Method for measuring minimum liquid flow

Abstract

The invention discloses a minimum liquid flow measuring method. The method comprises the steps that liquid is injected into a capillary receiving tube; the liquid outlet pipe is connected with a detected instrument, liquid is continuously injected into the liquid outlet pipe through the detected instrument, micro-convex liquid is formed at the liquid outlet, and the micro-convex liquid does not make contact with the capillary receiving pipe; the evaporation rate E1 of the liquid in the capillary receiving tube is obtained based on the reading of the balance in the detected time period T1; the evaporation rate E2 of the micro-convex liquid formed at the liquid outlet of the liquid outlet pipe is obtained based on the evaporation rate E1; acquiring a pipeline leakage rate Qleak between the detected instrument and the liquid outlet pipe; and the flow Q of the detected instrument is obtained based on the morphological relation between the evaporation rate E2 and the micro-convex liquid in the detected time period T1 and the pipeline leakage rate Qleak. According to the method, firstly, dynamic balance is formed by utilizing the extrusion amount and evaporation amount of the micro-convex liquid under the extremely small flow, then the evaporation rate at the liquid receiving opening of the capillary receiving tube in the near space is taken as a reference, and finally, the mass loss of the liquid collecting container is weighed by the balance, so that a real-time flow value is provided.

Description

Technical Field

[0001] This invention relates to the field of flow measurement technology, and more specifically, to a method for measuring extremely small liquid flow rates. Background Technology

[0002] Chinese patent CN118518174A discloses a flow measurement device and method based on the mass method. This device uses a balance to obtain the mass of the liquid and then converts that mass into flow rate to measure minute flow rates, with a lower limit of 100 μg / min. The measurement process involves liquid being extruded from an outlet pipe, forming micro-convex liquids, which are then collected by a capillary receiver. Therefore, the liquid flow rate is critical. If the flow rate is too low, much less than 100 μg / min, the volume of the micro-convex liquid extruded from the outlet pipe takes a considerable amount of time to reach the level required for absorption by the capillary receiver. This results in prolonged exposure of the micro-convex liquid, significantly increasing evaporation and significantly increasing the interval between liquid absorption by the capillary receiver, making measurement difficult. Therefore, there is an urgent need for a method capable of measuring extremely small liquid flow rates. Summary of the Invention

[0003] The main objective of this invention is to provide a method for measuring extremely small liquid flow rates, so as to solve the problem of difficulty in accurately measuring extremely small liquid flow rates in related technologies.

[0004] To achieve the above objectives, the present invention provides a method for measuring extremely small liquid flow rates, comprising: Inject liquid into the capillary receiving tube; Connect the liquid outlet tube to the instrument under test, continuously inject liquid into the liquid outlet tube through the instrument under test to form a micro-convex liquid at the outlet, and ensure that the micro-convex liquid does not come into contact with the capillary receiving tube. The evaporation rate E1 of the liquid in the capillary receiving tube is obtained based on the balance reading during the tested time period T1. The evaporation rate E2 of the micro-convex liquid formed at the outlet of the liquid outlet pipe is obtained based on the evaporation rate E1. Obtain the leakage Q of the pipeline between the instrument under test and the outlet pipe. leak ; Based on the relationship between the evaporation rate E2 and the morphology of the microconvex liquid during the tested time period T1, and the pipeline leakage Q leak Obtain the flow rate Q of the instrument under test.

[0005] With the above setup, the liquid receiving port of the capillary receiving tube and the liquid outlet of the outlet tube are located in the same environment. Therefore, the environment has the same effect on the evaporation rate of the liquid at the receiving port and the micro-convex liquid at the outlet. In this environment, since the micro-convex liquid remains in a state of not contacting the capillary receiving tube, the instrument under test continuously delivers a small flow of liquid to the outlet tube during the tested time period T1. At the same time, the micro-convex liquid formed at the outlet and the liquid in the liquid receiving port of the capillary receiving tube continue to evaporate. Since the capillary receiving tube is located on a balance, the evaporation rate E1 of the liquid in the capillary receiving tube can be determined by the balance reading during the tested time period T1. Because the liquid receiving port of the capillary receiving tube and the liquid outlet of the outlet tube are in the same environment, there is a certain relationship between the evaporation rate E1 and the evaporation rate E2 of the micro-convex liquid formed at the outlet. This relationship can be determined based on the evaporation area of ​​the two, so the evaporation rate E2 can be derived from the evaporation rate E1.

[0006] Because the instrument under test continuously supplies a small flow of liquid to the outlet pipe during the tested time period T1, and the micro-convex liquid is continuously evaporating, the relationship between the liquid flow rate continuously supplied by the instrument under test to the outlet pipe and the evaporation rate E2 of the micro-convex liquid will affect the morphology of the micro-convex liquid. Therefore, the flow rate in the outlet pipe can be deduced by reverse calculation based on the relationship between the evaporation rate E2 and the morphology of the micro-convex liquid during the tested time period T1. This can then be combined with the pipeline leakage Q between the instrument under test and the outlet pipe. leak The flow rate Q of the instrument under test is obtained.

[0007] This invention utilizes the physical property that liquid evaporation rate is strongly correlated with exposure area and environmental parameters under the same environmental conditions. The evaporation rate E1 of the liquid in the capillary receiving tube is used to indirectly deduce the evaporation rate E2 of the micro-convex liquid, avoiding the technical difficulty of directly measuring the evaporation rate of a very small volume of micro-convex liquid. Furthermore, based on the evaporation rate E2 and the morphological relationship of the micro-convex liquid, as well as the pipeline leakage Q... leak The flow rate Q of the instrument under test is derived, enabling flow rate measurement up to 1 μg / min, significantly improving the flow rate measurement range. Furthermore, the measurement process does not require consideration of the liquid receiving time interval of the capillary receiving tube, thus significantly improving measurement efficiency.

[0008] Optionally, liquid is injected into the capillary receiving tube, including: Liquid is injected into the capillary receiving tube, and the liquid evaporation surface is made flush with the liquid receiving port of the capillary receiving tube.

[0009] With the above settings, at the beginning of the measurement, the liquid evaporation surface inside the capillary receiving tube is flush with the liquid receiving port. The liquid receiving port is closer to the external environment of the capillary receiving tube than the internal tube section of the capillary receiving tube, so that the liquid evaporation surface is directly affected by the external environment and evaporates. As a result, the evaporation rate E1 of the liquid inside the capillary receiving tube can be very close to the evaporation rate E2 of the micro-convex liquid, thereby improving the accuracy of the flow rate Q measurement of the instrument under test.

[0010] Optionally, the evaporation rate E1 of the liquid in the capillary receiving tube is obtained based on the balance reading during the tested time period, including: The mass loss rate M is obtained based on the balance readings within the expected time period T2. S ; The mass loss rate M is obtained based on the balance readings within the expected time period T3. L The expected time period T2 and the expected time period T3 are sequential within the inspected time period T1, and the ratio K1 of the expected time period T2 to the expected time period T3 is 0.1-0.5; The evaporation rate E1 = mass loss rate M S - Mass loss rate M L .

[0011] The liquid inside the capillary receiver tube experiences mass loss due to evaporation. Evaporation occurs at the liquid receiving port of the capillary receiver tube and other gaps in the measuring device. Since these gaps are relatively small, the mass loss at these locations is less than that at the liquid receiving port. In the short term, the mass loss rate at the liquid receiving port is much higher than that at the gaps, thus the proportion of the mass loss rate at the liquid receiving port to the total mass loss rate is relatively high. However, as time progresses, the liquid evaporation surface within the capillary receiver tube gradually shrinks into the tube, and the evaporation rate of the liquid evaporation surface decreases significantly. This means the mass loss rate through the liquid receiving port decreases, while the mass loss rate at other gap locations remains constant. Therefore, the proportion of the mass loss rate at the liquid receiving port to the total mass loss rate is relatively low. Thus, in this embodiment, the short-term (expected time period T2) mass loss rate M is used... S -Long-term (expected time period T3) quality loss rate M L The evaporation rate E1 at the liquid receiving port is obtained, and the evaporation rate E2 of the microconvex liquid is derived based on this, making the measurement accurate and efficient.

[0012] Optionally, obtaining the evaporation rate E2 of the micro-convex liquid formed at the outlet of the liquid outlet pipe based on the evaporation rate E1 includes: Obtain the liquid evaporation area A1 of the liquid inside the capillary receiving tube; Obtain the surface area A2 of the microconvex liquid; The evaporation rate E2 is obtained using the following formula: ; in, R 1 The inner diameter of the capillary receiving tube. R 2 Let be the radius of the sphere of the slightly convex liquid. h The height of the slightly convex liquid.

[0013] With the above settings, after knowing the evaporation rate E1, the evaporation rate E2 can be determined based on the relationship between the evaporation area of ​​the micro-convex liquid and the liquid evaporation area in the capillary receiving tube, thus enabling the evaporation rate E2 to be obtained quickly and accurately.

[0014] Optionally, based on the relationship between the evaporation rate E2 and the morphology of the micro-convex liquid during the tested time period T1, and the pipeline leakage amount Q leak Obtaining the flow rate Q of the instrument under test includes: The morphological changes of the microconvex liquid were observed during the tested time period T1; If the shape of the microconvex liquid remains constant during the tested time period T1, the flow rate Q of the tested instrument is obtained according to the following formula: Flow rate Q = Evaporation rate E2 + Pipeline leakage Q leak ; If the shape of the micro-convex liquid is not constant during the inspection time period T1, then obtain the rate of change of the surface area A2 of the micro-convex liquid during the inspection time period T1. Based on the rate of change, the evaporation rate correction E3 within the time period T1 under test is obtained, and the flow rate Q of the instrument under test is obtained according to the following formula; Flow rate Q = Evaporation rate E2 + Evaporation rate correction E3 + Pipeline leakage Q leak .

[0015] Based on the above settings, the flow rate Q of the instrument under test is calculated according to the morphological changes of the micro-convex liquid within the tested time period T1. When the morphology of the micro-convex liquid remains constant, it means that the evaporation rate of the micro-convex liquid is equal to the flow rate of the liquid discharged through the outlet of the outlet pipe. Therefore, the flow rate Q = evaporation rate E2 + pipeline leakage Q. leak When the shape of the convex liquid is not constant, it means that the evaporation rate of the convex liquid is not equal to the liquid flow rate discharged through the outlet of the outlet pipe. Therefore, it is necessary to obtain the evaporation rate correction amount E3 within the tested time period T1. Then, the flow rate Q = evaporation rate E2 + evaporation rate correction amount E3 + pipeline leakage Q. leak The morphological changes of the microconvex liquid determine whether to introduce an evaporation rate correction, further improving the accuracy of flow measurement.

[0016] Optionally, the evaporation rate correction E3 is obtained according to the following formula: E3 ; in, R 2 Let be the radius of the sphere of the slightly convex liquid. h The height of the slightly convex liquid. t The time period T1 being inspected R 1 The inner diameter of the capillary receiving tube. The height change rate of the microconvex liquid.

[0017] Optionally, based on the relationship between the evaporation rate E2 and the morphology of the micro-convex liquid during the tested time period T1, and the pipeline leakage amount Q leak Obtaining the flow rate Q of the instrument under test includes: The morphological changes of the microconvex liquid were observed during the tested time period T1; If the shape of the microconvex liquid remains constant during the tested time period T1, the flow rate Q of the tested instrument is obtained according to the following formula: Flow rate Q = Evaporation rate E2 + Pipeline leakage Q leak ; If the shape of the micro-convex liquid is not constant during the time period T1 under inspection, the humidity of the environment where the micro-convex liquid and the liquid receiving port of the capillary receiving tube are located is adjusted to change the evaporation rate of the micro-convex liquid so that the shape of the micro-convex liquid remains constant. Obtain the evaporation rate E of the liquid in the current capillary receiving tube. 10 ; Based on the evaporation rate E 10 Obtain the evaporation rate E of the microconvex liquid. 20 The flow rate Q of the instrument under test is obtained according to the following formula: Flow rate Q = Evaporation rate E 20 + Pipeline leakage Q leak ; With the above settings, when the shape of the micro-convex liquid is not constant, it means that the evaporation rate of the micro-convex liquid is not equal to the liquid flow rate discharged through the outlet of the liquid outlet pipe. Therefore, the evaporation rate of the micro-convex liquid can be adjusted to make its shape constant. The method for adjusting the evaporation rate is to adjust the humidity of the environment where the micro-convex liquid and the liquid receiving port are located. After the evaporation rate is adjusted to the point where the shape of the micro-convex liquid is constant, the liquid evaporation rate E of the liquid receiving port is re-acquired. 10 And based on the evaporation rate E 10 Redetermine the evaporation rate E of the microconvex liquid 20 At this time, the slightly convex liquid has an evaporation rate E 20 The flow rate Q = evaporation rate E² + pipeline leakage Q can maintain a constant state. leakThe evaporation rate is adjusted based on the morphological changes of the slightly convex liquid, and the flow rate is then derived in reverse from the adjusted evaporation rate. This measurement method is simple and can improve the accuracy of flow rate measurement.

[0018] Optionally, during the process of continuously injecting liquid into the outlet tube through the instrument under test and forming a micro-convex liquid at the outlet, the height h of the formed micro-convex liquid is controlled to be less than its spherical radius. R 2 .

[0019] Optionally, the morphological changes of the microconvex liquid are obtained by image recognition of the microconvex liquid using machine time. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention, making other features, objects, and advantages of the invention more apparent. The illustrative embodiments of the invention illustrated in the drawings and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the measuring device according to an embodiment of the present invention; Among them, 1. liquid outlet pipe; 10. liquid outlet; 2. capillary receiving pipe; 20. liquid receiving port; 3. micro-convex liquid; 4. external anti-evaporation cover; 5. internal evaporation cover; 6. evaporation well; 7. balance. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein.

[0023] In this invention, the terms "upper," "lower," "inner," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0024] Furthermore, some of the aforementioned terms, besides indicating direction or positional relationships, may also have other meanings. For example, the term "above" may, in certain circumstances, indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0025] Furthermore, the terms "set up," "equipped with," "connected," and "fixed" should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0026] In addition, the term "multiple" should mean two or more.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] To address related technical problems, a method for measuring extremely small liquid flow rates is proposed. This method utilizes a flow measurement device based on the mass method disclosed in Chinese Patent CN118518174A, such as... Figure 1 As shown, in this measuring device, there is a gap between the liquid outlet 10 of the liquid outlet tube 1 and the liquid receiving port 20 of the capillary receiving tube 2, and both are located within the same external anti-evaporation hood 4, meaning they are in the same environment. The capillary receiving tube 2 can absorb liquid, and when the liquid does not completely fill the capillary receiving tube 2, the liquid will not flow out from the lower end of the capillary receiving tube 2 under the action of tension.

[0029] During the measurement process, a certain amount of liquid is injected into the capillary receiving tube 2, forming a continuous liquid column in the capillary receiving tube 2. The liquid evaporation surface at the upper end of the liquid column is located at or near the liquid receiving port 20 of the capillary receiving tube 2. Connect the liquid outlet tube 1 to the instrument under test, and continuously inject liquid into the liquid outlet tube 1 through the instrument under test to form a micro-convex liquid 3 at the liquid outlet 10, and ensure that the micro-convex liquid 3 does not contact the capillary receiving tube 2. In the measurement method disclosed in CN118518174A, the micro-convex liquid 3 squeezed out by the outlet tube 1 can be sucked into the capillary receiving tube 2. Therefore, when using the measurement device disclosed in CN118518174A, the distance between the outlet tube 1 and the capillary receiving tube 2 can be increased according to the actual measurement requirements so that the micro-convex liquid 3 will never come into contact with the liquid receiving port 20 of the capillary receiving tube 2 within the expected flow range.

[0030] The evaporation rate E1 of the liquid in the capillary receiving tube 2 is obtained based on the reading of the balance 7 during the tested time period T1. During the measurement process, as time progresses, the liquid in the capillary receiving tube 2 evaporates, causing a loss of liquid mass. The reading of the balance 7 decreases, thus the balance 7 can accurately determine the mass loss of the liquid in the capillary receiving tube 2 during the measured time period T1. The evaporation rate E1 of the liquid in the capillary receiving tube 2 can be obtained based on the ratio of the mass loss to the measured time period T1. When the liquid extrusion speed of the outlet tube 1 is extremely slow, the airflow inside the outer anti-evaporation cover 4 is undisturbed and stationary. Therefore, the evaporation rate inside the outer anti-evaporation cover 4 is approximately equal to the evaporation rate E1 at the receiving port of the capillary receiving tube 2.

[0031] The evaporation rate E2 of the micro-convex liquid 3 formed at the outlet 10 of the liquid outlet pipe 1 is obtained based on the evaporation rate E1. During the measurement process, the micro-convex liquid 3 at the outlet 10 continues to evaporate. Since the outlet 10 of the outlet pipe 1 and the liquid receiving port 20 of the capillary receiving tube 2 are located in the same external anti-evaporation cover 4, they are in the same environment. Since the evaporation rate E1 of the liquid in the capillary receiving tube 2 is approximately equal to the evaporation rate in the external anti-evaporation cover 4, it has a certain relationship with the evaporation rate E2 of the micro-convex liquid 3 formed at the outlet 10. Therefore, the evaporation rate E2 of the micro-convex liquid 3 formed at the outlet 10 of the outlet pipe 1 can be determined based on the evaporation rate E1.

[0032] Obtain the leakage Q of the pipeline between the instrument under test and the outlet pipe 1. leak ; For measuring extremely small liquid flow rates, even a tiny amount of liquid leakage at the connection between the instrument under test and the outlet pipe 1 can affect the measurement results. Therefore, it is also necessary to determine the pipe leakage Q between the instrument under test and the outlet pipe 1 during the measurement process. leak Pipeline leakage Q leak The leakage amount Q can be obtained through calibration experiments. For example, in a calibration experiment, a liquid with a known flow rate is injected into the outlet pipe 1 of the instrument under test. The liquid is received at the outlet 10 of the outlet pipe 1, and the flow rate of the received liquid is measured. By comparing the known flow rate with the received flow rate, the pipeline leakage amount Q can be obtained. leak .

[0033] Based on the relationship between the evaporation rate E2 and the morphology of the micro-convex liquid 3 during the tested time period T1, and the pipeline leakage amount Q leak Obtain the flow rate Q of the instrument under test.

[0034] During the tested time period T1, the instrument under test continuously supplies a small flow of liquid to the outlet pipe 1, while the micro-convex liquid 3 is continuously evaporating. The relationship between the liquid flow rate supplied by the instrument under test to the outlet pipe 1 and the evaporation rate E2 of the micro-convex liquid 3 affects the morphology of the micro-convex liquid 3. When the liquid flow rate in the outlet pipe 1 is the same as the evaporation rate E2 of the micro-convex liquid 3, the morphology of the micro-convex liquid 3 remains constant. When the liquid flow rate in the outlet pipe 1 is less than the evaporation rate E2 of the micro-convex liquid 3, the volume of the micro-convex liquid 3 decreases. When the liquid flow rate in the outlet pipe 1 is greater than the evaporation rate E2 of the micro-convex liquid 3, the volume of the micro-convex liquid 3 increases. Therefore, the flow rate in the outlet pipe 1 can be deduced from the relationship between the evaporation rate E2 and the morphology of the micro-convex liquid 3 during the tested time period T1, and then combined with the pipeline leakage Q between the instrument under test and the outlet pipe 1. leak The flow rate Q of the instrument under test is obtained.

[0035] This invention first utilizes the dynamic balance between the extrusion rate and evaporation rate of the micro-convex liquid 3 under extremely low flow rate. Then, it uses the evaporation rate at the liquid receiving port 20 of the capillary receiving tube 2 in the adjacent space as a reference. Finally, it uses a balance 7 to weigh the mass loss of the liquid collection container, thereby providing a real-time flow rate value. It can achieve flow rate measurement of 1 μg / min, significantly improving the flow rate measurement range and accuracy. Furthermore, it does not require consideration of the liquid receiving time interval of the capillary receiving tube 2 during the measurement process, significantly improving the measurement efficiency.

[0036] In one embodiment, injecting liquid into the capillary receiving tube 2 includes: Liquid is injected into the capillary receiving tube 2, and the liquid evaporation surface is made flush with the liquid receiving port 20 of the capillary receiving tube 2.

[0037] With the above settings, at the beginning of the measurement, the liquid evaporation surface inside the capillary receiving tube 2 is flush with the liquid receiving port 20. The liquid receiving port 20 is closer to the external environment of the capillary receiving tube 2 than the internal tube section of the capillary receiving tube 2, so that the liquid evaporation surface is directly affected by the external environment and evaporates. As a result, the evaporation rate E1 of the liquid inside the capillary receiving tube 2 can be very close to the evaporation rate E2 of the micro-convex liquid 3, thereby improving the accuracy of the flow rate Q measurement of the instrument under test.

[0038] In one embodiment, obtaining the evaporation rate E1 of the liquid in the capillary receiving tube 2 based on the reading of the balance 7 during the tested time period includes: The mass loss rate M is obtained based on the readings of balance 7 within the expected time period T2. S ; The mass loss rate M is obtained based on the readings of balance 7 within the expected time period T3. LThe expected time period T2 and the expected time period T3 are sequential within the inspected time period T1, and the ratio K1 of the expected time period T2 to the expected time period T3 is 0.1-0.5; The evaporation rate E1 = mass loss rate M S - Mass loss rate M L .

[0039] The liquid inside the capillary receiving tube 2 experiences mass loss due to evaporation. Evaporation occurs at the liquid receiving port 20 of the capillary receiving tube 2 and at other gaps in the measuring device. Taking the measuring device as an example where it is arranged on an experimental platform, these gaps include the gap between the inner anti-evaporation hood 5 and the experimental platform, the gap between the evaporation well 6 and the experimental platform, and the gap between the outer anti-evaporation hood 4 and the inner anti-evaporation hood 5. Since these gaps are relatively small, the mass loss they cause is less than that at the liquid receiving port 20. In a short time, the mass loss rate at the liquid receiving port 20 is much greater than the mass loss rate at the gaps. Therefore, the mass loss rate at the liquid receiving port 20 accounts for a relatively high proportion of the total mass loss rate.

[0040] As time progresses, the liquid evaporation surface inside the capillary receiving tube 2 gradually shrinks into the capillary receiving tube 2, and the evaporation rate of the liquid evaporation surface decreases significantly. That is, the mass loss rate through the liquid receiving port 20 decreases, while the mass loss rate at other gap locations remains constant. Therefore, the mass loss rate at the liquid receiving port 20 accounts for a relatively low proportion of the total mass loss rate. Thus, in this embodiment, the short-term (expected time period T2) mass loss rate M is used... S -Long-term (expected time period T3) quality loss rate M L The evaporation rate E1 at the liquid receiving port 20 is obtained, and the evaporation rate E2 of the microconvex liquid 3 is derived based on this, making the measurement accurate and efficient.

[0041] As an example, the expected time period T2 can be 30 minutes, the expected time period T3 can be 120 minutes, and the ratio K1 of the expected time T2 to the expected time T3 is 0.25. The quality loss rate M for the expected time period T2 is... S The expected mass loss rate M at a time T2 is 2 μg / min. L If the evaporation rate is 1 μg / min, then the liquid evaporation rate E1 at the liquid receiving port 20 is equal to 1 μg / min.

[0042] In one embodiment, obtaining the evaporation rate E2 of the micro-convex liquid 3 formed at the outlet 10 of the outlet pipe 1 based on the evaporation rate E1 includes: Obtain the liquid evaporation area A1 of the liquid inside the capillary receiving tube 2; Obtain the surface area A2 of the microconvex liquid 3; The evaporation rate E2 is obtained using the following formula: ; in, R 1 The inner diameter of the capillary receiving tube. R 2 Let be the radius of the sphere of the slightly convex liquid. h The height of the slightly convex liquid.

[0043] With the above settings, after the evaporation rate E1 is known, it is used as the standard evaporation rate. The evaporation rate E2 is determined according to the relationship between the liquid evaporation area in the micro-convex liquid 3 and the liquid evaporation area in the capillary receiving tube 2. The evaporation rate E2 can be obtained quickly and accurately.

[0044] Specifically, both the capillary receiving tube 2 and the liquid outlet tube 1 are circular tubes, and the slightly convex liquid 3 is hemispherical with a surface area of ​​[missing information]. The liquid evaporation surface inside the capillary receiving tube 2 is circular, therefore the liquid evaporation area is... ,in R 2 Let be the radius of the sphere of the slightly convex liquid 3 at outlet pipe 1. h The height of the slightly convex liquid 3 at outlet pipe 1. R 1 This is the inner diameter of capillary receiving tube 2. Based on this, ; .

[0045] In this embodiment, during the process of continuously injecting liquid into the outlet tube 1 through the instrument under test and forming a micro-convex liquid 3 at the outlet 10, the height h of the formed micro-convex liquid 3 is controlled to be less than the radius of the sphere. R 2 This is more in line with the calculation method for the sphere crown and improves the accuracy of measurement.

[0046] In one embodiment, the evaporation rate E2 and the morphological relationship of the micro-convex liquid 3 during the tested time period T1, and the pipeline leakage amount Q are considered. leak Obtaining the flow rate Q of the instrument under test includes: The morphological changes of the microconvex liquid 3 were observed during the tested time period T1; For example, the morphological changes of the microconvex liquid 3 can be observed using a microscope. These changes include the enlargement, shrinkage, and stabilization of the microconvex liquid 3 under continuous liquid flow. The observation method can be machine vision recognition. By acquiring images of the microconvex liquid 3, recognizing, analyzing, and processing the images, the area of ​​the microconvex liquid 3 can be calculated, thereby determining the morphological changes and improving the accuracy of the judgment.

[0047] If the shape of the microconvex liquid 3 remains constant during the tested time period T1, the flow rate Q of the tested instrument is obtained according to the following formula: When the shape of the slightly convex liquid 3 remains constant, it means that the evaporation rate of the slightly convex liquid 3 is equal to the flow rate of the liquid flowing from the outlet pipe 1 to the outlet 10. Therefore, given the known pipeline leakage rate Q... leak Under the premise that flow rate Q = evaporation rate E2 + pipeline leakage Q leak ; If the shape of the micro-convex liquid 3 is not constant (increases or decreases) during the inspection time period T1, then the rate of change of the surface area A2 of the micro-convex liquid 3 during the inspection time period T1 is obtained. Based on the rate of change, the evaporation rate correction E3 within the time period T1 under test is obtained, and the flow rate Q of the instrument under test is obtained according to the following formula; Flow rate Q = Evaporation rate E2 + Evaporation rate correction E3 + Pipeline leakage Q leak .

[0048] When the shape of the slightly convex liquid 3 is not constant, it means that the evaporation rate of the slightly convex liquid 3 is not equal to the liquid flow rate discharged through the outlet 10 of the outlet pipe 1. Therefore, it is necessary to obtain the evaporation rate correction amount E3 within the tested time period T1. Then, the flow rate Q = evaporation rate E2 + evaporation rate correction amount E3 + pipeline leakage Q leak In this embodiment, the evaporation rate correction is determined based on the morphological changes of the microconvex liquid 3, thereby further improving the accuracy of flow measurement.

[0049] In one embodiment, the evaporation rate correction amount E3 is obtained according to the following formula: E3 ; in, R 2 Let be the radius of the sphere of the slightly convex liquid. h The height of the slightly convex liquid. t The time period T1 being inspected R 1 The inner diameter of the capillary receiving tube. The height change rate of the slightly convex liquid surface.

[0050] In one embodiment, an alternative measurement method is proposed when the shape of the micro-convex liquid 3 is not constant. Specifically, if the shape of the micro-convex liquid 3 is observed to be not constant during the tested time period T1, the humidity of the environment in which the micro-convex liquid 3 and the liquid receiving port 20 of the capillary receiving tube 2 are located is adjusted to change the evaporation rate of the micro-convex liquid 3 so that the shape of the micro-convex liquid 3 remains constant. Obtain the evaporation rate E of the liquid in the capillary receiving tube 2. 10 ; Based on the evaporation rate E 10 The evaporation rate E of the microconvex liquid 3 is obtained. 20 The flow rate Q of the instrument under test is obtained according to the following formula: Flow rate Q = Evaporation rate E 20 + Pipeline leakage Q leak ; In this embodiment, when the shape of the micro-convex liquid 3 is not constant, it means that the evaporation rate of the micro-convex liquid 3 is not equal to the liquid flow rate discharged through the liquid outlet 10 of the liquid outlet pipe 1. Therefore, the evaporation rate of the micro-convex liquid 3 can be adjusted to make the shape of the micro-convex liquid 3 constant. The means of adjusting the evaporation rate is to adjust the humidity of the environment where the micro-convex liquid 3 and the liquid receiving port 20 are located. After the evaporation rate is adjusted to the point that the shape of the micro-convex liquid 3 is constant, the liquid evaporation rate E of the liquid receiving port 20 is obtained again. 10 And based on the evaporation rate E 10 Redetermine the evaporation rate E of the microconvex liquid 3 20 At this time, the slightly convex liquid 3 has an evaporation rate E 20 The flow rate Q = evaporation rate E² + pipeline leakage Q can maintain a constant state. leak The evaporation rate is adjusted based on the morphological changes of the microconvex liquid 3, and the flow rate is then derived in reverse from the adjusted evaporation rate. This measurement method is simple and can improve the accuracy of flow rate measurement. As an example, when it is necessary to increase the evaporation rate, the degree of airflow exchange between the outer evaporation shield 4 and the external environment can be increased, for example, by changing the size of the gap.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for measuring extremely small liquid flow rates, characterized in that, include: Inject liquid into the capillary receiving tube; Connect the liquid outlet tube to the instrument under test, continuously inject liquid into the liquid outlet tube through the instrument under test to form a micro-convex liquid at the outlet, and ensure that the micro-convex liquid does not come into contact with the capillary receiving tube. The evaporation rate E1 of the liquid in the capillary receiving tube is obtained based on the balance reading during the tested time period T1. The evaporation rate E2 of the micro-convex liquid formed at the outlet of the liquid outlet pipe is obtained based on the evaporation rate E1. Obtain the leakage Q of the pipeline between the instrument under test and the outlet pipe. leak ; Based on the relationship between the evaporation rate E2 and the morphology of the microconvex liquid during the tested time period T1, and the pipeline leakage Q leak Obtain the flow rate Q of the instrument under test.

2. The method for measuring minimal liquid flow rate according to claim 1, characterized in that, The process of injecting liquid into the capillary receiving tube includes: Liquid is injected into the capillary receiving tube, and the liquid evaporation surface is made flush with the liquid receiving port of the capillary receiving tube.

3. The method for measuring minimal liquid flow rate according to claim 1, characterized in that, The method of obtaining the evaporation rate E1 of the liquid in the capillary receiving tube based on the balance reading during the tested time period includes: The mass loss rate M is obtained based on the balance readings within the expected time period T2. S ; The mass loss rate M is obtained based on the balance readings within the expected time period T3. L The expected time period T2 and the expected time period T3 are sequential within the inspected time period T1, and the ratio K1 of the expected time period T2 to the expected time period T3 is 0.1-0.5; The evaporation rate E1 = mass loss rate M S - Mass loss rate M L .

4. The method for measuring minimal liquid flow rate according to claim 1, characterized in that, The process of obtaining the evaporation rate E2 of the micro-convex liquid formed at the outlet of the liquid outlet pipe based on the evaporation rate E1 includes: Obtain the liquid evaporation area A1 of the liquid inside the capillary receiving tube; Obtain the surface area A2 of the microconvex liquid; The evaporation rate E2 is obtained using the following formula: ； in, R 1 The inner diameter of the capillary receiving tube. R 2 Let be the radius of the sphere of the slightly convex liquid. h The height of the slightly convex liquid.

5. The method for measuring minimal liquid flow rate according to claim 4, characterized in that, The relationship between the evaporation rate E2 and the morphology of the microconvex liquid during the tested time period T1, and the pipeline leakage amount Q, are considered. leak Obtaining the flow rate Q of the instrument under test includes: The morphological changes of the microconvex liquid were observed during the tested time period T1; If the shape of the microconvex liquid remains constant during the tested time period T1, the flow rate Q of the tested instrument is obtained according to the following formula: Flow rate Q = Evaporation rate E2 + Pipeline leakage Q leak ; If the shape of the micro-convex liquid is not constant during the inspection time period T1, then obtain the rate of change of the surface area A2 of the micro-convex liquid during the inspection time period T1. Based on the rate of change, the evaporation rate correction E3 within the time period T1 under test is obtained, and the flow rate Q of the instrument under test is obtained according to the following formula; Flow rate Q = Evaporation rate E2 + Evaporation rate correction E3 + Pipeline leakage Q leak .

6. The method for measuring minimal liquid flow rate according to claim 5, characterized in that, The evaporation rate correction amount E3 is obtained according to the following formula: E3 ； Where R2 is the radius of the sphere of the microconvex liquid, h is the height of the microconvex liquid, t is the time period T1 under test, and R1 is the inner diameter of the capillary receiving tube. The height change rate of the microconvex liquid.

7. The method for measuring minimal liquid flow rate according to claim 4, characterized in that, The relationship between the evaporation rate E2 and the morphology of the microconvex liquid during the tested time period T1, and the pipeline leakage amount Q, are considered. leak Obtaining the flow rate Q of the instrument under test includes: The morphological changes of the microconvex liquid were observed during the tested time period T1; If the shape of the microconvex liquid remains constant during the tested time period T1, the flow rate Q of the tested instrument is obtained according to the following formula: Flow rate Q = Evaporation rate E2 + Pipeline leakage Q leak ; If the shape of the micro-convex liquid is not constant during the time period T1 under inspection, the humidity of the environment where the micro-convex liquid and the liquid receiving port of the capillary receiving tube are located is adjusted to change the evaporation rate of the micro-convex liquid so that the shape of the micro-convex liquid remains constant. Obtain the evaporation rate E of the liquid in the current capillary receiving tube. 10 ; Based on the evaporation rate E 10 Obtain the evaporation rate E of the microconvex liquid. 20 The flow rate Q of the instrument under test is obtained according to the following formula: Flow rate Q = Evaporation rate E 20 + Pipeline leakage Q leak .

8. The method for measuring minimal liquid flow rate according to claim 1, characterized in that, During the process of continuously injecting liquid into the outlet tube through the instrument under test and forming a micro-convex liquid at the outlet, the height h of the formed micro-convex liquid is controlled to be less than its spherical radius. R 2 .

9. The method for measuring minimal liquid flow rate according to claim 5 or 7, characterized in that, The morphological changes of the micro-convex liquid are obtained by image recognition of the micro-convex liquid using machine time.

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