A flat flow channel with strip grid and flow meter system
By laying strip grilles in the flat flow path of the ultrasonic flowmeter, the signal reflection and superposition problems are solved, the metering accuracy and performance are improved, and more efficient gas flow measurement is achieved.
Patent Information
- Application Number
- CN202210891156.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-27
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2042-07-27
AI Technical Summary
Existing ultrasonic flowmeters have signal reflection and superposition problems in flat runners, resulting in reduced metrological accuracy and limiting their application range.
A flat runner with a strip grille is designed. By laying a strip grille on the upper and lower inner walls of the runner, the height of the strip grille is 1/4 of the size of the ultrasonic sensor's radiation surface, and is used to block the reflected signal. Reduce signal superposition and rectify ultrasonic signals to ensure that the signal propagates effectively along the straight path.
It effectively improves the reflection and superposition of ultrasonic signals in the flat flow channel, improves the metering performance of the flowmeter, enhances the metering accuracy, and reduces the impact of eddy current on the signal.
Smart Images
Figure CN115200657B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of metering instruments, and in particular to a flat flow channel with a strip grid and a flow meter system. Background Art
[0002] As people pay more and more attention to the environment, natural gas as a clean and environmentally friendly green energy has received more and more attention and application, and the natural gas industry will develop rapidly in the future. In order to meet the development needs of the natural gas industry, especially the development needs of gas companies for natural gas metering and pipeline distribution management, under the background of the development of information technology, ultrasonic gas flow meters have gradually played an increasingly important role in natural gas metering and distribution management.
[0003] At present, the flow meters used in natural gas metering and distribution management in China are mainly Roots meters and turbine meters. Both of these metering instruments are mechanical metering instruments and are difficult to get rid of the inherent weaknesses of mechanical meters. For example, they have high requirements on the quality of natural gas, are prone to getting stuck, require frequent maintenance and have high maintenance costs. At the same time, as the diameter of the natural gas transmission pipeline increases, the size, weight and price of the two mechanical metering instruments will increase significantly. These weaknesses have seriously restricted the development of natural gas metering and pipeline distribution management towards the direction of "precision, stability, intelligence and efficiency".
[0004] In order to overcome the shortcomings of mechanical metering instruments, ultrasonic flow meters have appeared in the prior art. The current flow meter flow channel design is mainly circular in cross section, and there are also designs of flat flow channels with rectangular cross sections. When the flow area is constant, compared with the circular flow channel, the flat flow channel has a smaller fixed size, which can limit the size of large eddies; at the same time, when the flow rate is constant, the Reynolds coefficient of the flattened flow channel fluid is higher and it is easier to enter the turbulent area. Therefore, the flat flow channel is conducive to the stability of the flow state.
[0005] For example, a Chinese patent document with publication number CN105043474A discloses a new flow channel structure for an ultrasonic flow meter, including a measuring flow channel body and two ultrasonic transducers. The measuring flow channel body is a rectangular parallelepiped, and the two ultrasonic transducers are simultaneously arranged on the front side or the rear side of the measuring flow channel body in the horizontal direction.
[0006] The Chinese patent document with publication number CN110285861A discloses an ultrasonic flowmeter, which includes a fluid chamber, an ultrasonic sensor, and a data acquisition and processing device; the fluid chamber is a through-going long tube, and the two ends of the tube are compressed and deformed from a circular tube toward the center of the tube to form a rectangular tube; the ultrasonic sensor is arranged on the side wall of the rectangular tube in the fluid chamber, and is data-connected to the data acquisition and processing device.
[0007] However, due to the problems of signal reflection and superposition of ultrasonic signals in flat flow channels, flat flow channels suffer from problems such as signal attenuation and distortion in actual applications, which limits their scope of application. Summary of the invention
[0008] The present invention provides a flat flow channel with a strip grid, which can effectively solve the reflection and superposition of ultrasonic signals in the flat flow channel, and helps the flow meter system to achieve accurate measurement of gas flow.
[0009] A flat flow channel with a strip grid, wherein the cross section of the flat flow channel is a rectangle, and the length L of the cross section is greater than the height H; an ultrasonic sensor is arranged at the center of the two side walls in the upper and lower directions, respectively, the axes of the two ultrasonic sensors are on the same straight line, and the angle between the axes and the flow direction of the flat flow channel is Φ;
[0010] The flat flow channel is provided with at least one strip grid on the upper and lower inner wall surfaces along the flow direction, and the strip grid is arranged at a distance from the side wall. The position of the strip grid, the corresponding height h of the strip grid is D / 4n, n = 1, 2, 3 ..., D is the effective radiation surface size of the ultrasonic sensor. The present invention can effectively improve the attenuation and distortion problems of ultrasonic signals in conventional flat flow channels due to signal reflection and superposition; at the same time, the flat flow channel has a small size, which can limit the size of the eddy current in the flow channel to reduce the influence of the eddy current on the ultrasonic signal; in addition, the strip grid also has a rectifying effect.
[0011] Preferably, the ratio of the length L to the height H of the cross section is not less than 3.
[0012] Theoretically, Φ≠90° is sufficient. In practical applications, preferably, the angle Φ between the axes of the two ultrasonic sensors and the flow direction of the flat flow channel is 30° to 60°.
[0013] In practical applications, preferably, the flat flow channel has A plurality of strip grids are arranged at even intervals.
[0014] Under the condition that the ultrasonic signal can be effectively transmitted along a straight path between the two sensors, the height h of the strip grid is D / 4.
[0015] Preferably, the thickness t of the strip grid is less than half of the ultrasonic wavelength λ emitted by the ultrasonic sensor, so as to prevent the ultrasonic signal from being effectively reflected at the top of the strip grid and reaching the ultrasonic sensor at the receiving end.
[0016] Alternatively, the top of the strip grid is designed to be other shapes that can prevent the ultrasonic signal from being reflected by the top of the grid and reaching the sensor at the receiving end.
[0017] Preferably, the length of the strip grid runs through the entire flat channel. In practical applications, the length does not necessarily have to run through the entire channel, as long as it can effectively block the reflected ultrasonic signal to prevent it from reaching the receiving sensor.
[0018] The strip grid may be in a rectangular shape, or may be in other shapes such as a zigzag shape, a wavy shape, etc., as long as the reflected ultrasonic signal can be effectively shielded to prevent it from reaching the receiving sensor.
[0019] Sufficient gaps should be left between the strip grids on the upper and lower inner walls for ultrasonic signal propagation to avoid affecting the effective propagation of ultrasonic signals along a straight path. Preferably, the spacing between the strip grids arranged on the upper and lower inner walls of the flat flow channel is not less than 0.6D, that is, H-2h≥0.6D.
[0020] The present invention also provides a flow meter system, including a measuring flow channel, wherein the measuring flow channel is composed of the flat flow channel with the above-mentioned strip grid; wherein the measuring flow channel is composed of one flat flow channel, or is composed of a plurality of flat flow channels superimposed on each other.
[0021] The flow meter system also includes a temperature sensor and a pressure sensor, which are used to measure the gas temperature and pressure, and then used to realize the conversion from operating flow to standard flow.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] The present invention utilizes a carefully designed strip grid to shield the ultrasonic signals reaching the upper and lower walls of the flat pipe, effectively improving the reflection and superposition effects of the ultrasonic signals in the conventional flat pipe. At the same time, with the help of the rectifying effect of the strip grid, the ultrasonic flow meter using the flat flow channel can achieve higher metering performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is a schematic diagram of the reflection and superposition principle of ultrasonic signals in a flat pipe;
[0025] Figure 2 This is a schematic diagram to illustrate the principle of ultrasonic superposition;
[0026] Figure 3 Schematic diagram of the strip grid design to eliminate primary reflection;
[0027] Figure 4 Schematic diagram of the strip grid design to eliminate double reflection;
[0028] Figure 5 Schematic diagram of the strip grid design to eliminate triple reflection;
[0029] Figure 6Schematic diagram of the strip grid design to eliminate four reflections;
[0030] Figure 7 The schematic diagram of the conversion between the grid spacing derived when Φ is 90° and the grid spacing in actual application (Φ≠90°);
[0031] Figure 8 It is a schematic diagram of a flat flow channel with strip grid and its parameters;
[0032] Fig. 9 It is a schematic diagram of a strip grid;
[0033] Fig.10 Schematic diagram of the superposition of three flat flow channels using strip grids. DETAILED DESCRIPTION
[0034] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.
[0035] As a theoretical basis, the principle of using ultrasound to measure gas flow is briefly described as follows: The principle of using ultrasound to measure gas flow is the ultrasonic time difference method, which uses the (downstream) acceleration and (backstream) deceleration of the ultrasonic signal by the fluid, measures the propagation time of the ultrasonic wave in the downstream and backstream directions respectively, and then uses the difference between the two to calculate the medium flow rate, and finally obtains the medium flow rate. In other words, how to accurately identify the ultrasonic signal and accurately calculate the ultrasonic signal propagation time is the key to whether it can be accurately measured. In other words, all factors that affect the stable propagation of the ultrasonic signal will affect the measurement accuracy.
[0036] First combine Figure 1 Introducing the reflection and superposition problems of ultrasonic signals in conventional flat flow channels, in order to simplify the explanation, the change in longitudinal distance caused by the angle Φ between the ultrasonic sensor axis and the longitudinal axis of the flow channel is not considered in the principle description, that is, it is assumed that Φ = 90°. Figure 1 As shown, the cross-section of the flat pipe is a rectangle with a length of L and a height of H. The sensors SA and SB are located in the middle of the side wall (up and down direction) with a beam angle of α. In the figure, SA is an ultrasonic transmitting sensor and SB is an ultrasonic receiving sensor. In practice, both sensors are integrated transceiver sensors. Under ideal conditions, the ultrasonic wave emitted by SA has a small enough beam angle α, and the ultrasonic wave directly reaches the receiving sensor SB along the ideal path shown in the figure (the straight line path shown by the solid line in the figure). However, when α≥β (tanβ≥H / L), a part of the ultrasonic beam emitted by the sensor SA will be reflected on the upper and lower walls of the pipe, and will reach the receiving end sensor SB after being reflected along the reflection path shown in the figure (the broken line path shown by the dotted line in the figure).
[0037] like Figure 2 As shown, it is assumed that the ultrasonic signal reaching the receiving sensor SB along the ideal path shown in the figure is:
[0038] f1(t)=Asinωt
[0039] Then along Figure 1 The ultrasonic signal reaching the receiving sensor SB through the reflected path shown is:
[0040] f2(t)=Bsin[ω(t+Δt)]
[0041] Among them, Δt is the corresponding increase in propagation delay after the reflection path length increases, which is:
[0042]
[0043] According to the superposition principle of mechanical waves, the signal received by the receiving sensor SB should be:
[0044] f(t)=f1(t)+f2(t)=Asinωt+Bsin[ω(t+Δt)]
[0045] It can be seen that compared with the original ultrasonic signal f1(t) that arrives at the receiving sensor SB along the ideal path, the reflected and superimposed ultrasonic signal f(t) received by the receiving sensor SB has changed in amplitude and phase, which will have an adverse effect on the calculation of time.
[0046] In particular, in practical applications, due to the disturbance of airflow, the propagation paths mentioned above will change randomly under the disturbance of airflow. That is to say, the actual signal superposition situation at the receiving sensor SB end is more complex and random than the theoretically derived value, which also increases the difficulty of accurate timing.
[0047] In this regard, the present invention proposes a flat flow channel with a strip grid to weaken / eliminate the superposition of the reflected wave at the receiving sensor SB and the ultrasonic signal propagating along the ideal path. The design principle is described below.
[0048] like Figure 3 As shown, a strip grid is added at the L / 2 position of the upper and lower walls, with a height of h. The beam angle of the ultrasonic sensor is α and α≥β(tanβ≥H / L) (this will be used as the default condition later). The height h of the strip grid is calculated here, and it is required to block the primary reflection signal and prevent the primary reflection signal from reaching the receiving sensor SB.
[0049] First, the reflected wave path ( Figure 3Assume that the horizontal distance from the reflection point a to the transmitting sensor is x, and the horizontal distance from the reflection point a to the receiving sensor SB is Lx. Then:
[0050]
[0051]
[0052]
[0053] Combining equations ⑴, ⑵, and ⑶, we can get:
[0054] That is: when the strip grid height meets When , the primary reflected wave is either blocked by the strip grid or reaches the position below SB after reflection, and will not be able to directly reach the receiving sensor SB and superimpose with the original direct beam.
[0055] Similarly, when the reflected wave path is close to the receiving sensor SB ( Figure 3 The dotted path with point b as the reflection point) is similarly the case when the strip grid height satisfies When , the primary reflected wave is either blocked by the strip grid or reaches the position above SB after reflection, and will not be able to directly reach the receiving sensor SB and superimpose with the original direct beam.
[0056] In summary, when the height of the strip grid at the L / 2 position on the upper and lower walls meets When , the primary reflected wave will not be able to directly reach the receiving sensor SB and will be superimposed with the original direct beam.
[0057] like Figure 4 When the sensor beam angle α is large enough or the pipe is flat enough, the ultrasonic signal will reach the receiving end sensor SB after secondary reflection. Similarly, a strip grid is added at the position L / 4 from the upper and lower wall edges, and the grid height is h1.
[0058] First, the reflection point is on the reflected wave path on the left side of the grid ( Figure 4 Assume that the horizontal distance from the reflection point a to the transmitting sensor is x, and the horizontal distances between the first reflection point and the second reflection point are y, then the horizontal distance from the second reflection point to the receiving sensor SB is z. Then:
[0059]
[0060] y·tanγ=H···Formula 5
[0061]
[0062] x+y+z=L···Formula 7
[0063] Combining equations (4), (5), (6), and (7) we can obtain:
[0064]
[0065]
[0066] Then the beam with point a as the reflection point is at the position of the grid at the position L / 4 from the upper and lower wall edges, and the height from the wall where the strip grid is located is h * , then:
[0067]
[0068] That is: when the height of the strip grid at the position L / 4 from the upper and lower wall edges meets When , the ultrasonic beam reflected by the reflection point a will be blocked by the strip grid or can only reach the area above the receiving sensor, and will not be able to directly reach the receiving sensor SB and form an overlap with the original direct beam.
[0069] Similarly, when the reflection point of the reflection path is on the right side of the strip grid ( Figure 4 When the dotted line path with point b as the reflection point is When the secondary reflected wave is either blocked by the strip grid or reaches the position below SB after reflection, it will not be able to directly reach the receiving sensor SB and form a superposition with the original direct beam.
[0070] In summary, when the height of the strip grid at the position L / 4 from the upper and lower wall edges meets When , the secondary reflected wave will not be able to directly reach the receiving sensor SB and will be superimposed with the original direct beam.
[0071] Similarly, the following conclusion can be drawn by deducing in sequence: For the possible n (n = 1, 2, 3...) reflected waves, they will be reflected by the upper and lower walls at a horizontal distance of 1 / 2 from the transmitting sensor. The height is not less than The strip grid blocks the light and cannot directly reach the receiving end sensor SB. Figure 5 Schematic diagram of the strip grid design to eliminate triple reflection; Figure 6 Schematic diagram of the strip grid design to eliminate the fourth reflection.
[0072] Considering that in practical applications, all transceiver integrated sensors are used, and considering the actual manufacturing process and the flow constraint effect of the strip grid, on the basis of ensuring that sufficient signal channels are reserved, it is preferred to use For uniform spacing, the height should not be less than The strip grid can effectively weaken / eliminate the influence of the signal reflected by the upper and lower walls on the original signal after it reaches the receiving end and is superimposed with the signal along the ideal path.
[0073] In the above derivation, in order to simplify the explanation, the premise assumption is that the angle Φ between the ultrasonic sensor axis and the longitudinal axis of the flow channel is 90°. Theoretically, In practical applications, the preferred range of Φ is (30°, 60°). Therefore, the above conclusion needs to be revised in combination with Φ.
[0074] According to the above derivation, the strip grid spacing derived under the condition of Φ = 90° is It should be corrected to "the distance between two adjacent strip grids along the sensor axis direction". Figure 7 As shown. In practical applications, the optimal spacing of strip grids should be corrected to The corresponding minimum height of the strip grid has nothing to do with Φ and is still
[0075] like Figure 8 As shown, this is a schematic diagram of a flat flow channel designed according to the above design method. Fig. 9 It is a schematic diagram of a strip grid. It should be noted that the top width t of the strip grid should be much smaller than the ultrasonic wavelength to prevent the ultrasonic wave from being effectively reflected at the top of the grid; or the top of the strip grid can be designed into other shapes that cannot effectively reflect the ultrasonic signal to the receiving end.
[0076] In addition, please note that as the number of reflections increases, the signal reaching the receiving end after reflection will become weaker. In actual design, the shielding depth n (n = 1, 2, 3..., indicating that the ultrasonic signal reaches the receiving end after n reflections) can be set as needed, as long as the reflection superposition of the signal is controlled within an acceptable range. If n is too large, the strip grid spacing will be small enough. When the strip grid spacing is close to the ultrasonic wavelength or even smaller than the ultrasonic wavelength, the shielding effect of the strip grid is weakened or even ineffective.
[0077] Secondly, the length of the strip grid runs through the entire flow channel, which not only solves the problems of signal reflection and superposition but also plays a role in stabilizing the flow state. However, its length does not have to run through the entire flow channel, as long as it can effectively block the reflected ultrasonic signal from reaching the receiving sensor.
[0078] Furthermore, the strip grid is preferably in the shape of a straight rectangular strip, but is not limited to this state, and may also be in other shapes such as a zigzag shape, a wavy shape, etc., as long as it can effectively block the reflected ultrasonic signal from reaching the receiving sensor.
[0079] Furthermore, in practical applications, the specific position of the strip grille can actually be adjusted accordingly as needed. For example, the depth of the strip grille can be appropriately increased while ensuring that the shielding effect is not weakened, in exchange for fine-tuning the position of the strip grille; secondly, when the weakening of the shielding effect caused by fine-tuning the grille position is not sufficient to substantially affect the shielding effect (that is, the attenuation of the shielding effect is within an acceptable range), the position of the strip grille can also be fine-tuned. In short, as long as the shielding effect of the reflected signal required in practical applications can be met.
[0080] The flat flow channel designed according to the above flat flow channel design method is applied to the flow meter system, and the number of flow channels can be one or more, so as to realize the working flow measurement of the gas medium;
[0081] The flow meter system also includes the collection of medium temperature and pressure to complete the conversion of gas operating flow to standard flow.
[0082] like Fig.10 The figure shows a schematic diagram of three flat flow channels using strip grids. It should be noted that the axes of the three sensor groups in the figure are parallel, but this is not limited to the actual application, and the angles between the axes of the three sensor groups and the longitudinal axis of the flow channel are not necessarily consistent. In addition, the same flow meter can also use a mixture of flat flow channels of different sizes designed according to the above method.
[0083] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A flat flow channel with a strip grid, characterized in that: The cross section of the flat flow channel is rectangular, and the length L of the cross section is greater than the height H. An ultrasonic sensor is arranged at the center of the two side walls in the upper and lower directions of each side wall of the flat flow channel. The axes of the two ultrasonic sensors are on the same straight line, and the angle between the axes and the flow direction of the flat flow channel is Φ. The flat flow channel is provided with at least one strip grid on the upper and lower inner wall surfaces along the flow direction, and the strip grid is arranged at a distance from the side wall. The corresponding strip grid height h is D / 4n, n=1,2,3..., D is the effective radiation surface size of the ultrasonic sensor.
2. The flat flow channel with strip grid according to claim 1, characterized in that: The ratio of the length L to the height H of the cross section is not less than 3.
3. The flat flow channel with strip grid according to claim 1, characterized in that: The included angle Φ between the axes of the two ultrasonic sensors and the flow direction of the flat flow channel is 30° to 60°.
4. The flat flow channel with strip grid according to claim 1, characterized in that: The flat flow channel is provided with A plurality of strip grids are arranged at even intervals.
5. The flat flow channel with strip grid according to claim 1, characterized in that: The height h of the strip grid is D / 4.
6. The flat flow channel with strip grid according to claim 1, characterized in that: The thickness t of the strip grid is less than half of the ultrasonic wavelength λ emitted by the ultrasonic sensor, so as to prevent the ultrasonic signal from being effectively reflected at the top of the strip grid and reaching the ultrasonic sensor at the receiving end.
7. The flat flow channel with strip grid according to claim 1, characterized in that: The length of the strip grid runs through the entire flat flow channel, and its shape is rectangular, folded line or wavy.
8. The flat flow channel with strip grid according to claim 1, characterized in that: The interval between the strip grids arranged on the upper and lower inner wall surfaces of the flat flow channel is not less than 0.6D, that is, H-2h≥0.6D.
9. A flow meter system, comprising a measuring flow channel, characterized in that: The measuring flow channel is composed of a flat flow channel with a striped grid as described in any one of claims 1 to 8; wherein the measuring flow channel is composed of one flat flow channel, or is composed of a plurality of flat flow channels stacked together.
10. The flow meter system according to claim 9, characterized in that The flow meter system also includes a temperature sensor and a pressure sensor for completing the conversion of the gas operating flow rate to the standard flow rate.