An air-breathing ramjet engine with water injection afterburner

Abstract

This invention relates to an air-breathing ramjet engine employing water injection afterburner, comprising: an engine body (1), a fuel injection unit (2), and a water injection unit (3); the engine body (1) includes: a concave combustion chamber (11); the fuel injection unit (2) is connected upstream of the concave combustion chamber (11), and the water injection unit (3) is connected downstream of the concave combustion chamber (11); the nozzle (31) in the water injection unit (3) is embedded in the downstream side wall of the concave combustion chamber (11), wherein the nozzle (31) orifice faces the downstream direction of the concave combustion chamber (11) and is set at an acute angle to the mainstream direction of the engine body (1).

Description

Technical Field

[0001] This invention relates to the field of air-breathing ramjet engines, and more particularly to an air-breathing ramjet engine employing water injection for afterburner. Background Technology

[0002] As the core power component of hypersonic vehicles, the performance of the air-breathing ramjet engine determines the key technical indicators of the entire system, such as Mach number and range. The operation of a regenerative cooling engine is highly complex. It utilizes the physical and chemical heat sinks of kerosene to absorb heat from the engine walls, thus providing structural thermal protection. High-temperature gasified kerosene is injected downstream of the concave flame stabilizer, where the cracked small-molecule fuel undergoes a violent chemical reaction with the high-enthalpy incoming flow. Therefore, the engine thrust is strongly dependent on the injection strategy, engine configuration, and cooling system, and is also closely related to flight parameters.

[0003] In traditional approaches, increasing the fuel / air equivalence ratio is a simple and direct way to improve system performance, enhancing the combustion chamber's work capacity by increasing the amount of fuel involved in the chemical reaction and releasing heat. Fuel consumption should be minimized while ensuring thrust performance meets requirements. To meet engine thermal protection requirements, there is a lower limit to the kerosene flow rate used for cooling, ensuring the wall temperature does not exceed the material's temperature resistance limit. Increasing the kerosene flow rate effectively reduces the wall temperature and allows more cracked kerosene to be injected into the combustion chamber for chemical reactions. As the overall equivalence ratio gradually increases, more heat is released during combustion, eventually leading to thermal blockage in the reaction zone due to the adverse pressure gradient. Therefore, simply increasing fuel flow to increase thrust will inevitably encounter bottlenecks, as the engine's operating range is limited by both cooling and blockage. To further improve the overall performance of the thrust unit, optimization of each subsystem is necessary, including cavity configuration, surface expansion, and coupling schemes between wall injection and the cavity. Nevertheless, the space for increasing thrust using the above methods is very limited, and it is still impossible to break through the technical bottleneck of the system itself in principle. There is an urgent need to explore more effective new thrust enhancement schemes.

[0004] In the aviation industry, a technology is used to increase thrust by injecting water into the engine. This is specifically divided into two main categories: liquid-jet afterburning and staged combustion afterburning. Its primary application is in aero engines, where water is introduced solely as an additional working fluid, and thrust is increased through the expansion of the water. However, considering the weight of the water itself, the actual increase in thrust is relatively limited. Furthermore, exceeding a certain critical flow rate can significantly reduce combustion efficiency or even cause engine shutdown, which is highly detrimental to the combustion organization and normal operation of the engine. Summary of the Invention

[0005] The purpose of this invention is to provide an air-breathing ramjet engine that uses water injection for thrust increase, and to provide a method for increasing thrust of an air-breathing ramjet engine by water injection, thereby solving the problem that the introduction of water alone in the prior art can easily lead to reduced combustion efficiency or even engine shutdown.

[0006] To achieve the above-mentioned objectives, the present invention provides an air-breathing ramjet engine employing water injection afterburner, comprising: an engine body, a fuel injection unit, and a water injection unit;

[0007] The engine body includes: a concave combustion chamber;

[0008] The fuel injection unit is connected upstream of the concave combustion chamber, and the water injection unit is connected downstream of the concave combustion chamber.

[0009] The nozzle in the water spray unit is embedded in the downstream side wall of the concave combustion chamber, wherein the nozzle orifice faces the downstream direction of the concave combustion chamber and is set at an acute angle to the mainstream direction of the engine body.

[0010] According to one aspect of the invention, the concave combustion chamber has a catalyst coating at least partially disposed on the inner wall downstream of the nozzle.

[0011] According to one aspect of the invention, the catalyst coating is a nickel-based catalyst coating.

[0012] According to one aspect of the invention, the thickness of the catalyst coating is 5 mm to 10 mm.

[0013] According to one aspect of the invention, the nozzle is tilted at an angle of 30° to 45° relative to the mainstream direction of the engine body.

[0014] According to one aspect of the present invention, the water spraying unit further includes: a water storage tank, a first electric pump connected to the water storage tank, a flow meter connected to the first electric pump, a first cooling channel connected to the flow meter, and a first control valve and a second control valve connected to the first cooling channel;

[0015] The first control valve is used to control the connection and disconnection with the nozzle, and the second control valve is used to control the connection and disconnection with the external environment;

[0016] The first cooling channel is provided in the side wall upstream of the concave combustion chamber for cooling the upstream portion of the concave combustion chamber.

[0017] According to one aspect of the present invention, the water spray unit further includes: a temperature sensor, a first pressure sensor, a second pressure sensor, and a control unit;

[0018] The control unit is connected to the temperature sensor, the first pressure sensor, and the second pressure sensor, respectively.

[0019] The temperature sensor and the first pressure sensor are located at the outlet of the first cooling channel for connecting the first control valve and the second control valve.

[0020] The second pressure sensor is mounted on the concave combustion chamber.

[0021] According to one aspect of the present invention, the control unit in the water spray unit controls the on / off sequence of the first control valve and the second control valve based on the output signals of the temperature sensor, the first pressure sensor and the second pressure sensor; wherein, when the signals output by the temperature sensor, the first pressure sensor and the second pressure sensor all meet a preset threshold, the control unit controls the first control valve to open and controls the second control valve to close; otherwise, the control unit controls the first control valve to close and controls the second control valve to connect with the external environment.

[0022] According to one aspect of the present invention, the fuel injection unit includes: a fuel tank, a second electric pump connected to the fuel tank, a second cooling channel connected to the second electric pump, and a fuel nozzle connected to the second cooling channel;

[0023] The fuel nozzle is embedded upstream of the concave combustion chamber;

[0024] The second cooling channel is provided in the concave sidewall and downstream sidewall of the concave combustion chamber for cooling the concave portion and downstream portion of the concave combustion chamber.

[0025] According to one aspect of the present invention, a technical solution is proposed to increase thrust performance by injecting high-temperature cooling water downstream of a concave flame stabilizer. This differs from the method in aero engines that relies solely on water expansion for work. Instead, it utilizes the heat absorption and cooling capacity of water and the ability of water vaporization to enhance fuel-air mixing. It fully leverages the chemical reaction between high-temperature water and carbon in the combustion gas, as well as the thrust generated by the water's own expansion, to effectively increase the engine's thrust gain while ensuring that the combustion chamber does not shut down.

[0026] According to one aspect of the present invention, the water injection position is designed to be downstream of the concave flame stabilizer, which has a limited impact on the flame stabilization capability of the air-breathing engine while helping to achieve thrust increase through water injection.

[0027] According to one aspect of the present invention, the technical solution of the present invention is very simple, making full use of the internal energy of high-temperature and high-pressure water to do work; and under high-temperature conditions, water and carbon in the exhaust gas undergo a replacement reaction, which is beneficial to further improve the combustion efficiency of fuel. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the structure of an air-breathing ramjet engine according to one embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram illustrating the operation sequence of a water spray unit according to an embodiment of the present invention. Detailed Implementation

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0031] In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" express orientations or positional relationships based on the orientations or positional relationships shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on the present invention.

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the embodiments of the present invention are not limited to the following embodiments.

[0033] like Figure 1 As shown, according to one embodiment of the present invention, an air-breathing ramjet engine employing water injection afterburner includes: an engine body 1, a fuel injection unit 2, and a water injection unit 3. In this embodiment, the engine body 1 is a hollow cylindrical body, specifically including: a concave combustion chamber 11. In this embodiment, the fuel injection unit 2 is connected upstream of the concave combustion chamber 11, and the water injection unit 3 is connected downstream of the concave combustion chamber 11.

[0034] In this embodiment, the nozzle 31 in the water spray unit 3 is embedded in the downstream side wall of the concave combustion chamber 11, wherein the nozzle 31 has its nozzle orifice facing the downstream direction of the concave combustion chamber 11 and is set at an acute angle to the mainstream direction of the engine body 1.

[0035] By employing the above-mentioned configuration, the method of injecting high-temperature and high-pressure water downstream of the flame stabilizer in the combustion chamber fully utilizes the ability of water to chemically react with the small amount of carbon produced by pyrolysis under high-temperature conditions and to expand and do work, effectively improving the maximum thrust limit of the air-breathing ramjet engine and further extending the range of hypersonic vehicles.

[0036] like Figure 1 As shown, according to one embodiment of the present invention, a catalyst coating is at least partially provided on the inner wall of the concave combustion chamber 11 downstream of the nozzle 31. In this embodiment, the catalyst coating is applied to the inner wall of the concave combustion chamber 11 downstream of the nozzle 31. In this embodiment, the coating area of ​​the catalyst coating can be set according to the spray area of ​​the nozzle 31. For example, the catalyst coating can be applied to all circumferential sidewalls of the concave combustion chamber 11 downstream of the nozzle 31, or it can be applied to a portion of the inner wall of the concave combustion chamber 11 (e.g., the inner wall embedded in the nozzle 31) that can contact the water sprayed by the nozzle 31. In this embodiment, the catalyst coating is a nickel-based catalyst coating.

[0037] By applying a nickel-based catalyst coating to the downstream wall of nozzle 31, the above-mentioned configuration effectively ensures that high-temperature water reacts rapidly with carbon particles in the combustion chamber under high-temperature catalytic conditions, thereby improving combustion efficiency and thrust.

[0038] like Figure 1 As shown, according to one embodiment of the present invention, the thickness of the catalyst coating is 5 mm to 10 mm. In this embodiment, the coating thickness of the catalyst coating can be constant, or the thickness can be adjusted according to the distance from the nozzle 31 (e.g., gradually thickening or gradually thinning).

[0039] By setting the catalyst coating within the aforementioned thickness range, the high-speed scouring of the wall surface by the gas can effectively prevent coating consumption.

[0040] like Figure 1 As shown, according to one embodiment of the present invention, the nozzle 31 is tilted at an angle of 30° to 45° relative to the mainstream direction of the engine body 1.

[0041] By setting the nozzle 31 at an angle of 30° to 45° to the mainstream direction, its normal penetration depth is effectively reduced, and the momentum loss of the engine during operation is also effectively reduced, which is beneficial to ensuring the operating efficiency and stability of the present invention.

[0042] The purpose of the above settings is to maintain a low normal velocity, so that water does not need to enter the mainstream area of ​​the combustion chamber excessively. It is needed to play an expansion role and a role in the catalytic reforming hydrogen production reaction near the wall. This design can effectively increase the contact opportunities between the injected water and the catalyst on the wall.

[0043] like Figure 1 As shown, according to one embodiment of the present invention, the water spray unit 3 further includes: a water storage tank 32, a first electric pump 33 connected to the water storage tank 32, a flow meter 34 connected to the first electric pump 33, a first cooling channel 35 connected to the flow meter 34, and a first control valve 36 and a second control valve 37 connected to the first cooling channel 35. In this embodiment, the first control valve 36 is used to control the on / off connection with the nozzle 31, and the second control valve 37 is used to control the on / off connection with the external environment. In this embodiment, both the first control valve 36 and the second control valve 37 are high-temperature valves.

[0044] In this embodiment, the first cooling channel 35 is provided in the side wall upstream of the concave combustion chamber 11 to cool the upstream portion of the concave combustion chamber 11.

[0045] like Figure 1 As shown, according to one embodiment of the present invention, the water spray unit 3 further includes: a temperature sensor 3a, a first pressure sensor 3b, a second pressure sensor 3c, and a control unit 3d. In this embodiment, the control unit 3d is connected to the temperature sensor 3a, the first pressure sensor 3b, and the second pressure sensor 3c respectively; wherein, the temperature sensor 3a and the first pressure sensor 3b are disposed in the first cooling channel 35 for connecting the outlet positions of the first control valve 36 and the second control valve 37, while the second pressure sensor 3c is disposed on the concave combustion chamber 11. In this embodiment, the temperature sensor 3a is a K-type thermocouple.

[0046] like Figure 1 As shown, according to one embodiment of the present invention, the control unit 3d in the water spray unit 3 controls the on / off sequence of the first control valve 36 and the second control valve 37 based on the output signals of the temperature sensor 3a, the first pressure sensor 3b, and the second pressure sensor 3c; wherein, see Figure 2 As shown, when the signals output by the temperature sensor 3a, the first pressure sensor 3b, and the second pressure sensor 3c all meet the preset threshold, the control unit 3d controls the first control valve 36 to open and controls the second control valve 37 to close. Otherwise, the control unit 3d controls the first control valve 36 to close and controls the second control valve 37 to connect with the external environment.

[0047] Specifically, in the air-breathing ramjet engine of the present invention, before the start-up phase t0, the concave combustion chamber 11 is prone to oscillation or even stalling. During this process, the signals collected by temperature sensor 3a, first pressure sensor 3b, and second pressure sensor 3c are all unstable. Therefore, the control unit 3d controls the first control valve 36 to close and the second control valve 37 to directly discharge water that has not yet reached temperature equilibrium into the environment outside the engine, avoiding problems such as engine failure to switch operating conditions, and effectively ensuring the stable operation of the present invention during the start-up phase. As the engine continues to run, the control unit 3d continuously transmits signals through temperature sensor 3a, first pressure sensor 3b, and second pressure sensor 3c. The second pressure sensor 3c monitors the water temperature and pressure output from the first cooling channel 35, as well as the pressure in the concave combustion chamber 11. After the flame establishes a stable state in the concave combustion chamber 11 (i.e., after time t0), the temperature and pressure signals collected by the corresponding temperature sensor 3a, the first pressure sensor 3b, and the second pressure sensor 3c also become stable and can reach the preset threshold. At this time, the control unit 3d closes the second control valve 37 and opens the first control valve 36, thereby realizing the high temperature and high pressure water generated by the first cooling channel 35 being sprayed downstream of the concave combustion chamber 11 at a 45° angle to the mainstream direction (i.e., the downstream wall of the concave combustion chamber 11).

[0048] like Figure 1 As shown, according to one embodiment of the present invention, the fuel injection unit 2 includes: a fuel tank 21, a second electric pump 22 connected to the fuel tank 21, a second cooling channel 23 connected to the second electric pump 22, and a fuel nozzle 24 connected to the second cooling channel 23. In this embodiment, the fuel nozzle 24 is embedded upstream of the concave combustion chamber 11. The second cooling channel 23 is provided in the concave sidewall and downstream sidewall of the concave combustion chamber 11 for cooling the concave portion and downstream portion of the concave combustion chamber 11.

[0049] According to this invention, water, being a stable molecule with high specific heat, does not suffer from problems such as coking and carbon buildup at high temperatures. High-temperature, high-pressure water is injected along the wall into the downstream of the concave flame stabilizer, utilizing the physical and chemical properties of small-molecule water to improve the engine's thrust-to-specific-impulse ratio. High-temperature, high-pressure water vapor is injected into the downstream of the concave combustion chamber; under the pressure difference, the small-molecule working fluid rapidly expands, converting internal energy into kinetic energy. In the supersonic airflow, the flame stabilizing base is mainly located within the concave cavity and jet wake; water injection from its downstream position has little impact on the flame stabilization process, thus preventing significant combustion attenuation or global flameout. Conversely, the vaporization process of water under high-temperature conditions enhances the mixing of fuel and air, and water molecules also undergo a displacement reaction with carbon in the exhaust gas to generate hydrogen, thus promoting the downstream combustion process to some extent.

[0050] According to one embodiment of the present invention, the engine body 1 further includes: an air intake duct connected upstream of the cavity combustion chamber 11, and a tailpipe connected downstream of the cavity combustion chamber 11. Since the air intake duct, tailpipe, etc., all adopt existing structures, they will not be described in detail here.

[0051] The above description is merely an example of a specific solution of the present invention. For any devices and structures not described in detail herein, it should be understood that they are implemented using common devices and methods already available in the art.

[0052] The above description is merely one embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A water-jet afterburning air-breathing ramjet engine, characterized in that, include: Engine body (1), fuel injection unit (2) and water injection unit (3); The engine body (1) includes: a concave combustion chamber (11); The fuel injection unit (2) is connected upstream of the concave combustion chamber (11), and the water injection unit (3) is connected downstream of the concave combustion chamber (11). The nozzle (31) in the water spray unit (3) is embedded in the side wall downstream of the concave combustion chamber (11), and at least part of the inner side wall of the concave combustion chamber (11) downstream of the nozzle (31) is provided with a nickel-based catalyst coating with a thickness of 5 mm to 10 mm; wherein, the nozzle (31) is directed downstream of the concave combustion chamber (11), and the nozzle (31) is tilted at an angle of 30° to 45° relative to the mainstream direction of the engine body (1); The water spray unit (3) further includes: a water storage tank (32), a first electric pump (33) connected to the water storage tank (32), a flow meter (34) connected to the first electric pump (33), a first cooling channel (35) connected to the flow meter (34), a first control valve (36) and a second control valve (37) connected to the first cooling channel (35). The first control valve (36) is used to control the opening and closing of the nozzle (31), and the second control valve (37) is used to control the opening and closing of the external environment; The first cooling channel (35) is provided in the side wall upstream of the concave combustion chamber (11) for cooling the upstream part of the concave combustion chamber (11).

2. The air-breathing ramjet engine according to claim 1, characterized in that, The water spray unit (3) also includes: a temperature sensor (3a), a first pressure sensor (3b), a second pressure sensor (3c), and a control unit (3d). The control unit (3d) is connected to the temperature sensor (3a), the first pressure sensor (3b), and the second pressure sensor (3c), respectively. The temperature sensor (3a) and the first pressure sensor (3b) are disposed in the first cooling channel (35) for connecting the outlet positions of the first control valve (36) and the second control valve (37); The second pressure sensor (3c) is disposed on the concave combustion chamber (11).

3. The air-breathing ramjet engine according to claim 2, characterized in that, The control unit (3d) in the water spray unit (3) controls the on / off sequence of the first control valve (36) and the second control valve (37) based on the output signals of the temperature sensor (3a), the first pressure sensor (3b), and the second pressure sensor (3c). When the signals output by the temperature sensor (3a), the first pressure sensor (3b), and the second pressure sensor (3c) all meet the preset threshold, the control unit (3d) controls the first control valve (36) to open and controls the second control valve (37) to close. Otherwise, the control unit (3d) controls the first control valve (36) to close and controls the second control valve (37) to connect with the external environment.

4. The air-breathing ramjet engine according to claim 3, characterized in that, The fuel injection unit (2) includes: a fuel tank (21), a second electric pump (22) connected to the fuel tank (21), a second cooling channel (23) connected to the second electric pump (22), and a fuel nozzle (24) connected to the second cooling channel (23). The fuel nozzle (24) is embedded upstream of the concave combustion chamber (11); The second cooling channel (23) is provided in the concave sidewall and downstream sidewall of the concave combustion chamber (11) for cooling the concave part and downstream part of the concave combustion chamber (11).

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