CN107389974B - Gas-Liquid Slug Flow structure flow velocity acoustic-electric bimodal measurement method - Google Patents
Gas-Liquid Slug Flow structure flow velocity acoustic-electric bimodal measurement method Download PDFInfo
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Abstract
The present invention relates to a kind of Gas-Liquid Slug Flow structure flow velocity acoustic-electric bimodal measurement methods, are realized using twin crystal ultrasonic transducer and electric sensor, include: acquiring the moisture content of electric sensor and the doppler shifted signal of ultrasonic sensor；Calculate the moisture content mean value th in the sampling timeH, by thHRegion division is carried out to fluid as threshold value containing rate, calculates separately the area Ye Dan moisture content mean value using the gentle moisture content sequence for playing area in the area Ye DanThe gentle moisture content mean value for playing areaAnd second zone is carried out to fluid and is divided into the area Qi Dan, mixed zone and the area Ye Dan；Using empirical mode decomposition, high frequency denoising is carried out to ultrasonic Doppler frequency shift signal；It is again several intrinsic mode functions using empirical mode decomposition；Calculate Doppler's average frequency shift in liquid bullet portion, that is, mixed zone time range, Doppler's average frequency shift in the area Ye Dan time range, Doppler's average frequency shift degree in liquid film time range；Calculate the structure flow velocity of slug flow.
Description
Technical field
The invention belongs to fluid measurement technical field, it is related to a kind of ultrasonic sensor and electric sensor combined type measurement side
Method tests signal by decomposing Doppler, realizes that the non-disturbance formula of the structure flow velocity of Gas-Liquid Slug Flow obtains.
Background technique
Biphase gas and liquid flow is widely present in the industrial processes such as petroleum, nuclear power unit, chemical industry, compared with single-phase flow,
Complicated randomness, especially the interval flow pattern easy to form when flow velocity is higher is presented in its flow process, at this time gas-liquid two-phase it
Between interaction it is more obvious, violent pressure oscillation causes strong impact to pipeline, even causes safe thing when serious
Therefore.Therefore, to the measurement of Gas-Liquid Slug Flow structure flow velocity for the prediction and control of model foundation, Regime transition, production safety
It is of great significance with optimization.
Intermittence and transient state in slug flow flow process are that flow velocity measurement brings huge challenge.Traditional test
Means mostly use intrusive measurement method, such as conducting probe, hotting mask probe, can be to flowing over while obtaining flow parameter
Journey generates disturbance, influences measurement accuracy.In scientific research and industrial processes, it is badly in need of quasi- using non-disturbance formula measuring technique
Really obtain the procedure parameter of two phase flow, thus electric method, ultrasonic method are due to its non-intruding, sensor structure is simple, it is easy for installation,
It is low in cost and be concerned.
Electric measurement method is divided into annular photoconductive array, capacitor according to the structure of sensor, shape, the difference of energisation mode
The diversified forms such as pole plate, electrical impedance tomography, wherein annular photoconductive array is by constant swashing upper apply in excitation electrode
Voltage Establishment electricity sensitivity field is encouraged, when detected fluid containing rate when changing, the impedance operator of sensitivity field changes therewith,
Measurement of the detected fluid containing rate is realized to upper potential difference by obtaining measuring electrode, is had a good application prospect.Ultrasound inspection
It surveys and is used as a kind of non-invasive methods, occur when being propagated in a fluid using ultrasound caused by different medium acoustic impedance difference anti-
Phenomena such as penetrating, reflecting and the flow velocity of fluid is measured, mainly include correlation method, time difference method, Doppler method etc., medicine,
Have in fluid measurement and is widely applied very much.Ultrasonic Doppler technique based on continuous wave be based on Doppler effect, ultrasonic wave by
Ultrasonic transducer is emitted into fluid, after the reflection or scattering of the discrete phase (drop or bubble) moved in heterogeneous fluid by
Ultrasonic transducer receives.Incident acoustic wave and the average flowing for receiving frequency difference and discrete phase scattering particles in measured zone between sound wave
Speed is directly proportional.There is complexity but in practical flow process, in fluid contains rate distribution and fluid velocity profile, is especially playing shape
Intermittent gas bullet and liquid bullet in stream, there are big ups and downs containing rate and flow velocity in that causes fluid at any time.Therefore, Doppler's frequency
Shifting signal is that have the superposition of scattering particles different in flow rate to ultrasonic Doppler effect on different location, is a kind of comprising multifrequency
The aliasing signal of rate scale fluctuation.Different flow velocitys in the fluctuation reflection process fluid flow of these different frequency scales.Cause
This, electric sensor and ultrasonic Doppler sensor combinations are used, and obtain two phase flow contains rate and flow rate information.Pass through signal
Processing technique and conjoint analysis method, the acquisition of the final structure flow velocity for realizing Gas-Liquid Slug Flow.
Summary of the invention
The purpose of the present invention is on the basis of existing technology, obtained using ultrasonic Doppler sensor and conductivity sensor
The flow velocity and moisture content information of two phase flow provide a kind of survey of new Gas-Liquid Slug Flow structure flow velocity decomposed based on signal experience
Amount method.Technical scheme is as follows:
A kind of Gas-Liquid Slug Flow structure flow velocity acoustic-electric bimodal measurement method is sensed using twin crystal ultrasonic transducer and electricity
Device realizes that for twin crystal ultrasonic transducer for obtaining two phase flow ultrasonic Doppler frequency shift signal, electric sensor is aqueous for obtaining
Rate signal, the twin crystal ultrasonic transducer use the same side structure of transceiver, are installed in horizontal test duct bottom and protect
The angle for demonstrate,proving ultrasonic wave acoustic beam direction and flow direction is θ；The electric sensor is embedded in survey by four circular metal electrodes
Inner wall of the pipe composition is tried, is installed on simultaneously with ultrasonic transducer in test pipeline, measurement method comprises the following steps:
1) the moisture content signal H (t) of electric sensor, the doppler shifted signal of t ∈ (0, T) and ultrasonic sensor are acquired
fd(t), (0, T) t ∈, wherein T is the sampling time；
2) the moisture content mean value in the sampling time is calculatedBy thHAs threshold value containing rate to fluid into
Row region division: if some time inscribes moisture content greater than thH, then this when the area containing Shuai Weiyedan inscribed when flowing through electric sensor
Moisture content, otherwise this when the area containing Shuai Weiqidan inscribed moisture content when flowing through electric sensor, i.e.,Wherein Hnl, HngThe respectively gentle moisture content sequence for playing area in the area Ye Dan；
3) H is utilizednl、HngCalculate separately the area Ye Dan moisture content mean valueThe gentle moisture content mean value for playing area WithWherein Tl, TgRespectively in gentle bullet area, sampling time Nei Yedan area
The time of experience；It willWithSecond zone division is carried out to fluid as threshold value containing rate: if certain moment moisture content is less thanThen the moment is the area Qi Dan by electric sensor, if certain moment moisture content is less thanAnd it is greater thanThen the moment is
Mixed zone is otherwise the area Ye Dan by electric sensor, i.e., by electric sensor
Thus T at the beginning of the area Ye Dan can be obtained respectively1, the stop timing T of mixed zone2, T at the beginning of the area Qi Dan3
And the stop timing in the area Qi Dan, i.e., T at the beginning of next area Ye Dan4；
4) empirical mode decomposition is utilized, high frequency denoising is carried out to ultrasonic Doppler frequency shift signal: being based on empirical modal
The method of decomposition, by ultrasonic Doppler frequency shift signal fd(t), t ∈ (0, T) is decomposed into several intrinsic mode function IMF step by stepj
(t), j=1,2 ..., n and trend function rn(t) sum:Wherein n be decompose obtain it is intrinsic
Mode function number calculates each intrinsic mode function IMF using cross-correlation methodj(t), j=1,2 ..., n and former Doppler's frequency
The related coefficient of shifting signal is less than threshold value th with the related coefficient of former doppler shifted signal in m grades before removalccHigh frequency it is intrinsic
Mode function component；The general value of m is 3-4, thccGeneral value is 0.2-0.3；In will be m grades first with former doppler shifted signal
Related coefficient be greater than or equal to thccIntrinsic mode function, remaining n-m grades of intrinsic mode function and trend function rn
(t) it sums up, is reassembled into new signal f to be processedd'(t),t∈(0,T)；
5) utilize the method for empirical mode decomposition by signal f againd' (t), t ∈ (0, T) is decomposed into several intrinsic mode letters
Number IMFi(t), i=1,2 ..., N and trend term function rN(t) sum, i.e.,Wherein N is to decompose
Obtained intrinsic mode function number；Choose preceding 4 grades of intrinsic mode function IMFi(t), i=1,2,3,4 is as principal component；
6) Short Time Fourier Transform is carried out to principal component and obtains its time-frequency spectrum, by dividing with electricity moisture content combined signal
Analysis, determines the structure flow velocity for the fluid that principal component reflects respectively: first order intrinsic mode function IMF1(t) for most high frequency at
Point, reflect the spread speed of liquid bullet in slug flow；Second level intrinsic mode function IMF2(t) covering liquid bullet area and first order sheet
Levy mode function IMF1(t) reflect the mean flow rate in the area Ye Dan together；The third level and fourth stage intrinsic mode function IMF3(t) and
IMF4(t) area Ye Dan is appeared in, it is related to drop entraimnent, reflect the area Ye Dan inner fluid speed；
7) to first order intrinsic mode function component carry out Fast Fourier Transform (FFT) and calculate liquid bullet portion i.e. mixed zone when
Between Doppler's average frequency shift in range:To the first order and second level intrinsic mode function point
The adduction of amount carries out Fast Fourier Transform (FFT) and calculates Doppler's average frequency shift in the area Ye Dan time rangeThe adduction of the third level and fourth stage intrinsic mode function component is carried out in quick Fu
Leaf transformation simultaneously calculates Doppler's average frequency shift in liquid bullet time rangeWherein fd1,
fd2, fd3Respectively IMF1(t), IMF1(t)+IMF2(t), IMF3(t)+IMF4(t) under corresponding frequency namely different scale
Ultrasonic Doppler frequency displacement, Sd1(fd1), Sd2(fd2), Sd3(fd3) it is respectively its corresponding energy spectral intensity；
8) according to Doppler effect basic principle, the structure flow velocity of slug flow: the wherein spread speed of liquid bullet is calculated are as follows:The average speed of liquid bullet are as follows:The mean flow rate in the area Ye Dan are as follows:Wherein f0For the driving frequency of ultrasonic reflections probe, θ is ultrasonic wave acoustic beam direction and horizontal direction
Angle, c are the velocity of sound in fluid.
Substantive distinguishing features of the invention are: the moisture content fluctuation signal of Gas-Liquid Slug Flow is obtained using electric sensor, by
The strong reflection of ultrasound is acted in gas phase, obtains the how general of Gas-Liquid Slug Flow using ipsilateral transceiver ultrasonic Doppler sensor
Strangle frequency shift signal.Since the obvious gas bullet of flow velocity difference in slug flow and liquid bullet intermittence occur, moisture content and flow velocity are at any time
Between fluctuate it is violent.In addition the presence of fluid velocity profile and the distribution containing rate, so that doppler shifted signal is that have on different location
There is scatterer different in flow rate to the superposition of ultrasonication, is a kind of superposed signal of multi-frequency fluctuation.Therefore, using based on warp
Doppler signal is decomposed into several intrinsic mode functions by the signal processing method for testing mode decomposition, true using cross correlation algorithm
Surely reflect the principal component of signal most significant feature, and Short Time Fourier Transform analysis is carried out to principal component, in conjunction with moisture content to bullet
The reflection of shape stream intermittent nature, the final measurement for realizing slug flow structure flow velocity.Beneficial effects of the present invention and advantage are as follows:
1. this method is non-disturbance formula measurement means, any disturbance will not be generated to fluid；
2. electric sensor and ultrasonic Doppler sensor combinations formula, which measure, can get fluid flow process more fully
Description；
3. the measurement of the structure flow velocity of fluid is realized by signal processing technology and conjoint analysis method, it is simple and easy；
4. measurement is convenient, speed is fast, at low cost.
Detailed description of the invention
The following drawings describes the embodiment selected by the present invention then, is exemplary diagram and non exhaustive or restricted, in which:
Ultrasonic Doppler sensor structure schematic diagram in measurement method Fig. 1 of the invention；
Conductance ring sensor structure schematic diagram in measurement method Fig. 2 of the invention；
Slug flow cellular construction schematic diagram in Fig. 3 measurement method of the present invention；
Empirical mode decomposition flow chart in measurement method Fig. 4 of the invention；
Measurement method Fig. 5 of the invention is hit by a bullet the calculating step of shape flow structure flow velocity.
Specific embodiment
Below with reference to the instruction sheet embodiment that the present invention will be described in detail.
Fig. 1 is the structural schematic diagram of continuous wave ultrasound doppler sensor in measurement method of the invention.The invention patent
Ultrasonic Doppler probe used uses the twin crystal ultrasonic transducer of transceiver, and internal includes a transmitting piezoelectric ceramic crystalline substance
A piece 3a and reception piezoelectric ceramic wafer 3b, is respectively attached on acoustic-electric coupling material 3c and 3d.Acoustic-electric coupling material is direct
It is contacted with fluid, and with angle theta between horizontal pipe 10Installation protects the direction of flow 0 of ultrasonic beam access and two phase flow 2
Hold angle theta.It joined sound insulating material 4 between acoustic-electric the coupling material 3c and 3d and generated between sound wave with preventing from emitting and receive
Interference.The twin crystal ultrasonic transducer is installed on horizontal pipe bottom.Transmitting piezoelectric ceramic chip 3a emits ultrasonic wave, sound wave
It propagates in fluid 2, is received after receiving discrete phase reflection and scattering in measurement space 5 by reception piezoelectric ceramic wafer 3b.It connects
The flow rate information of fluid in the frequency difference reflection measurement space 5 to quiet down between wave and transmitting sound wave.
Fig. 2 is the structural schematic diagram of conductance ring sensor in measurement method of the invention.Electricity used in the invention patent passes
Sensor is embedded in inner wall of the pipe 0 by four circular metal electrodes (1,2,3,4) and is formed, and wherein electrode 1 and electrode 4 are excitation electricity
Extremely right, electrode 2 and electrode 3 are measuring electrode pair.By injecting constant square-wave excitation current into electrode 1 and connecing electrode 4
Ground can form stable electricity sensitivity field among electrode 1 and 4.When fluid flows through sensitivity field, medium contains rate and changes in distribution
When, the potential difference between electrode 2 and electrode 3 changes, and can realize measurement of the fluid containing rate by measuring the potential difference.
Fig. 3 is slug flow cellular construction schematic diagram in measurement method of the invention.The Gas-Liquid Slug Flow cellular construction packet
Gentle bullet area 3, the area Kuo Yedan 2, the turbulence intensity of fluid and the height in the area velocity ratio Qi Dan 3 in the area Qie Yedan 2.Due to the area Ye Dan
The liquid to fall off from previous liquid bullet is constantly picked up on head, in the front end of liquid bullet when the liquid of high speed is merged with the liquid of low speed
The vortex of high speed is formed, for a large amount of discrete bubble distributions in liquid phase, this part is mixed zone 1.In the tail portion liquid of liquid bullet
Since gravity constantly returns liquid film area 4, liquid undergoes faster moderating process in this stage.In the front end of gas bullet, gas
The fluctuation of liquid interface is stronger, and drop is caused to carry secretly, and over time, fluid flowing is gradually steady, and approximate wave flow is slow
Slow flow.It is T at the beginning of the area slug flow cellular construction Zhong Yedan 21, the stop timing of mixed zone 1 is T2, the area Qi Dan 3
At the beginning of be T3And the stop timing (at the beginning of next area Ye Dan) in the area Qi Dan 3 is T4.The slug flow unit knot
The spread speed of liquid bullet is V in structureT, the average speed in the area Ye Dan 2 is VS, the mean flow rate in liquid film area 4 is Vf。
Fig. 4 is empirical mode decomposition flow chart in measurement method of the invention.Empirical mode decomposition is a kind of adaptive
The fluctuation of different scale present in signal x (t) is separated step by step by the process of screening, generates a system by Time-Frequency Analysis Method
The intrinsic mode functions (IMF) with different scale are arranged, until remaining value sequence rn(t) stop decomposing for monotonic function.It is wherein every
A IMF needs to meet two primary conditions: 1) quantity (including maximum point and minimum point) and zero crossing of signal extreme point
Quantity it is equal, or at most difference 1；2) signal is put at any time, the coenvelope line and local pole that local maximum determines
The lower envelope line mean value of small value point determination is zero, and signal is about time shaft Local Symmetric.Condition described above is to screen every time
The stop condition of journey.
Fig. 5 is the calculating flow chart of steps that present invention ultrasound obtains slug flow structure flow velocity with electricity combination sensor.Under
By taking air-water two phase flow as an example, electricity of the invention, ultrasound data conjoint analysis method obtain the calculating of slug flow structure flow velocity in face
Steps are as follows:
Step 1: acquiring the moisture content signal H (t) of electric sensor, the Doppler frequency shift of t ∈ (0, T) and ultrasonic sensor
Signal fd(t), (0, T) t ∈, wherein T is the sampling time；
Step 2: region division is carried out according to fluid of the moisture content signal to Gas-Liquid Slug Flow.
1) the moisture content mean value in the sampling time is calculatedBy thHAs threshold value containing rate to fluid into
Region division of row: if some time inscribes moisture content greater than thH, then this when the area containing Shuai Weiyedan inscribed flow through electric sensor
When moisture content, otherwise this when the area containing Shuai Weiqidan inscribed moisture content when flowing through electric sensor, i.e.,
Wherein Hnl, HngThe respectively gentle moisture content sequence for playing area in the area Ye Dan；
2) H is utilizednl、HngCalculate separately the area Ye Dan moisture content mean valueThe gentle moisture content mean value for playing area WithWherein Tl, TgRespectively in gentle bullet area, sampling time Nei Yedan area
The time of experience.It willWithSecond zone division is carried out to fluid as threshold value containing rate: if certain moment moisture content is less thanThen the moment is the area Qi Dan by electric sensor, if certain moment moisture content is greater thanAnd it is less thanThen the moment is
Mixing is otherwise the area Ye Dan by electric sensor, i.e., by electric sensor
Thus T at the beginning of the area Ye Dan can be obtained respectively1, the stop timing T of mixed zone2, T at the beginning of the area Qi Dan3
And stop timing (at the beginning of next area the Ye Dan) T in the area Qi Dan4；
Step 3: the method based on empirical mode decomposition decomposes doppler shifted signal, and extracts the knot of slug flow
Structure flow velocity.
1) to doppler shifted signal fd(t), t ∈ (0, T) is denoised.Under normal circumstances, include in doppler shifted signal
The ingredient of high-frequency noise, seriously affects analysis precision, it is therefore desirable to be denoised.First with the method for empirical mode decomposition,
By ultrasonic Doppler frequency shift signal fd(t), t ∈ (0, T) is decomposed into several intrinsic mode function IMF step by stepj(t), j=1,
2 ..., n and trend function rn(t) sum:
Wherein n is intrinsic mode function number.It is worth noting that, the essence of empirical mode decomposition is screening process, sieve
The termination condition of choosing, i.e., each IMF need to meet two primary conditions and are difficult to meet, and generally require and restrain quasi- group according to Cauchy,
Screening is terminated by the standard deviation SD limited between adjacent decomposition result, it may be assumed that
Wherein, h1,k-1, h1,kIt is that continuous two decomposition result sequences, SD generally take within the scope of 0.2-0.3 in screening process
Value, and its selection will affect the number of decomposited intrinsic mode function.Each intrinsic mode is calculated using cross-correlation method
The related coefficient of function and former doppler shifted signal, related coefficient is bigger, then shows that the intrinsic mode function can more embody letter
Number most significant feature.Therefore correlation coefficient threshold th is selected according to practical high-frequency noise situationcc, m grades of high frequencies are intrinsic before selecting
Mode function component is judged: if the related coefficient of preceding m grades of high frequency intrinsic mode function component and former doppler shifted signal
Less than thcc, then it is chosen to remove, otherwise retains.Under normal circumstances, high-frequency noise is next because frequency highest is decomposited at first, and with
The related coefficient of former doppler shifted signal is smaller, therefore the general value of m is 3-4, thccGeneral value is 0.2-0.3.Then will
It is greater than or equal to th with the related coefficient of former doppler shifted signal in m grades firstccIntrinsic mode function, it is remaining n-m grades this
Levy mode function and trend function rn(t) it sums up, is reassembled into new signal f to be processedd'(t),t∈(0,T)；
2) by new signal f to be processedd' (t), the secondary empirical mode decomposition of t ∈ (0, T) progress, then signal can indicate
For several intrinsic mode function IMFi(t), i=1,2 ..., N and trend function rN(t) sum:
Intrinsic mode function number when wherein N is second decomposition.In each IMFi(t) include in be signal from high to low
Different frequency segment components, m- scale feature ingredient when what each IMF was represented is different in original signal.Due to Empirical Mode
State decomposition method can be described as principal component analytical method again, it is generally the case that the prime intrinsic mode function that second decomposition obtains point
Amount has often concentrated most significant, most important information in signal.Therefore it selects to determine preceding 4 grades of intrinsic mode function IMFj(t),j
=1,2,3,4 are used as principal component；
3) time frequency analysis is carried out to principal component using the method for Short Time Fourier Transform, is believed in conjunction in step 2 by moisture content
Number to the division result of fluid, the structure flow velocity for the fluid that principal component reflects respectively is determined.By electricity, the connection of ultrasound information
Analysis is closed, determines first order intrinsic mode function IMF1(t) it is most radio-frequency component, appears in the head in the area Ye Dan, reflection plays shape
The spread speed of liquid bullet in stream；Second level intrinsic mode function IMF2(t) basic covering liquid bullet area and first order eigen mode are covered
State function IMF1(t) reflect the mean flow rate in the area Ye Dan together；The third level and fourth stage intrinsic mode function IMF3(t)&IMF4
(t) liquid film area is appeared in, it is related to drop entraimnent, reflect liquid film area inner fluid speed；
4) when carrying out Fast Fourier Transform (FFT) to first order intrinsic mode function component and calculate liquid bullet portion (mixed zone)
Between Doppler's average frequency shift in range:To the first order and second level intrinsic mode function point
The adduction of amount carries out Fast Fourier Transform (FFT) and calculates Doppler's average frequency shift in the area Ye Dan time rangeThe adduction of the third level and fourth stage intrinsic mode function component is carried out in quick Fu
Leaf transformation simultaneously calculates Doppler's average frequency shift in liquid film time rangeWherein fd1,
fd2, fd3Respectively IMF1(t), IMF1(t)+IMF2(t), IMF3(t)+IMF4(t) respective frequencies, i.e. ultrasound under different scale
Doppler frequency shift, Sd1(fd1), Sd2(fd2), Sd3(fd3) it is respectively its corresponding energy spectral intensity, T1, T2, T3, T4By step 2
It obtains.
5) according to the basic principle of Doppler effect, the structure flow velocity of slug flow: the wherein spread speed of liquid bullet is calculated are as follows:The average speed (while being total apparent velocity of slug flow) of liquid bullet are as follows:Liquid film area
Mean flow rate are as follows:Wherein f0For the driving frequency of ultrasonic reflections probe, θ is ultrasonic wave acoustic beam side
To the angle with horizontal direction, c is the velocity of sound in fluid.
Claims (1)
1. a kind of Gas-Liquid Slug Flow structure flow velocity acoustic-electric bimodal measurement method, using twin crystal ultrasonic transducer and electric sensor
It realizes, twin crystal ultrasonic transducer is for obtaining two phase flow ultrasonic Doppler frequency shift signal, and electric sensor is for obtaining moisture content
Signal, the twin crystal ultrasonic transducer use the same side structure of transceiver, are installed in horizontal test duct bottom and guarantee
The angle of ultrasonic wave acoustic beam direction and flow direction is θ；The electric sensor is embedded in test by four circular metal electrodes
Inner wall of the pipe composition is installed on simultaneously in test pipeline with ultrasonic transducer, and measurement method comprises the following steps:
1) the moisture content signal H (t), the doppler shifted signal f of t ∈ (0, T) and ultrasonic sensor of electric sensor are acquiredd
(t), (0, T) t ∈, wherein T is the sampling time；
2) the moisture content mean value in the sampling time is calculatedBy thHArea is carried out to fluid as threshold value containing rate
Domain divides: if some time inscribes moisture content greater than thH, then this when the area containing Shuai Weiyedan inscribed it is aqueous when flowing through electric sensor
Rate, otherwise this when the area containing Shuai Weiqidan inscribed moisture content when flowing through electric sensor, i.e.,Wherein Hnl, HngThe respectively gentle moisture content sequence for playing area in the area Ye Dan；
3) H is utilizednl、HngCalculate separately the area Ye Dan moisture content mean valueThe gentle moisture content mean value for playing area WithWherein Tl, TgRespectively in gentle bullet area, sampling time Nei Yedan area
The time of experience；It willWithSecond zone division is carried out to fluid as threshold value containing rate: if certain moment moisture content is less thanThen the moment is the area Qi Dan by electric sensor, if certain moment moisture content is less thanAnd it is greater thanThen the moment is
Mixed zone is otherwise the area Ye Dan by electric sensor, i.e., by electric sensor
Thus T at the beginning of the area Ye Dan can be obtained respectively1, the stop timing T of mixed zone2, T at the beginning of the area Qi Dan3And
The stop timing in the area Qi Dan, i.e., T at the beginning of next area Ye Dan4；
4) empirical mode decomposition is utilized, high frequency denoising is carried out to ultrasonic Doppler frequency shift signal: being based on empirical mode decomposition
Method, by ultrasonic Doppler frequency shift signal fd(t), t ∈ (0, T) is decomposed into several intrinsic mode function IMF step by stepj(t), j=
1,2 ..., n and trend function rn(t) sum:Wherein n is to decompose obtained intrinsic mode letter
Several numbers calculate each intrinsic mode function IMF using cross-correlation methodj(t), j=1,2 ..., n and former doppler shifted signal
Related coefficient, before removal in m grade with the related coefficient of former doppler shifted signal less than threshold value thccThe intrinsic mode letter of high frequency
Number component；The general value of m is 3-4, thccGeneral value is 0.2-0.3；It is related to former doppler shifted signal in will be m grades first
Coefficient is greater than or equal to thccIntrinsic mode function, remaining n-m grades of intrinsic mode function and trend function rn(t) it carries out
Adduction, is reassembled into new signal f ' to be processedd(t),t∈(0,T)；
5) utilize the method for empirical mode decomposition by signal f ' againd(t), t ∈ (0, T) is decomposed into several intrinsic mode functions
IMFi(t), i=1,2 ..., N and trend term function rN(t) sum, i.e.,Wherein N is to decompose
The intrinsic mode function number arrived；Choose preceding 4 grades of intrinsic mode function IMFi(t), i=1,2,3,4 is as principal component；
6) Short Time Fourier Transform is carried out to principal component and obtains its time-frequency spectrum, by being analyzed with electricity moisture content combined signal,
Determine the structure flow velocity for the fluid that principal component reflects respectively: first order intrinsic mode function IMF1It (t) is most radio-frequency component, instead
Reflect the spread speed of liquid bullet in slug flow；Second level intrinsic mode function IMF2(t) covering liquid bullet area and the intrinsic mode of the first order
Function IMF1(t) reflect the mean flow rate in the area Ye Dan together；The third level and fourth stage intrinsic mode function IMF3(t) and IMF4(t)
The area Ye Dan is appeared in, it is related to drop entraimnent, reflect the area Ye Dan inner fluid speed；
7) Fast Fourier Transform (FFT) is carried out to first order intrinsic mode function component and calculates liquid bullet portion i.e. mixed zone time model
Enclose interior Doppler's average frequency shift:To the first order and second level intrinsic mode function component
Adduction carries out Fast Fourier Transform (FFT) and calculates Doppler's average frequency shift in the area Ye Dan time rangeThe adduction of the third level and fourth stage intrinsic mode function component is carried out in quick Fu
Leaf transformation simultaneously calculates Doppler's average frequency shift in liquid bullet time rangeWherein fd1,
fd2, fd3Respectively IMF1(t), IMF1(t)+IMF2(t), IMF3(t)+IMF4(t) under corresponding frequency namely different scale
Ultrasonic Doppler frequency displacement, Sd1(fd1), Sd2(fd2), Sd3(fd3) it is respectively its corresponding energy spectral intensity；
8) according to Doppler effect basic principle, the structure flow velocity of slug flow: the wherein spread speed of liquid bullet is calculated are as follows:The average speed of liquid bullet are as follows:The mean flow rate in the area Ye Dan are as follows:Wherein f0For the driving frequency of ultrasonic reflections probe, θ is ultrasonic wave acoustic beam direction and horizontal direction
Angle, c are the velocity of sound in fluid.
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