A method for measuring boundary layer transition information on large-scale thin-walled models

Abstract

The present invention discloses a method for measuring the transition information of the boundary layer on the surface of a large-scale thin-walled model. The thin-walled model is processed by high-strength metal. The outer dimensions of the measurement area on the model surface are processed according to negative tolerance. A high-emissivity thermal insulation coating is sprayed on the surface of the model. In a hypersonic wind tunnel that has been running for a long time, after the flow field is established and stabilized, the model is quickly inserted into the flow field. An infrared thermal imager is used to observe the temperature distribution on the model surface in real time. The transition position and shape of the boundary layer on the model surface are determined by the temperature distribution. This method solves the problem of measuring the transition information of the boundary layer on the surface of a large-scale thin-walled model and has the advantages of simple operation and efficient testing.

Description

Technical Field

[0001] The invention relates to a method for measuring boundary layer transition information on the surface of a large-size thin-wall model, and belongs to the field of wind tunnel test measurement. Background Art

[0002] In hypersonic wind tunnels, non-contact surface measurement technologies such as temperature-sensitive coating technology, liquid crystal friction measurement technology, or infrared thermal imaging technology are generally used to display and measure the boundary layer transition on the model surface. Among them, temperature-sensitive coating technology or liquid crystal friction measurement technology requires spraying sensitive coating materials on the model surface, and the test process is complicated and the test efficiency is low. Infrared thermal imaging technology does not require sensitive coating, but is generally suitable for non-metallic material processing models with high emissivity and low thermal conductivity, but the strength of non-metallic materials cannot meet the test requirements of large-scale thin-walled models. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to provide a method for measuring the boundary layer transition information on the surface of a large-sized thin-walled model, and to solve the difficulty in measuring the boundary layer transition on the surface of a large-sized thin-walled model.

[0004] The technical solution of the present invention is:

[0005] A method for measuring boundary layer transition information on the surface of a large-scale thin-walled model, comprising:

[0006] The thin-walled model is made of high-strength metal, and the dimensions of the measured area on the model surface are processed according to negative tolerances;

[0007] Spray a thermal insulation coating with an emissivity greater than 0.9 in a measurement area on the model surface, that is, a negative tolerance processing area, wherein the processing negative tolerance value is the same as the thickness of the thermal insulation coating, and the thermal insulation coating is a non-metallic material;

[0008] In a hypersonic wind tunnel that has been running for a long time, after the wind tunnel flow field is established and stabilized, the model is quickly inserted into the flow field, and an infrared thermal imager is used to measure the surface temperature distribution of the model in real time. The boundary layer transition position and shape are determined by the temperature distribution.

[0009] Preferably, the minimum wall thickness of the model is less than 1 mm, and the ratio of the maximum projected area of ​​the model to the average wall thickness is greater than 500 mm.

[0010] Preferably, the strength of the metal used for thin-walled model processing is not less than the strength of 30CrMnSiA, and the rigidity of the metal used for thin-walled model processing is not less than the rigidity of 30CrMnSiA.

[0011] Preferably, the measured area on the model surface is processed with negative tolerance, and other dimensions of the model are processed with standard tolerance.

[0012] Preferably, the outer dimensions of the model after the thermal insulation coating is sprayed on the surface are consistent with the ideal outer dimensions.

[0013] Preferably, the surface temperature of the model before the test is room temperature, and the temperature distribution is uniform.

[0014] Preferably, when the model is inserted into the flow field, the model attitude angle remains unchanged.

[0015] Preferably, when the model is inserted into the flow field, the running path of the model is parallel to the observation path of the infrared thermal imager.

[0016] Preferably, the acquisition frequency of the infrared thermal imager is not less than 100 Hz.

[0017] Preferably, the infrared thermal imager completely records the changes in surface temperature distribution during the process of inserting the model into the flow field.

[0018] The advantages of the present invention compared with the prior art are:

[0019] (1) The present invention uses high-strength metal materials to process large-sized thin-walled models, thereby ensuring the strength of the model and meeting the requirements of wind tunnel tests;

[0020] (2) The surface of the model of the present invention is sprayed with a high-emissivity thermal insulation coating, which meets the demand for high-precision measurement of the surface temperature distribution of the model;

[0021] (3) The external dimensions of the measurement area of ​​the model of the present invention are processed according to the negative tolerance, and the thickness of the coating on the surface of the model is substantially consistent with the negative tolerance value, thereby ensuring the accuracy of the external dimensions of the model.

[0022] (4) The present invention measures the boundary layer transition information on the model surface in a conventional hypersonic wind tunnel by quickly inserting the model and using an infrared thermal imager to measure the temperature distribution on the model surface in real time. This method has the advantages of simple operation and high test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the model of the present invention;

[0024] Figure 2 Schematic diagram of the wind tunnel test arrangement of the present invention. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings.

[0026] The present invention uses a high-strength metal processing thin-wall model, the outer dimensions of the model measurement area are processed according to the negative tolerance, and a high-emissivity thermal insulation coating is sprayed on the surface of the measurement area. The negative tolerance value is equivalent to the thickness of the thermal insulation coating. In a conventional hypersonic wind tunnel that has been running for a long time, after the wind tunnel flow field is established and stabilized, the model is quickly inserted into the flow field, and an infrared thermal imager is used to measure the model surface temperature distribution in real time, and the boundary layer transition information is obtained through the model surface temperature distribution.

[0027] The specific steps are as follows:

[0028] (1) Figure 1 As shown, firstly, high-strength metal is used to process large-size thin-walled models. The outer dimensions of the model measurement area are processed according to negative tolerances, and other dimensions of the model are processed according to standard tolerances. The minimum wall thickness of the model is less than 1mm, and the strength and rigidity of the metal used for thin-walled model processing is not less than 30CrMnSiA.

[0029] (2) A high-emissivity thermal insulation coating is sprayed on the model measurement area. The thickness of the thermal insulation coating is basically consistent with the value of the negative tolerance of the model processing. The outer dimensions of the model surface after the thermal insulation coating is sprayed are consistent with the ideal shape.

[0030] (3) In a conventional hypersonic wind tunnel with a wind tunnel operation time of more than 10 seconds, the model is placed outside the flow field before the test. After the wind tunnel flow field is established and stabilized, the model is quickly inserted into the flow field, and an infrared thermal imager is used to measure the surface temperature distribution of the model in real time. The acquisition frequency of the infrared thermal imager is not less than 100 Hz.

[0031] (4) Determine the transition position and shape of the boundary layer on the model surface through analyzing the temperature distribution on the model surface.

[0032] In the wind tunnel test, the model and measuring instruments are arranged as follows: Figure 2 As shown in the figure, the model enters the flow field from bottom to top, and the infrared thermal imager captures the surface temperature distribution of the model at the top of the test section. In conventional hypersonic wind tunnels with a running time of seconds, the model is initially placed outside the flow field. After the wind tunnel flow field is established and stabilized, the test model is quickly inserted into the flow field, and the infrared thermal imager is used to fully record the surface temperature distribution information of the model during the insertion of the model into the flow field. The path of the model insertion into the flow field is parallel to the infrared thermal imager shooting path. The information obtained by the infrared thermal imager is sent to the computer, and the surface temperature distribution of the model when the model is just inserted into the flow field is selected on the computer. Considering the surface shape characteristics of the model and aerodynamic knowledge, the transition position and morphology of the boundary layer on the surface of the model are determined.

[0033] The present invention aims at the boundary layer transition test measurement requirements of large-scale thin-walled models. The maximum projected area S (unit: mm) of the thin-walled model 2) to the average wall thickness b (unit: mm) ratio S / b is greater than 500 mm. Use high-strength metal to process large-size thin-wall models to ensure the strength and rigidity of the test model; spray a high-emissivity thermal insulation coating on the model surface to meet the measurement requirements of the infrared thermal imager; the model is processed with negative tolerance, and the negative tolerance value is equal to the coating thickness to ensure the external dimensions of the model after spraying; the surface temperature distribution of the model obtained by measurement is used to determine the surface boundary layer transition information.

[0034] The present invention solves the difficulty in measuring boundary layer transition of large-size thin-walled models, adopts a method of spraying a coating on the model surface with a negative tolerance to ensure the model shape, and combines a high-emissivity heat-insulating coating with an infrared thermal imager for measurement, which has the advantages of simple operation and efficient testing.

[0035] Example 1

[0036] In the transition measurement test of the wing model, the wing model is less than 5mm thick, 380mm long and 120mm wide. The surface machining tolerance of the model is (-10 to -20μm). The surface of the model is sprayed with a ceramic coating with a thickness of about 10 to 20μm, thus ensuring that the dimensional tolerance of the model after spraying the coating is -10 to 10μm.

[0037] The boundary layer transition measurement test was carried out in a conventional hypersonic wind tunnel. The test Mach number was 6 and the wind tunnel operation time was greater than 30s. During the establishment of the wind tunnel flow field, the wing model was placed on the south side of the test section. The infrared thermal imager was used to shoot from south to north through the window on the south side of the test section. After the wind tunnel flow field was established and stabilized, the model was quickly inserted into the flow field from south to north. The insertion time was about 0.15s. The infrared thermal imager acquisition frequency was 100Hz. The model surface temperature distribution obtained when the model just reached the center of the flow field was analyzed to determine the boundary layer transition position and morphology on the wing model surface. The boundary layer transition position and transition morphology information of large-scale thin-walled wing surfaces under different attack angles were obtained.

[0038] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for measuring boundary layer transition information on the surface of a large-scale thin-walled model, characterized in that: The thin-walled model is made of high-strength metal, and the dimensions of the measured area on the model surface are processed according to negative tolerances; A thermal insulation coating with an emissivity greater than 0.9 is sprayed on the surface measurement area of ​​the model, that is, the negative tolerance processing area. The surface measurement area of ​​the model is processed with negative tolerance, and other dimensions of the model are processed according to standard tolerances. The processing negative tolerance value is the same as the thickness of the thermal insulation coating. The thermal insulation coating is a non-metallic material. The outer dimensions of the model after the thermal insulation coating is sprayed are consistent with the ideal outer dimensions; In a hypersonic wind tunnel that has been running for a long time, after the wind tunnel flow field is established and stabilized, the model is quickly inserted into the flow field, and the model surface temperature distribution is measured in real time using an infrared thermal imager. The model surface temperature distribution when the model is just inserted into the flow field is selected, and the surface shape characteristics of the model and aerodynamic knowledge are comprehensively considered to determine the transition position and shape of the model surface boundary layer. When the model is inserted into the flow field, the model attitude angle remains unchanged.

2. The method for measuring the surface boundary layer transition information of a large-scale thin-walled model according to claim 1, characterized in that: The minimum wall thickness of the model is less than 1 mm, and the ratio of the maximum projected area of ​​the model to the average wall thickness is greater than 500 mm.

3. The method for measuring the boundary layer transition information on the surface of a large-scale thin-walled model according to claim 1, characterized in that: The strength of the metal used for thin-walled model processing shall not be less than the strength of 30CrMnSiA, and the rigidity of the metal used for thin-walled model processing shall not be less than the rigidity of 30CrMnSiA.

4. The method for measuring the boundary layer transition information on the surface of a large-scale thin-walled model according to claim 1, characterized in that: Before the test, the surface temperature of the model was room temperature and the temperature distribution was uniform.

5. The method for measuring the boundary layer transition information on the surface of a large-scale thin-walled model as claimed in claim 1, characterized in that: When the model is inserted into the flow field, the model running path is parallel to the observation path of the infrared thermal imager.

6. The method for measuring the boundary layer transition information on the surface of a large-scale thin-walled model according to claim 1, characterized in that: The acquisition frequency of the infrared thermal imager shall not be less than 100 Hz.

7. The method for measuring the boundary layer transition information on the surface of a large-scale thin-walled model according to claim 1, characterized in that: The infrared thermal imager completely records the changes in surface temperature distribution during the model's insertion into the flow field.

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