Single-probe conductive probe for liquid drop measurement
By designing a single-probe conductivity probe, adopting a coaxial structure and an insulating coating, the problems of droplet conductivity probe jitter and liquid film formation in two-phase flow experiments were solved, realizing accurate measurement and efficient calibration of small droplets.
Patent Information
- Application Number
- CN202511474580.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-15
- Publication Date
- 2026-01-09
AI Technical Summary
In two-phase flow experiments, droplet conductivity probes are prone to vibration, sensor distribution is asymmetrical, and droplet size measurement is prone to forming a liquid film, which leads to signal distortion, thus limiting the measurement range and accuracy.
Design a single-probe conductivity probe, including a front probe, a common electrode, and a rear probe, with a coaxial structure. Use an insulating coating to cover the sensor contact part, and calculate the droplet diameter and velocity by the time difference between the signals from the front and rear probes.
It achieves accurate measurement of small droplets (with a minimum diameter of about 0.15 mm), solves the problems of liquid film interference and signal distortion, has a simple structure and can withstand high flow rates, and simplifies the calibration method.
Smart Images
Figure CN121297906A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of droplet conductivity probe technology, specifically a single-probe conductivity probe for droplet measurement. Background Technology
[0002] A droplet conductivity probe typically consists of a front sensor, a common electrode sensor, and a rear sensor, with the common electrode sensor having the same length as the front sensor. In practical use, only the tips of the front and rear sensors are exposed, while the common electrode sensor is completely exposed. The front and rear sensors are connected to the positive terminal of a power supply, while the common electrode sensor needs to be connected to a lower voltage power supply. The sheath is grounded and in direct contact with the fluid.
[0003] The signals from droplet conductivity probes are divided into two categories: phase signals and field signals. The phase signal measures the potential difference between the common electrode and the preceding / following sensors, used to determine whether the probe tip is in the liquid or gas phase. The field signal measures the potential difference between the common electrode and the sleeve, used to distinguish whether the phase is dispersed or continuous. For example, when the droplet conductivity probe tip is in a continuous gas phase, both the phase and field signals will remain at high levels. When the probe sensor suddenly comes into contact with the droplet, the field signal remains high, and the phase signal becomes low, thus identifying the droplet. However, the measurement range and accuracy of the droplet conductivity probe are affected by three factors:
[0004] Firstly, in two-phase flow experiments, droplets typically exist in turbulent flow into mist-like flow, and these flow conditions all have high gas and liquid velocities. Each sensor of the droplet probe is small, typically a filament with a diameter of 0.17 mm (including coating). The three sensors are prone to vibration under these flow conditions, leading to signal distortion. Furthermore, the vibration can cause friction between the sensors, resulting in the failure of the insulating coating on the surfaces of the front and rear sensors.
[0005] Secondly, when repeatedly fabricating droplet conductivity probes, the distribution of the three sensors is asymmetrical and their relative positions are difficult to control. As a result, the properties of each droplet probe are inconsistent, and there is no universal calibration result.
[0006] Thirdly, the droplet size that the droplet conductivity probe can measure is determined by the radial distance between the common electrode sensor and the front / rear sensors. During measurement, the droplet needs to touch all three sensors to obtain a valid signal. The droplet size is typically 0-2 mm, and the smaller the radial distance between the three sensors, the smaller the detectable droplet size. However, in actual measurements, it has been found that a liquid film easily forms between the rear sensor and the common electrode sensor, causing severe fluctuations in the measurement signal waveform and making it impossible to extract valid information. Publicly available literature indicates that when the radial spacing is greater than 0.3 mm, the liquid film phenomenon can be significantly reduced, but at this point, the minimum measurement size of the droplet conductivity probe is too large, and the obtained information is not representative. Currently, no publicly available information mentions an effective improvement method. Summary of the Invention
[0007] The purpose of this invention is to provide a single-probe conductivity probe for droplet measurement, comprising a front probe, a common electrode, a rear probe, an alumina tube, and a stainless steel outer tube.
[0008] The front probe is a stainless steel wire. One end of the stainless steel wire tapers along the axial direction to form a sharp end with a conical cross-sectional profile, which is referred to as the head of the front probe, and the other end is referred to as the tail of the front probe.
[0009] The outer wall of the stainless steel wire is fitted with a common electrode, so that the tip of the front probe head and the tail of the front probe are exposed.
[0010] The stainless steel wire is covered with an insulating coating I at the point where it contacts the common electrode.
[0011] The common electrode is a stainless steel capillary tube I. The end closest to the front probe head is called the common electrode head, and the other end is called the common electrode tail.
[0012] The outer wall of the stainless steel capillary tube I is fitted with a rear probe, exposing the front half and tail of the common electrode. The end face of the common electrode head and the position in contact with the rear probe are covered with an insulating coating II.
[0013] The rear probe is a stainless steel capillary tube II. The end closest to the front probe head is referred to as the rear probe head, and the other end is referred to as the rear probe tail.
[0014] The head end face and tail end face of the rear probe are exposed, and the outer wall of the rear probe is covered with an insulating coating III.
[0015] The tail of the front probe, the tail of the common electrode, and the tail of the rear probe are all connected with wires.
[0016] The outer wall of the stainless steel capillary tube II is fitted with a corundum tube.
[0017] The corundum tube is embedded in the stainless steel outer tube, and AB glue is applied to the connection position between the stainless steel outer tube and the corundum tube.
[0018] In use, wrap wires around the stainless steel outer tube and ground it. Then connect the front and rear probes to the acquisition system through their respective wires. Connect the common electrode to the power supply through a wire and then connect it to the acquisition system. Calculate the droplet diameter, liquid holding capacity, and droplet velocity by the time difference between the signals from the front and rear probes.
[0019] Furthermore, the length of the common electrode is less than the length of the front probe, that is, the length of the stainless steel capillary tube I is less than the length of the stainless steel wire.
[0020] Furthermore, the portion of the front probe head near the front probe tail is located within the inner hole of the stainless steel capillary tube I.
[0021] The inner bore shape of the stainless steel capillary tube I is adapted to the outer contour shape of the front probe.
[0022] Furthermore, the common electrode head is a transition section that gradually narrows along the axial direction, and the outer contour of the cross section is an isosceles trapezoid.
[0023] Furthermore, the length of the rear probe is less than the length of the common electrode, that is, the length of stainless steel capillary II is less than the length of stainless steel capillary I.
[0024] Furthermore, the head of the rear probe is a transition section that tapers gradually along the axial direction, and the outer contour of the cross section is an isosceles trapezoid.
[0025] Furthermore, the insulating coating I, insulating coating II, and insulating coating III are polytetrafluoroethylene coatings.
[0026] Furthermore, the coating thickness of insulating coating I, insulating coating II, and insulating coating III is 20 μm.
[0027] Furthermore, the diameter of the front probe is 0.05 mm.
[0028] The inner diameter of the common electrode is 0.11 mm and the outer diameter is 0.2 mm.
[0029] The inner diameter of the rear probe is 0.3 mm, and the outer diameter is 0.4 mm.
[0030] Furthermore, the axial distance between the tip of the front probe and the end face of the common electrode is greater than 0 and less than 10 μm.
[0031] The axial distance between the end face of the common electrode head and the end face of the rear probe head is 1.2 mm.
[0032] The technical effects of this invention are undeniable, and its beneficial effects are as follows:
[0033] 1. The single-probe conductivity probe of this invention can measure small droplets (with a minimum diameter of approximately 0.15 mm), solving the problem of signal interference caused by liquid films. It has high strength and can withstand high flow rate conditions.
[0034] 2. The single-probe conductivity probe of the present invention has a simple structure, high repeatability, and smaller size and less invasiveness compared to the traditional three-probe droplet probe.
[0035] 3. The single-probe conductivity probe of the present invention solves the problem that the traditional three-probe droplet probe causes signal distortion when measuring continuous droplets due to the small tip-to-tip distance, resulting in a liquid film at the tip.
[0036] 4. The coaxial design of the single-probe conductivity probe of this invention can improve the calibration method and solve the problem that the traditional three-probe droplet probe, due to its asymmetrical structure, requires a rectangular calibration method, which leads to complex operation and difficulty in maintaining structural consistency. Attached Figure Description
[0037] Figure 1 This is a schematic diagram of the assembly structure of the front probe, common electrode, and rear probe;
[0038] Figure 2 This is a schematic diagram of the structure of the single-probe conductivity probe of the present invention;
[0039] Figure 3 This is a schematic diagram of signal distortion in a traditional droplet conductivity probe.
[0040] Figure 4 This is a schematic diagram of the signal of the single-probe conductivity probe of the present invention;
[0041] Figure 5 A schematic diagram (including top view) of the asymmetric structure of a traditional three-probe droplet probe and its rectangular calibration diagram;
[0042] Figure 6 This is a schematic diagram (including a top view) of the structure of the single-probe conductivity probe of the present invention and its calibration diagram.
[0043] In the diagram: Front probe 1, front probe head 101, front probe tail 102, common electrode 2, common electrode head 201, common electrode tail 202, insulating coating I 3, insulating coating II 4, rear probe 7, rear probe head 701, rear probe tail 702, insulating coating III 8, AB glue 12, corundum tube 13, stainless steel outer tube 14. Detailed Implementation
[0044] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.
[0045] Example 1:
[0046] See Figure 1 A single-probe conductivity probe for droplet measurement includes a front probe 1, a common electrode 2, a rear probe 7, an alumina tube 13, and a stainless steel outer tube 14.
[0047] The front probe 1 is a stainless steel wire. One end of the stainless steel wire tapers along the axial direction to form a sharp end with a conical cross-sectional profile, which is referred to as the front probe head 101, and the other end is referred to as the front probe tail 102.
[0048] The outer wall of the stainless steel wire is fitted with a common electrode 2, so that the tip of the front probe head 101 and the tail of the front probe 102 are exposed.
[0049] The stainless steel wire is covered with an insulating coating I3 at the point where it contacts the common electrode 2.
[0050] The common electrode 2 is a stainless steel capillary tube I. The end closest to the front probe head 101 is designated as the common electrode head 201, and the other end is designated as the common electrode tail 202.
[0051] The outer wall of the stainless steel capillary tube I is fitted with a rear probe 7, so that the front half of the common electrode 2 and the tail 202 of the common electrode are exposed. The end face of the head 201 of the common electrode and the position where it contacts the rear probe 7 are covered with an insulating coating II 4.
[0052] The rear probe 7 is a stainless steel capillary tube II. The end near the front probe head 101 is designated as the rear probe head 701, and the other end is designated as the rear probe tail 702.
[0053] The end face of the head 701 and the end face of the tail 702 of the rear probe are exposed, and the outer wall of the rear probe 7 is covered with an insulating coating Ⅲ8.
[0054] The front probe tail 102, the common electrode tail 202, and the rear probe tail 702 are all connected to wires.
[0055] See Figure 2 The outer wall of the stainless steel capillary tube II is fitted with a corundum tube 13.
[0056] The corundum tube 13 is embedded in the stainless steel outer tube 14, and AB glue 12 is applied to the connection position between the stainless steel outer tube 14 and the corundum tube 13.
[0057] In use, the stainless steel outer tube 14 is wrapped with wires and grounded. Then, the front probe 1 and the rear probe 7 are connected to the acquisition system through their respective wires. The common electrode 2 is connected to the power supply through a wire and then connected to the acquisition system. The droplet diameter, liquid holding rate and droplet velocity are calculated by the time difference between the signals from the front and rear probes.
[0058] Example 2:
[0059] The main structure of this embodiment is the same as that of Embodiment 1. Further, see [link to Embodiment 1]. Figure 1 The length of the common electrode 2 is less than the length of the front probe 1, that is, the length of the stainless steel capillary tube I is less than the length of the stainless steel wire.
[0060] Example 3:
[0061] The main structure of this embodiment is the same as any one of embodiments 1-2. Further, see [link to embodiment 1-2]. Figure 1 The portion of the front probe head 101 near the front probe tail 102 is located in the inner hole of the stainless steel capillary tube I (i.e., a portion of the constricted section of the front probe head 101 is located in the inner hole of the stainless steel capillary tube I).
[0062] The inner bore shape of the stainless steel capillary tube I is adapted to the outer contour shape of the front probe.
[0063] Example 4:
[0064] The main structure of this embodiment is the same as any one of embodiments 1 to 3. Further, see [link to embodiment 1]. Figure 1 The common pole head 201 is a transition section that gradually narrows along the axial direction, and the outer contour of the cross section is an isosceles trapezoid.
[0065] Example 5:
[0066] The main structure of this embodiment is the same as any one of embodiments 1 to 4. Further, see [link to embodiment 1]. Figure 1 The length of the rear probe 7 is less than the length of the common electrode 2, that is, the length of the stainless steel capillary II is less than the length of the stainless steel capillary I.
[0067] Example 6:
[0068] The main structure of this embodiment is the same as any one of embodiments 1 to 5. Further, see [link to embodiment 1-5]. Figure 1 The rear probe head 701 is a transition section that gradually narrows along the axial direction, and the outer contour of the cross section is an isosceles trapezoid.
[0069] Example 7:
[0070] The main structure of this embodiment is the same as any one of embodiments 1 to 6. Further, see [link to embodiment 1-6]. Figure 1The outer wall of the front probe 1, at the connection point with the common electrode 2, facing the tail 102 of the front probe, is also covered with a section of insulating coating II4.
[0071] Example 8:
[0072] The main structure of this embodiment is the same as any one of embodiments 1 to 7. Furthermore, the insulating coating I3, insulating coating II4 and insulating coating III8 are polytetrafluoroethylene coatings.
[0073] Example 9:
[0074] The main structure of this embodiment is the same as any one of embodiments 1 to 8. Furthermore, the coating thickness of insulating coating I3, insulating coating II4 and insulating coating III8 is 20 μm.
[0075] Example 10:
[0076] The main structure of this embodiment is the same as any one of embodiments 1 to 9. Furthermore, the diameter of the front probe 1 is 0.05 mm.
[0077] The inner diameter of the common electrode 2 is 0.11 mm, and the outer diameter is 0.2 mm.
[0078] The inner diameter of the rear probe 7 is 0.3 mm, and the outer diameter is 0.4 mm.
[0079] Example 11:
[0080] The main structure of this embodiment is the same as any one of embodiments 1 to 10. Furthermore, the axial distance between the tip of the front probe head 101 and the end face of the common electrode head 201 is greater than 0 and less than 10 μm.
[0081] The axial distance between the end face of the common electrode head 201 and the end face of the rear probe head 701 is 1.2mm.
[0082] Example 12:
[0083] The main structure of this embodiment is the same as any one of embodiments 1 to 11. Furthermore, this invention can achieve the measurement of small droplets (with a minimum diameter of approximately 0.15 mm), solving the interference of the liquid film on the signal. It has high strength and can withstand high flow rate conditions. It has a simple structure, high repeatability, and is smaller and less invasive than traditional three-probe droplet probes.
[0084] A stainless steel wire with a pointed head serves as the front probe 1, with the exposed tip serving as the detection area, while the rest of the area is coated with an insulating coating (polytetrafluoroethylene coating).
[0085] Insert the front probe 1 into a capillary stainless steel tube, which serves as the common electrode 2. The head 201 of the common electrode needs to be coated with an insulating layer to prevent electrical conduction with the front probe 1. The upper part of the common electrode 2 remains exposed.
[0086] The combination of the front probe 1 and the common electrode 2 is then inserted into a larger capillary stainless steel tube, which serves as the rear probe 7.
[0087] Electrical insulation between the common electrode 2 and the rear probe 7 is achieved by coating the common electrode with an insulating coating. The rear probe head 701 has a small exposed area as the detection zone, while the remaining surface is coated with an insulating coating.
[0088] The electrical connections between the front probe, common electrode, and rear probe and the rear circuitry are achieved by soldering wires to their respective exposed rear ends.
[0089] The probe is then inserted into the corundum tube 13 to enhance its impact resistance. The entire probe is then embedded into the stainless steel outer tube 14 to form a complete droplet probe. AB glue is applied to the corundum tube and left to stand for 48 hours to ensure a firm connection.
[0090] All insulating coatings are 20 μm thick. The front probe has a diameter of 0.05 mm; the common electrode has an inner diameter of 0.11 mm and an outer diameter of 0.2 mm; the rear probe has an inner diameter of 0.3 mm and an outer diameter of 0.4 mm.
[0091] Both the common electrode and the head of the rear probe are ground into a conical shape.
[0092] The three probes are kept coaxial, with the axial distance between the common electrode tip and the rear probe tip maintained at 1.2 mm. The axial distance between the tip of the front probe and the common electrode tip is kept within 10 μm.
[0093] Example 13:
[0094] The main structure of this embodiment is the same as any one of embodiments 1 to 12. Furthermore, the working principle of the present invention is as follows:
[0095] The stainless steel outer tube 14 is grounded by a wire wound around it. The front probe 1 and the rear probe 7 are connected to the acquisition system through their respective wires. The common electrode 2 is connected to the acquisition system through a wire connected to a +1V power supply.
[0096] If the probe is in the air of the flow channel, both the front probe 1 and the rear probe 7 will maintain a high level, and the common terminal will be +1V.
[0097] When a small droplet is present, the front probe 1 first penetrates the droplet, and then the droplet contacts the common electrode 2, causing the signal of the front probe 1 to become low. Subsequently, it contacts the tiny exposed area of the head of the rear probe 7, causing the signal of the rear probe 7 to become high. The signals from the two probes have a time difference due to the axial distance between the probes, and this time difference can be used to calculate parameters such as droplet diameter, liquid holdup, and droplet velocity.
[0098] Theoretically, the radial distance between the front probe 1 and the rear probe 7 determines the smallest detectable droplet diameter. This patent proposes a method to achieve a theoretically detectable minimum droplet diameter of 0.15 mm. When a liquid mass is present, the large volume of the liquid phase simultaneously envelops the grounded stainless steel outer sleeve and the common electrode, causing the +1V signal of the common electrode to drop low. Therefore, this method can be used to distinguish between small droplets (dispersed liquid phase) and liquid masses (continuous liquid phase).
[0099] Example 14:
[0100] The main structure of this embodiment is the same as any one of embodiments 1 to 13. Furthermore, the droplet diameter, liquid holding rate and droplet velocity are calculated by the time difference between the signals from the front and rear probes.
[0101] The droplet velocity of the j-th droplet and droplet diameter The calculation formula is as follows:
[0102] （1） （2）
[0103] In the formula: This refers to the distance between the front and rear probes in the main direction.
[0104] Let j be the time difference before and after the j-th droplet touches the probe;
[0105] The residence time of the j-th droplet is extracted using an algorithm;
[0106] Time-averaged parameters of droplets, such as droplet volume fraction (liquid holdup). Average droplet velocity Calculate using the following formula:
[0107] （3） （4）
[0108] In the formula: denoted as the total sampling time, where j = 1, 2, ..., N, and N is the total number of droplets.
[0109] Example 15:
[0110] The main structure of this embodiment is the same as any one of embodiments 1 to 12. Further, see [link to embodiment 1]. Figure 3 , Figure 4 The single-probe conductivity probe of the present invention solves the problem that the traditional three-probe droplet probe causes signal distortion when measuring continuous droplets due to the small tip-to-tip distance, resulting in a liquid film at the tip.
[0111] Example 16:
[0112] The main structure of this embodiment is the same as any one of embodiments 1 to 15. Further, see [link to embodiment 1]. Figure 5 , Figure 6 The coaxial design of the single-probe conductivity probe of this invention can improve the calibration method and solve the problems of complex operation and difficulty in maintaining structural consistency caused by the need for rectangular calibration method when calibrating traditional three-probe droplet probes due to their asymmetrical structure.
[0113] Example 17:
[0114] The main structure of this embodiment is the same as any one of embodiments 1 to 16, and further... Figure 5 The asymmetric structure and top view of a traditional three-probe droplet probe are shown. It can be seen that the interaction between the droplet and the probe is different at any position during probe measurement. Therefore, rectangular calibration is required at different positions during calibration.
[0115] Figure 6 The coaxial droplet probe structure and top view are shown. The symmetrical structure greatly simplifies the calibration process, requiring only calibration of one side.
Claims
1. A single-probe conductivity probe for droplet measurement, characterized in that: It includes a front probe (1), a common electrode (2), a rear probe (7), a corundum tube (13), and a stainless steel outer tube (14). The front probe (1) is a stainless steel wire. One end of the stainless steel wire tapers along the axial direction to form a sharp end with a tapered cross-sectional profile, which is called the head of the front probe (101), and the other end is called the tail of the front probe (102). The outer wall of the stainless steel wire is fitted with a common electrode (2), so that the tip of the front probe head (101) and the tail of the front probe (102) are exposed; The stainless steel wire is covered with an insulating coating I (3) at the point where it contacts the common electrode (2); The common electrode (2) is a stainless steel capillary tube I. The end closest to the front probe head (101) is called the common electrode head (201), and the other end is called the common electrode tail (202). The outer wall of the stainless steel capillary tube I is fitted with a rear probe (7), so that the front half of the common electrode (2) and the tail (202) of the common electrode are exposed; the end face of the head (201) of the common electrode and the position in contact with the rear probe (7) are covered with an insulating coating II (4). The rear probe (7) is a stainless steel capillary tube II. The end near the head (101) of the front probe is called the head (701) of the rear probe, and the other end is called the tail (702) of the rear probe. The end face of the head (701) and the end face of the tail (702) of the rear probe are exposed, and the outer wall of the rear probe (7) is covered with the insulating coating III (8). The front probe tail (102), the common electrode tail (202), and the rear probe tail (702) are all connected to wires; The outer wall of the stainless steel capillary tube II is fitted with a corundum tube (13); The corundum tube (13) is embedded in the stainless steel outer tube (14), and AB glue (12) is applied at the connection between the opening of the stainless steel outer tube (14) and the corundum tube (13). When in use, wrap wires around the stainless steel outer tube (14) and ground it. Then connect the front probe (1) and the rear probe (7) to the acquisition system through their respective wires. Connect the common electrode (2) to the power supply through the wire and then connect it to the acquisition system. Calculate the droplet diameter, liquid holding rate and droplet velocity by the time difference between the front and rear probe signals.
2. The single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The length of the common electrode (2) is less than the length of the front probe (1), that is, the length of the stainless steel capillary tube I is less than the length of the stainless steel wire.
3. The single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The front probe head (101) is located in the inner hole of the stainless steel capillary tube I on the side near the front probe tail (102). The inner bore shape of the stainless steel capillary tube I is adapted to the outer contour shape of the front probe.
4. The single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The common pole head (201) is a transition section that gradually narrows along the axial direction, and the outer contour of the cross section is an isosceles trapezoid.
5. A single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The length of the rear probe (7) is less than the length of the common electrode (2), that is, the length of the stainless steel capillary II is less than the length of the stainless steel capillary I.
6. The single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The rear probe head (701) is a transition section that gradually narrows along the axial direction, and the outer contour of the cross section is an isosceles trapezoid.
7. A single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The insulating coatings I (3), II (4) and III (8) are polytetrafluoroethylene coatings.
8. A single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The thickness of insulating coating I (3), insulating coating II (4) and insulating coating III (8) is 20 μm.
9. A single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The diameter of the front probe (1) is 0.05 mm; The inner diameter of the common electrode (2) is 0.11 mm and the outer diameter is 0.2 mm; The inner diameter of the rear probe (7) is 0.3 mm and the outer diameter is 0.4 mm.
10. A single-probe conductivity probe for droplet measurement according to claim 1, characterized in that: The axial distance between the tip (101) of the front probe head and the end face of the common electrode head (201) is greater than 0 and less than 10 μm; The axial distance between the end face of the common electrode head (201) and the end face of the rear probe head (701) is 1.2 mm.