Method for measuring vector angle of thrust vectoring nozzle

Abstract

This invention discloses a method for measuring the vector angle of a thrust vector nozzle, comprising the following steps: S1, acquiring a high-speed schlieren image of the thrust vector nozzle wake to obtain an original grayscale image; S2, obtaining a preprocessed image and a set of coordinate points representing the main boundary of the wake; S3, obtaining the coordinate range of a first selected region and a second selected region; S4, filtering out a first set of edge points located within the coordinate range of the first selected region and a second set of edge points located within the coordinate range of the second selected region; S5, performing linear fitting on the first set of edge points to obtain a first fitted line, and performing linear fitting on the second set of edge points to obtain a second fitted line; S6, calculating the angle bisector of the two lines to obtain the equation of the angle bisector; S7, outputting the thrust vector angle. This invention enables the direct acquisition of the nozzle wake deflection angle based on a high-speed schlieren image in the measurement of the thrust vector nozzle wake deflection angle.

Description

Technical Field

[0001] This invention relates to the field of aerodynamic flow measurement, and more specifically to a method for measuring the thrust vector nozzle vector angle. Background Technology

[0002] Thrust vectoring nozzles are core components of advanced aerospace propulsion systems. They can actively control the direction of the wake jet to deflect thrust, overcoming the limitations of traditional nozzles that only provide axial thrust and endowing aircraft with super-maneuverable flight capabilities. The thrust vector angle, as a core evaluation indicator for quantitatively describing the degree of wake deflection, not only affects the core performance of aircraft such as post-stall maneuverability and agile turning, but also plays a crucial role in improving the mission adaptability of supersonic aircraft. Therefore, achieving accurate and efficient measurement of the thrust vector angle under different operating conditions is a core prerequisite for verifying the overall performance of thrust vectoring nozzles and studying complex wake flow mechanisms. It can provide key data support for technological breakthroughs in aerospace propulsion systems and has irreplaceable engineering application value and scientific research significance in the fields of advanced aircraft development and propulsion system upgrades.

[0003] Currently, the methods for measuring the thrust vector angle are mainly divided into two categories: numerical simulation and experimental measurement.

[0004] In numerical simulation calculations of thrust vector angle, since secondary flow injection can cause complex flow scenarios such as shock wave interference and flow separation, in order to avoid the accuracy defects of direct integration of wall pressure, the momentum theorem is usually used to derive the force on the nozzle and calculate the thrust vector angle.

[0005] First, the flow field was numerically simulated by solving the Navier-Stokes equations to obtain the pressure of each micro-element at the nozzle exit section. Environmental back pressure ,density axial velocity component Lateral velocity components and the area of ​​the infinitesimal element .

[0006] Secondly, calculate the axial force component generated by the pressure difference at the outlet section: Then, calculate the axial and lateral momentum forces using the momentum theorem: The axial momentum force is the sum of the products of the mass flow rate and the axial velocity of each infinitesimal element: Lateral momentum force is the sum of the products of the mass flow rate and the lateral velocity of each infinitesimal element: The total axial force is obtained by superimposing the pressure difference and the axial momentum force. The lateral force is .

[0007] Finally, the thrust vector angle is calculated using the vector relationship of forces: The core logic of the experimental measurement of the thrust vector angle is to directly collect the force components acting on the nozzle using a force balance, and then derive the angle through vector relationships. The thrust vector nozzle is rigidly mounted on a high-precision six-component force balance, which is fixed to the experimental section and pre-calibrated. During the experiment, the axial force generated by the nozzle wake deflection... With lateral force The force is transmitted to the balance, where built-in strain gauge sensors convert the mechanical signal into an electrical signal. This electrical signal is then processed by the data acquisition system to obtain precise force component values. Based on the principle of force vector composition, the thrust vector angle is: However, existing methods for measuring the thrust vector angle have the following drawbacks: Numerical simulation methods rely on assumptions about the turbulence model and the quality of the mesh generation. For complex flow scenarios such as shock wave interference and flow separation, simplification of assumptions can easily lead to deviations between the calculated results and the actual flow field. While mesh refinement can improve accuracy, it significantly increases computational resource consumption and time costs, making it difficult to adapt to the needs of rapid iteration in engineering. Furthermore, numerical simulation cannot reproduce physical phenomena such as random disturbances and boundary layer transitions in real flow fields, and its accuracy in calculating the thrust vector angle of strongly nonlinear flows such as secondary flow injection is insufficient.

[0008] The core drawbacks of the force balance measurement method lie in its complexity and cost. This method requires high-precision assembly of the nozzle and balance, as well as multi-dimensional pre-calibration of the balance. Multiple sets of standard forces are applied to eliminate installation deviations and systematic errors, making the overall process cumbersome, time-consuming, and costly. Summary of the Invention

[0009] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for measuring the vector angle of a thrust vector nozzle, which can directly obtain the nozzle wake deflection angle based on high-speed schlieren images in the measurement of the thrust vector nozzle wake deflection angle.

[0010] To achieve the objective of this invention, the following solution is adopted: A method for measuring the thrust vectoring nozzle vector angle includes the following steps: S1. Obtain the high-speed schlieren image of the thrust vector nozzle wake to obtain the original grayscale image; S2. Perform edge preprocessing on the original grayscale image, extract the main boundary of the wake, and obtain the preprocessed image and the coordinate point set of the main boundary of the wake; S3. Perform a first rectangular selection and a second rectangular selection on the preprocessed image to select the first target edge region and the second target edge region of the wake, respectively, to obtain the coordinate range of the first selected region and the coordinate range of the second selected region. S4. Based on the coordinate range of the first framed region and the coordinate range of the second framed region, filter out the first set of edge points located within the coordinate range of the first framed region and the second set of edge points located within the coordinate range of the second framed region from the set of coordinate points of the main boundary of the wake. S5. Perform line fitting on the first edge point set to obtain a first fitted line, and perform line fitting on the second edge point set to obtain a second fitted line; S6. Based on the first fitted line and the second fitted line, calculate the angle bisector of the two lines and obtain the equation of the angle bisector; S7. Calculate the inclination angle of the angle bisector according to the angle bisector equation, use it as the thrust vector angle, and output the thrust vector angle.

[0011] Furthermore, step S2 specifically includes: The Canny operator is used to perform edge detection on the original grayscale image to obtain an edge image; Perform morphological closing operations on the edge image to fill the edge gaps; Remove noise regions with an area smaller than a preset threshold; The largest connected region in the image is extracted as the main boundary of the wake. All coordinate points of the main boundary are obtained to obtain the set of coordinate points of the main boundary of the wake. The image after the above processing is used as the preprocessed image.

[0012] Furthermore, step S3 specifically includes: Generate an image display window and load the preprocessed image; Make the first rectangular selection by dragging the mouse pointer, and save the coordinate range of the first selected area after confirmation; In the same image display window, drag the mouse pointer to make a second rectangular selection, and save the coordinate range of the second selected area after confirmation.

[0013] Furthermore, before filtering out the first set of edge points located within the coordinate range of the first selected area and the second set of edge points located within the coordinate range of the second selected area, the method further includes: converting the rectangular selection box position parameters in the coordinate range of the first selected area and the coordinate range of the second selected area into the start and end ranges of the horizontal and vertical coordinates in the global coordinate system of the image, and ensuring that the coordinate values ​​do not exceed the actual size of the image through boundary constraints.

[0014] Furthermore, in step S5, the straight line fitting adopts a first-order polynomial fitting method.

[0015] Furthermore, step S6 specifically includes: Verify whether the first fitted line and the second fitted line are parallel; If parallel, output a parallel prompt; If the lines are not parallel, find the intersection point of the two lines, and calculate the slope and equation of the angle bisector based on the coordinates of the intersection point and the slopes of the two lines to obtain the equation of the angle bisector.

[0016] Furthermore, after obtaining the angle bisector equation, a visualization output step is also included: the first fitted line, the second fitted line, and the angle bisector are superimposed and plotted on the original grayscale image, and the slope and arctangent angle of the angle bisector are output.

[0017] Furthermore, in the step of edge detection using the Canny operator, the high and low thresholds of the Canny operator are adaptively set according to the grayscale distribution of the image; the morphological closing operation uses a circular structuring element.

[0018] Further, in step S7, the step of calculating the inclination angle of the angle bisector based on the angle bisector equation as the thrust vector angle specifically includes: calculating the slope of the angle bisector in the global coordinate system of the image, calculating the arctangent angle based on the slope, and outputting the arctangent angle as the thrust vector angle.

[0019] Furthermore, in step S1, acquiring a high-speed schlieren image of the thrust vector nozzle wake includes: using a high-speed schlieren imaging system to capture the optical distortion caused by the density gradient of the nozzle wake, without the need to inject tracer particles or install contact sensors, thus achieving interference-free imaging of the flow field.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides direct and accurate measurements without requiring model assumptions. It directly captures optical distortion caused by the density gradient in the nozzle wake using high-speed schlieren images, realistically reproducing complex flow field details such as shock waves, turbulence, and flow separation. This avoids computational biases caused by turbulence model assumptions and mesh generation in numerical simulations, resulting in measurement results that more closely approximate the real flow field.

[0021] 2. This invention employs a non-contact measurement method, which does not interfere with the flow field. This invention achieves thrust vector angle measurement solely through optical imaging and image processing, eliminating the need to inject tracer particles into the flow field or install contact sensors. This avoids interference with the wake flow caused by traditional invasive measurements, preserving the original state of the flow field.

[0022] 3. This invention has low equipment requirements, significantly reducing testing costs. It does not rely on high-precision force balances or large-scale wind tunnel equipment; image acquisition can be completed with only a schlieren imaging system. The hardware layout is simple and compact, and the equipment purchase, maintenance, and site costs are significantly lower than existing experimental measurement methods.

[0023] 4. The operation process of this invention is simple and requires no complex calibration. This invention eliminates the cumbersome multi-dimensional pre-calibration and high-precision assembly process of force balances. The thrust vector angle can be quickly obtained through image acquisition, interactive rectangular selection, automated line fitting, and angle bisector calculation. The data processing is highly automated, significantly shortening the testing cycle and meeting the needs of rapid engineering iteration.

[0024] 5. This invention is highly adaptable and can handle complex wake morphologies. Through edge detection, morphological closing operations, and principal boundary filtering in edge preprocessing, this invention can effectively eliminate false edges caused by flow field noise and shock wave interference. It also has good fitting ability for irregular and asymmetric wake boundaries and has a wide range of applications. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method for measuring the thrust vector nozzle vector angle in an embodiment of the present invention; Figure 2 This is a schematic diagram of the method for measuring the thrust vector nozzle vector angle in an embodiment of the present invention; Figure 3 This is a schematic diagram of the original schlieren image acquired in an embodiment of the present invention; Figure 4 This is a schematic diagram of the first rectangular selection operation in an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the display of the selected area in the original image in an embodiment of the present invention; Figure 6 This is a schematic diagram of the upper boundary fitting result in an embodiment of the present invention; Figure 7 This is a schematic diagram of the lower boundary fitting result in an embodiment of the present invention; Figure 8 This is a schematic diagram illustrating the angle bisector calculation and visualization results in an embodiment of the present invention. Detailed Implementation

[0026] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0027] like Figure 1-8 As shown, this embodiment of the invention provides a method for measuring the thrust vector nozzle vector angle, including the following steps: S1. Obtain the high-speed schlieren image of the thrust vector nozzle wake to obtain the original grayscale image.

[0028] S2. Perform edge preprocessing on the original grayscale image, extract the main wake boundary, and obtain the preprocessed image and the set of coordinate points of the main wake boundary.

[0029] S3. Perform a first rectangular selection and a second rectangular selection on the preprocessed image to select the first target edge region and the second target edge region of the wake, respectively, to obtain the coordinate range of the first selected region and the coordinate range of the second selected region.

[0030] S4. Based on the coordinate range of the first framed area and the coordinate range of the second framed area, filter out the first edge point set located within the coordinate range of the first framed area and the second edge point set located within the coordinate range of the second framed area from the set of coordinate points of the main boundary of the wake.

[0031] S5. Perform line fitting on the first edge point set to obtain a first fitted line, and perform line fitting on the second edge point set to obtain a second fitted line.

[0032] S6. Based on the first fitted line and the second fitted line, calculate the angle bisector of the two lines to obtain the equation of the angle bisector.

[0033] S7. Calculate the inclination angle of the angle bisector according to the angle bisector equation, use it as the thrust vector angle, and output the thrust vector angle.

[0034] The method for measuring the thrust vector nozzle vector angle according to an embodiment of the present invention will be further described in detail below.

[0035] The thrust vector nozzle vector angle measurement method of this invention captures the optical characteristics of the nozzle wake through high-speed schlieren imaging, uses image recognition to locate the upper and lower boundaries of the wake and fits them into straight lines, solves the angle bisector of the two straight lines, and corresponds it to the thrust vector direction. Finally, the thrust vector angle is calculated, achieving low-cost, non-contact, and accurate measurement.

[0036] like Figure 2 As shown, the method for measuring the thrust vector nozzle vector angle in this embodiment of the invention includes: image loading and boundary preprocessing, region selection and identification, analysis of the selected coordinate range, fitting of straight lines, visualization of fitting results, and calculation and visualization of the angle bisectors of the two straight lines.

[0037] The specific process of the thrust vector nozzle vector angle measurement method according to an embodiment of the present invention is as follows: First, image loading and edge preprocessing are completed. The program reads the schlieren grayscale image file from the specified path, such as... Figure 3As shown, the Canny operator is used to perform edge detection of the image, then morphological closing operation is used to fill the edge gaps, and noise areas with too small area in the image are removed. Finally, the largest effective principal boundary in the image is extracted and all its coordinate points are obtained to complete the preprocessing of the image.

[0038] Then, an interactive dual-region mouse selection operation is performed. The program generates an image display window and loads the preprocessed image. It first prompts the user to perform a rectangular selection. The user drags the crosshair mouse pointer to select the first target edge region of the nozzle wake. After confirmation, the selection coordinates are saved. Then, a second rectangular selection is performed in the same window to accurately select the second target edge region of the wake, thus completing the selection of the two regions to be fitted edges.

[0039] like Figure 5 As shown, the program parses and verifies the coordinates of the two selection boxes, converts the position parameters of the rectangular selection box into the start and end range of the horizontal and vertical coordinates in the global coordinate system of the image, and ensures that the coordinate values ​​do not exceed the actual size of the image through boundary constraints. At the same time, a new image window is generated to confirm that the selection box position is accurate.

[0040] Based on the selected region, the program extracts the target edge points and fits the lines. From the extracted main boundary coordinates, the program selects the edge point sets that fall within the two selected regions respectively. The program then uses the first-order polynomial fitting method to fit the two edge point sets to the lines, solves for the slope and intercept of the lines corresponding to the two edges, and outputs the fitting results.

[0041] The program completes the local visualization verification of the fitted line. It crops out the image regions selected twice and displays the edge images of each region in an independent window. At the same time, it overlays the original edge point connection line and the fitted line, adds clear legends to distinguish the boundary points from the fitted line, and labels the expression of the corresponding line to intuitively verify the degree of fit between the edge and the fitted line.

[0042] Finally, the global coordinate transformation, angle bisector calculation, and comprehensive visualization output are completed. The locally fitted lines are transformed to the global coordinate system of the image. First, it is checked whether the two lines are parallel. If they are parallel, a prompt is given. If they are not parallel, the intersection point of the two lines is solved, and the slope and equation of the angle bisector of the two lines are calculated. Then, the two fitted lines and the angle bisector are superimposed and drawn on the original schlieren image. At the same time, the key data such as the slope of the angle bisector and the arctangent angle are output, completing the entire edge fitting and angle solving process.

[0043] The thrust vector nozzle vector angle measurement method of this invention constructs a schlieren imaging system adapted to the nozzle wake. It utilizes the optical distortion caused by the wake density gradient to directly capture the visual characteristics of thrust vector deflection without injecting tracer particles or installing contact sensors, thus achieving interference-free flow field imaging.

[0044] The thrust vector nozzle vector angle measurement method of this invention adopts a combination algorithm of Canny edge detection, morphological closure operation and principal boundary screening, which effectively eliminates false edges caused by flow field noise and shock wave interference, and accurately extracts the main boundary of the wake with the largest area, providing highly reliable basic data for subsequent fitting.

[0045] The thrust vector nozzle vector angle measurement method of this invention solves the intersection and inclination angle of two fitted lines, calculates the angle bisector equation, directly converts optical image features into thrust vector angle quantization data, and establishes an efficient mapping relationship between image edge-line fitting-angle bisector-vector angle.

[0046] The method for measuring the thrust vector nozzle vector angle according to embodiments of the present invention has the following advantages: 1. This invention provides direct and accurate measurements without requiring model assumptions. It directly captures optical distortion caused by the density gradient in the nozzle wake using high-speed schlieren images, realistically reproducing complex flow field details such as shock waves, turbulence, and flow separation. This avoids computational biases caused by turbulence model assumptions and mesh generation in numerical simulations, resulting in measurement results that more closely approximate the real flow field.

[0047] 2. This invention employs a non-contact measurement method, which does not interfere with the flow field. This invention achieves thrust vector angle measurement solely through optical imaging and image processing, eliminating the need to inject tracer particles into the flow field or install contact sensors. This avoids interference with the wake flow caused by traditional invasive measurements, preserving the original state of the flow field.

[0048] 3. This invention has low equipment requirements, significantly reducing testing costs. It does not rely on high-precision force balances or large-scale wind tunnel equipment; image acquisition can be completed with only a schlieren imaging system. The hardware layout is simple and compact, and the equipment purchase, maintenance, and site costs are significantly lower than existing experimental measurement methods.

[0049] 4. The operation process of this invention is simple and requires no complex calibration. This invention eliminates the cumbersome multi-dimensional pre-calibration and high-precision assembly process of force balances. The thrust vector angle can be quickly obtained through image acquisition, interactive rectangular selection, automated line fitting, and angle bisector calculation. The data processing is highly automated, significantly shortening the testing cycle and meeting the needs of rapid engineering iteration.

[0050] 5. This invention is highly adaptable and can handle complex wake morphologies. Through edge detection, morphological closing operations, and principal boundary filtering in edge preprocessing, this invention can effectively eliminate false edges caused by flow field noise and shock wave interference. It also has good fitting ability for irregular and asymmetric wake boundaries and has a wide range of applications.

[0051] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for measuring the thrust vector angle of a thrust vector nozzle, characterized in that, Includes the following steps: S1. Obtain the high-speed schlieren image of the thrust vector nozzle wake to obtain the original grayscale image; S2. Perform edge preprocessing on the original grayscale image, extract the main boundary of the wake, and obtain the preprocessed image and the coordinate point set of the main boundary of the wake; S3. Perform a first rectangular selection and a second rectangular selection on the preprocessed image to select the first target edge region and the second target edge region of the wake, respectively, to obtain the coordinate range of the first selected region and the coordinate range of the second selected region. S4. Based on the coordinate range of the first framed region and the coordinate range of the second framed region, filter out the first set of edge points located within the coordinate range of the first framed region and the second set of edge points located within the coordinate range of the second framed region from the set of coordinate points of the main boundary of the wake. S5. Perform line fitting on the first edge point set to obtain a first fitted line, and perform line fitting on the second edge point set to obtain a second fitted line; S6. Based on the first fitted line and the second fitted line, calculate the angle bisector of the two lines and obtain the equation of the angle bisector; S7. Calculate the inclination angle of the angle bisector according to the angle bisector equation, use it as the thrust vector angle, and output the thrust vector angle.

2. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, Step S2 specifically includes: The Canny operator is used to perform edge detection on the original grayscale image to obtain an edge image; Perform morphological closing operations on the edge image to fill the edge gaps; Remove noise regions with an area smaller than a preset threshold; The largest connected region in the image is extracted as the main boundary of the wake. All coordinate points of the main boundary are obtained to obtain the set of coordinate points of the main boundary of the wake. The image after the above processing is used as the preprocessed image.

3. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, Step S3 specifically includes: Generate an image display window and load the preprocessed image; Make the first rectangular selection by dragging the mouse pointer, and save the coordinate range of the first selected area after confirmation; In the same image display window, drag the mouse pointer to make a second rectangular selection, and save the coordinate range of the second selected area after confirmation.

4. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, Before filtering out the first set of edge points within the coordinate range of the first selected area and the second set of edge points within the coordinate range of the second selected area, the method further includes: converting the rectangular selection box position parameters in the coordinate range of the first selected area and the coordinate range of the second selected area into the start and end ranges of the horizontal and vertical coordinates in the global coordinate system of the image, and ensuring that the coordinate values ​​do not exceed the actual size of the image through boundary constraints.

5. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, In step S5, the straight line fitting adopts the first-order polynomial fitting method.

6. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, Step S6 specifically includes: Verify whether the first fitted line and the second fitted line are parallel; If parallel, output a parallel prompt; If the lines are not parallel, find the intersection point of the two lines, and calculate the slope and equation of the angle bisector based on the coordinates of the intersection point and the slopes of the two lines to obtain the equation of the angle bisector.

7. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, After obtaining the angle bisector equation, the process also includes a visualization output step: superimposing the first fitted line, the second fitted line, and the angle bisector onto the original grayscale image, and outputting the slope and arctangent angle of the angle bisector.

8. The method for measuring the thrust vector nozzle vector angle according to claim 2, characterized in that, In the step of edge detection using the Canny operator, the high and low thresholds of the Canny operator are adaptively set according to the grayscale distribution of the image; the morphological closing operation uses circular structuring elements.

9. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, In step S7, the step of calculating the inclination angle of the angle bisector based on the angle bisector equation as the thrust vector angle specifically includes: calculating the slope of the angle bisector in the global coordinate system of the image, calculating the arctangent angle based on the slope, and outputting the arctangent angle as the thrust vector angle.

10. The method for measuring the thrust vector nozzle vector angle according to claim 1, characterized in that, In step S1, acquiring a high-speed schlieren image of the thrust vector nozzle wake includes: using a high-speed schlieren imaging system to capture the optical distortion caused by the density gradient of the nozzle wake, without the need to inject tracer particles or install contact sensors, thus achieving interference-free imaging of the flow field.

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