Skeleton composite fuel and ramjet

Abstract

The present application relates to the technical field of ramjet propulsion and energetic materials, and discloses a skeleton composite fuel and a ramjet engine, which comprises a continuous combustible metal skeleton and an oxygen-deficient combustible filling phase, and the mass of the continuous combustible metal skeleton accounts for 50%-90% of the total mass of the fuel; the continuous combustible metal skeleton is used for forming a defined space, serving as a structural bearing unit and participating in a combustion reaction, and the oxygen-deficient combustible filling phase refers to a mixture that cannot maintain stable and complete combustion by itself under the condition of no external oxidizing medium; the oxygen-deficient combustible filling phase is filled in the defined space of the continuous combustible metal skeleton to form a closed structure or a quasi-closed structure that is not connected to the inside and outside of the matrix, and then the combustion reaction interface is located on the surface of the fuel during the working process. The fuel metal content can be improved, the unity of structural bearing and controllable reaction interface can be realized, and problems such as low metal content and difficulty in realizing effective coupling combustion with external oxidizing medium can be solved.

Description

Technical Field

[0001] This invention relates to the field of ramjet propulsion and energetic materials technology, and in particular, to a skeleton composite fuel and a ramjet engine. Background Technology

[0002] Ramjet engines utilize oxidizing media in the environment to achieve thrust output without relying on their own oxidizer or with only a small amount of oxidizer, making them one of the important power forms in the field of high-speed propulsion. As the core functional unit of this device, the energy characteristics, mechanical properties, and matching characteristics with the flow of the oxidizing media directly determine the overall performance of the device.

[0003] In existing technologies, common solid fuels or composite propellants are typically produced by mechanically mixing, casting, and curing polymer-based binders, solid oxidants (such as ammonium perchlorate), and metallic fuel particles (such as aluminum powder). Due to limitations in the rheological properties of the mixture and the curing process conditions, the content of metallic fuel in these fuels is usually difficult to increase significantly, generally not exceeding 20% ​​of the total mass, thus limiting the potential for improving the overall energy density of the fuel. Simultaneously, the mechanical properties of these fuels mainly depend on the organic polymer binder. During long-term operation in high-temperature, high-speed airflow environments, the binder is prone to pyrolysis, ablation, or softening, leading to a decrease in structural integrity, and even cracking, erosion, or morphological instability, making it difficult to meet the requirements for long-term, high-reliability operation.

[0004] To improve the combustion performance and structural stability of solid propellant systems, existing technologies attempt to introduce a skeletal structure within the fuel. For example, a skeletal network composed of fibers made of highly thermally conductive materials (such as copper or aluminum) is arranged within the propellant grain to enhance internal heat conduction and regulate the burning rate. However, the skeletal structure in this approach mainly consists of embedded fibers or filaments, accounting for a small percentage of the system's mass. Its function is primarily as a heat conduction pathway to regulate the combustion process, rather than participating in the energy release reaction as the main fuel. Furthermore, this propellant system still relies on its own oxidizer for combustion, making it a typical self-oxygenated solid propellant. Its combustion reaction occurs within the fuel itself and does not involve active coupling with an external oxidizing medium.

[0005] Another technical solution proposes constructing a three-dimensional metal skeleton filled with a composite material structure containing an oxidant component, aiming to achieve a relatively complete oxidation reaction within the material. This type of structure is a typical "self-oxygen-supplying" combustion system, where the reaction products tend to be in a state of complete combustion, which is not conducive to subsequent secondary reactions with external oxidizing media. Furthermore, this type of structure has a high proportion of oxidant, making it unsuitable for ramming operation modes that rely on external oxidizing media and have specific requirements for fuel oxygen-deficient characteristics.

[0006] Therefore, existing technologies generally suffer from the following technical problems and contradictions: On the one hand, there is a desire to significantly increase the metal content in solid fuels to improve energy density, but this is hampered by traditional mixing and molding processes, making it difficult to achieve breakthroughs in metal content. On the other hand, fuels need sufficient structural load-bearing capacity to adapt to harsh working environments, while their combustion reaction must be effectively coupled with externally introduced oxidizing media, rather than undergoing rapid internal oxidation. Existing solutions using embedded fiber skeletons or high-oxidant fillings struggle to achieve a good balance between high metal content, high structural strength, and compatibility with external oxidizing media for coupled combustion. Summary of the Invention

[0007] This invention provides a skeleton composite fuel and a ramjet engine. By constructing a closed or semi-closed fuel structure consisting of a continuous combustible metal skeleton and an oxygen-deficient combustible filling phase, it can significantly increase the metal content of the fuel while achieving a unity of structural load-bearing capacity and controllable reaction interface. This solves the technical problems of low metal content, insufficient structural strength, and difficulty in achieving effective coupling combustion with external oxidizing media in existing ramjet engines.

[0008] According to one aspect of the present invention, a composite fuel with a skeleton is provided, comprising a continuous combustible metal skeleton and an oxygen-deficient combustible filling phase, wherein the mass of the continuous combustible metal skeleton accounts for 50%-90% of the total mass of the fuel; the continuous combustible metal skeleton is used to form a defined space, serve as a structural load-bearing unit, and participate in the combustion reaction; the oxygen-deficient combustible filling phase refers to a mixture that cannot maintain stable and complete combustion on its own under conditions without an external oxidizing medium; the oxygen-deficient combustible filling phase fills the defined space of the continuous combustible metal skeleton, forming a closed or quasi-closed structure in which the interior and exterior of the matrix are not interconnected, thereby ensuring that the combustion reaction interface is located on the fuel surface during operation.

[0009] Furthermore, the mass fraction of the solid oxidant in the oxygen-deficient combustible packing phase is no more than 5%.

[0010] Furthermore, the mass fraction of solid oxidant in the oxygen-deficient combustible packing phase is no more than 2%; or the oxygen-deficient combustible packing phase does not contain solid oxidant.

[0011] Furthermore, the oxygen-deficient combustible filler phase, by mass parts, comprises the following components: 40%-80% polymer binder, 10%-40% combustible component, 0-5% oxidant, and 0-10% functional additives.

[0012] Furthermore, the polymer binder employs at least one of an inert polymer binder and an energetic polymer, wherein the inert polymer binder includes HTPB and / or PBAN.

[0013] Furthermore, the combustible component includes metallic fuel, wherein the metallic fuel is at least one of aluminum powder, magnesium powder, aluminum alloy powder, or magnesium alloy powder; and / or the combustible component includes non-metallic fuel, wherein the non-metallic fuel is at least one of boron powder, boron carbide powder, or carbon powder.

[0014] Furthermore, the continuous combustible metal skeleton adopts an integrated three-dimensional continuous structure; the geometric structure of the continuous combustible metal skeleton adopts at least one of the following: lattice structure, honeycomb structure, regular porous structure or irregular porous structure.

[0015] Furthermore, the continuous combustible metal skeleton is composed of a periodic and / or non-periodic array of structural units, and the structural units adopt at least one of rods, blocks or ribs; the size range of the structural units is 0.1mm-10mm.

[0016] Furthermore, different spatial regions of the continuous combustible metal skeleton have different structural parameters to form a gradient structure in the combustion direction and / or airflow direction.

[0017] Furthermore, an interface layer is provided between the continuous combustible metal skeleton and the oxygen-deficient combustible filling phase to enhance the bonding performance; the thickness of the interface layer is 1μm-100μm, and the interface layer is an oxide film, coating or chemically modified layer.

[0018] Furthermore, at least one through channel is provided on the continuous combustible metal skeleton. The through channel is used to guide the flow of external oxidizing medium and to form a combustion reaction interface on the channel wall. The through channel can be a single-channel structure or a multi-channel structure.

[0019] Furthermore, the fuel structure consisting of a continuous combustible metal skeleton and an oxygen-deficient combustible filler can be in the shape of a column, a block, or a tube.

[0020] Furthermore, the continuous combustible metal skeleton is prepared by additive manufacturing, powder metallurgy sintering, foam template replication, or metal component connection.

[0021] According to another aspect of the invention, a ramjet engine is also provided, comprising the aforementioned skeleton composite fuel.

[0022] The present invention has the following beneficial effects: 1. Significantly increased fuel metal content and improved energy density: By constructing a continuous combustible metal skeleton, the metal is transformed from a discrete filler into a continuous matrix. Its mass proportion is no longer limited by the physical limitations of traditional mixing processes, but depends on the structural design and preparation feasibility of the skeleton, thus providing a structural basis for a fundamental improvement in energy density; the mass fraction of metal components in fuel is increased to 50%-90%, achieving a breakthrough in metal content.

[0023] 2. Integrated high-strength structural load-bearing and main fuel function: The continuous combustible metal skeleton is a three-dimensional continuous load-bearing structure that runs through the entire fuel. Before combustion, the continuous combustible metal skeleton serves as a structural load-bearing unit, providing the main mechanical support. During combustion, the continuous combustible metal skeleton participates in the reaction as a metallic fuel. It abandons the traditional technology's separation of organic binders (providing strength) and metallic fuel particles (providing energy) in terms of function and materials, and solves the problem of mechanical property degradation caused by the dilution of the binder phase under high metal content. The continuity of the continuous combustible metal skeleton ensures the effective transfer of force and heat, avoiding the overall structural collapse caused by local failure. While possessing high energy, the fuel itself has excellent structural integrity, stiffness, and strength, and can withstand high temperature, high-speed gas erosion, and complex force and thermal loads.

[0024] 3. Forced external combustion interface, perfectly adapted to the working mechanism of ramjet engines: The oxygen-deficient combustible filling phase fills the limited space of the continuous combustible metal skeleton, forming a closed or quasi-closed structure in which the inside and outside of the matrix are not connected. This physically blocks the direct and continuous penetration channels of the external oxidizing medium into the fuel, making it impossible for the combustion reaction to occur spontaneously and completely inside the fuel. The reaction must rely on external heat input (ignition) and oxidant diffusion, thus being forcibly controlled at the interface between the fuel and the oxidizing medium (i.e., the fuel surface). This conforms to the working mechanism of ramjet engines, which is that "fuel produces rich combustion products under oxygen-deficient conditions, and then undergoes secondary combustion with the subsequently introduced external oxidizing medium." From the perspective of fuel structure design, this ensures the matching with the engine combustion organization. The combustion of fuel is strictly limited to the surface (end-face combustion) or the preset inner channel wall (inner channel diffusion combustion), realizing controllable and efficient coupled combustion with the external oxidizing medium.

[0025] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the high-metal-content skeleton composite fuel in the end-face combustion mode according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the continuous combustible metal skeleton in a high-metal-content skeleton composite fuel according to a preferred embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the application of a high-metal-content skeleton composite fuel in end-face combustion mode according to a preferred embodiment of the present invention. Figure 4 This is a schematic diagram of the structure of the high metal content skeleton composite fuel in the internal channel combustion mode according to a preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the continuous combustible metal skeleton in a high-metal-content skeleton composite fuel according to a preferred embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the application of a high-metal-content skeleton composite fuel in an internal channel combustion mode according to a preferred embodiment of the present invention.

[0027] Legend: 1. Continuous combustible metal skeleton; 2. Oxygen-deficient combustible filling phase; 3. Combustion end face; 4. Combustion-rich products; 5. Afterburning zone; 6. External oxidizing medium. Detailed Implementation

[0028] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below. Unless otherwise stated, the raw materials and reagents used in the following embodiments are commercially available or can be prepared by known methods.

[0029] The skeleton composite fuel of this embodiment includes a continuous combustible metal skeleton 1 and an oxygen-deficient combustible filler phase 2. The continuous combustible metal skeleton 1 accounts for 50%-90% of the total fuel mass. The continuous combustible metal skeleton 1 is used to form a defined space, serve as a structural load-bearing unit, and participate in the combustion reaction. The oxygen-deficient combustible filler phase 2 refers to a mixture that cannot maintain stable and complete combustion on its own under the condition of no external oxidizing medium 6. The oxygen-deficient combustible filler phase 2 fills the defined space of the continuous combustible metal skeleton 1, forming a closed or quasi-closed structure in which the inside and outside of the matrix are not connected, so that the combustion reaction interface is located on the fuel surface during the working process. In the skeleton composite fuel of this invention, in traditional fuels, metal particles are dispersed as fillers in an organic binder matrix, and the content is limited by the rheological properties of the mixing system and the curing process. This invention constructs a continuous combustible metal skeleton 1, transforming the metal from a discrete filler into a continuous matrix. The metal's mass percentage is no longer limited by the physical constraints of traditional mixing processes, but rather depends on the structural design and fabrication feasibility of the skeleton, thus providing a structural foundation for a fundamental improvement in energy density. It increases the mass fraction of metal components in the fuel to 50%-90%, achieving a breakthrough in metal content. The continuous combustible metal skeleton 1 is a three-dimensional continuous load-bearing structure that runs through the entire fuel. Before combustion, the continuous combustible metal skeleton 1 serves as a structural load-bearing unit, providing the main mechanical support. During combustion, the continuous combustible metal skeleton 1 participates in the reaction as metallic fuel. It abandons the traditional model of separating the organic binder (providing strength) and the metallic fuel particles (providing energy) in terms of function and materials, solving the problem of mechanical property degradation caused by the dilution of the binder phase under high metal content. The continuity of the continuous combustible metal skeleton 1 ensures effective force and heat transfer, avoiding overall structural collapse due to local failure. While possessing high energy, the fuel itself has excellent structural integrity, stiffness, and strength, capable of withstanding high temperatures, high-speed combustion gas erosion, and complex force and thermal loads. The oxygen-deficient combustible filling phase 2 fills the confined space of the continuous combustible metal skeleton 1, forming a closed or quasi-closed structure in which the interior and exterior of the matrix are not connected. This physically blocks the direct and continuous penetration channels of the external oxidizing medium 6 into the fuel interior, making it impossible for the combustion reaction to occur spontaneously and comprehensively inside the fuel. The reaction must rely on external heat input (ignition) and oxidant diffusion, thus being forcibly controlled at the interface between the fuel and the oxidizing medium (i.e., the fuel surface). This conforms to the working mechanism of the ramjet engine, which is that "the fuel produces fuel-rich products 4 under oxygen-deficient conditions, and then undergoes secondary combustion with the subsequently introduced external oxidizing medium 6." This ensures the matching of the fuel structure design with the engine combustion organization. The combustion of the fuel is strictly limited to the surface (end-face combustion) or the pre-set inner channel wall (inner channel diffusion combustion), achieving controllable and efficient coupled combustion with the external oxidizing medium 6.The continuous combustible metal skeleton 1 with a high metal content is the material and structural basis for achieving both ultra-high energy and ultra-high strength. The two are of the same origin and are interdependent, and there is no contradiction between energy and strength as in traditional schemes. The closed or semi-closed structure forces the interfacial combustion mode, while the oxygen-deficient combustible filling phase 2 itself cannot maintain complete combustion. This ensures that even at high temperatures, the reaction inside the fuel is incomplete, mainly generating fuel-rich intermediate products. This creates the necessary conditions (providing combustibles) and sufficient conditions (controlling the reaction location) for secondary combustion at the interface and downstream with the external oxidizing medium 6. The combination of the two ensures the consistency between the fuel working mode and the requirements of the ramjet engine from both the physical structure and chemical reaction characteristics. This invention relates to a composite fuel with a skeleton, which combines a continuous combustible metal skeleton 1 with an oxygen-deficient combustible filling phase 2 to form a specific closed structure. This represents a synergistic innovation in both material systems and macrostructure, overcoming the technical bottleneck of traditional solid fuels that struggle to balance metal content, structural strength, and combustion mode control. It not only achieves a leap in metal fuel content and overall energy density but also endows the fuel with inherently high structural reliability. Furthermore, it locks the combustion mode from the design stage into controlled surface combustion that matches the external oxidizing medium 6, fundamentally making the fuel characteristics compatible with the working nature of ramjet engines. This provides a novel and well-founded technical path to address the long-term demand for high-performance fuels. Preferably, the continuous combustible metal skeleton 1 accounts for 60%-85% of the total fuel mass.

[0030] In this embodiment, the mass fraction of solid oxidant in the oxygen-deficient combustible filling phase 2 is no more than 5%; this ensures that the fuel cannot achieve complete and stable combustion without an external oxidizing medium, thus forcing its operating mode to rely on and couple with an external oxidizing medium; it further consolidates the operating mode in which the combustion reaction is confined to the outer surface of the fuel or the wall of a pre-set channel, avoiding uncontrollable deep or volumetric combustion caused by internal oxidant residues or migration; it reduces the risk of accidental ignition or deflagration of the fuel during preparation, storage, transportation, and processing, and improves its long-term chemical compatibility and physical stability; it promotes a more reasonable segmented distribution of the fuel's energy release process in space (from the combustion interface to the afterburner) and time, which helps to organize more efficient and stable combustion. More specifically, the core feature of a ramjet engine is the use of an oxidizing medium in the environment (such as air). Ideally, the fuel should be in an oxygen-deficient state in the initial reaction stage, producing high-temperature combustion gas rich in combustible components (combustible product 4), which then undergoes sufficient secondary combustion with the intake air in the afterburner to release all energy. By controlling the solid oxidant content in the oxygen-deficient combustible filling phase 2 to a very low level (≤5%) or even zero, the possibility of self-oxygenated complete combustion within the fuel is suppressed from a chemical composition perspective. This forces the fuel's ignition and initial decomposition reaction to rely on external ignition energy, and the reaction products are inevitably chemically unbalanced fuel-rich mixtures. This creates the necessary fuel source and reaction driving force for subsequent secondary combustion with external oxidants. In conjunction with the closed or quasi-closed structure formed by the continuous combustible metal skeleton 1, the extremely low or no solid oxidant in the oxygen-deficient combustible filling phase 2 ensures that even if a very small amount of external oxidizing medium 6 diffuses into the interior through micropores, the lack of sufficient local oxidant makes it difficult to maintain continuous combustion reaction propagation. This eliminates the possibility of combustion waves developing deep into the fuel interior, ensuring that the combustion process strictly follows the interface retreat mode from the surface to the interior. This mode achieves stable flame residence, controllable combustion surface retreat rate, and uniform gas generation in the ramjet engine combustion chamber. Solid oxidants (such as perchlorates and nitrates) are typically highly sensitive and chemically active components in energetic material systems. Significantly reducing or completely eliminating solid oxidants directly reduces the fuel's sensitivity to external stimuli (such as friction, impact, static electricity, and thermal shock); it also avoids potential long-term, slow side reactions between strong oxidants and metallic framework materials or other combustible components, thus improving the chemical stability of the entire composite fuel system.Under low solid oxidant content, the oxygen-deficient combustible filler phase 2 mainly undergoes thermal decomposition or incomplete reaction upon heating. This process absorbs or releases some heat, providing the necessary thermal environment for the subsequent melting, gasification, and reaction of the metal skeleton, and generating gaseous or easily reacting intermediate products. A large amount of the heat of oxidation reaction is reserved for release during the secondary combustion stage in the combustion chamber with the fuel-rich products 4 and sufficient external oxidizing medium 6. This two-stage energy release mode of "first decomposing and gasifying to generate fuel, then focusing on oxidation and heat release" is more in line with the air mixing and combustion organization characteristics of the ramjet engine combustion chamber, which is beneficial to improving combustion efficiency and specific impulse performance. Preferably, the mass fraction of solid oxidant in the oxygen-deficient combustible filler phase 2 is no more than 2%; or the oxygen-deficient combustible filler phase 2 does not contain solid oxidant.

[0031] In this embodiment, the oxygen-deficient combustible filler phase 2, by mass parts, comprises the following components: 40%-80% polymer binder, 10%-40% combustible component, 0-5% oxidant, and 0-10% functional additives. The high polymer binder content of 40%-80% ensures that the oxygen-deficient combustible filler phase 2 has good processability and molding ability, enabling it to fully fill and tightly adhere to the complex voids of the continuous combustible metal skeleton 1, forming a dense and complete composite structure. The polymer binder decomposes or burns when heated, providing a heat source and gaseous products for the initial reaction of the fuel. Before curing, the polymer binder (such as hydroxyl-terminated polybutadiene, hydroxyl-terminated polyether, etc.) is usually a liquid or flowable prepolymer, facilitating integration with the continuous combustible metal skeleton 1 through processes such as casting and injection molding. The composite of the combustible metal skeleton 1; after curing, its high content ensures that the oxygen-deficient combustible filler phase 2 itself has sufficient strength and toughness, and can form a firm chemical or physical bond with the surface of the continuous combustible metal skeleton 1, ensuring the integrity of the composite fuel; during the working process, the polymer binder is the main mass component and initial reactant of the oxygen-deficient combustible filler phase 2, and its pyrolysis or oxygen-deficient combustion behavior directly determines the initial gas generation rate, composition and heat release, providing the necessary thermal atmosphere and possible active free radicals for the subsequent continuous reaction of the continuous combustible metal skeleton 1. Combustible components (such as fine metal powder, boron powder, hydrocarbons, etc.) with a content of 10%-40% can be used as high-energy additives to supplement energy density, adjust the overall heat of combustion and reaction temperature of oxygen-deficient combustible filler phase 2, and affect the composition and activity of the generated fuel-rich products 4. The introduction of combustible components can increase the volumetric energy density of oxygen-deficient combustible filler phase 2 without significantly increasing the oxidant. Different combustible components have different reaction kinetic characteristics (such as ignition temperature, heat of combustion, and reaction rate). By selecting their types and adjusting their proportions, they can be matched and synergistically used with the decomposition / combustion behavior of the polymer binder, thereby controlling the overall ignition sensitivity, burning rate, and initial gas temperature and composition of oxygen-deficient combustible filler phase 2 within a wider range to better adapt to different working conditions (such as ignition energy and inflow conditions). For example, adding highly reactive metal powder can reduce ignition difficulty and increase the initial reaction intensity.The oxidant content is limited to an extremely low range of 0-5%, which stoichiometrically ensures that the oxygen-deficient combustible filler phase 2 cannot maintain a stable and complete combustion reaction on its own, forcing it to rely on an external oxidizing medium 6 to complete sufficient oxidation. This low oxidant content provides limited local heat of oxidation in specific micro-regions (such as near the interface of the continuous combustible metal skeleton 1) to promote interface bonding or the propagation of the initial reaction. As a fine-tuning agent for combustion performance, it ensures that the overall oxygen balance of the oxygen-deficient combustible filler phase 2 is significantly negative (oxygen-deficient), so that even at high temperatures, the combustion reaction of the oxygen-deficient combustible filler phase 2 is incomplete. Its main products are incomplete combustion products rich in combustible gases, metal vapors, carbon particles, etc., i.e., fuel-rich products 4. This is completely consistent with the mechanism of ramjet engines, which require fuel to generate high-temperature fuel-rich gas for secondary combustion with subsequent air. The extremely low oxidant content also suppresses the possibility of combustion developing into the interior of the oxygen-deficient combustible filler phase 2 to the greatest extent, consolidating the working mode in which the combustion reaction is confined to the fuel surface. Functional additives, with a content of 0-10%, enable precise control of the oxygen-deficient combustible filler phase 2 for specific performance requirements (such as process regulation, combustion stability, burning rate regulation, mechanical modification, and anti-aging). Functional additives are a key means of fine-tuning performance. For example, plasticizers can improve the process rheology of the uncured system, burning rate regulators (such as catalysts and inhibitors) can finely control the ignition delay and burnout rate of the oxygen-deficient combustible filler phase 2, stabilizers can improve long-term storage performance, and bonding agents can enhance the interfacial bonding strength between the oxygen-deficient combustible filler phase 2 and the continuous combustible metal skeleton 1. Through small-scale, targeted addition, the overall performance of the oxygen-deficient combustible filler phase 2 can be optimized without fundamentally changing its oxygen-deficient combustible main characteristics, thereby improving the fuel's reliability, environmental adaptability, and mission adaptability. The polymer binder provides the matrix for the system, and its decomposition products may become gaseous oxidants or dispersion media for combustible components (such as metal powder). Combustible components may have different reaction pathways and rates in the gaseous environment generated by the pyrolysis of the polymer binder. Trace amounts of oxidants may preferentially react with some highly active combustible components, triggering local hot spots and promoting the overall reaction initiation. Functional additives affect the above processes from a physical or chemical perspective. These components work synergistically under specific ratios to ensure that the oxygen-deficient combustible filler phase 2 can achieve the following: In terms of process, it can be uniformly and densely filled and bonded to the continuous combustible metal skeleton 1 to form a stable composite; In terms of operation, it can controllably undergo an oxygen-deficient reaction when heated to generate high-temperature, fuel-rich initial combustion products, creating the necessary conditions for the continuous reaction and subsequent afterburning of the continuous combustible metal skeleton 1.

[0032] In this embodiment, the polymer binder is at least one of an inert polymer binder and an energetic polymer, wherein the inert polymer binder includes HTPB and / or PBAN. By allowing the selection of an inert polymer binder, an energetic polymer binder, or a combination of both, a basic material-level selection space is provided for adjusting the process performance, combustion performance, mechanical properties, and energy characteristics of the oxygen-deficient combustible filler phase 2 and even the entire composite fuel. Different types of polymer binders have vastly different chemical structures and physicochemical properties. Inert polymer binders (such as HTPB, PBAN, etc.) do not contain oxidizing groups or high-energy groups themselves, and their thermal decomposition or combustion mainly depends on external oxidizing media or reactions with other components. Their contribution to calorific value and fuel gas generation is relatively low, making them mainly act as structural skeletons and forming media in the system, which is conducive to achieving a lower oxidation balance and purer fuel gas (mainly composed of combustible pyrolytic small molecules and soot). Energetic polymer binders (such as poly(glycidyl ether) azide (GAP) and nitrate-plasticized polyether (NEPE)) have high-energy groups such as nitro and azide groups bonded to their molecular chains. Upon thermal decomposition, they release additional energy and a large amount of gaseous products, thereby increasing the volumetric energy density and fuel gas production of the oxygen-deficient combustible filler phase 2. By offering both inert and energetic polymer binders as options, targeted selection and compounding can be achieved based on the engine's specific requirements for fuel ignition ease, burning rate, fuel gas temperature, fuel gas molar mass, and mechanical properties, enabling precise control over the reaction intensity and output characteristics of the oxygen-deficient combustible filler phase 2. Inert polymer binders, such as HTPB and PBAN, provide a mature technological foundation, good mechanical properties, and well-defined oxygen-deficient reaction characteristics. This helps ensure the reliability and structural stability of fuel preparation and enhances the fuel's dependence on external oxidizing media. HTPB and PBAN are technically mature binder systems for solid propellants and composite fuels. They have suitable viscosity and rheological properties, making them easy to mix with combustible components and additives. They can also form effective adhesion to the surface of the continuous combustible metal skeleton 1. After curing, they impart good elasticity, toughness, and thermomechanical properties that match the continuous combustible metal skeleton 1 to the oxygen-deficient combustible filler phase 2. As inert polymers, they do not contain intrinsic oxidizing components, and their complete combustion requires sufficient oxygen. In the oxygen-deficient combustible filler phase 2, pyrolysis mainly occurs upon heating, producing combustible gases such as hydrogen, small molecule hydrocarbons, and unsaturated hydrocarbons, as well as residual carbon. Almost no oxidizing gases are produced, which greatly ensures the overall oxygen-deficient chemical characteristics of the oxygen-deficient combustible filler phase 2. This makes its initial reaction more inclined to generate fuel-rich products 4, which is highly compatible with the secondary combustion requirements of ramjet engines and helps reduce the sensitivity of the system. The introduction of energetic polymer binders can effectively increase the chemical energy and fuel production of oxygen-deficient combustible filler phase 2 without increasing (or decreasing) the amount of solid oxidant, thereby improving the energy density and specific impulse potential of the entire composite fuel.Energetic polymer binders contain high-energy chemical bonds (such as N-N and NO bonds), and the energy released during decomposition is much higher than that of inert polymers (CC and CH bonds). They release more heat per unit mass during decomposition or combustion and typically produce large amounts of small molecule gases such as nitrogen, carbon monoxide, and water vapor. Integrating these energy and gas release processes into the initial reaction of the oxygen-deficient combustible filling phase 2 can significantly enhance the heating and gasification of the continuous combustible metal skeleton 1, increase the temperature and pressure of the initial combustion gas, and provide more active intermediates and higher initial enthalpy values ​​for combustion in the subsequent combustion chamber, which is beneficial to improving the overall performance of the engine. In practical applications, a single type or a compound can be selected. For example, using HTPB as the main component to ensure the process and mechanical basis, and compounding some energetic polymers (such as GAP) to moderately increase energy, is a common strategy to achieve performance balance. The combination of the two can improve the energy characteristics of the oxygen-deficient combustible filler phase 2 in a targeted manner while maintaining good processability and structural strength. This selectivity and composability allow the polymer binder to act as a key variable, working synergistically with combustible components, oxidants and functional additives to achieve customized design and optimization of the ignition performance, burning rate, fuel composition, energy release law and mechanical properties of the oxygen-deficient combustible filler phase 2, so as to meet the specific requirements of different thrust curves, working time and environmental conditions for the fuel.

[0033] In this embodiment, the combustible component includes metallic fuel, which is at least one of aluminum powder, magnesium powder, aluminum alloy powder, or magnesium alloy powder; and / or the combustible component includes non-metallic fuel, which is at least one of boron powder, boron carbide powder, or carbon powder. The selected metallic and non-metallic fuel components, such as aluminum, magnesium, boron, and carbon, are all high-energy materials with high calorific value. Introducing them into the oxygen-deficient combustible filler phase 2 can directly and significantly increase the chemical energy density of this phase, thereby improving the overall energy level of the composite fuel. When aluminum, magnesium, and other metallic fuels react with oxidants, they release extremely high heat per unit mass (calorific value), making them key materials for improving the specific impulse of the propulsion system. Boron has one of the highest calorific and volumetric calorific values ​​among all common fuels. Although carbon (such as carbon powder and carbon fiber) has a slightly lower calorific value per unit mass than some metals, it is widely available, stable, and its combustion products are mainly gases (CO, CO2), which helps to increase the number of moles of fuel gas. These components undergo incomplete oxidation or incomplete reaction under oxygen-deficient conditions to generate corresponding metallic / non-metallic oxide particles, suboxides, or elemental vapors. These products will release a large amount of heat energy in subsequent secondary combustion with sufficient external oxidizing media, constituting one of the main sources of high fuel energy output. Different combustible components have different ignition temperatures, reaction kinetics, combustion product phases (gas, liquid, solid), and condensed product particle sizes. By selecting one or more combinations, the ignition sensitivity, burning rate, combustion temperature, and physicochemical state of the oxygen-deficient combustible filler phase 2, as well as the formation of the fuel-rich product 4, can be controlled to adapt to different working conditions. For example, magnesium and its alloy powders have relatively low ignition and combustion temperatures and react rapidly, which helps improve the overall ignition performance and initial reaction intensity of the fuel. Aluminum powder has a high combustion temperature and concentrated heat release, making it a core component for improving energy, but its surface... A dense oxide layer may lead to delayed ignition and incomplete combustion; although boron powder has an extremely high calorific value, it is difficult to ignite and has a long combustion time, which needs to be improved by surface modification or compounding with other components (such as magnesium); carbon powder combustion mainly produces gaseous products, which helps to regulate the composition of the fuel gas and the characteristics of the two-phase flow; combining combustible components with different characteristics can take advantage of their synergistic effects. For example, the rapid exothermic reaction of magnesium can be used to promote the ignition and combustion of aluminum or boron, or the gasification reaction of carbon can be used to absorb heat and regulate the local temperature, thereby achieving active design of the reaction process and output characteristics of the oxygen-deficient combustible filling phase 2 over a wider range.The condensed oxides (such as Al2O3, MgO, B2O3, etc.) generated after the combustion of different metallic or non-metallic fuels vary in terms of melting point, viscosity, surface tension, and particle size distribution. The characteristics of these condensed particles directly affect the combustion efficiency, two-phase flow loss, and possible internal flow channel deposition behavior in the afterburner. The combustion of aluminum powder generates solid Al2O3 particles with a high melting point. They may remain solid in the high-temperature environment of the afterburner. Their particle size and distribution affect the radiation characteristics of the combustion gas and the flow loss in the afterburner / nozzle. The combustion of magnesium powder generates solid MgO, which has similar properties but a lower melting point. Boron powder generates B2O3 under ideal complete combustion. It is liquid at the combustion temperature and is prone to agglomeration and deposition. Under incomplete combustion, it may generate low oxides or elemental boron. By selecting or combining different combustible components, the physicochemical properties of the condensed particles in the fuel-rich product 4 can be controlled, thereby optimizing the two-phase flow characteristics of the combustion products to a certain extent. This is of engineering significance for reducing energy loss and ensuring stable engine operation. As part of the oxygen-deficient combustible filling phase 2, the combustible components function synergistically with the continuous combustible metal skeleton 1, which serves as the main load-bearing structure and main fuel. The high-energy combustible components in the oxygen-deficient combustible filling phase 2 can react rapidly in the initial stage of ignition, providing a stronger initial thermal atmosphere for heating and igniting the continuous combustible metal skeleton 1. The continuous combustible metal skeleton 1 is composed of metals such as aluminum and magnesium or their alloys, while the combustible components in the oxygen-deficient combustible filling phase 2 can contain the same or different metals or non-metals, which can realize the design of the energy distribution of fuel in space. For example, the highly reactive components (such as magnesium) in the oxygen-deficient combustible filling phase 2 can promote the reaction of the skeleton metal (such as aluminum). The products generated after the reaction of the combustible components in the oxygen-deficient combustible filling phase 2 can interact with the combustion products of the metals in the continuous combustible metal skeleton 1, affecting the final morphology and distribution of the condensed phase products.

[0034] In this embodiment, the continuous combustible metal skeleton 1 adopts an integrated three-dimensional continuous structure; the geometric structure of the continuous combustible metal skeleton 1 adopts at least one of the following: lattice structure, honeycomb structure, regular porous structure, or irregular porous structure. The integrated three-dimensional continuous structure ensures that the metal phase forms a continuous, interpenetrating spatial network inside the fuel, rather than isolated and dispersed particles, solving the technical problem of how the metal phase can simultaneously serve as the main structural load-bearing unit while achieving a high metal mass fraction (50%-90%). In traditional mechanical mixing methods, high volume fraction metal particles make it difficult for the binder phase to be fully wetted and coated, and direct contact between particles easily forms stress concentration points, leading to increased material brittleness and reduced strength. The integrated three-dimensional continuous structure of this invention, such as lattice or honeycomb, is itself a topological framework that is continuously extended in three-dimensional space and is made of metal materials. This structure changes the load-bearing function of metal from particle reinforcement to skeleton load-bearing, so that its mechanical properties (such as stiffness, strength and toughness) are mainly determined by the intrinsic properties of the skeleton material and its macroscopic topological configuration. Thus, it can still obtain excellent and designable macroscopic mechanical properties under extremely high metal content, and meet the structural stability requirements under complex force and heat loads. The listed lattice, honeycomb, regular or irregular porous structures share the common feature of having clearly defined internal pores or chambers. These pores or chambers provide a defined filling space for the oxygen-deficient combustible filling phase 2. After filling, adjacent pores are separated by the skeleton solid wall, naturally forming closed or quasi-closed units that are not interconnected. This porous structure, defined by the continuous combustible metal skeleton 1 wall and isolated or partially interconnected, constructs a closed or quasi-closed structure that is not interconnected inside and outside the matrix. Geometrically, it blocks the continuous channel through the fuel body that allows the external oxidizing medium 6 to flow freely. The external oxidizing medium 6 can only contact the outermost surface of the fuel or the pre-set inner channel wall, and cannot penetrate into the fuel interior. Thus, the forced combustion reaction is restricted to the interface, which is suitable for the diffusion combustion or end-face combustion mechanism of ramjet engines. Different types of geometric structures (lattice, honeycomb, porous, etc.) provide rich design dimensions for the comprehensive performance optimization of fuels, and can achieve the best balance between load-bearing capacity, reaction, heat transfer, and flow. Honeycomb and lattice structures are known for their excellent specific strength and specific stiffness, and can achieve the maximum structural efficiency with the least amount of material, while controlling the structural weight while ensuring load-bearing capacity. The geometric characteristics of continuous combustible metal skeleton structures (such as rib or wall thickness, pore shape and size, surface area to volume ratio) directly determine the initial combustion surface area of ​​the fuel and the combustion surface retreat law. Regular structures (such as uniform lattices) help to achieve uniform and predictable combustion surface retreat. Irregular porous structures may provide more complex fluid-structure interaction and combustion characteristics.The continuous combustible metal skeleton 1 is an excellent heat conduction pathway. Its three-dimensional continuous structure enables rapid heat transfer and redistribution within the fuel, helping to balance the temperature between the combustion interface and the non-reactive zone, reducing thermal stress concentration, and potentially transferring heat from the combustion zone to the unburned zone more effectively, thus affecting the steady-state combustion performance of the fuel. The structure of the continuous combustible metal skeleton 1 determines the interface area and bonding morphology with the oxygen-deficient combustible filling phase 2. Complex structures with high specific surface area (such as certain lattices or irregular pores) can increase the contact area between the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2, enhancing the thermal conduction and possible chemical interactions between the two phases, which may affect ignition, burning rate, and combustion stability. The listed regular structures such as lattice and honeycomb are particularly suitable for advanced molding technologies such as additive manufacturing (3D printing), making it possible to accurately and controllably prepare complex three-dimensional continuous combustible metal skeletons 1, ensuring the repeatability of the design and the consistency of the structure. Additive manufacturing technology can build metal components with complex internal three-dimensional interconnected structures layer by layer based on digital models, providing a feasible preparation method for achieving the above-mentioned high-precision and high-performance skeleton structure. This makes it possible to actively control the mechanical properties of fuel and the evolution law of combustion area by finely designing the skeleton topology, which is a key enabling technology for achieving integrated control of "design-manufacturing-performance".

[0035] In this embodiment, the continuous combustible metal skeleton 1 is composed of a periodic and / or aperiodic array of structural units, which are at least one of rods, blocks, or ribs; the size range of the structural units is 0.1mm-10mm. Using rods, blocks, or ribs as basic structural units and arranging them in a periodic or aperiodic array provides a clear and quantifiable design basis for the macroscopic performance of the skeleton. This "unit-array" construction method allows key parameters such as the skeleton's macroscopic equivalent mechanical properties (e.g., equivalent elastic modulus, equivalent strength), porosity, and specific surface area to be theoretically predicted and optimized based on unit geometry, arrangement, and relative density. Rod units can form truss or lattice structures, achieving high specific stiffness and specific strength with low relative density and good internal connectivity. Block units (such as cubes, tetrahedrons, and other polyhedra) are stacked or arrayed to form foam-like or regular porous structures, exhibiting good isotropy and compressive properties. Rib units are used to strengthen plate-like structures or form honeycomb, corrugated, and other structures, providing high load-bearing efficiency in specific directions. By selecting and designing the geometry, connection methods (such as nodal connections of rods, coplanar connections of blocks, and planar extensions of ribs) of these basic units, as well as their periodic (regular repetition) or non-periodic (gradual, random) arrays, the macroscopic anisotropy of the skeleton, the load-bearing path, and the connectivity and shape of the internal pores can be precisely controlled, thereby enabling customized design for specific mechanical loads (such as axial pressure, shear, and vibration) and physical environments (such as thermal fields and flow fields). By limiting the size of the structural units to the range of 0.1mm-10mm, an effective connection is achieved between microscopic material properties and macroscopic fuel component properties, ensuring that the structure remains within the achievable precision range of modern manufacturing technologies (especially additive manufacturing). The lower limit of 0.1mm ensures that the structural units maintain their structural integrity and function under fuel operating conditions (high temperature, oxidation, and possible thermo-mechanical coupling). Metal units with excessively small dimensions (such as micrometers) have a drastically increased specific surface area, which may lead to processing difficulties, surface oxidation, and other problems. Furthermore, they may fail at high temperatures due to rapid melting, sintering, or structural instability, affecting the continuity and load-bearing capacity of the framework. The 0.1mm scale provides the units with sufficient characteristic dimensions to resist surface oxidation. The instability caused by surface effects, defects, or local inhomogeneities can be evaluated using traditional metallurgical or powder metallurgy theories. The upper limit of 10 mm ensures that the continuous combustible metal skeleton 1 has sufficient internal space (pores) to accommodate a sufficient amount of oxygen-deficient combustible filling phase 2, so as to realize its function as an initial reactant and structural binder. At the same time, the unit size of the continuous combustible metal skeleton 1 structure at this scale matches the macroscopic size of the fuel as a whole, which can form an effective three-dimensional continuous load-bearing network. Units that are too large (such as centimeter-level) will make the structure bulky, reduce the specific surface area, and reduce the interfacial bonding area with the oxygen-deficient combustible filling phase 2, which may be detrimental to the heat conduction and synergistic reaction between the two phases, and also reduce the design flexibility.The structural unit's size range of 0.1-10mm is entirely within the capabilities of current mainstream metal additive manufacturing (such as selective laser melting (SLM) and electron beam melting (EBM), precision casting, or three-dimensional weaving, ensuring the precise and controllable preparation of this complex three-dimensional continuous structure. The size and array arrangement of the structural units directly determine the initial geometry of the combustion reaction surface and its evolution during combustion, thus affecting the combustion rate, fuel generation patterns, and combustion stability. The dimensions of the structural units (such as the diameter of the rods, the thickness of the ribs, and the side length of the blocks) determine the characteristic dimensions of the continuous combustible metal skeleton 1 material in the combustion direction, directly affecting the burner surface retreat rate and combustion time of the continuous combustible metal skeleton 1. Periodic arrays typically produce regular and predictable burner surface evolution, which is beneficial for achieving stable thrust output. Non-periodic or gradient arrays may be used to design specific burner surface change patterns, such as achieving increased or decreased burner surface combustion. The size and arrangement of the structural units determine the interfacial area between the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2, affecting not only the thermal coupling and possible chemical interactions between the two phases but also facilitating ignition and the establishment of the initial reaction zone. Preferably, the size range of the structural units is 0.5 mm to 2 mm. Optionally, the volume fraction of the internal confined space of the continuous combustible metal skeleton 1 is preferably 10% to 60% to ensure that the fuel has sufficient reaction interface and heat conduction path while maintaining structural strength.

[0036] In this embodiment, different spatial regions of the continuous combustible metal skeleton 1 have different structural parameters to form a gradient structure in the combustion direction and / or airflow direction. By designing the gradient change of the continuous combustible metal skeleton 1 along the combustion direction, the change law of the fuel exposed surface area (i.e., combustion surface) over time during combustion can be actively controlled, thereby realizing a predetermined program for the change of engine thrust or gas generation rate over time, and meeting the thrust curve requirements of different flight mission profiles; the gas generation rate and thrust of ramjet engines (especially solid fuel ramjet engines) are directly related to the combustion surface area of ​​the fuel. The combustion surface evolution of traditional homogeneous propellants is determined by the initial propellant type, and the control capability is limited. In this invention, by making the continuous combustible metal skeleton 1 exhibit a gradient change of structural parameters (such as structural unit size, porosity, relative density, etc.) in the combustion direction (e.g., from the combustion surface to the unburned area), the law of combustion surface regression can be preset. For example, if the relative density of the continuous combustible metal skeleton 1 gradually increases along the combustion direction, the mass of the continuous combustible metal skeleton 1 per unit length increases, which may lead to an increasing trend in the gas generation rate (increased combustion surface). Conversely, it may achieve reduced combustion (reduced surface combustion) or complex variations. This ability to regulate the combustion surface through structural gradients allows for flexible control of the thrust-time curve solely through fuel design without altering the engine structure. By designing a gradient variation of the continuous combustible metal skeleton 1 along the airflow direction (such as axial or radial in the internal channel of a ramjet engine), the flow field distribution within the channel, the gas jet morphology, and the fuel-oxidizer mixing characteristics can be adjusted, thereby optimizing combustion efficiency and combustion stability. In the internal channel combustion mode, the combustion efficiency of a ramjet engine is highly dependent on the turbulent mixing of fuel-rich gas and high-speed incoming air. The continuous combustible metal skeleton 1 with a gradient structure can serve as a built-in flow or combustion control body. For example, by changing the size, shape, or opening ratio of the pores along the airflow direction, the rate and location of gas release from the wall can be actively controlled, forming a specific gas jet that promotes shearing and mixing with the main airflow. Radially, the gradient structure can be used to adjust the flow characteristics near the wall, control boundary layer development, or guide air penetration towards the wall. Through structural design, local flow field conditions favorable for vortex generation, enhanced turbulent mixing, or flame stabilization can be created in space, thereby improving combustion completeness and stability within the afterburner. In regions of concentrated thermal stress or significant temperature gradients, by designing gradient-based skeleton structural parameters (such as relative density and rib thickness), the local stiffness and thermal conductivity characteristics of these regions can be adjusted to match the thermal expansion behavior of the material, thereby reducing peak thermal stress and preventing fuel structure cracking or spalling caused by thermo-mechanical coupling. During combustion, significant temperature gradients (from the high temperature of the combustion surface to the low temperature of the unburned zone) and thermal expansion mismatches exist within the fuel. Homogeneous structures may generate high thermal stress at the interfaces.By designing gradient structures, such as using a lower relative density (greater porosity) structure in the high-temperature zone near the combustion surface, the equivalent elastic modulus of this region can be reduced, making it more compliant when heated and thus absorbing some thermal strain. Simultaneously, the gradient structure can also regulate the heat flow path, making the temperature distribution more gradual, further reducing the thermal stress level and enhancing the structural durability of the fuel under harsh thermal environments. For example, designing a sparser skeleton at the beginning of the channel to promote rapid ignition and initial combustion, designing a specific pore structure in the middle section to optimize mixing, and adjusting the structure at the end section to control the burnout process can achieve synergistic optimization of energy release and flow field evolution over the entire combustion chamber length. At the same time, this functional gradient design can also take into account the requirements of structural integrity, such as locally reinforcing the structure at fixed support ends or in areas with high thermal loads.

[0037] In this embodiment, an interface layer is provided between the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2 to enhance the bonding performance. The thickness of the interface layer is 1μm-100μm, and the interface layer is an oxide film, coating, or chemically modified layer. The interface layer with a thickness of 1μm-100μm significantly enhances the interfacial bonding strength between the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2, preventing structural integrity damage caused by interface debonding, cracking, or slippage under thermal-mechanical loads, thereby ensuring the structural reliability of the composite fuel during manufacturing, storage, and operation. The continuous combustible metal skeleton 1 (such as aluminum or magnesium alloy) and the oxygen-deficient combustible filling phase 2 (with a polymer binder as the matrix) are two materials with very different physicochemical properties, and their interface is usually a weak point in the structure. Stress concentration is easily generated at the interface under temperature changes (mismatched coefficients of thermal expansion) or mechanical loads. By pre-constructing an interface layer on the metal surface of the continuous combustible metal skeleton 1, the transition of physical and chemical properties from metal to polymer can be achieved. For example, interfacial layers formed through chemical treatments (such as phosphating and anodizing) or physical coatings (such as coupling agents and adhesion promoters) can form strong chemical bonds or physical anchors with the metal substrate. Simultaneously, their surface functional groups or structures exhibit good compatibility or reactivity with the polymer binder, thereby enhancing the interfacial bonding from weaker van der Waals forces or mechanical interlocking to stronger chemical bonds or interpenetrating network structures, effectively transferring and dispersing stress. As a buffer and regulating layer between the two phases, the interfacial layer can alter the physicochemical state of the continuous combustible metal skeleton 1, thus affecting the efficiency of heat transfer from the oxygen-deficient combustible filling phase 2 to the continuous combustible metal skeleton 1 during the initial ignition phase, the initial reactivity of the continuous combustible metal skeleton 1, and the reaction coupling behavior between the two phases. The introduction of the interfacial layer can modulate the thermophysical properties (such as thermal conductivity and emissivity) and chemical properties (such as surface energy, catalytic activity, and oxidation resistance) of the continuous combustible metal skeleton 1 surface. For example, a thin interfacial layer with moderate thermal conductivity (such as certain metal oxide coatings) can improve heat transfer from the oxygen-deficient combustible filler phase 2 to the continuous combustible metal skeleton 1, preventing the continuous combustible metal skeleton 1 from heating too slowly due to excessive interfacial thermal resistance, or from excessive polymer pyrolysis due to overheating of the interface. Some interfacial layers (such as energetic coatings or catalytically active coatings) may react on their own or catalyze the reaction of adjacent substances at specific temperatures, thereby reducing the ignition energy of the continuous combustible metal skeleton 1 and promoting its initial reaction with the decomposition products of the oxygen-deficient combustible filler phase 2, achieving a smoother and more synchronized two-phase combustion transition. Conversely, a dense interfacial layer with good thermal stability (such as an alumina film) can also inhibit premature or excessively rapid reactions of the continuous combustible metal skeleton 1 to a certain extent, thereby regulating the energy release pattern of the entire fuel.A suitable interface layer can protect the continuous combustible metal skeleton 1 (especially reactive metals such as magnesium and aluminum) from environmental corrosion (such as oxidation and moisture absorption) during fuel storage and pre-ignition stages, or inhibit slow side reactions that may occur between it and certain components in the oxygen-deficient combustible filler phase 2 under long-term contact, thus maintaining the performance stability of the fuel. The continuous combustible metal skeleton 1, especially three-dimensional porous structures with a large specific surface area, is prone to reacting with the ambient atmosphere (especially oxygen and water vapor) during preparation and storage, forming an undesirable thick oxide layer or hydroxide on its surface. This can not only reduce its reactivity as fuel but also weaken interfacial bonding. Pre-forming a dense and stable interface layer (such as a passivating oxide film or protective coating of a specific thickness) can act as a physical barrier, preventing or slowing down further corrosion from the environmental medium. Simultaneously, this interface layer can also isolate the continuous combustible metal skeleton 1 from certain corrosive or reactive additives that may be present in the oxygen-deficient combustible filler phase 2, ensuring the long-term chemical compatibility of the fuel system before service. An interface layer with a thickness of 1 μm to 100 μm is used. The lower limit of 1 μm ensures that the interface layer is sufficient to form a continuous cover to achieve basic bonding enhancement and protection functions, while the upper limit of 100 μm avoids the negative impacts that may arise from an excessively thick interface layer. An excessively thick interface layer may become a significant thermal barrier due to its own thermophysical properties (such as low thermal conductivity), hindering heat transfer; it may become a new failure source under thermal stress due to its own mechanical properties (such as brittleness); or it may affect the effective content of the continuous combustible metal skeleton 1 and the energy density of the fuel due to occupying too much volume. A thickness in the range of 1 μm to 100 μm allows the interface layer to function effectively without having unacceptable negative impacts on the overall thermodynamic properties and energy characteristics of the fuel. Optionally, the continuous combustible metal skeleton 1 can be surface-treated to enhance bonding performance.

[0038] In this embodiment, at least one through-channel is formed on the continuous combustible metal skeleton 1. The through-channel guides the flow of the external oxidizing medium 6 and forms a combustion reaction interface on the channel wall. The through-channel can be a single-channel or multi-channel structure. The through-channel pre-set inside the fuel provides a clear flow path for the external oxidizing medium 6 and extends the combustion reaction interface from the outer end face of the fuel to the entire inner wall of the through-channel, thereby achieving a larger initial combustion surface area per unit volume of fuel and promoting the mixing of fuel and oxidant. Ramjet engines rely on the interaction between high-speed airflow and fuel. End-face combustion mode is limited by the end-face area, resulting in a limited combustion surface. By establishing the through-channel, traditional end-face combustion is transformed into internal channel wall combustion. The inner wall of the through-channel forms an extended and continuous combustion reaction interface. High-speed flowing external oxidizing medium 6 flows along the through-channel, where it undergoes intense turbulent diffusion and mixing with the fuel-rich products 4 (from the combustion or pyrolysis of the oxygen-deficient combustible filling phase 2 and the continuous combustible metal skeleton 1) released from the channel wall. Combustion then occurs in the region adjacent to the wall or downstream. This mode significantly increases the contact area and mixing intensity between the fuel and oxidant, facilitating higher combustion rates and more complete energy release. Different configurations, whether single-channel or multi-channel, allow for active control of the airflow velocity, pressure distribution, residence time, and spatial distribution of the combustion surface within the fuel, thereby achieving optimized control of the flow field, temperature field, and combustion process within the combustion chamber. The single-channel structure is simple and has a clear flow path, suitable for fuel configurations with relatively simple combustion organization requirements or long axial dimensions. Its channel diameter is a key adjustment parameter, directly affecting the airflow velocity, pressure drop, and residence time of the combustion gas within the channel, thus influencing combustion efficiency and stability. Multi-channel structures, through multiple interconnected channels, can significantly increase the total internal combustion surface area, thereby achieving a higher total fuel gas generation rate with the same fuel volume. Multi-channel designs (such as star-shaped, wheel-shaped cross-sectional shapes, or honeycomb porous arrays) allow for airflow diversion, enabling more uniform fuel utilization. Different channel sizes, shapes, and arrangements can be designed to match specific flow requirements within the combustion chamber. For example, peripheral channels can be designed for stable combustion, while central channels facilitate the main airflow. Multi-channel structures contribute to more uniform fuel combustion across the combustion chamber cross-section, reducing localized overheating or incomplete combustion areas, and potentially providing better structural symmetry to resist thermal deformation. The presence of through-channels, combined with the closed or quasi-closed matrix structure formed by the continuous combustible metal skeleton 1, further macroscopically reinforces the design principle that the combustion reaction interface is located on the fuel surface, clearly defining the controllable combustion interface on the channel walls.The through-channel wall serves as a clear interface between the fuel entity and the external oxidizing medium flow space. Combustion can only occur at this interface and in the adjacent gas phase region. Because the matrix (continuous combustible metal skeleton 1 and oxygen-deficient combustible filling phase 2) is a closed or quasi-closed structure, the external oxidizing medium cannot penetrate the through-channel wall to enter the fuel interior. Therefore, the combustion reaction is strictly confined to the through-channel wall from the surface inwards. This perfectly aligns with the fundamental principle of ramjet engine combustion, which relies on the interaction between the fuel surface and the high-speed airflow. The geometry of the through-channel directly determines the shape and area of ​​the initial combustion surface, and its evolution is determined by the fuel's retreat along the wall, making the combustion process more predictable and designable. The design of the through-channel can be deeply coordinated with gradient structural features. For example, designing a gradient structure of a continuous combustible metal skeleton 1 along the axial (airflow direction) or radial (from the channel wall to the interior of the substrate) of the through channel can achieve programmed changes in the combustion surface area, gas release rate, or local combustion characteristics, thereby matching the flow field development within the through channel and achieving a better thrust-time curve or combustion efficiency. In a multi-channel structure, different gradient characteristics can also be designed for different channel branches to achieve more complex combustion control logic.

[0039] In this embodiment, the fuel structure, composed of a continuous combustible metal skeleton 1 and an oxygen-deficient combustible filling phase 2, has an external shape that is cylindrical, blocky, or tubular. The overall fuel shape is cylindrical, blocky, or tubular. These simple and regular macroscopic geometric shapes facilitate matching with the internal cavity shape, support structure, mounting interface, and sealing components of the ramjet engine combustion chamber. This ensures that the fuel can be reliably positioned and fixed within the engine, meeting the sealing requirements under operating pressure and preventing gas leakage or cross-flow. The ramjet engine combustion chamber is typically cylindrical or nearly cylindrical. Using a cylindrical (solid or with a central hole) or tubular shape allows for a tight fit between the fuel and the inner wall of the combustion chamber, or reliable installation using specialized fixtures. A blocky shape provides flexibility for integration into combustion chambers of specific shapes or modular propellant designs. These regular shapes facilitate processing, inspection, and dimensional tolerance control, ensuring assembly repeatability and consistency, and forming the basis for engineering applications. Regular contact surfaces also facilitate the arrangement and application of necessary preload or the use of standard sealing structures to withstand operating pressures and isolate gas leakage from undesigned channels. Different fuel shapes directly correspond to and define the main combustion organization modes that fuel may adopt within the engine, and provide macroscopic boundary conditions for the design of features such as internal through channels. Solid cylinders or blocks are adapted to end-face combustion modes, where the combustion reaction mainly occurs on the front face (or rear face, depending on the installation direction). The fuel-rich products 4 are blown into the downstream afterburner chamber to mix and burn with air. Their shape determines the area of ​​the combustion end face 3, which is the main determining factor of the initial combustion surface; block shapes can be used to achieve specific non-axisymmetric combustion chamber layouts. A cylindrical body with a central through-channel, i.e., a tube, is the typical configuration for achieving an internal combustion mode. The tube shape implies the presence of at least one axially continuous channel within it. The inner diameter of the tube defines the initial dimensions of the main airflow channel, while the gap between the outer diameter and the inner wall of the combustion chamber (if any) constitutes the outer channel. This shape naturally divides the combustion organization into a combination of internal channel wall combustion and possible end-face combustion. Multi-channel structures can also be achieved by combining multiple tubes (e.g., honeycomb-like) or by machining multiple parallel channels on a single cylindrical body. The regular shape makes the gas flow path within the combustion chamber (e.g., air intake, fuel mixing, exhaust) clearer and more controllable, facilitating fluid dynamics and combustion process modeling and analysis. Regular geometric shapes are the easiest to manufacture and control. For the composite structure of the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2 of this invention, its final shape can be directly determined by the pre-made shape of the skeleton, or formed by mold constraint and solidification after filling. This simplifies the production process and ensures the consistency of the product. In the non-use stage, fuel units with regular shapes are easier to safely package, fix, store and transport, which meets the high requirements of energetic materials for safety and reliability.Based on these regular shapes, relatively simplified but sufficiently accurate theoretical or numerical simulation models can be established to predict fuel burnout patterns, fuel gas generation rates, internal heat conduction, and mechanical responses, thereby guiding fuel optimization design. The geometry of cylinders, blocks, and tubes possesses symmetry (such as axisymmetry or planar symmetry) and well-defined boundaries, simplifying the mathematical models describing their combustion processes (one-dimensional or two-dimensional burnout), heat conduction (one-dimensional or two-dimensional heat conduction equations), and structural mechanics (such as thick-walled cylinder theory). Based on these models, fuel performance (such as thrust curves, temperature fields, and stress fields) under different sizes and channel configurations can be effectively predicted and compared during the design phase, accelerating design iteration and optimization processes and reducing absolute reliance on expensive and time-consuming full-scale tests.

[0040] In this embodiment, the continuous combustible metal skeleton 1 is prepared using additive manufacturing, powder metallurgy sintering, foam template replication, or metal component connection methods. The four listed preparation methods cover a variety of technical routes from digital additive manufacturing to traditional metallurgy and assembly, providing practical manufacturing means for realizing integrated three-dimensional continuous structures (including lattice, honeycomb, porous, etc.), ensuring the convertibility of this core structural feature from design drawings to physical entities. Additive manufacturing, based on three-dimensional model data, directly forms metal parts through layer-by-layer deposition (such as laser selective melting, electron beam melting). It has unique advantages in realizing complex three-dimensional continuous structures, especially structures with fine lattices, periodic gradients, or internal flow channels. It can almost freely realize the arbitrary arrangement of the aforementioned structural units (rods, blocks, ribs), with high precision, and can integrally form complex fuel skeletons with through channels, making it the preferred process for realizing complex structural designs and functional gradient designs. Powder metallurgy sintering involves filling a mold with metal powder (or a mixture of powder and a pore-forming agent), pressing it into shape, and then sintering it at high temperature to obtain a porous metal body with interconnected or non-interconnected pores. It is particularly suitable for preparing porous frameworks with good isotropy and relatively random or regular pore structures. By controlling the powder particle size, particle size distribution, pressing pressure, and sintering process, the porosity, pore size distribution, and mechanical properties of the framework can be controlled within a certain range. This method is suitable for scenarios where the absolute precision requirements of the structure are relatively relaxed but the demand for large-scale production is high. Foam template replication uses removable templates such as polymer foam as prototypes. A metal layer is coated onto the template through methods such as slurry dipping, melt infiltration, or chemical vapor deposition, and then the template is removed to obtain an open-cell foam metal structure. This method is suitable for preparing irregular porous metal frameworks with high porosity and biomimetic topology. Its structure inherits the network characteristics of the template and usually has excellent specific surface area and connectivity. The process is relatively mature. Metal component connections, achieved through welding, brazing, and mechanical joining, assemble prefabricated simple metal units (such as wires, sheets, and small lattice units) into larger, continuous three-dimensional structures. The advantage lies in flexibility; standardized units can be used to construct large or uniquely shaped skeletons, and connections between different material regions are possible, enabling modular design or functional integration. Different fabrication processes determine the differences in structural precision, mechanical properties, material selection range, fabrication efficiency, and cost of the resulting metal skeletons, allowing for the selection of the most suitable fabrication technology or combination of technologies based on specific fuel performance requirements, production volume, and cost constraints. Additive manufacturing offers the highest precision and can achieve the highest geometric complexity; powder metallurgy and foam replication methods typically struggle to achieve the same level of detail and structural design freedom; the connection method depends on the precision of the prefabricated units and the connection process. Additive manufacturing and powder metallurgy can utilize a wide variety of metal materials (such as titanium alloys, aluminum alloys, stainless steel, and high-melting-point metals), and through process optimization, mechanical properties approaching or even reaching forging levels can be obtained.Material selection for foam replication methods may be limited by the process, while the bonding method requires consideration of whether the performance of the bonding area will become a weak point. Different processes can also lead to different microstructures (such as grain size and defects) within the skeleton, affecting its intrinsic mechanical properties and combustion reactivity. Additive manufacturing is suitable for small-batch, highly complex customized production or R&D; powder metallurgy and foam replication methods may have cost advantages in mass production; bonding methods may be more economical when constructing large or repairable structures. The diversified choice of processes allows this fuel technology to adapt to different stages of needs from R&D verification to large-scale equipment. The preparation process not only determines the macroscopic geometry of the skeleton but also profoundly affects its microstructure and properties, thus affecting the overall performance of the fuel. For example, additive manufacturing may introduce anisotropic microstructures and non-equilibrium phases, affecting the thermal conductivity, mechanical anisotropy, and combustion characteristics of the skeleton. The pore surface state and sintering neck strength of the powder metallurgy skeleton directly affect the quality of its interfacial bonding with the filling phase and its own load-bearing capacity. The surface roughness of the ribs and the distribution of internal defects in the foam replication skeleton will affect its reaction initiation behavior. Therefore, the selection of preparation methods is an integral part of the closed-loop process of fuel performance design and realization.

[0041] The ramjet engine of this embodiment includes the aforementioned skeleton composite fuel. The skeleton composite fuel is adapted to the ramjet engine in different configurations depending on the engine's structure: in end-face combustion mode, the fuel uses the front end face as the primary reaction interface, and high-temperature, fuel-rich products are transported to the subsequent afterburner chamber for secondary combustion with ambient air; in internal channel combustion mode, a through-channel is provided inside the fuel, and the external oxidizing medium flows along the channel, forming a combustion reaction interface on the channel wall; the through-channel can be a single-channel or multi-channel structure to adjust airflow distribution and combustion intensity.

[0042] Combustion method and working process: When fuel operates in a ramjet engine, the combustion reaction is confined to the outer surface of the fuel or the walls of the internal through-channel. In the initial stage of ignition, the oxygen-deficient combustible filling phase is first heated and decomposed or undergoes an incomplete reaction, releasing heat and generating fuel-rich products; subsequently, the continuous combustible metal skeleton participates in the reaction under high temperature and releases heat; the generated fuel-rich products react with the external oxidizing medium entering the combustion zone, forming the main exothermic process.

[0043] Compared with existing technologies, this invention constructs a continuous combustible metal skeleton 1 and introduces an oxygen-deficient combustible filling phase 2, forming an integrated system of structural support and fuel reaction. This not only significantly increases the metal content in the fuel but also changes the combustion control method, transforming combustion from traditional gas combustion to interface-controlled combustion, thus achieving compatibility with the working mechanism of ramjet engines. Because the continuous three-dimensional interconnected combustible metal skeleton 1 serves as the load-bearing body, the fuel maintains overall structural stability under high temperature and high-speed airflow, reducing the problems of cracking, peeling, or erosion common in traditional particulate fuels and improving reliability. By designing the oxygen-deficient combustible filling phase 2 with oxygen deficiency and limiting the oxidant content, the fuel is kept in a fuel-rich state during operation, which is conducive to the generation of fuel-rich products 4 and further reaction with the external oxidizing medium 6, thereby improving energy utilization efficiency. Simultaneously, the fuel has a dense configuration, and no through-flow channels are formed inside the matrix, confining the combustion reaction to the outer surface or through-channel walls. This makes it suitable for end-face combustion or internal channel combustion modes, facilitating compatibility with the airflow organization of ramjet engines. Furthermore, by reducing or eliminating the use of solid oxidizers, the safety of the fuel during preparation and use is improved. In summary, this invention, while increasing the metal content, also considers structural strength and combustion compatibility, thus meeting the fuel requirements of ramjet engines.

[0044] Example 1: like Figure 1 , Figure 2 and Figure 3 As shown, this embodiment provides a high-metal-content composite fuel for ramjet engines suitable for end-face combustion mode. The fuel has a cylindrical, dense solid structure with a diameter of 120 mm and a length of 300 mm, with one end serving as the combustion end face 3. No through-flow channels are provided inside the fuel, and the overall structure is macroscopically airtight, confining the combustion process to the end-face region and gradually returning along the axial direction.

[0045] The fuel is composed of a continuous combustible metal skeleton 1 and an oxygen-deficient combustible filler phase 2. The continuous combustible metal skeleton 1 is an integrated three-dimensional connected lattice structure that runs through the entire fuel volume, forming a continuous force transmission path and simultaneously participating in the reaction as the main fuel. The continuous combustible metal skeleton 1 is made of aluminum-magnesium alloy material, with magnesium accounting for 10% by mass, and is obtained in one step through selective laser melting process, exhibiting good structural integrity and dimensional accuracy.

[0046] Geometrically, the continuous combustible metal skeleton 1 adopts a body-centered cubic lattice. In the region far from the combustion end face 3, the lattice unit size is 5 mm. To meet the requirements for reaction rate regulation during end-face combustion, the skeleton structure is locally refined in the region near the combustion end face 3. Within a range of approximately 50 mm (40 mm-60 mm) from the combustion end face 3, the lattice unit size is reduced to 1.5 mm, thereby increasing the specific surface area and reactivity in this region and achieving spatial regulation of the combustion rate. The overall volume fraction of the continuous combustible metal skeleton 1 is 55%, corresponding to a mass fraction of 75%-80%.

[0047] The oxygen-deficient combustible filler phase 2 is distributed within the structural space enclosed by the continuous combustible metal skeleton 1 and forms close contact with the surface of the continuous combustible metal skeleton 1. The oxygen-deficient combustible filler phase 2 adopts an HTPB-based system, in which HTPB binder accounts for 65%, plasticizer DOS accounts for 15%, aluminum powder accounts for 15%, boron powder accounts for 4%, and 1% iron oxide is added as a catalyst. This system does not contain solid oxidants, and the fuel is in an oxygen-deficient state. Without the participation of an external oxidizing medium 6, it cannot achieve self-sustaining complete combustion.

[0048] Oxygen-deficient combustible filler phase 2 is introduced into the interior of the continuous combustible metal skeleton 1 via a vacuum impregnation process. Specifically, the continuous combustible metal skeleton 1 is first preheated to 60°C to reduce the influence of the filler system's viscosity. Liquid oxygen-deficient combustible filler phase 2 is then injected under a vacuum of less than 100 Pa, allowing it to fully penetrate the skeleton structure. Subsequently, atmospheric pressure is restored, and a staged curing process is performed: curing at 60°C for 48 hours, followed by curing at 80°C for 24 hours. This ensures that the oxygen-deficient combustible filler phase 2 essentially fills the internal space of the continuous combustible metal skeleton 1, forming a stable composite structure. After filling, X-ray CT verification confirms that no through-hole structures have formed within the internal space.

[0049] To improve the interfacial bonding performance between the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2, the metal skeleton is pretreated before filling by holding it at 300°C in air for 30 minutes to form an oxide film with a thickness of 3μm-10μm on the surface of the continuous combustible metal skeleton 1. This oxide film, as an interfacial transition layer, helps to improve the adhesion between the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2, and also improves thermal conductivity and interfacial stability.

[0050] During engine operation, combustion first occurs in the combustion end face region 3. The oxygen-deficient combustible filler phase 2 undergoes pyrolysis or incomplete reaction under heating conditions, releasing heat and generating fuel-rich products 4. Subsequently, the continuous combustible metal skeleton 1 gradually participates in the reaction under high temperature, generating metal droplets and vapor phase products. These products collectively form the fuel-rich product 4, which is transported to the downstream afterburning zone 5. In this zone, it mixes thoroughly with the incoming external oxidizing medium 6 and undergoes secondary combustion, thus completing the main exothermic process. As the reaction continues, the fuel end face stabilizes and returns to a continuous combustion state.

[0051] It should be noted that the structural parameters, material composition and size ratio in this embodiment can be adjusted according to the specific engine operating conditions. For example, different combustion performance requirements can be achieved by changing the skeleton density, filling phase composition or end face structure morphology.

[0052] Example 2: like Figure 4 , Figure 5 and Figure 6 As shown, this embodiment provides a high-metal-content composite fuel for ramjet engines suitable for internal combustion modes. The fuel has an overall tubular structure with an outer diameter of 150 mm and a length of 400 mm. A central main channel with a diameter of 60 mm is provided along its entire length in the axial direction to guide the external oxidizing medium 6 to flow axially. Apart from this central channel, no other through-holes are provided inside the fuel, thus ensuring the overall structural compactness.

[0053] The fuel is also composed of a continuous combustible metal skeleton 1 and an oxygen-deficient combustible filling phase 2. The continuous combustible metal skeleton 1 is an integrated three-dimensional connected structure that runs through the entire structure, forming a stable load-bearing network in space and enclosing a closed or quasi-closed structural space to accommodate the filling phase. The skeleton material is an aluminum-magnesium-boron alloy, with a molar ratio of aluminum, magnesium, and boron of 1:1:4, and it is manufactured integrally using a selective laser melting process. The continuous combustible metal skeleton 1 adopts a Diamond lattice structure.

[0054] To accommodate the airflow scouring and reaction requirements during combustion in the internal channel, the dimensions of the skeleton units in the continuous combustible metal skeleton 1 exhibit a gradient distribution along the radial direction. In the region near the inner wall of the central main channel, the characteristic dimension of the skeleton unit is 2 mm; in the region near the outer side of the fuel, the skeleton unit size gradually increases to 4 mm.

[0055] An oxygen-deficient combustible filler phase 2 is filled within the structural space enclosed by a continuous combustible metal skeleton 1, forming a continuous covering layer on the inner wall of the central channel. The oxygen-deficient combustible filler phase 2 employs an energetic polymer system, comprising 55% GAP, 20% plasticizer BDNPF, 20% boron-magnesium alloy powder, and 1% copper oxide as a catalyst. This system contains no solid oxidant, maintaining its oxygen-deficient characteristics. The filler phase achieves near-complete filling within the skeleton, preventing the formation of interconnected pores within the fuel except for the central channel.

[0056] The filling process employs a combination of casting and vacuum-assisted filling. First, the continuous combustible metal skeleton 1 undergoes vacuum degassing to fully expel gas from the skeleton space. Then, a low-viscosity, oxygen-deficient combustible filling phase 2 is cast, and its uniform distribution within the structural space is promoted through appropriate rotational centrifugation. To ensure a continuous coating layer forms on the inner wall of the central channel, the fuel is rotated at low speed after casting, causing the oxygen-deficient combustible filling phase 2 to form a uniform coating layer with a thickness of 0.2mm-1mm on the channel wall. Subsequently, it is cured at 70℃ for 72 hours to allow the system to fully solidify and form a stable composite structure.

[0057] To further improve the interfacial bonding strength between the continuous combustible metal skeleton 1 and the oxygen-deficient combustible filling phase 2, the surface of the continuous combustible metal skeleton 1 is chemically modified before filling. An interfacial layer with a thickness of 10μm-20μm is formed by spraying a silane coupling agent, thereby forming a chemical bond between the oxygen-deficient combustible filling phase 2 and the continuous combustible metal skeleton 1, and improving the interfacial stability under thermal shock and high-speed airflow scouring conditions.

[0058] During engine operation, such as Figure 6 As shown, the external oxidizing medium 6 flows at high speed along the central channel, and a stable combustion reaction interface is formed on the inner wall of the channel. The oxygen-deficient combustible filling phase 2 first undergoes a pyrolysis reaction under heating conditions, and the continuous combustible metal skeleton 1 subsequently participates in the reaction and gradually melts or vaporizes, with both generating fuel-rich products 4. Inside the channel, a combustion supplement zone 5 is formed between the high-speed flowing external oxidizing medium 6 and the fuel-rich products 4 released from the wall surface, and it continuously develops along the axial direction, thereby establishing a stable diffusion combustion process. As combustion progresses, the inner wall of the channel gradually returns radially, while the continuous combustible metal skeleton 1 always provides continuous structural support, allowing the fuel to maintain its overall integrity under complex thermo-mechanical coupling conditions.

[0059] Experiments and applications show that this structure can achieve stable combustion in the internal channel combustion mode without obvious combustion oscillations or localized flameout, demonstrating good potential for engineering applications.

[0060] Matters not covered in this invention are common knowledge.

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., 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 skeleton composite fuel, characterized in that, It includes a continuous combustible metal skeleton and an oxygen-deficient combustible filling phase, with the continuous combustible metal skeleton accounting for 50%-90% of the total fuel mass; A continuous combustible metal skeleton is used to form a confined space, serve as a structural load-bearing unit, and participate in the combustion reaction. An oxygen-deficient combustible filling phase refers to a mixture that cannot maintain stability and complete combustion on its own under conditions without an external oxidizing medium. The oxygen-deficient combustible filling phase is filled in the confined space of the continuous combustible metal skeleton, forming a closed or quasi-closed structure in which the inside and outside of the matrix are not connected, so that the combustion reaction interface is located on the fuel surface during the working process.

2. The skeleton composite fuel according to claim 1, characterized in that, The mass fraction of solid oxidant in the oxygen-deficient combustible packing phase is no more than 5%.

3. The skeleton composite fuel according to claim 1, characterized in that, The oxygen-deficient combustible packing phase, by mass parts, comprises the following components: 40%-80% polymer binder, 10%-40% combustible components, 0-5% oxidant, and 0-10% functional additives.

4. The skeleton composite fuel according to claim 3, characterized in that, The polymer binder employs at least one of an inert polymer binder and an energetic polymer, wherein the inert polymer binder includes HTPB and / or PBAN.

5. The skeleton composite fuel according to claim 3, characterized in that, The combustible component includes a metallic fuel, wherein the metallic fuel is at least one of aluminum powder, magnesium powder, aluminum alloy powder, or magnesium alloy powder; and / or The combustible component includes non-metallic fuel, which is at least one of boron powder, boron carbide powder, or carbon powder.

6. The skeleton composite fuel according to any one of claims 1 to 5, characterized in that, The continuous combustible metal skeleton adopts an integrated three-dimensional continuous structure; The geometric structure of the continuous combustible metal skeleton adopts at least one of the following: lattice structure, honeycomb structure, regular porous structure, or irregular porous structure.

7. The skeleton composite fuel according to any one of claims 1 to 5, characterized in that, The continuous combustible metal skeleton is composed of a periodic and / or non-periodic array of structural units, and the structural units are at least one of rods, blocks or ribs; The size range of the structural unit is 0.1mm-10mm.

8. The skeleton composite fuel according to claim 7, characterized in that, Different spatial regions of a continuous combustible metal skeleton have different structural parameters to form a gradient structure in the direction of combustion and / or airflow.

9. The skeleton composite fuel according to any one of claims 1 to 5, characterized in that, An interface layer is provided between the continuous combustible metal skeleton and the oxygen-deficient combustible filling phase. The interface layer is used to enhance the bonding performance. The thickness of the interface layer is 1μm-100μm, and the interface layer is made of oxide film, coating or chemical modification layer.

10. The skeleton composite fuel according to any one of claims 1 to 5, characterized in that, At least one through channel is provided on the continuous combustible metal skeleton. The through channel is used to guide the flow of external oxidizing medium and to form a combustion reaction interface on the channel wall. The through passage can be a single-channel structure or a multi-channel structure.

11. The skeleton composite fuel according to any one of claims 1 to 5, characterized in that, The external shape of a fuel structure consisting of a continuous combustible metal skeleton and an oxygen-deficient combustible filler is a column, a block, or a tube.

12. The skeleton composite fuel according to any one of claims 1 to 5, characterized in that, The continuous combustible metal skeleton is prepared by additive manufacturing, powder metallurgy sintering, foam template replication or metal component connection.

13. A ramjet engine, characterized in that, Includes the skeleton composite fuel according to any one of claims 1 to 12.

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