Steam mass flow measuring device and method based on fiber optic interference principle

Abstract

The application provides a steam mass flow measuring device and method based on the optical fiber interference principle, wherein a high-pressure cavity sensing optical fiber and a low-pressure cavity sensing optical fiber are arranged in the flow resistance body, a light source and a beam splitter for splitting the coherent light of the same frequency emitted by the light source into two beams are arranged below the outside of the pipeline, an optical detector connected with a processor is arranged above the outside of the pipeline, and the input ends of the optical detector are connected with the high-pressure cavity sensing optical fiber and the low-pressure cavity sensing optical fiber at equal distances. The application is safe and reliable, can realize real-time continuous distributed remote measurement, has higher sensitivity and cost performance than other optical fiber flow meters and differential pressure flow meters, is not affected by factors such as light source fluctuation and temperature change because phase signals are detected, is suitable for pipeline steam flow testing in high-temperature environments, can reduce the manufacturing cost of the measuring device, optimizes the structure of the measuring device, and provides a new method for steam flow mass measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of two-phase flow detection, in particular to a steam mass flow measurement device and method based on the principle of optical fiber interference. BACKGROUND

[0002] Differential pressure measurement method is often used for pressure detection in industrial production and actual life, especially in the field of gas-liquid two-phase flow detection.

[0003] At present, the traditional differential pressure measurement method is to use a pressure lead pipe to introduce high and low pressures into a transmitter. A differential pressure sensor adopts an integrated structure of high and low pressure cavities, and a measurement diaphragm is placed in the middle of the high and low pressures. When the pressures generated by the two pressure cavities are different, the pressure diaphragm will deform, converting into an electrical signal for output, thereby indirectly obtaining the differential pressure value. In order to change the pressure value in the pressure cavity, a pressure lead pipe is needed to lead the pressure on the measurement pipe, and two different pressure values are introduced into the pressure cavity.

[0004] The sensors used in the prior art to detect differential pressure include resistance strain type, diffused silicon pressure resistance type, capacitance type, inductance type, and piezoelectric type. The principle used is to measure the differential pressure value according to the change of the pressure value, thereby causing the change of the voltage value.

[0005] The traditional differential pressure measurement needs to introduce high and low pressures into a sensor unit. Due to the resistance effect and piezoelectric effect, which are relatively mature, and the influence of the two differential pressures, this can make the measurement accuracy higher and have higher sensitivity in the measurement process. However, the disadvantage is also obvious, that is, the pressure in the pressure lead pipe is greatly affected by the medium in the pipe, especially when the fluid is full of multiphase flow. This is more obvious in vertical pipe measurement. Moreover, the parameters of the installed pressure cavities are relatively complex, and it is impossible to ensure that the parameters of the two pressure cavities are completely consistent, which will cause errors in the measurement process.

[0006] The measurement methods of steam mass flow can be roughly summarized into three types, namely, throttling flowmeter, non-throttling flowmeter, and indirect measurement method. The throttling flowmeter has high measurement accuracy, but causes pressure loss to steam. The non-throttling flowmeter uses additional devices such as float and impeller to measure the steam flow, and almost does not cause pressure loss, but the measurement accuracy needs to be improved. The indirect measurement method is a mathematical modeling method for obtaining steam flow measurement according to the flow law of steam. It has been widely concerned by industry personnel due to its low cost and wide application range, and has been widely valued by the academic circle.

[0007] Throttling flowmeter refers to setting orifice plate, elbow and other throttling devices on steam flow path, so that steam flow state changes when flowing through throttling devices, and then flow of steam is calculated by detecting parameters such as pressure difference and vortex frequency. At present, commonly used throttling flowmeters include differential pressure flowmeter and vortex flowmeter. Indirect measurement method is a modeling method for depicting flow variation characteristics according to fluid motion variation and fluid mechanics law. It establishes fluid motion model according to physical law followed by fluid flow, and then obtains flow of fluid to be measured by means of known, easily measured parameters and related boundary conditions. At present, indirect measurement method mainly researches flow measurement of single-phase flow and two-phase flow, but research work is extremely rare.

[0008] Chen Zhihang once used combination of oval gear flowmeter and orifice flowmeter to measure gas flow and liquid flow of gas-liquid two-phase flow. Li Haiqing once carried out combination measurement test by using air and water medium and double orifice plate cascade. Du Yipeng et al. use double vortex joint method to measure two-phase flow or multi-phase flow during flow process, use two vortex sensors to measure average flow velocity and vortex lift of fluid respectively, realize measurement of flow, density and dryness of wet saturated steam. Pu Cheng et al. use frequency signal generated by vortex flowmeter, V-cone flowmeter, differential pressure transmitter and temperature sensor and differential pressure signal generated by conical flowmeter to obtain actual density of wet steam, then substitute into flow formula of vortex or V-cone to obtain actual mass flow, measure temperature and pressure of pipeline to obtain dry density of saturated wet steam, and then obtain dryness of saturated wet steam. Disadvantage of the combined measurement device is that the device is relatively complex, and multi-point measurement will cause large measurement error. SUMMARY

[0009] One of the purposes of the present application is to provide a steam mass flow measurement device based on optical fiber interference principle to solve the problem of large measurement error caused by complex existing series combination method steam measurement device.

[0010] One of the purposes of the present application is achieved as follows: a steam mass flow measurement device based on optical fiber interference principle, a flow resistance body is arranged on the central axis in the pipeline, the flow resistance body is a hollow columnar body with a cross section in the shape of an isosceles trapezoid; the upper and lower ends of the flow resistance body are connected with the inner wall of the pipeline and form an integral structure with the pipeline; the front side of the flow resistance body is a flow face, and the back side of the flow resistance body is a back flow face; a partition plate parallel to the flow face and the back flow face is arranged at the central position in the flow resistance body, the partition plate divides the inner cavity of the flow resistance body into a high-pressure cavity in front and a low-pressure cavity behind; four high-pressure holes in communication with the high-pressure cavity are sequentially opened from top to bottom on the central axis of the flow face of the flow resistance body, and three low-pressure holes in communication with the low-pressure cavity are sequentially opened from top to bottom on the central axis of the back flow face of the flow resistance body.

[0011] The high-pressure cavity sensing optical fiber is parallel to the blocking fluid, and the low-pressure cavity sensing optical fiber is parallel to the blocking fluid; the upper end of the high-pressure cavity sensing optical fiber is connected with the coupler of the penetrating pipeline, and the lower end is connected with the lower transparent glass of the penetrating pipeline; the upper end of the low-pressure cavity sensing optical fiber is connected with the upper transparent glass of the penetrating pipeline, and the lower end is connected with the collimating lens of the penetrating pipeline;

[0012] The light source and the light splitter are arranged below the outside of the pipeline, and the light splitter divides the coherent light of the same frequency emitted by the light source into two beams; the output ends of the light splitter are connected with the high-pressure cavity sensing optical fiber and the low-pressure cavity sensing optical fiber at equal distances, respectively;

[0013] The photodetector connected with the processor is arranged above the outside of the pipeline; the input ends of the photodetector are connected with the high-pressure cavity sensing optical fiber and the low-pressure cavity sensing optical fiber at equal distances, respectively.

[0014] Further, the present application can be realized according to the following technical scheme:

[0015] The output ends of the light splitter are connected to the lower transparent glass and the collimating lens through two input optical fibers with the same length, respectively; and the input ends of the photodetector are connected to the coupler and the upper transparent glass through two output optical fibers with the same length, respectively.

[0016] The trapezoid-like shape includes an upper base, a lower base, two legs and two straight sides; the two ends of the lower base are connected with the corresponding two legs through the two straight sides, respectively; the lower base corresponds to the width of the flow face of the blocking fluid, and the upper base corresponds to the width of the back flow face of the blocking fluid.

[0017] The four high-pressure holes are sequentially arranged from top to bottom as a first high-pressure hole, a second high-pressure hole, a third high-pressure hole and a fourth high-pressure hole; the first high-pressure hole and the second high-pressure hole are located at 0.866R and 0.5R of the radius direction of the pipeline cross section, respectively, R being the radius of the pipeline; the third high-pressure hole and the second high-pressure hole are in a center symmetric structure with respect to the flow face, and the fourth high-pressure hole and the first high-pressure hole are in a center symmetric structure with respect to the flow face.

[0018] The three low-pressure holes are sequentially arranged from top to bottom as a first low-pressure hole, a fluctuation low-pressure hole and a second low-pressure hole; the first low-pressure hole is located at 0.866R of the radius direction of the pipeline cross section, R being the radius of the pipeline; the second low-pressure hole and the first low-pressure hole are in a center symmetric structure with respect to the back flow face, and the fluctuation low-pressure hole is located at a midpoint position.

[0019] The ratio of the width of the flow face of the blocking fluid to the inner diameter of the pipeline is 0.28.

[0020] The display module connected with the processor is further arranged for displaying the result calculated by the processor.

[0021] The second object of the present application is to provide a steam mass flow measurement method based on the principle of optical fiber interference to solve the problem that the existing technology cannot measure the pipeline steam flow in a high temperature environment.

[0022] The second object of the present application is achieved by a steam mass flow measurement method based on the principle of optical fiber interference, which uses the measurement device of claim 1, and the specific steps are as follows:

[0023] a. When the fluid in the pipeline flows through the flow resistance, two rows of regular staggered vortices are alternately separated and released on both sides behind the flow resistance;

[0024] b. The light waves emitted by the light source are divided into two light wave signals with the same frequency via a beam splitter, and the two light wave signals pass through the input optical fiber with the same distance, respectively, and are transmitted into the low pressure cavity and the high pressure cavity via the collimating lens and the lower transparent glass;

[0025] c. When the steam flows through the pipeline and enters the high pressure cavity and the low pressure cavity, the high pressure cavity sensing optical fiber and the low pressure sensing optical fiber are forced to vibrate under different pressures, and the light wave signals are modulated in phase by the vibration, and after passing through the coupler and the upper transparent glass, the light wave signals are transmitted to the optical fiber interference module via the output optical fiber with the same distance;

[0026] d. The two light wave signals form obvious interference fringes at the optical fiber interference module, and after being detected by the photodetector, the moving and changing frequency signal information of the detected interference fringes is transmitted to the processor;

[0027] e. After the processor distinguishes the direction and calculates, the optical fiber interference vibration frequency and the optical fiber interference differential pressure value are obtained, the optical fiber interference vibration frequency is consistent with the vortex shedding frequency f, and the average differential pressure is calculated according to formula 4 The mass flow Q of the steam fluid is calculated according to formula 8 m ;

[0028]

[0029]

[0030] In the formula:

[0031] Q m —The mass flow of steam fluid in the pipeline, kg / s;

[0032] ρ m —The average density of wet steam in the pipeline, kg / m 3 ;

[0033] f—The vortex frequency in the pipeline, Hz;

[0034] ε - the expansion coefficient of the measured medium in the pipeline, for compressible fluids such as gas, steam, etc., ε < 1; ε can be obtained from a table;

[0035] - the average differential pressure of the high-pressure chamber and the low-pressure chamber in the choke body, Pa;

[0036] K1 - the compensated and corrected flowmeter instrument coefficient;

[0037] K2 - the corrected flow coefficient;

[0038] The values of K1 and K2 are calibrated during the experiment;

[0039] wet steam mass flow q m The calculation formula of f and q is as follows:

[0040]

[0041]

[0042] The average density of the wet steam is obtained from formula 3:

[0043]

[0044] The wet steam mass flow is obtained from formula 4 and formula 5:

[0045]

[0046] K m = K1K2 2 ε 2 (7)

[0047] The wet steam mass flow is obtained from formula 6 and formula 7:

[0048]

[0049] In the formula, A is the cross-sectional area of the pipeline, K m is the mass flow instrument coefficient, which is a physical quantity related to the shape and size of the vortex generator, etc., and the value of K m can be calibrated by experimental measurement.

[0050] The present application utilizes the principle of vortex shedding frequency generated by fluid oscillation through the blocking fluid and the principle of optical fiber interference to modulate the light transmitted in the optical fiber, so that the intensity, phase, frequency or polarization state of the transmitted light changes, and then the modulated light signal is detected. The optical fiber interference vibration frequency and the optical fiber interference differential pressure value are measured without affecting the frequency signal generated by the vortex blocking fluid, and then the vortex shedding frequency and the differential pressure average value are obtained. The differential pressure and frequency signals can be extracted and processed simultaneously from one signal, and the mass flow can be calculated through the processor, which solves the problem of large measurement error caused by the complexity of the existing series combination steam measurement device.

[0051] The present application is safe and reliable, can realize real-time continuous distributed telemetry, has higher sensitivity and cost performance than other optical fiber flow meters and differential pressure flow meters, and because the detected signal is a phase signal, it is not affected by factors such as light source fluctuation and temperature change, and is suitable for pipeline steam flow testing in high temperature environment. In this way, the steam mass flow can be accurately calculated, the manufacturing cost of the measurement device can be reduced, the structure of the measurement device can be optimized, and a new method for measuring steam flow mass is provided. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 is a structural schematic diagram of the present application.

[0053] Figure 2 is Figure 1 A-A sectional view of the blocking fluid in

[0054] Figure 3 is a processing block diagram of the present application.

[0055] Figure 4 is a flow chart of the present application.

[0056] In the figure: 1, pipeline, 2, flow face, 3, back flow face, 4, partition, 5, first high pressure hole, 6, second high pressure hole, 7, third high pressure hole, 8, fourth high pressure hole, 9, first low pressure hole, 10, second low pressure hole, 11, high pressure cavity sensing optical fiber, 12, low pressure cavity sensing optical fiber, 13, fluctuating low pressure hole, 14, coupler, 15, upper transparent glass, 16, output optical fiber, 17, lower transparent glass, 18, collimating lens, 19, beam splitter, 20, light source, 21, photodetector, 22, straight edge, 23 input optical fiber. DETAILED DESCRIPTION

[0057] As Figure 1 and Figure 2As shown, the steam mass flow measuring device based on the fiber optic interference principle of the present application is provided with a flow resistance body on the central axis in the pipeline 1, the flow resistance body is a hollow columnar body with a cross section in the shape of an isosceles trapezoid, the isosceles trapezoid includes an upper base, a lower base, two waists and two straight edges 22; the two ends of the lower base are connected to the corresponding two waists through the two straight edges 22 respectively, the width of the lower base corresponds to the width of the flow face 2 of the flow resistance body, and the width of the upper base corresponds to the width of the back flow face 3 of the flow resistance body. Specifically, the flow resistance body in the vortex flowmeter can be used as the uniform velocity tube body.

[0058] The upper and lower ends of the flow resistance body are connected to the inner wall of the pipeline 1 and form an integral structure with the pipeline 1, the front side of the flow resistance body is the flow face 2, and the back side of the flow resistance body is the back flow face 3, so that the ratio of the width of the flow face 2 of the flow resistance body to the inner diameter of the pipeline 1 is 0.28, thereby avoiding that the width of the flow face 2 of the flow resistance body is too large to affect the flow area or too small to affect the vortex generation. A partition plate 4 parallel to the flow face 2 and the back flow face 3 is arranged at the central position in the flow resistance body, and the partition plate 4 divides the inner cavity of the flow resistance body into a front high-pressure cavity and a rear low-pressure cavity. In order to ensure the accuracy of measurement, the geometric size and material of the high-pressure cavity and the low-pressure cavity are kept consistent, the laser length measuring instrument is used to measure the geometric size of the pressure cavity to ensure that the geometric sizes of the two pressure cavities are consistent, and the error of pressure measurement is reduced.

[0059] In order to measure the fiber optic interference vibration frequency and the fiber optic interference differential pressure value, four high-pressure holes in communication with the high-pressure cavity are sequentially opened from top to bottom on the central axis of the flow face 2 of the flow resistance body according to the equal ring area method, the pipeline 1 cross section is divided into four parts with equal area by using the inner circle outer ring method, and the hole opening position is determined at the area equal division position. The four high-pressure holes are a first high-pressure hole 5, a second high-pressure hole 6, a third high-pressure hole 7 and a fourth high-pressure hole 8 from top to bottom; the first high-pressure hole 5 and the second high-pressure hole 6 are located at 0.866R and 0.5R of the pipeline 1 cross section radius direction respectively, R is the radius of the pipeline 1; and the third high-pressure hole 7 and the second high-pressure hole 6 are in a central symmetric structure with respect to the flow face 2, and the fourth high-pressure hole 8 and the first high-pressure hole 5 are in a central symmetric structure with respect to the flow face 2.

[0060] Three low-pressure holes in communication with the low-pressure cavity are sequentially opened from top to bottom on the central axis of the back flow face 3 of the flow resistance body; the three low-pressure holes are a first low-pressure hole 9, a fluctuation low-pressure hole 13 and a second low-pressure hole 10 from top to bottom, the first low-pressure hole 9 is located at 0.866R of the pipeline 1 cross section radius direction, R is the radius of the pipeline 1; the second low-pressure hole 10 and the first low-pressure hole 9 are in a central symmetric structure with respect to the back flow face 3. The fluctuation low-pressure hole 13 is located at the midpoint position. The hole diameter of the fluctuation low-pressure hole 13 is larger than those of the remaining high-pressure holes and low-pressure holes.

[0061] The high-pressure cavity sensing optical fiber 11 parallel to the blocking fluid is arranged on the side of the incident surface 2 of the blocking fluid, and the low-pressure cavity sensing optical fiber 12 parallel to the blocking fluid is arranged on the side of the backflow surface 3 of the blocking fluid; the upper end of the high-pressure cavity sensing optical fiber 11 is connected with the coupler 14 penetrating the pipeline 1, and the lower end is connected with the lower transparent glass 17 penetrating the pipeline 1; the upper end of the low-pressure cavity sensing optical fiber 12 is connected with the upper transparent glass 15 penetrating the pipeline 1, and the lower end is connected with the collimating lens 18 penetrating the pipeline 1. The side of the collimating lens 18 and the coupler 14 connected with the blocking fluid is made of transparent glass, so that the coherent light can be smoothly injected into or out of the blocking fluid, and the high-pressure cavity and the low-pressure cavity are connected with the output optical fiber 16 through the coupler 14.

[0062] The light source 20 and the beam splitter 19 for splitting the coherent light of the same frequency emitted by the light source 20 into two beams are arranged below the outside of the pipeline 1, and the output ends of the beam splitter 19 are connected with the high-pressure cavity sensing optical fiber 11 and the low-pressure cavity sensing optical fiber 12 at equal distances, respectively. The output ends of the beam splitter 19 are connected to the lower transparent glass 17 and the collimating lens 18 through two input optical fibers of the same length, respectively, so as to reduce the influence of the optical path difference and ensure that the transmission distances of the light are equal.

[0063] The photodetector 21 connected with the processor is arranged above the outside of the pipeline 1, and the input ends of the photodetector 21 are connected with the high-pressure cavity sensing optical fiber 11 and the low-pressure cavity sensing optical fiber 12 at equal distances, respectively. The input ends of the photodetector 21 are connected to the coupler 14 and the upper transparent glass 15 through two output optical fibers 16 of the same length, respectively, so as to reduce the influence of the optical path difference and ensure that the transmission distances of the light are equal.

[0064] The processing block diagram is as shown in Figure 3 The flow chart is as shown in Figure 4

[0065] The photodetector 21 is connected with the processor, used for detecting the movement and change information of the interference fringes and transmitting the results to the processor; the display module is connected with the processor, used for displaying the mass flow of the fluid; and the processor is connected with the photodetector 21, used for processing the information of the fringes.

[0066] When the measuring device in the application is used for measurement, the specific measurement method is as follows,

[0067] a. When the fluid of the pipeline 1 flows through the blocking fluid, two rows of regular staggered vortices are alternately separated and released on both sides of the blocking fluid, which is called the Karman vortex street, and the frequency of the vortex is proportional to the flow rate.

[0068] ​b. The light wave emitted by the light source 20 is split into two light wave signals with the same frequency by the beam splitter 19. These two light wave signals are transmitted into the low-pressure cavity and the high-pressure cavity respectively through the collimating lens 18 and the lower transparent glass 17 via the input optical fiber of the same distance.

[0069] c. When fluid flows through pipe 1 and enters the high-pressure chamber and low-pressure chamber, the high-pressure sensing fiber 11 and the low-pressure sensing fiber are subjected to different pressures and undergo forced vibration. The optical wave signal is modulated by this vibration and the phase changes. After passing through coupler 14 and upper transparent glass 15 respectively, the optical wave signal is transmitted to photodetector 21 for detection via output optical fiber 16 of the same distance.

[0070] The continuous light emitted from light source 20 is modulated into a series of periodic pulse sequences and injected into photodetector 21. According to the interference mechanism of light, during the duration of the pulse sequence, the photodetector 21 can detect the interference light signal, while the detected light intensity is zero at other times. When there is no external vibration signal, the amplitude of the interference pulse sequence remains essentially constant. When an external vibration signal acts on a certain point in the sensing fiber, the phase of the light transmitted within the fiber at that corresponding location changes, thus causing a change in the amplitude of the interference pulse sequence.

[0071] d. The two light wave signals will form obvious interference fringes, which are detected by photodetector 21. The frequency signal information of the movement and change of the detected interference fringes is then transmitted to the processor.

[0072] e. After direction identification and calculation, the processor obtains the fiber interference vibration frequency and fiber interference differential pressure value. The output light power transmitted through the fiber changes periodically. The fiber interference vibration frequency is consistent with the vortex shedding frequency f. By analyzing and processing the coherent optical signal, the fiber interference vibration frequency and fiber interference differential pressure value can be obtained, and then the vortex shedding frequency f and the average differential pressure value can be calculated. Calculate the mass flow rate Q of the steam fluid according to formula 8. m The processor sends the results to the display module for display.

[0073]

[0074]

[0075] In the formula:

[0076] Q m —Mass flow rate of steam in pipe 1, kg / s;

[0077] ρ m —Average density of wet steam in pipe 1, kg / m³ 3 ;

[0078] f - vortex shedding frequency in pipe 1, Hz;

[0079] ε - expansion coefficient of the medium in pipe 1, ε < 1 for compressible fluids such as gases, vapors, etc., ε can be found in tables;

[0080] - average differential pressure of the high and low pressure chambers in the choke, Pa;

[0081] K1 - the meter coefficient of the vortex flowmeter after compensation and correction;

[0082] K2 - the corrected flow coefficient;

[0083] where the values of K1 and K2 are calibrated during the experiment;

[0084] wet steam mass flow q m and the frequency f are calculated as follows:

[0085]

[0086]

[0087] The average density of the wet steam is obtained from equation 3:

[0088]

[0089] The wet steam mass flow is obtained from equations 4 and 5:

[0090]

[0091] K m = K1K2 2 ε 2 (7)

[0092] The wet steam mass flow is obtained from equations 6 and 7:

[0093]

[0094] where A is the cross-sectional area of pipe 1, K m is the mass flow meter coefficient, which is a physical quantity related to the shape and size of the vortex generator, etc., and the value of K m can be calibrated by experimental measurement. Therefore, the analysis and processing of the coherent light signal gives the fiber interference vibration frequency and the fiber interference differential pressure value, and then the vortex shedding frequency f and the average differential pressure are obtained. According to equation 8, the mass flow Q m of the fluid is calculated.

Claims

1. A steam mass flow measurement device based on the principle of fiber optic interferometry, comprising a flow-blocking fluid arranged on the central axis of a pipe, the flow-blocking fluid being a hollow column with a cross-section resembling an isosceles trapezoid; the upper and lower ends of the flow-blocking fluid being connected to the inner wall of the pipe and forming an integral structure with the pipe; the front side of the flow-blocking fluid being the flow-facing side, and the rear side of the flow-blocking fluid being the flow-reverse side; a baffle plate parallel to both the flow-facing and flow-reverse sides being provided at the center of the flow-blocking fluid, the baffle plate dividing the inner cavity of the flow-blocking fluid into a high-pressure chamber at the front and a low-pressure chamber at the rear; four high-pressure holes communicating with the high-pressure chamber being opened sequentially from top to bottom on the central axis of the flow-facing side of the flow-blocking fluid, and three low-pressure holes communicating with the low-pressure chamber being opened sequentially from top to bottom on the central axis of the flow-reverse side of the flow-blocking fluid; Its characteristic is that, A high-pressure cavity sensing fiber parallel to the obstructing fluid is disposed on the flow-facing side of the obstructing fluid, and a low-pressure cavity sensing fiber parallel to the obstructing fluid is disposed on the flow-reverse side of the obstructing fluid. The upper end of the high-pressure cavity sensing fiber is connected to the coupler of the exit pipe and the lower end is connected to the lower transparent glass of the exit pipe. The upper end of the low-pressure cavity sensing fiber is connected to the upper transparent glass of the exit pipe and the lower end is connected to the collimating lens of the exit pipe. A light source and a beam splitter that splits coherent light of the same frequency emitted by the light source into two beams are arranged below the outside of the pipe. The output end of the beam splitter is connected to the high-pressure cavity sensing fiber and the low-pressure cavity sensing fiber at equal distances. A photodetector connected to the processor is installed above the outer side of the pipe. The input end of the photodetector is connected at equal distances to the high-pressure cavity sensing fiber and the low-pressure cavity sensing fiber, respectively.

2. The steam mass flow measurement device based on the fiber optic interferometry principle according to claim 1, characterized in that, The output end of the beam splitter is connected to the lower transparent glass and the collimating lens respectively through two input optical fibers of the same length; the input end of the photodetector is connected to the coupler and the upper transparent glass respectively through two output optical fibers of the same length.

3. The steam mass flow measurement device based on the fiber optic interferometry principle according to claim 1, characterized in that, The isosceles trapezoid includes an upper base, a lower base, two sides, and two straight edges; the two ends of the lower base are respectively connected to the corresponding two sides through the two straight edges; the lower base corresponds to the width of the flow-blocking front surface, and the upper base corresponds to the width of the flow-blocking back surface.

4. The steam mass flow measurement device based on the fiber optic interferometry principle according to claim 1, characterized in that, The four high-pressure holes are arranged from top to bottom as the first high-pressure hole, the second high-pressure hole, the third high-pressure hole, and the fourth high-pressure hole. The first and second high-pressure holes are located at 0.866R and 0.5R respectively in the direction of the pipe cross-section radius, where R is the pipe radius. The third high-pressure hole and the second high-pressure hole are centrally symmetrical about the flow-facing surface, and the fourth high-pressure hole and the first high-pressure hole are centrally symmetrical about the flow-facing surface.

5. The steam mass flow measurement device based on the fiber optic interferometry principle according to claim 1, characterized in that, The three low-pressure holes are arranged from top to bottom as the first low-pressure hole, the fluctuating low-pressure hole, and the second low-pressure hole. The first low-pressure hole is located at 0.866R in the direction of the pipe cross-section radius, where R is the pipe radius. The second low-pressure hole and the first low-pressure hole are centrally symmetrical about the back flow surface, and the fluctuating low-pressure hole is located at the midpoint.

6. The steam mass flow measurement device based on the fiber optic interferometry principle according to claim 1, characterized in that, The ratio of the width of the flow-blocking surface to the inner diameter of the pipe is 0.

28.

7. The steam mass flow measurement device based on the fiber optic interferometry principle according to claim 1, characterized in that, It also includes a display module, which is connected to the processor and is used to display the results calculated by the processor.

8. A method for measuring steam mass flow rate based on the principle of fiber optic interferometry, characterized in that, The measurement method uses the measuring device described in claim 1, and the specific steps are as follows: a. When the fluid in the pipe flows through the obstructing fluid, two rows of regularly arranged vortices are alternately released on both sides behind the obstructing fluid. b. The light wave emitted by the light source is split into two light wave signals with the same frequency by the beam splitter. These two light wave signals are transmitted into the low-pressure cavity and the high-pressure cavity respectively through the collimating lens and the lower transparent glass through the same distance of the input optical fiber. c. When steam flows through the pipe and enters the high-pressure chamber and the low-pressure chamber, the high-pressure chamber sensing fiber and the low-pressure sensing fiber are subjected to different pressures and undergo forced vibration. The optical wave signal is modulated by this vibration and the phase changes. After passing through the coupler and the upper transparent glass, the optical wave signal is transmitted to the optical fiber interference module through the output optical fiber of the same distance. d. The two light wave signals will form obvious interference fringes at the fiber optic interference module. After being detected by the photodetector, the frequency signal information of the movement and change of the detected interference fringes will be transmitted to the processor. e. After orientation identification and calculation, the processor obtains the fiber interference vibration frequency and the fiber interference differential pressure value. The fiber interference vibration frequency is consistent with the vortex shedding frequency f. The average differential pressure is calculated according to formula 4. Calculate the mass flow rate Q of the steam fluid according to Formula 8. m ; In the formula: Q m —Mass flow rate of steam in the pipeline, kg / s; ρ m —Average density of wet steam in the pipeline, kg / m³ 3 ; f—the vortex frequency in the pipe, in Hz; ε—the coefficient of expansion of the medium being measured in the pipeline. For compressible fluids, ε<1; ε is obtained by looking up a table. —The average differential pressure between the high-pressure chamber and the low-pressure chamber within the fluid-resistant cavity, in Pa; K1—The vortex flowmeter instrument coefficient after compensation and correction; K2—Corrected flow coefficient; The values ​​of K1 and K2 were determined during the experiment. wet steam mass flow rate q m The formula for calculating frequency f is as follows: The average density of wet steam is obtained from formula 3: The wet steam mass flow rate is obtained from formulas 4 and 5: K m =K1K2 2 e 2 (7) The wet steam mass flow rate is obtained from formulas 6 and 7: In the formula, A is the cross-sectional area of ​​the pipe, and K m K is the mass flow meter coefficient, a physical quantity related to the shape and size of the vortex generator. m The value was obtained through experimental measurement and calibration.

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