air purging device effectively eliminates the influence of residual air bubbles in the pipeline on the flow measurement accuracy, ensuring the accuracy of the calibration results.

[0016] A flow meter calibration method, applied to the aforementioned flow meter calibration system, is characterized by comprising the following steps: S1: Start the dual-pump liquid supply module. The main pump outputs a pulse-free basic flow rate, while the auxiliary pump performs fine-tuning with a small displacement. The fluid enters the buffer and pressure-stabilizing chamber of the water distribution and pressure-stabilizing module. High-frequency pulsations are absorbed by the diaphragm damper, and low-frequency fluctuations are absorbed by the pressure-stabilizing buffer tank. The stabilized fluid enters the flow meter calibration module through the water distribution chamber and is adjusted to the target flow rate through the proportional valve.

[0017] S2: Based on the feedback signal of the pressure sensor directly inserted into the wall of the buffer pressure stabilizing chamber, an incremental PID algorithm is used to adjust the speed of the liquid supply pump with a control cycle of 10ms, forming a pressure closed loop, so that the pressure of the buffer pressure stabilizing chamber tracks the set value.

[0018] S3: When the proportional valve opening command changes, a compensation speed signal is output to the liquid supply pump 10 to 50 ms before the proportional valve actually operates, so that the pump flow output can synchronously cancel the expected valve flow change, thus achieving flow feedforward compensation.

[0019] S4: Simultaneously, the pressure sensor collects the pressure signal, and the standard flow meter collects the flow signal. When the pressure is stable but the flow rate deviates from the set value, the auxiliary pump makes a fine adjustment; when the flow rate is stable but the pressure deviates from the set value, the main pump regulates.

[0020] S5: During multi-channel parallel calibration, the proportional valves corresponding to each water distribution chamber switch sequentially in a step manner at 100ms intervals to avoid the superposition of multiple disturbances.

[0021] S6: Temperature sensors are installed in the water distribution and pressure stabilization module and the liquid storage tank respectively to measure the temperature of the medium, and temperature drift compensation is performed on the reading of the flow meter to be calibrated according to the density correction formula.

[0022] The density correction formula is: In the formula, For the medium at the measured temperature The actual density below, The density of the medium at a reference temperature of 20°C. The coefficient of volumetric expansion of the medium is given in °C. -1 ; The temperature is the actual temperature of the medium measured by the temperature sensor, in °C; constant 20 is the reference temperature.

[0023] S7: Read the pressure values ​​from the first, second, and third pressure gauges respectively. Correct the flow rate reading of the standard flow meter using the following formula: In the formula, The raw flow reading of the standard flow meter. The corrected standard flow rate value. The pressure value measured by the first pressure gauge. The pressure value is measured by the second pressure gauge.

[0024] Correct the flow rate at position 32 of the flow meter to be calibrated using the following formula: In the formula, This is the corrected flow rate value at the location of the flow meter to be calibrated. The pressure value measured by the second pressure gauge. The pressure value is measured by the third pressure gauge.

[0025] If the difference between the pressure value measured by the first pressure gauge and the pressure value measured by the second pressure gauge is less than a preset threshold, the first pressure compensation is skipped. If the difference between the pressure value measured by the second pressure gauge and the pressure value measured by the third pressure gauge is less than a preset threshold, the second pressure compensation is skipped.

[0026] S8: Compare the flow rate value of the flow meter to be calibrated after temperature drift compensation and pressure compensation with the output flow rate value of the flow meter to be calibrated, calculate the indication error, and complete the calibration.

[0027] As can be seen from the above technical solution, the present invention has the following beneficial effects: ①This invention integrates the buffer pressure stabilizing chamber, water distribution chamber and diaphragm damper on the same tank body, eliminating the need for long pipeline connections between the functions, reducing the problems of volume lag and pressure transmission lag in pipeline connections, and reducing the total pipeline length and the number of leakage points.

[0028] ② This invention uses a diaphragm damper to absorb the high-frequency flow pulsation generated by the liquid supply pump, and a pressure stabilizing buffer tank to absorb the low-frequency pressure fluctuations, forming a full-band complementary suppression of high-frequency pulsation and low-frequency fluctuations, thereby improving the system pressure stability.

[0029] ③ In this invention, the main pump is a variable frequency screw pump, which outputs a pulse-free basic flow rate to ensure flow stability under high flow conditions; the auxiliary pump is a variable frequency plunger pump, which is finely adjusted with a small displacement based on the main pump to improve the system response range and response speed.

[0030] ④ This invention adjusts the speed of the liquid supply pump through the feedback signal of the pressure sensor; at the same time, it outputs a compensation speed signal to the liquid supply pump in advance before the proportional valve actually operates, so as to realize flow feedforward compensation, reduce pressure overshoot, and improve the stability of system pressure.

[0031] ⑤ In this invention, each water distribution chamber corresponds to a flow meter calibration module, and each proportional valve switches sequentially in a stepwise manner at a preset time interval to avoid the superposition of multiple disturbances, thereby realizing multi-channel parallel calibration and improving calibration efficiency. Attached Figure Description

[0032] Figure 1 This is a front view of the flow meter calibration system with water separation and pressure stabilization function of the present invention; Figure 2 This is a schematic diagram of the flow meter calibration system with water separation and pressure stabilization function of the present invention; Figure 3 This is a schematic diagram of the structure of the water distribution and pressure stabilization module; Figure 4 This is a schematic diagram of the interior of the tank. Figure 5 This is a schematic diagram of the flow meter calibration module. Figure 6 This is a schematic diagram of the structure of the separable pipe assembly; Figure 7 This is a schematic diagram of the reciprocating drive mechanism.

[0033] In the diagram: 1. Dual-pump liquid supply module, 11. Liquid storage tank, 12. Liquid supply pump, 2. Water distribution and pressure stabilization module, 21. Tank body, 211. Buffer and pressure stabilization chamber, 212. Water distribution chamber, 22. Pressure stabilizing buffer tank, 23. Diaphragm damper, 3. Flow meter calibration module, 31. Standard flow meter, 32. Flow meter to be calibrated, 33. First pressure gauge, 34. Second pressure gauge, 35. Third pressure gauge, 4. Separable pipe assembly, 41. Fixed base plate, 42. Fixed seat, 43. Fixed pipe, 44. Slide plate, 45. Reciprocating drive mechanism, 451. Base, 452. Drive rod, 453. Hinge seat, 454. Handle, 46. Movable pipe, 5. Proportional valve. Detailed Implementation Example

[0034] like Figure 1-2The flow meter calibration system shown includes a dual-pump liquid supply module 1 for providing a base flow rate. A liquid distribution and pressure stabilization module 2 is used to distribute and stabilize the pressure of the fluid supplied by the dual-pump liquid supply module 1. A flow meter calibration module 3 is used to calibrate the flow meter to be calibrated. The dual-pump liquid supply module 1 includes a storage tank 11 and two supply pumps 12 connected in parallel to the inlet of the storage tank 11. The two supply pumps 12 include a main pump and an auxiliary pump. The main pump is a variable frequency screw pump, used to output a pulse-free base flow rate. The auxiliary pump is a variable frequency plunger pump, used for small-displacement fine-tuning and flow feedforward compensation based on the base flow rate. The dual pumps work together to optimize the system's effective adjustment range and response speed.

[0035] A proportional valve 5 is installed on the end pipeline of the flow meter calibration module 3. The proportional valve 5 is used to adjust the flow rate through the flow meter calibration module 3. A controller is also included. The controller is connected to the liquid supply pump 12 and the proportional valve 5 respectively. The controller is used to adjust the speed of the liquid supply pump 12 according to the pressure feedback signal of the water distribution and pressure stabilizing module 2 to stabilize the system pressure.

[0036] like Figure 2-4 The flow meter calibration system shown has a water distribution and pressure stabilization function. The water distribution and pressure stabilization module 2 includes a tank 21, a pressure stabilizing buffer tank 22, and a diaphragm damper 23. The tank 21 contains a buffer pressure stabilizing chamber 211 and several water distribution chambers 212. The buffer pressure stabilizing chamber 211 and the water distribution chambers 212 are separated by a perforated plate, and the water distribution chambers 212 are separated by partitions. The inlet of the buffer pressure stabilizing chamber 211 is connected to two liquid supply pumps 12, and the outlet of the water distribution chambers 212 is connected to the flow meter calibration module 3. The buffer pressure stabilizing chamber 211 and the several water distribution chambers 212 are... A diaphragm damper 23 is installed on the tank body 21, which is connected to the buffer pressure stabilizing chamber 211 to absorb high-frequency flow pulsations generated by the liquid supply pump 12. The pressure stabilizing buffer tank 22 is also connected to the buffer pressure stabilizing chamber 211 to absorb low-frequency pressure fluctuations. The damper has a corrugated metal diaphragm inside, dividing its interior into a gas chamber and a liquid chamber. The liquid chamber is connected in parallel to the side wall of the buffer pressure stabilizing chamber 211. When the high-frequency pressure pulsations generated by the rotation of the liquid supply pump 12 are transmitted to the liquid chamber of the diaphragm damper 23, the pressure in the liquid chamber pushes the diaphragm to compress the nitrogen in the gas chamber. The nitrogen, acting as an elastic medium, converts the pulsating kinetic energy into compressible energy and stores it. During the pulsating negative pressure phase, the energy is released, absorbing the pulsation. The cutoff frequency of the diaphragm damper 23 is approximately 5Hz. The pressure stabilizing buffer tank 22 has a built-in flexible rubber bladder filled with nitrogen and surrounded by a liquid medium. The effective volume of the pressure stabilizing buffer tank 22 is 5 to 15 times the volume of the main body of the water distributor. The cutoff frequency of the pressure stabilizing buffer tank 22 is approximately 0.1 Hz. The cutoff frequency of the diaphragm damper 23 is higher than that of the pressure stabilizing buffer tank 22. The two complement each other in suppressing high-frequency pulsations and low-frequency fluctuations across the entire frequency band, thereby improving the system pressure stability.

[0037] A pressure sensor, which is connected to the controller signal, is directly inserted into the wall of the buffer pressure regulating chamber 211 to collect the pressure signal of the buffer pressure regulating chamber 211 and send the signal to the controller.

[0038] like Figure 5 The flow meter calibration system shown has a water distribution and pressure stabilization function. The flow meter calibration module 3 includes a standard flow meter 31 and a flow meter 32 to be calibrated, arranged sequentially along the pipeline. The flow meter 32 to be calibrated is connected to a proportional valve 5 via a pipeline. The proportional valve 5 is connected to a storage tank 11 via a return pipe, used to return the fluid to the storage tank 11. The proportional valve 5 is an electrically operated proportional valve used to adjust the flow rate through the flow meter calibration module 3. The standard flow meter 31 is a Coriolis mass flow meter, and the flow meter 32 to be calibrated is a piezoelectric ceramic vortex water flow sensor. The Coriolis mass flow meter, as the standard flow meter 31, has extremely high measurement accuracy (up to 0.1 grade and above), and can directly measure mass flow rate, providing a reliable measurement benchmark for calibration.

[0039] In this embodiment, a first pressure gauge 33 and a second pressure gauge 34 are installed on the pipelines on both sides of the standard flow meter 31, and a third pressure gauge 35 is installed on the pipeline on the side of the flow meter to be calibrated 32 away from the standard flow meter 31. The first pressure gauge 33, the second pressure gauge 34 and the third pressure gauge 35 all use high-precision pressure sensors to collect the pressure values ​​of each measuring point in real time and transmit the measured pressure values ​​to the controller.

[0040] like Figure 5-6 The flow meter calibration system shown has a water distribution and pressure stabilization function. The flow meter 32 to be calibrated is installed on a separable pipe assembly 4. The separable pipe assembly 4 includes a fixed base plate 41 arranged along the pipe extension direction. At least two fixed seats 42 are installed on the fixed base plate 41 near the standard flow meter 31. A fixed pipe 43 containing the standard flow meter 31 is fixed on the fixed seat 42, and a second pressure gauge 34 is installed on the fixed pipe 43. A sliding plate 44 and a reciprocating drive mechanism 45 are provided on the fixed base plate 41 away from the standard flow meter 31. The sliding plate 44 is slidably connected to the fixed base plate 41 through a slide rail mechanism. The drive part of the reciprocating drive mechanism 45 is drivenly connected to the sliding plate 44. A movable pipe 46 is fixed on the surface of the sliding plate 44. The reciprocating drive mechanism 45 drives the sliding plate 44 to reciprocate, causing the fixed pipe 43 and the movable pipe 46 to move closer to or separate from each other. The inlet and outlet of the flow meter 32 to be calibrated are connected to the fixed pipe 43 and the movable pipe 46, respectively.

[0041] like Figure 7The flow meter calibration system with water distribution and pressure stabilization function shown includes a reciprocating drive mechanism 45 comprising a base 451 fixed to the end of a fixed base plate 41. A drive rod 452 is slidably connected to the base 451 via a sliding sleeve. The drive rod 452 extends towards and connects to a slide plate 44. A hinge seat 453 is provided on the side of the base 451 away from the slide plate 44. The hinge seat 453 is hinged to the sliding sleeve, and a handle 454 is hinged to the hinge seat 453. The handle 454 is hinged to the end of the drive rod 452. The handle 454 includes a hinge portion hinged to the drive rod 452 and a force-applying portion, the hinge portion and the force-applying portion being integrally arranged at an angle.

[0042] When installing the flow meter 32 to be calibrated, the operator first connects the flow meter 32 to the opening of the fixed pipe 43 or the movable pipe 46. Then, press the force-applying part of the handle 454. The hinge part drives the drive rod 452 to move towards the slide plate 44, pushing the slide plate 44 to slide along the slide rail mechanism, so that the movable pipe 46 moves closer to the fixed pipe 43, aligning the opening of the movable pipe 46 or the fixed pipe 43 with the interface of the flow meter 32 to be calibrated. Rotate the locking ring with internal threads at the interface of the flow meter 32 to connect the flow meter 32 to be calibrated between the fixed pipe 43 and the movable pipe 46. When it is necessary to disassemble the flow meter 32 to be calibrated, loosen the locking ring to separate the flow meter 32 from the movable pipe 46 or the fixed pipe 43. Reverse the operation of the handle 454 to separate the movable pipe 46 from the fixed pipe 43, and disassemble the flow meter 32 to be calibrated.

[0043] In this embodiment, each water distribution chamber 212 corresponds to a flow meter calibration module 3. The proportional valve 5 of each flow meter calibration module 3 is configured to switch sequentially at a preset time interval (100ms) to avoid the superposition of disturbances from multiple channels. The water distribution chambers 212 are isolated from each other by partitions. Pressure disturbances in any branch are attenuated within the water distribution chamber 212 of that branch, reducing interference to the water distribution chambers of other branches and achieving fluid dynamic decoupling between the branches.

[0044] In this embodiment, the flow meter calibration module 3 is provided with at least three sets, and the pipe diameters of the at least three sets of flow meter calibration modules 3 are arranged in ascending order (e.g., corresponding to D15, D20, and D40 diameters), and the inlets of the three sets of flow meter calibration modules 3 are respectively connected to the outlets of the water distribution chamber 212. By setting multiple sets of flow meter calibration modules with different pipe diameters, the calibration requirements of flow meters of different diameters can be met simultaneously, thus expanding the applicability of the system.

[0045] In this embodiment, the flow meter calibration module 3 is equipped with an air purging device on its pipeline to remove residual air from the pipeline. The air purging device effectively eliminates the influence of residual air bubbles in the pipeline on the accuracy of flow measurement, ensuring the accuracy of the calibration results.

[0046] A flow meter calibration method, applied to the aforementioned flow meter calibration system, is characterized by comprising the following steps: S1: Start the dual-pump liquid supply module 1. The main pump outputs a pulse-free basic flow rate, while the auxiliary pump performs fine-tuning with a small displacement. The fluid enters the buffer and pressure-stabilizing chamber 211 of the water distribution and pressure-stabilizing module 2. High-frequency pulsations are absorbed by the diaphragm damper 23, and low-frequency fluctuations are absorbed by the pressure-stabilizing buffer tank 22. The stabilized fluid enters the flow meter calibration module 3 through the water distribution chamber 212 and is adjusted to the target flow rate through the proportional valve 5.

[0047] S2: Based on the feedback signal from the pressure sensor directly inserted into the wall of the buffer pressure regulating chamber 211, an incremental PID algorithm is used to adjust the speed of the liquid supply pump 12 with a control cycle of 10ms, forming a pressure closed loop so that the pressure of the buffer pressure regulating chamber 211 tracks the set value. The PID parameters are tuned using the Ziegler-Nichols method. Taking the operating condition of 0.5MPa and 20m³ / h as an example, the typical parameters are: Kp=2.5, Ki=0.8, Kd=0.3. The pressure overshoot is ≤2%, and the settling time (from step disturbance to re-entering the ±0.1% steady-state band) is ≤0.8s.

[0048] S3: When the opening command of proportional valve 5 changes, a compensation speed signal is output to the liquid supply pump 12 10 to 50 ms before the actual action of proportional valve 5, so that the pump flow output can be synchronously canceled with the expected valve flow change, thus realizing flow feedforward compensation.

[0049] S4: Simultaneously, the pressure sensor collects the pressure signal, and the standard flow meter 31 collects the flow signal. When the pressure is stable but the flow rate deviates from the set value, the auxiliary pump makes a fine adjustment; when the flow rate is stable but the pressure deviates from the set value, the main pump adjusts.

[0050] S5: During multi-channel parallel calibration, the proportional valves 5 corresponding to each water distribution chamber 212 are switched sequentially in a step manner at 100ms intervals to avoid the superposition of multiple disturbances.

[0051] S6: Temperature sensors are installed in the water distribution and pressure stabilizing module 2 and the liquid storage tank 11 respectively to measure the medium temperature, and temperature drift compensation is performed on the reading of the flow meter 32 to be calibrated according to the density correction formula.

[0052] The density correction formula is: In the formula, For the medium at the measured temperature The actual density below, The density of the medium at a reference temperature of 20°C. The coefficient of volumetric expansion of the medium is given in °C. -1 ; The temperature of the medium is measured by the temperature sensor, in °C; the constant 20 is a reference temperature. For water, the temperature is around 20°C. Approximately 2.07 × 10 -4 ℃-1 .

[0053] It should be noted that the standard flow meter 31 is a Coriolis mass flow meter, outputting mass flow rate, which is independent of the medium density; the flow meter 32 to be calibrated is a piezoelectric ceramic vortex water flow sensor, outputting volumetric flow rate, which is related to the medium density. When the medium temperature deviates from the reference temperature by 20°C, the medium density changes accordingly. If the conversion is still based on the reference density, calibration errors will occur. Therefore, the actual temperature of the medium is first measured by the temperature sensor, the actual density is calculated according to the density correction formula, and then the volumetric flow rate of the flow meter to be calibrated is converted to mass flow rate using this actual density (not the reference density), thereby eliminating the influence of density changes caused by temperature drift on the flow reading.

[0054] S7: Read the pressure values ​​of the first pressure gauge 33, the second pressure gauge 34, and the third pressure gauge 35 respectively. Correct the flow reading of the standard flow meter 31 according to the following formula: In the formula, The original flow reading of standard flow meter 31. The corrected standard flow rate value. The pressure value measured by the first pressure gauge 33. The pressure value is measured by the second pressure gauge 34.

[0055] Correct the flow rate at position 32 of the flow meter to be calibrated using the following formula: In the formula, This is the corrected flow rate value at position 32 of the flow meter to be calibrated. The pressure value measured by the second pressure gauge. This is the pressure value measured by the third pressure gauge 35.

[0056] According to Bernoulli's equation and the continuity equation, the flow rate through a pipeline is proportional to the square root of the pressure difference across the pipeline. When there is a pressure loss in the pipeline between the standard flow meter 31 and the flow meter 32 to be calibrated, the flow rate at the standard flow meter is not exactly equal to the flow rate at the flow meter to be calibrated, and correction is required based on the pressure ratio.

[0057] If the difference between the pressure value measured by the first pressure gauge 33 and the pressure value measured by the second pressure gauge 34 is less than a preset threshold (e.g., less than 0.5%FS), then the first pressure compensation is skipped. If the difference between the pressure value measured by the second pressure gauge 34 and the pressure value measured by the third pressure gauge 35 is less than a preset threshold, then the second pressure compensation is skipped.

[0058] S8: Compare the flow rate value of the flow meter 32 to be calibrated after temperature drift compensation and pressure compensation with the output flow rate value of the flow meter 32 to be calibrated, calculate the indication error, and complete the calibration.

[0059] The above embodiments are exemplary and are intended to illustrate the technical concept and features of the present invention, so that those skilled in the art can understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A flow meter calibration system with water separation and pressure stabilization function, characterized in that: Includes a dual-pump liquid supply module (1) for providing the base flow rate; The water distribution and pressure stabilization module (2) is used to distribute and stabilize the fluid supplied by the dual-pump liquid supply module (1); The flow meter calibration module (3) is used to calibrate the flow meter to be calibrated. The dual-pump liquid supply module (1) includes a liquid storage tank (11) and two liquid supply pumps (12) connected in parallel to the liquid inlet of the liquid storage tank (11). The two liquid supply pumps (12) include a main pump and an auxiliary pump. The main pump is used to output a pulse-free basic flow rate, and the auxiliary pump is used to make small-displacement fine adjustments on the basic flow rate. The flow meter calibration module (3) is equipped with a proportional valve (5) on the end pipeline. The proportional valve (5) is used to adjust the flow rate through the flow meter calibration module (3). It also includes a controller, which is connected to the liquid supply pump (12) and the proportional valve (5) respectively. The controller is used to adjust the speed of the liquid supply pump (12) according to the pressure feedback signal of the water distribution and pressure stabilizing module (2) to stabilize the system pressure.

2. The flow meter calibration system with water separation and pressure stabilization function according to claim 1, characterized in that: The water distribution and pressure stabilizing module (2) includes a tank (21), a pressure stabilizing buffer tank (22), and a diaphragm damper (23). The tank (21) is provided with a buffer pressure stabilizing chamber (211) and several water distribution chambers (212); the inlet of the buffer pressure stabilizing chamber (211) is connected to two liquid supply pumps (12) respectively, and the outlet of the water distribution chamber (212) is connected to the flow meter calibration module (3); the tank (21) is provided with a diaphragm damper (23), which is connected to the buffer pressure stabilizing chamber (211) and is used to absorb the high-frequency flow pulsation generated by the liquid supply pump (12); the pressure stabilizing buffer tank (22) is connected to the buffer pressure stabilizing chamber (211) and is used to absorb low-frequency pressure fluctuations; the cutoff frequency of the diaphragm damper (23) is higher than the cutoff frequency of the pressure stabilizing buffer tank (22), and the two form a full-band complementary suppression of high-frequency pulsation and low-frequency fluctuation; a pressure sensor connected to the controller signal is directly inserted into the cavity wall of the buffer pressure stabilizing chamber (211) and is used to collect the pressure signal of the buffer pressure stabilizing chamber (211) and send the signal to the controller.

3. The flow meter calibration system with water separation and pressure stabilization function according to claim 2, characterized in that: The flow meter calibration module (3) includes a standard flow meter (31) and a flow meter to be calibrated (32) arranged sequentially along the pipeline. The flow meter to be calibrated (32) is connected to a proportional valve (5) through a pipeline. The proportional valve (5) is connected to a storage tank (11) through a return pipe, which is used to return the fluid to the storage tank (11).

4. The flow meter calibration system with water separation and pressure stabilization function according to claim 3, characterized in that: A first pressure gauge (33) and a second pressure gauge (34) are installed on the pipelines on both sides of the standard flow meter (31), and a third pressure gauge (35) is installed on the pipeline on the side of the flow meter to be calibrated (32) away from the standard flow meter (31).

5. The flow meter calibration system with water separation and pressure stabilization function according to claim 4, characterized in that: The flow meter to be calibrated (32) is installed on the separable pipe assembly (4); the separable pipe assembly (4) includes a fixed base plate (41) arranged along the pipe extension direction; at least two fixed seats (42) are installed on the fixed base plate (41) near the standard flow meter (31), and a fixed pipe (43) on which the standard flow meter (31) is fixed is fixed on the fixed seat (42), and the second pressure gauge (34) is installed on the fixed pipe (43); a sliding plate is provided on the fixed base plate (41) away from the standard flow meter (31). (44) and reciprocating drive mechanism (45), the slide plate (44) is slidably connected to the fixed base plate (41) through the slide rail mechanism, the drive part of the reciprocating drive mechanism (45) is driven connected to the slide plate (44), and the surface of the slide plate (44) is fixed with a movable tube (46); the reciprocating drive mechanism (45) drives the slide plate (44) to reciprocate, so that the fixed tube (43) and the movable tube (46) approach or separate from each other; the inlet and outlet of the flow meter (32) to be calibrated are respectively connected to the fixed tube (43) and the movable tube (46).

6. The flow meter calibration system with water separation and pressure stabilization function according to claim 5, characterized in that: The reciprocating drive mechanism (45) includes a base (451) fixed to the end of a fixed base plate (41); the base (451) is slidably connected to a drive rod (452) via a sliding sleeve; the drive rod (452) extends toward the slide plate (44) and is connected to the slide plate (44); the base (451) is provided with a hinge seat (453) on the side away from the slide plate (44), the hinge seat (453) is hinged to the sliding sleeve, and a handle (454) is hinged on the hinge seat (453), the handle (454) is hinged to the end of the drive rod (452); the handle (454) includes a hinge part that is hinged to the drive rod (452) and a force-applying part, the hinge part and the force-applying part being integrally arranged at an angle.

7. The flow meter calibration system with water separation and pressure stabilization function according to claim 2, characterized in that: Each water distribution chamber (212) corresponds to a flow meter calibration module (3). The proportional valve (5) of each flow meter calibration module (3) is configured to switch sequentially at a preset time interval to avoid the superposition of multiple disturbances.

8. The flow meter calibration system with water separation and pressure stabilization function according to claim 2, characterized in that: The flow meter calibration module (3) is provided with at least three sets, and the pipe diameters of the at least three sets of flow meter calibration modules (3) are arranged in ascending order, and the inlets of the three sets of flow meter calibration modules (3) are respectively connected to the outlet of the water distribution chamber (212).

9. The flow meter calibration system with water separation and pressure stabilization function according to claim 1, characterized in that: The flow meter calibration module (3) is equipped with an air venting device on its pipeline to remove residual air from the pipeline.

10. A flow meter calibration method, applied to the flow meter calibration system according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Start the dual-pump liquid supply module (1), the main pump outputs a pulse-free basic flow rate, and the auxiliary pump performs fine adjustment with a small displacement; the fluid enters the buffer pressure stabilizing chamber (211) of the water distribution and pressure stabilizing module (2), the high-frequency pulsation is absorbed by the diaphragm damper (23), the low-frequency fluctuation is absorbed by the pressure stabilizing buffer tank (22), and the pressure-stabilized fluid enters the flow meter calibration module (3) through the water distribution chamber (212), and is adjusted to the target flow rate through the proportional valve (5); S2: Based on the feedback signal of the pressure sensor directly inserted into the wall of the buffer pressure stabilizing chamber (211), the incremental PID algorithm is used to adjust the speed of the liquid supply pump (12) with a control cycle of 10ms to form a pressure closed loop, so that the pressure of the buffer pressure stabilizing chamber (211) tracks the set value. S3: When the opening command of the proportional valve (5) changes, a compensation speed signal is output to the liquid supply pump (12) 10 to 50 ms before the actual action of the proportional valve (5), so that the pump flow output is synchronously offset with the expected valve flow change, and the flow feedforward compensation is realized. S4: At the same time, the pressure sensor collects the pressure signal and the standard flow meter (31) collects the flow signal; when the pressure is stable but the flow rate deviates from the set value, the auxiliary pump makes a fine adjustment; when the flow rate is stable but the pressure deviates from the set value, the main pump adjusts. S5: During multi-channel parallel calibration, the proportional valves (5) corresponding to each water distribution chamber (212) are switched sequentially in a step manner at 100ms intervals to avoid the superposition of multi-channel disturbances; S6: Temperature sensors are installed in the water distribution and pressure stabilization module (2) and the liquid storage tank (11) respectively to measure the medium temperature, and temperature drift compensation is performed on the reading of the flow meter (32) to be calibrated according to the density correction formula. The density correction formula is: In the formula, For the medium at the measured temperature The actual density below, The density of the medium at a reference temperature of 20°C. is the coefficient of volume expansion of the medium. The temperature is the actual temperature of the medium measured by the temperature sensor, and constant 20 is the reference temperature. S7: Read the pressure values ​​of the first pressure gauge (33), the second pressure gauge (34), and the third pressure gauge (35) respectively; correct the flow reading of the standard flow meter (31) based on the pressure value measured by the first pressure gauge (33) and the pressure value measured by the second pressure gauge (34): The flow rate at the position of the flow meter to be calibrated (32) is corrected based on the pressure values ​​measured by the second pressure gauge (34) and the third pressure gauge (35): If the difference between the pressure value measured by the first pressure gauge (33) and the pressure value measured by the second pressure gauge (34) is less than a preset threshold, the first pressure compensation is skipped; if the difference between the pressure value measured by the second pressure gauge (34) and the pressure value measured by the third pressure gauge (35) is less than a preset threshold, the second pressure compensation is skipped. S8: Compare the flow value of the flow meter to be calibrated (32) after temperature drift compensation and pressure compensation with the output flow value of the flow meter to be calibrated (32), calculate the indication error, and complete the calibration.

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