CN107389974A - Gas-Liquid Slug Flow structure flow velocity acoustic-electric bimodal measuring method - Google Patents

Abstract

The invention relates to an acoustic-electric dual-mode measurement method for flow velocity in a gas-liquid slug flow structure, which is realized by using a dual-crystal ultrasonic transducer and an electrical sensor, including: collecting the water content of the electrical sensor and the Doppler frequency shift signal of the ultrasonic sensor ;Calculate the average value of water content th _H within the sampling time, use th _H as the threshold value of the water content to divide the fluid area, and use the water content series of the liquid elastic area and the gas elastic area to calculate the average water content of the liquid elastic area and the average water content in the aeroelastic zone And divide the fluid area into aeroelastic area, mixing area and liquid elastic area; use empirical mode decomposition to perform high frequency denoising processing on ultrasonic Doppler frequency shift signal; use empirical mode decomposition again to divide into several Eigenmode function; calculate the Doppler average frequency shift within the time range of the liquid warhead, that is, the mixing zone, the Doppler average frequency shift within the liquid elastic zone time range, and the Doppler average frequency shift within the liquid film time range ; Calculate the structure velocity of the slug flow.

Description

Acoustic-electric dual-mode measurement method for flow velocity in gas-liquid slug flow structure

technical field

The invention belongs to the technical field of fluid measurement, and relates to a combined measurement method of an ultrasonic sensor and an electrical sensor. By decomposing Doppler test signals, the undisturbed acquisition of the structural flow velocity of gas-liquid slug flow is realized.

Background technique

Gas-liquid two-phase flow widely exists in industrial production processes such as petroleum, nuclear power units, and chemical industry. Compared with single-phase flow, its flow process presents complex randomness, especially when the flow rate is high, it is easy to form an intermittent flow pattern. When the interaction between the gas-liquid two phases is more obvious, the severe pressure fluctuation will cause a strong impact on the pipeline, and even cause a safety accident in severe cases. Therefore, the measurement of the flow velocity of gas-liquid slug flow structure is of great significance for model establishment, prediction and control of flow pattern transformation, production safety and optimization.

The intermittent and transient nature of slug flow poses great challenges for flow velocity measurement. Traditional testing methods mostly use intrusive measurement methods, such as conductivity probes, hot film probes, etc., which will disturb the flow process while obtaining flow parameters and affect the measurement accuracy. In the process of scientific research and industrial production, it is urgent to use non-disturbance measurement technology to accurately obtain the process parameters of two-phase flow. Therefore, electrical methods and ultrasonic methods have attracted much attention due to their non-invasive, simple sensor structure, convenient installation, and low cost.

According to the structure, shape and excitation mode of the sensor, the electrical measurement method is divided into various forms such as annular conductance array, capacitive plate, electrical impedance tomography, etc., among which the annular conductance array is established by applying a constant excitation voltage on the excitation electrode pair. The electrical sensitive field, when the holdup of the measured fluid changes, the impedance characteristics of the sensitive field will change accordingly, and the measurement of the holdup of the measured fluid can be realized by obtaining the potential difference on the measuring electrode pair, which has a good application prospect. As a non-invasive method, ultrasonic testing uses the reflection and refraction of ultrasound caused by the different acoustic impedances of different media to measure the flow velocity of fluids, mainly including correlation methods, time difference methods, and Doppler methods. It has a wide range of applications in medicine and fluid measurement. Ultrasonic Doppler technology based on continuous wave is based on the Doppler effect. Ultrasonic waves are emitted into the fluid by ultrasonic transducers, reflected or scattered by the discrete phases (droplets or bubbles) moving in multiphase fluids, and then emitted by the ultrasonic transducers. take over. The frequency difference between the incident sound wave and the received sound wave is proportional to the average flow velocity of discrete phase scattering particles in the measurement area. However, in the actual flow process, there are complex holdup distributions and flow velocity profiles in the fluid, especially the gas bombs and liquid bombs that appear intermittently in the slug flow, causing the fluid holdup and flow velocity to fluctuate violently with time. Therefore, the Doppler frequency shift signal is the superposition of the ultrasonic Doppler effect caused by scattering particles with different flow velocities at different positions, and it is an aliasing signal containing multi-frequency scale fluctuations. These fluctuations on different frequency scales reflect different flow velocities in the fluid flow process. Therefore, electrical sensors are used in combination with ultrasonic Doppler sensors to obtain holdup and flow velocity information of two-phase flow. Through the signal processing technology and the joint analysis method, the acquisition of the structural flow velocity of the gas-liquid slug flow is finally realized.

Contents of the invention

The purpose of the present invention is to use ultrasonic Doppler sensor and conductivity sensor to obtain the flow velocity and water content information of two-phase flow on the basis of the prior art, and to provide a new flow velocity of gas-liquid slug flow structure based on signal empirical decomposition measurement method. Technical scheme of the present invention is as follows:

An acoustic-electric dual-mode measurement method for flow velocity in a gas-liquid slug flow structure, which is realized by using a dual-crystal ultrasonic transducer and an electrical sensor. The dual-crystal ultrasonic transducer is used to obtain two-phase flow ultrasonic Doppler frequency shift signals, and the electrical sensor For obtaining the water content signal, the dual-crystal ultrasonic transducer adopts the structure of transmitting and receiving on the same side, and is installed at the bottom of the horizontal test pipe to ensure that the angle between the direction of the ultrasonic sound beam and the flow direction is θ; the electrical sensor consists of Four ring-shaped metal electrodes are embedded in the inner wall of the test pipe, and are installed in the test pipe together with the ultrasonic transducer. The measurement method includes the following steps:

1) Acquire the water content signal H(t), t∈(0,T) of the electrical sensor and the Doppler frequency shift signal f _d (t), t∈(0,T) of the ultrasonic sensor, where T is the sampling time ;

2) Calculate the average value of moisture content within the sampling time Use th _H as the holdup threshold to divide the fluid into regions: if the water cut at a certain moment is greater than th _H , then the holdup at that moment is the water cut when the liquid elastic region flows through the electrical sensor, otherwise the holdup at this moment is is the water content when the aeroelastic zone flows through the electrical sensor, namely Among them, H _nl and H _ng are the water content series of the liquid elastic region and the gas elastic region respectively;

3) Use H _nl and H _ng to calculate the average water content in the liquid elastic zone and the average water content in the aeroelastic zone and Among them, T _l and T _g are the time experienced in the liquid elastic region and the gas elastic region respectively within the sampling time; and As the holdup threshold, the fluid is divided into two regions: if the water cut at a certain moment is less than Then at this moment, the aeroelastic zone passes through the electrical sensor. If the water content at a certain moment is greater than and less than Then at this moment, the mixture passes through the electrical sensor, otherwise, the liquid elastic zone passes through the electrical sensor, that is,

Thus, the start time T1 of the liquid _- elastic zone, the stop time T2 _of the mixing zone, the start time T3 of the aeroelastic zone, and the stop time of the aeroelastic zone can be respectively obtained, that is, the start time T4 _of the next liquid _- elastic zone;

4) Use empirical mode decomposition to perform high-frequency denoising processing on the ultrasonic Doppler frequency shift signal: based on the method of empirical mode decomposition, the ultrasonic Doppler frequency shift signal f _d (t),t∈(0, T) is decomposed step by step into the sum of several intrinsic mode functions IMF _j (t), j=1, 2,...,n and trend function r _n (t): Where n is the number of intrinsic mode functions obtained by decomposition, and the cross-correlation method is used to calculate each intrinsic mode function IMF _j (t), j=1,2,...,n and the original Doppler frequency shift signal The correlation coefficient of the original Doppler frequency shift signal in the first m stages is removed, and the high-frequency eigenmode function component whose correlation coefficient with the original Doppler frequency shift signal is less than the threshold th _cc ; m generally takes a value of 3-4, and th _cc generally takes a value of 0.2 -0.3; add the eigenmode function whose correlation coefficient with the original Doppler frequency shift signal in the first m level is greater than or equal to th _cc , the remaining nm level eigenmode function and the trend function r _n (t) and, recombined into a new signal to be processed f _d '(t),t∈(0,T);

5) Use the method of empirical mode decomposition again to decompose the signal f _d '(t), t∈(0,T) into several intrinsic mode functions IMF _i (t), i=1,2,..., The sum of N and the trend term function r _N (t), namely Where N is the number of intrinsic mode functions obtained by decomposition; select the first four intrinsic mode functions IMF _i (t), i=1,2,3,4 as the principal components;

6) Perform short-time Fourier transform on the principal component to obtain its time spectrum, and through joint analysis with the electrical water content signal, determine the structural flow velocity of the fluid reflected by the principal component: the first-order intrinsic mode function IMF ₁ ( t) is the highest frequency component, reflecting the propagation velocity of the liquid bomb in the slug flow; the second-order intrinsic mode function IMF ₂ (t) covers the basic covering liquid elastic area, and the first-order intrinsic mode function IMF ₁ (t) together reflect the average flow velocity in the liquid elastic region; the third and fourth order intrinsic mode functions IMF ₃ (t) & IMF ₄ (t) appear in the liquid film region, which are related to the droplet entrainment and reflect the liquid film fluid velocity in the zone;

7) Perform fast Fourier transform on the first-order eigenmode function components and calculate the Doppler average frequency shift within the time range of the liquid warhead, that is, the mixing zone: Fast Fourier transform the sum of the first and second order eigenmode function components and calculate the Doppler mean frequency shift over the time scale of the hydroelastic region Fast Fourier transform the sum of the third and fourth order eigenmode function components and calculate the Doppler mean frequency shift over the time scale of the liquid film where f _d1 , f _d2 , and f _d3 are the frequencies corresponding to IMF ₁ (t), IMF ₁ (t)+IMF ₂ (t), and IMF ₃ (t)+IMF ₄ (t), that is, the frequencies at different scales Ultrasonic Doppler frequency shift, S _d1 (f _d1 ), S _d2 (f _d2 ), S _d3 (f _d3 ) are their corresponding energy spectrum intensities;

8) According to the basic principle of the Doppler effect, calculate the structural velocity of the slug flow: where the propagation velocity of the liquid bomb is: The average velocity of the liquid bomb is: The average flow velocity in the liquid film region is: Where f ₀ is the excitation frequency of the ultrasonic reflection probe, θ is the angle between the direction of the ultrasonic beam and the horizontal direction, and c is the speed of sound in the fluid.

The substantive features of the present invention are: using the electrical sensor to obtain the water content fluctuation signal of the gas-liquid slug flow; Puller shifted signal. Due to the intermittent appearance of gas and liquid bombs with obvious flow velocity differences in slug flow, the water cut and flow velocity fluctuate violently with time. In addition to the existence of flow velocity profile and holdup distribution, the Doppler frequency shift signal is the superposition of ultrasonic effects from scatterers with different flow velocities at different positions, and it is a superposition signal of multi-frequency fluctuations. Therefore, a signal processing method based on empirical mode decomposition is used to decompose the Doppler signal into several eigenmode functions, and the cross-correlation algorithm is used to determine the principal component reflecting the most significant feature of the signal, and the short-time Fourier analysis of the principal component is carried out. The leaf transformation analysis, combined with the reflection of the water content on the intermittent characteristics of the slug flow, finally realizes the measurement of the flow velocity of the slug flow structure. Beneficial effect and advantage of the present invention are as follows:

1. This method is a non-disturbance measurement method, which will not cause any disturbance to the fluid;

2. The combined measurement of electrical sensor and ultrasonic Doppler sensor can obtain a more comprehensive description of the fluid flow process;

3. Realize the measurement of the structural flow velocity of the fluid through signal processing technology and joint analysis method, which is simple and easy;

4. The measurement is convenient, fast and low cost.

Description of drawings

The following drawings describe selected embodiments of the present invention, all of which are illustrative and not exhaustive or limiting, wherein:

The structure schematic diagram of ultrasonic Doppler sensor in the measurement method of the present invention in Fig. 1;

In Fig. 2 measurement method of the present invention, the structural representation of conductance ring sensor;

Schematic diagram of the structure of the slug flow unit in the measuring method of the present invention in Fig. 3;

Empirical mode decomposition flowchart in the measuring method of the present invention in Fig. 4;

Fig. 5 is the calculation steps of the flow velocity of the slug flow structure in the measurement method of the present invention.

detailed description

Embodiments of the present invention will be described in detail below in conjunction with the drawings.

Fig. 1 is a schematic structural diagram of a continuous wave ultrasonic Doppler sensor in the measurement method of the present invention. The ultrasonic Doppler probe used in the patent of the present invention adopts a dual-crystal ultrasonic transducer with integrated transceiver, which contains a transmitting piezoelectric ceramic chip 3a and a receiving piezoelectric ceramic chip 3b, which are respectively attached to the acoustic-electric coupling materials 3c and 3d . The acoustic-electric coupling material is in direct contact with the fluid, and is installed at an angle _θ0 between the horizontal pipe 1, so that the ultrasonic beam path and the incoming flow direction 0 of the two-phase flow 2 maintain an angle θ. A sound-insulating material 4 is added between the acoustic-electric coupling materials 3c and 3d to prevent interference between transmitting and receiving sound waves. The dual-crystal ultrasonic transducer is installed at the bottom of the horizontal pipeline. The transmitting piezoelectric ceramic chip 3 a emits ultrasonic waves, and the sound wave propagates in the fluid 2 , and is received by the receiving piezoelectric ceramic chip 3 b after being reflected and scattered by the discrete phase in the measurement space 5 . The frequency difference between the received sound wave and the emitted sound wave reflects the flow velocity information of the fluid in the measurement space 5 .

Fig. 2 is a structural schematic diagram of the conductance ring sensor in the measuring method of the present invention. The electrical sensor used in the patent of the present invention consists of four ring-shaped metal electrodes (1, 2, 3, 4) embedded in the inner wall 0 of the pipeline, wherein electrodes 1 and 4 are excitation electrode pairs, and electrodes 2 and 3 are measurement electrode pairs. By injecting a constant square-wave excitation current into electrode 1 and grounding electrode 4, a stable electrical sensitive field can be formed between electrodes 1 and 4. When the medium holdup and distribution change when the fluid flows through the sensitive field, the potential difference between electrode 2 and electrode 3 changes, and the measurement of the fluid holdup can be realized by measuring the potential difference.

Fig. 3 is a schematic diagram of the structure of the slug flow unit in the measurement method of the present invention. The gas-liquid slug flow unit structure includes a liquid elastic area 2 and an air elastic area 3 , and the fluid turbulence intensity and flow velocity in the liquid elastic area 2 are higher than those in the air elastic area 3 . Since the head of the liquid bomb area continuously picks up the liquid that fell off from the previous liquid bomb, when the high-speed liquid merges with the low-speed liquid, a high-speed vortex is formed at the front end of the liquid bomb, and a large number of discrete bubbles are distributed in the liquid phase. For Mixed Zone 1. At the tail of the liquid bomb, the liquid continuously returns to the liquid film area 4 due to gravity, and the liquid experiences a faster deceleration process in this stage. At the front end of the gas bomb, the fluctuation of the gas-liquid interface is strong, resulting in entrainment of liquid droplets. As time goes by, the fluid flow gradually stabilizes, and it flows slowly like a wavy flow. In the slug flow unit structure, the start time of the liquid elastic zone ₂ is T1, the stop time of the mixing zone ₁ is T2, the start time of the aeroelastic zone ₃ is T3 and the stop time of the aeroelastic zone 3 (next The start time of the liquid elastic zone) is T ₄ . The propagation velocity of the liquid bomb in the slug flow unit structure is V _T , the average velocity of the liquid elastic zone 2 is V _S , and the average velocity of the liquid film zone 4 is V _f .

Fig. 4 is a flow chart of empirical mode decomposition in the measurement method of the present invention. Empirical mode decomposition is an adaptive time-frequency analysis method. Through the screening process, the fluctuations of different scales in the signal x(t) are separated step by step, and a series of intrinsic mode functions (IMF) with different scales are generated. , stop decomposing until the residual value sequence r _n (t) is a monotone function. Each IMF needs to meet two basic conditions: 1) the number of signal extreme points (including maximum and minimum points) is equal to the number of zero-crossing points, or at most the difference is 1; 2) the signal is at any time point The mean value of the upper envelope determined by the local maximum and the lower envelope determined by the local minimum point is zero, and the signal is locally symmetrical about the time axis. The conditions mentioned above are the stopping conditions of each screening process.

Fig. 5 is a flow chart of calculation steps for obtaining the flow velocity of a slug flow structure by the ultrasonic and electrical combined sensor of the present invention. Taking the gas-water two-phase flow as an example, the calculation steps for obtaining the flow velocity of the slug flow structure by the electrical and ultrasonic data joint analysis method of the present invention are as follows:

Step 1: Collect the water content signal H(t), t ∈ (0, T) of the electrical sensor and the Doppler frequency shift signal f _d (t), t ∈ (0, T) of the ultrasonic sensor, where T is the sampling time;

Step 2: According to the water cut signal, the fluid of gas-liquid slug flow is divided into regions.

1) Calculate the average value of moisture content within the sampling time Use th _H as the holdup threshold to divide the fluid once: if the water cut at a certain moment is greater than th _H , then the holdup at that moment is the water cut when the liquid elastic region flows through the electrical sensor, otherwise the holdup at this moment is The rate is the water content when the aeroelastic region flows through the electrical sensor, that is

Among them, H _nl and H _ng are the water content series of the liquid elastic region and the gas elastic region respectively;

2) Use H _nl and H _ng to calculate the average water content in the liquid elastic zone and the average water content in the aeroelastic zone and Among them, T _l and T _g are the time experienced in the liquid elastic region and the gas elastic region respectively within the sampling time. Will and As the holdup threshold, the fluid is divided into two regions: if the water cut at a certain moment is less than Then at this moment, the aeroelastic zone passes through the electrical sensor. If the water content at a certain moment is greater than and less than Then at this moment, the mixture passes through the electrical sensor, otherwise, the liquid elastic zone passes through the electrical sensor, that is,

Thus, the start time T1 of the liquid _- elastic zone, the stop time T2 _of the mixing zone, the start time T3 _of the aeroelastic zone, and the stop time of the aeroelastic zone (the start time of the next liquid _- elastic zone) T4 can be obtained respectively;

Step 3: Decompose the Doppler frequency shift signal based on the method of empirical mode decomposition, and extract the structural velocity of the slug flow.

1) Denoising the Doppler frequency shifted signal f _d (t), t ∈ (0, T). In general, the Doppler frequency shift signal contains high-frequency noise components, which seriously affect the analysis accuracy, so denoising is required. First, using the empirical mode decomposition method, the ultrasonic Doppler frequency shift signal f _d (t), t∈(0, T) is decomposed step by step into several intrinsic mode functions IMF _j (t), j=1, The sum of 2,...,n and the trend function r _n (t):

where n is the number of eigenmode functions. It is worth noting that the essence of empirical mode decomposition is a screening process. The termination condition of screening, that is, each IMF needs to meet two basic conditions is difficult to meet. Generally, it is necessary to follow the Cauchy convergence quasi-group, by limiting the The standard deviation SD between terminates the screening, that is:

Among them, h _1,k-1 , h _1,k are two consecutive decomposition result sequences in the screening process, SD generally takes a value in the range of 0.2-0.3, and its selection will affect the decomposed intrinsic mode function the number of . The correlation coefficient between each eigenmode function and the original Doppler frequency shift signal is calculated by using the cross-correlation method. The larger the correlation coefficient is, the more the eigenmode function can reflect the most significant feature of the signal. Therefore, according to the actual high-frequency noise situation, the correlation coefficient threshold th _cc is selected, and the first m high-frequency eigenmode function components are selected for judgment: if the first m high-frequency eigenmode function components and the original Doppler shift signal If the correlation coefficient is less than th _cc , choose to remove, otherwise keep. In general, high-frequency noise is decomposed first because of the highest frequency, and the correlation coefficient with the original Doppler frequency shift signal is small, so m generally takes a value of 3-4, and th _cc generally takes a value of 0.2-0.3 . Then add the eigenmode functions whose correlation coefficient with the original Doppler frequency shift signal in the first m levels is greater than or equal to th _cc , the remaining nm-level eigenmode functions and the trend function r _n (t), Recombine into a new signal to be processed f _d '(t),t∈(0,T);

2) Decompose the new signal to be processed f _d '(t), t∈(0, T) into quadratic empirical mode decomposition, then the signal can be expressed as several intrinsic mode functions IMF _i (t), i=1 ,2,...,N and the sum of the trend function r _N (t):

Where N is the number of intrinsic mode functions in the second decomposition. Each IMF _i (t) contains different frequency components from high to low of the signal, and each IMF represents a different time-scale feature component in the original signal. Because the empirical mode decomposition method can also be called the principal component analysis method, under normal circumstances, the previous eigenmode function components obtained by the secondary decomposition often concentrate the most significant and important information in the signal. Therefore, the first four eigenmode functions IMF _j (t), j=1, 2, 3, 4 are selected as the principal components;

3) Use the short-time Fourier transform method to conduct time-frequency analysis on the principal components, and combine the results of the partitioning of the fluid by the water content signal in step 2 to determine the structural flow velocity of the fluid reflected by the principal components. Through the combined analysis of electrical and ultrasonic information, it is determined that the first-order intrinsic mode function IMF ₁ (t) is the highest frequency component, which appears at the head of the liquid-elastic region and reflects the propagation velocity of the liquid-elastic in the slug flow; The second-order intrinsic mode function IMF ₂ (t) covers the basic coverage of the liquid elastic region, and the first-order intrinsic mode function IMF ₁ (t) together reflects the average flow velocity of the liquid-elastic region; the third and fourth-order intrinsic mode functions The eigenmode functions IMF ₃ (t) & IMF ₄ (t) appear in the liquid film region, which are related to the droplet entrainment and reflect the fluid velocity in the liquid film region;

4) Perform fast Fourier transform on the first-order eigenmode function components and calculate the Doppler average frequency shift within the time range of the liquid warhead (mixing region): Fast Fourier transform the sum of the first and second order eigenmode function components and calculate the Doppler mean frequency shift over the time scale of the hydroelastic region Fast Fourier transform the sum of the third and fourth order eigenmode function components and calculate the Doppler mean frequency shift over the time scale of the liquid film Where f _d1 , f _d2 , f _d3 are respectively The corresponding frequency of IMF ₁ (t)+IMF ₂ (t), IMF ₃ (t)+IMF ₄ (t), that is, the ultrasonic Doppler shift at different scales, Sd1(f _d1 ), S _d2 (f _d2 ) , S _d3 (f _d3 ) are their corresponding energy spectrum intensities, and T ₁ , T ₂ , T ₃ , T ₄ are all obtained from step 2.

5) According to the basic principle of the Doppler effect, calculate the structural velocity of the slug flow: where the propagation velocity of the liquid bomb is: The average velocity of the liquid bomb (and at the same time the total superficial velocity of the slug flow) is: The average flow velocity in the liquid film region is: Where f ₀ is the excitation frequency of the ultrasonic reflection probe, θ is the angle between the direction of the ultrasonic beam and the horizontal direction, and c is the speed of sound in the fluid.

Claims (1)

1. A gas-liquid elastic flow structure flow velocity acoustoelectric bimodal measurement method is realized by adopting a bimorph ultrasonic transducer and an electrical sensor, wherein the bimorph ultrasonic transducer is used for acquiring two-phase flow ultrasonic Doppler frequency shift signals, the electrical sensor is used for acquiring water content signals, the bimorph ultrasonic transducer adopts a receiving and transmitting integrated homonymy structure, is arranged at the bottom of a horizontal test pipeline and ensures that the included angle between the ultrasonic beam direction and the flow direction is theta; the electric sensor is composed of four annular metal electrodes embedded in the inner wall of a test pipeline, and is simultaneously installed in the test pipeline together with the ultrasonic transducer, and the measuring method comprises the following steps:

1) collecting water content signals H (T), T ∈ (0, T) of the electrical sensor and Doppler frequency shift signals f of the ultrasonic sensor_d(T), T ∈ (0, T), where T is the sampling time;

2) calculating the mean value of the water content in the sampling timeWill th_HAnd (3) performing regional division on the fluid as a percentage threshold: if the water content is greater than th at a certain time_HIf the water content at the moment is the water content when the liquid elastic area flows through the electrical sensor, otherwise, the water content at the moment is the water content when the gas elastic area flows through the electrical sensor, namelyWherein H_nl，H_ngRespectively is a water content sequence of the liquid elastic area and the gas elastic area;

3) by means of H_nl、H_ngRespectively calculating the mean value of the water content of the liquid elastic areaMean value of water content of gas bomb mixing area Andwherein T is_l，T_gRespectively the time of the liquid bomb region and the time of the gas bomb region in the sampling time; will be provided withAndas the percentage of contentPerforming secondary region division on the fluid by using a threshold value: if the water content at a certain time is less thanThe time is that the air elastic area passes through the electrical sensor, and if the water content at a certain time is greater than that at a certain timeAnd is less thanThen the time is when the mixture passes through the electrical sensor, otherwise the liquid-elastic region passes through the electrical sensor, i.e.

The starting times T of the liquid elastic areas can be obtained respectively₁Stop time T of the mixing zone₂Start time T of the aeroelastic zone₃And the stopping time of the gas-bomb zone, i.e. the starting time T of the next liquid-bomb zone₄；

4) Carrying out high-frequency denoising treatment on the ultrasonic Doppler frequency shift signal by using empirical mode decomposition: based on empirical mode decomposition method, ultrasonic Doppler frequency shift signal f is obtained_d(T), T ∈ (0, T) are decomposed into a plurality of intrinsic mode functions IMF in a step-by-step manner_j(t), j ═ 1, 2.. times, n and trend function r_nSum of (t):wherein n is the number of intrinsic mode functions obtained by decomposition, and each intrinsic mode function IMF is calculated by utilizing a cross-correlation method_j(t), j is 1, 2.. times, n is the correlation coefficient of the original Doppler frequency shift signal, and the correlation coefficient of the original Doppler frequency shift signal in the previous m stages is removed and is smaller than a threshold th_ccA high frequency eigenmode function component of (a); m is generally 3-4 th_ccGenerally, the value is 0.2-0.3; the correlation coefficient with the original Doppler frequency shift signal in the previous m stages is greater than or equal to th_ccIntrinsic mode function of (1), residualn-m order eigenmode function and trend function r_n(t) are summed and recombined to a new signal f 'to be processed'_d(t),t∈(0,T)；

5) The signal f 'is decomposed by using empirical mode again'_d(T), T ∈ (0, T) is decomposed into several eigenmode functions IMF_i(t), i ═ 1, 2.., N, and a trend term function r_N(t) isWherein N is the number of intrinsic mode functions obtained by decomposition; selecting the first 4-level intrinsic mode function IMF_i(t), i ═ 1,2,3,4 as the principal components;

6) and carrying out short-time Fourier transform on the main components to obtain time spectrum diagrams thereof, and determining the structural flow rates of the fluids respectively reflected by the main components through joint analysis with the electrical water content signals: first order Intrinsic Mode Function (IMF)₁(t) is the highest frequency component, reflecting the propagation velocity of the liquid bullet in the bullet flow; second order Intrinsic Mode Function (IMF)₂(t) covering the substantially covered liquid-elastic region, and the first order intrinsic mode function IMF₁(t) together reflect the average flow velocity of the liquid elastic zone; third and fourth order intrinsic mode functions IMF₃(t)&IMF₄(t) occurs in the liquid film zone, is related to the droplet entrainment condition, and reflects the fluid flow velocity in the liquid film zone;

7) performing fast Fourier transform on the first-stage eigenmode function component and calculating Doppler average frequency shift in a liquid bullet part, namely a mixing region time range:performing fast Fourier transform on the sum of the first and second stage eigenmode function components and calculating the Doppler mean frequency shift in the time range of the liquid elastic regionPerforming fast Fourier transform on the sum of the third and fourth order eigenmode function components and calculating the Doppler mean frequency shift in the liquid film time rangeWherein f is_d1，f_d2，f_d3Are respectively IMF₁(t)，IMF₁(t)+IMF₂(t)，IMF₃(t)+IMF₄(t) corresponding frequencies, i.e. ultrasonic Doppler shifts at different scales, S_d1(f_d1)，S_d2(f_d2)，S_d3(f_d3) Respectively, the corresponding energy spectrum intensities;

8) according to the basic principle of the Doppler effect, the structural flow velocity of the bullet flow is calculated: wherein the propagation speed of the liquid bomb is as follows:the average velocity of the liquid slugs is:the average flow velocity of the liquid membrane zone was:wherein f is₀The excitation frequency of the ultrasonic reflection probe is theta, the included angle between the ultrasonic beam direction and the horizontal direction is theta, and c is the sound velocity in the fluid.