An apparatus and method for measuring the phase holdup of a high-pressure pipeline using a double-ring probe

Abstract

The present invention discloses a device and method for measuring the phase holdup of a high-pressure pipeline through a double-ring probe. The present invention accurately reflects the variation characteristics of the phase holdup of the multiphase fluid in the high-pressure pipeline and realizes non-intrusive non-contact measurement. Specifically, the double-ring electrode is sealed in the intermediate connection section through a high-pressure sealing structure. The lead electrode leads out the signal of the double-ring electrode and realizes insulation and high-pressure sealing with the housing. The method is to first obtain the relationship curve between the double-ring electrical signal and the phase holdup through high-pressure calibration. A high-frequency alternating voltage is applied to the double-ring electrode, and the phase holdup signal is recorded and displayed through a processing circuit and a data acquisition system. The device proposed by the present invention simultaneously solves the problems of sealing and insulation for high-pressure phase holdup measurement; establishes a high-pressure calibration method; realizes the functional integration of the measurement device and the instrument; has the advantages of compact structure, no interference with the internal flow, flexible application occasions, etc., and is convenient to be installed and used at various positions of the high-pressure pipeline.

Description

Technical Field

[0001] The present invention belongs to the field of measurement of multiphase flow phase parameters, and specifically relates to a device and method for measuring phase holdup using a double-ring probe in a high-pressure pipeline. Background Art

[0002] Multiphase flow phenomena widely exist in nature and industrial sites, such as industrial fields like petroleum, chemical engineering, and aerospace. The flow of multiphase flow in pipes is complex and variable, and exhibits different flow patterns under different combinations of flow parameters, such as bubbly flow, slug flow, stratified flow, and annular flow. Different flow patterns and phase parameters show obvious differences in aspects such as pipeline flow resistance, heat transfer characteristics, and pressure pulsation. Therefore, the accurate and real-time measurement of local pipeline phase parameters is of great significance for multiphase flow research and theory establishment. On the other hand, to ensure the efficient transportation of multiphase fluids, the pressure parameters of actual industrial pipelines are relatively high, and even reach the megapascal level in deep-sea oil and gas production and transportation pipelines. In practical applications, a low-cost and fast-response phase holdup measurement device is of great significance in on-site monitoring of industrial pipelines and scientific research.

[0003] Many studies use electrical, thermal, acoustic, and optical means to reflect the phase holdup information through other physical quantities. Among them, the electrical method is low-cost, fast-response, and has little interference to the flow, and has received extensive attention. The annular conductance probe applied to circular pipes has the advantage of non-contact measurement and has no interference to the flow inside the pipe, but there is no reported probe method and technology applicable to high-pressure pipelines. The insulation of the probe and pipeline sealing under high-pressure conditions are key issues. In addition, it is particularly crucial to obtain the mapping relationship between the phase holdup and the corresponding electrical signal under high-pressure conditions. Through structural design, the above key issues are solved, a calibration method from atmospheric pressure to high pressure is proposed, and an integrated device for measuring the phase holdup of high-pressure pipelines with on-line display and remote transmission is developed. Summary of the Invention

[0004] The purpose of the present invention is to provide a device and method for measuring phase holdup using a double-ring probe applicable to high-pressure conditions. Using this device and method, under the excitation of a high-frequency alternating voltage, the conductive fluid exhibits obvious impedance characteristics. By using the difference in the conductivity of the multiphase fluid between the two rings of the double-ring conductance probe, the magnitude and change of the phase holdup are reflected through the conductivity. Combining with the calibration curve at the corresponding pressure and temperature, the phase holdup of the multiphase fluid can be accurately and real-time measured. In addition, the electrode structure of this device is the same as the pipeline diameter and has no interference to the fluid flow inside the pipe. This device simultaneously realizes high-pressure sealing and electrical insulation, expanding the application scope of the electrical method in high-pressure multiphase flow pipelines.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A device for measuring the phase holdup of a high-pressure pipeline through a double-ring probe, including main structural parts such as a compression flange and an intermediate connection section connected in sequence, a signal processing and acquisition part such as a processing circuit, a voltage-current conversion module, and an acquisition module. Among them, a pair of compression flanges are arranged on both sides of the intermediate connection section and are connected by fasteners. The annular probe electrodes and the insulating sealing gaskets are installed in two symmetric annular gaps between the intermediate connection section and the compression flanges. The wiring electrodes, sealing bolts, insulating sealing sleeves, and insulating sealing pipes are all installed inside two vertical bolt holes of the intermediate connection section. The thermocouple and the pressure sensor are located in the middle position between the two compression flanges. The wiring electrodes are successively connected to the processing circuit and the voltage-current conversion module. The signal lines of the thermocouple, the pressure sensor, and the voltage-current conversion module are connected to the acquisition module and then connected to the display instrument. The high-pressure calibration air inlet valve and the high-pressure calibration drain valve are arranged opposite to each other on the upper and lower sides of the compression flanges.

[0007] Further, the two insulating sealing gaskets and the annular probe electrodes inside the intermediate connection section have the same inner and outer diameters and are stacked and combined to form a three-layer sealed insulating structure of "gasket - probe - gasket".

[0008] Further, the compression flange and the intermediate connection section are sealed with an O-ring, and the concentricity is ensured by the mating of the spigot.

[0009] Further, the wiring electrode is inserted into the insulating sealing sleeve, and the two are inserted into the sealing bolt. The insulating sealing sleeve is located at the bottom of the sealing bolt, and the insulating sealing sleeve relies on the deformation caused by the extrusion of the bolt to achieve external insulation and sealing of the wiring electrode.

[0010] Further, the top of the annular probe electrode has a threaded port and is threadedly connected to the bottom of the wiring electrode to lead out the electrical signal.

[0011] A method for measuring the phase holdup of a high-pressure pipeline through a double-ring probe includes the following steps:

[0012] Step 1, determine the high-pressure calibration curve of the current signal output by the wiring electrode through the processing circuit and the voltage-current conversion module and the phase holdup through the high-pressure calibration method. The high-pressure calibration pressure range is 6 - 30 MPa.

[0013] Step 2, connect the device to the high-pressure pipeline through the compression flanges at both ends. The multiphase medium in the pipeline needs to have an obvious conductivity difference, and keep the high-pressure calibration air inlet valve and the high-pressure calibration drain valve closed.

[0014] Step 3, connect the wiring electrode to the processing circuit. The processing circuit applies a sine wave excitation voltage of 20 - 100 kHz and 5 V. The processing circuit outputs a DC voltage of 0 - 5 V and outputs a standard signal of 4 - 20 mA through the voltage-current conversion module.

[0015] Step 4: Connect the above current signal, pressure sensor, and thermocouple signals to the acquisition module for collection. Calculate the corresponding phase holdup using the high-pressure calibration curve from step 1, and connect the display to record and display the phase holdup in real time.

[0016] A calibration method for measuring phase holdup in a high-pressure pipeline using a double-ring probe, obtaining a mapping relationship between a high-pressure static calibration electrical signal and the phase holdup in the pipeline, includes the following steps:

[0017] Step 1: Fill the device with water and adjust the level, then press the flanges tightly to seal.

[0018] Step 2: The high-pressure calibration air inlet valve is connected to the high-pressure gas cylinder, and the high-pressure gas cylinder is adjusted to the required calibration pressure.

[0019] Step 3: Open the high-pressure calibration drain valve, drain the specified amount of water according to the calibration point, and then close the drain valve.

[0020] Step 4: Connect a scale to the bottom of the drain valve. Once the valve stabilizes, record the dual-loop current signal and the mass of the discharged water to calculate the corresponding phase holdup within the device. Maintain constant pressure within the device during this process.

[0021] Step 5: Repeat steps 3 and 4 until the calibration is completed.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The present invention proposes a device and method for real-time online measurement of phase content in a high-pressure pipeline using a double-ring conductivity probe. First, the device ensures the sealing and electrical insulation of the phase content measurement process in the high-pressure pipeline through the designed multi-layer sealing structure, realizing the innovative application of electrical probes in high-pressure parameter pipelines. Secondly, based on the difference in impedance characteristics of high-frequency voltage signals for multiphase fluids, the electrical method has the advantages of fast response to phase content changes, good real-time performance, and accurate reflection of the time-frequency characteristics of the flow type. Thirdly, the double-ring probe inside the device has the same diameter as the inner diameter of the pipeline and does not interfere with the flow in the pipe. In addition, a calibration method from normal pressure to high pressure is proposed to map the current signal to the corresponding phase content, and the signal processing circuit is reasonably designed to ensure that the mapping relationship has good linearity and repeatability. Finally, the device has a simple structure, is non-radioactive, low cost, good versatility, is easy to disassemble and replace, and can be installed at any required position in the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of a device for measuring phase content in high-pressure pipelines using a double-ring probe.

[0025] Figure 2 This is the signal processing principle diagram of the device of the present invention

[0026] Figure 3Schematic diagram of the calibration method for the device of measuring the phase holdup in high-pressure pipelines by a double-ring probe according to the present invention

[0027] Figure 4 Calibration curves of measuring the phase holdup by the device under different pressures

[0028] Figure 5 Curve graph of measuring the real-time change of the phase holdup by the device Specific implementation manners

[0029] The present invention will be further described in detail below with reference to the accompanying drawings:

[0030] See Figure 1 , for the device of measuring the phase holdup in high-pressure pipelines by a double-ring probe according to the present invention, firstly in terms of structural design, the pipe wall thickness, flange and fastener specifications are reasonably determined according to the actual operating pressure of the pipeline. For a pressure of 30 MPa, the outer diameter of the pipeline is 60 mm and the wall thickness is 7 mm. The compression flange and the middle section are made of 304 stainless steel. The key to measuring the phase holdup by the double-ring probe under high-pressure conditions lies in high-pressure sealing and electrical insulation. Firstly, a "sandwich" structure is formed by using a pair of annular PTFE gaskets and a brass annular probe to achieve insulation from the housing. In addition, the bottom of the wiring electrode is connected to the copper electrode thread to lead out the electrical signal. The wiring electrode is inserted into the insulating sealing sleeve, and both are inserted into the sealing bolt. The sealing insulating sleeve is made of polytetrafluoroethylene and is located at the bottom of the sealing bolt, and relies on deformation to achieve sealing and external insulation of the wiring electrode.

[0031] See Figure 2 , for the method of measuring the phase holdup in high-pressure pipelines by a double-ring probe according to the present invention, the real-time change of the phase holdup in the high-pressure pipeline is converted into an electrical signal by the double-ring probe under high-frequency voltage excitation. The electrical signal is input into the processing circuit, and the processing circuit amplifies, rectifies and filters the high-frequency voltage signal to convert it into a DC voltage signal of 0-5V. For the convenience of long-distance transmission, the above voltage signal is converted into a standard current signal of 4-20 mA. The pressure sensor, thermocouple and double-ring electrical signal are synchronously input into the signal processing module, and are displayed in real time through the display and collected remotely by the computer.

[0032] See Figure 3 , the method of measuring the phase holdup in high-pressure pipelines by a double-ring probe according to the present invention further includes obtaining the mapping relationship between the phase holdup and the electrical signal under high-pressure conditions, which is specifically completed through calibration experiments under different pressure parameters. The equipment and devices required for calibration are as Figure 3As shown, there are a 15 high-pressure gas cylinder, a 16 inlet valve, a 17 double-ring probe measurement section, an 18 pressure sensor, a 19 signal processing and acquisition circuit, a 20 display, a 21 high-pressure water pump, a 22 inlet valve, a 23 drain valve, a 24 measuring cup, and a 25 weighing scale. The high-pressure double-ring structure is connected to the high-pressure gas cylinder and the high-pressure water pump through a high-pressure regulating valve in sequence. The total volume inside the device tube is obtained through structural design. The device is filled with water, sealed at both ends and adjusted to be horizontal. Open the high-pressure gas-phase regulating valve to make the pressure inside the device consistent with that of the high-pressure gas cylinder. Open the lower drain valve, and according to the calibration points, drain some water and then close the drain valve. After stabilization, record the voltage and the weight of the drained water, and calculate the corresponding phase holdup inside the tube. Repeat the above steps until the inside of the device reaches an empty tube. According to the data obtained above, obtain the one-to-one correspondence between the static liquid holdup inside the tube and the electrical signal.

[0033] The innovative method of the present invention is mainly reflected in that the proposed device and method can be applied to high-pressure pipelines for non-intrusive real-time measurement and display of phase holdup. To ensure stable operation under high-pressure parameter conditions, a "three-stage" sealing structure is reasonably designed to ensure no leakage of internal high-pressure multiphase fluids. In addition, through the deformation of the sealing material, insulation is formed between the wiring electrode and the housing, realizing the extraction and acquisition of electrical signals inside the high-pressure pipeline. The signal is amplified by a self-made amplifier circuit and converted into a standard current signal, and is displayed in real time to meet the requirements of remote signal transmission and acquisition. A calibration method and key steps for double-ring probes under high pressure are proposed to accurately obtain the mapping relationship between phase holdup and electrical signals under different pressure and temperature parameters. The device of the present invention adopts a modular design, with a simple structure, easy to disassemble and assemble, and good versatility.

[0034] Example 1: Measurement and calibration of the phase holdup of the device under different pressure conditions

[0035] According to the phase holdup calibration method of the present invention described above, calibration experiments can be realized from low pressure to high pressure conditions. As Figure 4 shown, the corresponding relationship between dimensionless conductivity and liquid holdup at pressure parameters of 0.1, 0.5, 1.5, 4.5, and 9 MPa is specifically given. It can be seen from the calibration curve that the influence of pressure on the calibration curve is relatively small, and multiple groups of experimental data points basically coincide. At the same time, for the liquid holdup in the range of 0.2 - 1, there is a good linear relationship between dimensionless conductivity and liquid holdup. The calibration curve is less sensitive to changes in pressure parameters, which is beneficial to improving the stability and accuracy of measurement.

[0036] Example 2: Actual measurement of the phase holdup signal curve

[0037] Using the above device, at an inlet pressure of 0.5 MPa, when the apparent liquid velocity is 4.18 m / s and the apparent gas velocities are 0.22 m / s and 1.08 m / s respectively, on-line real-time measurement of the phase holdup of the device is carried out. The specific results are as Figure 5As shown, the sampling frequency of the phase holdup signal is 1 kHz, the liquid phase is tap water, and the gas phase is air. It can be seen from the figure that the device can significantly and rapidly characterize the change of the phase holdup. When the superficial gas velocity is low, the flow pattern in the pipe is bubbly flow with relatively uniform gas-liquid distribution, and the amplitude of the phase holdup signal fluctuation is small; when the superficial gas velocity increases, the gas and liquid gradually separate, small bubbles merge into large bubbles, the fluctuation frequency decreases, and the fluctuation amplitude increases. The device of the present invention can accurately reflect the dynamic change process of the local phase holdup.

[0038] It should be noted that the above-described embodiments are only some examples that can be realized based on the device and method of the present invention. The present invention is not limited to these embodiments. Any equivalent transformation of the technical solution of the present invention adopted by those of ordinary skill in the art by reading the specification of the present invention is covered by the claims of the present invention.

Claims

1. An apparatus for measuring the phase holdup of a high-pressure pipeline using a double-ring probe, characterized in that, It includes a main structure part composed of a compression flange (1) and an intermediate connection section (4) connected in sequence, a signal processing and acquisition part of a processing circuit (8), a voltage-current conversion module (9) and an acquisition module (10). Among them, a pair of compression flanges (1) are arranged on both sides of the intermediate connection section (4) and are connected by fasteners (5). An annular probe electrode (16) and an insulating sealing gasket (15) are installed in two symmetric annular gaps between the intermediate connection section (4) and the compression flange (1). A wiring electrode (12), a sealing bolt (13), an insulating sealing sleeve (14) and an insulating sealing tube (18) are installed together inside two vertical bolt holes of the intermediate connection section (4). A thermocouple (3) and a pressure sensor (7) are located in the middle position between the two compression flanges. The wiring electrode (12) successively connects the processing circuit (8) and the voltage-current conversion module (9). The signal lines of the thermocouple (3), the pressure sensor (7) and the voltage-current conversion module (9) are connected to the acquisition module (10) and then connected to a display instrument (11). A high-pressure calibration intake valve (2) and a high-pressure calibration drain valve (6) are arranged opposite to each other on the upper and lower sides of the compression flange. The two insulating sealing gaskets and the annular probe electrode inside the intermediate connection section maintain the same inner and outer diameters and are stacked and combined to form a three-layer sealed insulation structure of "gasket-probe-gasket". The wiring electrode is inserted into the insulating sealing sleeve, and the two are inserted into the sealing bolt. The insulating sealing sleeve is located at the bottom of the sealing bolt. The insulating sealing sleeve relies on the extrusion deformation of the bolt to achieve the external insulation and sealing of the wiring electrode.

2. The device for measuring the phase holdup of a high-pressure pipeline by means of a double-ring probe according to claim 1, characterized in that The compression flange and the intermediate connection section are sealed with an O-ring, and the concentricity is ensured by the mating of the spigot.

3. The device for measuring the phase holdup of a high-pressure pipeline by using a double-ring probe according to claim 1, characterized in that, The top of the annular probe electrode has a threaded port and is threadedly connected to the bottom of the wiring electrode to lead out the electrical signal.

4. The method for a device for measuring the phase holdup of a high-pressure pipeline through a double-ring probe according to claim 1, characterized in that, It includes the following steps: Step 1: Determine the high-pressure calibration curve of the current signal output by the wiring electrode through the processing circuit and the voltage-current conversion module and the phase fraction through the high-pressure calibration method. The high-pressure calibration pressure range is 6 - 30 MPa. Step 2: The device is connected to the high-pressure pipeline through the compression flanges at both ends. The multiphase medium in the pipeline needs to have an obvious conductivity difference, and the high-pressure calibration intake valve and the high-pressure calibration drain valve are kept closed. Step 3: The wiring electrode is connected to the processing circuit. The processing circuit applies a sine wave excitation voltage of 20 - 100 kHz and 5 V. The processing circuit outputs a DC voltage of 0 - 5 V and outputs a standard signal of 4 - 20 mA through the voltage-current conversion module. Step 4: Connect the above current signal, the signals of the pressure sensor and the thermocouple to the acquisition module for acquisition, calculate the corresponding phase fraction through the high-pressure calibration curve in Step 1, and connect to the display instrument for phase fraction recording and real-time display. To obtain the high-pressure calibration curve of the double-ring electrical signal and the phase fraction in the high-pressure pipeline, it specifically includes the following steps: 1) Fill the device with water and adjust the level, and seal both ends of the compression flange. 2) Connect the high-pressure calibration intake valve to the high-pressure gas cylinder, and adjust the high-pressure gas cylinder to the required calibration pressure. 3) Open the high-pressure calibration drain valve, and drain a specified amount of water according to the calibration points and then close the drain valve. 4) The bottom of the drain valve is connected to a weighing scale. After stabilization, record the double-loop current signal and the mass of the discharged water, and calculate the corresponding phase holdup in the device while keeping the pressure in the device constant during the process; 5) Repeat steps 3) and 4) until the calibration is completed.

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