Method and device for correcting standard volume of piston type volume tube

Abstract

The invention provides a standard volume correction method and device for a piston type volume tube. The outer wall distributed temperature array is adopted to replace a traditional intrusive probe, the spatial resolution is improved, the complex temperature gradient existing in the axial direction of the volume tube can be more accurately captured, and particularly the defect that under the condition that the physical property of a medium is not uniform or environment heat exchange is not uniform, the temperature gradient of the volume tube is not uniform is overcome. And single-point temperature measurement cannot truly reflect the equivalent average temperature of the fluid. Meanwhile, the fluid temperature of the partition is inversed through the pipe wall temperature array, the heat conduction error in a traditional intrusive temperature measurement method is eliminated, and the temperature measurement deviation is remarkably reduced. And finally, the modular design of the sensor supports single-point replacement, so that the maintenance cost is reduced, the layout of the sensor can be conveniently adjusted according to actual requirements, and the temperature monitoring effect is further optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of instruments and meters, and particularly relates to a method and device for correcting the standard volume of a piston-type volume tube. Background Art

[0002] In the traditional temperature measurement method of piston-type volume tube flow standard devices, an invasive temperature sensor is usually used to monitor the temperature of the fluid in the tube. However, this method has significant disadvantages:

[0003] (1) The physical structure of the invasive probe will disturb the fluid flow field and destroy the original laminar or turbulent state. Especially under flow change or high flow rate conditions, the additional error introduced by the flow field distortion is large, which directly affects the basic accuracy of the flow meter calibration.

[0004] (2) Limited by the number of sensors and the installation position, its spatial resolution is seriously insufficient, making it difficult to capture the complex temperature gradient along the axial direction of the volume tube. Especially when the physical properties of the medium are uneven or the environmental heat exchange is uneven, single-point temperature measurement cannot truly reflect the equivalent average temperature of the fluid.

[0005] (3) The above-mentioned flow field interference and inaccurate temperature field representation together lead to systematic deviations in the input parameters of the thermal expansion correction model, which significantly reduces the accuracy of volume correction based on JJG 209-2010 or ISO 7278-2 standards.

[0006] (4) Intrusive installation requires drilling holes in the pipe wall and configuring a dynamic sealing structure, which not only increases the risk of fluid leakage, but also makes the probe easily contaminated by high-viscosity media or mechanically damaged, significantly increasing the frequency of periodic disassembly and maintenance of the equipment and the cost of probe replacement, seriously restricting the long-term operating economy and reliability of the device.

[0007] (5) When there are two different fluids separated by a piston rod in the tube, traditional invasive temperature measurement cannot perform volume corrections for different medium areas based on temperature differences due to single-point sampling and flow field interference, resulting in inaccurate calculation of the standard volume value under mixed medium working conditions, making it difficult to meet the complex medium calibration requirements. Summary of the Invention

[0008] To solve the above problems, the purpose of the present invention is to realize the equivalent temperature inversion of the fluid partition in the tube through real-time temperature monitoring, thereby realizing the standard volume correction function of the volume tube.

[0009] Based on the above objectives, the present invention provides a method and device for correcting the standard volume of a piston-type volume tube.

[0010] The first aspect of the present invention provides a method for correcting the standard volume of a piston-type volume tube. This method measures the outer wall temperature, inlet and outlet temperatures, and piston inlet and outlet pressures in real time, and further inverts the fluid partition temperature based on the outer wall temperature to correct the standard volume value during the test. The method comprises the following steps:

[0011] S1: Obtain the indicated value of the standard measuring instrument during the piston-type volume tube calibration experiment, that is, the standard volume value of the piston-type volume tube;

[0012] S2: obtaining the temperature and pressure of the fluid in the partition of the tube during the volume tube measurement process according to the temperature measuring unit, the pressure measuring unit and the temperature sensor array;

[0013] S3: obtaining the average temperature of the inverted fluid in each partition according to the temperature of the partitioned fluid in the pipe, and calculating a first correction factor;

[0014] S4: Calculate the correction of the standard volume value of the volume tube according to the standard volume value, the temperature and pressure of the partitioned fluid in the tube, and the first correction factor.

[0015] A second aspect of the present invention provides a piston-type volume tube standard volume correction device, comprising:

[0016] The indication value acquisition module is used to obtain the indication value of the standard measuring instrument during the piston-type volume tube calibration experiment.

[0017] The temperature and pressure acquisition module is used to inversely calculate the temperature of the fluid in the pipe partition based on the temperature sensors, pressure sensors and outer pipe wall temperature sensor arrays upstream and downstream of the piston-type volume pipe, and simultaneously obtain the pressure inside the volume pipe.

[0018] The first correction factor calculation module is used to calculate the first correction factor according to the temperature of the partitioned fluid in the piston-type volume tube.

[0019] The correction module is used to calculate the correction of the standard volume value of the volume tube according to the standard volume value, the temperature and pressure of the fluid in the partition of the tube, and the first correction factor.

[0020] Based on the above technical content, the present invention produces the following beneficial effects:

[0021] (1) The use of an outer wall distributed temperature array instead of the traditional invasive probe not only improves the spatial resolution, but also can more accurately capture the complex temperature gradient along the axial direction of the volume tube. In particular, it improves the problem that single-point temperature measurement cannot truly reflect the equivalent average temperature of the fluid when the physical properties of the medium are uneven or the environmental heat exchange is uneven.

[0022] (2) The partitioned fluid temperature is inverted by the pipe wall temperature array, eliminating the thermal conductivity error in the traditional invasive temperature measurement method, and significantly reducing the temperature measurement deviation.

[0023] (3) The non-invasive design avoids the risk of seal failure and reduces maintenance frequency. At the same time, when the piston center axis temperature or the tube wall temperature field fluctuates abnormally, a dynamic seal failure alarm can be triggered in real time, increasing the safety of the system.

[0024] (4) The modular design of the sensor supports single-point replacement, which not only reduces maintenance costs but also facilitates adjustment of the sensor layout according to actual needs, further optimizing the monitoring effect.

[0025] (5) For the different fluid areas divided by the piston rod, the temperature of the two fluids can be measured separately by the temperature difference, and their respective corrections to the standard volume value of the volume tube can be calculated accordingly, thus realizing accurate volume correction in cases containing different fluid media. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a working principle diagram of the piston-type volume tube test in an embodiment of the present application;

[0027] Figure 2 This is a flow chart of a method for correcting the standard volume of a piston-type volume tube according to an embodiment of the present application.

[0028] Figure markings: 1. Pressure sensor at the inlet; 2. Temperature sensor at the inlet; 3. Piston-type volume tube cylinder; 4. Temperature sensor array; 5. Piston; 6. Flow meter under test; 7. Pressure sensor at the outlet; 8. Temperature sensor at the outlet; 9. Control system; 10. Photoelectric switch for ending detection; 11. Measuring rod; 12. Photoelectric switch for starting detection. DETAILED DESCRIPTION

[0029] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0030] The measurement principle of the piston-type volume tube flow standard device is based on the volume displacement principle. Figure 1 The figure shows the working principle of the piston-type volume tube test provided by the embodiment of the present application. The arrow in the figure indicates the direction of the given flow rate. Before the test, a certain flow rate is injected into the inlet of the piston-type volume tube. The piston 5 in the piston-type volume tube cylinder 3 moves from the start detection photoelectric switch 12 on the measuring rod 11 to the end detection photoelectric switch 10. The volume of fluid displaced by the piston 5 during this process represents the standard volume during the test. , the detection time is , thus obtaining the cumulative flow The accumulated flow is used to calibrate the flow meter 6 under test, and the formula is:

[0031]

[0032] Since the wall of the volume tube is in direct contact with the fluid, its temperature distribution is directly affected by the fluid state, while traditional invasive temperature measurement will interfere with the flow field and make it difficult to capture the axial temperature gradient. In the embodiment of the present application, an array of temperature sensors 4 is laid at intervals on the outer wall of the volume tube to obtain the temperature field distribution of the entire tube wall in real time. Since the outer wall temperature field accurately reflects the thermodynamic state inside the tube, a complete fluid thermodynamic parameter system is constructed by combining the data measured by the pressure measuring unit and the temperature measuring unit. The equivalent temperature of the fluid is calculated by partitioning and inverting the thermal resistance model, and the thermal expansion compensation amount is directly generated without the need to indirectly infer the piston rod temperature. The pressure measuring unit includes an inlet pressure sensor 1 and an outlet pressure sensor 7, and the temperature measuring unit includes an inlet temperature sensor 2 and an outlet temperature sensor 8.

[0033] When the piston-type volume tube starts testing, the system records the outer wall temperature field distribution 5 times between the two key time points during the movement of the piston 5 from the start of the detection of the photoelectric switch 12 to the end of the detection of the photoelectric switch 10. The temperature field data of the 5 times between the two time points are input into the thermodynamic inversion model: the equivalent temperature of the partitioned fluid is calculated, the thermal expansion compensation is generated, and the pressure average of the inlet pressure sensor 2 and the outlet pressure sensor 8 is synchronously integrated. Finally, the dynamic compensation of the standard volume value is completed through the correction formula. This calculation process is executed in real time by the control system 9.

[0034] Based on the above working principle, Figure 2 As shown, the embodiment of the present application provides a method for correcting the standard volume of a piston-type volume tube. First, the standard measuring instrument indication value during the piston-type volume tube calibration experiment is obtained, that is, the standard volume value of the piston-type volume tube. Then, based on the correction formula for the standard volume value of the volume tube in the national verification regulations for volume tubes, an improved method for calculating the correction value of the standard volume value of the volume tube is provided by using the temperature and pressure of the fluid in the partition within the tube and a first correction factor. Specifically, the following steps are included:

[0035] S1: Obtain the indicated value of the standard measuring instrument during the piston-type volumetric tube calibration experiment, that is, the standard volume value of the piston-type volumetric tube.

[0036] S2: Based on the temperature sensors and pressure sensors upstream and downstream of the piston-type volume tube and the outer tube wall temperature sensor array, the temperature and pressure of the partitioned fluid in the tube during the volume tube measurement process are obtained.

[0037] S3: Obtain the average temperature of the inverted fluid in each partition based on the tube wall temperature array during the piston-type volume tube test and the temperatures upstream and downstream of the volume tube, and calculate the first correction factor.

[0038] S4: Calculate the correction of the standard volume value of the volume tube according to the standard volume value, the temperature and pressure of the partitioned fluid in the tube, and the first correction factor.

[0039] Furthermore, the temperature sensor array is laid at intervals on the outer wall of the piston-type volume tube to obtain the temperature field distribution of the entire tube wall in real time.

[0040] Furthermore, the pressure measuring unit is respectively arranged at the upstream and downstream of the piston-type volume tube; the temperature measuring unit is respectively arranged at the upstream and downstream of the piston-type volume tube.

[0041] Furthermore, the S2 is specifically:

[0042] According to the pressure measuring units upstream and downstream of the piston-type volume tube, the pressure inside the volume tube is obtained;

[0043] According to the temperature sensor array laid at intervals along the axial direction on the outer surface of the volume tube, the temperature change of the tube wall zone is obtained;

[0044] According to the temperature measuring units upstream and downstream of the piston-type volume tube, the temperatures upstream and downstream of the volume tube are obtained.

[0045] In particular, the temperature distribution of the fluid in the volume tube given in the embodiment of the present application is based on temperature sensors installed on the outer surface of the volume tube and upstream and downstream of the volume tube, so as to obtain real-time monitoring of the temperature of the partitioned fluid in the volume tube. There is no need to change the original mechanical structure of the volume tube, and the implementation method is simple and efficient.

[0046] Furthermore, in S4, the correction of the standard volume value of the volume tube is obtained by the following calculation method:

[0047]

[0048] Where: is the volume value of the volume tube under standard conditions, L; is the indicated value of the standard measuring instrument, L; is the volume expansion coefficient of the standard measuring instrument material, 1 / ℃; is the volume expansion coefficient of the equivalent fluid, 1 / °C; is the wall temperature of the standard measuring instrument, °C; is the overall water temperature of the volume tube, °C; is the linear expansion coefficient of the volume tube material, 1 / °C; To measure the linear expansion coefficient of the rod, 1 / °C; is the piston rod temperature, °C; is the gauge pressure of the fluid in the volume tube, Pa; is the inner diameter of the standard volume section of the volume tube, m; E is the elastic modulus of the volume tube material, Pa; t is the wall thickness of the standard volume section of the volume tube, m; is the compressibility of water, 1 / Pa; is the first correction factor.

[0049] Furthermore, the volume expansion coefficient of the equivalent fluid is Represents a comprehensive, volume-weighted average coefficient of expansion for overall thermal expansion correction when the piston rod separates different fluid media. It is calculated as follows:

[0050] The volume expansion coefficient of each partition fluid is weighted averaged according to its volume proportion:

[0051]

[0052] and They represent the volume of the tube occupied by different fluids, and Represent the volume expansion coefficients of different fluids respectively.

[0053] Furthermore, the overall water temperature of the volume tube Obtained by the following method:

[0054] Data acquisition of pipe wall temperature sensor array: ,in is the reading of the upstream temperature sensor, ℃; is the reading of the downstream temperature sensor, ℃; is the temperature of point i, ℃.

[0055] Partition the temperature field: randomly select two points ,when ( When is the temperature threshold, it means that the fluids in the pipe represented by the two points are different and need to be calculated separately. Measure each sensor point in each partition and obtain the fluid temperature inversion at each point:

[0056]

[0057] in, is the pipe wall thickness, mm; is the thermal conductivity of the partition medium, W / (m×k).

[0058] The fluid temperature of each point is inverted and averaged to obtain the inverted fluid average temperature of partition m :

[0059] =

[0060] The overall water temperature is obtained by weighted averaging the average temperature of the inverted fluid in each partition according to its volume proportion. :

[0061]

[0062] Furthermore, the piston center rod temperature t r Obtained by the following method:

[0063] Determine the piston rod position:

[0064]

[0065] in, Piston position (obtained in real time by photoelectric switch); is the fixed distance from the piston to the center of the measuring rod.

[0066] Interpolation to obtain the rod position fluid temperature:

[0067]

[0068] Use the cubic spline interpolation algorithm to obtain the piston center rod temperature t r :

[0069]

[0070] in, is the radius of the measuring rod, m; is the thermal conductivity of the rod material, W / (m×k); is the thermal conductivity of the fluid, W / (m×k); is the thermal diffusivity, .

[0071] In conjunction with the first aspect, in one possible design, the first correction factor is calculated as follows:

[0072] The axial temperature distribution of the entire tube wall is obtained through the temperature sensor array laid on the outer wall of the volume tube;

[0073] Obtain the fluid temperature at the inlet and outlet of the volume tube through the temperature measuring unit;

[0074] Get the volume expansion coefficient of the tube;

[0075] A first correction factor is calculated according to the axial temperature distribution of the tube wall, the fluid temperature at the inlet and outlet of the volume tube, and the expansion coefficient of the volume tube.

[0076] Furthermore, the first correction factor for calculating the fluid temperature during the piston-type volume tube test is obtained by the following calculation method:

[0077]

[0078] in, is the geometric volume of partition m, is the volume expansion coefficient of the fluid in partition m, 1 / °C.

[0079] Based on the same concept as the above method, the embodiment of the present application also provides a piston-type volume tube standard volume correction device, comprising:

[0080] The indication value acquisition module is used to obtain the indication value of the standard measuring instrument during the piston-type volume tube calibration experiment;

[0081] The temperature and pressure acquisition module is used to perform partition inversion of the fluid temperature in the volume tube based on the temperature sensors and pressure sensors upstream and downstream of the piston-type volume tube and the tube wall temperature array, and obtain the partition temperature and pressure of the fluid in the volume tube;

[0082] A first correction factor calculation module is used to calculate the first correction factor based on the upstream and downstream temperature data and the outer wall temperature inversion fluid partition temperature;

[0083] The correction module is used to calculate the correction of the standard volume value of the volume tube according to the standard volume value, the temperature and pressure of the partition in the tube, and the first correction factor.

[0084] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for correcting the standard volume of a piston-type volume tube, characterized in that: The steps include: S1: Obtain the indicated value of the standard measuring instrument during the piston-type volume tube calibration experiment, that is, the standard volume value of the piston-type volume tube; S2: obtaining the temperature and pressure of the fluid in the partition of the tube during the volume tube measurement process according to the temperature measuring unit, the pressure measuring unit and the temperature sensor array; S3: obtaining the average temperature of the inverted fluid in each partition according to the temperature of the partitioned fluid in the pipe, and calculating a first correction factor; S4: Calculate the correction of the standard volume value of the volume tube according to the standard volume value, the temperature and pressure of the partitioned fluid in the tube, and the first correction factor.

2. The method according to claim 1, characterized in that The temperature sensor array is laid at intervals on the outer wall of the piston-type volume tube to obtain the temperature field distribution of the entire tube wall in real time.

3. The method according to claim 1, characterized in that The pressure measuring units are respectively arranged at the upstream and downstream of the piston-type volume tube; the temperature measuring units are respectively arranged at the upstream and downstream of the piston-type volume tube.

4. The method according to claim 1, 2 or 3, characterized in that The step 2 is specifically as follows: According to the pressure measuring units upstream and downstream of the piston-type volume tube, the pressure inside the volume tube is obtained; According to the temperature sensor array laid at intervals along the axial direction on the outer surface of the volume tube, the temperature change of the tube wall zone is obtained; According to the temperature measuring units upstream and downstream of the piston-type volume tube, the temperatures upstream and downstream of the volume tube are obtained.

5. The method according to claim 1, wherein The calculation method of the average temperature of the inversion partition fluid is: Performing data acquisition on the temperature sensor array; Randomly sample the temperature of two points. When the temperature difference between the two points is greater than the set temperature threshold, it means that the fluids in the pipe represented by the two points are different, and the fluids in the pipe are partitioned. Measure each sensor point in each partition and obtain the fluid temperature inversion at each point; The fluid temperature of each point is inverted and averaged to obtain the average fluid temperature of the inverted partition.

6. The method according to claim 1, 2 or 3, characterized in that The calculation method of the first correction factor is: The axial temperature distribution of the entire pipe wall is obtained by the temperature sensor array; the temperature of the fluid inlet and outlet of the volume pipe is obtained by the temperature measuring unit; Get the volume expansion coefficient of the tube; A first correction factor is calculated according to the axial temperature distribution of the tube wall, the fluid temperature at the inlet and outlet of the volume tube, and the expansion coefficient of the volume tube.

7. The method according to claim 1, characterized in that In S4, the correction of the standard volume value of the volume tube is obtained by the following calculation method: ； Where: It is the volume value of the volume tube under standard conditions, the unit is L; It is the indication value of the standard measuring instrument, the unit is L; is the volume expansion coefficient of the standard measuring instrument material, the unit is 1 / ℃; is the volume expansion coefficient of the equivalent fluid, in 1 / °C; is the wall temperature of the standard measuring instrument, in °C; is the overall water temperature of the volume tube, in °C; is the linear expansion coefficient of the volume tube material, in 1 / °C; To measure the linear expansion coefficient of the rod, the unit is 1 / ℃; is the piston rod temperature, in °C; is the gauge pressure of the fluid in the volume tube, in Pa; is the inner diameter of the standard volume section of the volume tube, in m; E is the elastic modulus of the volume tube material, in Pa; t is the wall thickness of the standard volume section of the volume tube, in m; is the compressibility coefficient of water, unit is 1 / Pa; is the first correction factor.

8. The method according to claim 7, characterized in that The overall water temperature is obtained by weightedly averaging the average temperatures of the inverted fluids in each partition according to their volume proportions.

9. The method according to claim 7, characterized in that The piston center rod temperature is obtained by the following method: Determine the piston rod position; interpolate to obtain the rod position fluid temperature; use the cubic spline interpolation algorithm to obtain the piston center rod temperature.

10. A piston-type volume tube standard volume correction device, characterized in that: include: The indication value acquisition module is used to obtain the indication value of the standard measuring instrument during the piston-type volume tube calibration experiment; The temperature and pressure acquisition module is used to inversely calculate the temperature of the fluid in the pipe partition based on the temperature sensors, pressure sensors and outer wall temperature sensor arrays upstream and downstream of the piston-type volume tube, and simultaneously obtain the pressure inside the volume tube; A first correction factor calculation module, used to calculate the first correction factor according to the temperature of the partitioned fluid in the piston-type volume tube; The correction module is used to calculate the correction of the standard volume value of the volume tube according to the standard volume value, the temperature and pressure of the fluid in the partition of the tube, and the first correction factor.

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