A method for repairing a hypersonic nozzle inner contour

Abstract

This invention relates to a method for repairing the internal profile of a hypersonic nozzle, belonging to the field of wind tunnel testing. It involves numerical simulation of the nozzle profile; analysis of whether the nozzle flow field is under-expanded or over-expanded based on nozzle exit flow field calibration data; and repair of the nozzle under-expanded or over-expanded state using either left-hand or right-hand characteristic line region correction methods. Based on the original nozzle profile, this invention only requires localized repair of the profile to achieve excellent flow field quality, while being low-cost and short-cycle, and can be quickly applied to hypersonic nozzles with poor flow fields. This invention can provide high-quality hypersonic wind tunnel aerodynamic data for aircraft development and can simulate flight environments.

Description

Technical Field

[0001] This invention belongs to the field of wind tunnel testing and relates to a method for repairing the internal profile of a hypersonic nozzle. Background Technology

[0002] In hypersonic wind tunnel testing, the nozzle is a key component for obtaining the required uniform test airflow in the test section, affecting the quality of the hypersonic test airflow. Hypersonic flows are characterized by high speed, large gradients, strong discontinuities, complex thermal coupling, and limited propagation area, making their design technology extremely complex. With the development of modern aerodynamics, the research content of wind tunnel testing is becoming increasingly diversified, and the requirements for wind tunnel testing capabilities are also becoming increasingly stringent.

[0003] Hypersonic wind tunnels have been developed for decades, and corresponding nozzle design technology has also been developed for decades. However, the existing hypersonic nozzle design methods and theories are relatively outdated, and the nozzle exit flow field parameters cannot meet the development needs of current wind tunnel tests. At the same time, the processing cost of new nozzles is high and the cycle is long. In order to save costs and improve flow field quality, it is urgent to develop a method for repairing the internal profile of hypersonic nozzles, improve the flow field quality of the test section, and make its flow field quality meet excellent parameters, so as to provide corresponding support for the high-quality wind tunnel test aerodynamic data required for the development of advanced aircraft. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a method for repairing the internal profile of a hypersonic nozzle. Based on the original nozzle profile, only local repair of the profile is required to achieve excellent flow field quality. At the same time, it is low in cost and short in cycle, and can be quickly applied to hypersonic nozzles with poor flow field.

[0005] The solution of the present invention is:

[0006] A method for repairing the internal profile of a hypersonic nozzle includes:

[0007] Numerical simulation of the nozzle profile;

[0008] Based on the nozzle exit flow field calibration data, analyze whether the nozzle flow field is under-expanded or over-expanded.

[0009] For nozzles that are under-expanded or over-expanded, the method of left-side feature line region correction or right-side feature line region correction is used for repair.

[0010] In the aforementioned method for repairing the internal profile of a hypersonic nozzle, when the total temperature of the nozzle sump chamber is less than 800K, the numerical simulation uses the ideal gas equation; when the total temperature of the nozzle sump chamber is between 800-1600K, the numerical simulation uses the complete gas equation; when the total temperature of the nozzle sump chamber is between 1600-2500K, the numerical simulation uses the chemical non-equilibrium gas equation; when the total temperature of the nozzle sump chamber is greater than 2500K, the numerical simulation uses the thermochemical non-equilibrium gas equation; and when there are liquid or solid particles in the nozzle sump chamber, the numerical simulation uses the multiphase flow gas equation.

[0011] In the above-mentioned method for repairing the internal profile of a hypersonic nozzle, the nozzle expansion section consists of 3 parts or 2 parts; when it is 3 parts, it includes the left-moving region section TA, the conical flow region section GA, and the right-moving region section AD; when the G point and A point of the hypersonic nozzle coincide, it only includes 2 parts, namely the left-moving region section TA and the right-moving region section AD.

[0012] In the above-mentioned method for repairing the internal profile of a hypersonic nozzle, the nozzle profile slope is calculated using a polynomial interpolation method, specifically the Hermit interpolation polynomial method.

[0013] In the aforementioned method for repairing the internal profile of a hypersonic nozzle, when the nozzle is in a state of underexpansion, the numerical simulation results show that a closed region with Mach number Ma1 appears on the central axis of the nozzle. A slope β is selected at point G, and a conic section is constructed using this slope β, extending G towards T to point F, where the x-coordinate of point F is x. F The vertical axis is y F .

[0014] In the above-mentioned method for repairing the internal profile of a hypersonic nozzle, the equation for the TF curve is:

[0015]

[0016]

[0017] In the formula, x and y are the coordinate points of the TF curve equation.

[0018] In the above-mentioned method for repairing the internal profile of a hypersonic nozzle, NT, TF, FG, GA and AD are connected to generate a new nozzle profile; numerical simulation technology is used for numerical calibration; when the quality of the experimental flow field does not meet the requirements, the position of point F is modified, and the modification standard can be to change the airflow deflection angle α, and iterative processing is performed, with the α value selected in each iteration being 0.2° to 0.5°, until the requirements are met.

[0019] In the aforementioned method for repairing the internal profile of a hypersonic nozzle, when the nozzle is in an overexpansion state, the numerical simulation results show that a boundary layer increases sharply at the nozzle exit, causing the Mach number Ma2 to deflect sharply towards the centerline. The rightward-moving region segment is reconstructed using a 7th to 8th order Bézier curve. Point A is selected as the initial starting point of the Bézier curve, and point D1 is selected as the final ending point of the Bézier curve. The radial extension distance from point D1 to point D is d, and the value of d ranges from 5 to 15 mm. The reconstructed Bézier curve is monotonic, and its second derivative is continuous.

[0020] In the aforementioned method for repairing the internal profile of a hypersonic nozzle, the Bézier curve is expressed as a combination of the position vectors of the vertices of the characteristic polygon and Bernstein basis functions:

[0021]

[0022]

[0023] In the formula, n is the degree of the Bézier curve;

[0024] i is the index of the vertex of the feature line, 0≤i≤n;

[0025] u is a parameter, 0≤u≤1; Vi is the position vector of the vertex of the feature polygon.

[0026] J n,i These are Bernstein basis functions. It is the combination number.

[0027] In the aforementioned method for repairing the internal profile of a hypersonic nozzle, a rightward characteristic curve of the nozzle is reconstructed using 7-8 Bézier curves. The first three vertices ensure the continuity of the parameters at the initial point and the first and second derivatives, while the last three points ensure the continuity of the parameters at the end point and the first and second derivatives. The remaining points are used to control the curve shape. Numerical simulation technology is used to numerically calibrate the new curve. When the experimental flow field quality does not meet the requirements, the coordinates of the points used to control the curve shape are changed, and the process is iterated until the requirements are met.

[0028] The beneficial effects of this invention compared to the prior art are:

[0029] (1) Based on the original nozzle profile, the present invention only needs to make local repairs to the profile, and the flow field quality can reach excellent indicators.

[0030] (2) This invention is low in cost and short in cycle time, and can be quickly applied to hypersonic nozzles with poor flow fields. This invention can provide high-quality hypersonic wind tunnel test aerodynamic data for aircraft development and can simulate flight environment. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the nozzle profile and corresponding slope of the present invention;

[0032] Figure 2 This is a schematic diagram of the flow field in the underexpansion nozzle of the present invention;

[0033] Figure 3 This is a schematic diagram of the flow field through the expansion nozzle of the present invention;

[0034] Figure 4 This is a flowchart illustrating the process of repairing the internal profile of the hypersonic nozzle according to the present invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments.

[0036] This invention provides a method for repairing the internal profile of a hypersonic nozzle, relating to the field of wind tunnel testing. For hypersonic wind tunnel nozzles, various factors, such as the lack of consideration for the nozzle inlet boundary layer during initial design, the absence of the characteristic line method in the design due to its early design date, or inadequate boundary layer correction, result in an under-expanded or over-expanded flow field within the nozzle. This leads to an uneven flow field at the nozzle exit, resulting in flow field quality in the test section failing to meet excellent specifications and causing significant deviations in the aerodynamic parameters of the test model. Redesigning and developing a new nozzle is costly and time-consuming. This invention, based on the existing nozzle profile, only requires localized repair of the profile to achieve excellent flow field quality. Simultaneously, it is low-cost, quick to develop, and can be rapidly applied to hypersonic nozzles with poor flow fields. This invention can provide high-quality aerodynamic data for hypersonic wind tunnel testing for aircraft development, simulating the flight environment.

[0037] The method for repairing the internal profile of a hypersonic nozzle includes the following steps:

[0038] Numerical simulations were performed on the nozzle profile. When the total temperature of the nozzle sump chamber was less than 800 K, the numerical simulation used the ideal gas equation; when the total temperature of the nozzle sump chamber was between 800 and 1600 K, the numerical simulation used the perfect gas equation; when the total temperature of the nozzle sump chamber was between 1600 and 2500 K, the numerical simulation used the chemical non-equilibrium gas equation; when the total temperature of the nozzle sump chamber was greater than 2500 K, the numerical simulation used the thermochemical non-equilibrium gas equation; and when there were liquid or solid particles in the nozzle sump chamber, the numerical simulation used the multiphase flow gas equation.

[0039] Based on the nozzle exit flow field calibration data, analyze whether the nozzle flow field is under-expanded or over-expanded.

[0040] For nozzles that are under-expanded or over-expanded, the method of left-side feature line region correction or right-side feature line region correction is used for repair.

[0041] The nozzle expansion section consists of either two or three parts; when it has three parts, it includes the left-moving region section TA, the conical flow region section GA, and the right-moving region section AD, as shown below. Figure 1 As shown. When points G and A of the hypersonic nozzle coincide, it consists of only two parts: the left-hand section TA and the right-hand section AD.

[0042] The nozzle profile slope is calculated using polynomial interpolation, specifically the Hermit interpolation polynomial method.

[0043] When the nozzle is in a state of underexpansion, such as Figure 2 As shown, the numerical simulation results show that a closed region with Mach number Ma1 appears on the central axis of the nozzle; a slope β is selected at point G, and a conic section is drawn using this slope β, extending G towards T to point F, where the x-coordinate of point F is x. F The vertical axis is y F The equation of the TF curve is:

[0044]

[0045]

[0046] In the formula, x and y are the coordinate points of the TF curve equation.

[0047] Connect NT, TF, FG, GA, and AD to generate a new nozzle profile; use numerical simulation technology to perform numerical calibration; when the test flow field quality does not meet the requirements, modify the position of point F. The modification standard can be changing the airflow deflection angle α. Iterate, and select an α value of 0.2° to 0.5° for each iteration until the requirements are met.

[0048] When the nozzle is in an overexpansion state, such as Figure 3 As shown, the numerical simulation results show that a boundary layer increases sharply at the nozzle exit, causing the Mach number Ma2 to deflect sharply towards the centerline. The rightward segment is reconstructed using a Bézier curve of degree 7-8. Point A is selected as the starting point of the initial end of the Bézier curve, and point D1 is selected as the ending point of the Bézier curve. The radial extension distance from point D1 to point D is d, and the value of d ranges from 5 to 15 mm. The reconstructed Bézier curve is monotonic, and its second derivative is continuous.

[0049] The Bézier curve is formed by combining the position vectors of the vertices of the characteristic polygon with Bernstein basis functions, and its expression is:

[0050]

[0051]

[0052] In the formula, n is the degree of the Bézier curve;

[0053] i is the index of the vertex of the feature line, 0≤i≤n;

[0054] u is a parameter, 0≤u≤1; Vi is the position vector of the vertex of the feature polygon.

[0055] J n,i These are Bernstein basis functions. It is the combination number.

[0056] The nozzle rightward characteristic curve is reconstructed using 7-8 Bézier curves. The first three vertices ensure the continuity of the parameters at the initial point and the first and second derivatives, while the last three points ensure the continuity of the parameters at the end point and the first and second derivatives. The other points are used to control the curve shape. Numerical simulation technology is used to numerically calibrate the new curve. If the experimental flow field quality does not meet the requirements, the coordinates of the points used to control the curve shape are changed, and the process is iterated until the requirements are met.

[0057] Example

[0058] Specific steps are as follows Figure 4 As shown.

[0059] Step 1: Perform numerical simulation of the nozzle profile and, combined with nozzle exit flow field calibration data, analyze whether the nozzle flow field is under-expanded or over-expanded. For under-expanded or over-expanded nozzles, use either left-hand or right-hand characteristic line region correction methods for repair.

[0060] Step 2: When the total temperature of the nozzle sump chamber is less than 800K, the numerical simulation uses the ideal gas equation; when the total temperature of the nozzle sump chamber is between 800 and 1600K, the numerical simulation uses the perfect gas equation; when the total temperature of the nozzle sump chamber is between 1600 and 2500K, the numerical simulation uses the chemical non-equilibrium gas equation; when the total temperature of the nozzle sump chamber is greater than 2500K, the numerical simulation uses the thermochemical non-equilibrium gas equation. When there are liquid or solid particles in the nozzle sump chamber, the numerical simulation uses the multiphase flow gas equation.

[0061] Step 3: The nozzle expansion section consists of 2 or 3 parts: the left-hand flow section TA, the conical flow section GA, and the right-hand flow section AD. See [link / description]. Figure 1 In some hypersonic nozzles, points G and A coincide, and can be considered as having only two parts: the left-hand travel segment TA and the right-hand travel segment AD. The nozzle profile slope is calculated using polynomial interpolation, specifically the Hermit interpolation polynomial method.

[0062] Step 4: See the nozzle under-expansion state. Figure 2The numerical simulation results show a closed region with Mach number Ma1 on the central axis of the nozzle. Choosing a slope β at point G, a conic section is plotted using this slope β, extending G towards T to point F, where the x-coordinate of point F is x. F The vertical axis is y F The equation of the TF curve is:

[0063]

[0064]

[0065] Where x and y are the coordinates of the TF curve equation.

[0066] Connect NT, TF, FG, GA, and AD to generate a new nozzle profile. Numerical simulation is then used for numerical calibration. If the experimental flow field quality does not meet the excellent requirements, the position of point F is modified. The modification standard can be changing the airflow deflection angle α. The process is iterated, with each iteration selecting an α value of 0.2° to 0.5° until the requirements are met.

[0067] Step 5: See nozzle over-expansion state. Figure 3 Numerical simulations show a sharp increase in the boundary layer at the nozzle exit, causing a rapid deflection of the Mach number Ma2 towards the centerline. In this case, a 7th-8th degree Bézier curve is used to reconstruct the rightward-moving region. Point A is chosen as the initial starting point of the Bézier curve, and point D1 is chosen as the final ending point. The radial extension distance from point D1 to point D is d, with a value ranging from 5 to 15 mm. The reconstructed Bézier curve is monotonic, and its second derivative is continuous. The specific method is as follows:

[0068] Bézier curves are constructed by combining the position vectors of the vertices of a characteristic polygon with Bernstein basis functions; their expression is as follows:

[0069]

[0070]

[0071] In the formula, n is the degree of the Bézier curve; i is the index of the vertex of the characteristic line, 0≤i≤n; u is the parameter, 0≤u≤1; Vi is the position vector of the vertex of the characteristic polygon, J n,i These are Bernstein basis functions. The number of combinations is used. A nozzle rightward characteristic curve is reconstructed from a 7-8 degree Bézier curve. The first three vertices ensure the continuity of the parameters at the initial point and the first and second derivatives, while the last three points ensure the continuity of the parameters at the end point and the first and second derivatives. The remaining points are used to control the curve shape. Numerical simulation techniques are used to numerically calibrate the new curve. If the experimental flow field quality does not meet the excellent requirements, the coordinates of the points used to control the curve shape should be iterated until the requirements are met.

[0072] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method of repairing a hypersonic nozzle inner contour, characterized by: include: Numerical simulation of the nozzle profile; When the total temperature of the nozzle sump chamber is less than 800K, the numerical simulation uses the ideal gas equation; when the total temperature of the nozzle sump chamber is between 800-1600K, the numerical simulation uses the complete gas equation; when the total temperature of the nozzle sump chamber is between 1600-2500K, the numerical simulation uses the chemical non-equilibrium gas equation; when the total temperature of the nozzle sump chamber is greater than 2500K, the numerical simulation uses the thermochemical non-equilibrium gas equation; when there are liquid or solid particles in the nozzle sump chamber, the numerical simulation uses the multiphase flow gas equation. Based on the nozzle exit flow field calibration data, analyze whether the nozzle flow field is under-expanded or over-expanded. For nozzles that are under-expanded or over-expanded, the method of left-side feature line region correction or right-side feature line region correction is used for repair.

2. The method of claim 1, wherein: The nozzle expansion section consists of 3 or 2 parts; when it is 3 parts, it includes the left-moving region section TA, the conical flow region section GA, and the right-moving region section AD; when the G and A points of the hypersonic nozzle coincide, it only includes 2 parts, namely the left-moving region section TA and the right-moving region section AD.

3. The method of claim 2, wherein: The nozzle profile slope is calculated using polynomial interpolation, specifically the Hermit interpolation polynomial method.

4. The method of claim 3, wherein: When the nozzle is in a state of underexpansion, the numerical simulation results show that a closed region with Mach number Ma1 appears on the central axis of the nozzle; a slope β is selected at point G, and a conic section is drawn using this slope β, extending G towards T to point F, where the x-coordinate of point F is x. F The vertical axis is y F .

5. The method of claim 4, wherein: The equation of the TF curve is: （1） （2） In the formula, x and y are the coordinate points of the TF curve equation.

6. The method of claim 5, wherein: Connect NT, TF, FG, GA, and AD to generate a new nozzle profile; use numerical simulation technology to perform numerical calibration; when the test flow field quality does not meet the requirements, modify the position of point F. The modification standard can be changing the airflow deflection angle α. Iterate, and select an α value of 0.2°~0.5° for each iteration until the requirements are met.

7. The method of claim 6, wherein: When the nozzle is in an overexpansion state, the numerical simulation results show that the boundary layer increases sharply at the nozzle exit, causing the Mach number Ma2 to deflect sharply towards the centerline. The rightward segment is reconstructed using a 7th to 8th order Bézier curve. Point A is selected as the initial starting point of the Bézier curve, and point D1 is selected as the final ending point of the Bézier curve. The radial extension distance from point D1 to point D is d, and the value of d ranges from 5 to 15 mm. The reconstructed Bézier curve is monotonic, and its second derivative is continuous.

8. The method of claim 7, wherein: The Bézier curve is formed by combining the position vectors of the vertices of the characteristic polygon with Bernstein basis functions, and its expression is: （3） （4） In the formula, n is the degree of the Bézier curve; i is the index of the vertex of the feature line, 0≤i≤n; u is a parameter, 0≤u≤1; Vi is the position vector of the vertex of the feature polygon. J n,i Bernstein basis functions, is a combinatorial number.

9. The method of claim 8, wherein: The nozzle rightward characteristic curve is reconstructed using 7-8 Bézier curves. The first three vertices ensure the continuity of the parameters at the initial point and the first and second derivatives, while the last three points ensure the continuity of the parameters at the end point and the first and second derivatives. The remaining points are used to control the curve shape. Numerical simulation is used to numerically calibrate the new curve. If the experimental flow field quality does not meet the requirements, the coordinates of the points used to control the curve shape are changed, and the process is iterated until the requirements are met.

Images