CN115825252B - Computer readable medium and electronic device - Google Patents

Abstract

The invention relates to a computer readable medium storing a sound propagation time length measuring and calculating program, and an electronic device, wherein the sound propagation time length measuring and calculating program comprises a sound velocity measuring and calculating module and a shortest propagation time length measuring and calculating module; the sound velocity measuring and calculating module stores a scanning surface sound velocity field model constructed by using a sound velocity field model construction method, the scanning surface sound velocity field model construction method comprises the steps of using a two-dimensional sound field to scan a container filled with uneven fluid, obtaining first sound pressure in each transmitting and receiving process, establishing an initial sound velocity field model, simulating the transmitting and receiving process to obtain second sound pressure, optimizing the second sound pressure by using a gradient optimization algorithm, obtaining a final sound velocity field model after the first sound pressure is less than a threshold value, and calculating the propagation time t _i (x, z) from a third transmitting position to an (x, z) position and the propagation time t _j (x, z) from the (x, z) to a third sound pressure measuring position by using a shortest propagation time measuring module. Using this, t _i (x, z) and t _j (x, z) can be calculated.

Description

Computer readable medium, electronic device

Technical Field

The present invention relates to the technical field of ultrasonic detection of a container containing an uneven fluid, and in particular to a computer-readable medium storing a sound propagation time measurement program and an electronic device.

Background Art

Key connection parts such as the UHV transformer outlet device rely solely on the natural cycle of thermal expansion and contraction of insulating oil, which belongs to a semi-dead oil zone state. Once discharge breakdown occurs in this area, the short-circuit current does not pass through the winding, and the discharge energy is large, making it a high-risk area, seriously affecting the safety of the UHV power grid.

At present, the monitoring methods for key connection parts such as the outlet device of UHV transformers are divided into oil chromatography detection route, core grounding current detection route, core grounding high-frequency partial discharge detection route, etc. These detection methods mainly detect the characteristics of the fault state and cannot effectively monitor the entire process of the internal state change of the transformer.

Theoretically, ultrasound can be used for non-contact detection of UHV transformer outlet devices. However, the insulating oil contained in the UHV transformer outlet device will produce thermal cycles due to thermal expansion and contraction during operation, causing changes in the acoustic properties of the insulating oil at different positions and times, thus affecting the detection accuracy. Taking single-channel ultrasonic vertical incidence scanning detection as an example, its detection time is too long, and the errors caused by the acoustic properties of the insulating oil accumulate over time, resulting in extremely low accuracy. Taking array ultrasonic scanning detection as an example, array ultrasonic waves require a synthetic sound beam, which is difficult to achieve effective focusing, and the detection resolution is low and the accuracy is poor.

Summary of the invention

The purpose of the present invention is to provide a computer-readable medium storing a sound propagation time measurement program and an electronic device for measuring the sound propagation time between any two points of a container containing an uneven fluid.

The technical solution of the present invention is:

A computer-readable medium storing a sound propagation time calculation program, wherein the sound propagation time calculation program comprises an input module, a sound speed calculation module, a shortest propagation time calculation module and an output module;

The sound velocity calculation module stores a scanning surface sound velocity field model constructed using a sound velocity field model construction method, and the sound velocity field model construction method includes the following steps:

Step S10, scanning the container containing the non-uniform fluid in a circumferential manner in a scanning plane, transmitting an ultrasonic wave at a first transmitting position r _s in each transmitting and receiving process of the circumferential scanning of the container containing the non-uniform fluid, and measuring first sound pressures u _obs (t, r _r , r _s ) at n first sound pressure measuring positions r _r at a time t after the transmission, where n≥2;

Step S11, establish a scanning surface structure simulation model of the container containing the non-uniform fluid, discretize the scanning surface structure simulation model, add the wave rule after the discrete processing, configure the sound speed of each discrete point, and obtain the scanning surface sound speed field model

Step S12: using a gradient optimization algorithm to iteratively correct the scanning surface sound velocity field model Obtain a scanning surface sound velocity field model that fits the sound velocity field in the scanning plane of step S10

The input module is used to input the third transmitting position of the m-times transmitting and receiving process in the scanning plane of the container containing the non-uniform fluid, the n third sound pressure measurement positions, and the third sound pressure measured at the third sound pressure measurement position, wherein m≥1; the third ultrasonic wave emitted at the third transmitting position is the same as the ultrasonic wave in the step S10;

The shortest propagation time measuring module is used to measure the propagation time _ti (x, z) of the third ultrasonic wave emitted from the i-th third transmitting position to the discrete point (x, z) position and the propagation time _tj (x, z) of the third ultrasonic wave from the discrete point (x, z) position to the j-th third sound pressure measurement position, wherein i is 1, 2, 3, ..., m respectively; j is 1, 2, 3, ..., n respectively;

The output module is used to output _ti (x, z) and _tj (x, z).

Preferably, the scanning surface structure simulation model includes a first discrete point for simulating air, a second discrete point for simulating the shell of the first container containing the non-uniform fluid, and a third discrete point for simulating the non-uniform fluid. The input module is also used to input the sound velocity of the first discrete point and the sound velocity of the second discrete point. The sound velocity measurement module updates the scanning surface sound velocity field model.

Preferably, assuming k≥0, in step S12, the scanning surface sound velocity field model is iteratively corrected using a gradient optimization algorithm The method comprises the following steps:

Step S120: Before the k+1th iteration, the scanning surface sound velocity field model In the simulation of all the transmitting and receiving processes of step S10, the scanning surface sound velocity field model Output the second sound pressure at the corresponding position at the time t after the emission.

set up

like Then the iteration is terminated and the scanning surface sound velocity field model is obtained like Then the k+1th iteration is performed; ξ is the maximum threshold of the second sound pressure and the first sound pressure;

Step S121: At the k+1th iteration, the gradient operator

g _k+1 =J ^T Δu _k (2) where J represents the Jacobian matrix, Δu _k is the scanning surface sound velocity field model a difference between the output second sound pressure and the first sound pressure;

Use the gradient optimization algorithm to find the search direction and search step size, and update the scanning surface sound velocity field model

Wherein, α _k+1 is the iteration step, d _k+1 is the search direction, d _k+1 =f(g _k+1 );

Let k=k+1 and continue to execute step S120.

Further preferably, in step S121, d _k+1 = -g _k+1 , and α _k+1 is the iteration step length obtained by using the line search method.

Further preferably, in the step S10, in each transmission and receiving process, the first ultrasonic wave is transmitted in the first direction at the first transmission position, and the first transmission position, the first direction and the n first sound pressure measurement positions are all set in the scanning plane; in the step S120, the scanning surface sound velocity field model The method for simulating the one-time transmission and receiving process of step S10 is: taking the relative positions of the first transmission position, n first sound pressure measurement positions and the first container containing the non-uniform fluid in the one-time transmission and receiving process of step S10 as a reference basis, determining the second transmission position and n second sound pressure measurement positions respectively according to the position of the scanning surface structure simulation model, setting the parameters of the second ultrasonic wave simulated to be transmitted at the second transmission position, the second ultrasonic wave simulating the first ultrasonic wave, and the scanning surface sound velocity field model The second sound pressure at the second sound pressure measurement position at a time t after the second ultrasonic wave is emitted is measured.

Preferably, the container containing the non-uniform fluid is a transformer outlet device, and in the step S10, n＞31.

Preferably, in the step S11, a maximum grid size Δs for discretization processing is set to discretize the scanning surface structure simulation model;

The fluctuation rule after the discrete processing is:

Where u(x,z,t) is the acoustic pressure field, (x,z) are the horizontal and vertical coordinates of the discrete points in the scanning surface, t is the time, v(x,z) is the sound velocity at the discrete point (x,z), Δt is the calculation time step, Δs is the maximum grid size, M represents 0.5 times the differential accuracy order, and C is the differential coefficient.

Further preferably, in step S11, the maximum grid size Δs is 1/8 of the minimum wavelength of the ultrasonic wave; the calculation time step Δt satisfies _vmin is the minimum sound velocity of the medium in the scanning plane.

Further preferably, the method in which the shortest propagation time measuring module measures the shortest propagation time between any two points in the scanning surface sound velocity field model is:

Assume that discrete point p is within the previous propagation depth, corresponding to position ( _xp , _zp ); point q is within the next propagation depth, corresponding to position ( _xq , _zq ), then the virtual propagation time of the two discrete points p and q is

Where v(x _p ,z _p ) is the speed of sound at the discrete point (x _p ,z _p );

If point p and point q are in the same sound propagation depth, or point p and point q are not in two adjacent sound propagation depths, or point p and point q are in two adjacent sound propagation depths, but point p is in the latter sound propagation depth and point q is in the former sound propagation depth, then let tof _pq = ∞, indicating that the sound wave cannot temporarily propagate between p and q;

If point p and point q are not within two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q, and tof _pq is updated.

Still further preferably, for point p and point q which are not within two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the Viterbi shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q.

Preferably, in step S10, an ultrasonic transmitter is used to transmit ultrasonic waves, and the ultrasonic transmitter is a linear array ultrasonic transmitter composed of m ultrasonic transmitting units. An ultrasonic receiver is used to measure the sound pressure at n first sound pressure measurement positions, and the ultrasonic receiver is a linear array ultrasonic receiver composed of n ultrasonic receiving units, where n≥m≥2.

An electronic device includes a processor and the aforementioned computer-readable medium storing a sound propagation duration measurement program.

The beneficial effects of the present invention are:

1. In the computer-readable medium storing the sound propagation time measurement program of the present invention: the sound speed measurement module of the sound propagation time measurement program stores a scanning surface sound speed field model constructed using a sound speed field model construction method, which is mainly used to determine the scanning surface sound speed field of a container containing an inhomogeneous fluid. The shortest propagation time measurement module of the sound propagation time measurement program uses the third transmission position, n third sound pressure measurement positions, and the third sound pressure measured at the third sound pressure measurement position obtained in the m transmission and reception processes, wherein m≥1; the third ultrasonic wave transmitted at the third transmission position is the same as the ultrasonic wave in the step S10; the propagation time _ti (x,z) of the third ultrasonic wave transmitted from the i-th third transmission position to the third transmission direction to the discrete point (x,z) position and the propagation time _tj (x,z) of the third ultrasonic wave transmitted from the discrete point (x,z) position to the j-th third sound pressure measurement position are calculated, wherein i is 1, 2, 3, ..., m respectively; j is 1, 2, 3, ..., n respectively; _ti (x,z) and _tj (x,z) output by the output module can be used as input of the imaging algorithm to obtain ultrasonic imaging of the container containing inhomogeneous fluid on the scanning plane.

2. In the computer-readable medium storing the sound propagation time measurement program of the present invention: the scanning surface sound velocity field model includes a first discrete point for simulating air, a second discrete point for simulating the shell of the first container containing the inhomogeneous fluid, and a third discrete point for simulating the inhomogeneous fluid. The actual third emission position and the third sound pressure measurement position are not necessarily close to the shell of the second container containing the inhomogeneous fluid. Therefore, the actual sound velocity of the air and the actual sound velocity of the shell will affect the result. Therefore, by obtaining the sound velocity of the first discrete point and the sound velocity of the second discrete point, after the sound velocity measurement module updates the final sound velocity field model, the final sound velocity field model will be closer to the sound velocity field model of the second container containing the inhomogeneous fluid, which can improve the accuracy. In the sound propagation time measurement program, the shortest propagation time measurement module is independently extracted, rather than directly using the shortest propagation time measured by the first container containing the inhomogeneous fluid, so that the influence of the actual sound velocity of the air and the actual sound velocity of the shell on the result can be considered, which can improve the accuracy.

4. In the computer-readable medium storing the sound propagation time measurement program of the present invention, when the scanning surface sound velocity field model is constructed using the sound velocity field model construction method: in the step S12, the optimization efficiency of the scanning surface sound velocity field model can be improved by using the gradient optimization algorithm.

5. In the computer-readable medium storing the sound propagation time calculation program of the present invention, when the scanning surface sound velocity field model is constructed using the sound velocity field model construction method: in the step S121, d _k+1 =-g _k+1 , α _k+1 is the iteration step length obtained by the line search method. It corresponds to the fastest gradient descent optimization algorithm, with fast convergence speed and high optimization efficiency.

6. In the computer-readable medium storing the sound propagation time measurement program of the present invention, when the scanning surface sound velocity field model is constructed using the sound velocity field model construction method: in the step S10, in each transmission and reception process, an ultrasonic wave is transmitted in the first direction at one of the first transmission positions. Compared with transmitting the ultrasonic wave from more than two first transmission positions, the sound pressure at the first sound pressure measurement position will not be superimposed, and the effect of each ultrasonic wave in the scanning plane can be distinguished. Similarly, in each transmission and reception process simulated in step S120, the ultrasonic wave is transmitted in the second direction at one of the second transmission positions. The first transmission position, the first direction and the n first sound pressure measurement positions are all set on the scanning plane, and a two-dimensional sound field set in the scanning plane can be formed.

6. In the computer-readable medium storing the sound propagation time measurement program of the present invention, when the scanning surface sound velocity field model is constructed using the sound velocity field model construction method: after the insulating oil is filled in the transformer, it is a container containing an uneven fluid. In actual use, the amount of insulating oil in the transformer is consistent, so the reproducibility is high. Since the size of the transformer outlet device is large, n>31, the ultrasonic receiving range can be effectively improved, the calculation area can be increased, and the detection efficiency can be improved; at the same time, the amount of data is increased, so that there are more reference quantities when inverting and calculating the scanning surface sound velocity field model, thereby improving the fitting degree of the scanning surface sound velocity field model.

7. In the computer-readable medium storing the sound propagation time measurement program of the present invention, when the scanning surface sound velocity field model is constructed using the sound velocity field model construction method: the medium applicable to the existing wave equation is continuous, while the ultrasonic propagation characteristics of the medium of the container containing the non-uniform fluid are inconsistent. Only after discretization processing can the sound velocity be configured for different media on this basis. Add the wave equation after discretization processing to the scanning surface structure simulation model, configure the initial sound velocity of each discrete point in the scanning surface structure simulation model, and obtain the scanning surface sound velocity field model. In this way, an initial scanning surface sound velocity field model simulating the sound propagation characteristics is constructed to facilitate optimization fitting.

8. In the computer-readable medium storing the sound propagation time calculation program of the present invention, when the scanning surface sound velocity field model is constructed using the sound velocity field model construction method: in the step S11, when the model space is discretized, 1/8 of the minimum wavelength of the ultrasonic wave is taken as the maximum grid size Δs, so that the medium on the ultrasonic wave propagation path can be finely distinguished. The calculation time step Δt satisfies v _min is the minimum sound velocity of the medium in the scanning plane. When the discrete points obtained in this way are used for finite difference forward simulation calculation, the physical dispersion phenomenon of sound waves in the propagation process can be effectively weakened while ensuring the stability of the difference format.

9. In the computer-readable medium storing the sound propagation time calculation program of the present invention, in the method in which the shortest propagation time calculation module calculates the shortest propagation time between any two points in the sound velocity field model of the scanning surface, since the grid size is smaller than the wavelength, in the same sound propagation depth in the same spatial slice, each discrete point is approximately considered to be an isotropic medium, and the sound velocity does not change. Therefore, assuming that point p is in the previous sound propagation depth, corresponding to the position (x _p , z _p ); point q is in the next sound propagation depth, corresponding to the position (x _q , z _q ), then the virtual propagation time of the two discrete points p and q is Where v(x _p ,z _p ) is the sound velocity of the discrete point (x _p ,z _p ); if point p and point q are in the same sound propagation depth, or point p and point q are not in two adjacent sound propagation depths, or point p and point q are in two adjacent sound propagation depths, but point p is in the latter sound propagation depth and point q is in the former sound propagation depth, then let tof _pq = ∞, indicating that the sound wave cannot temporarily propagate between p and q; in this way, the shortest propagation time between any two medium points at two adjacent depths can be determined. For point p and point q not in two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q, and tof _pq is updated. In this way, the shortest propagation time between any two medium points can be determined.

10. In the computer-readable medium storing the sound propagation time measurement program of the present invention, in the method in which the shortest propagation time measurement module measures the shortest propagation time between any two points in the scanning surface sound velocity field model, in the step S13, the Viterbi shortest path search algorithm is used to determine the shortest propagation path between any two points p and q on the spatial slice in the model space. The algorithm is mature and can save measurement workload.

11. In the electronic device of the present invention, when the processor executes the sound propagation time measurement program, _ti (x, z) and _tj (x, z) can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method for ultrasonic imaging of a container containing an inhomogeneous fluid.

FIG. 2 is a schematic diagram of searching the propagation path of a first ultrasonic wave in a method for ultrasonic imaging of a container containing an inhomogeneous fluid.

DETAILED DESCRIPTION

The present invention is described in the form of embodiments in conjunction with the accompanying drawings to assist those skilled in the art in understanding and implementing the present invention. Unless otherwise specified, the following embodiments and the technical terms therein should not be understood without departing from the technical knowledge background of the technical field.

The ultrasonic detector includes an ultrasonic generator, an ultrasonic transmitter and an ultrasonic receiver.

The ultrasonic generator converts the AC power from the power supply into power suitable for powering the transducer at ultrasonic frequency, and is used to send high voltage electrical pulses to the ultrasonic transducer.

Ultrasonic transducers convert energy from electrical energy to mechanical energy, or mechanical energy to electrical energy. This conversion can be accomplished through piezoelectric ceramics or magnetostrictive materials. According to their functions, they can be divided into ultrasonic transmitters, ultrasonic receivers, and ultrasonic transceivers. Ultrasonic transmitters convert high-voltage electrical pulses into ultrasonic vibrations. Ultrasonic receivers convert ultrasonic vibrations into electrical signals. Ultrasonic transceivers can transmit and receive ultrasonic waves.

Embodiment 1: A method for ultrasonic imaging of a container containing an inhomogeneous fluid, comprising the following steps:

Step S10, using a two-dimensional sound field to scan a first container containing an inhomogeneous fluid, assuming that the plane where the two-dimensional sound field is located is a scanning plane; in each transmitting and receiving process, transmitting a first ultrasonic wave in a first transmitting position in a first direction, respectively measuring the sound pressures at n first sound pressure measurement positions, where n≥2, and obtaining the first transmitting position, the first direction, the relative positions of the n first sound pressure measurement positions and the first container containing the inhomogeneous fluid corresponding to each transmitting and receiving process, and the first sound pressure corresponding to the first sound pressure measurement position;

In the field of ultrasonic testing, the two-dimensional sound field, i.e., the first emission position, the first emission direction, and the n first sound pressure measurement positions are all within the scanning surface. When using the two-dimensional sound field to scan the first container containing the non-uniform fluid, generally within the same scanning surface, the first emission position needs to be moved so that the first emission position surrounds the scanning surface to complete the scanning of the scanning surface; after completing the scanning of a scanning surface, the scanning surface is moved stepwise along the normal direction of the scanning surface to complete the slice scanning of the first container containing the non-uniform fluid.

In this embodiment, an ultrasonic simulation model of a transformer outlet device is obtained. Therefore, the first container containing an uneven fluid to be scanned in this step is a transformer outlet device that can be used as a standard for measurement, that is, a normal transformer outlet device, which is different from a faulty transformer outlet device.

Specifically, during ultrasonic testing, the third ultrasonic wave received by the ultrasonic receiving unit is an ultrasonic feedback signal reflected by the medium. Therefore, the ultrasonic receiver and the ultrasonic transmitter are arranged on the same side of the transformer outlet device, and the ultrasonic transmitter, the ultrasonic receiver and the step-by-step displacement mechanism are fixedly connected, so that the step-by-step displacement mechanism drives the ultrasonic transmitter and the ultrasonic receiver to perform step-by-step scanning on the shell of the transformer outlet device in a normal state.

The ultrasonic transmitter can be composed of one ultrasonic transmitting unit. However, in practice, in order to improve efficiency, the ultrasonic transmitter is usually composed of more than two ultrasonic transmitting units in a linear array. In this embodiment, a two-dimensional sound field is used to detect the transformer outlet device. Therefore, the ultrasonic transmitter selects a linear array ultrasonic transmitter, which is composed of more than two ultrasonic transmitting units, and the ultrasonic receiver selects a linear array ultrasonic transmitter, which is composed of n ultrasonic receiving units. When in use, the ultrasonic transmitting unit, the ultrasonic wave emitted by the ultrasonic transmitting unit, and the n ultrasonic receiving units should all be arranged on the same plane.

In the ultrasonic detectors on the market, the functions of the ultrasonic transmitting unit and the ultrasonic receiving unit are generally realized through the ultrasonic transceiver unit, which is smaller in size and easier to scan and operate. In this case, the number of ultrasonic transmitting units and ultrasonic receiving units is the same. When scanning the shell of the transformer outlet device, it is best to make the ultrasonic transmitter close to the shell surface of the transformer outlet device.

Taking the ultrasonic transceiver composed of 16 ultrasonic transceiver units arranged in a linear array as an example, when in use, at each scanning position, one of the ultrasonic transceiver units is used to transmit a first ultrasonic wave (the first ultrasonic wave is generally a pulsed ultrasonic wave), the first ultrasonic wave is reflected in the transformer outlet device, and the ultrasonic feedback signal returned to the ultrasonic receiving unit is an ultrasonic feedback signal, so that all ultrasonic receiving units are waiting to receive the ultrasonic feedback signal. After all ultrasonic receiving units have received the ultrasonic feedback signal, a transmission and reception process is completed, and then the ultrasonic transceiver unit is replaced to transmit another first ultrasonic wave, and the next transmission and reception process is performed, until all 16 ultrasonic transceiver units have completed a transmission and reception process, the scanning position is scanned; the ultrasonic transceiver is moved step by step to the next scanning position, and the new scanning position is scanned until the scanning of the scanning surface is completed around the scanning surface; after completing the scanning of one scanning surface, the scanning surface is moved step by step along the normal direction of the scanning surface to complete the slice scanning of the first container containing the non-uniform fluid.

In each transmission and reception process, the relative positions of the ultrasonic transmitter, the ultrasonic receiver and the transformer outlet device are determined, wherein the ultrasonic excitation point of the ultrasonic transmitting unit corresponds to the first transmission position, the ultrasonic direction emitted by the ultrasonic transmitting unit corresponds to the first direction, and the position of the ultrasonic receiving unit corresponds to the first sound pressure measurement position. In each transmission and reception process, it is necessary to record the relative positions of the first transmission position, the first direction, the first sound pressure measurement position and the first container containing the non-uniform fluid, as well as the emission sound pressure of the first ultrasonic wave and the first sound pressure received at each first sound pressure measurement position. The purpose of recording the relative positions of the first transmission position, the first direction, the first sound pressure measurement position and the first container containing the non-uniform fluid, as well as the emission sound pressure of the first ultrasonic wave and the first sound pressure received at each first sound pressure measurement position in each transmission and reception process is to reproduce the transmission and reception process in subsequent simulations.

When establishing a transformer outlet device simulation model in the model space of the sound propagation simulation software and performing sound propagation simulation, when the relative positions of the second emission position, the second emission direction, the n second sound pressure measurement positions and the transformer outlet device simulation model are the same as the relative positions of the first emission position, the first emission direction, the n first sound pressure measurement positions and the transformer outlet device, the second ultrasonic wave is simulated to be emitted along the second emission direction at the second emission position, and the second ultrasonic wave should simulate the first ultrasonic wave, that is, the emission sound pressure, waveform and other physical quantities of the second ultrasonic wave should be the same as the emission sound pressure, waveform and other physical quantities of the first ultrasonic wave, and the second sound pressure at the matching n second sound pressure measurement positions is measured by forward simulation. Generally, in the sound propagation simulation software, only relevant parameters need to be input to obtain the second sound pressure at the second sound pressure measurement position.

When simulating the emission of the second ultrasonic wave, if the second ultrasonic wave propagates spherically, that is, propagates diffusely in all directions in the scanning plane, it is not necessary to make the second emission direction the same as the first emission direction.

In the simulation, if the difference between the second sound pressure at the second sound pressure measurement position and the first sound pressure at the equivalent first sound pressure measurement position is within the sound pressure attenuation equivalent threshold, it is considered that the simulated propagation path from the second ultrasonic wave emitted from the second emission position in the model space to the second sound pressure measurement position is consistent with the measured propagation path from the first ultrasonic wave emitted from the first emission position in this step to the corresponding first sound pressure measurement position, and the emission and reception process from the first emission position to the first sound pressure measurement position is reproduced, and the ultrasonic propagation characteristics of the medium on the simulated propagation path are consistent with the ultrasonic propagation characteristics on the measured propagation path. In the simulation, if all the sound pressure detection points corresponding to the same second ultrasonic wave reproduce the emission and reception process from the first emission position to the first sound pressure measurement position, that is, the simulated propagation path of the second ultrasonic wave measured in the model space is consistent with the actual propagation path of the first ultrasonic wave in this step, that is, the ultrasonic sound velocity characteristics of the medium on the n simulated propagation paths of the second ultrasonic wave of the transformer outlet device simulation model in the model space are the same as the ultrasonic sound velocity characteristics of the medium on the n measured propagation paths of the first ultrasonic wave of the actual transformer outlet device. By traversing and simulating the scanning transformer outlet device simulation model, when all second transmitting positions reproduce the transmitting and receiving process of the first transmitting position in this step, it is considered that the ultrasonic sound velocity characteristics of the transformer outlet device simulation model in the model space are the same as the ultrasonic sound velocity characteristics of the measured transformer outlet device. In this way, a sound velocity field model of the transformer outlet device is obtained.

In actual operation, the relative positions of the first emission position, the first emission direction, the first sound pressure measurement position and the transformer outlet device are generally kept in an easily reproducible pattern to reduce the complexity of the simulation.

After obtaining the sound velocity field model of the first container containing the inhomogeneous fluid, the shortest path search algorithm is used to determine the shortest propagation time tof _pq between any two points p and q in the model space according to the Fermat principle, and the shortest propagation time tof _pq corresponds to the propagation path of the second ultrasonic wave. The shortest propagation time between all two points can construct an ultrasonic simulation model of the first container containing the inhomogeneous fluid.

When in use, the transformer outlet device to be tested is subjected to m transmission and reception processes. In each transmission and reception process, a third ultrasonic wave is transmitted in a third direction at a third transmission position, and the third sound pressure is measured at n third sound pressure measurement positions respectively. The transmission sound pressure and waveform of the third ultrasonic wave are the same as those of the first ultrasonic wave, and when the housing of the transformer outlet device to be tested is overlapped with the housing of the transformer outlet device in this step, the detection plane determined by the third direction and the n third sound pressure measurement positions is parallel to the scanning plane in this step. The third transmitting position, the third direction, the relative positions of n third sound pressure measurement positions and the first container containing inhomogeneous fluid, and the third sound pressure corresponding to the third sound pressure measurement position obtained through m transmission and receiving processes are input into the ultrasonic simulation model, and the ultrasonic simulation model outputs the propagation time _ti (x, z) of the third ultrasonic wave emitted from the i-th third transmitting position toward the third direction to the discrete point (x, z) position and the propagation time _tj (x, z) of the third ultrasonic wave from the discrete point (x, z) position to the j-th third sound pressure measurement position, wherein m≥1; i is 1, 2, 3, ..., m respectively; j is 1, 2, 3, ..., n respectively; and the imaging algorithm is used to calculate the pixel values of the discrete points in the detection plane to obtain the ultrasonic image of the second container containing inhomogeneous fluid in the detection plane.

When emitting the third ultrasonic wave, if the third ultrasonic wave propagates in a hemispherical manner, that is, propagates diffusely in all directions within the scanning plane, it is not necessary to make the third radiation direction the same as the first radiation direction.

In the ultrasonic detectors on the market, the ultrasonic transceiver unit is about 2 cm wide, so the distance between two adjacent ultrasonic transceiver units is about 5 cm. Combining the principle of the present invention, it can be seen that:

First, in theory, the closer the distance between adjacent first transmitting positions and the closer the distance between adjacent first sound pressure measurement positions, the better the inversion accuracy of the ultrasonic sound velocity characteristics of the sound velocity field model of the transformer outlet device and the ultrasonic sound velocity characteristics of the actual transformer outlet device. However, the coverage range of a single transmitting and receiving process is small and the scanning efficiency is low. Therefore, it is necessary to take into account both the scanning efficiency and the fitting accuracy, that is, it is necessary to properly control the distance between the two adjacent first transmitting positions and the distance between the two adjacent first sound pressure measurement positions.

Second, in theory, in a transmission and reception process, the larger the n, the more reference points are obtained for the inversion calculation, thereby improving the similarity between the ultrasonic sound velocity characteristics of the simulation model of the transformer outlet device in the model space and the ultrasonic sound velocity characteristics of the actual transformer outlet device.

Third, the n first sound pressure measurement positions do not need to be arranged regularly. However, the array setting of the n first sound pressure measurement positions combined with the step-by-step scanning is more suitable for the gridding measures of the simulation, and can also avoid missing scanning positions during scanning. Moreover, this can reduce the complexity of the model and the difficulty of operation.

Since the size of the transformer is much larger than that of the ultrasonic transmitting unit and the ultrasonic receiving unit, theoretically, the more ultrasonic transmitting units and the more ultrasonic receiving units there are, the better. The more ultrasonic receiving units there are, the wider the coverage of the first ultrasonic wave is. The more ultrasonic transmitting units there are, the fewer times of step-by-step movement are required, which can improve the transformer detection efficiency. In this embodiment, n is preferably ≥32.

At present, COMSOL software can realize computer simulation of sound wave propagation process using finite element method. In this embodiment, finite difference method is used to self-program and realize forward simulation process. When simulating the sound wave propagation process, it is necessary to establish an initial sound velocity field model of the transformer outlet device, and then continuously correct the sound velocity field model of the transformer outlet device according to the inversion process, so that the second sound pressure received in the forward simulation process approaches the first sound pressure actually collected.

Step S11, establishing a simulation model of the first container containing the non-uniform fluid in the model space of the sound propagation simulation software, discretizing the model space, using the parallel plane of the scanning surface to slice the simulation model layer by layer, adding the wave rule after the discretization processing, configuring the sound speed for each discrete point on the obtained space slice, and obtaining the initial sound speed field model of the model space;

When discretizing the model space of the sound propagation software, it is necessary to reasonably select the mesh size and the calculation time step. The way to select the mesh size and the calculation time step is:

Take 1/8 of the minimum wavelength as the maximum grid size of the model space, and the calculation time step satisfies the Courant-Friedrichs-Le wy (CFL) condition, that is:

Where v _min is the minimum sound velocity in the model space, Δt is the calculation time step, and Δs is the maximum grid size in the model space;

According to the minimum sound velocity value _vmin in the model space, the minimum wavelength is calculated, and then the maximum grid size in the model space is determined. Combined with formula (5), the range of the calculation time step can be determined.

By simulating the sound wave propagation process by computer, the received sound pressure signal, wave source and propagation medium satisfy the wave equation:

Among them, u(x,z,t) is the sound pressure field, (x,z) are the horizontal and vertical coordinates of the medium in the two-dimensional sound field, t is time, and v(x,z) is the sound speed in the medium at point (x,z). is the Laplace operator, and s(x,z,t) is the source term.

According to the finite difference method, the discrete form of the wave equation transformation is:

Among them, u(x,z,t) is the acoustic pressure field, (x,z) are the horizontal and vertical coordinates of the medium in the space slice, t is time, v(x,z) is the sound velocity of the medium at the discrete point (x,z), Δt is the calculation time step, Δs is the maximum grid size of the model space, M represents 0.5 times the differential accuracy order, and C is the differential coefficient. For example, M=1 represents the second-order differential accuracy; M=2 represents the fourth-order differential accuracy; M=3 represents the sixth-order differential accuracy; and so on.

The simulation model is cut layer by layer using a plane parallel to the scanning plane, that is, when the simulation model of the first container containing the non-uniform fluid coincides with the first container containing the non-uniform fluid in step S10, the cutting plane of this step is parallel to the scanning plane in step S10. The purpose is to make the scanning plane of the first container containing the non-uniform fluid in step S10 set in the same way as the cutting plane of the simulation model.

The wave equation after discretization is added to the model space, and the initial sound velocity of the medium at each discrete point in the model space is input to obtain the initial sound velocity field model of the model space. For the initial sound velocity of the medium in the simulation model of the transformer outlet device, the initial sound velocity of the shell is the theoretical sound velocity at normal temperature and pressure, the initial sound velocity of the insulating oil inside is the theoretical sound velocity at normal temperature and pressure without disturbance, and the medium sound velocity at the discrete points outside the transformer outlet device in the model space is the theoretical sound velocity of air at normal temperature and pressure.

Step S12, forward modeling the transmitting and receiving process of step S10 at the matching position of the simulation model; taking the second sound pressure measured at the matching position of the simulation model approaching the first sound pressure obtained in step S10 as the goal, using the gradient optimization algorithm to iteratively correct the initial sound velocity field model, so that the ultrasonic sound velocity properties of the model space fit the ultrasonic sound velocity properties of the first container containing the inhomogeneous fluid in step S10, and obtaining the final sound velocity field model of the model space;

Use the sound propagation simulation software to simulate the emission of the second ultrasonic wave at the matched second emission position along the second emission direction, and forward simulate and measure the second sound pressure at the matched n second sound pressure measurement positions. Among them, when the relative positions of the second emission position, the second emission direction, the n second sound pressure measurement positions and the transformer outlet device simulation model are consistent with the relative positions of the first emission position, the first emission direction, the n first sound pressure measurement positions and the transformer outlet device in step S10, the second emission position matches the first emission position, the second emission direction matches the first emission direction, and the second sound pressure measurement position matches the first sound pressure measurement position. The acoustic characteristics of the emission sound pressure, waveform and other acoustic characteristics of the second ultrasonic wave are consistent with the acoustic characteristics of the emission sound pressure, waveform and other acoustic characteristics of the first ultrasonic wave in step S10.

The data difference between the ultrasonic feedback signal obtained in the forward numerical simulation process and the actually collected ultrasonic feedback signal is calculated and expressed as the objective function in the sense of least squares:

Wherein, u _cal is the second sound pressure calculated by forward modeling in the sound velocity field v, and u _obs is the first sound pressure.

The discretized objective function is:

Among them, u _cal (t, r _r , r _s |ν) is the second sound pressure calculated by forward simulation in the sound velocity field v, u _obs (t, r _r , r _s ) is the first sound pressure, r _s represents the second emission position, and r _t represents the second sound pressure measurement position.

The definition of the gradient in the model is the partial derivative of the objective function with respect to the sound velocity field in the model, and the gradient operator is:

Where J represents the Jacobian matrix, Δu _k is the sound velocity field model The difference between the second sound pressure output and the first sound pressure.

Combined with the parameter information of the model space, such as the sound velocity, the second sound pressure and the first sound pressure of each discrete point, the gradient of the objective function with respect to the sound velocity field at all positions at any time in the model space is calculated.

The sound velocity field model is iteratively updated based on the gradient optimization algorithm to minimize the objective function, and the flow chart is shown in Figure 1. The specific process is:

The calculation is performed starting from the given initial sound velocity field model v _0. Since the relationship between the data and the model parameters is nonlinear, multiple iterations are required to converge to the local minimum of the objective function near the sound velocity field model.

In each iteration, the search direction and search step size are found through the gradient optimization algorithm, and the sound velocity field model is updated. Take the k+1th iteration as an example:

ν _k+1 ＝ν _k +α _k+1 d _k+1 (11)

Wherein, ν _k+1 is the sound velocity field model obtained at the k+1th iteration, α _k+1 is the iteration step size of the k+1th iteration, d _k+1 is the search direction of the k+1th iteration, and d _k+1 =f(g _k+1 ).

Different gradient descent methods are used, and the f(g) function is also different. In this embodiment, the fastest gradient descent optimization algorithm is used, so d _k+1 =-g _k+1 . In other embodiments, the conjugate gradient method, spectral conjugate gradient method, mixed conjugate gradient method, etc. can also be used.

When E(v _k+1 )＜E(v _k ) is satisfied, it means that the objective function value decreases until E(v _k+1 )≤ξ. At this time, the sound velocity field model v _k+1 is the final sound velocity field model; wherein ξ is the maximum threshold of the difference between the second sound pressure obtained by the forward numerical simulation and the first sound pressure actually collected.

Step S13, combining the discrete points and the final sound velocity field model, determining the shortest propagation time tof _pq between any two points p and q on each of the space slices in the model space, and all the shortest propagation times constitute an ultrasonic simulation model;

Based on the Fermat principle, that is, "ultrasound always propagates between two fixed points in space along the path of the shortest time", the propagation path of the sound line in the model space is approximated to the shortest path problem in computer graph theory. According to the Viterbi shortest path search algorithm, the sound propagation path and sound propagation time between any two fixed points in the model space are calculated, and the sound-time matrix of the model space is established.

Taking the 4-layer space model as an example, its sound line search is shown in Figure 2. Among them, the x-axis direction is horizontal to the right, and the z-axis direction is the depth direction.

Assume that the number of grid points at the same depth position after discretization is A, and the number of all discrete points is D, then in FIG1 , A=7.

After abstraction, there is the following discrete point matrix:

Among them, D＝(B+1)·A.

Assume that the second transmitting position is S, the second sound pressure measurement position is set to point e, and the second ultrasonic wave is emitted from point S to point e.

In order to construct the Viterbi shortest path search algorithm, it is necessary to establish an acoustic time matrix to represent the sound propagation time between any two fixed points. Since the grid size is smaller than the wavelength, the grid at the same depth position is approximately considered to be an isotropic medium, and the sound speed does not change. Therefore, all grid points are connected by paths, which are all search paths from point S to point e. Tof _pq is used to represent the propagation time between any two points p and q. The sound wave can only propagate between p and q when p and q are located in adjacent grids and are not at the same depth position. Therefore, the acoustic time matrix of the model space is established:

Among them, A represents the number of grid points at the same depth position after discretization, and D represents the number of all grid points.

When discrete point p is within the previous propagation depth, corresponding to position ( _xp , _zp ); point q is within the next propagation depth, corresponding to position ( _xq , _zq ), then the virtual propagation time of the two discrete points p and q is

Where ν(x _p ,z _p ) is the speed of sound at the discrete point (x _p ,z _p );

If point p and point q are within the same sound propagation depth, or point p and point q are not within two adjacent sound propagation depths, or point p and point q are within two adjacent sound propagation depths, but point p is within the latter sound propagation depth and point q is within the former sound propagation depth, then let tof _pq = ∞, indicating that the sound wave cannot temporarily propagate between p and q.

If point p and point q are not within two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q, and tof _pq is updated.

According to Fermat's principle, the sound propagation path is the path with the shortest sound propagation time among all possible paths. Therefore, the Viterbi shortest path search algorithm is used to calculate the shortest sound propagation time. First, starting from the sound source point S, for the A discrete points in the first layer, it is obvious that the time between S and each point in the first layer is the shortest time. The time matrix is searched to obtain the time from S to each point in the first layer tof＝tof _1a , where a＝1,2,3,…,A; then the propagation time of the A discrete points in the second layer is calculated, and for a specific point b, its sound propagation time is tof _1b ＝min(tof _1a +tof _ab ); by iterative calculation, the shortest propagation time from the sound source point S to all grid points can be obtained, and finally the sound propagation path corresponding to the shortest time can be calculated according to the backtracking principle.

Step S14, inputting the third transmitting position, the third direction, the relative positions of the n third sound pressure measurement positions and the second container containing the non-uniform fluid obtained in the m-times transmitting and receiving process into the ultrasonic simulation model, and the ultrasonic simulation model outputs the propagation time _ti (x, z) of the third ultrasonic wave emitted from the i-th third transmitting position toward the third direction to the discrete point (x, z) position and the propagation time _tj of the third ultrasonic wave from the discrete point (x, z) position to the j-th third sound pressure measurement position (x,z), wherein m≥1; i is 1, 2, 3, ..., m; j is 1, 2, 3, ..., n; assuming that the second container containing the inhomogeneous fluid coincides with the first container containing the inhomogeneous fluid, the detection plane determined by the third radiation direction and the n third sound pressure measurement positions is parallel to the scanning plane in the step S10, and the third ultrasonic wave is the same as the first ultrasonic wave in the step S10; an imaging algorithm is used to calculate the pixel values of discrete points in the detection plane to obtain an ultrasonic image of the second container containing the inhomogeneous fluid in the detection plane.

In this step, the transmitting and receiving process can be actually carried out, that is, in each transmitting and receiving process, a third ultrasonic wave is transmitted in a third transmitting position toward a third direction, and the transmitting sound pressure, waveform, etc. of the third ultrasonic wave should be the same as the transmitting sound pressure, waveform, etc. of the first ultrasonic wave, and the third sound pressure is measured at n third sound pressure measurement positions. The transmitting and receiving process can also be simulated. It can also be the third transmitting position, the third direction, the relative positions of the n third sound pressure measurement positions and the second container containing the non-uniform fluid involved in the transmitting and receiving process directly obtained without transmitting, and the third sound pressure at the third sound pressure measurement position.

In this embodiment, the propagation time _ti (x, z) of the third ultrasonic wave emitted from the i-th third emission position to the third emission direction to the discrete point (x, z) position and the propagation time tj (x, _z ) of the third ultrasonic wave from the discrete point (x, z) position to the j-th third sound pressure measurement position are obtained, wherein i is 1, 2, 3, ..., m respectively; j is 1, 2, 3, ..., n respectively; the focusing law of the first ultrasonic wave focused to any position in the detection plane in the model space is calculated by post-processing, and combined with the full focusing imaging algorithm, the coherent summation of all third ultrasonic waves of the m third emission positions and the n third sound pressure measurement positions at discrete points in the detection plane of the simulation model is measured in the model space.

Therefore, the imaging algorithm used is

Wherein, I(x,z) is the pixel value at the discrete point (x,z), h() is the Hilbert transform, m is the number of the third emission positions, n is the number of the third sound pressure measurement positions, _uij is the third sound pressure of the third ultrasonic wave emitted by the i-th third emission position to the j-th third sound pressure measurement position, _ti (x,z) represents the propagation time of the third ultrasonic wave emitted by the i-th third emission position to the discrete point (x,z) position, and _tj (x,z) represents the propagation time of the third ultrasonic wave from the discrete point (x,z) position to the j-th third sound pressure measurement position.

In formula (13), if the ultrasonic transmitter has only one ultrasonic transmitter unit, then m=1. If the ultrasonic transmitter has m ultrasonic transmitter units, when in use, at a scanning position, the ultrasonic transmitter can be kept unchanged and m transmission and reception processes can be performed by changing the ultrasonic transmitter units.

Coherent superposition does not change the actual sound pressure at the actual target point position. It is only a virtual focusing processing method that can increase the amplitude of the target point during imaging and improve the resolution.

Based on Example 1, a computer-readable medium storing a sound propagation time calculation program of the present invention can be obtained, wherein the sound propagation time calculation program includes an input module, a sound speed calculation module, a shortest propagation time calculation module and an output module;

The sound velocity calculation module stores a scanning surface sound velocity field model constructed using a sound velocity field model construction method, and the sound velocity field model construction method includes the following steps:

Step S10, scanning the container containing the non-uniform fluid in a circumferential manner in a scanning plane, transmitting an ultrasonic wave at a first transmitting position r _s in each transmitting and receiving process of the circumferential scanning of the container containing the non-uniform fluid, and measuring first sound pressures u _obs (t, r _r , r _s ) at n first sound pressure measuring positions r _r at a time t after the transmission, where n≥2;

Step S11, establish a scanning surface structure simulation model of the container containing the non-uniform fluid, discretize the scanning surface structure simulation model, add the wave rule after the discrete processing, configure the sound speed of each discrete point, and obtain the scanning surface sound speed field model

Step S12: using a gradient optimization algorithm to iteratively correct the scanning surface sound velocity field model Obtain a scanning surface sound velocity field model that fits the sound velocity field in the scanning plane of step S10

The input module is used to input the third transmission position, n third sound pressure measurement positions, and the third sound pressure measured at the third sound pressure measurement position obtained in the m transmission and reception processes within the scanning plane of the container containing the non-uniform fluid, wherein m≥1; the third ultrasonic wave is the same as the ultrasonic wave in step S10;

The shortest propagation time measuring module is used to measure the propagation time _ti (x, z) of the third ultrasonic wave emitted from the i-th third transmitting position to the discrete point (x, z) position and the propagation time _tj (x, z) of the third ultrasonic wave from the discrete point (x, z) position to the j-th third sound pressure measurement position, wherein i is 1, 2, 3, ..., m respectively; j is 1, 2, 3, ..., n respectively;

The output module is used to output _ti (x, z) and _tj (x, z).

Preferably, the scanning surface structure simulation model includes a first discrete point for simulating air, a second discrete point for simulating the shell of the first container containing the non-uniform fluid, and a third discrete point for simulating the non-uniform fluid. The input module is also used to input the sound velocity of the first discrete point and the sound velocity of the second discrete point. The sound velocity measurement module updates the scanning surface sound velocity field model.

Preferably, assuming k≥0, in step S12, the scanning surface sound velocity field model is iteratively corrected using a gradient optimization algorithm The method comprises the following steps:

Step S120: Before the k+1th iteration, the scanning surface sound velocity field model In the simulation of all the transmitting and receiving processes of step S10, the scanning surface sound velocity field model Output the second sound pressure at the corresponding position at the time t after the emission.

set up

like Then the iteration is terminated and the scanning surface sound velocity field model is obtained like Then the k+1th iteration is performed; ξ is the maximum threshold of the second sound pressure and the first sound pressure;

Step S121: At the k+1th iteration, the gradient operator

g _k+1 =J ^T Δu _k (15)

Where J represents the Jacobian matrix, Δu _k is the scanning surface sound velocity field model a difference between the output second sound pressure and the first sound pressure;

Use the gradient optimization algorithm to find the search direction and search step size, and update the scanning surface sound velocity field model

Wherein, α _k+1 is the iteration step, d _k+1 is the search direction, d _k+1 =f(g _k+1 );

Let k=k+1 and continue to execute step S120.

Further preferably, in step S121, d _k+1 = -g _k+1 , and α _k+1 is the iteration step length obtained by using the line search method.

Further preferably, in the step S10, in each transmission and receiving process, the first ultrasonic wave is transmitted in the first direction at the first transmission position, and the first transmission position, the first direction and the n first sound pressure measurement positions are all set in the scanning plane; in the step S120, the scanning surface sound velocity field model The method for simulating the one-time transmission and receiving process of step S10 is: taking the relative positions of the first transmission position, n first sound pressure measurement positions and the first container containing the non-uniform fluid in the one-time transmission and receiving process of step S10 as a reference basis, determining the second transmission position and n second sound pressure measurement positions respectively according to the position of the scanning surface structure simulation model, setting the parameters of the second ultrasonic wave simulated to be transmitted at the second transmission position, the second ultrasonic wave simulating the first ultrasonic wave, and the scanning surface sound velocity field model The second sound pressure at the second sound pressure measurement position at a time t after the second ultrasonic wave is emitted is measured.

Preferably, the container containing the non-uniform fluid is a transformer outlet device, and in the step S10, n＞31.

Preferably, in the step S11, a maximum grid size Δs for discretization processing is set to discretize the scanning surface structure simulation model;

The fluctuation rule after the discrete processing is:

Where u(x,z,t) is the acoustic pressure field, (x,z) are the horizontal and vertical coordinates of the discrete points in the scanning surface, t is the time, v(x,z) is the sound velocity at the discrete point (x,z), Δt is the calculation time step, Δs is the maximum grid size, M represents 0.5 times the differential accuracy order, and C is the differential coefficient.

Further preferably, in step S11, the maximum grid size Δs is 1/8 of the minimum wavelength of the ultrasonic wave; the calculation time step Δt satisfies _vmin is the minimum sound velocity of the medium in the scanning plane.

Further preferably, the method in which the shortest propagation time measuring module measures the shortest propagation time between any two points in the scanning surface sound velocity field model is:

Assume that discrete point p is within the previous propagation depth, corresponding to position ( _xp , _zp ); point q is within the next propagation depth, corresponding to position ( _xq , _zq ), then the virtual propagation time of the two discrete points p and q is

Where ν(x _p ,z _p ) is the speed of sound at the discrete point (x _p ,z _p );

If point p and point q are in the same sound propagation depth, or point p and point q are not in two adjacent sound propagation depths, or point p and point q are in two adjacent sound propagation depths, but point p is in the latter sound propagation depth and point q is in the former sound propagation depth, then let tof _pq = ∞, indicating that the sound wave cannot temporarily propagate between p and q;

If point p and point q are not within two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q, and tof _pq is updated.

Still further preferably, for point p and point q which are not within two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the Viterbi shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q.

Preferably, in step S10, an ultrasonic transmitter is used to transmit ultrasonic waves, and the ultrasonic transmitter is a linear array ultrasonic transmitter composed of m ultrasonic transmitting units. An ultrasonic receiver is used to measure the sound pressure at n first sound pressure measurement positions, and the ultrasonic receiver is a linear array ultrasonic receiver composed of n ultrasonic receiving units, where n≥m≥2.

An electronic device can also be obtained, including a processor and the aforementioned computer-readable medium storing the sound propagation duration measurement program.

The present invention is described in detail above with reference to the accompanying drawings and embodiments. It should be understood that it is impossible to describe all possible implementation methods in practice, and the inventive concept of the present invention is described as much as possible by way of example. Without departing from the inventive concept of the present invention and without creative work, the technical personnel in this technical field make selections and combinations of the technical features in the above embodiments, make experimental changes to the specific parameters, or use the prior art in this technical field to conventionally replace the disclosed technical means of the present invention to form specific embodiments, which should all belong to the implicit disclosure of the present invention.

Claims (8)

1. A computer-readable medium storing a sound propagation time calculation program, the sound propagation time calculation program comprising an input module, a sound speed calculation module, a shortest propagation time calculation module and an output module; the sound speed calculation module stores a scanning surface sound speed field model constructed using a sound speed field model construction method, characterized in that the sound speed field model construction method comprises the following steps: Step S10, scanning the first container containing the non-uniform fluid in a circumferential manner in a scanning plane, transmitting an ultrasonic wave at a first transmitting position r _s in each transmitting and receiving process of the circumferential scanning of the first container containing the non-uniform fluid, and measuring first sound pressures u _obs (t, r _r , r _s ) at n first sound pressure measuring positions r _r at a time t after the transmission, where n≥2; Step S11, establish a scanning surface structure simulation model of the first container containing the non-uniform fluid, discretize the scanning surface structure simulation model, add the wave rule after the discrete processing, configure the sound speed of each discrete point, and obtain the scanning surface sound speed field model ; Step S12: using a gradient optimization algorithm to iteratively correct the scanning surface sound velocity field model , obtain the scanning surface sound velocity field model that fits the sound velocity field in the scanning plane of step S10 ; The input module is used to input the third transmitting position of the m-times transmitting and receiving process in the scanning plane of the container containing the non-uniform fluid, the n third sound pressure measurement positions, and the third sound pressure measured at the third sound pressure measurement position, wherein m≥1; the third ultrasonic wave emitted at the third transmitting position is the same as the ultrasonic wave in the step S10; The shortest propagation time measuring module is used to measure the propagation time _ti (x, z) of the third ultrasonic wave emitted from the i-th third transmitting position to the discrete point (x, z) position and the propagation time _tj (x, z) of the third ultrasonic wave from the discrete point (x, z) position to the j-th third sound pressure measurement position, wherein i is 1, 2, 3, ..., m respectively; j is 1, 2, 3, ..., n respectively; The output module is used to output _ti (x, z) and _tj (x, z); In the step S11, a maximum grid size Δs for discretization processing is set to discretize the scanning surface structure simulation model; The fluctuation rule after the discretization process is: (4); Wherein, u(x,z,t) is the acoustic pressure field, (x,z) are the horizontal and vertical coordinates of the discrete points in the scanning surface, t is the time, v(x,z) is the sound velocity at the discrete point (x,z), Δt is the calculation time step, Δs is the maximum grid size, M represents 0.5 times the differential accuracy order, and C is the differential coefficient; In step S11, the maximum grid size Δs is 1/8 of the minimum wavelength of the ultrasonic wave; the calculation time step Δt satisfies , v _min is the minimum sound velocity of the medium in the scanning plane. 2. The computer-readable medium storing a sound propagation duration calculation program according to claim 1 is characterized in that the scanning surface structure simulation model includes a first discrete point for simulating air, a second discrete point for simulating the shell of the first container containing an inhomogeneous fluid, and a third discrete point for simulating the inhomogeneous fluid, and the input module is also used to input the sound velocity of the first discrete point and the sound velocity of the second discrete point, and the sound velocity calculation module updates the scanning surface sound velocity field model . 3. The computer-readable medium storing the sound propagation duration calculation program according to claim 1, characterized in that, assuming k ≥ 0, in step S12, the scanning surface sound velocity field model is iteratively corrected using a gradient optimization algorithm The method comprises the following steps: Step S120: Before the k+1th iteration, the scanning surface sound velocity field model In the simulation of all the transmitting and receiving processes of step S10, the scanning surface sound velocity field model Output the second sound pressure at the corresponding position at the time t after the emission. ; set up (1); like , the iteration is terminated and the scanning surface sound velocity field model is obtained ;like , then the k+1th iteration is performed; ξ is the maximum threshold of the second sound pressure and the first sound pressure; Step S121: At the k+1th iteration, the gradient operator g _k+1 =J ^T Δu _k (2); wherein J represents the Jacobian matrix, , _Δuk is the scanning surface sound velocity field model a difference between the output second sound pressure and the first sound pressure; Use the gradient optimization algorithm to find the search direction and search step size, and update the scanning surface sound velocity field model (3); Wherein, α _k+1 is the iteration step, d _k+1 is the search direction, d _k+1 =f(g _k+1 ); Let k=k+1 and continue to execute step S120. 4. The computer-readable medium storing the sound propagation time measurement program according to claim 3 is characterized in that in the step S10, in each transmission and reception process, the first ultrasonic wave is transmitted in the first direction at the first transmission position, and the first transmission position, the first direction and the n first sound pressure measurement positions are all set in the scanning plane; in the step S120, the sound velocity field model of the scanning plane is The method for simulating the one-time transmission and receiving process of step S10 is: taking the relative positions of the first transmission position, n first sound pressure measurement positions and the first container containing the non-uniform fluid in the one-time transmission and receiving process of step S10 as a reference basis, determining the second transmission position and n second sound pressure measurement positions respectively according to the position of the scanning surface structure simulation model, setting the parameters of the second ultrasonic wave simulated to be transmitted at the second transmission position, the second ultrasonic wave simulating the first ultrasonic wave, and the scanning surface sound velocity field model The second sound pressure at the second sound pressure measurement position at a time t after the second ultrasonic wave is emitted is measured. 5. The computer-readable medium storing the sound propagation duration calculation program according to claim 1, characterized in that the first container containing the non-uniform fluid is a transformer outlet device, and in the step S10, n＞31. 6. The computer-readable medium storing a sound propagation time calculation program according to claim 1, wherein the method by which the shortest propagation time calculation module calculates the shortest sound propagation time between any two points in the scanning surface sound velocity field model is: Assume that discrete point p is within the previous propagation depth, corresponding to position ( _xp , _zp ); point q is within the next propagation depth, corresponding to position ( _xq , _zq ), then the virtual propagation time of the two discrete points p and q is ; Where v(x _p ,z _p ) is the speed of sound at the discrete point (x _p ,z _p ); If point p and point q are in the same sound propagation depth, or point p and point q are not in two adjacent sound propagation depths, or point p and point q are in two adjacent sound propagation depths, but point p is in the latter sound propagation depth and point q is in the former sound propagation depth, then let tof _pq = ∞, indicating that the sound wave cannot propagate between p and q temporarily; If point p and point q are not within two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q, and tof _pq is updated. 7. The computer-readable medium storing a sound propagation time measurement program as described in claim 6 is characterized in that, for point p and point q which are not within two adjacent sound propagation depths, and the sound propagation depth to which point p belongs is before the sound propagation depth to which point q belongs, the Viterbi shortest path search algorithm is used to calculate the shortest sound propagation time between point p and point q. 8. An electronic device, comprising a processor, characterized in that it also includes a computer-readable medium storing a sound propagation duration measurement program as described in any one of claims 1 to 7.