阅读说明：本技术 一种非均匀流场气体流量测量方法及系统 (Non-uniform flow field gas flow measurement method and system ) 是由 石伟伟 韦红旗 于森 王丘 梁万库 张彭 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种非均匀流场气体流量测量方法及系统,非均匀流场气体流量测量方法,在测量截面上按网格法布置N根皮托管,获取N根皮托管测量的流速值,N根皮托管测量的流速值的平均值为测量截面的平均流速,平均流速与测量截面的截面积相乘,即得到该截面的气体流量,其中,N≥4。本发明非均匀流场气体流量测量方法,通过在测量截面上布置N根皮托管,获取N根皮托管测量的流速值的滚动平均值,实现非均匀流场气体流量的连续输出,显著提高了非均匀流场气体流量测量的准确性；进一步,将N根皮托管接同一个差压变送器,减少了现场标定试验的工作量,降低了成本。(The invention discloses a non-uniform flow field gas flow measuring method and a system, wherein N pitot tubes are arranged on a measuring section according to a grid method, flow velocity values measured by the N pitot tubes are obtained, the average value of the flow velocity values measured by the N pitot tubes is the average flow velocity of the measuring section, the average flow velocity is multiplied by the sectional area of the measuring section, and the gas flow of the section is obtained, wherein N is more than or equal to 4. According to the non-uniform flow field gas flow measuring method, the N pitot tubes are arranged on the measuring section, the rolling average value of the flow velocity values measured by the N pitot tubes is obtained, the continuous output of the non-uniform flow field gas flow is realized, and the accuracy of the non-uniform flow field gas flow measurement is obviously improved; furthermore, the N pitot tubes are connected with the same differential pressure transmitter, so that the workload of a field calibration test is reduced, and the cost is reduced.)

1. A method for measuring gas flow in a non-uniform flow field is characterized in that: arranging N pitot tubes on the measuring section according to a grid method, circularly obtaining flow velocity values measured by the N pitot tubes, taking a rolling average value of continuous N flow velocity values as an average flow velocity of the measuring section, and multiplying the average flow velocity by the sectional area of the measuring section to obtain the gas flow of the section, wherein N is more than or equal to 4.

2. The non-uniform flow field gas flow measurement method of claim 1, wherein: and reversely blowing the pitot tube one by compressed air to prevent the pitot tube from being blocked, wherein the obtained flow rate value is the flow rate value of the pitot tube which is not in the reverse blowing state at any moment.

3. A non-uniform flow field gas flow measurement method according to claim 1 or 2, wherein: the N pitot tubes are connected with the same differential pressure transmitter, total pressure joints of the pitot tubes are connected to a positive pressure end of the differential pressure transmitter through first pressure leading tubes respectively, and each first pressure leading tube is provided with a total pressure on-off valve; and the static pressure joint of each pitot tube is connected to the negative pressure end of the differential pressure transmitter through a second pressure leading pipe respectively, and each second pressure leading pipe is provided with a static pressure on-off valve.

4. A non-uniform flow field gas flow measurement method according to claim 3, wherein: all the first pressure leading pipes are converged to a total pressure pipe, and the total pressure pipe is communicated with a positive pressure end of the differential pressure transmitter; all the second pressure leading pipes are converged to the static pressure pipe, and the static pressure pipe is communicated with the negative pressure end of the differential pressure transmitter.

5. A non-uniform flow field gas flow measurement method according to claim 3, wherein: the total pressure on-off valve and the static pressure on-off valve which are correspondingly connected with a single pitot tube are always opened or closed simultaneously, N pitot tubes are controlled to be sequentially communicated with the positive pressure end and the negative pressure end of the differential pressure transmitter in a round-robin mode through the on-off of the total pressure on-off valve and the static pressure on-off valve which correspond to the pitot tubes, the flow velocity values measured by the N pitot tubes are obtained in the round-robin mode, the rolling average value of the continuous N flow velocity values is used as the average flow velocity of the measured section, and the average flow velocity is multiplied by the sectional area of the measured section, so that the gas flow of the section can be obtained.

6. A non-uniform flow field gas flow measurement system which characterized in that: the device at least comprises a pitot tube, a first pressure leading pipe, a second pressure leading pipe and a differential pressure transmitter;

the number of the pitot tubes is N, the N pitot tubes are distributed on the measuring section according to a grid method, wherein N is more than or equal to 4;

the number of the first pressure guide pipes is equal to that of the pitot tubes, the pitot tubes correspond to the number of the pitot tubes one by one, the total pressure joints of the pitot tubes are connected to the positive pressure end of the differential pressure transmitter through the corresponding first pressure guide pipes respectively, and each first pressure guide pipe is provided with a total pressure on-off valve;

the number of the second pressure guide pipes is equal to that of the pitot tubes, the pitot tubes correspond to the pitot tubes one by one, the static pressure joints of the pitot tubes are connected to the negative pressure end of the differential pressure transmitter through the corresponding second pressure guide pipes respectively, and the second pressure guide pipes are provided with static pressure on-off valves.

7. The non-uniform flow field gas flow measurement system of claim 7, wherein: the device also comprises a total pressure pipe and a static pressure pipe; the total pressure joints of the pitot tubes are connected to a total pressure pipe through corresponding first pressure leading pipes respectively, and the total pressure pipe is communicated with the positive pressure end of the differential pressure transmitter; and the static pressure joints of the pitot tubes are respectively connected to the static pressure tube through corresponding second pressure leading tubes, and the static pressure tube is communicated with the negative pressure end of the differential pressure transmitter.

8. The non-uniform flow field gas flow measurement system of claim 6 or 7, wherein: the device also comprises a compressed air blowback pipe; the quantity of the compressed air back flushing pipes is equal to the sum of the quantity of the first pressure guiding pipes and the second pressure guiding pipes and corresponds to the sum of the quantity of the compressed air back flushing pipes one by one, the compressed air back flushing pipes are connected to the corresponding first pressure guiding pipes or the corresponding second pressure guiding pipes, and the interface positions of the compressed air back flushing pipes are positioned between the total pressure on-off valves or the static pressure on-off valves and the pitot tubes; each compressed air blowback pipe is provided with a blowback control valve.

9. The non-uniform flow field gas flow measurement system of claim 8, wherein: more than two total pressure on-off valves are replaced by a total pressure integrated valve, more than two static pressure on-off valves are replaced by a static pressure integrated valve, and more than two back-blowing control valves are replaced by a back-blowing integrated valve.

10. The non-uniform flow field gas flow measurement system of claim 8, wherein: sequentially opening the back-blowing control valves corresponding to the pitot tubes, and closing the total pressure on-off valve or the static pressure on-off valve corresponding to the pitot tube when the two back-blowing control valves corresponding to the pitot tubes are opened; the total pressure on-off valve and the corresponding back-blowing control valve are replaced by a three-way electromagnetic valve, and the static pressure on-off valve and the corresponding back-blowing control valve are replaced by a three-way electromagnetic valve.

Technical Field

The invention relates to a method and a system for measuring gas flow in a non-uniform flow field, belonging to the field of gas flow monitoring.

Background

In modern enterprise production, a boiler needs to send a large amount of wind every hour and simultaneously produces a large amount of flue gas. With the deep innovation of the economic system and the subdivision of economic accounting units in China, the trend of carrying out cost accounting and management and fully reducing energy consumption is developed, and the significance of the measurement of the dust-containing gas flow of a large pipeline is more and more important and is more and more concerned and valued by people.

In the industrial production process, in the measurement of four thermal parameters of temperature, pressure, flow and liquid level, the difficulty that flow measurement is expected to reach the expected accuracy and reliability is the biggest for the automatic control engineer generally, and especially the measurement of large pipeline air volume and flue gas flow is more obvious and troublesome, and the reason is the following: the measured fluid generally has the characteristics of high temperature, large dust content, strong corrosivity and the like; and secondly, the pipeline for conveying the fluid has large sectional area, short straight pipe section, more elbows, uneven flow field, large flow change range, small static pressure and low flow speed. Therefore, to accurately measure the large-pipeline air volume and the flue gas flow, not only the flow meter needs to be reasonably designed and selected, but also the flow meter needs to be correctly installed and used, and the accuracy and the reliability of the measured value can be ensured only through omnibearing management and control.

The matrix differential pressure flowmeter is developed for measuring the gas flow in the non-uniform flow field, and the core technical idea is that a plurality of pressure sensing measuring points are arranged on a large section and collected, so that multi-point pressure equalizing (connected with a differential pressure transmitter later) is realized, and the measurement accuracy is improved. On the premise that the flow field distribution rule is basically unchanged, the flow coefficient of the flowmeter is obtained through a field calibration test, the gas flow can be measured more accurately, and once the flow field distribution rule changes, the flow coefficient changes along with the change, so that the gas flow cannot be measured accurately. The reason for this is that, the channeling exists among the pressure sensing measuring points, the kinetic energy of the gas flow cannot be completely converted into potential energy, that is, the obtained differential pressure signal after pressure equalization is distorted, and the flow coefficient is unstable.

The pitot tube is a tubular device for measuring total pressure and static pressure of airflow to determine airflow speed, and is provided with a total pressure joint and a static pressure joint which are respectively connected with a positive pressure end and a negative pressure end of a differential pressure gauge, and the flow speed v of a certain point in fluid can be measured by applying a Bernoulli equation:

in the formula: p-differential pressure value, Pa, measured by a pitot tube;

p-fluid density, kg/m³；

K-flow coefficient of the pitot tube.

The flow coefficient K of the pitot tube is stable, but a single pitot tube can only measure the flow velocity of a certain point, the flow velocity of the point cannot represent the average flow velocity of the whole measuring section, and if the flow velocity of the gas in the whole section is calculated by the flow velocity of the pitot tube, a large deviation exists.

Disclosure of Invention

In order to solve the technical problems, the invention provides a non-uniform flow field gas flow measuring method and system, so as to achieve the purpose of improving the accuracy and universality of the non-uniform flow field gas flow measurement, and further reduce the workload of a field calibration test.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a non-uniform flow field gas flow measuring method comprises the steps of arranging N pitot tubes on a measuring section according to a grid method, circularly obtaining flow velocity values measured by the N pitot tubes, taking a rolling average value of continuous N flow velocity values as an average flow velocity of the measuring section, and multiplying the average flow velocity by the sectional area of the measuring section to obtain the gas flow of the section, wherein N is larger than or equal to 4.

The rolling average is the average of N successive flow rate values, and is not required for the pitot tube starting tube.

The method obviously improves the accuracy of the gas flow measurement of the non-uniform flow field, has novel and original conception, simple scheme and obvious effect, and is easy to popularize.

In order to ensure the accuracy of measurement, the pitot tube is blown back by compressed air in a round-trip mode during operation, so that the pitot tube is prevented from being blocked. At any moment, the obtained flow rate value is the flow rate value of the pitot tube which is not in the back blowing state, namely, at any moment, the back blowing and the measurement are not the same pitot tube. This ensures the accuracy of the measurement and the safety of the device.

In order to reduce the workload of a field calibration test, the N pitot tubes are connected with the same differential pressure transmitter, the total pressure joints of the pitot tubes are connected to the positive pressure end of the differential pressure transmitter through first pressure leading pipes respectively, and each first pressure leading pipe is provided with a total pressure on-off valve; and the static pressure joint of each pitot tube is connected to the negative pressure end of the differential pressure transmitter through a second pressure leading pipe respectively, and each second pressure leading pipe is provided with a static pressure on-off valve. Because the flow coefficient K of the pitot tube is stable, the accuracy of flow measurement can be judged by calibrating one differential pressure transmitter.

In order to facilitate connection and installation, all the first pressure leading pipes are converged to a total pressure pipe, and the total pressure pipe is communicated with a positive pressure end of the differential pressure transmitter; all the second pressure leading pipes are converged to the static pressure pipe, and the static pressure pipe is communicated with the negative pressure end of the differential pressure transmitter.

In order to further improve the accuracy of measurement, the total pressure on-off valve and the static pressure on-off valve which are correspondingly connected with the single pitot tube are always opened or closed simultaneously.

For convenience of control and measurement accuracy, as a specific implementation scheme, the N pitot tubes are controlled to be sequentially communicated with the positive pressure end and the negative pressure end of the differential pressure transmitter through the on-off of the total pressure on-off valve and the static pressure on-off valve corresponding to each pitot tube, the flow velocity values measured by the N pitot tubes are obtained through round-robin, the rolling average value of the continuous N flow velocity values is used as the average flow velocity of the measurement section, and the average flow velocity is multiplied by the sectional area of the measurement section, so that the gas flow of the section can be obtained.

A non-uniform flow field gas flow measurement system at least comprises a pitot tube, a first pressure pipe, a second pressure pipe and a differential pressure transmitter;

the number of the pitot tubes is N, the N pitot tubes are distributed on the measuring section according to a grid method, wherein N is more than or equal to 4;

the number of the first pressure guide pipes is equal to that of the pitot tubes, the pitot tubes correspond to the number of the pitot tubes one by one, the total pressure joints of the pitot tubes are connected to the positive pressure end of the differential pressure transmitter through the corresponding first pressure guide pipes respectively, and each first pressure guide pipe is provided with a total pressure on-off valve;

the number of the second pressure guide pipes is equal to that of the pitot tubes, the pitot tubes correspond to the pitot tubes one by one, the static pressure joints of the pitot tubes are connected to the negative pressure end of the differential pressure transmitter through the corresponding second pressure guide pipes respectively, and the second pressure guide pipes are provided with static pressure on-off valves.

The N pitot tubes are connected with the same differential pressure transmitter, so that the accuracy of flow measurement can be judged only by calibrating one differential pressure transmitter, the flow coefficient K of the pitot tubes is stable, and the workload of a field calibration test is reduced.

The above grid method is performed with reference to GB/T10184-2015.

The non-uniform flow field gas flow measuring system is convenient to connect and install and further comprises a total pressure pipe and a static pressure pipe; the total pressure joints of the pitot tubes are connected to a total pressure pipe through corresponding first pressure leading pipes respectively, and the total pressure pipe is communicated with the positive pressure end of the differential pressure transmitter; and the static pressure joints of the pitot tubes are respectively connected to the static pressure tube through corresponding second pressure leading tubes, and the static pressure tube is communicated with the negative pressure end of the differential pressure transmitter.

In order to prevent the pitot tube from being blocked and improve the reliability of the measurement system, the non-uniform flow field gas flow measurement system also comprises a compressed air blowback pipe; the quantity of the compressed air back flushing pipes is equal to the sum of the quantity of the first pressure guiding pipes and the quantity of the second pressure guiding pipes, the compressed air back flushing pipes correspond to the first pressure guiding pipes or the second pressure guiding pipes one by one, the compressed air back flushing pipes are connected to the corresponding first pressure guiding pipes or the corresponding second pressure guiding pipes, and the positions of interfaces (the connecting positions of the compressed air back flushing pipes and the first pressure guiding pipes or the second pressure guiding pipes) of the compressed air back flushing pipes are between the total pressure on-off valves or the static pressure on-off valves and the pitot tubes; each compressed air blowback pipe is provided with a blowback control valve. In order to improve the anti-blocking back-blowing effect, back-blowing control valves corresponding to the pitot tubes are opened in sequence, and when two back-blowing control valves corresponding to the pitot tubes are opened, total pressure on-off valves or static pressure on-off valves corresponding to the pitot tubes are closed.

And the back-blowing control valve corresponding to the pitot tube is a back-blowing control valve connected to a compressed air back-blowing pipe on the first pressure guide pipe and the second pressure guide pipe corresponding to the pitot tube.

During practical application, a plurality of total pressure on-off valves can be replaced by a total pressure integrated valve, a plurality of static pressure on-off valves can be replaced by a static pressure integrated valve, and a plurality of back-blowing control valves can also be replaced by a back-blowing integrated valve, so that the system integration level is improved.

For convenient control, the total pressure on-off valve, the static pressure on-off valve and the back-blowing control valve can be electromagnetic valves.

The total pressure on-off valve and the corresponding back-blowing control valve are replaced by a three-way electromagnetic valve, and the static pressure on-off valve and the corresponding back-blowing control valve are replaced by a three-way electromagnetic valve, so that the system integration level is improved.

The back-blowing control valve corresponding to the total pressure on-off valve refers to a back-blowing control valve on a compressed air back-blowing pipe connected to a first pressure leading pipe where the total pressure on-off valve is located. And the back-blowing control valve corresponding to the static pressure on-off valve refers to a back-blowing control valve on a compressed air back-blowing pipe connected to a second pressure leading pipe where the static pressure on-off valve is located.

When the differential pressure transmitter is used, the differential pressure transmitter can be electrically connected with an information control processor of the control display cabinet, and a measured value is displayed by the control display cabinet.

The prior art is referred to in the art for techniques not mentioned in the present invention.

According to the non-uniform flow field gas flow measuring method, N pitot tubes are arranged on the measuring section, the average value of the flow velocity values measured by the N pitot tubes is obtained, the non-uniform flow field gas flow is obtained through calculation, and the accuracy of the non-uniform flow field gas flow measurement is improved; furthermore, the N pitot tubes are connected with the same differential pressure transmitter, so that the workload of a field calibration test is reduced, and the cost is reduced; through compressed air blowback, improved flow measurement's accuracy and stability, prolonged pitot tube's life, prolonged the maintenance cycle, reduced the maintenance cost.

Drawings

FIG. 1 is a schematic view of a pitot tube of the present invention in a measurement cross-section;

FIG. 2 is a side view of FIG. 1;

FIG. 3 is a top view of FIG. 1;

FIG. 4 is a schematic view of a non-uniform flow field gas flow measurement system in embodiment 5 of the present invention;

FIG. 5 is a schematic view of a non-uniform flow field gas flow measurement system in embodiment 8 of the present invention;

in the figure, 1 is a pitot tube, 1-1 is a total pressure joint, 1-2 is a static pressure joint, 2 is a first pressure leading pipe, 3 is a total pressure on-off valve, 4 is a second pressure leading pipe, 5 is a static pressure on-off valve, 6 is a total pressure pipe, 7 is a static pressure pipe, 8 is a differential pressure transmitter, 9 is a compressed air back-blowing pipe, and 10 is a gas flow direction.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

Example 1

As shown in FIGS. 1-4, in the non-uniform flow field gas flow measurement method, N pitot tubes are arranged on a measurement section according to a grid method, flow velocity values measured by the N pitot tubes are obtained in a round-robin manner, a rolling average value of continuous N flow velocity values is used as an average flow velocity of the measurement section, and the average flow velocity is multiplied by a sectional area of the measurement section, so that the gas flow of the section is obtained, wherein N is more than or equal to 4.

The method obviously improves the accuracy of the gas flow measurement of the non-uniform flow field, and has the advantages of novel conception, simple scheme, obvious effect and easy popularization.

Example 2

On the basis of the embodiment 1, the following improvements are further made: and reversely blowing the pitot tube one by compressed air to prevent the pitot tube from being blocked, wherein the obtained flow rate value is the flow rate value of the pitot tube which is not in the reverse blowing state at any moment.

Example 3

On the basis of the embodiment 2, the following improvements are further made: as shown in fig. 4, in order to reduce the workload of the field calibration test, the N pitot tubes are connected to the same differential pressure transmitter, the total pressure joints of the pitot tubes are connected to the positive pressure end of the differential pressure transmitter through first pressure pipes, and each first pressure pipe is provided with a total pressure on-off valve; and the static pressure joint of each pitot tube is connected to the negative pressure end of the differential pressure transmitter through a second pressure leading pipe respectively, and each second pressure leading pipe is provided with a static pressure on-off valve. Therefore, the accuracy of flow measurement can be judged only by calibrating the differential pressure transmitter.

Example 4

On the basis of the embodiment 3, the following improvements are further made: as shown in fig. 1-3, for convenience of connection and installation, all the first pressure leading pipes are merged to a total pressure pipe, and the total pressure pipe is communicated with a positive pressure end of the differential pressure transmitter; all the second pressure leading pipes are converged to the static pressure pipe, and the static pressure pipe is communicated with the negative pressure end of the differential pressure transmitter.

Example 5

On the basis of the embodiment 4, the following improvements are further made: in order to further improve the accuracy of measurement, the total pressure on-off valve and the static pressure on-off valve which are correspondingly connected with the single pitot tube are always opened or closed simultaneously. For convenience of control and measurement accuracy, as a specific implementation scheme, the N pitot tubes are controlled to be sequentially communicated with the positive pressure end and the negative pressure end of the differential pressure transmitter through the on-off of the total pressure on-off valve and the static pressure on-off valve corresponding to each pitot tube, the flow velocity values measured by the N pitot tubes are obtained through round-robin, the rolling average value of the continuous N flow velocity values is used as the average flow velocity of the measurement section, and the average flow velocity is multiplied by the sectional area of the measurement section, so that the gas flow of the section can be obtained.

As shown in fig. 4, a non-uniform flow field gas flow measurement system for implementing the measurement method includes a pitot tube, a first pressure pipe, a second pressure pipe, a total pressure pipe, a static pressure pipe and a differential pressure transmitter;

the number of the pitot tubes is N, the N pitot tubes are distributed on the measuring section according to a grid method, wherein N is more than or equal to 4;

the number of the first pressure guide pipes is equal to that of the pitot tubes and corresponds to the pitot tubes one by one, the total pressure joints of the pitot tubes are connected to the total pressure pipes through the corresponding first pressure guide pipes respectively, the total pressure pipes are communicated with the positive pressure end of the differential pressure transmitter, and each first pressure guide pipe is provided with a total pressure on-off valve;

the number of the second pressure leading pipes is equal to that of the pitot tubes and corresponds to the pitot tubes one by one, the static pressure joints of the pitot tubes are connected to the static pressure pipe through the corresponding second pressure leading pipes respectively, the static pressure pipe is communicated with the negative pressure end of the differential pressure transmitter, and each second pressure leading pipe is provided with a static pressure on-off valve.

The N pitot tubes are connected with the same differential pressure transmitter, so that the accuracy of flow measurement can be judged only by calibrating the differential pressure transmitter, and the workload of a field calibration test is reduced.

Example 6

On the basis of the embodiment 5, the following improvements are further made: as shown in fig. 5, in order to prevent the pitot tube from being blocked and improve the reliability of the measurement system, the non-uniform flow field gas flow measurement system further comprises a compressed air blowback pipe; the quantity of the compressed air back flushing pipes is equal to the sum of the quantity of the first pressure guiding pipes and the second pressure guiding pipes and corresponds to the sum of the quantity of the compressed air back flushing pipes one by one, the compressed air back flushing pipes are connected to the corresponding first pressure guiding pipes or the corresponding second pressure guiding pipes, and the interface positions of the compressed air back flushing pipes are positioned between the total pressure on-off valves or the static pressure on-off valves and the pitot tubes; each compressed air blowback pipe is provided with a blowback control valve. When the anti-blocking back-blowing control valve is operated, the back-blowing control valves corresponding to the pitot tubes are opened in sequence for improving the anti-blocking back-blowing effect, and when the two back-blowing control valves corresponding to the pitot tubes are opened, the total pressure on-off valve or the static pressure on-off valve corresponding to the pitot tubes is closed. .

Example 7

On the basis of the embodiment 6, the following improvements are further made: all total pressure on-off valves are replaced by a total pressure integrated valve, all static pressure on-off valves are replaced by a static pressure integrated valve, and all back-blowing control valves are also replaced by a back-blowing integrated valve.

Example 8

On the basis of the embodiment 6, the following improvements are further made: as shown in fig. 5, the total pressure on-off valve, the static pressure on-off valve and the back-blowing control valve are all electromagnetic valves, the total pressure on-off valve and the back-blowing control valve corresponding to the total pressure on-off valve are replaced by a three-way electromagnetic valve, and the static pressure on-off valve and the back-blowing control valve corresponding to the static pressure on-off valve are replaced by a three-way electromagnetic valve. To improve system integration.

Through the arrangement of the back flushing pipe and the like, the accuracy and the stability of flow measurement are improved, the service life of the pitot tube is prolonged, the overhaul period is prolonged, and the maintenance cost is reduced.