Air-breathing aircraft for long-term flight in upper atmosphere

Abstract

The invention provides an air-breathing aircraft for long-term flight in an upper atmosphere, and relates to the technical field of aircrafts in the upper atmosphere, the air-breathing aircraft comprises an aircraft body, the aircraft body is provided with an air-breathing electric propulsion system, the outer contour of the aircraft body is cylindrical, and an air inlet channel is arranged in the center of the aircraft body; the air inlet channel comprises a gradually-shrinking conical inlet pipeline, an inwards-concave gradually-shrinking compression pipeline, a cylindrical ionization acceleration pipeline and a gradually-expanding conical outlet pipeline which are sequentially arranged from front to back. The solar cell wings are arranged on the outer side of the aircraft body, the solar cell wings are forward-swept trapezoidal wings, and the solar cell wings can supply power to the air suction type electric propulsion system; the problem that in the prior art, technical defects exist in the aerodynamic configuration design of how to achieve thrust and resistance balance of an aircraft flying for a long time in the upper atmosphere is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of upper atmosphere aircraft, and more specifically, relates to an air-breathing aircraft for long-term flight in the upper atmosphere. Background Art

[0002] An upper atmosphere vehicle refers to a vehicle that flies at an altitude of 100km to 300km for a long time. Compared with low-orbit satellites, an upper atmosphere vehicle has the advantages of higher spatial resolution for ground observation or reconnaissance, lower launch cost, shorter communication delay and less communication loss. In addition, the flight environment of an upper atmosphere vehicle is safer because the thin atmosphere can block some cosmic rays, resulting in lower cosmic ray intensity; and the thin atmospheric drag causes space debris in the area to automatically decay and crash, thereby reducing the risk of collision with space debris. In the current situation of tight resources in high, medium and low orbits, the development and utilization of the upper atmosphere airspace will undoubtedly improve the utilization rate of orbital space. Moreover, once the power system fails, the upper atmosphere vehicle will automatically crash and will not generate new space debris.

[0003] However, the air density in the upper atmosphere between near space and outer space is extremely low, and aircraft can hardly use aerodynamic force to maneuver. Spacecraft cannot operate in orbit for a long time due to atmospheric drag. This is because the fuel consumption required to overcome atmospheric drag to maintain orbital altitude and implement orbit change maneuvers is very large. Therefore, there are currently no mature aircraft that can fly for a long time in the upper atmosphere, and this airspace has not yet been developed and utilized. One difficulty in the research of upper atmosphere aircraft is the design of its aerodynamic shape, especially how to achieve a balance between thrust and drag under limited solar energy supply. There has been no obvious technical breakthrough so far, and this is precisely the core technology for upper atmosphere aircraft to achieve long-term flight. Summary of the invention

[0004] The purpose of the present invention is to provide an air-breathing aircraft for long-term flight in the upper atmosphere in view of the deficiencies in the prior art, so as to solve the problem in the prior art of how the aerodynamic shape design of an aircraft for long-term flight in the upper atmosphere achieves a balance between thrust and drag.

[0005] In order to achieve the above object, the present invention provides an air-breathing aircraft for long-term flight in the upper atmosphere, comprising: An aircraft body, wherein the aircraft body has an air-breathing electric propulsion system, the outer contour of the aircraft body is cylindrical, an air inlet is arranged at the center of the aircraft body, and the air inlet comprises a tapered inlet duct, a concave tapered compression duct, a cylindrical ionization acceleration duct and a gradually expanding tapered outlet duct arranged in sequence from front to back; A solar cell wing is provided on the outer side of the aircraft body. The solar cell wing is a forward-swept trapezoidal wing and can supply power to the air-breathing electric propulsion system.

[0006] Optionally, the front radius of the tapered conical inlet duct is equal to the outer contour radius of the aircraft body.

[0007] Optionally, the cone angle of the tapered conical inlet duct differs from the forward sweep angle of the forward-swept trapezoidal wing by -10° to 10°.

[0008] Optionally, the cross-sectional profile of the concave tapered compression duct is arc-shaped, and the front radius of the concave tapered compression duct is equal to the rear radius of the tapered conical inlet duct.

[0009] Optionally, the radius of the cylindrical ionization acceleration duct is 25% to 75% of the rear radius of the tapered conical inlet duct.

[0010] Optionally, the front radius of the tapered conical outlet duct is equal to the radius of the cylindrical ionization acceleration duct.

[0011] Optionally, the front end of the root of the forward-swept trapezoidal wing is flush with the front end of the aircraft body.

[0012] Optionally, the rear end of the root of the forward-swept trapezoidal wing extends beyond the rear end of the aircraft body.

[0013] Optionally, a pair of the solar cell wings are symmetrically arranged on the outer side of the aircraft body.

[0014] Optionally, the forward-swept trapezoidal wing is a flat plate structure, and the thickness of the forward-swept trapezoidal wing is 20 mm to 40 mm.

[0015] The present invention provides an air-breathing aircraft for long-term flight in the upper atmosphere, and its beneficial effects are as follows: The aircraft body of the air-breathing aircraft for long-term flight in the upper atmosphere has an air-breathing electric propulsion system. Based on the aerodynamic characteristics of the upper atmosphere, considering that the rarefied atmosphere in the upper atmosphere will generate resistance, making it difficult for the aircraft to fly long-term, the air-breathing electric propulsion system is used to generate thrust to overcome the resistance generated by the rarefied atmosphere. At the same time, solar cell wings are arranged on the outside of the aircraft body, and the electric energy of the air-breathing electric propulsion system is provided by the solar cell wings to meet the energy supply requirements; the aircraft body can carry payloads. The air intake of the air-breathing electric propulsion system is located at the center of the aircraft body and is a through-hole structure. Gas enters the air intake through a tapered inlet pipe, is compressed in an inwardly concave tapered compression pipe, then is ionized and accelerated in a cylindrical ionization acceleration pipe, and finally is discharged through a tapered outlet pipe to generate thrust; the solar cell wings adopt forward-swept trapezoidal wings. The existence of the forward sweep angle and the increase in the taper angle of the tapered inlet pipe improve the effective inlet size of the air intake, which is beneficial for the high-speed and low-density upper atmosphere to enter the air intake, thereby enhancing the gas collection performance of the air intake; after the air intake collects and compresses the low-density upper atmosphere, the air-breathing electric propulsion system ionizes and accelerates it using the electric energy provided by the solar cell wings to generate thrust and overcome the atmospheric resistance suffered by the aircraft, thereby achieving long-term flight.

[0016] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By describing the exemplary embodiments of the present invention in more detail in conjunction with the drawings, the above-mentioned and other objects, features, and advantages of the present invention will become more obvious. Among them, in the exemplary embodiments of the present invention, the same reference numerals generally represent the same components.

[0018] Figure 1 FIG. shows a three-dimensional structural schematic diagram of an air-breathing aircraft for long-term flight in the upper atmosphere according to Embodiment 1 of the present invention.

[0019] Figure 2 FIG. shows a central longitudinal sectional schematic diagram of an air-breathing aircraft for long-term flight in the upper atmosphere according to Embodiment 1 of the present invention.

[0020] Figure 3 FIG. shows a sectional schematic diagram of the aircraft body and the air intake of an air-breathing aircraft for long-term flight in the upper atmosphere according to Embodiment 1 of the present invention.

[0021] Figure 4 FIG. shows a central longitudinal sectional schematic diagram of an air-breathing aircraft for long-term flight in the upper atmosphere according to Embodiment 2 of the present invention.

[0022] Figure 5 Shows a schematic central longitudinal section of a scramjet aircraft for long-term flight in the upper atmosphere according to Embodiment 3 of the present invention.

[0023] Description of reference numerals: 1. Aircraft body; 2. Inlet duct; 3. Solar cell wing; 4. Tapered inlet duct; 5. Concave tapered compression duct; 6. Cylindrical ionization acceleration duct; 7. Divergent tapered outlet duct. Detailed implementation manners

[0024] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0025] Embodiment 1

[0026] As Figures 1 to 3 shown, the present invention provides a scramjet aircraft for long-term flight in the upper atmosphere, including: An aircraft body 1, the aircraft body 1 having a scramjet electric propulsion system, the outer contour of the aircraft body 1 being cylindrical, and an inlet duct 2 being provided at the central position of the aircraft body 1. The inlet duct 2 includes a tapered inlet duct 4, a concave tapered compression duct 5, a cylindrical ionization acceleration duct 6, and a divergent tapered outlet duct 7 arranged in sequence from front to back; A solar cell wing 3, the solar cell wing 3 being provided on the outside of the aircraft body 1, the solar cell wing 3 being a forward-swept trapezoidal wing, and the solar cell wing 3 being capable of supplying power to the scramjet electric propulsion system.

[0027] Specifically, to solve the problem of technical defects in the aerodynamic design of how to achieve the balance between thrust and drag for aircraft flying in the upper atmosphere for a long time in the prior art; the aircraft body of the air-breathing aircraft for long-term flight in the upper atmosphere provided by the present invention has an air-breathing electric propulsion system. Based on the aerodynamic characteristics of the upper atmosphere, considering that the thin atmosphere in the upper atmosphere will generate resistance, making it difficult for the aircraft to fly for a long time, the air-breathing electric propulsion system is used to generate thrust to overcome the resistance generated by the thin atmosphere. At the same time, solar cell wings are arranged on the outer side of the aircraft body, and the electric energy of the air-breathing electric propulsion system is provided by the solar cell wings to meet the energy supply requirements; the aircraft body can carry payloads. The air inlet of the air-breathing electric propulsion system is located at the center of the aircraft body and is a through-hole structure. Gas enters the air inlet through a tapered inlet duct, is compressed in an inwardly concave tapered compression duct, then is ionized and accelerated in a cylindrical ionization acceleration duct, and finally is discharged through a tapered outlet duct to generate thrust; the solar cell wings adopt forward-swept trapezoidal wings. The existence of the forward sweep angle and the increase in the taper angle of the tapered inlet duct improve the effective inlet size of the air inlet, which is beneficial for the high-speed and low-density upper atmosphere to enter the air inlet, thereby improving the gas collection performance of the air inlet; after the air inlet collects and compresses the low-density upper atmosphere, the air-breathing electric propulsion system ionizes and accelerates it with the electric energy provided by the solar cell wings to generate thrust, overcoming the atmospheric resistance received by the aircraft, so as to achieve long-term flight.

[0028] In this embodiment, the solar cell wing 3 is a right trapezoid and has a forward sweep angle.

[0029] In view of the long-term flight requirements in the airspace of the upper atmosphere, the present invention proposes the air-breathing aircraft for long-term flight in the upper atmosphere from the perspective of integrated aerodynamic and propulsion design. The outer contour of the aircraft body 1 is cylindrical, and the length and diameter of the aircraft body 1 can be selected according to engineering needs.

[0030] In this embodiment, the air-breathing aircraft for long-term flight in the upper atmosphere is applicable to the upper atmosphere height range of 100 km to 300 km, and the flight speed is in the suborbital speed range, that is, about 7760 m / s.

[0031] Optionally, the front end radius of the tapered inlet duct 4 is equal to the outer contour radius of the aircraft body 1.

[0032] Specifically, the front end of the tapered inlet duct 4 tapers from the outermost periphery of the aircraft body 1, so that the front end radius of the tapered inlet duct 4 can reach the maximum value, that is, equal to the radius of the aircraft body 1, which can not only maximize the size of the gas inlet, but also better ensure the strength and stiffness of the front end of the aircraft body 1 compared with a cylindrical inlet duct.

[0033] The length of the tapered conical inlet duct 4 can be determined according to the size of the aircraft.

[0034] In this embodiment, for the air-breathing aircraft designed for long-term flight in the upper atmosphere, the diameter D of the aircraft body 1 is 1.5 m. Then, the front radius R of the tapered conical inlet duct 4 b is 0.75 m, the chord length a at the root of the solar cell wing 3 is 2 m, and the length L of the tapered conical inlet duct 4 i and the rear radius R i are 0.2 m and 0.55 m respectively.

[0035] Optionally, the cone angle of the tapered conical inlet duct 4 differs from the sweep angle of the forward-swept trapezoidal wing by -10° to 10°.

[0036] Specifically, the cone angle of the tapered conical inlet duct 4 is coordinated with the sweep angle of the forward-swept trapezoidal wing, and the difference between them is relatively small, forming a relatively smooth angle transition. This can increase the effective inlet size of the inlet duct 2, facilitate the entry of the high-speed and low-density upper atmosphere into the inlet duct 2, and thus improve the gas collection performance of the inlet duct 2.

[0037] Optionally, the cross-sectional profile of the concave tapered compression duct 5 is circular arc-shaped, and the front radius of the concave tapered compression duct 5 is equal to the rear radius of the tapered conical inlet duct 4.

[0038] Specifically, the circular arc-shaped cross-sectional profile of the duct can improve the compression performance and collection performance of the inlet duct 2. The front end of the concave tapered compression duct 5 is connected to the rear end of the tapered conical inlet duct 4 in a broken line shape.

[0039] The length of the concave tapered compression duct 5 can be determined according to the flight altitude and the size of the aircraft.

[0040] In this embodiment, for the air-breathing aircraft designed for long-term flight in the upper atmosphere, the flight altitude is 180 km, and the length L of the concave tapered compression duct 5 c and the rear radius R e are 0.88 m and 0.32 m respectively.

[0041] Optionally, the radius of the cylindrical ionization acceleration duct 6 is 25% to 75% of the rear radius of the tapered conical inlet duct 4.

[0042] Specifically, the cylindrical ionization acceleration duct 6 adopts a relatively large radius, which can eliminate the large-scale recirculation in the concave tapered compression duct 5, facilitate the entry of gas from the concave tapered compression duct 5 into the cylindrical ionization acceleration duct 6, and improve the gas collection performance of the inlet duct 2.

[0043] The length of the cylindrical ionization acceleration duct 6 can be determined according to the size of the aircraft.

[0044] In this embodiment, the length L of the cylindrical ionization acceleration duct 6 e is 0.5 m.

[0045] Optionally, the radius of the front end of the gradually expanding conical outlet duct 7 is equal to the radius of the cylindrical ionization acceleration duct 6.

[0046] Specifically, the length of the gradually expanding conical outlet duct 7 can be determined according to the size of the aircraft.

[0047] In this embodiment, the length L of the gradually expanding conical outlet duct 7 o and the rear end radius R o are 0.1 m and 0.36 m respectively.

[0048] Optionally, the front end of the root of the forward-swept trapezoidal wing is flush with the front end of the aircraft body 1.

[0049] Specifically, while the cone angle of the gradually shrinking conical inlet duct 4 is coordinated with the forward sweep angle of the forward-swept trapezoidal wing, the front end of the root of the forward-swept trapezoidal wing is flush with the front end of the aircraft body 1, so that a relatively smooth transitional connection is formed between the leading edge of the forward-swept trapezoidal wing and the gradually shrinking conical inlet duct 4, which is beneficial to improving the air collection performance.

[0050] Optionally, the rear end of the root of the forward-swept trapezoidal wing extends beyond the rear end of the aircraft body 1.

[0051] Specifically, the chordwise length of the root of the forward-swept trapezoidal wing is greater than the length of the aircraft body 1, and the rear end of the root of the forward-swept trapezoidal wing extends backward to the outside of the rear end of the aircraft body 1, so that the center of mass of the entire aircraft is behind the center of pressure, improving the pitch and yaw static stability of the aircraft.

[0052] In this embodiment, the length L of the aircraft body 1 is 1.683 m.

[0053] Optionally, a pair of solar cell wings 3 are symmetrically arranged on the outside of the aircraft body 1.

[0054] The chordwise length of the root of the solar cell wing 3, the chordwise length at the wing tip position, and the spanwise length can all be determined according to the flight altitude and the size of the aircraft.

[0055] In this embodiment, there are two solar cell wings 3, which are arranged symmetrically on both sides of the aircraft body 1; the chordwise length b at the wing tip position of the solar cell wing 3 is 4 m, and the span w is 4 m.

[0056] Optionally, the forward-swept trapezoidal wing is a flat plate structure, and the thickness of the forward-swept trapezoidal wing is 20 mm to 40 mm.

[0057] Specifically, in order to reduce the aerodynamic drag and ensure the structural strength, the thickness of the solar cell wing 3 should be as small as possible, and a thickness of 20 mm to 40 mm is sufficient.

[0058] The air-breathing vehicle for long-term flight in the upper atmosphere needs to meet the following two conditions during long-term flight in the upper atmosphere: 1) From the perspective of force balance, the thrust generated by the propulsion system can overcome the aerodynamic drag, that is, the thrust and drag are balanced (thrust-drag balance); 2) From the perspective of energy balance, the electric energy provided by the solar cell wing 3 is sufficient to supply the propulsion system, that is, the ratio of the thrust to the power of the propulsion system (thrust-power ratio) is within the normal range.

[0059] To evaluate the feasibility of the air-breathing vehicle for long-term flight in the upper atmosphere in this embodiment, taking the atmospheric environment at a flight altitude of 180 km as an example, the direct simulation Monte Carlo (DSMC) method is used to simulate the internal and external flows of the air-breathing vehicle for long-term flight in the upper atmosphere to obtain the gas pressure distribution, gas mass flow rate, and aerodynamic drag. The gas-solid interaction is the Maxwell model with an accommodation coefficient of 0.5. The volume fraction of nitrogen molecules in the incoming flow component is 0.4829, the volume fraction of oxygen atoms is 0.4820, and the volume fraction of oxygen molecules is 0.0351. The specific incoming flow parameter values are as follows: velocity u ∞ is 7760 m / s, the angle of attack α is is 0°, the temperature T ∞ is 790.07 K, and the density ρ ∞ is 5.198×10 -10 kg / m 3 .

[0060] The average gas pressure in the cylindrical ionization acceleration duct 6 of the air-breathing electric propulsion system given by the DSMC simulation is 0.0232 Pa, and the gas mass flow rate through the duct is m fr = 2.07×10 -6 kg / s. The total drag on the air-breathing vehicle for long-term flight in the upper atmosphere, including the external contour drag of the vehicle body 1, the internal flow drag of the inlet 2, and the drag of the solar cell wing 3, is F = 80.51 mN. The average gas pressure in the cylindrical ionization acceleration duct 6 is much greater than the pressure threshold of 0.005 Pa for gas ionization, ensuring a high gas ionization efficiency. To estimate the thrust, assume that the ionization efficiency or the working fluid utilization rate is η= 72.27%, the neutral gas is ionized and accelerated to v out = 40 km / s and discharged. Thus, the thrust generated by the air-breathing electric propulsion system T is: .

[0061] Substituting the ionization efficiency, mass flow rate, and exhaust velocity, the thrust can be obtained as: T = 80.51 mN.

[0062] Therefore, the thrust generated by the air-breathing electric propulsion system is exactly equal to the total resistance received by the aircraft, achieving thrust-drag balance.

[0063] Next, continue to evaluate whether the thrust-power ratio of the air-breathing electric propulsion system is within the normal range. In this embodiment, the area of the solar cell wing 3 is 24 m 2 , and the energy density of the cell wing is 150 W / m 2 . Therefore, the solar power obtained by the aircraft is 3.6 kW, and the thrust-power ratio of the air-breathing electric propulsion system is 22.36 mN / kW. Currently, the thrust-power ratio of the air-breathing electric propulsion system can reach 30 mN / kW. Therefore, the thrust-power ratio of this scheme is within the normal range.

[0064] Based on the above evaluations of the average gas pressure inside the air-breathing electric propulsion system, thrust-drag balance, and thrust-power ratio, the following conclusion is obtained: The air-breathing aircraft for long-term flight in the upper atmosphere in this embodiment achieves thrust-drag balance under the condition of limited energy supply. That is, the thrust generated by the air-breathing electric propulsion system through the electric energy supplied by the solar cell wing 3 can exactly overcome the aerodynamic resistance received by the entire aircraft, realizing the long-term flight of the aircraft in the upper atmosphere, and thus promoting the development and utilization of this airspace in the upper atmosphere.

[0065] Embodiment 2 and Embodiment 3 As Figure 4 and Figure 5 shown, respectively show the size conditions of the solar cell wing 3 when the size of the aircraft body 1 in Embodiment 2 and Embodiment 3 is the same as that in Embodiment 1; in Embodiment 2, the root chord length a of the solar cell wing 3 is 2 m, the chord length b at the wing tip position is 4 m, and the span w is 3 m; in Embodiment 3, the root chord length a of the solar cell wing 3 is 2.5 m, the chord length b at the wing tip position is 4.5 m, and the span w is 4 m. The area of the solar cell wing 3 in Embodiment 2 is 18 m 2 , and the energy density of the cell wing is 150 W / m 2, so the solar power obtained by the aircraft is 2.7 kW, the thrust-to-power ratio of the air-breathing electric propulsion system is 26.74 mN / kW, the ionization efficiency is 64.87%, and the total drag force on the aircraft is 72.21 mN. In the third embodiment, the area of the solar cell wing 3 is 28 m 2 , and the energy density of the cell wing is 150 W / m 2 , so the solar power obtained by the aircraft is 4.2 kW, the thrust-to-power ratio of the air-breathing electric propulsion system is 20 mN / kW, the ionization efficiency is 75.39%, and the total drag force on the aircraft is 83.99 mN. By comparison, if the ionization efficiency of the air-breathing electric propulsion system is low, a smaller area of the solar cell wing 3 can be used, and the thrust-to-power ratio is higher at this time; if the ionization efficiency of the propulsion system is high, a larger area of the solar cell wing 3 can be used, and the thrust-to-power ratio is lower at this time.

[0066] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An air-breathing aircraft for long-term flight in the upper atmosphere, characterized in that, Comprising: An aircraft body, the aircraft body having an air-breathing electric propulsion system, the outer contour of the aircraft body being cylindrical, an air inlet being provided at the central position of the aircraft body, the air inlet including a tapered conical inlet duct, a concave tapered compression duct, a cylindrical ionization acceleration duct, and a tapered conical outlet duct arranged in sequence from front to back; Solar cell wings, the solar cell wings being provided on the outside of the aircraft body, the solar cell wings being forward-swept trapezoidal wings, and the solar cell wings being capable of supplying power to the air-breathing electric propulsion system.

2. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, wherein The front end radius of the tapered conical inlet duct is equal to the outer contour radius of the aircraft body.

3. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that, The cone angle of the tapered conical inlet duct differs from the forward sweep angle of the forward-swept trapezoidal wing by -10° to 10°.

4. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that, The cross-sectional contour of the concave tapered compression duct is circular arc-shaped, and the front end radius of the concave tapered compression duct is equal to the rear end radius of the tapered conical inlet duct.

5. The air-breathing vehicle for long-term flight in the upper atmosphere according to claim 1, characterized in that, The radius of the cylindrical ionization acceleration duct is 25% to 75% of the rear end radius of the tapered conical inlet duct.

6. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that, The front end radius of the tapered conical outlet duct is equal to the radius of the cylindrical ionization acceleration duct.

7. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that, The front end of the root of the forward-swept trapezoidal wing is flush with the front end of the aircraft body.

8. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 7, characterized in that, The rear end of the root of the forward-swept trapezoidal wing extends beyond the rear end of the aircraft body.

9. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, wherein A pair of the solar cell wings are symmetrically arranged on the outside of the aircraft body.

10. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that, The forward-swept trapezoidal wing is a flat plate structure, and the thickness of the forward-swept trapezoidal wing is 20 mm to 40 mm.

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