An ultrasonic- and radio-frequency-based gas-liquid two-phase flow measurement system and method

Abstract

The present invention provides an ultrasonic- and radio-frequency-based gas-liquid two-phase flow measurement system and method, which includes a measurement pipe section, a battery, and a measurement circuit. The measurement pipe section includes an ultrasonic sensor and a radio-frequency antenna. The battery is used to supply power to the measurement circuit. The ultrasonic sensor and the radio-frequency antenna are electrically connected to the measurement circuit. The measurement circuit is used to adjust the voltage of the battery and then supply power to the ultrasonic sensor and the radio-frequency antenna, and to determine the fluid type based on the output signals of the ultrasonic sensor and / or the radio-frequency antenna and calculate the gas flow rate, the liquid flow rate, and the total flow rate. The ultrasonic- and radio-frequency-based gas-liquid two-phase flow measurement system provided by the present invention, through the ultrasonic sensor, the radio-frequency antenna, and the measurement circuit, realizes the measurement of the separated-phase flow rates and the total flow rate of any gas-liquid ratio during the entire blowout process of a gas well, directly connected in series to the blowout pipeline without gas-liquid separation.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas field production metering, and particularly relates to a gas-liquid two-phase flow measurement system and method based on ultrasonic wave and radio frequency. Background Art

[0002] The process of fracturing fluid backflow after the fracturing of gas well 47 is divided into three stages: the initial stage, the middle stage and the late stage.

[0003] In the initial stage of fracturing fluid backflow, the fluid backflowed mainly includes the liquid in the formation in the wellbore. In the middle stage of liquid drainage, all the original liquid in the wellbore has been drained out. The fluid drained from the formation is sometimes liquid, sometimes gas, and sometimes a gas-liquid mixed fluid, and the gas-liquid ratio is uncertain, that is, it may be all water, may be all gas, or may be a mixed fluid with any gas-water ratio, and the three states of all gas, all water or gas-liquid mixture may appear alternately. When the drained fluid is a gas-liquid mixed fluid, its flow pattern is turbulent flow. In the late stage of liquid drainage, gas well 47 is close to the normal production process, and the drained fluid is mainly gas, but it does not rule out the presence of a certain amount of liquid.

[0004] The existing measurement methods for the backflow fluid are as follows: one is the estimation method. For the liquid entering the discharge pool, the discharged liquid volume is estimated according to the geometric shape and size of the sewage discharge pool, and the gas is ignited and burned. That is, the gas is not estimated, and the liquid discharge volume is estimated according to the liquid discharge time and the geometric shape and size of the sewage discharge pool, and accurate measurement cannot be achieved. The other is the separation method. First, a separator is used to separate the gas and the liquid, then the flow rates of the separated gas and liquid are measured respectively, and finally the total flow rate is obtained.

[0005] The first method mentioned above cannot obtain the gas emission volume nor the total gas-liquid flow rate, and the measurement of the liquid can only be an estimation; the problem with the second method is that a special separation device is required, the equipment is huge, the transportation is difficult, the cost is expensive, the construction is complex, and the operation cost is high. Summary of the Invention

[0006] The purpose of the present invention is to provide a gas-liquid two-phase flow measurement system based on ultrasonic wave and radio frequency, so as to overcome the above-mentioned technical problems existing in the prior art.

[0007] Another purpose of the present invention is to provide a gas-liquid two-phase flow measurement method based on ultrasonic wave and radio frequency, which is directly connected in series to the blowout pipeline without gas-liquid separation and is suitable for measuring the separated-phase flow rate and total flow rate of any gas-liquid ratio during the whole process of gas well blowout.

[0008] For this reason, the technical solution provided by the present invention is as follows:

[0009] A gas-liquid two-phase flow measurement system based on ultrasonic and radio frequency, comprising a measurement pipe section, a battery and a measurement circuit. The measurement pipe section includes an ultrasonic sensor and a radio frequency antenna. The battery is used to supply power to the measurement circuit. The ultrasonic sensor and the radio frequency antenna are electrically connected to the measurement circuit. The measurement circuit is used to adjust the voltage of the battery and supply power to the ultrasonic sensor and the radio frequency antenna, and to judge the fluid type according to the output signals of the ultrasonic sensor and / or the radio frequency antenna and calculate the gas flow rate, liquid flow rate and total flow rate.

[0010] The measurement pipe section includes an ultrasonic sensor, a radio frequency antenna, an inner pipe and an outer protection pipe. The outer protection pipe is arranged outside the inner pipe. There are two pairs of ultrasonic sensors and they are arranged crosswise. The two pairs of ultrasonic waves are the first ultrasonic sensor and the second ultrasonic sensor, the third ultrasonic sensor and the fourth ultrasonic sensor respectively. Among them, the frequency of the first pair of ultrasonic sensors is suitable for propagation in liquid, and the frequency of the second pair of ultrasonic sensors is suitable for propagation in gas. There are two radio frequency antennas, namely the first radio frequency antenna and the second radio frequency antenna respectively.

[0011] The first radio frequency antenna, the second radio frequency antenna and the ultrasonic sensor are sequentially arranged on the inner pipe along the fluid flow direction. The straight line where the first ultrasonic sensor and the second ultrasonic sensor are located intersects the axis of the inner pipe, and the included angle with the axis is 35°-55°. The straight line where the third ultrasonic sensor and the fourth ultrasonic sensor are located intersects the axis of the inner pipe, and the included angle with the axis is 125-145°. The straight line one and the straight line two intersect the axis at the same point.

[0012] The inner pipe includes a right transition pipe, a radio frequency antenna installation pipe, an ultrasonic sensor installation body and a left transition pipe which are sequentially connected along the fluid direction.

[0013] The first radio frequency antenna and the second radio frequency antenna are both installed perpendicular to the axis, and the distance between the first radio frequency antenna and the second radio frequency antenna is 1-8 cm.

[0014] The frequencies of the first ultrasonic sensor and the second ultrasonic sensor are both 500 kHz-2 MHz, and the frequencies of the third ultrasonic sensor and the fourth ultrasonic sensor are both 20 kHz-200 kHz.

[0015] The right transition pipe is connected to one end of the outer protection pipe through a right connecting pipe and a right plug. The left transition pipe is connected to the other end of the outer protection pipe through a left connecting pipe and a left plug.

[0016] A gas-liquid two-phase flow measurement method based on ultrasonic and radio frequency, using a gas-liquid two-phase flow measurement system based on ultrasonic and radio frequency. When the fluid flows through the measurement pipe section, two radio frequency antennas and / or two pairs of ultrasonic sensors output signals to the measurement circuit. The measurement circuit determines the fluid type based on the signals and calculates the gas flow rate, liquid flow rate, and total flow rate.

[0017] The fluid types include liquid, gas, and gas-liquid mixture;

[0018] When the signal amplitude obtained by transmitting at one end and receiving at the other end of the first radio frequency antenna or the second radio frequency antenna is 1.2 - 1.8V, the measurement circuit determines that the fluid is liquid. Then the measurement circuit obtains the flow velocity through the time difference of the signals received by each other of the first pair of ultrasonic sensors, and finally calculates the liquid flow rate;

[0019] When the signal amplitude obtained by transmitting at one end and receiving at the other end of the first radio frequency antenna or the second radio frequency antenna is 0.3 - 0.6V, the measurement circuit determines that the fluid is gas. Then the measurement circuit obtains the flow velocity through the time difference of the signals received by each other of the second pair of ultrasonic sensors, and finally calculates the gas flow rate;

[0020] When both pairs of ultrasonic sensors have no response when the fluid passes by, the measurement circuit determines that the fluid is gas-liquid mixture. Then the measurement circuit takes the average value of the gas content rate or liquid content rate measured by the two radio frequency antennas, and then obtains the time taken to pass through the two radio frequency antennas according to the correlation function of the signals received by the two radio frequency antennas. The flow velocity is obtained based on the time and distance, and finally the total flow rate, gas flow rate, and liquid flow rate are calculated.

[0021] The time difference of the signals received by each other of the first pair of ultrasonic sensors is Δt;

[0022] Among them, the time when the first ultrasonic sensor transmits and the second ultrasonic sensor receives is The time when the second ultrasonic sensor transmits and the first ultrasonic sensor receives is Then the time difference

[0023] In the formula, υ is the flow velocity, m / s; c is the propagation velocity of ultrasonic waves in the medium. For gas, c is 340m / s, and for water, c is 1480m / s; D is the inner diameter of the pipe, m; α is the angle between the straight line where the two pairs of ultrasonic sensors are located and the axis.

[0024] The correlation function of the signals received by the two radio frequency antennas is:

[0025]

[0026] Where x(t) is the signal received by the first RF antenna; y(t) is the signal received by the second RF antenna; T is the length of the time period, in s; τ is the time corresponding to the maximum value of Rxy obtained by cross-correlation operation, in s; t is the integration variable, in s.

[0027] The beneficial effects of the present invention are:

[0028] The gas-liquid two-phase flow measurement system based on ultrasonic and RF provided by the present invention realizes the measurement of the separated phase flow rate and the total flow rate that are directly connected in series to the blowout prevention pipeline and suitable for any gas-liquid ratio during the whole process of gas well blowout through ultrasonic sensors, RF antennas and measurement circuits without gas-liquid separation.

[0029] When the conventional gas-liquid separation metering method is used for flowing well on the well site without power electricity, not only a dedicated power system needs to be erected, but also the separator has a large power consumption and weighs dozens of tons, and the construction processes such as transportation and connection to the blowout prevention pipeline are complex. The present invention uses a battery to supply power to the measurement system, with a weight within 100 kg, no longer requiring power electricity, being light in weight and convenient for transportation. The whole set of system is connected to the blowout prevention pipeline through threads, with convenient construction, and can measure the flow rate of full liquid, full gas and mixed fluid with any gas-liquid ratio.

[0030] To make the above content of the present invention more obvious and understandable, the following specifically gives preferred embodiments and, in conjunction with the accompanying drawings, makes a detailed description as follows. Description of the Drawings

[0031] Figure 1 is the structural schematic diagram of the present invention;

[0032] Figure 2 is the structural diagram of the measurement pipe section.

[0033] In the figure:

[0034] Description of the reference numerals in the drawings:

[0035] 1. Left connecting pipe; 2. Left plug; 3. Outer protection pipe; 4. Left transition pipe; 5. Ultrasonic sensor mounting body; 6. First RF antenna; 7. RF antenna mounting pipe; 8. Right transition pipe; 9. Right plug; 10. Fourth lead-out end; 11. Right connecting pipe; 12. Second RF antenna; 13. First ultrasonic sensor; 14. First weld seam; 15. Fixing screw; 16. First sealing ring; 17. Thread; 18. Second sealing ring; 19. Third lead-out end; 20. Third sealing ring; 21. Second ultrasonic sensor; 22. Third ultrasonic sensor; 23. Fourth sealing ring; 24. First positioning pin; 25. Second positioning pin; 26. Fifth sealing ring; 27. Fourth ultrasonic sensor; 28. First sealing needle; 29. Sixth sealing ring; 30. Third positioning pin; 31. Pin; 32. Cable outlet; 33. Second weld seam; 34. Second sealing needle; 35. Third sealing needle; 36. Seventh sealing ring; 37. Fourth positioning pin; 38. Fourth sealing needle; 39. First lead-out end; 40. Second lead-out end; 41. Eighth sealing ring; 42. Measuring pipe section; 43. Battery; 44. Measuring circuit; 45. Wireless transmitter; 46. Remote wireless receiver; 47. Gas well; 48. Collection device. Detailed implementation mode

[0036] The following specific embodiments illustrate the implementation mode of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0037] It should be noted that in the present invention, the up, down, left, and right in the figure are regarded as the up, down, left, and right of the gas-liquid two-phase flow measurement system based on ultrasonic and RF in this specification.

[0038] Now refer to the accompanying drawings to introduce the exemplary implementation mode of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described here. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary implementation mode shown in the accompanying drawings are not limitations on the present invention. In the drawings, the same unit / element uses the same reference numeral.

[0039] Unless otherwise specified, the terms (including scientific and technical terms) used here have the ordinary meaning understood by those skilled in the art. In addition, it can be understood that the terms defined in the commonly used dictionary should be understood to have a meaning consistent with the context of their related fields, and should not be understood as idealized or overly formal meanings.

[0040] Embodiment 1:

[0041] This embodiment provides a gas-liquid two-phase flow measurement system based on ultrasonic and radio frequency, which includes a measurement pipe segment 42, a battery 43 and a measurement circuit 44. The measurement pipe segment 42 includes an ultrasonic sensor and a radio frequency antenna. The battery 43 is used to supply power to the measurement circuit 44. The ultrasonic sensor and the radio frequency antenna are electrically connected to the measurement circuit 44. The measurement circuit 44 is used to adjust the voltage of the battery 43 to supply power to the ultrasonic sensor and the radio frequency antenna, and to judge the fluid type according to the output signals of the ultrasonic sensor and / or the radio frequency antenna and calculate the gas flow rate, liquid flow rate and total flow rate.

[0042] Embodiment 2:

[0043] Based on Embodiment 1, this embodiment provides a gas-liquid two-phase flow measurement system based on ultrasonic and radio frequency. The measurement pipe segment 42 includes an ultrasonic sensor, a radio frequency antenna, an inner pipe and an outer protection pipe 3. The outer protection pipe 3 is arranged outside the inner pipe. There are two pairs of ultrasonic sensors and they are arranged crosswise. The two pairs of ultrasonic waves are the first ultrasonic sensor 13 and the second ultrasonic sensor 21, the third ultrasonic sensor 22 and the fourth ultrasonic sensor 27 respectively. Among them, the frequency of the first pair of ultrasonic sensors is suitable for propagation in liquid, and the frequency of the second pair of ultrasonic sensors is suitable for propagation in gas. There are two radio frequency antennas, which are the first radio frequency antenna 6 and the second radio frequency antenna 12 respectively;

[0044] The first radio frequency antenna 6, the second radio frequency antenna 12 and the ultrasonic sensor are successively arranged on the inner pipe along the fluid flow direction. The straight line where the first ultrasonic sensor 13 and the second ultrasonic sensor 21 are located intersects with the axis of the inner pipe, and the included angle with the axis is 35°-55°. The straight line where the third ultrasonic sensor 22 and the fourth ultrasonic sensor 27 are located intersects with the axis of the inner pipe, and the included angle with the axis is 125-145°. The straight line 1 and the straight line 2 intersect with the axis at the same point.

[0045] Principle of the present invention:

[0046] 1) When the liquid is full-flowing in the pipe. That is, there is no gas in the pipe and the liquid is 100%. The response characteristics of each ultrasonic sensor are:

[0047] The first pair of ultrasonic sensors: composed of the first ultrasonic sensor 13 and the second ultrasonic sensor 21, and the installation angle is 35°-55°. The ultrasonic signals with the frequency of this pair of ultrasonic sensors have good propagation characteristics in liquid, and the flow rate of the whole liquid can be measured.

[0048] The second pair of ultrasonic sensors: It consists of the third ultrasonic sensor 22 and the fourth ultrasonic sensor 27, and the installation angle is 125 - 145°. The ultrasonic signals of this pair of ultrasonic sensors with a certain frequency have good propagation characteristics in gas, but are not suitable for measuring liquid flow rate.

[0049] Two RF antennas (the first RF antenna 6 and the second RF antenna 12): When the pipe is full of liquid, since the dielectric constant of the liquid is much larger than that of air, the signal amplitude obtained when any RF antenna emits at one end and receives at the other end is 1.2 - 1.8V, which can be used to confirm that the pipe is full of liquid.

[0050] Therefore, the signal measured by the first pair of ultrasonic sensors is used as the flow measurement result. The principle of measuring the flow rate is as follows: The first ultrasonic sensor 13 and the second ultrasonic sensor 21 alternately emit pulse signals. The time when the first ultrasonic sensor 13 emits and the second ultrasonic sensor 21 receives is

[0051] The time when the second ultrasonic sensor 21 emits and the first ultrasonic sensor 13 receives is

[0052] Then the time difference between the two is

[0053] The flow velocity can be obtained as:

[0054] In the formula, υ is the flow velocity, m / s; c is the propagation velocity of ultrasonic wave in the medium, c = 1480m / s (for water); D is the inner diameter of the pipe, m; α is the angle between the straight line where the first pair of ultrasonic sensors is located and the axis.

[0055] 2) The pipe is full of flowing gas. That is, there is no liquid in the pipe and the gas is 100%. The response characteristics of each ultrasonic sensor are as follows:

[0056] The first pair of ultrasonic sensors: The ultrasonic signals with their corresponding frequencies have good propagation characteristics in liquid, but attenuate very quickly in gas and it is very difficult to detect signals, so they are not suitable for measuring gas flow rate.

[0057] The second pair of ultrasonic sensors: The ultrasonic signals with their corresponding frequencies have good propagation characteristics in gas and are very suitable for measuring gas flow rate.

[0058] Two RF antennas (the first RF antenna 6 and the second RF antenna 12): When the pipe is full of gas, since the dielectric constant of the gas is much smaller than that of the liquid, the signal amplitude obtained when any antenna emits at one end and receives at the other end is 0.3 - 0.6V, which can be used to confirm that the pipe is full of gas. Therefore, the signal measured by the second pair of ultrasonic sensors can be used as the flow measurement result.

[0059] From Calculate the flow velocity, where the angle α is the angle between the line where the second pair of ultrasonic sensors is located and the axis; c is the speed of sound of ultrasonic waves in the gas, which is 340 m / s (for gas).

[0060] 3) The fluid in the pipe is a gas-liquid mixed fluid with full pipe flow. The typical inner diameter of the blowdown pipeline is 62 mm. The flow rate of gas well blowdown is mostly 20,000 - 100,000 cubic meters per day. Its Reynolds number is much greater than 4000, so its flow regime must be turbulent. However, the gas-liquid ratio is unknown. The response characteristics of each ultrasonic sensor are:

[0061] The first pair of ultrasonic sensors: The ultrasonic signal of this frequency has good propagation characteristics in the liquid, but attenuates rapidly in the gas. When the gas ratio is high, it is difficult to detect the signal. Due to the unknown gas holdup, it is difficult to be used for the flow measurement of gas-water mixed liquids.

[0062] The second pair of ultrasonic sensors: Contrary to the first pair of ultrasonic sensors, it cannot be used for the flow measurement of high water cut.

[0063] Two RF antennas: The gas holdup or liquid holdup can be measured simultaneously, and the average value of the two is used as the final gas holdup or liquid holdup. At the same time, since the two antennas are installed at a distance of 1 cm - 8 cm, in the case of turbulent flow with gas, when the liquid passes through the first antenna and the second antenna, the received signals are correlated. The flow rate can be calculated through correlation operations. The specific principle is:

[0064] Let the signal received by the first RF antenna 6 be x(t), and the signal received by the second RF antenna 12 be y(t). Then the correlation function of the two is:

[0065]

[0066] The continuous measurement process is divided into many time periods according to time. T is the length of the time period, unit: s; τ is the time corresponding to the maximum value of Rxy obtained by cross-correlation operation, s; t is time, s. In the formula, it is the integration variable, that is, the independent variable of x(t) and y(t).

[0067] The time corresponding to the maximum value of the correlation function is the time when the liquid passes through the two RF antennas. Since the installation distance of the two RF antennas is known, the flow velocity can be obtained based on time and distance, and then the flow rate can be calculated from the pipe diameter and flow velocity.

[0068] Among them, the received signal of the RF antenna is related to the dielectric constant ε r and conductivity σ of the fluid in the pipe. The phase attenuation coefficient β and amplitude attenuation coefficient γ are respectively:

[0069]

[0070]

[0071] Where, γ is the amplitude attenuation coefficient, Np / m; β is the phase attenuation coefficient, rad / m; μ is the magnetic permeability of the fluid, H / m; ε r is the relative dielectric constant of the fluid; ω is the angular frequency, rad; σ is the conductivity of the fluid, S / m.

[0072] The gas in the gas-liquid mainly refers to natural gas, and the liquid is mainly water. When the gas-liquid ratio is different, because the dielectric constant of the liquid is 80, the relative dielectric constant of the gas is 2, and the correlation is 40 times. Therefore, when the gas-liquid ratio in the pipe is different, the amplitude and phase are also different. The gas-liquid ratio in the pipeline can be detected by the amplitude and phase, and of course it can also be distinguished whether it is all liquid or gas.

[0073] Embodiment 3:

[0074] This embodiment provides a gas-liquid two-phase flow measurement system based on ultrasound and radio frequency, such as Figure 1 In the dotted frame, the gas-liquid two-phase flow measurement system includes a measuring pipe section 42, a battery 43, and a measuring circuit 44. After obtaining the flow rate, the measuring circuit 44 sends a signal to a wireless transmitter 45, and the wireless transmitter 45 sends the flow rate signal to a remote wireless receiver 46 via wireless transmission.

[0075] The fluid inlet is connected to the wellhead of the gas well 47 through a pipeline, and the outlet of the measuring pipe section 42 is connected to the gas-liquid collecting device 48 through a pipeline. The battery 43 is a rechargeable battery 43.

[0076] The rechargeable battery 43, the measuring circuit 44, the wireless transmitter and the remote wireless receiver 46 and other components are outside the measuring pipe section 42, wherein the rechargeable battery 43 supplies power to the measuring circuit 44. The role and function of the measuring circuit 44 are: first, to adjust the voltage of the rechargeable battery 43 to power various ultrasonic sensors and radio frequency antennas in the measuring pipe section 42; second, to provide excitation or transmission signals to various sensors inside the measuring pipe section 42 and receive output signals of ultrasonic sensors; third, to process the output signals of ultrasonic sensors and calculate gas flow, liquid flow and total flow.

[0077] Embodiment 4:

[0078] This embodiment provides a gas-liquid two-phase flow measurement system based on ultrasound and radio frequency, such as Figure 2 As shown, the inner tube includes a right transition tube 8, a radio frequency antenna installation tube 7, an ultrasonic sensor installation body 5 and a left transition tube 4 which are sequentially connected along the fluid direction.

[0079] The right transition pipe 8 is connected to one end of the outer protection pipe 3 through the right connecting pipe 11 and the right plug 9, and the left transition pipe 4 is connected to the other end of the outer protection pipe 3 through the left connecting pipe 1 and the left plug 2.

[0080] In this embodiment, the left connecting pipe 1 is connected to the connecting pipe of the collection device 48 in Figure 1 through a thread 17, and the right connecting pipe 11 of the measuring pipe section 42 is connected to the blowout preventer line in Figure 1 through a thread 17. The other end of the blowout preventer line is connected to the wellhead of the gas well 47. The arrow indicates the flow direction of the fluid in the pipeline.

[0081] Refer to Figure 2 , the left connecting pipe 1 of the measuring pipe section 42 is connected to the left transition pipe 4 through a thread 17 and sealed with a first sealing ring 16. The left connecting pipe 1 is also connected to the left plug 2 through a first weld 14. The outer diameter of the left plug 2 is connected to the outer protection pipe 3 through a fixing screw 15 and sealed with a seventh sealing ring 36.

[0082] Refer to Figure 2 , the right end of the left transition pipe 4 is connected to the ultrasonic sensor mounting body 5 through a thread 17, a second sealing ring 18, and a fourth positioning pin 37. The other end of this mounting body is connected to the RF antenna mounting pipe 7 through a thread 17, a fourth sealing ring 23, and a first positioning pin 2424. The other end of this RF antenna mounting pipe 7 is connected to the right transition pipe 8 through a thread 17, a fifth sealing ring 26, and a second positioning pin 25. The right end of the right transition pipe 8 is connected to the right connecting pipe 11 through a thread 17, a sixth sealing ring 29, and a third positioning pin 30. This right connecting pipe 11 is connected to the right plug 9 through a second weld 33. This right plug 9 is connected to the right end of the outer protection pipe 3 through a pin 31. The cable outlet 32 on this right plug 9 is used to pass multiple wires and is connected to Figure 1 the measuring circuit 44 in

[0083] See Figure 2 , four ultrasonic sensors are installed on the ultrasonic sensor mounting body 5 in the measuring pipe section 42. The installation method of each ultrasonic sensor is the same, and they are all installed on the ultrasonic sensor mounting body 5 through a thread 17 and a sealing ring. Taking the first ultrasonic sensor 13 as an example, the first sensor is installed on the ultrasonic sensor mounting body 5 through a thread 17 and an eighth sealing ring 41. Similarly, the second ultrasonic sensor 21 is installed on the ultrasonic sensor mounting body 5 through a thread 17 and a third sealing ring 20. The installation methods of the third ultrasonic sensor 22 and the fourth ultrasonic sensor 27 are the same as above.

[0084] The first ultrasonic sensor 13 and the second ultrasonic sensor 21 among the four ultrasonic sensors form a pair and are used to measure the flow rate of all the liquid in the pipe. Under the action of the Figure 1 measuring circuit 44 shown, the first ultrasonic sensor 13 emits, and the second ultrasonic sensor 21 receives. Then, the second ultrasonic sensor 21 emits, and the first ultrasonic sensor 13 receives, repeating this process continuously to obtain the time difference and calculate the real-time flow velocity and flow rate.

[0085] Refer to Figure 2 . On the radio frequency antenna mounting pipe 7 in the measuring pipe section 42, there are two radio frequency antennas, namely the first radio frequency antenna 6 and the second radio frequency antenna 12. At each end of each radio frequency antenna, there is a sealing needle, namely the first sealing needle 28, the second sealing needle 34, the third sealing needle 35, and the fourth sealing needle 38. Each sealing needle is provided with a thread 17 and a sealing ring, which are standard off-the-shelf components. Their function is to connect the antenna to the radio frequency antenna mounting body and can also seal.

[0086] Refer to Figure 2 . The first lead-out end 39 and the second lead-out end 40 of the first radio frequency antenna 6 are the transmitting end and the receiving end respectively. The third lead-out end 19 and the fourth lead-out end 10 of the second radio frequency antenna 12 are the transmitting end and the receiving end respectively. They are all led out through a cable from the multi-strand cable outlet 32 and connected to the measuring circuit 44.

[0087] Example 5:

[0088] This example provides a gas-liquid two-phase flow measurement system based on ultrasonic and radio frequency. The first radio frequency antenna 6 and the second radio frequency antenna 12 are both installed perpendicular to the axis, and the distance between the first radio frequency antenna 6 and the second radio frequency antenna 12 is 1 - 8 cm.

[0089] The frequencies of the first ultrasonic sensor 13 and the second ultrasonic sensor 21 are both 500 kHz - 2 MHz, and the frequencies of the third ultrasonic sensor 22 and the fourth ultrasonic sensor 27 are both 20 kHz - 200 kHz.

[0090] Example 6:

[0091] This example provides a gas-liquid two-phase flow measurement method based on ultrasonic and radio frequency. Using the gas-liquid two-phase flow measurement system based on ultrasonic and radio frequency, when the fluid flows through the measuring pipe section 42, the two radio frequency antennas and / or the two pairs of ultrasonic sensors output signals to the measuring circuit 44. The measuring circuit 44 determines the fluid type according to the signals and calculates the gas flow rate, liquid flow rate, and total flow rate.

[0092] Example 7:

[0093] Based on Embodiment 6, this embodiment provides a method for measuring gas-liquid two-phase flow based on ultrasonic and radio frequency, where the fluid types include liquid, gas, and gas-liquid mixture;

[0094] When the signal amplitude obtained by transmitting from one end and receiving at the other end of the first radio frequency antenna 6 or the second radio frequency antenna 12 is 1.2 - 1.8V, the measurement circuit 44 determines that the fluid is liquid. Then, the measurement circuit 44 obtains the flow velocity through the time difference of the signals received by the first pair of ultrasonic sensors from each other, and finally calculates the liquid flow rate;

[0095] When the signal amplitude obtained by transmitting from one end and receiving at the other end of the first radio frequency antenna 6 or the second radio frequency antenna 12 is 0.3 - 0.6V, the measurement circuit 44 determines that the fluid is gas. Then, the measurement circuit 44 obtains the flow velocity through the time difference of the signals received by the second pair of ultrasonic sensors from each other, and finally calculates the gas flow rate;

[0096] When both pairs of ultrasonic sensors have no response when the fluid passes by, the measurement circuit 44 determines that the fluid is gas-liquid mixture. Then, the measurement circuit 44 takes the average value of the gas holdup or liquid holdup measured by the two radio frequency antennas, and then obtains the time taken to pass through the two radio frequency antennas according to the correlation function of the signals received by the two radio frequency antennas. Based on the time and distance, the flow velocity is obtained, and finally the total flow rate, gas flow rate, and liquid flow rate are calculated.

[0097] The time difference of the signals received by the first pair of ultrasonic sensors from each other is Δt;

[0098] Among them, the time when the first ultrasonic sensor 13 transmits and the second ultrasonic sensor 21 receives is The time when the second ultrasonic sensor 21 transmits and the first ultrasonic sensor 13 receives is Then the time difference

[0099] In the formula, υ is the flow velocity, m / s; c is the propagation speed of ultrasonic waves in the medium. For gas, c is 340m / s, and for water, c is 1480m / s; D is the inner diameter of the pipeline, m; α is the angle between the straight line where the two pairs of ultrasonic sensors are located and the axis.

[0100] The correlation function of the signals received by the two radio frequency antennas is:

[0101]

[0102] In the formula, x(t) is the signal received by the first radio frequency antenna 6; y(t) is the signal received by the second radio frequency antenna 12; T is the length of the time period, s; τ is the time corresponding to the maximum value of Rxy obtained by the cross-correlation operation, s; t is the integration variable, s.

[0103] Embodiment 8:

[0104] Based on Example 7, this example provides a method for measuring gas-liquid two-phase flow based on ultrasonic and radio frequency. The measurement of flow rate is divided into the following three cases:

[0105] Case 1: The pipe is full of flowing liquid. That is, there is no gas in the pipe and the liquid is 100%. The response characteristics of each sensor are as follows:

[0106] The first pair of ultrasonic sensors: It consists of the first ultrasonic sensor 13 and the second ultrasonic sensor 21, with an installation angle of 40° (that is, the first straight line rotates counterclockwise by 40° to coincide with the axis). Its frequency is 1 MHz. The ultrasonic signal of this frequency has good propagation characteristics in the liquid and can measure the flow rate of the whole liquid.

[0107] The second pair of ultrasonic sensors: It consists of the third ultrasonic sensor 22 and the fourth ultrasonic sensor 27, with an installation angle of 140° (that is, the second straight line rotates counterclockwise by 140° to coincide with the axis). Its frequency is 40 kHz. The ultrasonic signal of this frequency has good propagation characteristics in the gas but is not suitable for measuring the liquid flow rate.

[0108] Two RF antennas: When the pipe is full of liquid, since the dielectric constant of the liquid is much larger than that of air, the signal amplitude obtained when the first RF antenna 6 or the second RF antenna 12 transmits at one end and receives at the other end is 1 V, which can be used to confirm that the pipe is full of liquid.

[0109] Therefore, the flow velocity is calculated through the obtained time difference Δt, and then the liquid flow rate is calculated.

[0110] Case 2: The pipe is full of flowing gas. That is, there is no liquid in the pipe and the gas is 100%. The response characteristics of each sensor are as follows:

[0111] The first pair of ultrasonic sensors: Its frequency is 1 MHz. The ultrasonic signal of this frequency has good propagation characteristics in the liquid but attenuates quickly in the gas, and it is difficult to detect the signal, so it is not suitable for measuring the gas flow rate.

[0112] The second pair of ultrasonic sensors: Its frequency is 40 kHz. The ultrasonic signal of this frequency has good propagation characteristics in the gas and is very suitable for measuring the gas flow rate.

[0113] Two RF antennas: When the pipe is full of gas, since the dielectric constant of the gas is much smaller than that of the liquid, the signal amplitude obtained when the first RF antenna 6 or the second RF antenna 12 transmits at one end and receives at the other end is 0.4 V, which can be used to confirm that the pipe is full of gas. Therefore, the signal measured by the second pair of ultrasonic sensors can be used as the flow measurement result.

[0114] Similarly, the flow velocity is calculated based on the obtained time difference Δt, and then the gas flow rate is calculated.

[0115] Case 3: The fluid in the pipe is a gas-liquid mixed fluid with full pipe flow, and the flow regime is turbulent, but the gas-liquid ratio is unknown. The response characteristics of each sensor are as follows:

[0116] The first pair of ultrasonic sensors: Its frequency is 1 MHz. The ultrasonic signal of this frequency has good propagation characteristics in liquids, but attenuates rapidly in gases. When the gas ratio is high, it is difficult to detect the signal. Since the gas holdup is unknown, it is difficult to be used for the flow measurement of gas-water mixed liquids.

[0117] The second pair of ultrasonic sensors: Its frequency is 40 kHz. Contrary to the first pair of ultrasonic sensors, it cannot be used for the flow measurement with a high water content.

[0118] Two RF antennas: They can measure the gas holdup or liquid holdup simultaneously, and the average value of the two is used as the final gas holdup or liquid holdup. At the same time, since the two RF antennas are installed at a certain distance, in the case of turbulent flow and the presence of gas, when the liquid passes through the first RF antenna and the second RF antenna, the received signals are correlated, and the flow rate can be calculated through relevant operations.

[0119] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. An ultrasonic and radio frequency-based gas-liquid two-phase flow measurement system, characterized in that: It includes a measuring pipe section (42), a battery (43) and a measuring circuit (44). The measuring pipe section (42) includes ultrasonic sensors and RF antennas. The battery (43) is used to supply power to the measuring circuit (44). The ultrasonic sensors and RF antennas are electrically connected to the measuring circuit (44). The measuring circuit (44) is used to adjust the voltage of the battery (43) to supply power to the ultrasonic sensors and RF antennas, and to judge the fluid type according to the output signals of the ultrasonic sensors and / or RF antennas and calculate the gas flow rate, liquid flow rate and total flow rate. There are two pairs of ultrasonic sensors which are arranged crosswise. The two pairs of ultrasonic sensors are the first ultrasonic sensor (13) and the second ultrasonic sensor (21), the third ultrasonic sensor (22) and the fourth ultrasonic sensor (27) respectively. There are two RF antennas, which are the first RF antenna (6) and the second RF antenna (12) respectively. When the signal amplitude obtained when one end of the first RF antenna (6) or the second RF antenna (12) transmits and the other end receives is 1.2 - 1.8V, the measuring circuit (44) judges that the fluid is a liquid. When the signal amplitude obtained when one end of the first RF antenna (6) or the second RF antenna (12) transmits and the other end receives is 0.3 - 0.6V, the measuring circuit (44) judges that the fluid is a gas.

2. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement system according to claim 1, characterized in that: The measuring pipe section (42) includes ultrasonic sensors, RF antennas, an inner pipe and an outer protection pipe (3). The outer protection pipe (3) is arranged outside the inner pipe. There are two pairs of ultrasonic sensors which are arranged crosswise. The two pairs of ultrasonic sensors are the first ultrasonic sensor (13) and the second ultrasonic sensor (21), the third ultrasonic sensor (22) and the fourth ultrasonic sensor (27) respectively. Among them, the frequency of the first pair of ultrasonic sensors is suitable for propagation in liquids, and the frequency of the second pair of ultrasonic sensors is suitable for propagation in gases. The first RF antenna (6), the second RF antenna (12) and ultrasonic sensors are successively arranged on the inner pipe along the fluid flow direction.

3. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement system according to claim 2, characterized in that: The inner pipe includes a right transition pipe (8), an RF antenna installation pipe (7), an ultrasonic sensor installation body (5) and a left transition pipe (4) which are successively connected along the fluid direction.

4. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement system according to claim 2, characterized in that: The first RF antenna (6) and the second RF antenna (12) are both installed perpendicular to the axis, and the distance between the first RF antenna (6) and the second RF antenna (12) is 1 - 8 cm.

5. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement system according to claim 2, characterized in that: The frequencies of the first ultrasonic sensor (13) and the second ultrasonic sensor (21) are both 500 kHz - 2 MHz, and the frequencies of the third ultrasonic sensor (22) and the fourth ultrasonic sensor (27) are both 20 kHz - 200 kHz.

6. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement system according to claim 3, characterized in that: The right transition pipe (8) is connected to one end of the outer protection pipe (3) through a right connecting pipe (11) and a right plug (9), and the left transition pipe (4) is connected to the other end of the outer protection pipe (3) through a left connecting pipe (1) and a left plug (2).

7. An ultrasonic and radio frequency-based gas-liquid two-phase flow measurement method, using the ultrasonic and radio frequency-based gas-liquid two-phase flow measurement system according to claim 2, characterized in that: When fluid flows through the measuring pipe section (42), two RF antennas and / or two pairs of ultrasonic sensors output signals to the measuring circuit (44). The measuring circuit (44) determines the fluid type based on the signals and calculates the gas flow rate, liquid flow rate, and total flow rate.

8. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement method according to claim 7, characterized in that: The fluid types include liquid, gas, and gas-liquid mixture. When the signal amplitude obtained by transmitting from one end and receiving at the other end of the first RF antenna (6) or the second RF antenna (12) is 1.2 - 1.8 V, the measuring circuit (44) determines that the fluid is liquid. Then, the measuring circuit (44) obtains the flow velocity through the time difference of the signals received by the first pair of ultrasonic sensors from each other, and finally calculates the liquid flow rate. When the signal amplitude obtained by transmitting from one end and receiving at the other end of the first RF antenna (6) or the second RF antenna (12) is 0.3 - 0.6 V, the measuring circuit (44) determines that the fluid is gas. Then, the measuring circuit (44) obtains the flow velocity through the time difference of the signals received by the second pair of ultrasonic sensors from each other, and finally calculates the gas flow rate. When both pairs of ultrasonic sensors have no response when the fluid passes by, the measuring circuit (44) determines that the fluid is gas-liquid mixture. Then, the measuring circuit (44) takes the average value of the gas content rate or liquid content rate measured by the two RF antennas, and then obtains the time taken to pass through the two RF antennas according to the correlation function of the signals received by the two RF antennas. The flow velocity is obtained based on the time and distance, and finally the total flow rate, gas flow rate, and liquid flow rate are calculated.

9. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement method according to claim 8, characterized in that: The time difference of the signals received by the first pair of ultrasonic sensors from each other is Δt. wherein, the time when the first ultrasonic sensor (13) emits and the second ultrasonic sensor (21) receives is , the time when the second ultrasonic sensor (21) emits and the first ultrasonic sensor (13) receives is , then the time ; In the formula, υ is the flow velocity, m / s; c is the propagation speed of ultrasonic waves in the medium. For gas, c is 340 m / s, and for water, c is 1480 m / s; D is the inner diameter of the pipe, m; α is the angle between the straight line where the two pairs of ultrasonic sensors are located and the axis.

10. The ultrasonic and radio frequency-based gas-liquid two-phase flow measurement method according to claim 8, characterized in that: The correlation function of the signals received by the two RF antennas is: In the formula, x(t) is the signal received by the first RF antenna (6); y(t) is the signal received by the second RF antenna (12); T is the length of the time period, s; τ is the time corresponding to the maximum value of Rxy obtained by cross-correlation operation, s; t is the integration variable, s.

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