A method of measuring the flow rate of a pipeline gas

Abstract

The application discloses a kind of pipeline gas flow rate measurement methods, comprising the following steps: S1, thermistor is installed in the preset pipeline where gas flow rate and temperature can be adjusted;S2, flow rate curve fitting: S3, the gas flow rate of the preset pipeline is kept at a constant reference value V0, change preset pipeline temperature t1, collect the voltage value u2 of the thermistor both ends under different pipeline temperature t1;S4, calculate the thermistor voltage error value S5, temperature curve fitting;S6, the thermistor is installed in the pipeline to be measured, the temperature t k Of the pipeline to be measured is measured, and the voltage value u k Of the thermistor both ends is measured;S7, calculate the thermistor voltage correction value u c =u k -Δy'; S8, the thermistor voltage correction value u c Substitute the flow rate curve, obtain the gas flow rate v c Of the pipeline to be measured.The application reduces the influence of environmental temperature change on pipeline gas flow rate, reduces the measurement error, greatly improves the accuracy of measuring gas flow rate.

Description

Technical Field

[0001] This invention relates to the technical field of flow velocity measurement, and more specifically, to a method for measuring the flow velocity of gas in a pipeline. Background Technology

[0002] In clinical practice, when delivering gases such as oxygen, it is necessary to measure the gas flow rate in the pipeline in real time and quickly to improve the accuracy of medical measures and thus maximize the effectiveness of medical treatment.

[0003] Traditional pipeline gas measurement devices, such as gas flow meters and ultrasonic gas velocity meters, each have their own limitations when measuring the flow rate of gas in pipelines. For example, the former requires an additional external pipeline for flow detection, while the latter has high requirements for the straightness and smoothness of the gas transmission pipeline. These defects lead to varying degrees of error in their measurement results.

[0004] In addition, there is a method for measuring the gas flow rate in a pipeline using a thermistor. The basic principle is that when gases with different flow rates pass through the thermistor, they will carry away different amounts of heat from the thermistor, causing the resistance of the thermistor to change. This causes a change in the voltage across the thermistor. When it is necessary to measure the gas flow rate, the gas flow rate can be deduced from the change in the thermistor voltage.

[0005] However, in actual use, the resistance of the thermistor is affected not only by the gas flow rate but also by the ambient temperature. In different temperature environments, the resistance of the thermistor is different at the same flow rate. This leads to a large error in the flow rate value measured by the above method as the ambient temperature changes.

[0006] Therefore, it is necessary to improve the existing technology for measuring gas flow velocity in pipelines. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for measuring gas flow velocity in pipelines, thereby improving the accuracy of gas flow velocity measurement in pipelines.

[0008] This invention discloses a method for measuring gas flow velocity in a pipeline, comprising the following steps: S1, installing a thermistor in a preset pipeline with adjustable gas flow velocity and temperature; S2, flow velocity curve fitting: maintaining the temperature of the preset pipeline at a constant reference value T0, changing the gas flow velocity v1 in the preset pipeline, collecting the voltage value u1 across the thermistor at different gas flow velocities v1, obtaining multiple sets of data scatter points about v1 and corresponding u1, fitting the scatter points of v1 and u1 to obtain a flow velocity curve relating the gas flow velocity v1 to the voltage u1 across the thermistor; S3, maintaining the gas flow velocity in the preset pipeline at a constant reference value V0, changing the temperature t1 in the preset pipeline, collecting the voltage value u2 across the thermistor at different pipeline temperatures t1; S4, calculating the corresponding thermistor voltage error value for each different pipeline temperature t1 in S3. in S5. Temperature curve fitting: Perform regression fitting on the scatter points of Δy and corresponding t1 to obtain the temperature curve relating the thermistor voltage error value Δy to the pipe temperature t1; S6. Install the thermistor inside the pipe to be tested and measure the temperature t of the pipe to be tested. k And measure the voltage value u across the thermistor. k S7. The temperature t of the pipe to be measured k Substituting the temperature curve, the thermistor voltage error value Δy′ is obtained, and the thermistor voltage correction value u is calculated. c =u k -Δy′;S8、The thermistor voltage correction value u c Substituting the velocity curve, the gas velocity v in the pipe under test is obtained. c .

[0009] Preferably, it also includes deviation calculation: deviation value Deviation correction: Set a deviation correction range, determine whether the deviation value x is within the deviation correction range, retain t1 and Δy of the deviation value x within the deviation correction range, and discard t1 and Δy of the deviation value x outside the deviation correction range.

[0010] Preferably, the method for determining the deviation correction range is as follows: perform regression analysis on t1-T0 and Δy to obtain the regression curve of t1-T0 with respect to Δy, calculate the distance between each data point (t1-T0, Δy) and the regression curve, and discard the data points that are farthest from the regression curve by a preset proportion.

[0011] Preferably, let t1 = t k u2=u kThe deviation calculation and correction are performed, using the measured pipe temperature t that conforms to the deviation correction. k The thermistor voltage correction value u is calculated based on the thermistor voltage error value Δy′. c Otherwise, remeasure the temperature t of the pipe to be tested. k and the voltage value u across the thermistor k .

[0012] Preferably, the collected voltage values ​​across the thermistor are filtered.

[0013] Preferably, the least squares method is used to perform regression fitting on the flow velocity curve and the temperature curve.

[0014] Preferably, the least squares method is used to fit the regression curve of t1-T0 with respect to Δy.

[0015] Preferably, a gas flow rate measurement system is used to measure the gas flow rate in the pipeline under test. The gas flow rate measurement system includes a thermistor and its control circuit, a temperature sensor, a voltage measuring device, a processor, and input / output devices.

[0016] Preferably, a gas flow rate measurement system is used to measure the gas flow rate in the pipeline under test. The gas flow rate measurement system includes a thermistor and its control circuit, a temperature sensor, a filter, a voltage measuring device, a processor, and input / output devices.

[0017] Preferably, the temperature sensor is used to measure the temperature of the preset pipe and the pipe to be tested, and the voltage measuring device is used to measure the voltage across the thermistor.

[0018] The beneficial effects of this application are as follows:

[0019] By maintaining a constant flow rate, the relationship between pipe temperature and the thermistor voltage error is found, allowing the influence of temperature on the thermistor voltage to be considered during flow rate measurement. This reduces the impact of pipe temperature changes caused by ambient temperature variations on pipe flow rate measurement, significantly reducing measurement errors and improving the accuracy of pipe gas flow rate measurement. Furthermore, through extensive sampling by the software and equipment in the gas flow rate measurement system, temperature and flow rate curves with different levels of accuracy can be fitted according to different precision requirements, greatly improving the accuracy of pipe gas flow rate measurement. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a flowchart of the pipeline gas flow velocity measurement method of the present invention;

[0022] Figure 2 This is a schematic diagram of the gas flow rate measurement system of the present invention;

[0023] Figure 3 A velocity curve showing the relationship between the gas flow rate in the pipeline and the voltage across the thermistor.

[0024] Figure 4 A temperature curve showing the relationship between the thermistor voltage error and the pipe temperature;

[0025] Figure 5 This is a schematic diagram of the gas flow rate measurement system when measuring the temperature of the pipe under test. Detailed Implementation

[0026] The following drawings disclose several embodiments of the present invention. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not essential. Furthermore, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0027] It should be noted that all directional indications in the embodiments of the present invention, such as up, down, left, right, front, back, etc., are only used to explain the relative positional relationship and movement of the components in a specific posture as shown in the attached figure. If the specific posture changes, the directional indication will also change accordingly.

[0028] Furthermore, in this invention, the use of terms such as "first," "second," etc., is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish items or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0029] To further understand the invention's content, features, and effects, the following embodiments are described in detail with reference to the accompanying drawings:

[0030] Reference Figure 1 and Figure 2 This invention discloses a method for measuring gas flow velocity in a pipeline. The method uses a gas flow velocity measurement system to measure the gas flow velocity within the pipeline. The gas flow velocity measurement system includes a thermistor and its control circuit, a temperature sensor, a filter, a voltage measuring device, a processor, and input / output devices. The thermistor and its control circuit, the temperature sensor, the filter, and the input / output devices are all connected to the processor. The voltage measuring device is connected to the thermistor and its control circuit, and the filter. Specifically, the temperature sensor measures the pipeline temperature, the voltage measuring device measures the voltage across the thermistor, and the filter performs filtering processing on the voltage data.

[0031] Reference Figure 1-5 The measurement method includes the following steps:

[0032] S1. Start the gas flow rate measurement system. Before measuring the gas flow rate in the pipeline to be measured, install a thermistor in a preset pipeline. The gas flow rate and temperature in the preset pipeline can be adjusted within a certain range.

[0033] S2. Flow velocity curve fitting: Using a typical pipe temperature value T0 as a benchmark (T0 = 25℃ in this embodiment), the gas temperature inside the preset pipe is kept constant at T0. The gas flow velocity v1 inside the preset pipe is continuously changed, and the voltage value u1 across the thermistor is collected under different gas flow velocities v1. The measured voltage value u1 is filtered by a filtering device to obtain multiple sets of data scatter points about v1 and the corresponding u1. The least squares method is used to fit the above scatter points to obtain the flow velocity curve showing the relationship between the gas flow velocity v1 and the voltage u1 across the thermistor. Figure 3 The v1-u1 curve in the figure: v1 = Au1 3 +Bu1 2 +Cu1 1 +D, where A, B, C, and D are the coefficients obtained after fitting;

[0034] S3. Taking a typical pipeline flow velocity V0 as a reference, in this embodiment, V0 = 10 L / min is taken. The gas flow velocity in the preset pipeline is kept constant at V0. The preset pipeline temperature t1 is continuously changed, and the voltage value u2 across the thermistor is collected at different pipeline temperatures t1.

[0035] S4. Deviation Calculation: For each different pipe temperature t1 in S3, calculate the corresponding thermistor voltage error value Δy, and the deviation value x of the degree of influence of pipe temperature on the thermistor voltage. Let u1 be the value of the voltage across the thermistor when v1 = V0 in the v1-u1 curve.

[0036] S5, Deviation Correction: Determine whether the deviation value x is within the deviation correction range. Take t1 and Δy that are within the deviation correction range and perform S6. Discard t1 and Δy that are outside the deviation correction range. Specifically, the deviation correction method is: use the least squares method to perform regression analysis on t1-T0 and Δy, fit the regression curve of t1-T0 with respect to Δy, calculate the distance between each data point (t1-T0, Δy) and the regression curve, and remove a specific proportion of data points that are farthest from the regression curve. Specifically, in this embodiment, 30% of the data points that are farthest from the regression curve are removed.

[0037] S6. Temperature Curve Fitting: The scatter plots of the data points from S4, which meet the deviation correction Δy and the corresponding t1, are fitted using the least squares method to obtain the temperature curve relating the thermistor voltage error value Δy to the pipe temperature t1. Figure 4 The Δy-t1 curve in the figure: Δy=at1 3 +bt1 2 +ct1 1 +d, where a, b, c, and d are the coefficients obtained after fitting;

[0038] S7. Install the thermistor inside the pipe to be tested, and use a temperature sensor to measure the temperature t of the pipe. k The voltage value u across the thermistor is measured using a voltage measuring device. k Simultaneously, the voltage value u across the thermistor was collected. k Perform filtering processing;

[0039] S8. Calculate the thermistor voltage correction value u. c The temperature t of the pipe under test measured in S7 k Substituting the temperature curve, we obtain the thermistor voltage error value Δy′, and let t1 = t k u2=u k Perform deviation calculation in S4 to determine the temperature t of the pipe under test. k If the thermistor voltage error value Δy′ conforms to the deviation correction in S5, then calculate the thermistor voltage correction value u. c =u k If -Δy′ does not meet the deviation correction, then repeat S7;

[0040] S9. Adjust the voltage correction value of the thermistor to the tolerance. c Substituting the velocity curve, we obtain the gas velocity v in the pipe under test. c .

[0041] Experimental Example

[0042] Reference Figure 3-5After determining the flow velocity and temperature curves, a gas flow velocity measurement system is used to measure the temperature (t) inside the pipe under test using a temperature sensor. k =34℃, the actual voltage sampled across the thermistor is u k =5V;

[0043] t k =34℃ Substitute Figure 4 The temperature curve yielded a thermistor voltage error value Δy′=2.4V. After verification and deviation correction, the thermistor voltage correction value u was determined. c =u k -Δy′=5-2.4=2.6V;

[0044] The thermistor voltage correction voltage value u c =2.6V Substitute Figure 3 The velocity curve is used to obtain the gas velocity v. c =10L / min.

[0045] The implementation principle and beneficial effects of this invention are as follows: When the heating power of the thermistor is constant, if no gas flows through, the surface temperature of the thermistor remains unchanged; when gas flows through the thermistor, it carries away heat, and the amount of heat carried away is related to the gas flow rate. Therefore, the temperature of the thermistor will decrease, thereby changing the resistance of the thermistor and causing a change in the voltage across the thermistor. By using temperature curves and flow rate curves to find the variation law of the voltage across the thermistor with temperature and the variation law of the voltage across the thermistor with the gas flow rate in the pipe, and then specifically measuring the temperature of the pipe to be tested and the voltage of the thermistor placed in it, the gas flow rate of the pipe to be tested can be obtained by calculating and analyzing using temperature curves and flow rate curves.

[0046] By maintaining a constant flow rate, the relationship between pipe temperature and the thermistor voltage error is found, allowing the influence of temperature on the thermistor voltage to be considered during flow rate measurement. This reduces the impact of pipe temperature changes caused by ambient temperature variations on pipe flow rate measurement, significantly reducing measurement errors and improving the accuracy of pipe gas flow rate measurement. Furthermore, through extensive sampling by the software and equipment in the gas flow rate measurement system, temperature and flow rate curves with different levels of accuracy can be fitted according to different precision requirements, greatly improving the accuracy of pipe gas flow rate measurement.

[0047] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method of measuring the flow rate of a pipeline gas, characterized in that, The method comprises the following steps: S1, installing a thermistor in a preset pipeline with adjustable gas flow rate and temperature; S2, Flow velocity curve fitting: Maintaining the temperature of the preset pipe at a constant reference value. Change the gas flow rate in the preset pipe Collect different gas flow rates The voltage value across the thermistor described below Multiple sets of information were obtained. Data scatter points, for the and The gas flow rate is obtained by fitting the data scatter points. The voltage across the thermistor The velocity curves relating the two; S3, maintaining the gas flow rate of the preset pipeline at a constant reference value , changing the temperature in the preset pipeline , collecting the voltage value across the thermistor at different pipeline temperatures , collecting the voltage value across the thermistor at different pipeline temperatures ; S4, for each different pipe temperature in S3 , calculate the corresponding thermistor voltage error value where is the value of the thermistor voltage when the flow rate curve ​​ S5, temperature curve fitting: the data scatter points of the thermistor voltage error value and the corresponding pipe temperature are fitted by regression to obtain a temperature curve of the relationship between the thermistor voltage error value and the pipe temperature S6, install the thermistor in the pipeline to be measured to measure the temperature of the pipeline to be measured , and measure the voltage value across the thermistor ; S7. The temperature of the pipe to be measured Substituting the temperature curve, the voltage error value of the thermistor is obtained. Calculate the voltage correction value of the thermistor. = - ; S8、correcting the thermistor voltage value substituting the flow rate curve, the gas flow rate of the pipeline to be measured is obtained .

2. The method of claim 1, wherein, Also included is a deviation calculation: a deviation value ; a deviation correction: setting a deviation correction range, determining whether the deviation value is within the deviation correction range, retaining the deviation value within the deviation correction range and , discarding the deviation value outside the deviation correction range and .

3. The method of claim 2, wherein, The method for determining the deviation correction range is: regression analysis is performed on and to obtain a regression curve about , the distance between each data point , and the regression curve is calculated, and a preset proportion of data points farthest from the regression curve are discarded.

4. A method of measuring the flow rate of a pipeline gas according to claim 2 or 3, characterised in that, Let = , the deviation calculation and the deviation correction are carried out, the pipeline temperature to be measured and the thermistor voltage error value corresponding to the deviation correction are adopted to calculate the thermistor voltage correction value , otherwise the pipeline temperature to be measured and the voltage value across the thermistor are re-measured .

5. The method of claim 1-3, wherein, Filtering the collected voltage of the thermistor.

6. The method of claim 1-3, wherein, Using the least square method to regress and fit the flow rate curve and the temperature curve.

7. The method of claim 3, wherein, The least square method is used to fit the regression curve of the Regarding the regression curve is fitted.

8. The method of claim 1-3, wherein, Measuring the gas flow rate of the pipeline to be measured by a gas flow rate measuring system, which comprises a thermistor and its control circuit, a temperature sensor, a voltage measuring device, a processor and an input and output device.

9. The method of claim 5, wherein, Measuring the gas flow rate of the pipeline to be measured by a gas flow rate measuring system, which comprises a thermistor and its control circuit, a temperature sensor, a filter device, a voltage measuring device, a processor and an input and output device.

10. The method of claim 9, wherein, Measuring the temperature of the preset pipeline and the pipeline to be measured by the temperature sensor, and measuring the voltage across the thermistor by the voltage measuring device.

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