Low-temperature icing dual-mode wind tunnel implementation method and system

Abstract

The application relates to the technical field of aerodynamic experiment equipment, in particular to a low-temperature icing double-mode wind tunnel implementation method and system, which can solve the problem that the existing icing wind tunnel sets a cooling plate provided with a coolant pipeline in an air flow loop, the cooling plate forms great air flow resistance, great power loss is caused, and the construction cost and operation cost are both very high. The method comprises the following steps: a return flow type wind tunnel is adopted, liquid nitrogen is sprayed on test gas in a spraying manner to reduce and control the temperature of the test gas, and the moisture in the humid test gas can be condensed into liquid drops for icing test; a low-temperature wind tunnel and an icing wind tunnel share a liquid nitrogen cooling system, the wind tunnel is switched between the low-temperature wind tunnel mode and the icing wind tunnel mode, different wind tunnel test work is carried out, so that the wind tunnel can complete the low-temperature wind tunnel and icing wind tunnel work in different operation modes, and the test parameter range of the low-temperature wind tunnel and the icing wind tunnel can be expanded.

Description

Technical Field

[0001] This application relates to the field of aerodynamic experimental equipment technology, and more specifically, to a method and system for realizing a low-temperature icing dual-mode wind tunnel. Background Technology

[0002] A wind tunnel is an aerodynamic testing device proposed by the Englishman Wenham in the 19th century. Its key feature is that it blows a stable airflow through a test model in a duct, allowing for observation of the forces acting on the model and the surrounding flow field. Because the airflow provided by a wind tunnel is relatively stable, it gradually replaced cantilever cranes as the mainstream equipment for ground-based aerodynamic testing.

[0003] With the rapid development of aerospace technology, the range of test parameters for wind tunnels is constantly expanding, and various types of wind tunnel designs are emerging. In the early stages of wind tunnel development, wind tunnels were mainly used to study the changes in the lift drag characteristics of airfoils. The wind tunnels designed at that time were relatively small, mainly aiming to obtain aerodynamic data on small-scale models and then map it to actual-sized aircraft using similarity laws. For example, the wind tunnel built by the Wright brothers in the United States could only test wingspans of about 10 cm. Later, Prandtl in Germany built a full-scale wind tunnel for aircraft aerodynamic research and corrected the erroneous results caused by the scale effect of small-scale wind tunnels.

[0004] Wind tunnels are broadly classified into two types: direct-flow (DC) and recirculation (ROC). A DC wind tunnel consists of a test section within a long, straight duct, where the test model is installed. Fans are then added upstream or downstream of this section, creating a blowing or sucking wind tunnel. In transonic or supersonic wind tunnels with higher airflow velocities, gas tanks or vacuum tanks can be used instead of fans to blow higher-energy airflow over the model for testing. The advantages of DC wind tunnels are their simple structure and easy airflow control, making them the most popular design type in the early days of wind tunnel technology. However, because the airflow in a DC wind tunnel passes through a diffuser section and is then expelled into the surrounding atmosphere after passing over the model, its main disadvantage is significant energy loss. This loss is tolerable for small-sized wind tunnels, but for large-sized wind tunnels, it necessitates a substantial increase in operating power, ultimately leading to a significant increase in operating costs. Furthermore, the exhaust air from DC wind tunnels has a relatively large environmental impact.

[0005] Because of these drawbacks of direct-flow wind tunnels, recirculating wind tunnels were developed. As the name suggests, the basic characteristic of a recirculating wind tunnel is the use of a ring-shaped duct as its main structure. The airflow passing through the test model passes through the ring-shaped duct and is rectified before re-entering the test section, thus greatly reducing energy loss and environmental impact. For wind tunnel tests requiring controlled airflow temperature and humidity, the advantages of recirculating wind tunnels are even more pronounced. Recirculating wind tunnels typically have four turns, and the airflow needs to be rectified by guide vanes when passing through these turns. Therefore, their structure is more complex than that of direct-flow wind tunnels. However, due to the advantages mentioned above, recirculating wind tunnels have gradually become the main design type for subsonic and transonic wind tunnels.

[0006] Early wind tunnels simulated airflow environments near the ground. Therefore, as long as the airflow was smooth enough and met the turbulence requirements, it could be used for aerodynamic testing. The emergence of recirculation wind tunnels made the airflow environment inside the wind tunnel relatively independent of the laboratory environment. This provided a possibility to obtain an airflow environment different from the ground environment by controlling the airflow parameters inside the wind tunnel. At the same time, it is easy to know from the definition of Reynolds number that changing parameters such as airflow temperature, density, viscosity and pressure can significantly increase the test range of wind tunnel Reynolds number, thereby simulating the aerodynamic characteristics of the test model in a larger parameter space. This led to the development of cryogenic wind tunnel design.

[0007] Cryogenic wind tunnels primarily lower the temperature of the test airflow by spraying cryogenic nitrogen gas or directly spraying liquid nitrogen into it. As the airflow temperature decreases, its viscosity decreases and its density increases, leading to a significant increase in the Reynolds number and thus expanding the range of test Reynolds numbers.

[0008] Besides flight under normal weather conditions, aircraft design also needs to consider changes in flight performance under special weather conditions. Among various weather conditions, icing has the greatest impact on flight safety, and changes in flight performance under icing conditions are one of the main subjects of civil aircraft airworthiness verification. Therefore, icing wind tunnels, which can be used to study aircraft icing, have reappeared in the category of special wind tunnel design. Unlike low-temperature wind tunnels that control airflow temperature, typical icing wind tunnels use Freon to reduce airflow temperature. Similar to household air conditioners, existing icing wind tunnels also have multiple cooling plates installed inside to reduce airflow temperature. Freon pipes are arranged on the cooling plates. When the airflow passes over the cooling plates, the airflow temperature drops to icing conditions, and then atomized water droplets are sprayed from the water spray pipes. The water droplets freeze on the model, ultimately completing the entire test process.

[0009] The biggest drawback of existing icing wind tunnel designs is that the cooling plate is placed in the wind tunnel loop, which creates a lot of airflow resistance and causes a lot of power loss. Summary of the Invention

[0010] To address the major drawback of existing icing wind tunnel designs—that the cooling plate is placed in the wind tunnel loop, creating significant airflow resistance and resulting in substantial power loss—this application provides a method and system for implementing a low-temperature icing dual-mode wind tunnel.

[0011] The embodiments of this application are implemented as follows:

[0012] Firstly, this application provides a method for implementing a low-temperature icing dual-mode wind tunnel, including:

[0013] A recirculating wind tunnel is used to reduce and control the temperature of the test gas by spraying liquid nitrogen into it, and it can also condense the moisture in the humid test gas into droplets for icing tests.

[0014] The low-temperature wind tunnel and the icing wind tunnel share a liquid nitrogen cooling system, allowing the wind tunnel to switch between low-temperature wind tunnel mode and icing wind tunnel mode to conduct different wind tunnel tests. This enables the wind tunnel to perform the work of both low-temperature and icing wind tunnels under different operating modes.

[0015] In one possible implementation, the method further includes adjusting the humidity of the test gas by adding dry steam to the test gas.

[0016] In one possible implementation, the method further includes: the surface temperature of the test model is adjustable to simulate changes in the icing morphology of the model under different environments.

[0017] In one possible implementation, the method further includes: injecting larger-scale droplets into the test airflow via droplet atomization upstream of the test section to adjust the droplet size distribution to make it closer to the size distribution in the real atmospheric environment.

[0018] In one possible implementation, the method further includes: removing excess water vapor downstream of the test section to reduce water vapor corrosion of the tunnel walls.

[0019] Secondly, this application provides a low-temperature icing dual-mode wind tunnel system, the system comprising: a recirculation low-temperature wind tunnel, a liquid nitrogen cooling system, and a direct-cooling icing test module, wherein the liquid nitrogen cooling system and the direct-cooling icing test module are both installed in the recirculation low-temperature wind tunnel;

[0020] The direct-cooling icing test module includes a dry steam humidity regulating device, an atomizing spray device, and a testing system, the testing system being used for icing tests.

[0021] In one possible implementation, the system further includes: the dry steam humidity regulating device is installed upstream of the recirculation low-temperature wind tunnel test section, and the humidity of the test gas is adjusted by adding dry steam to the test gas.

[0022] In one possible implementation, the system further includes: the atomizing spray device is installed upstream of the recirculating low-temperature wind tunnel, and water vapor is injected into the test airflow using a droplet atomization method.

[0023] In one possible implementation, the system further includes a surface temperature regulating device disposed inside the experimental model;

[0024] The surface temperature regulating device includes a cooling pipe and a resistance wire installed inside the test model. The cooling pipe is used to introduce low-temperature nitrogen gas into the model to cool the surface temperature of the model, and the resistance wire is used to heat the surface of the model.

[0025] In one possible implementation, the system further includes a water vapor removal device located downstream of the test section;

[0026] The water vapor removal system includes a guide vane, a water vapor collection net, and a guide channel. The guide vane and the water vapor collection net can collect water vapor in the airflow and discharge it from the wind tunnel through the guide channel. In addition, a resistance wire is embedded inside the leading edge of the guide vane to prevent secondary icing.

[0027] The technical solution provided in this application can achieve at least the following beneficial effects:

[0028] This application provides a method and system for implementing a dual-mode wind tunnel for low-temperature icing. The "direct-cooling icing wind tunnel" used in this application can inject liquid nitrogen or low-temperature nitrogen gas into the wind tunnel to obtain the low-temperature airflow conditions required for icing tests. Furthermore, water in the humidified test airflow is condensed into water mist for icing tests. By combining the design of a low-temperature wind tunnel with that of a direct-cooling icing wind tunnel, the wind tunnel can operate in both low-temperature and icing modes, greatly expanding its operational range and achieving higher returns with a given construction cost. In particular, by adjusting the internal temperature and pressure of the wind tunnel, high-altitude aircraft icing simulation can be achieved. Simultaneously, an environment close to naturally formed clouds and fog can be created within the wind tunnel, enabling wind tunnel simulations related to cloud physics. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The background section shows a schematic diagram of the structure of a low-temperature wind tunnel;

[0031] Figure 2 The background section shows a schematic diagram of the structure of a "direct-cooling" icing wind tunnel;

[0032] Figure 3 This is a schematic diagram of another low-temperature icing dual-mode wind tunnel as illustrated in an exemplary embodiment of this application.

[0033] Figure label:

[0034] 1. Test section; 2. Model; 3. First diffusion section; 4. First corner; 5. Guide vane; 6. Drain outlet; 7. Liquid nitrogen injection port; 8. Second corner; 9. Fan; 10. Second diffusion section; 11. Third corner; 12. Exhaust port; 13. Dry steam injection port; 14. Fourth corner; 15. Honeycomb unit; 16. Second liquid nitrogen injection port; 17. Ultrasonic water mist injection port; 18. Contraction section. Detailed Implementation

[0035] To make the objectives, implementation methods and advantages of this application clearer, the exemplary implementation methods of this application will be clearly and completely described below with reference to the accompanying drawings of the exemplary embodiments of this application. Obviously, the exemplary embodiments described are only some embodiments of this application, and not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0036] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0037] The terms "first," "second," "third," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar or related objects or entities, and do not necessarily imply a specific order or sequence, unless otherwise specified. It should be understood that such terms are interchangeable where appropriate.

[0038] The terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclude inclusion, for example, a product or device that includes a range of components is not necessarily limited to all of the components that are clearly listed, but may include other components that are not clearly listed or that are inherent to such product or device.

[0039] To facilitate the explanation of the technical solution of this application, some concepts involved in this application will be explained first below.

[0040] A wind tunnel is an aerodynamic testing device proposed by the British Frank H. Wenham in the 19th century. Its characteristic is that a stable airflow is blown through a test model in a tube, thereby completing the observation of the stress on the model and the surrounding flow field. Because the airflow quality provided by the wind tunnel is relatively stable, it gradually replaced the cantilever machine and became the mainstream equipment for ground aerodynamic testing.

[0041] Before explaining the low-temperature icing dual-mode wind tunnel implementation method and system provided in the embodiments of this application, the application scenarios and implementation environment of the embodiments of this application will be introduced first.

[0042] With the rapid development of aerospace technology, the range of test parameters for wind tunnels is constantly expanding, and various types of wind tunnel designs are emerging. In the early stages of wind tunnel development, wind tunnels were mainly used to study the changes in the lift drag characteristics of airfoils. The wind tunnels designed at that time were relatively small, mainly to obtain aerodynamic data on small-scale models and then map it to actual-sized aircraft using similarity laws. For example, the wind tunnel built by the Wright brothers in the United States could only test wingspans of about 10 cm. Later, Prandtl in Germany built a full-scale wind tunnel for aircraft aerodynamic research and made up for the errors caused by the scale effect of small-scale wind tunnels.

[0043] Figure 1 The background section shows a schematic diagram of the structure of a low-temperature wind tunnel. Figure 2 The background section shows a schematic diagram of the structure of a "direct cooling" icing wind tunnel.

[0044] Wind tunnels are broadly classified into two types: direct-flow and recirculation wind tunnels. A direct-flow wind tunnel consists of a test section within a long, straight pipe where the test model is installed. Fans are then added upstream or downstream of this test section, creating a blowing or sucking wind tunnel. In transonic or supersonic wind tunnels with higher airflow velocities, air tanks or vacuum tubes can be used instead of fans to blow higher-energy airflow over the model for testing. The advantages of direct-flow wind tunnels are their simple structure and easy airflow control, making them the most popular design type in the early days of wind tunnel technology. However, because the airflow in a direct-flow wind tunnel passes through a diffuser section and is then blown into the surrounding atmosphere, its main disadvantage is significant energy loss. This loss is tolerable for small-sized wind tunnels, but for large-sized wind tunnels, it necessitates a substantial increase in operating power, ultimately leading to a significant increase in operating costs. Furthermore, the exhaust airflow from a direct-flow wind tunnel has a relatively large environmental impact.

[0045] Because of these drawbacks of direct-flow wind tunnels, recirculating wind tunnels were developed. As the name suggests, the basic characteristic of a recirculating wind tunnel is that it uses a ring-shaped duct as the main structure. The airflow passing through the test model is rectified and then re-enters the test section, thus greatly reducing energy loss and environmental impact. For wind tunnel tests requiring controlled airflow temperature and humidity, the advantages of recirculating wind tunnels are even more pronounced. Figure 1 As shown, recirculating wind tunnels typically have four corners. When the airflow passes through the corners, it needs to be rectified by guide vanes. Therefore, the structure is more complex than that of a direct-flow wind tunnel. However, due to the advantages mentioned above, recirculating wind tunnels have gradually become the main design type for subsonic and transonic wind tunnels.

[0046] Early wind tunnels simulated airflow environments near the ground. Therefore, as long as the airflow was smooth enough and met the turbulence requirements, it could be used for aerodynamic testing. The emergence of recirculation wind tunnels made the airflow environment inside the wind tunnel relatively independent of the laboratory environment. This provided a possibility to obtain an airflow environment different from the ground environment by controlling the airflow parameters inside the wind tunnel. At the same time, it is easy to know from the definition of Reynolds number that changing parameters such as airflow temperature, density and pressure can significantly increase the test range of wind tunnel Reynolds number, thereby understanding the aerodynamic characteristics of the test model in a larger parameter space. This led to the development of cryogenic wind tunnel design.

[0047] Cryogenic wind tunnels primarily reduce the temperature of the test airflow by spraying cryogenic nitrogen or directly spraying liquid nitrogen. As the airflow temperature decreases, its viscosity also decreases, leading to a significant increase in the Reynolds number and thus expanding the range of test Reynolds numbers. Besides flight under normal weather conditions, aircraft design must also consider changes in flight performance under special weather conditions. Among various weather conditions, icing environments have the greatest impact on flight safety, and changes in flight performance under icing conditions are a major subject in civil aircraft airworthiness verification. Therefore, icing wind tunnels, used to study aircraft icing, have emerged as a category of special wind tunnel designs. Unlike cryogenic wind tunnels that control airflow temperature, typical icing wind tunnels utilize Freon to reduce airflow temperature. Similar to household air conditioners, icing wind tunnels also have multiple cooling plates installed inside to lower the airflow temperature. Freon pipes are arranged on these cooling plates. When the airflow passes over the cooling plates, its temperature drops to icing conditions. Then, atomized water droplets are sprayed from the water spray pipes, freezing on the model and ultimately completing the entire test process.

[0048] However, the biggest drawback of the existing icing wind tunnel design is that the cooling plate is placed in the wind tunnel loop, which creates a lot of airflow resistance and causes a lot of power loss. Therefore, since NASA built the Icing Research Tunnel (IRT) in the 1940s, it has carried out two major redesigns of the cooling device, but the overall design concept has not changed.

[0049] Based on this, this application provides a method and system for implementing a low-temperature icing dual-mode wind tunnel, employing a "direct-cooling icing wind tunnel" design, such as... Figure 2 As shown, rapidly cooling the test airflow by injecting cryogenic nitrogen gas, while simultaneously condensing the moisture in the humid air into droplets for icing tests, is a novel approach in icing wind tunnel design. This approach uses a cryogenic nitrogen nozzle array instead of cooling plates, which can significantly reduce power loss in wind tunnel tests. Moreover, due to its relatively simple structure, it is suitable for building new icing wind tunnels at a lower cost, and can also be used to convert existing wind tunnels into icing wind tunnels. Its construction and operating costs are far lower than those of existing icing wind tunnels. Furthermore, combining icing tests with cryogenic wind tunnel tests, utilizing their commonalities, can greatly expand the testing range of the wind tunnel, thereby improving its utilization efficiency.

[0050] Next, the technical solutions of this application and how they solve the aforementioned technical problems will be described in detail through embodiments and in conjunction with the accompanying drawings. The embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application.

[0051] The design principle of low-temperature icing dual-mode wind tunnels is the same, but their specific implementation methods can be divided according to the range of Mach numbers that the wind tunnel can simulate, such as low-speed dual-mode wind tunnels, subsonic dual-mode wind tunnels, and transonic dual-mode wind tunnels, etc.

[0052] Structurally, wind tunnels can be divided into two types: horizontal and vertical. A horizontal wind tunnel is one where the axis of the test section is parallel to the horizontal plane, which is the most common type used in wind tunnels. A vertical wind tunnel, on the other hand, is one where the axis of the test section is perpendicular to the horizontal plane. Horizontal wind tunnels have better structural stability, lower requirements for wind tunnel infrastructure, and are easier to install and arrange measurement and control systems. Vertical wind tunnels, however, have lower stability and require additional support structures to ensure stability during operation. The advantage of vertical wind tunnels is that there is no deviation in the droplet trajectory due to gravity during icing tests. Therefore, in the actual design and construction process, various design constraints must be comprehensively considered when making a choice.

[0053] Figure 3This is a schematic diagram of another low-temperature icing dual-mode wind tunnel as illustrated in an exemplary embodiment of this application.

[0054] In one exemplary embodiment, such as Figure 3 As shown, a method for implementing a low-temperature icing dual-mode wind tunnel is provided. In this embodiment, the method may include:

[0055] A recirculating wind tunnel is used to reduce and control the temperature of the test gas by spraying liquid nitrogen into it, and it can also condense the moisture in the humid test gas into droplets for icing tests.

[0056] The low-temperature wind tunnel and the icing wind tunnel share a liquid nitrogen cooling system, allowing the wind tunnel to switch between low-temperature wind tunnel mode and icing wind tunnel mode to conduct different wind tunnel tests. This enables the wind tunnel to perform the work of both low-temperature and icing wind tunnels under different operating modes.

[0057] As can be seen, compared with traditional icing wind tunnels, the low-temperature icing dual-mode wind tunnel proposed in this application can simulate the icing process in high-altitude environments and the condensation phenomenon in still airflow, while also simulating atmospheric physical phenomena such as clouds and fog.

[0058] In one possible implementation, the method further includes adjusting the humidity of the test gas by adding dry steam to the test gas.

[0059] The dry steam system includes a dry steam generator and a piping and nozzle system for introducing dry steam into the wind tunnel. When the humidity of the test gas is not saturated, the dry steam system can be used to increase the humidity of the test gas flow, but the humidity must be controlled below the saturation level to prevent premature water mist precipitation.

[0060] In one possible implementation, the method further includes: the surface temperature of the test model is adjustable to simulate changes in the icing morphology of the model under different environments.

[0061] This process involves vaporizing liquid nitrogen into cryogenic nitrogen gas, which is then introduced into the model's piping network via a pipeline system. This reduces the model's surface temperature. Theoretically, the pre-laid piping network in the model needs to be designed based on the actual temperature distribution of the airfoil surface to ensure that the actual airfoil surface temperature distribution can be reproduced after the cryogenic nitrogen gas is introduced. An electric heating device can also be embedded inside the airfoil's leading edge to simulate the operation of the aircraft's anti-icing and de-icing system, simulating the temperature changes on the airfoil surface after the anti-icing and de-icing system is activated.

[0062] In one possible implementation, the method further includes: injecting larger-scale droplets into the test airflow via droplet atomization upstream of the test section to adjust the droplet size distribution to make it closer to the size distribution in the real atmospheric environment.

[0063] In one possible implementation, the method further includes: removing excess water vapor downstream of the test section to reduce water vapor corrosion of the tunnel walls.

[0064] The drainage system is generally located downstream of the test section near the first bend. Here, the test airflow carrying water mist collides with the guide vanes and the wind tunnel walls and bottom plate, and is separated from the airflow and accumulates on the wind tunnel walls and bottom. The separated water can be directed into the collection box or directly discharged from the wind tunnel by opening holes or slots in the wind tunnel bottom plate.

[0065] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially as indicated, these steps are not necessarily executed in the indicated order. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0066] Corresponding to the aforementioned embodiment of a low-temperature icing dual-mode wind tunnel implementation method, this application also provides an embodiment of a low-temperature icing dual-mode wind tunnel system.

[0067] In one exemplary embodiment, such as Figure 3 As shown, the low-temperature icing dual-mode wind tunnel system includes: a recirculation low-temperature wind tunnel, a liquid nitrogen cooling system, and a direct-cooling icing test module. The liquid nitrogen cooling system and the direct-cooling icing test module are both installed in the recirculation low-temperature wind tunnel.

[0068] The direct-cooling icing test module includes a dry steam humidity regulating device, an atomizing spray device, and a testing system, the testing system being used for icing tests.

[0069] The low-temperature icing dual-mode wind tunnel proposed in this application can be seen as adding a direct-cooling icing test module to the traditional low-temperature wind tunnel design. This mainly involves adding a dry steam humidity control system and an atomizing spray device, as well as a testing system for icing tests. From a physical perspective, low-temperature wind tunnels primarily use dry air for testing, while direct-cooling icing wind tunnels use humid air. Combining the two adds a water vapor circulation to the original airflow and cooling circulation of the low-temperature wind tunnel. This means that to regulate the humidity of the test gas, water vapor needs to be added to the test gas upstream of the test section, and excess water vapor needs to be removed downstream of the test section. Simultaneously, the corrosive effect of water vapor on the tunnel walls must be considered.

[0070] In one possible implementation, such as Figure 3 As shown, the system further includes: the dry steam humidity regulating device is installed in the test section of the recirculation low-temperature wind tunnel, and the humidity of the test gas is adjusted by adding dry steam into the test gas.

[0071] In one possible implementation, such as Figure 3 As shown, the system further includes: the atomizing spray device is installed upstream of the recirculating low-temperature wind tunnel, and water vapor is injected into the test airflow by droplet atomization.

[0072] In one possible implementation, such as Figure 3 As shown, the system also includes a surface temperature regulating device installed inside the experimental model;

[0073] The surface temperature regulating device includes a cooling pipe and a resistance wire installed inside the test model. The cooling pipe is used to introduce low-temperature nitrogen gas into the model to cool the surface temperature of the model, and the resistance wire is used to heat the surface of the model.

[0074] In one possible implementation, such as Figure 3 As shown, the system also includes a water vapor removal device installed downstream of the test section;

[0075] The water vapor removal device includes a guide vane, a water vapor collection net, and a guide channel. The guide vane and the water vapor collection net can collect water vapor in the airflow and discharge it from the wind tunnel through the guide channel. In addition, a resistance wire is embedded inside the leading edge of the guide vane to prevent secondary icing.

[0076] For specific limitations regarding the low-temperature icing dual-mode wind tunnel system, please refer to the limitations of a low-temperature icing dual-mode wind tunnel implementation method and system mentioned above, which will not be repeated here.

[0077] Test Procedure: The low-temperature icing dual-mode wind tunnel provided in some embodiments of this application can be operated in low-temperature wind tunnel mode and icing wind tunnel mode, respectively, and their operation processes are as follows:

[0078] (1) As Figure 3 As shown, when operating in low-temperature wind tunnel mode, only the liquid nitrogen injection port for reducing the temperature of the test airflow inside the wind tunnel and the exhaust port of the heated airflow are opened, while the dry steam injection port, the secondary liquid nitrogen injection port, and the ultrasonic water mist injection port for icing tests are closed. At this time, the wind tunnel is in low-temperature wind tunnel mode.

[0079] (2) Figure 3 As shown, when operating in icing mode, the liquid nitrogen injection port, exhaust port, dry steam injection port, secondary liquid nitrogen injection port, and ultrasonic water mist main inlet are opened simultaneously, and the drain port is also opened. At this time, the wind tunnel is in icing wind tunnel mode.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for implementing a low-temperature icing dual-mode wind tunnel, characterized in that, The method includes: A recirculation wind tunnel is adopted, which sprays liquid nitrogen into the test gas through the liquid nitrogen injection port to reduce and control the temperature of the test gas, and can condense the moisture in the humid test gas into droplets for icing tests. The recirculation wind tunnel includes a liquid nitrogen injection port and an exhaust port on the loop, a dry steam injection port, a secondary liquid nitrogen injection port and an ultrasonic water mist injection port on the upstream of the test section, and a drainage port on the downstream of the test section near the first corner. When operating in low-temperature wind tunnel mode, open the liquid nitrogen injection port to reduce the temperature of the test airflow inside the wind tunnel and the exhaust port of the heated airflow, and close the dry steam injection port, the secondary liquid nitrogen injection port and the ultrasonic water mist injection port used for icing tests. At this time, the wind tunnel is a low-temperature wind tunnel. When operating in icing mode, the liquid nitrogen injection port, exhaust port, dry steam injection port, secondary liquid nitrogen injection port, and ultrasonic water mist injection port are opened simultaneously, and the drain port is also opened. At this time, the wind tunnel is an icing wind tunnel. The low-temperature wind tunnel and the icing wind tunnel share a liquid nitrogen cooling system, allowing the wind tunnel to switch between low-temperature wind tunnel mode and icing wind tunnel mode to carry out different wind tunnel tests. This enables the wind tunnel to complete the work of low-temperature wind tunnel and icing wind tunnel in different operating modes. The humidity of the test gas is adjusted by adding dry steam into the test gas through a dry steam injection port. Water vapor is injected into the test airflow through an ultrasonic water mist injection port in the form of droplet atomization, and excess water vapor is discharged through a drain outlet downstream of the test section. The surface temperature of the experimental model is adjustable to simulate the changes in the icing morphology of the model under different environments.

2. The method for implementing a low-temperature icing dual-mode wind tunnel as described in claim 1, characterized in that, The method further includes: injecting larger-scale droplets into the test airflow upstream of the test section using droplet atomization to adjust the droplet size distribution to make it closer to the size distribution in the real atmospheric environment.

3. A low-temperature icing dual-mode wind tunnel system, applied to the method described in any one of claims 1-2, characterized in that, include: The system includes a recirculation-type cryogenic wind tunnel, a liquid nitrogen cooling system, and a direct-cooling icing test module, both of which are installed in the recirculation-type cryogenic wind tunnel. The direct-cooling icing test module includes a dry steam humidity regulating device, an atomizing spray device, and a testing system, the testing system being used for icing tests.

4. The low-temperature icing dual-mode wind tunnel system as described in claim 3, characterized in that, The system further includes: the dry steam humidity regulating device is installed upstream of the recirculation low-temperature wind tunnel test section, and the humidity of the test gas is adjusted by adding dry steam to the test gas.

5. A low-temperature icing dual-mode wind tunnel system as described in claim 3, characterized in that, The system further includes: the atomizing spray device is installed upstream of the recirculating low-temperature wind tunnel test section, and water vapor is injected into the test airflow by droplet atomization.

6. The low-temperature icing dual-mode wind tunnel system as described in claim 3, characterized in that, The system also includes a surface temperature regulating device installed inside the experimental model; The surface temperature regulating device includes a cooling pipe and a resistance wire installed inside the test model. The cooling pipe is used to introduce low-temperature nitrogen gas into the model to cool the surface temperature of the model, and the resistance wire is used to heat the surface of the model.

7. A low-temperature icing dual-mode wind tunnel system as described in claim 3, characterized in that, The system also includes a water vapor removal device installed downstream of the test section; The water vapor removal device includes a guide vane, a water vapor collection net, and a guide channel. The guide vane and the water vapor collection net can collect water vapor in the airflow and discharge it from the wind tunnel through the guide channel. In addition, a resistance wire is embedded inside the leading edge of the guide vane to prevent secondary icing.

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