Flexible thermal insulation material free jet flow examination test device under arc wind tunnel condition

Abstract

A flexible thermal insulation material free jet flow examination test device under an arc wind tunnel condition comprises a rectangular spray pipe, a switching section and a support frame, and the support frame comprises a dimensional thermal insulation inner support and an outer support frame; the switching section is tightly connected with the rectangular spray pipe, the inner molded surface is in smooth transition without steps, and a water cooling channel is arranged in the switching section; the two ends, in the jet flow direction, of the tested flexible heat-proof material are connected with the front side wall and the rear side wall of the outer supporting frame, the maintenance type heat-insulation inner support is located in a cavity of the outer supporting frame and supports the flexible heat-proof material in the vertical direction, certain tension is kept, and the whole model formed by the flexible heat-proof material, the maintenance type heat-insulation inner support and the outer supporting frame is connected with the switching section. And a test whole is formed. According to the invention, the heat-proof and heat-insulation performance and the sealing performance of the flexible heat-insulation material in a free jet heating environment can be examined on the ground.

Description

Technical Field

[0001] The present invention relates to a free jet test device and method for evaluating a flexible thermal insulation material under arc wind tunnel conditions, in particular to a free jet test device and method for evaluating a flexible thermal insulation material under arc wind tunnel conditions in a ground simulation test of aerodynamic thermal protection, which can perform ground simulation evaluation on the high temperature resistance and thermal insulation performance of the flexible thermal insulation material under free jet working conditions. Background Art

[0002] When the Earth return capsule and the Mars landing capsule re-enter or enter the atmosphere, they usually use aerodynamic deceleration to reduce their speed and then land safely by opening a parachute and coordinating rocket reverse thrust or airbag cushioning. When the speed is very high during re-entry (entry), the return capsule (landing capsule) may even need to shuttle through the atmosphere several times to reduce its speed to meet the requirements of the landing system. During this process, the kinetic energy of the return capsule (landing capsule) is converted into internal energy through intense friction with the atmosphere, resulting in a very high temperature on the outer surface of the return capsule (landing capsule), which places very high demands on the thermal protection system.

[0003] In addition, during the aerodynamic deceleration stage, the return capsule (landing capsule) is often required to have a specific aerodynamic shape such as a blunt body in order to decelerate efficiently. The mass of the thermal protection system of this shape is relatively high, and the utilization of the internal space of the return capsule (landing capsule) is also affected.

[0004] The inflatable flexible thermal protection system has the characteristics of light weight and little impact on the appearance of the return capsule (landing capsule), and can solve the above-mentioned problems: the inflatable flexible thermal protection system is a thermal protection system composed of foldable and inflatable flexible insulation materials. It is usually folded and stored inside the return capsule (landing capsule). When re-entering or entering the atmosphere, it is ejected out of the capsule through a mechanism and inflated to form a certain shape, protecting the return capsule (landing capsule) to return to the ground smoothly.

[0005] The key component of the inflatable flexible thermal protection system is the flexible thermal insulation material, which can be divided into three layers according to function and position: the outer layer is the thermal protection layer, the middle layer is the thermal insulation layer, and the inner layer is the airtight layer. The outer thermal protection layer is directly exposed to the high-temperature atmospheric environment and is subjected to the action of high-speed airflow. It has very good high-temperature resistance and mechanical ability, and also requires good elasticity. It is mainly used to prevent the damage of high-temperature airflow to the interior and eliminate the impact of high-speed airflow on the internal materials. The inner airtight layer has the function of inflating and maintaining the shape, has very good elasticity and stability, and also has self-sealing and self-repairing functions. It also has certain requirements for high-temperature resistance. The thermal insulation layer is filled between the thermal protection layer and the airtight layer. Its main function is to prevent the heat of the thermal protection layer from damaging the airtight layer. It has very good thermal insulation performance, and also has certain high-temperature resistance and elasticity.

[0006] Despite its many excellent characteristics, flexible thermal insulation materials are only sub-centimeter thick, so they are increasingly valued in the field of aerodynamic thermal protection. Therefore, it is necessary to conduct comprehensive tests to evaluate them in various complex environments when used in ground equipment simulating the atmosphere.

[0007] The most typical application environment of the thermal protection system is the ablation environment faced by large areas of the fuselage and wing surfaces during high-speed re-entry of an aircraft: the airflow passes over the surface of the thermal insulation material at a speed of 2000 meters per second or even higher, and the airflow and the material surface are subjected to intense friction. A large amount of kinetic energy is converted into internal energy, causing the surface temperature of the material to rise sharply, and the surface temperature can even exceed 3000°C.

[0008] On the ground, the free jet assessment method is often used to simulate the thermal environment faced by large areas of the fuselage and wing surfaces. When conducting ground simulation tests on thermal protection, it is usually necessary to use arc wind tunnel equipment. The arc wind tunnel is a device that uses an electric arc to heat the air and then accelerates it through a Laval nozzle to form a high-temperature and high-speed airflow, which is then blown onto the surface of the thermal insulation material to test its thermal protection and insulation performance.

[0009] Conventional thermal insulation materials are usually solid materials, which are machined into a flat plate shape and installed on ground equipment. They are tested by having high-temperature and high-speed airflow blow across their surface. Flexible thermal insulation materials are different from conventional thermal insulation materials. They are very thin and elastic and have no specific shape. Special methods need to be designed to conduct ground free jet test. Summary of the invention

[0010] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a free jet assessment test device and method for flexible thermal insulation materials under arc wind tunnel conditions, which can assess the thermal insulation performance and sealing performance of flexible thermal insulation materials under free jet heating environment on the ground.

[0011] The purpose of the present invention is achieved through the following technical solutions:

[0012] A free jet test device for flexible thermal insulation materials under arc wind tunnel conditions, comprising a rectangular nozzle, a transition section, and a support frame, wherein the support frame comprises a dimensional thermal insulation inner support and an outer support frame;

[0013] The transition section is tightly connected to the rectangular nozzle, the inner surface has a smooth transition without steps, and a water cooling channel is built in the transition section; the two ends of the flexible heat-proof material to be tested along the jet direction are connected to the front and rear side walls of the outer support frame, and the dimensional insulation inner support is located in the cavity of the outer support frame. The flexible heat-proof material is stretched in the vertical direction and a certain tension is maintained. The model consisting of the flexible heat-proof material, the dimensional insulation inner support and the outer support frame is connected to the transition section to form a test whole.

[0014] A test method based on the above-mentioned flexible thermal insulation material free jet assessment test device comprises:

[0015] Firstly, the assessment shape and test conditions are selected according to the application site of the flexible thermal insulation material and the thermal environment faced by this site. Then, the flexible thermal insulation material is installed on the support frame. The flexible thermal insulation material is pulled by an external pushing device to generate a specific tension and maintain a stable tension during the action of high-temperature and high-speed airflow. The arc wind tunnel is started, and the operating power is gradually increased until the set assessment environment is reached. The high-temperature and high-speed airflow heated by the arc heater and accelerated by the rectangular nozzle interacts with the flexible thermal insulation material in terms of heat and force. The temperature change process of the outer surface of the flexible thermal insulation material is obtained by an infrared thermometer, and the temperature inside the flexible thermal insulation material is obtained by the temperature measuring points between the layers, thereby evaluating the thermal insulation performance of the flexible thermal insulation material.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention applies a set tension to the flexible heat-resistant material through the transition section and the support frame, and places the flexible material at the nozzle outlet for a heat-resistant test, which is in line with the actual use environment;

[0018] (2) The present invention can obtain the anti-heat insulation performance of the flexible material under tension in multiple dimensions through the supporting force of the dimensional bracket on the flexible material and the pulling force of the pulling mechanism on the end surface of the flexible material;

[0019] (3) The supporting force of the dimensional support on the flexible material and the pulling force of the pulling mechanism on the end surface of the flexible material have a pressure stabilizing function, and the set force can be maintained unchanged as the flexible material deforms elastically, thereby ensuring the stability of tension in multiple dimensions;

[0020] (4) The present invention can assess the air tightness of the flexible thermal insulation material by applying a set gas pressure through the vent hole at the center of the dimensional support. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the exploded diagram of the test structure;

[0022] Figure 2 The cross-section diagram of the test structure connection is shown;

[0023] Figure 3 This is the flow chart of the assessment test.

[0024] Figure numbers: 1-rectangular nozzle, 2-transition section, 2-2-smooth transition groove, 3-1-dimensional thermal insulation inner support, 3-2-external support frame, 3-3-vent, 4-flexible heat protection material. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0026] A free jet test device for flexible thermal insulation materials under arc wind tunnel conditions comprises a rectangular nozzle 1, a transition section 2, and a support frame, wherein the support frame comprises a dimensional thermal insulation inner support 3-1 and an outer support frame 3-2, such as Figure 1 and Figure 2 shown.

[0027] The transition section 2 is tightly connected to the rectangular nozzle 1, and the inner surface has a smooth transition without steps. The transition section has a built-in water cooling channel, which can pass cooling water to prevent damage by high-temperature and high-speed airflow. The flexible heat-proof material 4 is a rectangular material with a thickness of about 10 mm, a length of about 700 mm, and a width of about 260 mm. Both ends in the length direction are connected to the front and rear side walls of the outer support frame 3-2. The dimensional insulation inner support 3-1 is located in the cavity of the outer support frame 3-2 and can move vertically along the cavity direction (the cross-section of the inner cavity of the outer support frame 3-2 is rectangular, and the dimensional insulation inner support 3-1 is pushed by an external pushing mechanism and can slide in the inner cavity of the outer support frame 3-2). The flexible heat-proof material 4 is stretched open by vertical upward movement and a certain tension is maintained. The model composed of the flexible heat-proof material 4, the dimensional insulation inner support 3-1 and the outer support frame 3-2 is connected to the transition section to form a test whole.

[0028] The rectangular nozzle 1 is a Laval nozzle, and the typical outlet size is 120 mm × 60 mm. It can accelerate the high-temperature and high-pressure airflow from the arc heater into a high-temperature and high-speed airflow, and flush the surface of the flexible heat-resistant material 4 to achieve the test effect.

[0029] One end of the transition section 2 is tightly connected to the rectangular nozzle 1, and a rectangular channel is opened inside to smoothly transition with the rectangular nozzle 1. At the same time, a smooth transition groove 2-2 is set at the other end, which works together with the dimensional insulation inner support 3-1 to fix the flexible heat-proof material at the nozzle outlet. A water cooling channel is set inside for water cooling.

[0030] The dimensional heat-insulating inner support 3-1 is made of heat-insulating and heat-resistant materials, such as fiberglass, high silica or foam ceramics, and has certain strength and heat-resistant and heat-insulating properties. It can support flexible materials without destroying the heat transfer characteristics of flexible materials.

[0031] The internal cavity of the outer support frame 3-2 can limit the dimensional insulation inner support 3-1 to move only in the vertical direction. At the same time, fixing holes are set on the front and rear end faces to fix the flexible heat-proof material 4. In addition, a variety of fixing methods are also set at the bottom, which can connect the flexible heat-proof material 4, the dimensional insulation inner support 3-1 and the outer support frame 3-2 that constitute the whole to the transition section 2.

[0032] The flexible material 4 is formed by sewing multiple layers of heat-insulating cloth, and thermocouples are arranged inside to measure the temperature change of each layer.

[0033] like Figure 3 As shown, a free jet test method for flexible thermal insulation materials under arc wind tunnel conditions includes: first, selecting the test shape and test conditions according to the location where the flexible thermal insulation material 4 is used and the thermal environment faced by the location, then installing the flexible thermal insulation material 4 on a support frame, pulling the flexible thermal insulation material through an external push device to generate a specific tension and maintain a stable tension during the action of high-temperature and high-speed airflow, starting the arc wind tunnel, gradually increasing the operating power until the set test environment is reached, and the high-temperature and high-speed airflow heated by the arc heater and accelerated by the Lava nozzle has a thermal and force action relationship with the flexible thermal insulation material 4, obtaining the temperature change process of the outer surface of the flexible thermal insulation material 4 through an infrared thermometer, obtaining the temperature inside the flexible thermal insulation material 4 through the temperature measuring points between the layers, and then evaluating the thermal insulation performance of the flexible thermal insulation material 4. After the test is completed, the arc wind tunnel operation is stopped, the next test model and state are replaced, and the data are summarized and analyzed after all tests are completed.

[0034] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0035] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A free jet test device for flexible thermal insulation materials under arc wind tunnel conditions, characterized in that: It includes a rectangular nozzle, a transition section, and a support frame, wherein the support frame includes a dimensional heat-insulating inner support and an outer support frame; The transition section is tightly connected to the rectangular nozzle, the inner surface has a smooth transition without steps, and the transition section has a built-in water cooling channel; The two ends of the tested flexible heat-proof material along the jet direction are connected to the front and rear side walls of the outer support frame. The dimensional insulation inner support is located in the cavity of the outer support frame. The flexible heat-proof material is stretched out in the vertical direction and a certain tension is maintained. The model consisting of the flexible heat-proof material, the dimensional insulation inner support and the outer support frame is connected to the transition section to form a test whole.

2. The flexible thermal insulation material free jet test device according to claim 1 is characterized in that: The dimensional heat-insulating inner support can slide in the cavity of the outer support frame through an external pushing mechanism.

3. The flexible thermal insulation material free jet test device according to claim 1 is characterized in that: The rectangular nozzle is a Laval nozzle.

4. The flexible thermal insulation material free jet test device according to claim 1 is characterized in that: One end of the transition section is tightly connected to the rectangular nozzle, and a rectangular channel is opened inside to smoothly transition to the rectangular nozzle. At the same time, a smooth transition groove is set at the other end, which works together with the dimensional insulation inner support to fix the flexible heat-proof material at the nozzle outlet.

5. The flexible thermal insulation material free jet test device according to claim 1 is characterized in that: The dimensional heat-insulating inner support is made of heat-insulating and heat-resistant materials.

6. The flexible thermal insulation material free jet test device according to claim 1 is characterized in that: The flexible material is made of multiple layers of heat-insulating cloth sewn together, with thermocouples arranged inside to measure the temperature changes of each layer.

7. The flexible thermal insulation material free jet test device according to claim 1 is characterized in that: Ventilation holes are arranged on the dimensional heat-insulating inner support.

8. A test method based on the flexible thermal insulation material free jet assessment test device according to claim 1, characterized in that: include: Firstly, the assessment shape and test conditions are selected according to the application site of the flexible thermal insulation material and the thermal environment faced by this site. Then, the flexible thermal insulation material is installed on the support frame. The flexible thermal insulation material is pulled by an external pushing device to generate a specific tension and maintain a stable tension during the action of high-temperature and high-speed airflow. The arc wind tunnel is started, and the operating power is gradually increased until the set assessment environment is reached. The high-temperature and high-speed airflow heated by the arc heater and accelerated by the rectangular nozzle interacts with the flexible thermal insulation material in terms of heat and force. The temperature change process of the outer surface of the flexible thermal insulation material is obtained by an infrared thermometer, and the temperature inside the flexible thermal insulation material is obtained by the temperature measuring points between the layers, thereby evaluating the thermal insulation performance of the flexible thermal insulation material.

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