Distortion velocity field inversion method and system considering distortion factor

Abstract

The invention discloses a distortion velocity field inversion method and system considering a distortion factor, and belongs to the technical field of non-contact flow field measurement. The inversion method comprises the following steps: determining a corresponding average speed according to the flying time and the path length of each sound wave path; defining the average speed meeting a preset condition as a standard speed; determining a distortion degree factor according to a deviation absolute value of the average speed and a standard speed; redividing a basic measurement area of the section of the air inlet channel based on the distortion degree factor; and solving the average speed of the re-divided region and reconstructing an air inlet speed field. According to the invention, the pertinence, accuracy and stability of air inlet channel measurement can be obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-contact flow field measurement, and more particularly to a distortion velocity field inversion method and system considering distortion factors. BACKGROUND

[0002] The stable operation of military aircraft is closely related to the inlet. The performance of the aircraft inlet directly affects the thrust generated by the engine and whether the engine can work normally, thereby restricting the overall performance of the aircraft. The large Mach number and high maneuverability of the new generation of fighter aircraft pose a severe challenge to the compatibility of the inlet and the engine.

[0003] With the continuous improvement of the maneuverability of the aircraft, the range of Mach number, altitude, angle of attack and side slip angle is greatly expanded, and the position and layout method of the inlet on the aircraft body and the structure are becoming more and more complex. These factors make it more and more difficult to meet the compatibility of the inlet and the engine. For example, the airflow in the S-shaped inlet is subjected to an adverse pressure gradient, resulting in secondary flow and separation phenomena, causing uneven distribution of the airflow at the outlet section. Inlet distortion may occur during aircraft climbing, large yaw angle, crosswind, launching weapons and inlet non-starting conditions, affecting the normal operation of the engine and flight safety.

[0004] Therefore, modern engine design requires consideration of both its performance and the anti-distortion ability of the inlet. In recent years, the ultrasonic velocity measurement method has been rapidly popularized due to its advantages of no pressure loss, high measurement accuracy, and multi-channel configuration suitable for complex flow field structures. However, the current methods for reconstructing the velocity field mainly include the least squares method, radial basis function approximation method and function regularization method, etc. These methods are aimed at velocity fields with small distortion degree, and the division method of each space region is relatively simple. There are still some limitations in the measurement of complex and severely distorted flow fields. SUMMARY

[0005] Therefore, in order to at least partially solve the above problems, the present application provides a distortion velocity field inversion method and system considering distortion factors, aiming to improve the pertinence of the distortion flow field improvement method and the reconstruction accuracy of the velocity field.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions: A distortion velocity field inversion method considering distortion factors, first, ultrasonic transducers are arranged on the inner wall of the inlet for emitting and receiving sound wave signals; the inversion method comprises: determining the corresponding average velocity according to the flight time and path length of each sound wave path; defining the average velocity satisfying the preset condition as the standard velocity; determining the distortion degree factor according to the absolute value of the deviation of the average velocity from the standard velocity; The basic measurement area of ​​the intake duct section is redefined based on the aforementioned distortion factor; Solve for the average velocity of the redefined region and reconstruct the intake velocity field.

[0007] Furthermore, the working distance of the ultrasonic transducer is determined based on the signal range, the size of the measurement area, and the signal strength, and the total deflection angle between the transmitting end and the receiving end of the effective sound wave path is ≤45°, where the total deflection angle is the angle between the initial propagation direction of the ultrasonic wave leaving the transmitting end and the final propagation direction reaching the receiving end.

[0008] Furthermore, the average speed that meets the preset conditions is defined as the standard speed, including the minimum average speed as the standard speed.

[0009] Furthermore, a distortion degree factor is determined based on the absolute value of the deviation between the average speed and the standard speed, including level 1 when the absolute value of the deviation between the average speed and the standard speed is ≤15%, level 2 when it is >15% and ≤25%, level 3 when it is >25% and ≤35%, level 4 when it is >35% and ≤45%, level 5 when it is >45% and ≤55%, level 6 when it is >55% and ≤65%, level 7 when it is >65% and ≤75%, and level 8 when it is >75%.

[0010] Furthermore, the basic measurement area of ​​the intake duct cross-section is redefined based on the aforementioned distortion factor, including: If there are two paths with a distortion factor difference ≥ n within the base region, the current base region is split off using the path with the higher distortion factor as the boundary, ensuring that the split sub-regions satisfy the following conditions: they are not traversed by paths with a distortion factor difference ≥ n and are covered by at least two paths. If these conditions are not met, the split is canceled and the original base region is retained. Here, n is preferably 4.

[0011] Furthermore, the average velocity of the redefined region is solved and the inlet velocity field is reconstructed, including: Assume that the velocity within each grid is the same and uniform; Determine the theoretical flight time of the sound wave, and combine it with the measured flight time of the sound wave to determine the error of the sound wave flight time; The least squares method is used to minimize the sum of squared errors in the sound wave transit time, and the average velocity in each region is obtained by solving for the extreme values. The inlet planar velocity field is reconstructed using an interpolation algorithm.

[0012] Furthermore, the expression for the sound wave transit time error is:

[0013] In the formula, Let be the measured flight time of the k-th sound wave path. Let be the theoretical flight time of the k-th sound wave path. For the number of regions, For region index, This represents the reciprocal of the average speed of sound propagation in the i-th region. This represents the length of the k-th path through the i-th region.

[0014] Furthermore, the average velocity within each region is calculated, including identifying regions with severe distortion. A path weight matrix is ​​introduced, and the objective is then:

[0015] In the formula, K represents the number of paths, and k represents the path index. This represents the time error of the k-th sound wave path. Let represent the weight of the k-th path, where

[0016] To adjust the parameters and control the impact of the distorted region on the weights, This represents the proportion of the length of the k-th path within the severely distorted region.

[0017] In the formula, N represents the number of severely distorted regions. This represents the length of the k-th path through the i-th region.

[0018] Furthermore, a severely distorted region is defined as a region traversed by two or more paths with distortion factors greater than or equal to p, where p is preferably 7.

[0019] Furthermore, the average velocity within each region is:

[0020] In the formula, This represents a matrix consisting of the lengths of the regions traversed by each path. The weight matrix representing the path, This represents the propagation time matrix for each path.

[0021] On the other hand, this application also provides a distortion velocity field inversion system considering the distortion factor, which applies the distortion velocity field inversion method considering the distortion factor as described above, including: An ultrasonic sensor array, installed on the inner wall of the air intake duct, includes multiple ultrasonic transducers for transmitting and receiving ultrasonic signals along multiple different paths. The signal acquisition and processing unit is electrically connected to the ultrasonic sensor array and is used to acquire the flight time of each sound wave path and calculate the average speed of the corresponding path based on the length of each path. The distortion analysis unit, which is communicatively connected to the signal acquisition and processing unit, is configured as follows: a) Define the average speed that meets the preset conditions from the average speeds of all paths as the standard speed; b) Calculate the absolute value of the deviation between the average speed of each path and the standard speed, and determine the distortion factor corresponding to each path based on the absolute value of the deviation; The dynamic mesh generation unit is communicatively connected to the distortion analysis unit and is used to re-divide the basic measurement area of ​​the inlet cross section based on the distortion degree factor. The velocity field reconstruction unit is communicatively connected to the dynamic mesh division unit and is used to solve the average velocity of each region after re-division and reconstruct the velocity field of the air intake.

[0022] The present invention discloses a distortion velocity field inversion method and system that considers distortion factors. By re-dividing the measurement area according to the distortion degree factor, it can reduce the occurrence of high singularity and edge effects in the reconstruction matrix due to the division, improve the relevance and accuracy of the inlet measurement, and solve the problem of single division of the inlet distortion velocity field measurement area. Furthermore, by introducing a weight matrix according to the distortion degree factor, path-differentiated weighting can be achieved, which can suppress data pollution in the distortion area and significantly improve the reconstruction accuracy of complex distortion flow fields. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the transducer arrangement of the present invention; Figure 2 This is a flowchart of the distortion velocity field inversion method of the present invention, which takes into account the distortion degree factor; Figure 3 A schematic diagram showing the intake duct cross-section divided into 17 regions; Figure 4 A schematic diagram showing the intake duct cross-section divided into 19 regions; Figure 5 A schematic diagram showing the intake duct cross-section divided into 33 regions; Figure 6 An example diagram showing the re-division of the basic area of ​​the intake duct cross-section. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0027] This invention discloses a method and system for inverting distorted velocity fields that considers distortion factors, applicable to the measurement of distorted flow fields in aero-engine inlets, wind tunnels, or aircraft.

[0028] The main technical approach of this application includes: First, ultrasonic transducers arranged on the wall of the air intake duct sequentially transmit and receive signals, and process the sound wave signals to obtain the sound wave transit time. Next, the average velocity of each path is calculated based on the sound wave transit time and sound wave propagation distance. Then, distortion levels are classified according to the average velocity of each path, and different distortion degree factors are assigned to each path. Finally, the areas traversed by paths with different distortion degree factors are replanned, and the weight of the paths is adjusted using the distortion degree factor when calculating the velocity, generating a measurement area for the distorted region of the air intake flow field.

[0029] In some implementation schemes, the working distance of the ultrasonic transducer is first determined based on the required signal range of the ultrasonic transducer, the size of the measurement working area, and the transducer signal strength, and the ultrasonic transducers are then deployed accordingly. In this embodiment, four pairs of ultrasonic transducers are evenly distributed on the circular wall of the air intake duct, such as... Figure 1 As shown, transducers are numbered from 1 to 8 according to their location. Each effective acoustic path is numbered based on transducer performance and effective angle of attack, following the rule of transmitting transducer number minus receiving transducer number, for example: 1-3, 1-4, 2-4, etc. The total deflection angle between the transmitting and receiving ends of the effective acoustic path is ≤45°, where the total deflection angle is the angle between the initial propagation direction of the ultrasonic wave leaving the transmitting end and the final propagation direction reaching the receiving end.

[0030] In one specific embodiment, Figure 2 The flowchart of the inversion method includes the following steps: S1. Determine the corresponding average velocity based on the flight time and path length of each sound wave path; S2. Define the average speed that meets the preset conditions as the standard speed; S3. Determine the distortion factor based on the absolute value of the deviation between the average speed and the standard speed; S4. Based on the aforementioned distortion factor, redivide the basic measurement area of ​​the intake duct cross-section; S5. Solve for the average velocity of the redefined region and reconstruct the inlet velocity field. Preferably, a path weight matrix is ​​introduced during the solution process.

[0031] In some implementations, in S1, after sequentially transmitting and receiving ultrasonic waves, the average sound wave transit time for each path is obtained, and the average velocity of that path is calculated based on the length of each path and the average sound wave transit time.

[0032] In S2, the path with the minimum average speed is defined as the standard path that does not pass through the distortion region, and its speed is the standard speed. ; In some implementations, S3, based on the average speed of the defined standard path, determines the distortion factor of each path; that is, firstly, the absolute value of the deviation between the average speed of each path and the standard speed is calculated, and the factor is set at the absolute value not exceeding [the standard speed]. A 15% path distortion factor is 1, exceeding... 15% but not exceeding 25% of the path distortion factor is 2, exceeding 25% but not exceeding 35% of the path distortion factor is 3, exceeding... 35% but not exceeding 45% of the path distortion factor is 4, exceeding... 45% but not exceeding 55% of the path distortion factor is 5, exceeding... 55% but not exceeding 65% of the path distortion factor is 6, exceeding... 65% but less than 75% of the path distortion factor is 7, exceeding... The path distortion factor is 8 for 75%.

[0033] In some optional implementations, S4, the basic measurement area of ​​the intake duct cross-section is redefined based on the distortion factor; in this embodiment, the basic measurement area is divided into 17, 19, or 33 regions according to the circular shape of the intake duct cross-section, respectively referring to... Figures 3-5 When using it, you can freely choose according to your requirements for spatial resolution.

[0034] During re-division, if there are two paths with a distortion factor difference ≥ n within the base region, the current base region is split with the path with the higher distortion factor as the boundary, ensuring that the split sub-regions satisfy the following conditions: they are not traversed by paths with a distortion factor difference ≥ n and are covered by at least two paths. If these conditions are not met, the division is canceled and the original base region is retained.

[0035] For example, if within a certain region of the base measurement area, two paths with a distortion factor difference of 4 or more simultaneously pass through that region, it indicates that when calculating the velocity in this region, the path with the larger distortion factor and the path with the smaller distortion factor are involved in the calculation with equal weight. The path with the larger distortion factor will affect the calculation speed of this region, leading to a significant deviation between the calculated value and the true value. In this case, the region is re-divided into two independent regions based on the path with the larger distortion factor. This ensures that both regions are still traversed by paths with smaller distortion factors, but are not traversed by other paths with a distortion factor difference of 4 or more. The division result is as follows: Figure 6 It is important to note that when dividing a region, at least two different paths must pass through that region to ensure that the velocity equation has a solution; if dividing a new region results in no solution to the equation, the division should be canceled and the original region should be retained.

[0036] If, within a certain area of ​​the basic measurement area, two or more paths with a distortion factor difference of less than 4 pass through that area simultaneously, then the influence of the distortion area on that area is considered to be within an acceptable range, and calculation can begin directly.

[0037] This application redefines the measurement area based on the distortion degree factor, making it more targeted and accurate.

[0038] In some implementations, the steps in S5 for solving the average velocity of the redefined region and reconstructing the inlet velocity field include: First, assume that the speed within each region is the same and uniform. Then, assign a number to each path k and each region i. This represents the length of the k-th path through the i-th region.

[0039] According to the formula for sound wave travel time ,in Let be the time of flight of the sound wave along the k-th path. This represents the reciprocal of the average sound wave propagation speed c in the i-th region. The error is:

[0040] in To measure the time of sound wave travel, This represents the error in the time it takes for the sound wave to travel.

[0041] Furthermore, based on the division of the test area, the spatial state factor, acoustic path length, flight time, and flight time error values ​​are obtained for each area, and the error is calculated using the least squares method. To minimize the sum of squares, the average velocity within each region is obtained by using the extreme value solution method. Finally, using an appropriate interpolation algorithm, the distribution of the velocity field of the entire plane under test is reconstructed.

[0042] In a preferred embodiment, since there is no prior information about the distortion field, the region traversed by two or more paths with a distortion factor greater than or equal to 7 is considered a severely distorted region. If a path passes through a severely distorted region when calculating other regions, the velocity calculation for that region will have a significant deviation.

[0043] To differentiate the reliability of different paths, a weight matrix is ​​introduced. ,in This represents the weight of the k-th path. The extent to which a path traverses a severely distorted region can be quantified by the geometric overlap, defined as the proportion of the k-th path's length within that region.

[0044] The weights can be: ,in To adjust the parameters and control the degree of influence of the distorted region on the weights.

[0045] Furthermore, substituting the weight matrix into the calculation, the objective function becomes weighted least squares: The velocity solution is obtained as follows: .

[0046] In another embodiment, this application also provides a distortion velocity field inversion system considering the distortion factor, which applies the distortion velocity field inversion method considering the distortion factor as described above, including: An ultrasonic sensor array, installed on the inner wall of the air intake duct, includes multiple ultrasonic transducers for transmitting and receiving ultrasonic signals along multiple different paths. The signal acquisition and processing unit is electrically connected to the ultrasonic sensor array and is used to acquire the flight time of each sound wave path and calculate the average speed of the corresponding path based on the length of each path. The distortion analysis unit, which is communicatively connected to the signal acquisition and processing unit, is configured as follows: a) Define the average speed that meets the preset conditions from the average speeds of all paths as the standard speed; b) Calculate the absolute value of the deviation between the average speed of each path and the standard speed, and determine the distortion factor corresponding to each path based on the absolute value of the deviation; The dynamic mesh generation unit is communicatively connected to the distortion analysis unit and is used to re-divide the basic measurement area of ​​the inlet cross section based on the distortion degree factor. The velocity field reconstruction unit is communicatively connected to the dynamic mesh division unit and is used to solve the average velocity of each region after re-division and reconstruct the velocity field of the air intake.

[0047] The inversion method provided by this invention fills a gap in the existing technology. By re-dividing the measurement area according to the distortion degree factor, it reduces the possibility that the reconstruction matrix will have high singularity and edge effects due to the division. By introducing a weight matrix according to the distortion degree factor, it suppresses data pollution in the distorted area, improves reconstruction accuracy, and at the same time ensures the accuracy and stability of the air intake flow field adjustment. It meets the measurement requirements and accuracy of velocity field in the testing and development process of military fields such as aircraft, wind tunnels, propellers, and engines.

[0048] In one specific application, a signal processing and velocity field reconstruction module is developed based on MATLAB / Simulink. In this module, four pairs of high-frequency piezoelectric ceramic transducers are evenly distributed on the circular wall of the air intake, and the effective acoustic wave paths are numbered. Furthermore, the initialization and path configuration process is as follows:

[0049] The dynamic grading process of distortion factor is as follows:

[0050] The region repartitioning algorithm process includes:

[0051] The weighted velocity field reconstruction process includes:

[0052] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for inverting a distortion velocity field considering a distortion factor, characterized in that, The inner wall of the air intake duct is equipped with ultrasonic transducers for transmitting and receiving sound wave signals; the inversion method includes: The corresponding average velocity is determined based on the flight time and path length of each sound wave path; The average speed that meets the preset conditions is defined as the standard speed; The distortion factor is determined based on the absolute value of the deviation between the average speed and the standard speed; The basic measurement area of ​​the intake duct section is redefined based on the aforementioned distortion factor; Solve for the average velocity of the redefined region and reconstruct the intake velocity field.

2. The distortion velocity field inversion method according to claim 1, characterized in that, The working distance of the ultrasonic transducer is determined based on the signal range, the size of the measurement area, and the signal strength. The total deflection angle between the transmitting end and the receiving end of the effective sound wave path is ≤45°. The total deflection angle is the angle between the initial propagation direction of the ultrasonic wave leaving the transmitting end and the final propagation direction reaching the receiving end.

3. The distortion velocity field inversion method according to claim 1, characterized in that, The average speed that meets the preset conditions is defined as the standard speed, including the minimum average speed as the standard speed.

4. The distortion velocity field inversion method according to claim 1, characterized in that, The distortion factor is determined based on the absolute value of the deviation between the average speed and the standard speed, including: Level 1 when the absolute value of the deviation between the average speed and the standard speed is ≤15%; Level 2 when it is >15% and ≤25%; Level 3 when it is >25% and ≤35%; Level 4 when it is >35% and ≤45%; Level 5 when it is >45% and ≤55%; Level 6 when it is >55% and ≤65%; Level 7 when it is >65% and ≤75%; and Level 8 when it is >75%.

5. The distortion velocity field inversion method according to claim 1, characterized in that, The basic measurement area of ​​the inlet cross-section is redefined based on the aforementioned distortion factor, including: If there are two paths with a distortion factor difference ≥ n within the basic measurement area, the current basic area is split off using the path with the higher distortion factor as the boundary. This ensures that the split sub-regions satisfy the following conditions: they are not traversed by paths with a distortion factor difference ≥ n and are covered by at least two paths. If these conditions are not met, the split is canceled and the original basic area is retained.

6. The distortion velocity field inversion method according to claim 1, characterized in that, Solving for the average velocity of the redefined region and reconstructing the inlet velocity field includes: Determine the theoretical flight time of the sound wave, and combine it with the measured flight time of the sound wave to determine the error of the sound wave flight time; With the goal of minimizing the sum of squared errors in the sound wave transit time, the average velocity in each region is obtained by solving the problem. The inlet planar velocity field is reconstructed using an interpolation algorithm.

7. The distortion velocity field inversion method according to claim 6, characterized in that, The expression for the sound wave transit time error is: In the formula, Let be the measured flight time of the k-th sound wave path. Let be the theoretical flight time of the k-th sound wave path. For the number of regions, For region index, This represents the reciprocal of the average speed of sound propagation in the i-th region. This represents the length of the k-th path through the i-th region.

8. The distortion velocity field inversion method according to claim 6, characterized in that, To calculate the average velocity within each region, including identifying severely distorted areas, a path weight matrix is ​​introduced. The objective then becomes: In the formula, K represents the number of paths, and k represents the path index. This represents the time error of the k-th sound wave path. Let represent the weight of the k-th path, where To adjust the parameters, This represents the proportion of the length of the k-th path within the severely distorted region. In the formula, N represents the number of severely distorted regions. This represents the length of the k-th path through the i-th region.

9. The distortion velocity field inversion method according to claim 8, characterized in that, The average velocity obtained in each region is: In the formula, This represents a matrix consisting of the lengths of the regions traversed by each path. The weight matrix representing the path, This represents the propagation time matrix for each path.

10. A distortion velocity field inversion system considering distortion factors, characterized in that, The distortion velocity field inversion method considering distortion factors according to any one of claims 1-9 includes: An ultrasonic sensor array, installed on the inner wall of the air intake duct, includes multiple ultrasonic transducers for transmitting and receiving ultrasonic signals along multiple different paths. The signal acquisition and processing unit is electrically connected to the ultrasonic sensor array and is used to acquire the flight time of each sound wave path and calculate the average speed of the corresponding path based on the length of each path. The distortion analysis unit, which is communicatively connected to the signal acquisition and processing unit, is configured as follows: a) Define the average speed that meets the preset conditions from the average speeds of all paths as the standard speed; b) Calculate the absolute value of the deviation between the average speed of each path and the standard speed, and determine the distortion factor corresponding to each path based on the absolute value of the deviation; The dynamic mesh generation unit is communicatively connected to the distortion analysis unit and is used to re-divide the basic measurement area of ​​the inlet cross section based on the distortion degree factor. The velocity field reconstruction unit is communicatively connected to the dynamic mesh division unit and is used to solve the average velocity of each region after re-division and reconstruct the velocity field of the air intake.

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