A wind tunnel model transition detection method based on refrigerant

Abstract

A wind tunnel model transition detection method based on refrigerant belongs to the field of wind tunnel test technology. It includes processing multiple cavities at the bottom of the wind tunnel test model, and a surface cover is set on the wind tunnel test model on one side of the cavity; connecting the cavities; connecting the cavities with the external atmospheric environment; sealing and heat-insulating the surface of the wind tunnel test model and the connection between the wind tunnel test model and the pipeline; before the transition test, putting the refrigerant into the cavity and closing the surface cover of the wind tunnel test model; sealing the cavity and the surface cover of the wind tunnel test model; starting the wind tunnel, and after the wind tunnel test model and the flow field form a temperature difference, using an infrared camera to shoot the transition measurement area on the surface of the wind tunnel test model; solving the problem that the thickness of the electric heating coating sprayed on the surface of the wind tunnel test model affects the test effect, the test efficiency is low, the wind tunnel test section and the inside of the wind tunnel test model are polluted, and the flow field quality is reduced, so as to improve the efficiency of the wind tunnel test.

Description

Technical Field

[0001] The invention relates to a wind tunnel model transition detection method based on refrigerant, belonging to the technical field of wind tunnel tests. Background Art

[0002] The drag of civil aircraft is generally composed of pressure drag, friction drag, and lift drag. By optimizing the shape and other designs, the pressure drag and lift drag can often be reduced to a lower level. In the cruising state, the friction drag can account for up to half of the total drag. Since the friction drag of the turbulent boundary layer is much greater than that of the laminar boundary layer, by expanding the laminar range of the wing surface, the friction drag of the wing can be effectively reduced, thereby providing a considerable drag reduction effect.

[0003] The boundary between turbulence and laminar flow is called the transition layer, so transition detection is an indispensable means in laminar test flight experiments. The turbulent area has a high heat transfer coefficient and a fast heat exchange with the flow field, so the transition position can be determined by measuring the wing surface temperature and the temperature difference before and after the transition. The temperature resolution of infrared technology is about 0.025k, and the use of infrared cameras is fully capable of satisfying transition measurements. However, since the wind tunnel test model and the wind tunnel cannot continuously provide a temperature difference during the wind tunnel test, the temperature difference between laminar flow and turbulent flow is not obvious, which affects the transition measurement. The existing technology also heats the wind tunnel test model, artificially increases the temperature between the wind tunnel test model and the wind tunnel airflow, and uses an infrared camera to shoot, thereby achieving the measurement of the transition position.

[0004] At present, the heating technology mainly involves spraying electric heating coating on the surface of wind tunnel test models. This method has the following defects and shortcomings: First, the electric heating coating has a certain thickness. During the wind tunnel test, the flow field speed is relatively fast, and a small thickness difference will cause the aerodynamic state of the wind tunnel test model surface to deviate; second, the preparation time cost of the electric heating coating is relatively high, which affects the efficiency of the wind tunnel test; third, for some wind tunnel test models that need to be assembled on site, the preparation of the electric heating coating needs to be carried out in the wind tunnel test section. The spraying environment here generally cannot meet the conditions of the spraying clean room, which will not only affect the quality of the coating preparation, but also pollute the wind tunnel test section and reduce the flow field quality; fourth, after the transition detection is completed, it is generally necessary to remove the surface coating of the wind tunnel test model to facilitate the next step of the test. This process also takes a certain amount of time and is easy to pollute the interior and environment of the wind tunnel test model.

[0005] Therefore, it is urgent to propose a refrigerant-based wind tunnel model transition detection method to solve the above technical problems. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the thickness of the electric heating coating sprayed on the surface of the wind tunnel test model in the prior art affects the test effect, the test efficiency is low, and the wind tunnel test section and the inside of the wind tunnel test model are polluted, which reduces the quality of the flow field. A brief overview of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0007] The technical solution of the present invention:

[0008] A wind tunnel model transition detection method based on refrigerant comprises the following steps:

[0009] Step 1: When designing the wind tunnel test model, the transition test area is determined, and the lower part of the wind tunnel test model is processed to dig out a plurality of cavities, and a surface cover is provided on the wind tunnel test model on one side of the cavity;

[0010] Step 2: Connecting the cavities in the wind tunnel test model under the transition detection area;

[0011] Step 3: Use a pipeline to connect one of the cavities along the connection between the wind tunnel test model and the wind tunnel to the external atmospheric environment;

[0012] Step 4: Perform sealing and heat insulation treatment on the surface of the wind tunnel test model and the connection between the wind tunnel test model and the pipeline;

[0013] Step 5: Before the transition test, put the refrigerant into the cavity and close the surface cover of the wind tunnel test model;

[0014] Step 6: Sealing the cavity and the surface cover of the wind tunnel test model;

[0015] Step 7: Start the wind tunnel, and after a temperature difference is formed between the wind tunnel test model and the flow field, use an infrared camera to photograph the transition measurement area on the surface of the wind tunnel test model;

[0016] Step 8: After the test is completed, open the surface cover of the wind tunnel test model and remove the remaining refrigerant.

[0017] The wind tunnel test model comprises a fuselage and wings located on both sides of the fuselage, cavities are processed in the fuselage and the wings on both sides, and the cavities in the fuselage and the wings on both sides are connected to each other.

[0018] The refrigerant placed in the cavity is dry ice.

[0019] In step seven, the refrigerant utilizes the heat absorption principle of dry ice sublimation to keep the transition area to be tested on the surface of the wind tunnel test model at a low temperature, thereby forming a temperature difference with the flow field.

[0020] The present invention has the following beneficial effects:

[0021] 1. The built-in refrigerant of the present invention replaces the traditional electric heating coating on the surface of the wind tunnel test model, reducing the aerodynamic interference of the coating thickness on the surface of the wind tunnel test model;

[0022] 2. The present invention reduces the time cost of traditional transition detection preparation work and improves the efficiency of wind tunnel testing;

[0023] 3. The present invention is not affected by the type of wind tunnel test model. No matter what kind of wind tunnel test model is used, after the on-site preparation is completed, the refrigerant can be added to start the test, and the pollution of the wind tunnel caused by the coating preparation is reduced;

[0024] 4. The present invention reduces the coating cleaning steps existing in the prior art and reduces the pollution to the wind tunnel test model and the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the coordination of the wind tunnel test model and the cavity of the present invention.

[0026] In the figure: 1- wind tunnel test model, 2- cavity, 3- pipeline. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0028] The connection mentioned in the present invention is divided into fixed connection and detachable connection. The fixed connection is a non-detachable connection including but not limited to conventional fixed connection methods such as folding connection, rivet connection, bonding connection and welding connection. The detachable connection includes but not limited to conventional detachable methods such as threaded connection, snap connection, pin connection and hinge connection. When the specific connection method is not clearly defined, it is assumed that at least one connection method can always be found in the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example: a fixed connection is selected as a welding connection, and a detachable connection is selected as a hinge connection.

[0029] Example: Combination Figure 1 The present embodiment is described. A wind tunnel model transition detection method based on refrigerant in the present embodiment comprises the following steps:

[0030] Step 1: When designing the wind tunnel test model 1, the transition test area is determined according to user needs or concerned parts, and the lower part of the wind tunnel test model 1 is processed to dig out multiple cavities 2. The cavities 2 correspond to the test parts of the wind tunnel test model 1. The plane shape of the cavity 2 is designed to be a polygon close to the transition test area as much as possible, and a surface cover is provided on the wind tunnel test model 1 on one side of the cavity 2. In addition to the surface cover, thermal insulation layers are provided in other areas to facilitate directional cooling;

[0031] Step 2: connecting the cavities 2 in the wind tunnel test model 1 located below the transition detection area;

[0032] Step 3: Use the pipeline 3 to connect one of the cavities 2 along the connection between the wind tunnel test model 1 and the wind tunnel to the external atmospheric environment, in order to prevent the refrigerant from gasifying and expanding and causing an explosion;

[0033] Step 4: The surface of the wind tunnel test model 1 and the connection between the wind tunnel test model 1 and the pipeline 3 are sealed and heat-insulated. During the heat insulation treatment, rock wool, polyurethane foam and other similar materials can be used;

[0034] Step 5: Before the transition test, put the refrigerant into the cavity 2 and close the surface cover of the wind tunnel test model 1;

[0035] Step 6: The cavity 2 and the surface cover of the wind tunnel test model 1 are sealed to prevent the refrigerant from gasifying and leaking from the model surface, thereby affecting the aerodynamic characteristics of the model surface. At the same time, the refrigerant mainly absorbs the heat on the surface of the wind tunnel test model, thereby reducing its temperature impact on other positions of the wind tunnel test model.

[0036] Step 7: Start the wind tunnel, and after a temperature difference is formed between the wind tunnel test model 1 and the flow field, use an infrared camera to photograph the transition measurement area on the surface of the wind tunnel test model 1;

[0037] Step 8: After the test is completed, open the surface cover of the wind tunnel test model 1 and remove the remaining refrigerant.

[0038] The wind tunnel test model 1 includes a fuselage and wings located on both sides of the fuselage. Cavities 2 are processed in the fuselage and the wings on both sides, and the cavities 2 in the fuselage and the wings on both sides are connected to each other.

[0039] The refrigerant placed in the cavity 2 is dry ice or other similar materials. The refrigerant should be in a shape with the smallest possible contact area with the air while meeting the temperature reduction requirement.

[0040] In step seven, the refrigerant utilizes the heat absorption principle of dry ice sublimation to maintain the low temperature state of the transition area to be tested on the surface of the wind tunnel test model, forming a temperature difference with the flow field. Due to the different heat transfer coefficients between the laminar flow area and the turbulent flow area in the flow field, under this condition, the heat transfer in the laminar flow area is slow, and when photographed by an infrared camera, the temperature is close to that of the low-temperature surface cover. The heat transfer in the turbulent area is fast, and when photographed by an infrared camera, the temperature is close to that of the high-temperature airflow, thereby forming a temperature difference and measuring the transition position. The designed cavity 2 is connected to the atmosphere in order to prevent dry ice from sublimating and causing explosions due to volume expansion.

[0041] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A wind tunnel model transition detection method based on refrigerant, characterized in that: The following steps are involved: Step 1: when designing a wind tunnel test model (1), a transition test area is determined, and the lower part of the wind tunnel test model (1) is processed to dig out a plurality of cavities (2), and a surface cover is provided on the wind tunnel test model (1) on one side of the cavity (2); Step 2: connecting the cavities (2) in the wind tunnel test model (1) located below the transition detection area; Step 3: Use a pipe (3) to connect one of the cavities (2) along the connection between the wind tunnel test model (1) and the wind tunnel to the external atmospheric environment; Step 4: performing sealing and heat insulation treatment on the surface of the wind tunnel test model (1) and the connection between the wind tunnel test model (1) and the pipeline (3); Step 5: Before the transition test, the refrigerant is placed in the cavity (2) and the surface cover of the wind tunnel test model (1) is closed; Step 6: sealing the cavity (2) and the surface cover of the wind tunnel test model (1); Step 7: Start the wind tunnel, and after a temperature difference is formed between the wind tunnel test model (1) and the flow field, use an infrared camera to photograph the transition measurement area on the surface of the wind tunnel test model (1); Step 8: After the test is completed, open the surface cover of the wind tunnel test model (1) and remove the remaining refrigerant.

2. The refrigerant-based wind tunnel model transition detection method according to claim 1, characterized in that: The wind tunnel test model (1) comprises a fuselage and wings located on both sides of the fuselage, wherein cavities (2) are processed in the fuselage and the wings on both sides, and the cavities (2) in the fuselage and the wings on both sides are interconnected.

3. The refrigerant-based wind tunnel model transition detection method according to claim 2, characterized in that: The refrigerant placed in the cavity (2) is dry ice.

4. The refrigerant-based wind tunnel model transition detection method according to claim 3, characterized in that: In step seven, the refrigerant utilizes the heat absorption principle of dry ice sublimation to keep the transition area to be tested on the surface of the wind tunnel test model at a low temperature, thereby forming a temperature difference with the flow field.

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