A boron-containing fuel-rich propellant and a method for preparing the same

Abstract

The present application relates to solid fuel-rich propellant for hypersonic ramjet engine, and particularly discloses a boron-containing fuel-rich propellant and a preparation method thereof, which comprises, by mass percentage, 15-24% of a binder system, 28-32% of an oxidizer, 40-50% of composite boron powder, 5-10% of auxiliary metal fuel, and 0.1-2% of a performance regulator; wherein the binder system comprises a plasticizer, and the plasticizer is ethylene glycol perfluorodecanoate. The propellant uses the composite boron powder to replace the ordinary boron powder, the process performance of the propellant is greatly improved, the boron powder content in the propellant is greatly increased, and the energy level of the propellant is effectively improved; meanwhile, the ethylene glycol perfluorodecanoate (FOE) is used to replace the ordinary plasticizer DOS, the phase change energy loss caused by B2O3 generated after the propellant is burned is reduced, and the energy performance of the propellant is further improved.

Description

Technical Field

[0001] This invention relates to the field of fuel-rich propellant technology for solid scramjet engines, specifically to a boron-containing fuel-rich propellant and its preparation method. Background Technology

[0002] Air-breathing cruise vehicles can cruise with power throughout their flight, possessing unique advantages such as fast response speed, strong penetration capability, minimal speed loss during ballistic maneuvers, and high terminal velocity. They represent one of the disruptive development directions for future aircraft. Scramjet engines are one of the bottleneck technologies restricting the development of air-breathing cruise vehicles. Solid scramjet engines not only possess advantages such as high specific impulse and high propulsion efficiency under hypersonic conditions, but also retain the inherent advantages of traditional solid rocket engines, such as simple structure, small size, low cost, high safety and reliability, and good storage and maintenance performance. They can meet the engineering application requirements of aircraft, including low cost, high reliability, strong environmental adaptability, and long-term all-weather operation.

[0003] Solid scramjet engines use solid fuel-rich propellants as their power source, with fuel content reaching 30-50%. Therefore, fuel performance is one of the key factors determining whether the potential superior performance of solid rocket ramjet engines can be fully realized. Boron-rich propellants have a high calorific value and are the preferred propellant for solid scramjet engines. However, boron powder has a high melting and boiling point, making it difficult to melt and vaporize, and has a high ignition temperature (1900K). Furthermore, during the combustion of boron powder, highly viscous boron oxides (B2O3) are produced, covering the surface of the boron powder, making ignition difficult and hindering complete combustion.

[0004] Impurities such as B2O3 and H3BO3 on the surface of boron powder can potentially trigger condensation reactions between hydroxyl-terminated polybutadiene (HTPB) molecules during propellant loading, leading to further polymerization of HTPB. This reaction severely interferes with the propellant loading process for propellants using HTPB as a binder. For example, during the loading of boron-containing fuel-rich solid propellants, the mixing and stirring of boron powder and HTPB can promote the condensation reaction of certain compounds under the influence of H3BO3, forming polymers. The more thorough the stirring, the more polymers are formed, and in severe cases, viscosity issues can lead to propellant failure. To prevent the highly viscous substances on the surface of boron powder from affecting propellant performance, washing is generally used to remove the surface oxide layer. However, due to the chemically active nature of boron powder, it is easily oxidized to form B2O3, which in turn generates highly viscous and non-dense H3BO3 covering the surface of the boron powder. H3BO3 is a non-dense porous structure that adsorbs oxygen and water from the air, leading to further oxidation of the boron powder. Therefore, the method of washing to remove the highly viscous oxide layer on the surface of boron powder cannot completely solve the problem of boron powder oxidation affecting storage performance and causing deterioration of propellant process performance. Furthermore, because the oxide layer on the surface of boron powder is very tightly bonded to the boron powder, the washing method cannot completely remove the oxide layer.

[0005] Impurities such as B2O3 and H3BO3 severely affect process performance, preventing an increase in the boron powder content of the propellant. Previous studies have shown that the boron powder content in propellants should not exceed 30%, and since boron powder is the main energy source in boron-containing propellants, its content affects propellant energy enhancement and limits its application range. To further improve the propellant's energy level and meet the energy performance requirements of solid scramjet engines, it is necessary to further increase the boron powder content to improve the propellant's energy level. CN108892599 A uses metal composite powder as auxiliary fuel, resulting in a high boron powder content and high energy release efficiency. However, subsequent tests revealed that because ordinary boron powder was used, the propellant viscosity and yield value increased rapidly during mixing, making it unsuitable for large engine propellant loading. Summary of the Invention

[0006] To address the aforementioned problems, the first objective of this invention is to provide a boron-rich fuel propellant. This propellant uses composite boron powder instead of ordinary boron powder, which significantly improves the propellant's processing performance, greatly increases the boron powder content in the propellant, and effectively enhances the propellant's energy level. Simultaneously, it uses perfluorodecanoic acid ethylene glycol (FOE) instead of the ordinary plasticizer DOS, reducing the phase transition energy loss caused by the formation of B2O3 after propellant combustion, further improving the propellant's energy performance.

[0007] A second objective of this invention is to provide a method for preparing a boron-rich fuel propellant.

[0008] The first technical solution adopted in this invention is: a boron-containing fuel-rich propellant, comprising the following components by mass percentage:

[0009] Adhesive system: 15-24%;

[0010] Oxidizing agent: 28-32%;

[0011] Composite boron powder: 40-50%;

[0012] Auxiliary metal fuel: 5-10%;

[0013] Performance modifier: 0.1–2%;

[0014] The adhesive system includes a plasticizer, which is ethylene glycol perfluorodecanoate.

[0015] Preferably, the perfluorodecanoic acid glycol ester has a mass percentage content of 3% in the boron-containing rich fuel propellant.

[0016] Preferably, the adhesive system further includes an adhesive and a curing agent;

[0017] The adhesive is hydroxyl-terminated polybutadiene.

[0018] The curing agent is one or more of hexamethylene diisocyanate and isophorone diisocyanate.

[0019] Preferably, the oxidant is ammonium perchlorate and / or potassium perchlorate.

[0020] Preferably, the particle size of the oxidant includes one or more of categories I, III, IV and V, wherein the particle size range of category I is 280 μm to 360 μm, the particle size range of category III is 90 μm to 140 μm, the particle size range of category IV is 5 μm to 15 μm, and the particle size range of category V is 0.5 μm to 2 μm.

[0021] Preferably, the composite boron powder is prepared by a two-stage condensation method using vinylidene fluoride / acrylic alcohol copolymer as the composite agent, polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer as the auxiliary composite agent, and an epoxy resin system as the curing system.

[0022] Preferably, the particle size of the composite boron powder is 1.2 μm to 2.0 μm.

[0023] Preferably, the auxiliary metal fuel includes one or more of magnesium and aluminum, and the particle size of the auxiliary metal fuel is 1μm to 30μm.

[0024] Preferably, the performance modifier is one or more of the following: lecithin, tris[1-(2-methyl)aziridinyl]phosphine oxide, iron acrylate, 3-amino-1,2,4-triazole copper perchlorate, N,N-diphenyl-p-phenylenediamine, N-phenyl-2-naphthylamine, and N-phenyl-N-cyclohexyl-p-phenylenediamine.

[0025] The second technical solution adopted in this invention is: a method for preparing a boron-containing rich fuel propellant as described in the first technical solution, comprising the following steps:

[0026] S1. Weigh each component in a dry environment and set aside for later use;

[0027] S2. Mix the binder system, oxidant, composite boron powder, auxiliary metal fuel, and performance modifier to obtain a slurry;

[0028] S3. Vacuum casting of the slurry and curing in a dry environment to obtain boron-rich fuel propellant.

[0029] The beneficial effects of the above technical solution are as follows:

[0030] (1) To address the problems in existing technologies where the presence of highly viscous substances on the surface of boron powder affects propellant processing performance, leading to deterioration, difficulty in increasing boron powder content, and challenges in energy enhancement, this invention provides a boron-rich fuel propellant. This propellant uses composite boron powder instead of ordinary boron powder. Because the surface of the boron powder is covered by a dense organic layer, air is completely isolated, significantly improving the propellant's processing performance, storage performance, and boron powder content, effectively increasing the propellant's energy level. Furthermore, the presence of fluorine compounds in the composite boron powder that can damage the boron oxide layer effectively improves the propellant's combustion efficiency. However, the presence of boron powder... Combustion generates B2O3 gas, which requires two phase transitions to become solid B2O3. At higher temperatures, B2O3 remains in gaseous form, and the energy from the two phase transitions cannot be released, resulting in insufficient propellant energy release. Fluorine in composite boron powder can break down the boron powder oxide layer and improve the propellant's ignition efficiency, but due to the low coating content and limited fluorine content, its effect on improving propellant energy release efficiency is limited. Therefore, this invention also uses perfluorodecanoic acid ethylene glycol (FOE) to replace the common plasticizer DOS, reducing the phase transition energy loss caused by the generation of B2O3 after propellant combustion, and further improving the propellant's energy performance.

[0031] (2) The boron-rich fuel propellant disclosed in this invention uses fluoride-coated composite boron powder with high mechanical strength, and uses FOE to replace the conventional plasticizer DOS. This can destroy the B2O3 oxide layer generated by the combustion of boron powder and generate BOF gas, thereby reducing the phase change energy loss caused by the combustion of B2O3 in the propellant and improving the combustion efficiency of the propellant.

[0032] (3) This invention replaces ordinary boron powder with composite boron powder, which solves the problem that the boron oxide on the surface of boron powder affects the propellant process and that increasing the boron powder content will lead to the deterioration of the propellant process. This invention increases the boron powder content in boron-rich fuel propellants and improves the energy performance of the propellant.

[0033] (4) The boron-containing rich fuel propellant disclosed in this invention can be used in ramjet engines, which can solve the problem of ramjet engines' demand for high-performance rich fuel propellants, improve the performance level of advanced solid ramjet tactical missile weapons, and has broad application prospects. Attached Figure Description

[0034] Figure 1 This is a schematic flowchart of a method for preparing a boron-rich fuel propellant according to an embodiment of the present invention. Detailed Implementation

[0035] The present invention will be further illustrated below with specific embodiments. It should be noted that those skilled in the art can make several modifications and improvements without departing from the principle of the present invention, and these should also be considered to fall within the protection scope of the present invention.

[0036] The terms “first,” “second,” etc. (if applicable) in the specification and claims are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data used in this way can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that comprises a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0037] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0038] This invention discloses a boron-containing fuel-rich propellant, comprising the following components by mass percentage:

[0039] Adhesive system: 15-24%;

[0040] Oxidizing agent: 28-32%;

[0041] Composite boron powder: 40-50%;

[0042] Auxiliary metal fuel: 5-10%;

[0043] Performance modifier: 0.1-2%.

[0044] The adhesive system comprises an adhesive, a curing agent, and a plasticizer. The adhesive is hydroxyl-terminated polybutadiene (HTPB), the curing agent is one or more of hexamethyl ethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), and the plasticizer is ethylene glycol perfluorodecanoate (FOE) of perfluorocarboxylic acid esters, with a mass percentage content of 3% in the boron-containing fuel-rich propellant.

[0045] During propellant combustion, fluorine can combine with boron and oxygen to form boron fluoride compounds:

[0046] B+F - +O 2- →BOF

[0047] Boron oxyfluoride (BOF) is a gas at room temperature, so there is no heat loss due to phase transition, further improving the combustion efficiency of the propellant. Fluorine in composite boron powder can break down the boron powder oxide layer, improving the propellant's ignition efficiency. However, due to the low content of the coating layer and limited fluorine content, its effect on improving the propellant's energy release efficiency is limited. To further improve the propellant's combustion efficiency, fluorine compounds must be added to reduce the phase transition energy loss caused by the formation of B2O3 after propellant combustion. However, ordinary liquid fluorine compounds have high cohesive energy and strong electronegativity, resulting in poor compatibility with propellant components and making them unsuitable as propellant components. Hydroxyl-terminated fluorinated ether binders containing reactive groups are unusable due to their high viscosity. Therefore, this invention uses perfluorodecanoate (FOE) instead of the common plasticizer diisooctyl sebacate (DOS) to further break down the B2O3 oxide layer, generating BOF gas, reducing the phase transition energy loss caused by the formation of B2O3 during propellant combustion, and improving the propellant's combustion efficiency.

[0048] The oxidant is ammonium perchlorate (AP) and / or potassium perchlorate (KP), and the particle size of the oxidant includes one or more combinations of categories I, III, IV and V, wherein the particle size range of category I is 280 μm to 360 μm, the particle size range of category III is 90 μm to 140 μm, the particle size range of category IV is 5 μm to 15 μm, and the particle size range of category V is 0.5 μm to 2 μm.

[0049] The composite boron powder is prepared by a two-stage condensation method using vinylidene fluoride / acrylic acid copolymer (PVFA) as the composite agent, polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer (PANE) as the auxiliary composite agent, and an epoxy resin system as the high-strength coating and curing system. The particle size is 1.2 μm to 2.0 μm.

[0050] Because the composite boron powder is coated with PVFA, the combustion efficiency of the propellant is further improved, and the propellant can still maintain efficient and stable combustion at low pressure. Because the boron powder is coated with epoxy resin, the structural regularity of the boron powder is greatly improved. There is no boron oxide on the surface of the propellant that would cause process deterioration. The boron powder content is greatly increased, and the total fuel content in the propellant can reach more than 50%.

[0051] The auxiliary metal fuel includes one or a combination of magnesium (Mg) and aluminum (Al), and the particle size of the auxiliary metal fuel is 1 μm to 30 μm.

[0052] The performance modifier is one or more of the following: lecithin, tris[1-(2-methyl)aziridinyl]phosphine oxide (MAPO), iron acrylate (FeAA), 3-amino-1,2,4-triazole copper perchlorate (ACP), N,N-diphenyl-p-phenylenediamine (DPPD), N-phenyl-2-naphthylamine (antioxidant D), and N-phenyl-N-cyclohexyl-p-phenylenediamine (antioxidant 4010).

[0053] like Figure 1 As shown, the present invention also discloses a method for preparing a boron-rich fuel propellant, comprising the following steps:

[0054] S1. Weighing: Accurately weigh each component in a dry environment and set aside for later use;

[0055] S2. Mixing: The binder system, oxidant, composite boron powder, auxiliary metal fuel, and performance modifier are mixed to obtain a slurry;

[0056] S3. Casting and curing: The slurry is vacuum cast and cured in a dry environment to obtain boron-rich fuel propellant.

[0057] Example 1

[0058] Table 1 Propellant Formulation Composition

[0059]

[0060] Weigh each component according to the formula in Table 1, mix the components to obtain a slurry; vacuum cast the slurry and solidify it in a dry environment to obtain a boron-rich fuel propellant.

[0061] The performance test results of the propellant are shown in Tables 2 and 3.

[0062] Table 2 Processing properties of boron-containing fuel-rich propellants

[0063]

[0064] Table 3 Energy and Combustion Performance of Boron-Containing Fuel-Rich Propellants

[0065]

[0066] Example 2

[0067] Table 4 Propellant Formulation Composition

[0068]

[0069] Weigh each component according to the formula in Table 4, and prepare a boron-rich fuel propellant using the same method as in Example 1.

[0070] The propellant performance test results are shown in Tables 5 and 6.

[0071] Table 5 Processing properties of boron-containing fuel-rich propellants

[0072]

[0073] Table 6 Energy and Combustion Performance of Boron-Containing Fuel-Rich Propellants

[0074]

[0075] Example 3

[0076] Table 7 Propellant Formulation Composition

[0077]

[0078] Weigh each component according to the formula in Table 7, and prepare a boron-rich fuel propellant using the same method as in Example 1.

[0079] The propellant performance test results are shown in Tables 8 and 9.

[0080] Table 8 Processing properties of boron-containing fuel-rich propellants

[0081]

[0082] Table 9 Energy and Combustion Performance of Boron-Containing Fuel-Rich Propellants

[0083]

[0084] Example 4

[0085] Table 10 Propellant Formulation Composition

[0086]

[0087] Weigh each component according to the formula in Table 10, and prepare a boron-rich fuel propellant using the same method as in Example 1.

[0088] The propellant performance test results are shown in Tables 11 and 12.

[0089] Table 11 Processing properties of boron-containing fuel-rich propellants

[0090]

[0091] Table 12 Energy and Combustion Performance of Boron-Containing Fuel-Rich Propellants

[0092]

[0093]

[0094] Example 5

[0095] Table 13 Propellant Formulation Composition

[0096]

[0097] Weigh each component according to the formula in Table 13 and prepare a boron-rich fuel propellant using the same method as in Example 1.

[0098] The propellant performance test results are shown in Tables 14 and 15.

[0099] Table 14 Processing properties of boron-containing fuel-rich propellants

[0100]

[0101] Table 15 Energy and Combustion Performance of Boron-Containing Fuel-Rich Propellants

[0102]

[0103] Example 6

[0104] Table 16 Propellant Formulation Composition

[0105]

[0106]

[0107] Weigh each component according to the formula in Table 16 and prepare a boron-rich fuel propellant using the same method as in Example 1.

[0108] The propellant performance test results are shown in Tables 17 and 18.

[0109] Table 17 Processing properties of boron-containing fuel-rich propellants

[0110]

[0111] Table 18 Energy and Combustion Performance of Boron-Containing Fuel-Rich Propellants

[0112]

[0113] Comparative Example 1

[0114] Table 19 Composition of Fuel-Rich Propellant Formulations Containing Ordinary Boron Powder

[0115]

[0116] According to the formulation in Table 19, a fuel-rich propellant containing ordinary boron powder corresponding to Example 2 was prepared. However, the fuel-rich propellant containing ordinary boron powder could not form a uniform slurry during the mixing process and could not be processed into a drug. As can be seen from Comparative Example 1 and Example 2, their formulations are almost identical. The only difference is that Comparative Example 2 uses composite boron powder, while Comparative Example 1 uses ordinary boron powder. In Comparative Example 1, the high boron powder content prevented the drug from being processed into a drug. However, this invention replaces ordinary boron powder with composite boron powder, which solves the problem that the boron oxide on the surface of boron powder affects the propellant process and the high boron powder content leads to the deterioration of the propellant process. This increases the boron powder content in the boron-rich propellant, thereby improving the energy performance of the propellant.

[0117] Comparative Example 2

[0118] Table 20 Composition of Fuel-Rich Propellant Formulations Containing Ordinary Boron Powder

[0119]

[0120] A fuel-rich propellant containing ordinary boron powder was prepared according to the formula in Table 20, which is similar to that in Example 6. The performance test results of the fuel-rich propellant containing ordinary boron powder are shown in Tables 21 and 22.

[0121] Table 21 Processing properties of fuel-rich propellants containing ordinary boron powder

[0122]

[0123] Table 22 Energy and Combustion Performance of Fuel-Rich Propellants Containing Ordinary Boron Powder

[0124]

[0125] As can be seen from the data in Comparative Example 2 and Example 6, the solid content is the same in both. Comparative Example 2 uses ordinary boron powder (content of 37%) and DOS as plasticizer; Example 6 uses composite boron powder (content of 41%) and FOE as plasticizer. The process performance of Example 6 is much better than that of Comparative Example 2. Moreover, Comparative Example 2 cannot be ignited at 0.12 MPa, and its combustion efficiency is significantly lower than that of Example 6. The mechanical properties of the two are the same. Compared with Comparative Example 2, the formulation of Example 6 has higher injection efficiency and higher combustion efficiency. From the examples, all examples of the present invention have high ignition performance and high combustion efficiency at low pressure. Therefore, the present invention uses fluoride-coated composite boron powder with high mechanical strength and uses FOE to replace the conventional plasticizer DOS, which can destroy the B2O3 oxide layer generated by the combustion of boron powder, generate BOF gas, reduce the phase change energy loss caused by the combustion of B2O3 in the propellant, and improve the combustion efficiency of the propellant.

[0126] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments; the above descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present invention without departing from the spirit and scope of the present invention, and all such modifications and improvements fall within the scope of the present invention; the scope of protection of the present invention is determined by the appended claims.

Claims

1. A boron-containing fuel-rich propellant, characterized in that, The following components are included by mass percentage: Adhesive system: 15-24%; Oxidizing agent: 28-32%; Composite boron powder: 40-50%; Auxiliary metal fuel: 5~10%; Performance modifier: 0.1–2%; The adhesive system includes an adhesive, a curing agent, and a plasticizer, wherein the adhesive is hydroxyl-terminated polybutadiene. The curing agent is one or more of hexamethylene diisocyanate and isophorone diisocyanate; the plasticizer is ethylene glycol perfluorodecanoate, and the mass percentage content of ethylene glycol perfluorodecanoate in the boron-containing fuel-rich propellant is 3%; The composite boron powder is prepared by a two-stage condensation method using vinylidene fluoride / acrylic alcohol copolymer as the composite agent, polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer as the auxiliary composite agent, and an epoxy resin system as the curing system. The particle size of the composite boron powder is 1.2μm~2.0μm.

2. The boron-containing rich fuel propellant according to claim 1, characterized in that, The oxidant is ammonium perchlorate and / or potassium perchlorate.

3. The boron-containing rich fuel propellant according to claim 2, characterized in that, The particle size of the oxidant includes one or more of categories I, III, IV and V, wherein the particle size range of category I is 280μm to 360μm, the particle size range of category III is 90μm to 140μm, the particle size range of category IV is 5μm to 15μm, and the particle size range of category V is 0.5μm to 2μm.

4. The boron-containing rich fuel propellant according to claim 1, characterized in that, The auxiliary metal fuel includes one or more of magnesium and aluminum, and the particle size of the auxiliary metal fuel is 1μm to 30μm.

5. The boron-containing rich fuel propellant according to claim 1, characterized in that, The performance modifier is one or more of the following: lecithin, tris[1-(2-methyl)aziridinyl]phosphine oxide, iron acrylate, 3-amino-1,2,4-triazole copper perchlorate, N,N-diphenyl-p-phenylenediamine, N-phenyl-2-naphthylamine, and N-phenyl-N-cyclohexyl-p-phenylenediamine.

6. A method for preparing a boron-containing rich fuel propellant as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Weigh each component in a dry environment and set aside for later use; S2. Mix the binder system, oxidant, composite boron powder, auxiliary metal fuel, and performance modifier to obtain a slurry; S3. Vacuum casting of the slurry and curing in a dry environment to obtain boron-rich fuel propellant.

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