Calibration method and indicator device for speed and Mach number in supersonic variable Mach number wind tunnel

Abstract

The invention relates to the technical field of wind tunnels, and discloses a calibration method and an indicating device for the speed and Mach number of a supersonic variable Mach number wind tunnel. A grid model is generated according to a drawn two-dimensional model of a supersonic variable Mach number wind tunnel and a computational fluid module is introduced. After steady-state calculation converges, a dynamic grid model is started to calculate transient state. The transient state calculation is to import a UDF program compiled according to a formula to control the rotation of the wind tunnel model, monitor the Mach number and speed of an experimental area, and obtain a Mach number cloud map. During the model simulation rotation process, a set of data is monitored every 0.006° rotation. According to the monitoring result, a function relationship curve diagram of the Mach number and the rotation angle and a function relationship curve diagram of the speed and the rotation angle are drawn. The wind tunnel is calibrated according to a relationship fitting function of the Mach number and the rotation angle obtained by simulation and a relationship fitting function of the speed and the rotation angle. The invention can solve the problem of displacement thickness correction of the boundary layer of the variable Mach number wind tunnel, so that the speed and the Mach number of the experimental area are accurately positioned and the indication accuracy is high.

Description

Technical Field

[0001] The invention relates to the technical field of wind tunnels, and in particular to a calibration method and an indicating device for the speed and Mach number of a supersonic variable Mach number wind tunnel. Background Art

[0002] Supersonic variable Mach number wind tunnels are becoming increasingly important in the field of wind tunnels. This type of wind tunnel can be used to study the problem of hypersonic vehicle inlet failure during acceleration and deceleration, the performance changes of aircraft during acceleration and deceleration, the performance changes of combined engines during mode conversion, and the effective evaluation of the dynamic characteristics of ramjet engines. In addition, a variable Mach number wind tunnel can conduct one experiment without changing the nozzle, which is equivalent to multiple experiments in a traditional single Mach number wind tunnel. At the same time, its flow field is closer to the actual flight environment. Currently, there are only two types of popular variable Mach number nozzles in the field of variable Mach number wind tunnels, namely slider nozzles and soft-wall nozzles. The slider nozzle changes the throat area by changing the position of the slider inside the nozzle to achieve Mach number changes. The disadvantage is that the slider wake affects the quality of the outlet flow field. The soft-wall nozzle obtains different curved wall shapes of the nozzle by changing the position of the actuator to achieve changes in the nozzle profile, thereby obtaining different Mach numbers. However, the soft-wall nozzle is difficult to process and control, and has high cost, making it difficult to be widely used. In the nozzle development process of the variable Mach number wind tunnel, due to the influence of the boundary layer, boundary layer correction is often required to achieve the designed Mach number. The boundary layer correction generally uses the Sivells-Payne method to correct the boundary layer displacement thickness. This application is proposed on the basis of the Chinese patent-two-dimensional variable Mach number nozzle and supersonic variable Mach number wind tunnel using the nozzle (application number: CN201410578068.8). The variable Mach number nozzle rotates the nozzle as a whole around the center of the arc expansion surface, and finally realizes the continuous change of the Mach number within a certain range. The boundary layer correction measure is to rotate a certain angle on the basis of the corresponding position of the theoretical value to offset the influence of insufficient expansion of the boundary layer on the expansion wall, so it is necessary to solve the problem of rotating a certain angle.

[0003] Since the supersonic variable Mach number wind tunnel realizes the rotation of the nozzle as a whole around the center of the arc expansion surface through a manual or electric actuation mechanism, the continuous change of the Mach number within a certain range is finally realized. However, during the rotation of the nozzle profile, the Mach number changes continuously, and the displacement thickness of the boundary layer also changes accordingly, which increases the difficulty of correcting the boundary layer thickness. Therefore, there is no method or indicator device that can determine the Mach number and speed of the effective experimental area according to the rotation of the nozzle profile to a certain angle. This makes it difficult to accurately position the manual adjustment of the variable Mach number wind tunnel, and it is also impossible to provide the initial values ​​of the Mach number and speed for the electric adjustment, so as to adjust the flow parameters in the effective experimental area according to a specific rule. Summary of the invention

[0004] The purpose of the present invention is to provide a calibration method and an indication device for the speed and Mach number of a supersonic variable Mach number wind tunnel, solve the problem of displacement thickness correction of the boundary layer of the variable Mach number wind tunnel, and realize precise positioning of the supersonic variable Mach number wind tunnel with high indication accuracy.

[0005] To achieve the above object, one aspect of the present invention provides a method for calibrating speed and Mach number in a supersonic variable Mach number wind tunnel, which comprises the following steps:

[0006] Step 1, drawing a two-dimensional geometric model of a supersonic variable Mach number wind tunnel using drawing software;

[0007] Step 2, importing the two-dimensional geometric model of the supersonic variable Mach number wind tunnel in step 1 into a mesh generation software to generate a mesh model;

[0008] Step 3, import the grid model in step 2 into the computational fluid module of the numerical simulation software, and set parameters according to the operating conditions of the wind tunnel, first perform steady-state calculations, wait for the computational model residuals to converge and become stable, then import the UDF program compiled according to the effective experimental area flow field Mach number regulation law and the effective experimental area flow field velocity regulation law to control the rotation of the wind tunnel model, then start the dynamic grid model of the computational fluid module of the numerical simulation software, perform instantaneous calculations, monitor the Mach number and velocity of the center point of the effective experimental area of ​​the supersonic variable Mach number wind tunnel, and thus calculate the Mach number cloud map; wherein, during the simulated rotation of the wind tunnel model, a group of data of the effective experimental area is monitored every 0.006° rotation;

[0009] Step 4: stop the calculation after the wind tunnel model rotates 22.07°, derive the monitoring results, and draw a graph of the functional relationship between the Mach number and the rotation angle in the effective experimental area, as well as a graph of the functional relationship between the speed and the rotation angle in the effective experimental area;

[0010] Step 5. During the actual experiment of the supersonic variable Mach number wind tunnel, a limited set of data is first tested, and then the supersonic variable Mach number wind tunnel is calibrated based on the fitting function of the relationship between the Mach number and the rotation angle in the effective experimental area and the fitting function of the relationship between the speed and the rotation angle obtained by the numerical analysis software.

[0011] As a preferred solution of the present invention, the formula for implementing the effective experimental area flow field Mach number adjustment law in step 3 is:

[0012]

[0013] In formula (1), C Ma is the adjustment coefficient of the Mach number; Ma0 is the Mach number corresponding to the variable Mach number nozzle at the initial position during wind tunnel operation, t is the time; γ is the air specific heat ratio, ω is the rotation angular velocity.

[0014] As a preferred solution of the present invention, C Ma is a constant or a function of t.

[0015] As a preferred solution of the present invention, the effective experimental area flow field velocity regulation law in step 3 is realized by the formula:

[0016]

[0017] In formula (2), C velocity is the speed adjustment coefficient; ν0 is the incoming flow velocity corresponding to the variable Mach number nozzle at the initial position during wind tunnel operation, t is time; γ is the air specific heat ratio, ω is the rotation angular velocity, T0 is the total temperature, and R is the gas constant of air.

[0018] As a preferred solution of the present invention, C velocity is a constant or a function of t.

[0019] As a preferred solution of the present invention, in step 5, the fitting function of the Mach number and the rotation angle in the effective experimental area is:

[0020]

[0021] In formula (3), θ is the angle, γ is the air specific heat ratio, Ma is the Mach number; a, b, c, and d are all unknown coefficients.

[0022] As a preferred solution of the present invention, in step 5, the fitting function of the speed and rotation angle of the effective experimental area is:

[0023]

[0024] In formula (4), θ is the angle, γ is the specific heat ratio of air, R is the gas constant of air, T0 is the total temperature, V is the velocity; a, b, and c are all unknown coefficients.

[0025] In addition, another aspect of the present invention provides an indicating device for a supersonic variable Mach number wind tunnel, based on the calibration method for the speed and Mach number of the supersonic variable Mach number wind tunnel, including an experimental area Mach number indicating device made according to the calibration result obtained by the calibration method for the speed and Mach number of the supersonic variable Mach number wind tunnel and an experimental area speed indicating device made according to the calibration result obtained by the calibration method for the speed and Mach number of the supersonic variable Mach number wind tunnel.

[0026] Compared with the prior art, the calibration method and indicating device for supersonic variable Mach number wind tunnel speed and Mach number in the embodiment of the present invention have the following beneficial effects:

[0027] The present invention solves the problem of displacement thickness correction of the boundary layer of the variable Mach number wind tunnel by fitting the functional relationship between the rotation angle of the variable Mach number wind tunnel profile and the Mach number of the experimental area and the functional relationship between the rotation angle of the variable Mach number wind tunnel profile and the speed of the experimental area, thereby realizing precise positioning of manual adjustment of the supersonic variable Mach number wind tunnel with high indication accuracy; at the same time, it can provide initial values ​​of the Mach number and the speed for electric adjustment, thereby realizing adjustment of the flow parameters in the effective experimental area according to a specific rule. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0029] Figure 1 It is a schematic diagram of a supersonic variable Mach number wind tunnel grid model provided by the present invention;

[0030] Figure 2 It is a Mach number cloud diagram;

[0031] Figure 3 It is a graph of the relationship between Mach number and rotation angle;

[0032] Figure 4 It is a function graph of the relationship between speed and rotation angle;

[0033] Figure 5 It is a schematic diagram of the Mach number indicating device in the experimental area;

[0034] Figure 6 yes Figure 5 Schematic diagram of the scale marking area of ​​the Mach number indicator in the middle experimental area;

[0035] Figure 7 It is a schematic diagram of the speed indicating device in the experimental area;

[0036] Figure 8 yes Figure 7 Schematic diagram of the scale marking area of ​​the speed indicator device in the middle experimental area. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. It should be understood that the terms "first", "second", etc. are used in the present invention to describe various information, but such information should not be limited to these terms, which are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the "first" information may also be referred to as the "second" information, and similarly, the "second" information may also be referred to as the "first" information.

[0039] like Figures 1 to 8 As shown, the calibration method and indicating device of the supersonic variable Mach number wind tunnel speed and Mach number of the preferred embodiment of the present invention include the following steps:

[0040] Step 1: Draw a two-dimensional geometric model of a supersonic variable Mach number wind tunnel using drawing software (the two-dimensional geometric model here refers to a two-dimensional simplified model of a nozzle section and an experimental section of a supersonic variable Mach number wind tunnel, which can be understood as a central cross section of the nozzle section and the experimental section in a three-dimensional model of a supersonic variable Mach number wind tunnel); in this embodiment, Solidworks software is used to draw a 1:1 two-dimensional model of a variable Mach number nozzle, and its geometric design parameters are based on the design formulas given in the Chinese patent - Two-dimensional variable Mach number nozzle and supersonic variable Mach number wind tunnel using the nozzle (application number: CN201410578068.8).

[0041] Step 2: Import the two-dimensional geometric model of the supersonic variable Mach number wind tunnel in step 1 into a grid generation software to generate a grid model; in this embodiment, the ICEM grid generation module of ansys software or the GEOM grid generation software is used for grid generation.

[0042] Step three, import the grid model in step two into the computational fluid module of the numerical simulation software, and set parameters according to the operating conditions of the wind tunnel, first perform steady-state calculations, wait for the computational model residuals to converge and become stable, then import the UDF program compiled according to the effective experimental area flow field Mach number regulation law and the effective experimental area flow field velocity regulation law to control the rotation of the wind tunnel model (specifically, in this embodiment, the fluent module of ansys software is used for simulation), then start the dynamic grid model of the computational fluid module of the numerical simulation software for instantaneous calculations (that is, the transient calculation is to import the UDF program compiled according to the formula to control the rotation of the wind tunnel model), monitor the Mach number and velocity of the center point of the effective experimental area of ​​the supersonic variable Mach number wind tunnel, and thus calculate the Mach number cloud map (such as Figure 3As shown); wherein, in the wind tunnel model simulation rotation process, the upper wall of the nozzle monitors a set of data of the effective experimental area every time it rotates 0.006°; by monitoring the Mach number and speed of the center point of a set of effective experimental areas every time it rotates 0.006°, the indication accuracy can reach 0.006°, which can accurately position the supersonic variable Mach number wind tunnel.

[0043] Specifically, the formula for implementing the effective experimental area flow field Mach number adjustment law in step 3 is:

[0044]

[0045] In formula (1), C Ma is the adjustment coefficient of the Mach number; Ma0 is the Mach number corresponding to the variable Mach number nozzle at the initial position during wind tunnel operation, t is time; γ is the air specific heat ratio, ω is the rotation angular velocity. And the adjustment coefficient of the Mach number C Ma It is a human-controlled parameter and can be selected as a constant or a function of time t.

[0046] The formula for implementing the effective experimental area flow field velocity regulation law in step 3 is:

[0047]

[0048] In formula (2), C velocity is the speed adjustment coefficient; ν0 is the corresponding incoming flow velocity when the variable Mach number nozzle is at the initial position during wind tunnel operation, t is time; γ is the air specific heat ratio, ω is the rotation angular velocity, T0 is the total temperature, and R is the gas constant of the air. And the speed adjustment coefficient C velocity It is a human-controlled parameter and can be selected as a constant or a function of time t.

[0049] Step 4: Stop the calculation after the wind tunnel model rotates 22.07°, export the monitoring results, and draw a functional relationship curve between the Mach number and the rotation angle of the effective experimental area (such as Figure 3 As shown), and the function relationship curve of the speed and rotation angle of the effective experimental area (as shown Figure 4 The supersonic variable Mach number wind tunnel itself is designed to rotate 22.07°;

[0050] Step 5: In the actual experiment process of the supersonic variable Mach number wind tunnel, a limited set of data is first tested, and then the supersonic variable Mach number wind tunnel is calibrated according to the fitting function of the relationship between the Mach number and the rotation angle in the effective experimental area and the fitting function of the relationship between the speed and the rotation angle obtained by the numerical analysis software. Specifically, the fitting function of the Mach number and the rotation angle in the effective experimental area is:

[0051]

[0052] In formula (3), θ is the angle, γ is the air specific heat ratio, Ma is the Mach number; a, b, c, and d are all unknown coefficients.

[0053] In this embodiment, Matlab software is used to fit the calibration function, and the function of the Mach number and the rotation angle fitting is as follows:

[0054] val=

[0055] General model:

[0056] val(X)=2.44949*atan(sqrt(0.166667*(X^2-1)))*180 / pi-atan(sqrt(X^

[0057] 2-1))*180 / pi+a*X^3+b*X^2+c*X+d

[0058] Coefficients(with 95%confidence bounds):

[0059] a=-0.1341(-0.1864,-0.08172)

[0060] b=1.805(1.229,2.381)

[0061] c=-7.485(-9.586,-5.384)

[0062] d=-38.93(-41.47,-36.4)

[0063] In this embodiment, Matlab software is used to fit the calibration function, and the fitting function of the speed and rotation angle of the effective experimental area is:

[0064]

[0065] In formula (4), θ is the angle, γ is the specific heat ratio of air, R is the gas constant of air, T0 is the total temperature, V is the velocity; a, b, and c are all unknown coefficients.

[0066] The function of speed and rotation angle fitting is as follows:

[0067] val=

[0068] General model:

[0069] val(X)=2.44949*atan(sqrt(0.166667*((X^2 / (120540-0.2*X^2)-1))))*180 /

[0070] pi-atan(sqrt((X^2 / (120540-0.2*X^2)-1)))*180 / pi+a*X^2+b*X+cCoefficients(with 95%confidence bounds):

[0071] a=0.0001547(0.0001451,0.0001643)

[0072] b=-0.1992(-0.2118,-0.1866)

[0073] c=15.2(11.08,19.31)

[0074] In addition, an embodiment of the present invention further provides an indicating device for a supersonic variable Mach number wind tunnel, based on the above-mentioned supersonic variable Mach number wind tunnel speed and Mach number calibration method, including an experimental area Mach number indicating device (such as Figure 5 , 6 ) and a test area speed indicating device (such as a speed indicating device made by the calibration result obtained by the calibration method of the supersonic variable Mach number wind tunnel speed and Mach number) Figure 7 , 8 shown).

[0075] In summary, the present invention solves the problem of correction of displacement thickness of the boundary layer of the variable Mach number wind tunnel (i.e., the problem of how much additional rotation angle is required for boundary layer correction of the variable Mach number wind tunnel) by fitting the functional relationship between the rotation angle of the variable Mach number wind tunnel profile and the Mach number of the experimental area and the functional relationship between the rotation angle of the variable Mach number wind tunnel profile and the speed of the experimental area, thereby achieving precise positioning of manual adjustment of the supersonic variable Mach number wind tunnel with high indication accuracy; at the same time, it can provide the initial values ​​of the Mach number and the speed for the electric adjustment, thereby achieving the adjustment of the flow parameters in the effective experimental area according to a specific rule.

[0076] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for calibrating the speed and Mach number of a supersonic variable Mach number wind tunnel, characterized in that: The following steps are involved: Step 1, drawing a two-dimensional geometric model of a supersonic variable Mach number wind tunnel using drawing software; Step 2, importing the two-dimensional geometric model of the supersonic variable Mach number wind tunnel in step 1 into a mesh generation software to generate a mesh model; Step 3, import the grid model in step 2 into the computational fluid module of the numerical simulation software, and set parameters according to the operating conditions of the wind tunnel, first perform steady-state calculations, wait for the computational model residuals to converge and become stable, then import the UDF program compiled according to the effective experimental area flow field Mach number regulation law and the effective experimental area flow field velocity regulation law to control the rotation of the wind tunnel model, then start the dynamic grid model of the computational fluid module of the numerical simulation software, perform instantaneous calculations, monitor the Mach number and velocity of the center point of the effective experimental area of ​​the supersonic variable Mach number wind tunnel, and thus calculate the Mach number cloud map; wherein, during the simulated rotation of the wind tunnel model, a group of data of the effective experimental area is monitored every 0.006° rotation; The formula for adjusting the Mach number of the flow field in the effective experimental area is: In formula (1), C Ma is the adjustment coefficient of the Mach number; Ma0 is the Mach number corresponding to the variable Mach number nozzle at the initial position during wind tunnel operation, t is the time; γ is the air specific heat ratio, ω is the rotation angular velocity; The formula for realizing the velocity regulation law of the flow field in the effective experimental area is: In formula (2), C velocity is the speed adjustment coefficient; ν0 is the corresponding incoming flow velocity when the variable Mach number nozzle is at the initial position during wind tunnel operation; t is the time; γ is the specific heat ratio of air, ω is the angular velocity of rotation, T0 is the total temperature, and R is the gas constant of air; Step 4: stop the calculation after the wind tunnel model rotates 22.07°, derive the monitoring results, and draw a graph of the functional relationship between the Mach number and the rotation angle of the effective experimental area, as well as a graph of the functional relationship between the speed and the rotation angle of the effective experimental area; Step 5. During the actual experiment of the supersonic variable Mach number wind tunnel, a limited set of data is first tested, and then the supersonic variable Mach number wind tunnel is calibrated based on the fitting function of the relationship between the Mach number and the rotation angle in the effective experimental area and the fitting function of the relationship between the speed and the rotation angle obtained by the numerical analysis software.

2. The method for calibrating the speed and Mach number of a supersonic variable Mach number wind tunnel according to claim 1, characterized in that: C Ma is a constant or a function of t.

3. The method for calibrating the speed and Mach number of a supersonic variable Mach number wind tunnel as claimed in claim 1, characterized in that: C velocity is a constant or a function of t.

4. The method for calibrating the speed and Mach number of a supersonic variable Mach number wind tunnel as claimed in claim 1, characterized in that: In step 5, the fitting function of the Mach number and the rotation angle in the effective experimental area is: In formula (3), θ is the angle, γ is the air specific heat ratio, Ma is the Mach number; a, b, c, and d are all unknown coefficients.

5. The method for calibrating the speed and Mach number of a supersonic variable Mach number wind tunnel as claimed in claim 1, characterized in that: In step 5, the fitting function of the speed and rotation angle of the effective experimental area is: In formula (4), θ is the angle, γ is the specific heat ratio of air, R is the gas constant of air, T0 is the total temperature, V is the velocity; a, b, and c are all unknown coefficients.

6. An indicator device for a supersonic variable Mach number wind tunnel, characterized in that: A supersonic variable Mach number wind tunnel speed and Mach number calibration method based on any one of claims 1 to 5, comprising an experimental area Mach number indicating device made using the calibration results obtained by the supersonic variable Mach number wind tunnel speed and Mach number calibration method and an experimental area speed indicating device made using the calibration results obtained by the supersonic variable Mach number wind tunnel speed and Mach number calibration method.

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