Electric heater for hypersonic wind tunnel

Abstract

The utility model relates to the technical field of electric heaters, in particular to an electric heater for a hypersonic wind tunnel. Comprising a container which comprises an outer cylinder and an inner cylinder; the outer cylinder and the inner cylinder are coaxially connected in a sleeved mode, a gap is formed between one end of the inner cylinder and an end cover of the outer cylinder, and the other end of the inner cylinder extends to be exposed out of the outer cylinder. The electric heating core comprises a supporting plate and a heating pipe element; the plurality of supporting plates are arranged in the inner cylinder at equal intervals, and the plurality of heating tube elements are uniformly arrayed and inserted on the supporting plates; the heating pipe element is formed by bundling a plurality of small steel pipes. According to the heating tube element, a traditional single hollow tube is changed into a small tube bundle, the circulation equivalent diameter of fluid is reduced, and the heat exchange coefficient is increased; the heating pipe element is low in temperature and longer in service life; the device is especially suitable for hypersonic wind tunnels and occasions with the heating temperature of about 1000 DEG C.

Description

Technical Field

[0001] The utility model relates to the technical field of electric heaters, in particular to an electric heater for a hypersonic wind tunnel. Background Technique

[0002] In a hypersonic wind tunnel, the air in the test section expands violently due to being accelerated to a very high speed when flowing through the nozzle, and the static temperature is very low, which will cause the air flow to change from an unsaturated state to a supersaturated state. Once condensation occurs in the air flow, it will directly affect the accuracy of the wind tunnel data. On the one hand, the latent heat released by the condensation of the air flow changes the specific heat. If there are water particles in the air flow, icing will occur on the model and the measurement probe, and it will be difficult to read the readings of the measuring instrument at this time. On the other hand, research has shown that in a hypersonic wind tunnel, the pressure of the air flow is greatly affected by the condensation of the air. Because of the heat release during condensation, the entire flow process changes from isentropic to non-isentropic, the mechanical energy decreases and is converted into heat energy, the total pressure also decreases accordingly, the static pressure increases, and the Mach number decreases. Therefore, it is necessary to use equipment to preheat the air flow in advance to increase the total temperature of the incoming fluid.

[0003] Generally, to increase the total temperature of the incoming fluid, an electric heating method is often used. The traditional resistance wire or resistance band heating or the heating method using a hollow tube as a resistor is adopted. For some low Mach number occasions, the traditional method has not too many problems. However, for high Mach number occasions, the problems that occur in the traditional heating method or the method of connecting multiple single hollow tubes in series are that the heating element burns out due to insufficient heat transfer coefficient. Especially in the high-temperature heating occasion where the Mach number exceeds 8, the service life of the heating element is greatly affected, and there is an urgent need to develop a heating element for high-temperature heating in hypersonic wind tunnels. Content of the Utility Model

[0004] The purpose of the utility model is to provide an electric heater for a hypersonic wind tunnel with a small volume and a high heat transfer coefficient, so that the entire heating tube element is both a heat exchange tube and a heating tube. The heating tube element is changed from a traditional single hollow tube to a thin tube bundle, the equivalent diameter of the fluid flow decreases, and the heat transfer coefficient increases; the surface temperature of the heating tube element is lower during operation, and the service life is longer; it is especially suitable for hypersonic wind tunnels with a heating temperature of about  1000°C.

[0005] To solve the above technical problems, the utility model provides an electric heater for a hypersonic wind tunnel, including:

[0006] A container, the container includes an outer cylinder and an inner cylinder; the outer cylinder and the inner cylinder are coaxially sleeved, and there is a distance between one end of the inner cylinder and the end cover of the outer cylinder, and the other end extends and is exposed outside the outer cylinder;

[0007] Electric heating core, the electric heating core includes a support plate and a heating tube element; a plurality of the support plates are arranged equidistantly inside the inner cylinder, and a plurality of the heating tube elements are uniformly and arrayedly inserted on the support plate; the heating tube element is formed by bundling a plurality of small steel pipes.

[0008] Preferably, it further includes a support rod, and a plurality of the support rods are circumferentially inserted on the support plates arranged equidistantly; a high-temperature resistant ceramic sleeve is also arranged between the heating tube element and the support plate.

[0009] Preferably, a fluid inlet is opened on the outer cylinder on the side away from the end cover, and the port of the inner cylinder exposed outside the outer cylinder is a fluid outlet.

[0010] Preferably, it further includes a short-circuit ring, and both ends of the heating tube element are embedded on the short-circuit ring.

[0011] Preferably, it further includes a connecting piece, and the connecting piece is arranged in an S-shaped path and staggered on the short-circuit rings at both ends of every two adjacent heating tube elements, so that a plurality of the heating tube elements form a series circuit.

[0012] Preferably, in the direction of the fluid flow, the heating tube element is formed by sequentially connecting in series a single small steel pipe, two small steel pipes, three small steel pipes to N small steel pipes through a tapered adapter.

[0013] Preferably, according to the fluid flow direction, the small steel pipe can be welded by selecting different sections of heating materials, so that the heating resistance of the heating tube element is gradually set from high to low; or by selecting the same heating material, the thickness of the small steel pipe is gradually set from thin to thick.

[0014] Preferably, a plurality of the heating tube elements are arranged in two concentric circular arrays; the heating tube elements on the inner circular array form one series circuit, the heating tube elements on the outer circular array form two symmetrically distributed series circuits, and both ends of each series circuit are respectively connected to the terminal on the junction box through a power lead rod.

[0015] Preferably, a temperature sensor is further included on the electric heating core, and the heating tube element is in contact with the detection probe of the temperature sensor.

[0016] Preferably, a layer of high-temperature resistant ceramic coating is also sprayed and sintered on the outer surface of the support plate.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] 1. The heating tube element designed by the utility model is formed by bundling thin steel pipes. The equivalent diameter of fluid flow is reduced, the heat transfer coefficient is increased, and the service life of the heating tube element is extended, ensuring that the entire heating tube element can be used at a temperature of about 1000 °C for a long time.

[0019] 2. The utility model ingeniously utilizes the equipotential advantage of the current flowing through the bundled thin steel pipes, and short-circuit rings can be added at any point according to needs. The purpose is to enhance the bundling degree of the bundled thin steel pipes, and improve the overall strength of the heating tube element formed by the bundled thin steel pipes.

[0020] 3. The heating tube element designed by the utility model is designed with an equal load according to needs, which is more conducive to improving the service life of the system.

[0021] 4. The heating tube element designed by the utility model has good anti-vibration strength in a hypersonic wind tunnel. The bundled thin steel pipe structure is especially suitable for the occasion of a hypersonic wind tunnel with a Mach number above 6. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the front view of an electric heater for a hypersonic wind tunnel of the utility model.

[0023] Figure 2 It is the cross-sectional view of an electric heater for a hypersonic wind tunnel of the utility model.

[0024] Figure 3 It is the structural diagram of the installation of the support plate and the support rod in the utility model.

[0025] Figure 4 It is the left view of the electric heating core in the utility model.

[0026] Figure 5 It is the right view of the electric heating core in the utility model.

[0027] Figure 6 It is the schematic diagram of the electric heating core in the utility model in a double concentric circular array.

[0028] Figure 7 It is the structural diagram of the heating tube element in the first embodiment of the utility model.

[0029] Figure 8 It is the structural diagram of the heating tube element with several short-circuit rings added in the first embodiment of the utility model.

[0030] Figure 9 It is the structural diagram of the heating tube element in the second embodiment of the utility model.

[0031] In the figure: 1 - container, 11 - outer cylinder, 12 - inner cylinder, 13 - end cover, 14 - fluid inlet, 15 - fluid outlet, 2 - electric heating core, 21 - support plate, 22 - heating tube element, 23 - small steel tube, 24 - support rod, 25 - high-temperature resistant ceramic sleeve, 26 - short-circuit ring, 27 - connecting piece, 3 - conical adapter, 4 - power supply lead rod. Specific embodiments

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are in a very simplified form and are all in non-precise proportions, only for the purpose of conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0033] Embodiment 1

[0034] As Figures 1 to 7 shown, the embodiment of the present invention specifically discloses a technical solution of an electric heater for a hypersonic wind tunnel, including: a container 1, and the container 1 includes an outer cylinder 11 and an inner cylinder 12; the outer cylinder 11 and the inner cylinder 12 are coaxially sleeved, and there is a gap between one end of the inner cylinder 12 and the end cover 13 of the outer cylinder 11, and the other end extends and is exposed outside the outer cylinder 11; the above-mentioned inner cylinder 12 is used for bearing temperature, and the outer cylinder 11 is used for bearing pressure, adopting a reflux double-wall structure, which is beneficial to the cooling of the container 1 shell; an electric heating core 2, and the electric heating core 2 includes a support plate 21 and a heating tube element 22; a plurality of support plates 21 are arranged at equal intervals inside the inner cylinder 12. Here, it is necessary to ensure that the installation gap between the inner cylinder 12 and the support plate 21 is extremely small or achieve a sealed connection, so as to prevent the fluid from flowing through the gap and not flowing through the inside of the small steel tube 23, and a plurality of heating tube elements 22 are evenly arranged and inserted on the support plate 21; the heating tube element 22 is formed by bundling a plurality of small steel tubes 23, and the gas will flow through the inside of the plurality of small steel tubes 23. The purpose is to reduce the equivalent diameter of the air flow, increase the heat transfer coefficient, and extend the service life of the equipment. At the same time, a plurality of small steel tubes 23 are bundled together, increasing the strength of the heating tube element 22. The heating tube element 22 is both a heat exchange tube and a heating tube, and generates energy by the resistance of the heating tube element 22 itself under the action of current. It is a product with very high heat exchange efficiency. The bundled structure of the small steel tubes 23 is particularly suitable for the occasion of a hypersonic wind tunnel with a Mach number above 6.

[0035] It also includes support rods 24, and a plurality of support rods 24 are circumferentially inserted on the support plates 21 arranged at equal intervals; between the heating tube element 22 and the support plate 21, there is also a high-temperature resistant ceramic sleeve 25 arranged. Here, the high-temperature resistant ceramic sleeve 25 needs to ensure a sealed connection or an extremely small installation gap between the heating tube element 22 and the support plate 21 respectively, so as to prevent the fluid from flowing through the gap and not flowing through the inside of the small steel tube 23.

[0036] A fluid inlet 14 is provided on the outer cylinder 11 on the side away from the end cap 13, and the port of the inner cylinder 12 exposed outside the outer cylinder 11 is the fluid outlet 15.

[0037] It further includes a short - circuit ring 26, and both ends of the heating tube element 22 are embedded on the short - circuit ring 26.

[0038] It further includes a connecting piece 27. The connecting piece 27 is arranged in an S - shaped path and staggered on the short - circuit rings 26 at both ends of every two adjacent heating tube elements 22, so that a number of heating tube elements 22 form a series circuit.

[0039] As Figure 8 shown, taking advantage of the equipotential of the current flowing through the bundled small steel pipes, in order to enhance the bundling degree of the bundled small steel pipes and overall improve the strength of the heating tube element formed by the bundled small steel pipes, short - circuit rings 26 can be added at any point as needed, that is, a number of short - circuit rings 26 can be arranged at any point according to requirements between the two end short - circuit rings 26, as Figure 8 shown. Specifically, by adding three short - circuit rings 26, its overall bundling strength is improved.

[0040] A number of heating tube elements 22 are arranged in two concentric circular arrays. Here, in order to increase the standby function, a heating tube element 22 is also provided at the center of the concentric circles, but it is not energized. The heating tube elements 22 on the inner circular array form a series circuit, and the heating tube elements 22 on the outer circular array form two symmetrically distributed series circuits. And both ends of each series circuit are respectively connected to the terminal on the junction box through the power supply lead rod 4. According to needs, Y - type or delta - type connection can be adopted, and the junction box can be designed as a dust - proof, waterproof or explosion - proof structure.

[0041] The heating tube element 22 can be designed with an equal - load design. At the place where the temperature of the fluid inlet 14 is low, the power load is a little higher, and at the place where the temperature of the fluid outlet 15 is high, the power load is a little lower.

[0042] The electric heating core 2 further includes a temperature sensor to prevent the system from overheating, and the heating tube element 22 is in contact with the detection probe of the temperature sensor to ensure the accuracy of the temperature measurement of the heating tube element 22 by the temperature sensor.

[0043] The outer surface of the support plate 21 further includes a layer of high - temperature - resistant ceramic coating sprayed and sintered to prevent the risk of the system being electrified due to the damage of the ceramic parts.

[0044] Embodiment Two

[0045] As Figure 9As shown, on the basis of the above-mentioned First Embodiment, the heating tube element 22 can also adopt the following structure: To achieve an equal load design for the heating tube element 22, in the direction of the fluid flow, the heating tube element 22 is formed by sequentially connecting a single small steel pipe 23, two small steel pipes 23, three small steel pipes 23 to N small steel pipes 23 through a tapered adapter 3. The purpose is that the current flowing through is the same, but the resistance of each section is different, and the heating power of each section is also different, thus realizing the concept of equal load design.

[0046] Third Embodiment

[0047] On the basis of the above-mentioned First Embodiment, the heating tube element 22 can also adopt the following structure: To achieve an equal load design for the heating tube element 22, according to the fluid flow direction, the small steel pipe 23 can be welded by selecting different sections of heating materials, so that the heating resistance of the heating tube element 22 is gradually set from high to low; or by selecting the same heating material, the thickness of the small steel pipe 23 is gradually set from thin to thick.

[0048] The above description is only for the description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention according to the above disclosure shall fall within the protection scope of the claims.

Claims

1. A heater for a hypersonic wind tunnel, characterized in that Comprising: A container (1), the container (1) including an outer cylinder (11) and an inner cylinder (12); the outer cylinder (11) and the inner cylinder (12) are coaxially sleeved, and there is a spacing between one end of the inner cylinder (12) and the end cover (13) of the outer cylinder (11), and the other end extends and is exposed outside the outer cylinder (11); An electric heating core (2), the electric heating core (2) including a support plate (21) and heating tube elements (22); a plurality of the support plates (21) are arranged at equal intervals inside the inner cylinder (12), and a plurality of the heating tube elements (22) are uniformly and arrayedly inserted on the support plate (21); the heating tube elements (22) are formed by bundling a plurality of small steel pipes (23).

2. The electric heater for a hypersonic wind tunnel according to claim 1, characterized in that, It further includes support rods (24), a plurality of the support rods (24) are circumferentially inserted on the support plates (21) arranged at equal intervals; a high-temperature resistant ceramic sleeve (25) is also provided between the heating tube elements (22) and the support plate (21).

3. The electric heater for a hypersonic wind tunnel according to claim 1, characterized in that, A fluid inlet (14) is opened on the outer cylinder (11) on the side away from the end cover (13), and the port of the inner cylinder (12) exposed outside the outer cylinder (11) is a fluid outlet (15).

4. The electric heater for hypersonic wind tunnel according to claim 1, characterized in that, It further includes a short-circuit ring (26), and both ends of the heating tube element (22) are embedded on the short-circuit ring (26).

5. The electric heater for a hypersonic wind tunnel according to claim 4, characterized in that It further includes a connecting piece (27), the connecting piece (27) is arranged in an S-shaped path and staggered on the short-circuit rings (26) at both ends of every two adjacent heating tube elements (22), so that a plurality of the heating tube elements (22) form a series circuit.

6. The electric heater for a hypersonic wind tunnel according to claim 1, characterized in that, In the direction of the fluid flow, the heating tube elements (22) are sequentially connected in series by a single small steel pipe (23), a double small steel pipe (23), a triple small steel pipe (23) to an N small steel pipe (23) through a tapered adapter (3).

7. The electric heater for hypersonic wind tunnel according to claim 1, characterized in that, According to the fluid flow direction, the small steel pipes (23) can be welded by selecting different sections of heating materials, so that the heating resistance of the heating tube element (22) is gradually set from high to low; or by selecting the same heating material, the thickness of the small steel pipes (23) is gradually set from thin to thick.

8. The electric heater for a hypersonic wind tunnel according to claim 5, characterized in that, A plurality of the heating tube elements (22) are arranged in two concentric circular arrays; the heating tube elements (22) on the inner circular array form one series circuit, the heating tube elements (22) on the outer circular array form two symmetrically distributed series circuits, and both ends of each series circuit are respectively connected to the terminal on the junction box through a power lead rod (4).

9. The electric heater for a hypersonic wind tunnel according to claim 1, characterized in that, The electric heating core (2) further includes a temperature sensor, and the heating tube element (22) is in contact with the detection probe of the temperature sensor.

10. A kind of electric heater for hypersonic wind tunnel according to any one of claims 1 to 9, characterized in that, The outer surface of the support plate (21) further includes a layer of high-temperature resistant ceramic coating sprayed and sintered.

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