CN110631958B - Gas-liquid two-phase flow parameter measurement method - Google Patents
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Abstract
The invention belongs to the technical field of flow detection, and relates to a gas-liquid two-phase flow parameter measurement method, wherein an ultrasonic measurement unit and a differential pressure measurement unit are adopted to measure parameters of a gas-liquid two-phase flow in a pipeline, and a dynamic wave storage and dynamic time delay mechanism is introduced under the measurement of a two-phase medium, so that the problem that an acquired echo signal is incomplete due to the fact that the propagation speeds of ultrasonic waves in a gas-phase medium and a liquid-phase medium are greatly different in the existing sampling mechanism is solved; then according to the collected ultrasonic echo signal, the uplink and downlink time difference delta t and the uplink time t are carried out up Down time t down The method is used for calculating, and then each parameter of the gas-liquid two-phase medium is obtained through calculation by a measuring method combining an ultrasonic measuring principle and a differential pressure measuring principle, and the method has the advantages of no radioactive pollution, reliable and stable measuring results and the like.
Description
Technical Field
The invention belongs to the technical field of flow detection, relates to ultrasonic flow measurement and differential pressure flow measurement, and in particular relates to a gas-liquid two-phase flow parameter measurement method.
Background
The gas-liquid two-phase flow is widely applied to the industrial fields of petroleum, chemical industry and the like, and the gas-liquid two-phase flow is difficult to measure compared with the single-phase flow due to the diversity and the variability of the distribution condition of the gas-liquid two-phase flow.
The traditional method for effectively measuring the gas-liquid two-phase flow mainly adopts separation type measurement, separates the gas phase from the liquid phase to form single-phase fluid, and then adopts a single-phase fluid measurement mode to respectively measure the gas phase and the liquid phase. The gamma ray measuring method has complex structure and high cost, can generate radioactive pollution and limits the wide application of the measuring method. Therefore, the development of the gas-liquid two-phase flowmeter suitable for engineering application has very important significance.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a gas-liquid two-phase flow parameter measurement method, which utilizes the combination of an ultrasonic measurement technology and a differential pressure measurement technology, and introduces a dynamic wave storage and dynamic time delay wave storage mechanism to measure the gas-liquid two-phase flow parameter.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the gas-liquid two-phase flow parameter measurement method adopts an ultrasonic measurement unit and a differential pressure measurement unit to measure parameters of gas-liquid two-phase flow in a pipeline, and introduces a dynamic wave storage and dynamic time delay mechanism under the measurement of a two-phase medium, and specifically comprises the following steps: taking the state when the two-phase medium is pure gas as the initial state of a dynamic wave storage and dynamic time delay mechanism, under the pure gas, after the ultrasonic excitation signal is sent, delaying for a period of time, starting to acquire echo signals, and storing the static ultrasonic echo signals at the time of zero flow; judging whether an ultrasonic echo signal is acquired or not under a two-phase medium, and if the ultrasonic echo signal is acquired, not starting a dynamic wave storage and dynamic time delay mechanism; if the ultrasonic echo signal is not acquired, starting a dynamic wave storage and dynamic time delay mechanism; and according to the structural parameters and the medium parameters, the acquired ultrasonic echo signals and differential pressure signals are calculated to obtain parameters of the gas-liquid two-phase flow.
Further, the gas-liquid two-phase flow parameter measurement method specifically comprises the following steps:
step 1), defining an initial time t for starting to collect ultrasonic echo signals delay ＝t delay1 ，t delay1 For an initial time for starting to collect ultrasonic echo signals under pure gas, based on the initial time t delay1 Collecting ultrasonic echo signals, and storing static ultrasonic echo signals at zero flow;
step 2), judging whether an ultrasonic echo signal is acquired or not: if yes, the acquired ultrasonic echo signals do not need to be stored, and the delay time is unchanged; otherwise, executing the step 3);
step 3), defining an initial time t for starting to collect ultrasonic echo signals delay ＝t delay0 ，t delay0 For an initial time for starting to acquire ultrasonic echo signals under pure liquid, based on the initial time t delay0 Starting to collect ultrasonic echo signals;
step 4), judging whether an ultrasonic echo signal is acquired or not: if yes, the acquired ultrasonic echo does not need to be stored, and the delay time is unchanged; otherwise, starting to collect the initial time t of the ultrasonic echo signal delay Increasing the step size by taking 20 mu s as a step size;
step 5), cycling the step 4) until an ultrasonic echo signal is acquired, storing the acquired ultrasonic echo signal, and setting a time delay t delay ；
Step 6), calculating according to the acquired ultrasonic echo signals to obtain uplink and downlink time difference delta t and uplink time t up Down time t down ；
Step 7), obtaining the instantaneous flow q through calculation 1 The mixing density rho of the two-phase fluid, the liquid volume fraction LVF, the gas volume fraction GVF and the liquid flow q in the gas-liquid two-phase flow l Flow rate q of gas g Cumulative flow rate Q of liquid phase l Cumulative flow rate of gas phase Q g 。
Further, the number of points collected in step 1) is 2 n Starting to count the time at the starting time of the ultrasonic excitation signal transmission, and starting to acquire when the set time for starting to acquire the echo signal is reached, wherein the initial time for starting to acquire the echo signal is recorded as t delay The number of the collected points is 512, and the dynamic time delay mechanism for collecting the echo signals can reduce the time for collecting the echo signals, the consumption of memory and the operation time of a cross-correlation algorithm under the condition of guaranteeing that the complete echo signals are collected.
Further, in the step 2), the judging method for judging whether the ultrasonic echo signal is collected is as follows: if the maximum value of the acquired signals is greater than 2V and the positions of 512 points corresponding to the maximum value are between 200 and 300 points, acquiring ultrasonic echo signals; otherwise, the ultrasonic echo signal is not acquired.
Further, in step 3), the initial time t delay0 The calculation formula of (2) is as follows:
in the formula (1), t delay0 Is expressed in s, L is the length of the channel, m is the propagation velocity of the ultrasonic wave in the water, and m/s is the propagation velocity of the ultrasonic wave in the water.
Further, in step 6), the calculation method of each parameter is as follows:
the uplink time t up The calculation method of (2) is as follows: performing cross-correlation operation on the ultrasonic echo signal in the forward direction and the stored static ultrasonic echo signal in the zero flow in the forward direction; taking the first L points, the maximum point and the last L points of the maximum point corresponding to the abscissa T after the cross correlation operation to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number, the frequency omega of the sinusoidal to be fitted is the excitation frequency of the ultrasonic transducer, then obtaining the abscissa i corresponding to the maximum point of the fitted curve through a three-parameter fitting curve algorithm, and then going up for time T up Can be calculated by the following formula:
t up ＝(T-L+i)÷Fs (2)
if the dynamic wave storage and dynamic time delay mechanism are started in the measuring process, the uplink time t up The calculation of (2) requires the subtraction of (t) on the basis of equation (2) delay1 -t delay )；
The calculation method of the uplink and downlink time difference delta t is as follows: performing cross-correlation operation on the ultrasonic echo signals in the forward flow direction and the ultrasonic echo signals in the backward flow direction; taking the front L ' points, the maximum points and the rear L ' points of the abscissa T ' corresponding to the maximum points after the cross correlation operation to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L ' is a natural number, the frequency omega of the sinusoidal to be fitted is the excitation frequency of the ultrasonic transducer, and then obtaining the abscissa i ' corresponding to the maximum points of the fitted curve through the three-parameter fitting curve algorithm, wherein the uplink and downlink time difference deltat can be calculated through the following formula:
Δt＝(T′-L′+i′)÷Fs (3)
in the formulas (2) - (3), fs is the sampling frequency of the signal;
the downlink time t down The calculation formula of (2) is as follows.
t down ＝t up -Δt (4)
Further, in step 7), the calculation method of each parameter is as follows:
the instantaneous flow rate q 1 The calculation formula of (a) is as follows,
in the formula (5), D is the diameter of the pipeline, and phi is the included angle between the uplink and downlink transducers and the axis of the pipeline;
the mixing density rho of the two-phase fluid is calculated by combining (6) and (7),
ρ＝ΔP×K 2 /(q 1 ) 2 (6)
in the formula (6), delta P is a differential pressure measured value, and is obtained by collecting differential pressure signals for calibration, and K is a differential pressure coefficient; in the formula (7), c is an outflow coefficient, β is a diameter ratio, ε is an expansion coefficient, and d is a orifice diameter of the throttle.
The liquid volume fraction LVF in the gas-liquid two-phase flow is calculated by the formula (8),
the gas volume fraction GVF is calculated by formula (9),
GVF＝1-LVF (9)
flow rate q of liquid l Is calculated by the method (10),
q l ＝q 1 ×LVF (10)
flow rate q of gas g Calculated by the formula (11),
q g ＝q 1 ×GVF (11)
liquid phase cumulative flow rate Q l Calculated by the formula (12),
gas phase cumulative flow rate Q g Calculated by the formula (13),
further, the ultrasonic measurement unit comprises a temperature sensor, a pressure sensor, a first ultrasonic transducer, a second ultrasonic transducer, a third ultrasonic transducer and a fourth ultrasonic transducer; the first ultrasonic transducer and the second ultrasonic transducer are positioned on the same axis and are obliquely and oppositely arranged on the pipe wall respectively, the third ultrasonic transducer and the fourth ultrasonic transducer are positioned on the same axis and are obliquely and oppositely arranged on the pipe wall respectively, and two axes of the four ultrasonic transducers are X-shaped; the temperature sensor and the pressure sensor are respectively arranged on the front pipe wall and the rear pipe wall of the installation positions of the four ultrasonic transducers.
Further, the differential pressure measuring unit comprises a differential pressure sensor and a wedge-shaped throttling device, the wedge-shaped throttling device is arranged on the inner wall of the pipeline, and two sides of the differential pressure sensor are respectively communicated with the front position and the rear position of the pipeline where the wedge-shaped throttling device is located.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects: the gas-liquid two-phase flow parameter measurement method adopts the combination of the ultrasonic measurement unit and the differential pressure measurement unit to measure the parameters of the gas-liquid two-phase flow in the pipeline, and introduces a dynamic wave storage and dynamic time delay mechanism under the measurement of the two-phase medium, thereby solving the problem that the acquired echo signals are incomplete due to the great difference of the propagation speeds of ultrasonic waves in the gas-phase medium and the liquid-phase medium in the existing sampling mechanism, and having the advantages of no radioactive pollution, reliable and stable measurement results and the like.
In addition, the ultrasonic measuring unit comprises a temperature sensor and a pressure sensor which are used for measuring real-time temperature and pressure and can be used for temperature and pressure compensation of standard flow measurement.
Drawings
FIG. 1 is a flow chart of a method for measuring parameters of a gas-liquid two-phase flow provided by the invention;
fig. 2 is a schematic structural diagram of a gas-liquid two-phase flowmeter according to the present invention.
Wherein: 1 is a flange; 2 is a pipe section; 3 is a temperature sensor; 4 is a pressure sensor; 5 is a first ultrasonic transducer; 6 is a second ultrasonic transducer; 7 is a third ultrasonic transducer; 8 is a fourth ultrasonic transducer; 9 is a wedge-shaped throttling device; 10 is a differential pressure sensor; 11 is a header control operation unit; 12 is an ultrasonic measurement unit; 13 is a differential pressure measurement cell.
Detailed Description
The invention is described in further detail below with reference to the attached drawings and examples:
examples
Referring to fig. 1, the invention provides a gas-liquid two-phase flow parameter measurement method, which adopts an ultrasonic measurement unit and a differential pressure measurement unit to measure parameters of gas-liquid two-phase flow in a pipeline, and introduces a dynamic wave storage and dynamic time delay mechanism under the measurement of a two-phase medium, specifically comprising the following steps: taking the state when the two-phase medium is pure gas as the initial state of a dynamic wave storage and dynamic time delay mechanism, under the pure gas, after the ultrasonic excitation signal is sent, delaying for a period of time, starting to acquire echo signals, and storing the static ultrasonic echo signals at the time of zero flow; judging whether an ultrasonic echo signal is acquired or not under a two-phase medium, if the ultrasonic echo signal is acquired, not starting a dynamic wave storage and dynamic time delay mechanism, and if the ultrasonic echo signal is not acquired, starting the dynamic wave storage and dynamic time delay mechanism; and according to the structural parameters and the medium parameters, the acquired ultrasonic echo signals and differential pressure signals are calculated to obtain parameters of the gas-liquid two-phase flow. The structural parameters refer to the general terms of parameters related to the structural aspect of the detection device, including parameters in differential pressure coefficients, pipeline diameter D and the like, used in the process of calculating each parameter of the gas-liquid two-phase flow; the media parameters include density parameters.
Further, the gas-liquid two-phase flow parameter measurement method specifically comprises the following steps:
step 1), defining an initial time t for starting to collect ultrasonic echo signals delay ＝t delay1 ，t delay1 For the initial time of starting to collect ultrasonic echo signals under pure gas, the initial time t is based on delay1 Collecting ultrasonic echo signals, and storing static ultrasonic echo signals at zero flow; the number of the collected points is 512, the selection of the 512 points is the optimal sampling point of the invention, the sampling point is not limited to 512 points, and other sampling points are also suitable for the invention;
step 2), judging whether an ultrasonic echo signal is acquired or not, wherein the specific judging method is as follows: if the maximum value of the acquired signals is greater than 2V and the positions of 512 points corresponding to the maximum value are between 200-300 points, judging that the acquired ultrasonic echo signals are acquired, and storing the acquired ultrasonic echo signals without changing the delay time; otherwise, judging that the ultrasonic echo signal is not acquired, and executing the step 3);
step 3), defining an initial time t for starting to collect ultrasonic echo signals delay ＝t delay0 ，t delay0 For the initial time of starting to collect ultrasonic echo signals under pure liquid, the initial time t is based on delay0 Starting to collect ultrasonic echo signals;
further toGround, t delay0 The calculation formula of (2) is as follows:
in the formula (1), t delay0 The unit of (1) is s, L is the length of a sound channel, m is the propagation speed of ultrasonic waves in water, and m/s is the unit;
step 4), judging whether an ultrasonic echo signal is acquired or not: if yes, the acquired ultrasonic echo does not need to be stored, and the delay time is unchanged; otherwise, starting to collect the initial time t of the ultrasonic echo signal delay Increasing by 20 mu s as step length, namely the initial time t for collecting ultrasonic echo signals at the current moment delay The initial time equal to the last moment when the acquisition of the ultrasonic echo signal is started is added with 20 mu s;
step 5), cycling the step 4) until the ultrasonic echo signals are collected and stored, and setting a time delay t delay ；
Step 6), calculating according to the collected ultrasonic echo signals to obtain uplink and downlink time difference delta t and uplink time t up Down time t down ；
Step 7), obtaining the instantaneous flow q through calculation 1 The mixing density rho of the two-phase fluid, the liquid volume fraction LVF, the gas volume fraction GVF and the liquid flow q in the gas-liquid two-phase flow l Flow rate q of gas g Cumulative flow rate Q of liquid phase l Cumulative flow rate of gas phase Q g 。
Further, the uplink and downlink time difference deltat and the uplink time t up Down time t down The calculation method of (2) is as follows:
step a), knowing that the frequency of the ultrasonic transducer is omega, the frequency is the frequency of a sinusoidal curve to be fitted, the length of an acquired signal is n, and the sampling frequency of the signal is Fs;
step b), two paths of signals are collected, wherein x (n) and y (n) are respectively, x (n) is an ultrasonic echo signal in a forward flow direction, the forward flow direction can be shown as a figure 2, y (n) is an ultrasonic echo signal in a reverse flow direction, and n is a signal length;
step c), zero padding is carried out in front of the signal x (N), zero padding is carried out behind the signal y (N), the length of the sequence after zero padding is N, the length of N is required to be 2r, r is a natural number, and the signals after zero padding are x '(N) and y' (N);
step d), performing Fast Fourier Transform (FFT) on x '(n) and y' (n) respectively to obtain signals x (k) and y (k);
step e) of obtaining the conjugate of x (k) as x * (k) Will x * (k) Multiplying y (k) to give a signal R xy (k)；
Step f), pair R xy (k) Performing inverse Fourier transform (IFFT) to obtain cross-correlation signal R xy (τ)；
Step g), pair R xy (tau) peak search to find the cross-correlation signal R xy The abscissa corresponding to the maximum point (τ) is denoted T;
step h), taking the cross-correlation signal R xy Maximum point (T, R) xy (T)) the ordinate of the first L points, the maximum point and the last L points constitutes the signal y,
y is the discrete sequence to be fitted;
step i), constructing a matrix M,
step j), calculating
Step k), fitting a sinusoidal expression:wherein the method comprises the steps of
Step l), let ωi+θ=0, obtain the abscissa corresponding to the maximum point of the fitted sinusoidal curve as i, then
Step m), then the uplink and downlink time difference Δt= (T-l+i)/(Fs);
step n), collecting two paths of signals, namely x (n) and y (n), wherein x (n) is an ultrasonic echo signal in the forward flow direction, y (n) is a stored static ultrasonic echo signal in the forward flow direction under zero flow, and n is the signal length;
step o), repeating step c) to step l), up time t up = (T-l+i)/(Fs); the uplink time t is set due to the dynamic wave storage and the dynamic echo starting time setting up The calculation needs to be subtracted (t) delay1 -t delay ) Wherein t is delay1 For the initial time t of starting to collect ultrasonic echo signals under pure gas delay The time delay of the time when the ultrasonic echo signal is acquired in the step 5);
step p), downstream time t down ＝t up -Δt。
Further, the calculation method of each parameter in step 7) is as follows:
(1) according to the flow calculation formulaObtaining a flow value to be measured, wherein D is the diameter of a pipeline, and phi is the included angle between an uplink transducer and a downlink transducer and the axis of the pipeline;
(2) the mixing density rho of the two-phase fluid is calculated by combining the formulas (6) and (7),
ρ＝ΔP×K 2 /(q 1 ) 2 (6)
in the formula (6), delta P is a differential pressure measured value, and is obtained by collecting differential pressure signals for calibration, and K is a differential pressure coefficient; in the formula (7), c is an outflow coefficient, beta is a diameter ratio, epsilon is an expansion coefficient, and d is a throttling element aperture;
(3) the liquid volume fraction LVF and the gas volume fraction GVF in the gas-liquid two-phase flow are respectively calculated by combining the formulas (8) and (9),
GVF＝1-LVF (9)
(4) calculating to obtain the liquid flow q in the gas-liquid two-phase flow by combining the formula (10) l ，
q l ＝q 1 ×LVF (10)
(5) Calculating the gas flow q in the gas-liquid two-phase flow by combining the formula (11) g ，
q g ＝q 1 ×GVF (11)
(6) Calculating to obtain liquid phase accumulated flow Q by combining formula (12) l ，
(7) Calculating the gas phase accumulated flow Q by combining the formula (13) g ，
Further, the density of the gas is obtained by a density calculation method in national standard GB/T11062-2014, and the density ρ of the liquid is Air flow Depending on the acquisition measurement of the liquid in situ.
The device based on the gas-liquid two-phase flow parameter measurement method has the following specific structure and working process: the device, see fig. 2, comprises a gauge outfit control arithmetic unit 11, a flange 1, a pipe section 2, a temperature sensor 3, a pressure sensor 4, a first ultrasonic transducer 5, a second ultrasonic transducer 6, a third ultrasonic transducer 7 and a fourth ultrasonic transducer 8, wherein the ultrasonic measuring unit 12 is formed by the four ultrasonic transducers, the temperature sensor 3 and the pressure sensor 4, and the differential pressure measuring unit 13 is formed by a wedge-shaped throttling device 9 and a differential pressure sensor 10.
Further, the first ultrasonic transducer 5 and the second ultrasonic transducer 6 are positioned on the same axis and are respectively and obliquely arranged on the pipe wall in an opposite mode, the third ultrasonic transducer 7 and the fourth ultrasonic transducer 8 are positioned on the same axis and are respectively and obliquely arranged on the pipe wall in an opposite mode, and two axes of the four ultrasonic transducers are in an X shape; the temperature sensor 3 and the pressure sensor 4 are respectively arranged on the front pipe wall and the rear pipe wall of the installation positions of the four ultrasonic transducers, and temperature and pressure measurement values are obtained through signal conditioning, acquisition and calculation and are used for temperature and pressure compensation of standard condition flow measurement; the ultrasonic measurement unit 12 controls four ultrasonic transducers through the gauge head control arithmetic unit 11, for a total of four modes: when the first mode is that the first ultrasonic transducer 5 transmits signals, the second ultrasonic transducer 6 receives signals; when the second mode is that the second ultrasonic transducer 6 sends a signal, the first ultrasonic transducer 5 receives the signal; the third mode is that the third ultrasonic transducer 7 sends signals, and the fourth ultrasonic transducer 8 receives signals; mode four is the fourth ultrasonic transducer 8 transmitting signals and the third ultrasonic transducer 7 receiving signals.
Further, the differential pressure measuring unit 13 includes a throttling device and a differential pressure sensor 10, the throttling device is a wedge-shaped throttling device 9, the throttling device in the invention is not limited to the wedge-shaped throttling device 9, other throttling devices also accord with the working principle of the invention, preferably, the wedge-shaped throttling device 9 is selected, the wedge-shaped throttling device 9 is arranged on the inner wall of the pipeline, two sides of the differential pressure sensor 10 are respectively communicated with the front position and the rear position of the pipeline where the wedge-shaped throttling device 9 is positioned, and the differential pressure sensor 10 is used for measuring differential pressure signals at the front end and the rear end of the throttling piece.
The gauge outfit control arithmetic unit 11 performs time-sharing acquisition on ultrasonic echo signals in four modes through one ADC acquisition moduleThe acquisition mechanism of the echo signals is to start timing at the starting moment of the transmission of the ultrasonic excitation signals, when the set time for starting to acquire the echo signals is reached, the acquisition is started, and the time for starting to acquire the echo signals is recorded as t delay The number of acquisition points is 512 points. The signal acquisition mechanism can reduce the time for acquiring the echo signals, reduce the consumption of memory and the operation time of a cross-correlation algorithm under the condition that the complete echo signals are acquired.
Further, the gauge head control operation unit 11 includes implementation of the mechanism and algorithm operation used in the working process of the ultrasonic measurement unit 12 and the differential pressure measurement unit 13, and integrates menu, communication, pulse and 4-20mA output functions.
In summary, the method for measuring the parameters of the gas-liquid two-phase flow adds a dynamic wave storage and dynamic time delay mechanism under the measurement of the two-phase medium, so that the problem that the acquired echo signals are incomplete due to the fact that the propagation speeds of the ultrasonic waves in the gas-phase medium and the liquid-phase medium are greatly different in the existing acquisition mechanism can be solved. The flowmeter based on the gas-liquid two-phase flow parameter measurement method combines ultrasonic measurement and differential pressure measurement, and is matched with the gauge head control operation unit 11 with various operation mechanisms and algorithms to form the meter with simple structure, small volume, low cost, no radioactive pollution and reliable and stable measurement, and can be used for wellhead gas production, wellhead natural gas two-phase parameter on-line monitoring and parameter measurement in other gas-liquid two-phase media.
The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention.
It will be understood that the invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (9)
1. The method is characterized in that an ultrasonic measuring unit (12) and a differential pressure measuring unit (13) are adopted to measure parameters of gas-liquid two-phase flow in a pipeline, and under the measurement of a two-phase medium, a dynamic wave storage and dynamic time delay mechanism is introduced, and the method is specifically as follows: taking the state when the two-phase medium is pure gas as the initial state of a dynamic wave storage and dynamic time delay mechanism, under the pure gas, after the ultrasonic excitation signal is sent, delaying for a period of time, starting to acquire echo signals, and storing the static ultrasonic echo signals at the time of zero flow; judging whether an ultrasonic echo signal is acquired or not under a two-phase medium, if the ultrasonic echo signal is acquired, not starting a dynamic wave storage and dynamic time delay mechanism, and if the ultrasonic echo signal is not acquired, starting the dynamic wave storage and dynamic time delay mechanism; according to the structural parameters and the medium parameters, the acquired ultrasonic echo signals and differential pressure signals are calculated to obtain parameters of gas-liquid two-phase flow;
the gas-liquid two-phase flow parameter measurement method specifically comprises the following steps:
step 1), defining delay time t for starting to collect ultrasonic echo signals delay ＝t delay1 ，t delay1 For an initial time for starting to collect ultrasonic echo signals under pure gas, based on the initial time t delay1 Collecting ultrasonic echo signals, and storing static ultrasonic echo signals at zero flow;
step 2), judging whether an ultrasonic echo signal is acquired or not: if yes, the acquired ultrasonic echo signals do not need to be stored, and the delay time is unchanged; otherwise, executing the step 3);
step 3), defining delay time t for starting to collect ultrasonic echo signals delay ＝t delay0 ，t delay0 For an initial time for starting to acquire ultrasonic echo signals under pure liquid, based on the initial time t delay0 Starting to collect ultrasonic echo signals;
step 4), judging whether the ultrasonic echo signal is acquiredNumber: if yes, the acquired ultrasonic echo does not need to be stored, and the delay time is unchanged; otherwise, starting to collect the initial time t of the ultrasonic echo signal delay Increasing the step size by taking 20 mu s as a step size;
step 5), cycling the step 4) until the ultrasonic echo signals are collected, storing the collected ultrasonic echo signals, and setting a time delay t delay ；
Step 6), calculating according to the acquired ultrasonic echo signals to obtain uplink and downlink time difference delta t and uplink time t up Down time t down ；
Step 7), obtaining the instantaneous flow q through calculation 1 The mixing density rho of the two-phase fluid, the liquid volume fraction LVF, the gas volume fraction GVF and the liquid flow q in the gas-liquid two-phase flow l Flow rate q of gas g Cumulative flow rate Q of liquid phase l Cumulative flow rate of gas phase Q g 。
2. The gas-liquid two-phase flow parameter measurement method according to claim 1, wherein the number of points collected in step 1) is 2 n And each.
3. The method for measuring parameters of gas-liquid two-phase flow according to claim 2, wherein the number of the points collected in the step 1) is 512.
4. The method for measuring parameters of gas-liquid two-phase flow according to claim 3, wherein in step 2), the method for judging whether the ultrasonic echo signal is acquired is as follows: if the maximum value of the acquired signals is greater than 2V and the positions of 512 points corresponding to the maximum value are between 200 and 300 points, acquiring ultrasonic echo signals; otherwise, the ultrasonic echo signal is not acquired.
5. The gas-liquid two-phase flow parameter measurement method according to claim 1, wherein in step 3), the initial time t delay0 The calculation formula of (2) is as follows:
in the formula (1), t delay0 Is expressed in s, L is the length of the channel, m is the propagation velocity of the ultrasonic wave in the water, and m/s is the propagation velocity of the ultrasonic wave in the water.
6. The method for measuring parameters of a gas-liquid two-phase flow according to claim 1, wherein in step 6), the calculation method of each parameter is as follows:
the uplink time t up The calculation method of (2) is as follows: performing cross-correlation operation on the ultrasonic echo signal in the forward direction and the stored static ultrasonic echo signal in the zero flow in the forward direction; taking the first L points, the maximum point and the last L points of the maximum point corresponding to the abscissa T after the cross correlation operation to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L is a natural number, the frequency omega of the sinusoidal to be fitted is the excitation frequency of the ultrasonic transducer, then obtaining the abscissa i corresponding to the maximum point of the fitted curve through a three-parameter fitting curve algorithm, and then going up for time T up Can be calculated by the following formula:
t up ＝(T-L+i)÷Fs (2)
if the dynamic wave storage and dynamic time delay mechanism are started in the measuring process, the uplink time t up The calculation of (2) requires the subtraction of (t) on the basis of equation (2) delay1 -t delay )；
The calculation method of the uplink and downlink time difference delta t is as follows: performing cross-correlation operation on the ultrasonic echo signals in the forward flow direction and the ultrasonic echo signals in the backward flow direction; taking the front L ' points, the maximum points and the rear L ' points of the abscissa T ' corresponding to the maximum points after the cross correlation operation to form an input signal in a three-parameter fitting sinusoidal algorithm, wherein L ' is a natural number, the frequency omega of the sinusoidal to be fitted is the excitation frequency of the ultrasonic transducer, and then obtaining the abscissa i ' corresponding to the maximum points of the fitted curve through the three-parameter fitting curve algorithm, wherein the uplink and downlink time difference deltat can be calculated through the following formula:
Δt＝(T'-L'+i')÷Fs (3)
in the formulas (2) - (3), fs is the sampling frequency of the signal;
the downlink time t down The calculation formula of (2) is as follows:
t down ＝t up -Δt (4)。
7. the method for measuring parameters of a gas-liquid two-phase flow according to claim 1, wherein in step 7), the calculation method of each parameter is as follows:
the instantaneous flow rate q 1 The calculation formula of (a) is as follows,
in the formula (5), D is the diameter of the pipeline, and phi is the included angle between the uplink and downlink transducers and the axis of the pipeline;
the mixing density rho of the two-phase fluid is calculated by combining (6) and (7),
ρ＝ΔP×K 2 /(q 1 ) 2 (6)
in the formula (6), delta P is a differential pressure measured value, and is obtained by collecting differential pressure signals for calibration, and K is a differential pressure coefficient; in the formula (7), c is an outflow coefficient, beta is a diameter ratio, epsilon is an expansion coefficient, and d is a throttling element aperture;
the liquid volume fraction LVF in the gas-liquid two-phase flow is calculated by the formula (8),
in formula (8), ρ Air flow Is the density of the gas in the gas-liquid two-phase flow, the rho Air flow Can be obtained according to the density calculation method in national standard GB/T11062-2014; ρ Liquid and its preparation method The density of the liquid in the gas-liquid two-phase flow can be set by sampling the actual liquid on the application site;
the gas volume fraction GVF is calculated by formula (9),
GVF＝1-LVF (9)
flow rate q of liquid l Is calculated by the method (10),
q l ＝q 1 ×LVF (10)
flow rate q of gas g Calculated by the formula (11),
q g ＝q 1 ×GVF (11)
liquid phase cumulative flow rate Q l Calculated by the formula (12),
gas phase cumulative flow rate Q g Calculated by equation (13).
8. The gas-liquid two-phase flow parameter measurement method according to any one of claims 1-7, wherein the ultrasonic measurement unit (12) comprises a temperature sensor (3), a pressure sensor (4), a first ultrasonic transducer (5), a second ultrasonic transducer (6), a third ultrasonic transducer (7) and a fourth ultrasonic transducer (8); the first ultrasonic transducer (5) and the second ultrasonic transducer (6) are positioned on the same axis and are obliquely and oppositely arranged on the pipe wall respectively, the third ultrasonic transducer (7) and the fourth ultrasonic transducer (8) are positioned on the same axis and are obliquely and oppositely arranged on the pipe wall respectively, and two axes of the four ultrasonic transducers are in an X shape; the temperature sensor (3) and the pressure sensor (4) are respectively arranged on the front pipe wall and the rear pipe wall of the installation positions of the four ultrasonic transducers.
9. The gas-liquid two-phase flow parameter measurement method according to any one of claims 1 to 7, wherein the differential pressure measurement unit (13) comprises a differential pressure sensor (10) and a wedge-shaped throttling device (9), the wedge-shaped throttling device (9) is arranged on the inner wall of a pipeline, and two sides of the differential pressure sensor (10) are respectively communicated with the front position and the rear position of the pipeline where the wedge-shaped throttling device (9) is located.
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