A heater for a high Reynolds number hypersonic wind tunnel

Abstract

The application belongs to the field of hypersonic wind tunnel test equipment, and discloses a heater for a high Reynolds number hypersonic wind tunnel. The heater is a tank body, and sequentially comprises a lower plug, a winding cylinder body and an upper plug from bottom to top. The lower plug is provided with an air inlet, and the upper plug is provided with an air outlet. The inner diameters of the air inlet and the air outlet are equal. The winding cylinder body is sleeved with a winding frame. The inner wall of the winding cylinder body is covered with a heat shield, and the inner wall of the heat shield is uniformly distributed with heating elements. The lower part of the winding cylinder body is suspendedly fixed with a cold gas flow guide table, and the gap between the lower surface of the cold gas flow guide table and the bottom surface of the winding cylinder body forms a uniform flow cavity. The heater adopts a gas piston driving operation mode in which superhigh pressure cold gas drives superhigh temperature and superhigh pressure hot gas, so as to maintain the total temperature and total pressure of the hot gas at the air outlet of the heater constant, fully utilize the superhigh temperature and superhigh pressure hot gas in the heater, and enable the effective operation time of the high Reynolds number hypersonic wind tunnel to be 1 second to several tens of seconds.

Description

Technical Field

[0001] This invention belongs to the field of hypersonic wind tunnel testing equipment, specifically relating to a heater for high Reynolds number hypersonic wind tunnels. Background Technology

[0002] Conventional hypersonic wind tunnels typically use air as the test medium, with a maximum operating Mach number of 10, a maximum total air pressure of 12 MPa, and a maximum total air temperature of 1082 K. The Reynolds number in these tunnels is relatively low. Due to the high gas velocity, reaching Mach numbers of 5 to 10, the gas expands violently through the nozzle, causing water vapor and carbon dioxide to condense, resulting in flow field inhomogeneities and inaccurate test data—unacceptable in hypersonic wind tunnel aerodynamic testing. Therefore, heaters are required in hypersonic wind tunnels using high-speed air as the medium to heat the gas to the necessary anti-condensation temperature. Heaters used in conventional hypersonic wind tunnels are generally of two types: direct-heating heaters and regenerative heaters. Direct-heating heaters achieve gas heating through direct heat exchange between the gas and a metal resistance band or wire; they consist of a metal heating element (resistance band or wire), a heat insulation layer, and a single-piece forged pressure-bearing shell. Regenerative heaters preheat an internal heat storage body using metal heating elements, then the airflow exchanges heat with the heat storage body to achieve airflow heating. A regenerative heater consists of metal heating elements (armored heating tubes), a metal heat storage body or a pebble bed heat storage body, an insulation layer, and an integral forged pressure-bearing shell. Both the direct-heating and regenerative heaters described above have a maximum operating total temperature below 1373K and a maximum total pressure below tens of megapascals, which can meet the airflow heating requirements of conventional hypersonic wind tunnel tests.

[0003] Because high Reynolds number hypersonic wind tunnels can simultaneously simulate high Reynolds numbers and high Mach numbers, operating at Mach numbers far greater than 10, with a maximum total airflow pressure of 200 MPa and a maximum total airflow temperature of 2300 K, the wind tunnel has a high Reynolds number. To meet the heating requirements of the test airflow and the wind tunnel's operational specifications, the heater needs to meet the following requirements:

[0004] 1. The heater needs to have a maximum operating total pressure of 200MPa and a maximum operating temperature of 2300K;

[0005] 2. The ultra-high temperature and ultra-high pressure airflow heated by the heater must meet the requirement that the wind tunnel running time is greater than 1 second. The volume of ultra-high temperature and ultra-high pressure test airflow provided by the heater in a single test needs to be several cubic meters, and the corresponding pressure vessel volume is even larger.

[0006] 3. Ultra-high temperature and ultra-high pressure tests require a clean and pollution-free environment;

[0007] 4. During the operation of the high Reynolds number hypersonic wind tunnel, the temperature and pressure of the gas flow at the heater outlet must remain constant at 200 MPa and 2300 K.

[0008] The continuous and regenerative air heaters commonly used in conventional hypersonic wind tunnels have the following shortcomings:

[0009] 1. Heating elements such as resistance bands, resistance wires, and armored heating tubes are made of metal, and their operating temperature is far below 2300K, which cannot meet the heating requirements of the test gas flow.

[0010] 2. The working temperature of the metal heat storage body is far below 2300K, which cannot meet the heating requirements of the test gas flow;

[0011] 3. The pebble bed heat storage body has an inherent problem of slag shedding, which contaminates the test airflow. At the same time, under the scouring of ultra-high pressure and high flow rate airflow, the pebble bed will float and damage the internal components of the heater.

[0012] 4. Ultra-high pressure integral forged pressure vessels may experience a catastrophic explosion within seconds, posing a significant safety hazard;

[0013] 5. Manufacturing large-capacity, 200MPa ultra-high pressure integral forging pressure vessels with a volume of several cubic meters is difficult and risky;

[0014] 6. At 2300K, heaters using air as the test medium will experience oxidation of the heater's heating element and internal components, affecting the heater's performance.

[0015] To address the issues of low operating temperature and contamination of test airflow in continuous and regenerative heaters, as well as the small volume, significant safety hazards, and oxidation of heater internals by air media in integral forged pressure vessels, there is an urgent need to develop a heater for high Reynolds number hypersonic wind tunnels. Summary of the Invention

[0016] The technical problem to be solved by the present invention is to provide a heater for high Reynolds number hypersonic wind tunnels, which solves the problems of low operating temperature, contamination of test airflow, small volume of integral forged pressure vessels, large safety hazards, and oxidation of heater internals by air medium in continuous and regenerative heaters.

[0017] The heater for a high Reynolds number hypersonic wind tunnel of the present invention is characterized in that the heater is a tank, which consists of a lower plug, a winding cylinder and an upper plug from bottom to top;

[0018] The lower plug is equipped with an air inlet, which is L-shaped and adopts a horizontal air intake and vertical upward air outlet structure; the upper plug is equipped with an air outlet, which is Γ-shaped and adopts a vertical upward air intake and horizontal air outlet structure; the inner diameters of the air inlet and the air outlet are equal.

[0019] The winding cylinder is covered with a winding frame; the inner wall of the winding cylinder is covered with a heat insulation cover, and the heating elements are evenly distributed on the inner wall of the heat insulation cover; the lower part of the winding cylinder is suspended and fixed with a cold air guide platform, the vertical distance between the lower surface of the cold air guide platform and the bottom surface of the winding cylinder is h, and the gap between the lower surface of the cold air guide platform and the bottom surface of the winding cylinder forms a flow equalization cavity.

[0020] The airflow guide is a spiral body, consisting of a guide plate, a cylindrical section, and a baffle from bottom to top. The guide plate is a ring extending horizontally from the lower surface of the cylindrical section, with the outer diameter of the ring being larger than the inner diameter of the heating element. The height of the cylindrical section is H, where H > h. The baffle is a cone extending outward and downward from the upper surface of the cylindrical section, with a diameter that is smaller at the top and larger at the bottom. The cone angle of the baffle ranges from 30° to 60°.

[0021] The heating element heats the nitrogen gas inside the winding cylinder. When the pressure and temperature of the nitrogen gas reach the set values, it forms ultra-high temperature and ultra-high pressure hot gas. The heating element stops working, and the diaphragm downstream of the heater's outlet ruptures or the valve opens. At the same time, an equal volume of cold driving gas enters the flow equalization chamber through the inlet on the lower plug of the heater. After being rectified by the cold gas guide platform, it enters the winding cylinder. The cold driving gas pushes the ultra-high temperature and ultra-high pressure hot gas inside the winding cylinder upward through the gas piston, thereby maintaining the total temperature and total pressure of the hot gas at the heater's outlet constant until the hot gas inside the heater is exhausted, and the high Reynolds number hypersonic wind tunnel operation ends.

[0022] Furthermore, the maximum temperature of the ultra-high temperature and ultra-high pressure hot gas is 2300K and the maximum pressure is 200MPa.

[0023] Furthermore, the cold driving gas is nitrogen gas with a temperature of 323K and a pressure range of 200MPa to 250MPa.

[0024] Furthermore, the heating element is a carbon-carbon composite material heating element.

[0025] The heater of this invention for high Reynolds number hypersonic wind tunnels has a large volume, heats the test gas to a high temperature, and provides a clean and uncontaminated test gas, thus meeting the heating requirements of high Reynolds number hypersonic wind tunnel test gas. The heater uses a carbon-carbon composite material as the heating element and nitrogen as the test medium, ensuring that the test gas temperature reaches 2300K without oxidation damage to the heating element and heater internals. The heater uses a winding cylinder and winding frame as a pressure vessel, with cold gas inlets and hot gas outlets at the lower and upper plugs, ensuring that the heater's hot zone volume meets the operating time and high flow rate requirements of the high Reynolds number hypersonic wind tunnel. The heater uses a gas piston-driven operation mode, ensuring that the heater output... The hot gas pressure and temperature are kept constant. Simultaneously, without increasing the heater volume, the internal hot gas is fully utilized to extend the effective operating time of the high Reynolds number hypersonic wind tunnel, reaching 1 to tens of seconds. A cold gas guide platform is installed at the bottom of the heater, which reduces the cold gas velocity and adjusts the airflow direction, lowering the mixing speed between cold and hot gas, improving gas piston drive efficiency and hot gas utilization, further extending the effective operating time of the high Reynolds number hypersonic wind tunnel. A flow equalization cavity is set between the lower plug of the heater and the cold gas guide platform, ensuring uniform cold gas velocity, density, and pressure entering the guide platform, thereby improving gas piston drive efficiency and hot gas utilization. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the internal structure of the heater for a high Reynolds number hypersonic wind tunnel according to the present invention;

[0027] Figure 2 This is a schematic diagram of the external structure of the heater for a high Reynolds number hypersonic wind tunnel according to the present invention.

[0028] In the diagram, 1. Air inlet; 2. Lower plug; 3. Cold air guide platform; 4. Winding cylinder; 5. Winding frame; 6. Heating element; 7. Heat shield; 8. Upper plug; 9. Air outlet; 10. Flow equalization chamber. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] like Figure 1 , Figure 2 As shown, the heater for the high Reynolds number hypersonic wind tunnel in this embodiment is a tank, which consists of a lower plug 2, a winding cylinder 4, and an upper plug 8 from bottom to top.

[0032] The lower plug 2 is provided with an air inlet 1, which is L-shaped and adopts a horizontal air intake and vertical upward air outlet structure; the upper plug 8 is provided with an air outlet 9, which is Γ-shaped and adopts a vertical upward air intake and horizontal air outlet structure; the inner diameters of the air inlet 1 and the air outlet 9 are equal.

[0033] The winding cylinder 4 is covered with a winding frame 5; the inner wall of the winding cylinder 4 is covered with a heat insulation cover 7, and the heating elements 6 are evenly distributed on the inner wall of the heat insulation cover 7; the lower part of the winding cylinder 4 is suspended and fixed with a cold air guide platform 3, the vertical distance between the lower surface of the cold air guide platform 3 and the bottom surface of the winding cylinder 4 is h, and the gap between the lower surface of the cold air guide platform 3 and the bottom surface of the winding cylinder 4 forms a flow equalization cavity 10.

[0034] The airflow guide platform 3 is a spiral body, consisting of a guide plate, a cylindrical section, and a baffle plate from bottom to top. The guide plate is a ring extending horizontally from the lower surface of the cylindrical section, and the outer diameter of the ring is smaller than the inner diameter of the heating element 6. The height of the cylindrical section is H, where H > h. The baffle plate is a cone extending outward and downward from the top surface of the cylindrical section, with a diameter that is smaller at the top and larger at the bottom. The cone angle of the baffle plate ranges from 30° to 60°.

[0035] Heating element 6 heats the nitrogen gas inside the winding cylinder 4. When the pressure and temperature of the nitrogen gas reach the set value, it forms ultra-high temperature and ultra-high pressure hot gas. Heating element 6 stops working, and the diaphragm downstream of the heater outlet 9 ruptures or the valve opens. At the same time, an equal volume of cold driving gas enters the flow equalization chamber 10 through the air inlet 1 on the heater lower plug 2. After being rectified by the cold gas guide platform 3, it enters the winding cylinder 4. The cold driving gas pushes the ultra-high temperature and ultra-high pressure hot gas inside the winding cylinder 4 through the gas piston drive, thereby maintaining the total temperature and total pressure of the hot gas at the heater outlet 9 constant until the hot gas inside the heater is emptied, and the high Reynolds number hypersonic wind tunnel operation ends.

[0036] In this embodiment, the test medium for the heater used in the high Reynolds number hypersonic wind tunnel is nitrogen. The heating element 6 of CC composite material directly heats the nitrogen inside the winding cylinder 4 through convection and radiation heating, thereby raising the temperature, pressurizing, maintaining the temperature and pressure of the nitrogen to achieve the specifications of 2300K and 200MPa. The heater has no heat storage element, the internal parts of the heater will not be oxidized by oxygen, the operating temperature is high, and the internal test airflow is clean and uncontaminated.

[0037] In this embodiment, the heater for the high Reynolds number hypersonic wind tunnel employs a gas piston-driven operation mode that uses ultra-high pressure cold gas to drive ultra-high temperature and ultra-high pressure hot gas, maintaining a constant total temperature and total pressure of the hot gas at the heater outlet 9. This gas piston-driven operation mode ensures constant pressure and temperature of the hot gas at the heater outlet, while fully utilizing the ultra-high temperature and ultra-high pressure hot gas inside the heater, enabling the high Reynolds number hypersonic wind tunnel to operate effectively for 1 second to tens of seconds.

[0038] The heater for the high Reynolds number hypersonic wind tunnel in this embodiment adopts an internal hollow structure, and the heating element 6 is arranged on the inner wall of the winding cylinder 4, that is, on the outside of the hot zone, which is beneficial to improve the gas piston driving efficiency and extend the effective operating time of the high Reynolds number hypersonic wind tunnel.

[0039] Below the cold gas guide platform 3 in the heater of the high Reynolds number hypersonic wind tunnel in this embodiment is a flow equalization chamber 10. The function of the flow equalization chamber 10 is to equalize the flow of the ultra-high pressure cold gas entering from the air inlet 1, so that the velocity, density and pressure of the ultra-high pressure cold gas are uniform. This ensures that the velocity, density and pressure of the ultra-high pressure cold gas entering the cold gas guide platform 3 are uniform, thereby improving the gas piston driving efficiency and heat utilization rate. The guide plate, cylindrical section and baffle plate provided on the cold gas guide platform 3 can further reduce the airflow velocity of the ultra-high pressure cold gas and adjust the airflow direction, reduce the mixing speed of cold gas and hot gas, and improve the gas piston driving efficiency and heat utilization rate.

[0040] In this embodiment, the inlet 1 and outlet 9 of the heater used in a high Reynolds number hypersonic wind tunnel have the same inner diameter, ensuring that the volumetric flow rate of inlet 1 and outlet 9 is the same when the gas piston is driven, thereby ensuring that the temperature and pressure of the gas flow at the heater outlet are constant.

[0041] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments, and can be applied to various fields suitable for the present invention. Those skilled in the art will readily implement other improvements and modifications without departing from the principles of the present invention. The present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A heater for a high Reynolds number hypersonic wind tunnel, characterized in that, The heater is a tank body, sequentially comprising a lower plug (2), a winding cylinder (4) and an upper plug (8) from bottom to top. The lower plug (2) is provided with an air inlet (1) which is L-shaped and adopts a horizontal air inlet and vertical upward air outlet structure; the upper plug (8) is provided with an air outlet (9) which is Γ-shaped and adopts a vertical upward air inlet and horizontal air outlet structure; the air inlet (1) and the air outlet (9) have equal inner diameters. The winding cylinder (4) is sleeved with a winding rack (5); the inner wall of the winding cylinder (4) is covered with a heat shield (7), and the inner wall of the heat shield (7) is uniformly distributed with heating elements (6); the lower part of the winding cylinder (4) is suspendedly fixed with a cold air flow guide table (3), and the vertical distance between the lower surface of the cold air flow guide table (3) and the bottom surface of the winding cylinder (4) is h; the gap between the lower surface of the cold air flow guide table (3) and the bottom surface of the winding cylinder (4) forms a uniform flow cavity (10). The cold air flow guide table (3) is a rotary body, sequentially comprising a flow guide plate, a cylindrical section and a flow blocking plate from bottom to top; the flow guide plate is a circular ring horizontally extended from the lower surface of the cylindrical section, and the outer diameter of the circular ring is greater than the inner diameter of the heating element (6); the height of the cylindrical section is H, and H>h; the flow blocking plate is a conical cylinder with a diameter decreasing from top to bottom, and the taper angle of the flow blocking plate ranges from 30° to 60°. The heating element (6) heats the nitrogen in the winding cylinder (4); when the pressure and temperature of the nitrogen reach the set values, the super-high-temperature and super-high-pressure hot gas is formed, the heating element (6) stops working, the downstream diaphragm of the air outlet (9) of the heater breaks or the valve opens, at the same time, an equal volume of cold driving gas enters the uniform flow cavity (10) through the air inlet (1) on the lower plug (2) of the heater, and then enters the winding cylinder (4) after being rectified by the cold air flow guide table (3); the cold driving gas pushes the super-high-temperature and super-high-pressure hot gas in the winding cylinder (4) upward by the gas piston driving form, so as to maintain the constant total temperature and total pressure of the hot gas at the air outlet (9) of the heater, until the hot gas in the heater is exhausted, and the high Reynolds number and high supersonic speed wind tunnel operation is completed.

2. The heater for a high Reynolds number hypersonic wind tunnel of claim 1, wherein, The highest temperature of the super-high-temperature and super-high-pressure hot gas is 2300K, and the highest pressure is 200MPa.

3. The heater for high Reynolds number hypersonic wind tunnels of claim 1, wherein, The cold driving gas is nitrogen with a normal temperature of 323K and a pressure ranging from 200MPa to 250MPa.

4. The heater for a high Reynolds number hypersonic wind tunnel of claim 1, wherein, The heating element (6) is a carbon-carbon composite material heating element.

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