Conductivity Sensors for Oil Quality Monitoring

Abstract

The present application provides a conductivity sensor for oil quality monitoring, including a sensor body, a measuring electrode assembly, a flow guide component, a temperature compensation unit and a signal processing unit. The sensor body includes a tubular housing and a measuring chamber arranged in the tubular housing. The measuring electrode assembly is arranged in the measuring chamber, including an inner electrode and an outer electrode arranged coaxially, and an annular measuring space is formed between the inner electrode and the outer electrode. The flow guide component is arranged at the oil inlet end of the annular measuring space, and is used to guide the oil entering the annular measuring space into a laminar flow state. The temperature compensation unit includes a temperature sensor arranged in the annular measuring space. The signal processing unit is electrically connected to the measuring electrode assembly and the temperature compensation unit. The conductivity sensor improves the accuracy of oil quality measurement by arranging the flow guide component and the temperature compensation unit.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a conductivity sensor for oil quality monitoring. Background Art

[0002] During the production process of an oil refinery, the quality of oil products may change due to various factors during the flow of oil products in the pipeline. For example, corrosion on the inner wall of the pipeline, loose sealing at the pipeline joints, etc. may cause oil products to be contaminated. At present, oil refineries usually install conductivity sensors at the inlet and outlet of oil product pipelines to monitor the quality of oil products by measuring the conductivity of the oil products.

[0003] However, existing conductivity sensors have low measurement accuracy in practical applications. This is because the oil is in a flowing state in the pipeline, and eddy currents are easily formed between the sensor's measuring electrodes and the flowing oil, causing fluctuations in the measurement signal. In addition, the temperature change of the oil during the flow process will also affect the measured value of conductivity, further reducing the measurement accuracy. The problem of low measurement accuracy makes it difficult for refineries to detect abnormal changes in oil quality in a timely and accurate manner, thus affecting the timeliness and effectiveness of product quality control.

[0004] Therefore, how to improve the measurement accuracy of conductivity sensors in oil transportation pipelines is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present application is to provide a conductivity sensor for oil quality monitoring, so as to solve the technical problem of low measurement accuracy of existing conductivity sensors in oil transportation pipelines.

[0006] An embodiment of the present application provides a conductivity sensor for oil quality monitoring, comprising: a sensor body, the sensor body comprising a tubular shell and a measuring chamber arranged in the tubular shell; a measuring electrode assembly, the measuring electrode assembly is arranged in the measuring chamber, comprising an inner electrode and an outer electrode arranged coaxially, and an annular measuring space is formed between the inner electrode and the outer electrode; a flow guide member, the flow guide member is arranged at the oil inlet end of the annular measuring space, and is used to guide the oil entering the annular measuring space into a laminar flow state; a temperature compensation unit, the temperature compensation unit comprising a temperature sensor arranged in the annular measuring space; and a signal processing unit, the signal processing unit is electrically connected to the measuring electrode assembly and the temperature compensation unit.

[0007] In the above conductivity sensor, the axis of the measuring chamber coincides with the axis of the tubular housing, and an annular cavity is provided between the measuring chamber and the tubular housing.

[0008] In the above conductivity sensor, the measuring chamber comprises: an oil inlet end, which is provided with a tapered transition section; and an oil outlet end, which is provided with an expansion section.

[0009] In the above conductivity sensor, a plurality of guide ribs are arranged inside the measuring chamber, the guide ribs are evenly distributed along the circumference and are parallel to the axis of the measuring chamber, and the cross section of the guide ribs is streamlined.

[0010] In the above conductivity sensor, the inner wall of the measuring chamber is provided with a plurality of annular grooves.

[0011] In the above conductivity sensor, a plurality of annular protrusions are provided on the outer surface of the inner electrode, and the annular protrusions are arranged in sequence along the axial direction of the inner electrode.

[0012] In the above conductivity sensor, each of the annular protrusions includes: a main body portion, which is in a circular ring shape and has a trapezoidal cross section; and transition portions, which are located on both sides of the main body portion.

[0013] In the above conductivity sensor, the spacing between adjacent annular protrusions gradually increases from the middle of the inner electrode to both ends, and the height of the annular protrusions gradually decreases from the middle of the inner electrode to both ends.

[0014] In the above conductivity sensor, the surface of each annular protrusion is provided with a plurality of arc-shaped grooves evenly distributed along the circumferential direction.

[0015] In the above conductivity sensor, the outer electrode includes a plurality of annular electrode units arranged along the axial direction, and adjacent annular electrode units are separated by insulating rings; each of the annular electrode units includes: a main electrode layer, which is located on the inner side; and a shielding electrode layer, which is located on the outer side.

[0016] The conductivity sensor of the present application sets a flow guide component at the oil inlet end of the annular measurement space, and the flow guide component guides the oil entering the annular measurement space into a laminar flow state. Since the laminar flow has the characteristics of stable flow and uniform velocity distribution, the eddy current phenomenon in the measurement space can be significantly reduced, thereby reducing the interference of the flow state on the conductivity measurement. In addition, the inner electrode and the outer electrode of the conductivity sensor of the present application are coaxially arranged to form an annular measurement space, so that the electric field distribution can be more uniform, further improving the measurement accuracy of the conductivity sensor in the oil product transportation pipeline.

[0017] The conductivity sensor of the present application also has a temperature sensor arranged in the annular measuring space, and monitors the oil temperature in real time and performs compensation calculations through a temperature compensation unit, thereby effectively eliminating the influence of temperature changes on the conductivity measurement and making the final output conductivity value more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a conductivity sensor for oil quality monitoring provided in an embodiment of the present application.

[0019] Figure 2 yes Figure 1 A cross-sectional view of a conductivity sensor for oil quality monitoring is shown.

[0020] Figure 3 yes Figure 1 or Figure 2 The schematic diagram shown is a schematic diagram of the positional relationship between the inner electrode and the outer electrode of the conductivity sensor for oil quality monitoring.

[0021] Figure 4 yes Figures 1 to 3 The schematic diagram of the longitudinal section of the inner electrode of the conductivity sensor for oil quality monitoring is shown. DETAILED DESCRIPTION

[0022] The specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0023] The terms "first", "second" and similar words do not indicate any order, quantity or importance, but are only used to distinguish different technical features. The term "plurality" and similar words mean two or more, unless otherwise clearly defined.

[0024] The embodiments of the present application may be combined with each other.

[0025] like Figure 1 As shown, in order to solve the technical problem that the existing conductivity sensor has low measurement accuracy in the oil delivery pipeline 10, the present application provides a conductivity sensor 20 for oil quality monitoring.

[0026] The conductivity sensor 20 of the present application can be applied to the oil product transportation pipeline system of the oil refinery, which includes the main transportation pipeline, branch pipelines, oil pump stations, valve control systems and monitoring control centers. The main transportation pipeline is a carbon steel pipeline, and multiple detection stations are set at key node positions of the main transportation pipeline, and each detection station is installed with the conductivity sensor 20 of the present application.

[0027] The detection station includes: bypass pipeline unit, sensor installation unit, data acquisition unit and control unit. The bypass pipeline unit is set in parallel with the main delivery pipeline, and the oil flow through the bypass pipeline can be adjusted by controlling the valve. The diameter of the bypass pipeline is smaller than the diameter of the main delivery pipeline, which can ensure that the oil has a suitable flow rate in the sensor measurement space. A flow regulating valve is set upstream of the bypass pipeline to control the oil flow entering the sensor; a back pressure valve is set downstream to maintain a stable pressure in the measurement space.

[0028] The sensor installation unit includes a sensor holder, a sealing joint and a shockproof bracket. The sensor holder is connected to the bypass pipe by a flange connection to ensure a secure installation and easy maintenance. The shockproof bracket is used to reduce the impact of pipeline vibration on sensor measurement, and includes a vibration damping pad and a fixing clamp.

[0029] A pressure sensor is provided upstream and downstream of the conductivity sensor 20 in the bypass pipeline to monitor the pressure change in the measurement space. The pressure sensor is installed on the pipeline through a threaded joint, and its output signal is connected to the data acquisition unit. In addition, a flow meter is also provided near the sensor to monitor the oil flow rate to ensure that the flow conditions during measurement meet the requirements.

[0030] The data acquisition unit is installed in an explosion-proof box, including a data acquisition device, a signal conditioning circuit and a communication module. The data acquisition device simultaneously receives signals from the conductivity sensor 20, the pressure sensor and the flow meter, and performs comprehensive analysis and processing. The signal conditioning circuit conditions the signals of various sensors. The communication module uses industrial Ethernet to exchange data with the monitoring and control center.

[0031] The control unit includes a programmable controller (PLC), a valve controller and a human-machine interface. The PLC automatically adjusts the opening of the flow control valve and the back pressure valve according to the preset control strategy to maintain the stability of the measurement conditions. The valve controller includes an electric control valve and a pneumatic controller to control the valve. The human-machine interface displays real-time monitoring data and equipment operating status, and provides manual control functions.

[0032] The monitoring and control center connects all the testing sites to the Internet through industrial Ethernet to achieve centralized monitoring. The monitoring and control center is equipped with a server, database and monitoring software. The server is responsible for data collection, storage and processing. The database records historical monitoring data and supports data query and analysis functions. The monitoring software provides a graphical interface to display the operating status of the entire pipeline system and oil quality parameters.

[0033] In actual application, after the oil enters the bypass pipeline from the main delivery pipeline, it is first adjusted to a suitable flow rate by the flow control valve, and then enters the conductivity sensor 20. The flow guide component 206 of the conductivity sensor 20 transforms the turbulent oil into a laminar flow, ensuring the stability of the flow state in the measurement space. The measuring electrode detects the conductivity of the oil, while the temperature sensor 204 monitors the oil temperature. These data are processed by the signal processing unit 205 and transmitted to the monitoring and control center together with parameters such as pressure and flow.

[0034] The software system of the monitoring and control center analyzes the received data to determine the oil quality status. If an abnormality is detected, the system will immediately issue an alarm and automatically adjust the relevant process parameters. At the same time, the system will record the abnormal data to provide a basis for subsequent analysis and processing.

[0035] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the conductivity sensor 20 provided in the present application includes a sensor body, a measuring electrode assembly, a flow guiding member 206 , a temperature compensation unit and a signal processing unit 205 .

[0036] The sensor body comprises a tubular housing and a measuring chamber 201 arranged in the tubular housing.

[0037] An oil inlet and an oil outlet are respectively provided at both ends of the tubular housing, and both the oil inlet and the oil outlet are connected to the oil delivery pipeline 10 by threaded connection.

[0038] The measuring chamber 201 is located in the middle of the tubular housing and is cylindrical. The axis of the measuring chamber 201 coincides with the axis of the housing to form a coaxial structure.

[0039] An annular cavity is provided between the measuring chamber 201 and the housing, and the annular cavity includes an inner cavity and an outer cavity. The inner cavity is close to the outer wall of the measuring chamber 201, and the outer cavity is close to the inner wall of the housing. A plurality of support ribs are provided between the inner cavity and the outer cavity. The support ribs are evenly distributed along the circumference, and each support rib includes a radial portion and an axial portion, the radial portion is used to connect the inner cavity and the outer cavity, and the axial portion is used to enhance the support strength.

[0040] The oil inlet end of the measuring chamber 201 is provided with a conical transition section, the inner wall of which is tapered.

[0041] The transition section includes a main section and a guide section. The inner wall of the main section is tapered, and its cross-sectional area gradually decreases along the flow direction of the oil. The guide section is located at the entrance of the main section and is trumpet-shaped, which is used to pre-adjust the flow direction of the oil. The inner wall of the main section is provided with a plurality of spiral guide grooves, which are evenly distributed along the circumference, so that the oil can produce a rotational motion, which is conducive to eliminating the lateral velocity component.

[0042] The tapered structure of the main section can gradually increase the oil flow rate, reduce flow resistance, and avoid flow separation caused by sudden changes in cross section. The trumpet-shaped structure of the guide section can pre-adjust the flow direction of the oil, so that the oil enters the main section at a smaller incident angle, reducing the impact of the oil on the inner wall. The setting of the spiral guide groove can not only make the oil produce a predetermined rotational motion, but also separate impurities and bubbles in the oil through centrifugal force, thereby improving the accuracy of measurement.

[0043] The oil outlet end of the measuring chamber 201 is provided with an expansion section for reducing the oil flow rate and reducing the outlet turbulence.

[0044] The expansion section includes a first expansion portion, a transition portion, and a second expansion portion. The first expansion portion is directly connected to the measuring chamber 201, and its inner wall is gradually expanded, which is used to initially reduce the oil flow rate. The cross-sectional area of ​​the transition portion remains constant, which is used to stabilize the oil flow. The expansion angle of the second expansion portion is greater than that of the first expansion portion, which is used to further reduce the flow rate.

[0045] The inner wall of the expansion section is provided with a plurality of guide wings, the leading edge of which is at a certain angle to the oil flow direction, and the trailing edge is parallel to the oil flow direction. The guide wings can guide the oil to flow in the axial direction to prevent backflow. In addition, a rectifying grid is provided at the outlet of the expansion section to eliminate the residual rotational motion and restore the oil to the axial flow state.

[0046] This multi-stage expansion structure can make the oil flow rate reduction process smoother, effectively avoiding the backflow and vortex phenomenon that is easy to produce in the single-stage expansion structure. The small-angle expansion of the first expansion part can achieve the initial reduction of the oil flow rate, the equal-section design of the transition part provides a stable flow space for the oil, and the large-angle expansion of the second expansion part further reduces the flow rate. At the same time, the coordinated use of the guide wing and the rectifying grid ensures that the oil maintains a stable axial flow state at the outlet, effectively suppressing the generation of turbulence.

[0047] Through the above technical scheme, the tapered transition section at the oil inlet end can achieve a smooth transition of the oil and avoid flow separation caused by sudden changes in the cross section; the multi-stage expansion structure at the oil outlet end can effectively reduce the oil flow rate, reduce outlet turbulence, and ensure the stability of the flow state in the measurement space.

[0048] A plurality of guide ribs are arranged inside the measuring chamber 201. The guide ribs are evenly distributed along the circumference and are parallel to the axis of the chamber. The cross section of the guide ribs is streamlined to reduce the interference of the guide ribs on the flow of oil.

[0049] The inner wall of the measuring chamber 201 is provided with a plurality of groups of anti-bubble guides, which are used to prevent bubbles from being generated on the inner wall of the measuring chamber 201 during the flow of the oil. Each group of anti-bubble guides includes a main flow channel and a plurality of branch channels. The main flow channel extends along the circumference of the measuring chamber 201 and is arranged in a spiral shape. The spiral angle is adapted to the flow direction of the oil to guide the oil to flow along a predetermined path and avoid the generation of local eddies. The branch channel extends downstream from the main flow channel, and its cross-sectional area gradually decreases to form a gradual flow channel.

[0050] A smooth transition surface is provided between each set of anti-bubble guide parts, and the transition surface is treated with micro-convex and concave to form an air-repellent surface. The air-repellent surface is used to prevent bubbles from forming and gathering on the inner wall surface. A guide plate is provided at the entrance of the main flow channel, and the flow-facing surface of the guide plate is designed in an arc shape to reduce the impact of the oil and prevent the generation of bubbles. The trailing edge of the guide plate is parallel to the flow direction of the oil to ensure smooth flow of the oil.

[0051] In addition, the inner wall of the measuring chamber 201 is also provided with multiple groups of eddy current suppression sheets, which are located between adjacent anti-bubble guides. Each group of eddy current suppression sheets includes multiple micro guide strips, and the arrangement of the guide strips matches the flow characteristics of the oil to eliminate local eddy currents and prevent the generation of bubbles. Through this multi-level anti-bubble design, the influence of bubbles during the measurement process is effectively avoided, and the measurement accuracy is improved.

[0052] In the above technical solution, since a conical transition section and an expansion section are provided, the flow state of the oil in the measuring space can be ensured to be stable, thereby improving the measurement accuracy; since guide ribs and annular grooves are provided, the bubble interference problem can be effectively solved, thereby further improving the measurement reliability.

[0053] The surface roughness of the inner wall of the measuring chamber 201 is not greater than Ra0.4 micrometers to reduce turbulence when the oil flows.

[0054] A plurality of mounting holes are provided on the outer wall of the measurement chamber 201 for mounting the signal line interface and the temperature sensor 204 .

[0055] The measuring electrode assembly is arranged in the measuring chamber 201, including an inner electrode 203 and an outer electrode 202 arranged coaxially, and an annular measuring space is formed between the inner electrode 203 and the outer electrode 202. The inner electrode 203 is cylindrical, and a plurality of measuring surfaces are arranged on its outer surface, and a plurality of microelectrode arrays are evenly distributed on each measuring surface. The outer electrode 202 is cylindrical, and a plurality of microelectrode arrays are also arranged on its inner surface corresponding to the measuring surface position of the inner electrode 203. The microelectrode arrays of the inner and outer electrodes form a plurality of groups of measuring units, and each group of measuring units can independently collect conductivity signals.

[0056] The inner electrode 203 is fixed at the center of the measurement chamber 201 through a plurality of insulating support columns, one end of the support column is connected to the inner electrode 203, and the other end is connected to the inner wall of the measurement chamber 201. A signal transmission channel is provided inside each support column for transmitting the measurement signal. The outer electrode 202 is fixed to the inner wall of the measurement chamber 201 through a positioning ring, and a plurality of positioning grooves are provided on the positioning ring to ensure that the outer electrode 202 is coaxial with the measurement chamber 201.

[0057] The annular measurement space between the inner and outer electrodes is divided into several measurement spaces by multiple partitions, and each measurement space corresponds to a group of microelectrode arrays. The setting of the partitions can prevent signal interference between adjacent measurement spaces. In each measurement space, the microelectrode arrays are arranged in a specific manner to form a uniform electric field distribution. Through the collaborative work of multiple measurement spaces, more comprehensive measurement data can be obtained and the accuracy of the measurement can be improved.

[0058] The microelectrode arrays of the inner and outer electrodes work in an alternating excitation mode, that is, when one microelectrode array is used as an excitation electrode, the corresponding microelectrode array is used as a receiving electrode, and the conductivity of the oil is calculated by measuring the relationship between the excitation signal and the receiving signal. This alternating excitation mode can eliminate the influence of the electrode polarization effect and improve the measurement accuracy.

[0059] The measuring electrode assembly is arranged in the measuring chamber 201, and comprises a coaxially arranged inner electrode 203 and an outer electrode 202. The outer surface of the inner electrode 203 is provided with a plurality of annular protrusions 2031, which can optimize the electric field distribution.

[0060] These annular protrusions 2031 are arranged in sequence along the axial direction of the inner electrode 203. Each annular protrusion 2031 includes a main body and a transition part. The main body is in a circular ring shape, and its cross section is a trapezoid. The upper bottom surface of the trapezoid is connected to the surface of the inner electrode 203, and the lower bottom surface faces the outer electrode 202. The transition part is located on both sides of the main body and is a gradually curved surface, which is used to achieve a smooth transition with the surface of the inner electrode 203.

[0061] The spacing between adjacent annular protrusions 2031 gradually increases from the middle to the two ends of the inner electrode 203. This can compensate for the electric field distortion effect at the end. A plurality of arc grooves are also provided on the surface of each annular protrusion 2031, and these arc grooves are evenly distributed along the circumference of the annular protrusion 2031 to adjust the local electric field strength.

[0062] In order to further optimize the electric field distribution, the height of the annular protrusion 2031 gradually decreases from the middle of the inner electrode 203 to both ends. This can form a stepped electric field distribution and improve the uniformity of the measurement space. Reinforcement ribs are provided at the connection between the annular protrusion 2031 and the inner electrode 203 body, and these reinforcement ribs are distributed radially to enhance the structural strength and guide the flow of oil.

[0063] The main body of each annular protrusion 2031 is also provided with sensing electrodes, which are electrically insulated from the main body and are used to collect local electric field information. The sensing electrodes are connected to the signal processing unit 205 through internal signal lines to achieve real-time monitoring of the electric field distribution.

[0064] In the above technical solution, the uniform distribution of the electric field strength in the measurement space is achieved through the design of variable spacing and gradual height, thereby improving the measurement accuracy; the setting of the arc groove can refine and adjust the local electric field and reduce the influence of the edge effect; the setting of the reinforcement ribs not only ensures the structural strength, but also improves the flow state of the oil.

[0065] The outer electrode 202 adopts a segmented design, including a plurality of independent annular electrode units 2021, and adjacent electrode units are separated by insulating rings.

[0066] These annular electrode units 2021 are arranged along the axial direction, and each unit is an independent measurement unit. The annular electrode unit 2021 includes a main electrode layer and a shielding electrode layer. The main electrode layer is located on the inner side for actual measurement; the shielding electrode layer is located on the outer side for shielding external electric field interference.

[0067] Adjacent annular electrode units 2021 are electrically isolated and mechanically connected through insulating connection components such as positioning rings, insulating gaskets and locking pieces. The positioning rings are used to ensure coaxial alignment of adjacent electrode units, the insulating gaskets are used to provide electrical isolation, and the locking pieces are used to ensure connection reliability.

[0068] The annular protrusion 2031 of the inner electrode 203 and the annular electrode unit 2021 of the outer electrode 202 form a corresponding measurement area. The axial position of each annular protrusion 2031 coincides (concentrically aligned) with the center line of the corresponding annular electrode unit 2021. A fixed distance is maintained between the outer diameter of the annular protrusion 2031 and the inner diameter of the annular electrode unit 2021.

[0069] The upper surface of the main body of the annular protrusion 2031 is provided with a plurality of arc-shaped measuring electrodes, which are evenly distributed along the circumference. Each measuring electrode is connected to the signal processing unit 205 through an independent signal line. The inner surface of the corresponding annular electrode unit 2021 is also provided with a corresponding receiving electrode array. The measuring electrode and the receiving electrode form an independent measuring unit.

[0070] The insulating ring between the annular electrode units 2021 is stepped, including an inner step and an outer step. The inner step cooperates with the main electrode layer of the annular electrode unit 2021, and the outer step cooperates with the shielding electrode layer to form an electric field shielding structure. The axial width of the insulating ring corresponds to the spacing between the annular protrusions 2031.

[0071] There are multiple support wings evenly distributed along the circumference between the inner and outer electrodes. The cross section of the support wings is streamlined to minimize the impact on the flow of oil.

[0072] The inner electrode 203 is made of gold-plated stainless steel and is cylindrical. One end of the inner electrode 203 is electrically connected to the signal processing unit 205, and the other end is fixed by an insulating support. The insulating support is made of polytetrafluoroethylene.

[0073] The outer electrode 202 is also made of gold-plated stainless steel and is cylindrical. The outer electrode 202 is fixed in the measuring chamber 201 by insulating positioning rings at both ends, and the insulating positioning rings are made of polyetheretherketone. A gap of a predetermined distance (for example, 2 mm) is left between the outer surface of the outer electrode 202 and the inner wall of the measuring chamber 201 to form a reflux channel.

[0074] An annular measuring space is formed between the inner electrode 203 and the outer electrode 202, and the radial spacing of the measuring space is 5 mm. The surfaces of the inner and outer electrodes are precision polished, and the surface roughness is not greater than Ra0.2 microns, which can reduce the interference of the electrode surface on the flow of oil. The ends of the inner and outer electrodes are provided with 45-degree chamfers, which can reduce the turbulence phenomenon when the oil enters the measuring space.

[0075] The flow guiding member 206 is disposed at the oil inlet end of the annular measuring space, and is used to guide the oil entering the annular measuring space into a laminar flow state.

[0076] The flow guide member 206 includes a flow guide cover and a plurality of flow guide plates. The flow guide cover is made of stainless steel and is trumpet-shaped, with a large end diameter of 30 mm, a small end diameter of 20 mm, and a length of 25 mm. The inner surface of the flow guide cover is polished, and the surface roughness is not greater than Ra0.4 microns.

[0077] The guide vane is arc-shaped and made of stainless steel. Multiple (e.g., 8) guide vanes are evenly arranged along the inner wall of the guide cover. The flow-facing end of each guide vane is at an angle of 0 to 15 degrees to the flow direction of the oil, which can reduce the impact force of the oil and gradually transform the oil into a rotating flow. The tail end of the guide vane is parallel to the flow direction of the oil to form a stable laminar flow.

[0078] A straightening ring is provided at the connection between the guide cover and the measuring chamber 201. A plurality of through holes are evenly opened on the straightening ring, and the axes of these through holes are parallel to the flow direction of the oil. In this way, the rotating oil flow can be transformed into an axial laminar flow state. The straightening ring is made of polytetrafluoroethylene material. Since polytetrafluoroethylene material has good self-lubricating properties, it can reduce energy loss when the oil flows.

[0079] In addition, a protective net is provided outside the flow guide member 206. The protective net is made of a 100-mesh stainless steel wire mesh to filter large particles of impurities in the oil to prevent the impurities from clogging the flow guide member 206 or damaging the electrode.

[0080] The temperature compensation unit includes a temperature sensor 204 disposed in the annular measurement space, which is used to detect the oil temperature in real time and perform temperature compensation on the conductivity measurement value.

[0081] The temperature compensation unit also includes a temperature signal conditioning circuit and a temperature compensation processing circuit. The temperature sensor 204 is located in the middle of the outer electrode 202, passes through the wall of the outer electrode 202 through a sealed joint and extends into the measurement space. The sensing end of the temperature sensor 204 is in direct contact with the oil to collect the temperature data of the oil in real time.

[0082] The temperature sensor 204 is provided with a plurality of temperature measuring units at different positions of the outer electrode 202. The main temperature measuring unit is located in the middle of the outer electrode 202, passes through the wall of the outer electrode 202 through a sealing joint and extends into the measuring space.

[0083] The auxiliary temperature measuring units are evenly distributed along the axial direction of the outer electrode 202, and are used to monitor the temperature distribution in the measurement space. Each temperature measuring unit is used to collect temperature data in real time. The detection end of the temperature measuring unit is stepped.

[0084] The signals of all temperature measuring units are processed by the centralized data acquisition module, which uses time division multiplexing to read the data of each temperature measuring unit in turn.

[0085] The temperature signal conditioning circuit includes a signal amplifier and a filter. The signal amplifier is used to amplify the weak electrical signal output by the temperature sensor 204, and the filter is used to filter out interference noise in the temperature signal. The temperature signal conditioning circuit also includes a signal conversion module for converting an analog temperature signal into a digital signal.

[0086] The temperature compensation processing circuit includes a temperature characteristic function storage unit, a compensation coefficient calculation unit and a compensation value output unit.

[0087] The temperature characteristic function storage unit pre-stores the correction coefficient function of oil conductivity at different temperatures. This function establishes the corresponding relationship between temperature and correction coefficient by polynomial fitting, including linear terms, quadratic terms and high-order terms, to accurately describe the influence of temperature change on conductivity.

[0088] The compensation coefficient calculation unit obtains the corresponding correction coefficient from the temperature characteristic function according to the temperature value measured in real time. Specifically, the compensation coefficient calculation unit includes a temperature sampling module, a coefficient calculation module and an operation module. The temperature sampling module obtains the measurement value of the temperature sensor 204 according to the preset sampling period, and filters the measurement value to eliminate the fluctuation of the temperature signal. The coefficient calculation module substitutes the processed temperature value into the temperature characteristic function to calculate the correction coefficient at the current temperature. The operation module normalizes the correction coefficient to ensure the accuracy of the compensation calculation.

[0089] The compensation value output unit calculates the correction coefficient and the original conductivity measurement value to obtain the conductivity value after temperature compensation.

[0090] The compensation value output unit selects different compensation algorithms according to the amplitude of temperature change. When the temperature change amplitude is less than the preset threshold, linear compensation is adopted. Linear compensation adopts the first-order temperature coefficient model, and the compensated conductivity value σc is calculated by the following formula:

[0091] σc = σm[1 + α(T - T0)]

[0092] Where σm is the original conductivity measurement value, α is the temperature coefficient, T is the current measurement temperature, and T0 is the reference temperature.

[0093] When the temperature change is greater than or equal to the preset threshold, nonlinear compensation is used. Nonlinear compensation uses a polynomial model and obtains the compensation result through iterative calculation. Establish an n-order temperature characteristic polynomial:

[0094] σc = σm[1 + a1(T - T0) + a2(T - T0)² + ... + an(T - T0)ⁿ]

[0095] Among them, a1, a2, ..., an are temperature characteristic coefficients.

[0096] The iterative calculation process adopts a step-by-step approach. The specific steps are as follows:

[0097] In the first step, the initial compensation value σ1 is calculated using the first-order approximation:

[0098] σ1 = σm[1 + a1(T - T0)]

[0099] Where σm is the original conductivity measurement value, a1 is the first-order temperature coefficient, T is the current measurement temperature, and T0 is the reference temperature.

[0100] In the second step, the initial compensation value is substituted into the second-order term for correction to obtain σ2:

[0101] σ2 = σ1 + σm[a2(T - T0)²]

[0102] Where a2 is the second-order temperature coefficient.

[0103] The third step is to take into account the influence of the third-order term and obtain σ3:

[0104] σ3 = σ2 + σm[a3(T - T0)³]

[0105] Where a3 is the third-order temperature coefficient.

[0106] The fourth step is to take into account the influence of the fourth-order term and obtain σ4:

[0107] σ4 = σ3 + σm[a4(T - T0) 4 ]

[0108] Where a4 is the fourth-order temperature coefficient.

[0109] After each iteration, the relative error between two adjacent iteration results is calculated:

[0110] ε = |σn - σn-1| / σn-1

[0111] Among them, σn is the result of the current iteration, and σn-1 is the result of the previous iteration.

[0112] When the relative error ε is less than the pre-set convergence threshold, the iteration process ends. The convergence threshold is determined based on the following principle: when the relative error is less than one ten-thousandth, the iteration result can be considered to have reached a stable state, and the iteration value at this time is the final compensation result. If the relative error calculated for five consecutive iterations is greater than the convergence threshold, the exception handling mechanism is triggered and the compensation calculation is performed again.

[0113] In addition, the compensation value output unit automatically adjusts the compensation parameters according to the type of oil. When a change in the type of oil is detected, it automatically switches to the corresponding temperature characteristic function to ensure the applicability of the compensation calculation and effectively eliminate the impact of temperature changes on conductivity measurement.

[0114] The compensation value output unit includes an oil identification module, a parameter selection module and a compensation execution module. The oil identification module determines the type of oil by analyzing the change characteristics of the conductivity measurement value. When the conductivity value is in the first range, it is determined to be mineral oil, and the first-order temperature characteristic function is selected; when the conductivity value is in the second range, it is determined to be synthetic oil, and the second-order temperature characteristic function is selected; when the conductivity value is in the third range, it is determined to be mixed oil, and the third-order temperature characteristic function is selected.

[0115] The parameter selection module automatically adjusts the compensation parameters according to the identification results. For mineral oil, the temperature characteristic function is:

[0116] f1(T) = k1(T - T0)

[0117] Where k1 is the temperature coefficient of mineral oil.

[0118] For synthetic oil, the temperature characteristic function is:

[0119] f2(T) = k2(T - T0) + k3(T - T0)²

[0120] Among them, k2 and k3 are the first-order and second-order temperature coefficients of synthetic oil respectively.

[0121] For mixed oil, the temperature characteristic function is:

[0122] f3(T) = k4(T - T0) + k5(T - T0)² + k6(T - T0)³

[0123] Among them, k4, k5, and k6 are the first-order, second-order, and third-order temperature coefficients of the mixed oil, respectively.

[0124] The temperature compensation unit also includes a self-calibration module for regularly calibrating the temperature sensor 204 for zero point and range to ensure the accuracy of temperature measurement. The self-calibration module includes a reference temperature source and a comparator to correct the temperature measurement error by comparing with the reference temperature.

[0125] The signal processing unit 205 is electrically connected to the measuring electrode assembly and the temperature compensation unit, and is used to receive and process the measurement signal.

[0126] The signal processing unit 205 includes a signal acquisition module, a signal analysis module and a data output module. The signal acquisition module is electrically connected to the measuring electrode assembly and the temperature compensation unit, and is used to collect the conductivity measurement signal and the temperature signal between the electrodes. The signal acquisition module includes a multi-channel signal input interface to simultaneously collect multiple sensor signals.

[0127] The signal analysis module includes a signal preprocessing unit, a feature extraction unit and a judgment unit. The signal preprocessing unit amplifies, filters and performs analog-to-digital conversion on the collected original signal. The feature extraction unit extracts the conductivity characteristic value and temperature characteristic value from the processed signal. The judgment unit judges the oil quality status according to the extracted characteristic values.

[0128] The data output module includes a data storage unit and a communication interface unit. The data storage unit is used to record historical measurement data and analysis results. The communication interface unit supports multiple communication protocols and can interact with external control systems.

[0129] The signal processing unit 205 also includes a self-diagnosis module for monitoring the working state of the sensor. The self-diagnosis module can detect the electrode contamination degree parameter and send out an alarm signal when an abnormality is detected.

[0130] This technical solution guides the oil into a laminar flow state by providing a flow guide component 206 to reduce the generation of eddy currents, and eliminates the influence of temperature changes on the measurement accuracy through a temperature compensation unit, thereby improving the measurement accuracy of the conductivity sensor 20.

[0131] The conductivity sensor 20 provided in the present application transforms the turbulent oil into a laminar flow state through the flow guide member 206, thereby reducing the eddy current phenomenon in the measurement space, thereby reducing the interference of the flow state on the conductivity measurement. The flow guide member 206 is provided with a guide plate and a rectifying ring, which ensures that the oil forms a stable laminar flow field in the measurement space and improves the stability of the measurement signal.

[0132] The temperature compensation unit effectively eliminates the influence of temperature changes on conductivity measurement by real-time monitoring of oil temperature and performing compensation calculations.

[0133] The multi-level signal processing scheme adopted by the signal processing unit 205 improves the signal-to-noise ratio of the measurement signal, so that the conductivity sensor 20 of the present application can maintain a high measurement accuracy in the actual working environment of the oil transportation pipeline 10.

[0134] The conductivity sensor 20 of the present application sets a flow guide member 206 at the oil inlet end of the annular measurement space, and the flow guide member 206 guides the oil entering the annular measurement space into a laminar flow state. Since the laminar flow has the characteristics of stable flow and uniform velocity distribution, the eddy current phenomenon in the measurement space can be significantly reduced, thereby reducing the interference of the flow state on the conductivity measurement. In addition, the inner electrode 203 and the outer electrode 202 of the conductivity sensor 20 of the present application are coaxially arranged to form an annular measurement space, so that the electric field distribution can be made more uniform, further improving the measurement accuracy of the conductivity sensor 20 in the oil product delivery pipeline 10.

[0135] The conductivity sensor 20 of the present application also has a temperature sensor 204 disposed in the annular measurement space, and the temperature compensation unit monitors the oil temperature in real time and performs compensation calculations, thereby effectively eliminating the influence of temperature changes on the conductivity measurement and making the final output conductivity value more accurate.

[0136] The embodiments of the present application are described in detail above, and the contents of this specification should not be construed as limiting the scope of protection of the present application.

Claims

1. A conductivity sensor for oil quality monitoring, characterized in that: include: A sensor body, the sensor body comprising a tubular housing and a measuring chamber disposed in the tubular housing; A measuring electrode assembly, the measuring electrode assembly is arranged in the measuring chamber, and comprises an inner electrode and an outer electrode arranged coaxially, and an annular measuring space is formed between the inner electrode and the outer electrode; A flow guiding member, which is arranged at the oil inlet end of the annular measuring space and is used to guide the oil entering the annular measuring space into a laminar flow state; a temperature compensation unit, the temperature compensation unit comprising a temperature sensor disposed in the annular measurement space; as well as a signal processing unit, the signal processing unit being electrically connected to the measuring electrode assembly and the temperature compensation unit; The axis of the measuring chamber coincides with the axis of the tubular housing, and an annular cavity is provided between the measuring chamber and the tubular housing; The measuring chamber comprises: An oil inlet end, wherein the oil inlet end is provided with a tapered transition section; as well as An oil outlet end, wherein the oil outlet end is provided with an expansion section; A plurality of guide ribs are arranged inside the measuring chamber, the guide ribs are evenly distributed along the circumference and are parallel to the axis of the measuring chamber, and the cross section of the guide ribs is streamlined; The inner wall of the measuring chamber is provided with a plurality of annular grooves.

2. The conductivity sensor according to claim 1, characterized in that: A plurality of annular protrusions are arranged on the outer surface of the inner electrode, and the annular protrusions are arranged in sequence along the axial direction of the inner electrode.

3. The conductivity sensor according to claim 2, characterized in that Each of the annular protrusions comprises: A main body, the main body is in a circular ring shape, and its cross section is a trapezoid; and A transition portion is located at two sides of the main body.

4. The conductivity sensor according to claim 3, characterized in that: The spacing between adjacent annular protrusions gradually increases from the middle of the inner electrode to both ends, and the height of the annular protrusions gradually decreases from the middle of the inner electrode to both ends.

5. The conductivity sensor according to claim 4, characterized in that: The surface of each annular protrusion is provided with a plurality of arc grooves evenly distributed along the circumferential direction.

6. The conductivity sensor according to claim 1, characterized in that: The outer electrode comprises a plurality of annular electrode units arranged along the axial direction, and adjacent annular electrode units are separated by insulating rings; Each of the annular electrode units comprises: a main electrode layer, the main electrode layer being located on the inner side; and The shielding electrode layer is located on the outside.

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