CN214121300U

CN214121300U - Unstable liquid measuring device of flow in closed pipeline

Info

Publication number: CN214121300U
Application number: CN202120435154.9U
Authority: CN
Inventors: 李雪菁
Original assignee: Shanghai Institute of Measurement and Testing Technology
Current assignee: Shanghai Institute of Measurement and Testing Technology
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2021-09-03
Anticipated expiration: 2031-02-26

Abstract

The utility model belongs to the technical field of liquid flow measurement, and particularly discloses a liquid measuring device for unstable flow in a closed pipeline; comprises a pipeline, wherein a water inlet and a first water outlet are respectively arranged at two ends of the pipeline; the pipeline is also provided with a standard meter electromagnetic flowmeter; a flow stabilizer is arranged between the standard meter electromagnetic flowmeter and the first water outlet; an ultrasonic flowmeter is arranged between the flow stabilizer and the first water outlet; a glass window is arranged between the ultrasonic flowmeter and the first water outlet.

Description

Unstable liquid measuring device of flow in closed pipeline

Technical Field

The utility model belongs to the technical field of liquid flow measurement, concretely relates to unstable liquid measuring device of flow in closed pipeline.

Background

Closed conduit fluid metering is a very important part of industrial process control. Flow measurement problems typically arise from the metering and control requirements for full line fluid, and most flow sensors are based on full line condition flow measurement methods. However, with the increasing water consumption in industrial and agricultural production and society, there is an increasing demand for unstable flow and non-full pipe flow measurement in the fields of sewage discharge flow monitoring and water resource transportation and measurement. In recent years, our country has paid more and more attention to the safety and management of water resource transportation and discharge. The supply and discharge delivery pipelines of the water resource system are often in a non-full pipe and unstable flow state. If a corresponding flow measurement method and a corresponding flow measurement device are lacked, the requirements of energy conservation and emission reduction monitoring on pipeline supply and drainage flow management are obviously difficult to meet.

Both flow instabilities and non-full pipe fluids are characterized by free surface water motion. For this feature, open channels are one of the commonly used measurement methods. Open channels have achieved certain performance in some hydraulic projects, but have certain limitations on non-full pipe flow measurement, and open channels cannot be used in sewage treatment, particularly in toxic and harmful sewage treatment. Another method of metering non-full pipe fluid is: "level gauge + flow meter". But the problems of high cost, difficult later maintenance, incapability of real-time measurement and the like in the process of non-full pipe measurement by utilizing multiple sensors are solved. The use of multiple sensors is greatly limited, particularly when metering toxic hazardous fluids. There are also ultrasonic flow meters which are sold under the claim of "not full pipe" flow measurement, but when the flow rate is low, the flow is unstable, and the liquid level is below 50% of the total liquid level, accurate measurement cannot be performed.

When the flow is unstable, even in the state that the pipeline is not full, the key technology to be solved is the relationship between the flow and the liquid level change of the non-full pipeline (generally, the full degree range of the fluid is considered to be 10% -100%). The utility model provides a, when the closed conduit, to unstable, the not full state of managing of fluid flow, solve the accurate measuring device and the method of industrial field to the flow.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a measure unstable liquid measurement device of accurate closed pipeline internal flow under the full pipe state of non-.

Based on the above purpose, the utility model adopts the following technical scheme:

a device for measuring unstable liquid flow in a closed pipeline comprises a pipeline, wherein a water inlet and a first water outlet are respectively arranged at two ends of the pipeline; a standard meter electromagnetic flowmeter is also arranged on the pipeline, and a weighing method flow measuring mechanism is arranged between the standard meter electromagnetic flowmeter and the water inlet; a flow stabilizer is arranged between the standard meter electromagnetic flowmeter and the first water outlet; an ultrasonic flowmeter is arranged between the flow stabilizer and the first water outlet; a glass window is arranged between the ultrasonic flowmeter and the first water outlet, and the flow stabilizer, the ultrasonic flowmeter and the glass window are all arranged on the pipeline.

Furthermore, four pairs of capacitance electrodes are laid on the upper and lower parts of the insulating pipe wall of the electromagnetic flowmeter of the standard meter and are uniformly distributed around the insulating pipe wall; any one capacitor electrode is arc-shaped, the central opening angle of any one capacitor electrode is 40 degrees, and the gaps between any two adjacent capacitor electrodes are equal; the four continuous capacitance electrodes are positive plates, the four capacitance electrodes opposite to the positive plates are negative plates, and the positive plates and the negative plates are respectively positioned on the upper side and the lower side of the insulating pipe wall; and a shielding cover is arranged outside the circular ring formed by the capacitor electrodes.

Further, the flow stabilizer comprises a first cuboid water tank, a water inlet pipe is arranged at the bottom of the first water tank, the water inlet pipe comprises a vertical pipe, the bottom end of the vertical pipe is communicated with a pipeline on one side of the first water tank, which is close to the electromagnetic flowmeter of the standard meter, the top end of the vertical pipe is connected with a bent pipe, and the bent pipe is an arc-shaped pipeline which is bent downwards; a liquid inlet is formed in one end, away from the vertical pipe, of the bent pipe and is positioned at the bottom of the first water tank; a liquid outlet is arranged above the liquid inlet and is arranged above the bent pipe, and the liquid outlet is communicated with a pipeline on one side of the first water tank, which is far away from the electromagnetic flowmeter of the standard meter; a plurality of throttle orifice plates are arranged in the first water tank, and through holes which are uniformly distributed are formed in any throttle orifice plate; the throttling orifice plate comprises horizontal plates arranged in parallel with the bottom surface of the first water tank, and any horizontal plate is hermetically connected with four side walls of the first water tank; the throttling orifice plate also comprises vertical plates which are perpendicular to the horizontal plate, any vertical plate is hermetically connected with the bottom end and the side wall of the first water tank, and the vertical plate is not hermetically connected with the top end of the first water tank; the vertical plates comprise transverse plates and longitudinal plates which are arranged in a crossed manner; the top of the first water tank is provided with a breather valve.

Further, the ultrasonic flowmeter is clamped on the pipeline; the glass window is transparent and tubular, two ends of the glass window are communicated with the pipeline, a liquid level graduated scale is arranged on the glass window, and a capacitance type liquid level switch is arranged in the glass window.

Further, an excitation system of the standard meter electromagnetic flowmeter is low-frequency square wave excitation; a filter circuit is arranged in the electromagnetic flowmeter of the standard meter.

Furthermore, the weighing method flow measurement mechanism comprises a commutator connected with the pipeline, a second water outlet and a third water outlet are arranged on the commutator, and a second water tank communicated with the second water outlet is arranged below the second water outlet; a bearing container communicated with the third water outlet is arranged below the third water outlet, and an electronic scale is arranged below the bearing container and used for weighing the weight of the bearing container; one end of the second water tank, which is far away from the commutator, is communicated with the pipeline, and a pipeline pump is arranged on the pipeline of one side of the second water tank, which is far away from the commutator.

Furthermore, a metal corrugated pipe is arranged between the commutator and the water inlet, and both ends of the metal corrugated pipe are communicated with the pipeline; and a manual valve is arranged on a pipeline between the second water tank and the pipeline pump, and a manual valve is arranged on a pipeline between the electromagnetic flowmeter of the standard meter and the flow stabilizer.

Furthermore, a control system is arranged in the electromagnetic flowmeter of the standard meter and used for receiving capacitance value information, and the control system is connected with an LED warning lamp.

Compared with the prior art, the utility model discloses following beneficial effect has:

the metal corrugated pipe can buffer the impact force on the electronic scale under different filling degrees, and reduce the error of the electronic scale under a weighing method.

The flow of the measured fluid is usually in a low-pressure or non-pressure state, and the uncertainty of the whole device is ensured by selecting a high-precision electronic scale under the conditions that the pressure loss is very small and the total head loss of the device changes at any time.

The glass window with scales is internally provided with a capacitance type liquid level switch for monitoring different liquid levels at any time, and simultaneously, the liquid level can be observed through a graduated scale on the glass window. The values of the two can be compared, and the uncertainty of liquid level measurement is reduced.

The ultrasonic flowmeter is directly clamped on the pipeline, the pipeline does not need to be disassembled, when the fullness is (50-100)%, the reading of the ultrasonic flowmeter can be compared with a standard meter, and the reading uncertainty of the standard meter is reduced.

The capacitor electrode is provided with a shielding cover outside to prevent interference on the measuring electrode.

The capacitor electrodes are uniformly laid outside the insulating pipe wall, and the size of each capacitor electrode is the same and the gap between every two electrodes is also the same in size design. This design is designed to maximize the measurement of the level variation and to ensure that measurements with a fullness below 50% are met. Theoretically, the more the number of the capacitor electrodes is, the more the capacitance value between every two electrode plates can be measured, the higher the measurement precision is, and the accuracy is also improved. However, if the number of the capacitor electrodes is increased, the design of the hardware circuit is more complicated in implementation, and the manufacturing cost is increased. The utility model discloses 4 to the electric capacity electrode, and the design of 40 degrees of central flare angles, not only guaranteed measuring precision, and reduced complexity and cost in the aspect of hardware circuit's design realization.

In the standard meter electromagnetic flowmeter, an excitation system adopts low-frequency square wave excitation, and an excitation circuit designed by a following circuit and an inverting circuit is shown in the attached drawing. The selection of the excitation mode directly affects the accuracy of the measurement. In the case of unstable flow of fluid, finding a way to provide a stable, uniform magnetic field is an effective way to ensure the sensitivity of the device. The direct current excitation easily generates a polarization phenomenon, and the alternating current excitation reduces the signal-to-noise ratio. The low-frequency square wave excitation provides a more uniform magnetic field for the electromagnetic flowmeter of the standard meter, and simultaneously avoids the defects of direct current excitation and alternating current excitation. In the whole process, the magnetic field generated by the low-frequency rectangular wave is in a periodic change process, and is an alternating signal, so that later amplification and processing are facilitated.

The flow stabilizer is a cuboid, obtains better measuring effect for ensuring the requirements of stable flow of fluid in the pipe and liquid level of the non-full pipe, adopts layered design, and is provided with a breather valve at the top end of the device. The breather valve ensures the communication of the internal liquid with the air, and ensures the overflow of the fluid when the pipe is full. The inside adopts the orifice plate. When the flow is unstable and not full of pipe flow, the flow speed and the flow inside the device are unstable, and very large errors are caused to the measurement. The lower edge and the two side edges of the pore plate are hermetically connected with the interior of the device box body. The liquid inlet is communicated with the liquid outlet but not on a horizontal plane, and the liquid inlet of the elbow structure is arranged at the bottom of the device. When the liquid level rises gradually from the low position, each layer of unit in the device is filled gradually, the unit is the gap between the adjacent horizontal plates, and the interface of the fluid and the air in the whole process keeps a stable rising or falling state.

The flow stabilizer is formed by arranging a plurality of vertical plates and horizontal plates in a crossed manner, so that n small water storage partitions are formed. When water flows in, the water storage partition is gradually filled with water, and the stability of the water level is ensured.

Drawings

Fig. 1 is a structural diagram of a liquid flow instability measuring device in embodiment 1 of the present invention;

FIG. 2 is a schematic view of a glass window in embodiment 1 of the present invention;

fig. 3 is a schematic structural diagram of a standard meter electromagnetic flowmeter according to embodiment 1 of the present invention;

fig. 4 is a circuit diagram of an excitation module of the electromagnetic flowmeter of the standard meter according to the embodiment 1 of the present invention;

fig. 5 is a schematic structural view of a flow stabilizer of embodiment 1 of the present invention;

fig. 6 is a circuit diagram of a filter module of an electromagnetic flowmeter of the standard meter according to embodiment 1 of the present invention;

fig. 7 is a schematic diagram of the capacitance electrode distribution of the electromagnetic flowmeter of embodiment 1 of the present invention.

In the figure: DN50 bellows 1, DN50 glass window 2, ultrasonic flowmeter 3, DN20 manual valve 4, standard meter electromagnetic flowmeter 5, pipeline pump 6, DN40 manual valve 7, second water tank 8, electronic scale 9, bearing container 10, commutator 11, flow stabilizer 12, first water tank 13, bent pipe 14, vertical pipe 15, water inlet 16, first water outlet 17, second water outlet 18, third water outlet 19, pipeline 20, support 21, shield 22, capacitance electrode 23, liquid 24, insulating pipe wall 25 and orifice plate 26.

Detailed Description

Example 1

The utility model discloses a collect device of non-full pipe flow of measurable quantity as an organic whole of standard meter method and static quality method. Flow range: (1 to 800) m³The fluid fullness ranges from 10% to 100%. The device expansion uncertainty under the static mass method was 0.06%, and the device expansion uncertainty under the standard gauge method was 0.2%. The standard meter adopts an electromagnetic type electromagnetic flowmeter, and the electrodes of the flowmeter adopt 4 pairs of capacitance electrodes. The relationship between liquid level and average flow rate can be obtained from a standard table, which in turn yields the liquid 24 flow rate.

A device for measuring unstable liquid 24 flowing in a closed pipeline 20 is shown in figure 1 and comprises a pipeline 20, wherein the pipeline 20 is arranged on a support 21, and a water inlet 16 and a first water outlet 17 are respectively arranged at two ends of the pipeline 20; a standard meter electromagnetic flowmeter 5 is also arranged on the pipeline 20, and a weighing method flow measurement mechanism is arranged between the standard meter electromagnetic flowmeter 5 and the water inlet 16; a flow stabilizer 12 is arranged between the standard meter electromagnetic flowmeter 5 and the first water outlet 17; an ultrasonic flowmeter 3 is arranged between the flow stabilizer 12 and the first water outlet 17; a DN50 glass window 2 is arranged between the ultrasonic flowmeter 3 and the first water outlet 17.

As shown in fig. 1, a DN50 bellows 1 is arranged between a commutator 11 and a water inlet 16 of the weighing method flow measuring mechanism, two ends of the DN50 bellows 1 are both communicated with a pipeline 20, and the DN50 bellows 1 can buffer impact force on an electronic scale 9 under different fullness degrees, so that error of the electronic scale 9 under the weighing method is reduced; a DN40 manual valve 7 is arranged on the pipeline 20 between the second water tank 8 and the pipeline pump 6, and a DN20 manual valve 4 is arranged on the pipeline 20 between the electromagnetic flowmeter 5 and the flow stabilizer 12 of the standard meter.

As shown in fig. 1, the weighing flow measuring mechanism includes a diverter 11 connected to a pipeline 20, the diverter 11 is provided with a second water outlet 18 and a third water outlet 19, and a second water tank 8 communicated with the second water outlet 18 is arranged below the second water outlet 18; a bearing container 10 communicated with the third water outlet 19 is arranged below the third water outlet 19, an electronic scale 9 is arranged below the bearing container 10, and the electronic scale 9 is used for weighing the weight of the bearing container 10; the electronic scale 9 is a MSE524S type scale from Saddoliss, Germany. The MSE524S has a resolution of 0.1mg, a precision of 1mg, and an accuracy rating of I. The flow of the measured fluid is usually in a low-pressure or non-pressure state, and the uncertainty of the whole device is ensured by selecting the high-precision electronic scale 9 under the conditions that the pressure loss is very small and the total head loss of the device changes at any time. One end of the second water tank 8 far away from the commutator 11 is communicated with a pipeline 20, and a pipeline pump 6 is arranged on the pipeline 20 on one side of the second water tank 8 far away from the commutator 11.

Further, the ultrasonic flow meter 3 is clamped on the pipe 20; the external clamp type ultrasonic flowmeter 3 is directly clamped on the pipeline 20, the pipeline 20 does not need to be disassembled, when the fullness is (50-100%), the reading of the ultrasonic flowmeter 3 can be compared with a standard meter, and the reading uncertainty of the standard meter is reduced.

As shown in fig. 1 and 2, the DN50 glass window 2 is transparent and tubular, two ends of the DN50 glass window 2 are both communicated with the pipeline 20, a liquid level scale is arranged on the DN50 glass window 2, and a capacitive liquid level switch is arranged in the DN50 glass window 2. DN50 glass window 2 with scale has a capacitanc level switch placed inside for monitor different liquid levels at any time, also can observe the liquid level through the scale on DN50 glass window 2 simultaneously. The values of the two can be compared, and the uncertainty of liquid level measurement is reduced.

As shown in fig. 2, T is DN50 glass window 2, L1 … Ln +1 is a liquid level switch at different liquid levels, DN50 glass window 2 has a fluid outflow end connected to a meter to be detected and the other end connected to an ultrasonic flowmeter 3. The fluid input of the ultrasonic flow meter 3 is connected to a flow smoother 12.

As shown in fig. 3, four pairs of capacitance electrodes 23 are laid outside the insulating pipe wall 25 of the standard meter electromagnetic flowmeter 5, and the four pairs of capacitance electrodes 23 are uniformly distributed around the insulating pipe wall 25; any one of the capacitor electrodes 23 is arc-shaped, the central opening angle of any one of the capacitor electrodes 23 is 40 degrees, and the gaps between any two adjacent capacitor electrodes 23 are equal; the four continuous capacitance electrodes 23 are positive plates, the four capacitance electrodes 23 opposite to the positive plates are negative plates, and the positive plates and the negative plates are respectively positioned at the upper side and the lower side of the lining; a shielding cover 22 is arranged outside the capacitor electrode 23; a control system is arranged in the standard meter electromagnetic flowmeter 5 and used for receiving capacitance value information, and the control system is connected with an LED warning lamp; the control system is also used for receiving DN50 information of a liquid level switch in the glass window 2.

The standard meter electromagnetic flowmeter 5 adopts 4 pairs of capacitance sheets, obtains the capacitance value between every two capacitance electrodes 23 through the prior art, obtains the average flow velocity related to the liquid level height after being processed by a control system, and further obtains the flow rate of the fluid in the pipe.

4 pairs of capacitance electrodes 23 are laid on the outer wall of an insulating pipe wall 25 of a sensor of the standard meter electromagnetic flowmeter 5, and the central opening angle of each circular arc electrode is 40 degrees. The sensor is provided with a shield 22 outside to prevent interference with the measuring electrodes.

The capacitance electrodes 23 of the standard meter electromagnetic flowmeter 5 are uniformly laid outside the insulating pipe wall 25, and the size of each capacitance electrode 23 is the same and the gap between every two electrodes is also the same in size design. This design is designed to maximize the measurement of the level variation and to ensure that measurements with a fullness below 50% are met. Theoretically, the larger the number of the capacitor electrodes 23 is, the more the capacitance value between each two electrode plates can be measured, the higher the measurement precision is, and the accuracy is also improved. However, if the number of the capacitor electrodes 23 is increased, the design of the hardware circuit is more complicated in implementation, and the manufacturing cost thereof is increased. The utility model discloses 4 to capacitor electrode 23, and the design of 40 degrees of central flare angles, not only guaranteed measuring precision, and reduced complexity and cost in the aspect of hardware circuit's design realization.

Further, an excitation system of the standard meter electromagnetic flowmeter 5 adopts low-frequency square wave excitation, and an excitation circuit designed by a follower circuit and an inverter circuit is shown in an attached figure 4. The selection of the excitation mode directly affects the accuracy of the measurement. In the case of unstable flow of fluid, finding a way to provide a stable, uniform magnetic field is an effective way to ensure the sensitivity of the device. The direct current excitation easily generates a polarization phenomenon, and the alternating current excitation reduces the signal-to-noise ratio. The low-frequency square wave excitation provides a more uniform magnetic field for the electromagnetic flowmeter 5 of the standard meter, and simultaneously avoids the defects of direct current excitation and alternating current excitation. In the whole process, the magnetic field generated by the low-frequency rectangular wave is in a periodic change process, and is an alternating signal, so that later amplification and processing are facilitated.

As shown in fig. 6, the electromagnetic flowmeter 5 of the standard meter adopts a filter circuit, which ensures that the anti-interference capability is strong at a certain response speed. S1a, S1b and S2a, S2b are synchronous switches. When the S1a, the S1b, the S2a and the S2b are disconnected, the input signal does not charge the capacitor, and the capacitor only holds the potential at the moment. When S1a and S1b are closed, the signal charges the capacitor from top to bottom, and when S2a and S2b are closed, the signal charges the capacitor from top to bottom.

As shown in fig. 5, the flow stabilizer 12 comprises a first water tank 13 in a rectangular parallelepiped shape, a water inlet pipe is arranged at the bottom of the first water tank 13, the water inlet pipe comprises a vertical pipe 15, the bottom end of the vertical pipe 15 is communicated with a pipeline 20 at one side of the first water tank 13 close to the electromagnetic flowmeter 5 of the standard meter, and the top end of the vertical pipe 15 is connected with a bent pipe 14; a liquid inlet is formed in one end, away from the vertical pipe 15, of the bent pipe 14 and is positioned at the bottom of the first water tank 13; a liquid outlet is arranged above the liquid inlet and is communicated with a pipeline 20 on one side of the first water tank 13 far away from the electromagnetic flowmeter 5 of the standard meter; a plurality of throttle orifice plates 26 are arranged in the first water tank 13, and through holes which are uniformly distributed are formed in any throttle orifice plate 26; the orifice plate 26 includes horizontal plates arranged in parallel with the bottom surface of the first water tank 13, and any one of the horizontal plates is hermetically connected with four side walls of the first water tank 13; the orifice plate 26 further comprises vertical plates arranged perpendicular to the horizontal plates, any vertical plate is hermetically connected with the bottom end and the side wall of the first water tank 13, and the vertical plates comprise transverse plates and longitudinal plates which are arranged in a crossed manner; the top end of the first water tank 13 is provided with a breather valve.

The flow stabilizer 12 is a cuboid, obtains better measuring effect for ensuring the requirements of stable flow of fluid in the pipe and liquid level of the non-full pipe, adopts a layered design, and is provided with a breather valve at the top end of the device. The breather valve ensures communication of the internal liquid 24 with air, and ensures spillage of the liquid when the tube is full. An orifice plate 26 is employed internally. When the flow is unstable and not full of pipe flow, the flow speed and the flow inside the device are unstable, and very large errors are caused to the measurement. The lower edge and the two side edges of the pore plate are hermetically connected with the interior of the device box body. The inlet is connected to the outlet but not in a horizontal plane and the outlet in the configuration of elbow 14 is located at the bottom of the device. When the liquid level rises gradually from the low position to fill each layer of unit in the device gradually, the interface of the whole process fluid and the air keeps a relatively stable rising or falling state. The flow stabilizer 12 plays an important role in accurate measurement of the standard meter, and the flow stabilizer 12 is formed by arranging a plurality of vertical plates and horizontal plates in a crossed manner to form n small water storage partitions. When water flows in, the water storage partition is gradually filled with water, and the stability of the water level is ensured.

When the device measures an unstable flow (not full pipe) of liquid 24, the measured portion is communicated with the inlet of the pipe 20 and the first outlet 17; water is pumped from the water tank to the pipeline 20 by the pipeline pump, the water flows through the measured flowmeter and the flow working standard, and the output flow of the measured flowmeter and the flow working standard are compared, so that the metering accuracy and the repeatability of the measured flowmeter are determined.

The measuring method of the unstable liquid 24 flow rate measuring device in the closed pipeline 20 comprises the following steps,

step 1, communicating a tested part with a water inlet 16 and a first water outlet 17, sequentially flowing liquid 24 to a commutator 11 of a weighing method flow measurement mechanism through the water inlet 16, respectively flowing the liquid 24 to a weighing container and a second water tank 8 through the commutator 11, pumping the liquid 24 in the second water tank 8 by a pipeline pump 6, and measuring the fluid by the non-full-pipe standard meter electromagnetic flow meter 5 when the liquid 24 flows to the standard meter electromagnetic flow meter 5 and the liquid 24 flows to the standard meter electromagnetic flow meter 5. When the flow is small and the liquid level is low, the measured fluid cannot fill the measuring pipeline 20, and the traditional liquid 24 measuring instrument cannot accurately measure the fluid. When the flow rate is low and the liquid level is not full of the measuring pipeline 20, the average flow rate has a certain relation with the liquid level, so that accurate parameters of the flow rate are obtained, and the method is a key technology for solving the problem of metering of the non-full pipe electromagnetic flowmeter. As the liquid 24 flows through the water flow stabilizer 12, as shown in fig. 5, the liquid 24 flows from the elbow 14 below through an orifice plate 26, above which is a breather valve in communication with the air. Liquid 24 slowly fills each layer of pore plate from a low liquid level, and in the whole process, the liquid level is ensured to stably rise, and then the liquid sequentially flows through the flow stabilizer 12, the ultrasonic flowmeter 3, the DN50 glass window 2 and the first water outlet 17.

Step 2, the relative dielectric constant ε of the fluid inside the sensor, i.e. inside the insulating tube wall 25₁Relative dielectric constant of air ε₂The volume of fluid in the insulating tube wall 25 is V1, the volume of air in the insulating tube wall 25 is V2, and the equivalent relative permittivity ε

ε＝(V₁/V)·ε₁+(V₂/V)·ε₂ (1)

ε＝[(V-V₂)]·_ε1+(V₂/V)·ε₂＝(V₂/V)·(ε₂-ε₁) (2)

Where V is the total volume of the two-phase flow:

V＝V₁+V₂ (3)

define the discrete phase concentrations as:

β₂＝V₂/V (4)

the capacitance measurement C can be obtained as:

C＝K·ε＝K·f(V₂/V)＝K·f(β₂) (5)

where K is a coefficient, K is related to the electrical properties of the air and liquid 24, and the structural properties of the insulating tube wall 25, etc.

When the liquid level heights are different, the cross-sectional areas of the liquid 24 in the tubes are different, the volumes of the liquid 24 in the tubes are different, the equivalent relative dielectric constants of the two substances are different, and the capacitance value between the two electrode plates is changed. The capacitance value and the liquid level height in the insulating tube are related through the above formula.

And establishing a relation between the capacitance and the liquid level to measure the capacitance values of the non-full pipe flowing liquid 24 at different heights, so as to realize the measurement of the liquid level parameters of the non-full pipe electromagnetic flowmeter.

When the tube is full, the induced potential E of the sensor is as follows:

in the formula, B is magnetic induction intensity;

is the average flow rate of the liquid 24; d is the effective measured pipe diameter, D is the inner diameter of the insulating pipe wall 25 when full.

D in formula (1) is related to the liquid level h when the liquid level is low.

Actual flow rate of fluid flowing through the tube:

wherein Q is the actual flow rate in the insulating tube wall 25; a is the cross-sectional area of the liquid 24 flowing through the insulating tube wall 20;

is the average flow rate of the liquid 24

Wherein h is the height of the liquid surface and D is the inner diameter of the insulating tube wall 25

As shown in fig. 3, the electromagnetic flowmeter of the standard meter adopts a capacitive electrode. The utility model discloses a capacitanc electromagnetic flowmeter measures liquid level parameter is according to the velocity of flow signal of weight function under to different liquid levels and calculates. Between the measuring tube and the lining, 4 pairs of capacitor plates are arranged, the conductive liquid 24 flowing in the tube and the measuring tube lining serving as the medium of the capacitor. When the height of the liquid 24 flowing through the insulating tube wall 25 changes, the angle of the equivalent capacitance between the plate and the liquid 24 also changes, and the capacitance value between the capacitance electrodes 23 also changes. The height of the liquid level determines the capacitance between the two plates of the capacitor. To calculate the liquid level versus capacitance, a calculation model was constructed as shown in FIG. 7. The capacitive electrodes 23 are numbered with 4 pairs: 1, 1'; 2, 2'; 3, 3'; 4,4'. The relationship between the geometric quantities can be derived from fig. 7:

d＝R(cosβ-cosα) (9)

a＝R(sinα-sin) (10)

where R is the radius of the inner wall of the insulating tube wall 20.

The capacitance value C of the symmetrical arc column plate capacitor per unit length can be obtained through the geometrical relation (9-10):

in the formula, epsilon₀Is the relative dielectric constant.

Therefore, when the liquid level h is different, α and β change, the value between the capacitance electrodes 23 changes (equation (6)), and at this time, the capacitance value measured between the two capacitance electrodes 23 also changes, so that a functional relationship between the capacitance value C between the electrode plates and the liquid level height h flowing through the non-full insulating tube wall 20 is established, the capacitance value is measured, the liquid level height h of the liquid 24 in the insulating tube wall 25 is calculated through the capacitance value C, and the flow Q1 of the liquid 24 in the insulating tube wall 25 is calculated through the liquid level height h of the liquid 24 in the insulating tube wall 25.

Step 3, measuring the flow rate Q2 of the liquid 24 in the pipeline 20 for a period of time by using a weighing method flow measuring mechanism; when the unstable liquid flow measuring device starts to work, the liquid level can be observed through the DN50 glass window 2 in FIG. 2, and the liquid level switch is triggered to be started, and the liquid level height is recorded through the control system in FIG. 3. When the liquid 24 reaches a certain height, i.e. the liquid level exceeds 50%, the reading Q3 of the ultrasonic flow meter 3 can be compared with the reading Q1 of the standard meter, and the reading of the standard meter is calibrated after the comparison.

When the device fails, for example, metering cannot be achieved or the liquid 24 does not achieve system internal circulation, the control system cannot receive the capacitance value, and the electromagnetic flowmeter of the standard meter in fig. 3 sends out an alarm signal and is reminded through the LED.

The measurement is finished. The measured data can be displayed by a display terminal (as shown in fig. 3), and data transmission and sharing with other devices can be realized through the communication port.

The error of the existing non-full pipe flow device in China is about 15%, and the measured data and the actual yield of the experimental device are shown in the following table under the condition of continuous working for one day. The following table shows that the measurement precision is greatly improved when the comparison error is about 5%;

actual flow (m)³)	Measuring flow (m)³)	Error (%)
			27.34	25.97	5.01
28.56	27.27	4.59
			25.61	24.37	4.92
25.69	24.33	5.08
			26.65	23.60	4.26
24.37	23.14	5.04
			22.34	21.21	5.06

Claims

1. A device for measuring unstable liquid flow in a closed pipeline is characterized by comprising a pipeline, wherein a water inlet and a first water outlet are respectively arranged at two ends of the pipeline; the pipeline is also provided with a standard meter electromagnetic flowmeter; a flow stabilizer is arranged between the standard meter electromagnetic flowmeter and the first water outlet; an ultrasonic flowmeter is arranged between the flow stabilizer and the first water outlet; a glass window is arranged between the ultrasonic flowmeter and the first water outlet.

2. The device for measuring the unstable liquid flow in the closed pipeline according to claim 1, wherein four pairs of capacitive electrodes are laid on the upper and lower sides of the insulating pipe wall of the electromagnetic flowmeter of the standard meter, and are uniformly distributed around the insulating pipe wall; any one of the capacitor electrodes is arc-shaped, the central opening angle of any one of the capacitor electrodes is 40 degrees, and the gaps between any two adjacent capacitor electrodes are equal; the four continuous capacitance electrodes are positive plates, the four capacitance electrodes opposite to the positive plates are negative plates, and the positive plates and the negative plates are respectively positioned on the upper side and the lower side of the insulating pipe wall; and a shielding cover is arranged outside the circular ring formed by the capacitor electrodes.

3. The device for measuring unstable liquid flow in a closed pipeline according to claim 2, wherein the flow stabilizer comprises a first water tank, a water inlet pipe is arranged at the bottom of the first water tank, the water inlet pipe comprises a vertical pipe, the bottom end of the vertical pipe is communicated with the pipeline at one side of the first water tank, which is close to the electromagnetic flowmeter of the standard meter, and the top end of the vertical pipe is connected with a bent pipe; a liquid inlet is formed in one end, away from the vertical pipe, of the bent pipe and is positioned at the bottom of the first water tank; a liquid outlet is arranged above the liquid inlet and is communicated with a pipeline at one side of the first water tank, which is far away from the electromagnetic flowmeter of the standard meter; a plurality of throttle orifice plates are arranged in the first water tank, and through holes which are uniformly distributed are formed in any throttle orifice plate; the throttling orifice plate comprises horizontal plates arranged in parallel with the bottom surface of the first water tank, and any horizontal plate is hermetically connected with the inner side wall of the first water tank; the throttling orifice plate further comprises vertical plates which are perpendicular to the horizontal plates, any vertical plate is hermetically connected with the bottom end and the side wall of the first water tank, and the vertical plates comprise transverse plates and longitudinal plates which are arranged in a crossed mode; and a breather valve is arranged at the top end of the first water tank.

4. A device for measuring unstable liquid flow in an enclosed conduit according to claim 3, wherein said ultrasonic flow meter is clamped to the conduit; the glass window is transparent tubulose, the both ends of glass window all communicate with the pipeline, be provided with the liquid level scale on the glass window, be provided with capacitanc liquid level switch in the glass window.

5. The device for measuring the unstable liquid flow in the closed pipeline according to claim 4, wherein an excitation system of the electromagnetic flowmeter of the standard meter is low-frequency square wave excitation; and a filter circuit is arranged in the electromagnetic flowmeter of the standard meter.

6. The device for measuring the unstable liquid flow in the closed pipeline according to claim 5, wherein a control system is arranged in the electromagnetic flowmeter of the standard meter, and the control system is connected with an LED warning lamp.