Powder propellant and preparation method thereof

Abstract

The present invention belongs to the field of fuel-rich propellants for solid ramjet engines and provides a powder propellant comprising the following components in the following mass ratios: a binder system: 3% to 5%; a boron powder surface modifier: 1.2% to 3%; a fuel: 88% to 92%; and an auxiliary metal fuel: 3% to 5%. The fuel is boron powder with a particle size of 0.6 to 1.5 μm. The boron powder surface modifier comprises a main modifier and an auxiliary modifier, wherein the main modifier is a vinylidene fluoride / propylene alcohol copolymer with a molecular weight of 2000 and its mass percentage in the powder propellant is 1 to 2%. The auxiliary modifier is a copolymer of polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / propylene alcohol / hydroxyethyl acrylate and its content in the powder propellant is 0.2 to 1%. The auxiliary metal fuel is magnesium and / or aluminum. The binder system comprises a binder and a curing agent, wherein the binder is a modified epoxy resin and the curing agent is diethylenetriamine.

Description

Technical Field

[0001] The invention belongs to the field of fuel-rich propellants for solid ramjet engines, and particularly relates to a powder propellant and a preparation method thereof. Background Art

[0002] Air-breathing cruise vehicles are capable of full-range powered cruising, offering unique advantages such as rapid response, strong penetration capability, ballistic maneuvers without significant speed loss, and high terminal velocity. They represent a disruptive development direction for future aircraft. Scramjet engines are a bottleneck technology limiting the development of air-breathing cruise vehicles, and are considered a key strategic development direction by the world's leading aerospace powers. Solid scramjet engines not only offer the advantages of high specific impulse and high propulsion efficiency at hypersonic speeds, but also possess the inherent advantages of traditional solid rocket engines, such as simple structure, compact size, low cost, high safety and reliability, and excellent storability and maintainability. These engines meet the engineering application requirements of low-cost, high-reliability, strong environmental adaptability, and long-term, all-weather operation.

[0003] High-energy powder propellant does not contain oxidizer and is directly mixed with air and burned in the supersonic combustion chamber, with a high density specific impulse. It is also safe to use and has good ignition stability. It can better adapt to the strong constraints of airborne / ship-based submarine platforms, efficiently support the hypersonic cruise flight of aircraft, and greatly improve the efficiency of hypersonic long-range delivery.

[0004] High-energy powder propellant exhibits no autonomous combustion behavior, allowing for customized combustion adjustments and multiple ignition capabilities. This effectively supports the engine and its associated multi-mode switching capabilities during cruise trajectories, balancing high-G maneuvers with wide-area target coverage. Furthermore, its repeatable ignition capability allows for active engine power-up and power-down during hypersonic cruise. Upon sensing an interceptor missile situation, the aircraft can proactively shut down its ramjet engine and perform a high-G glide maneuver to evade a penetration. During extended flight, the engine can be re-ignited and switched to a higher level, leveraging the cruise missile's power advantage to achieve wide-area coverage of moving targets.

[0005] High-energy powder propellant is mainly composed of boron powder and metal powders such as magnesium powder and aluminum powder. The chemical properties of boron powder are relatively active and it is easily oxidized in the air. The surface of boron powder is covered with highly sticky boron oxides (mainly B2O3 and H3BO3). In addition, the morphology of boron powder is irregular, which will cause boron powder accumulation and affect the delivery of propellant.

[0006] In addition, due to the active chemical properties of boron powder, its storage performance will decrease due to oxidation during storage. During the combustion process, the boron oxide (B2O3) on the surface of the boron powder will affect the ignition and combustion performance of the propellant. Summary of the Invention

[0007] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a powder propellant and a preparation method thereof. The powder propellant of the present invention uses a high-molecular-weight vinylidene fluoride / propylene alcohol copolymer modifier with a polyhydroxy structure to modify the surface of boron powder, and uses an adhesive to compound the composited boron powder with a flammable metal and granulate it into a propellant micro-unit powder, thereby isolating the boron powder from contact with air and preparing a powder with a regular morphology. This solves the problem of boron powder being oxidized directly when exposed to air, resulting in reduced combustion efficiency, and also solves the problem of boron powder agglomerating due to the generation of sticky products due to oxidation, which affects transportation. In addition, the powder with a regular morphology is more conducive to transportation than the original boron powder with an irregular morphology.

[0008] The technical solution of the present invention is a powder propellant comprising the following components in the following mass ratios:

[0009] Adhesive system: 3% to 5%;

[0010] Boron powder surface modifier: 1.2-3%;

[0011] Fuel: 88% to 92%;

[0012] Auxiliary metal fuel: 3% to 5%;

[0013] The fuel is boron powder;

[0014] The boron powder surface modifier includes a main modifier and an auxiliary modifier, wherein the main modifier is a vinylidene fluoride / propylene alcohol copolymer with a molecular weight of 2000.

[0015] Furthermore, the particle size of the boron powder is 0.6-1.5 μm.

[0016] Furthermore, the auxiliary metal fuel is magnesium and / or aluminum, and the particle size is 0.6 to 2 μm.

[0017] Furthermore, the mass percentage of the main modifier in the powder propellant is 1-2%.

[0018] Furthermore, the auxiliary modifier is a copolymer of polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / propylene alcohol / hydroxyethyl acrylate.

[0019] Furthermore, the content of the auxiliary modifier in the powder propellant is 0.2-1%.

[0020] Furthermore, the above adhesive system includes an adhesive and a curing agent, wherein the adhesive is a modified epoxy resin and the curing agent is diethylenetriamine.

[0021] The present invention also provides a method for preparing the above-mentioned powder propellant, comprising the following steps:

[0022] Step 1, surface modification of the fuel: in a dry environment, boron powder, vinylidene fluoride / propylene alcohol copolymer, polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer, and ethyl acetate are weighed in proportion, and the vinylidene fluoride / propylene alcohol copolymer is configured into a dilute solution; polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer is added under stirring, and after the polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / hydroxyethyl acrylate copolymer is completely dissolved, the temperature of the reaction system is raised to 75°C to 80°C, boron powder is added thereto, and the mixture is stirred under reflux for 3 to 5 hours. Stirring is stopped until the solution becomes clear, and then 80% of the ethyl acetate is distilled off under stirring to obtain a suspension of fluoride-complexed boron powder;

[0023] Step 2: Mixing and granulating the propellant: weigh the remaining components in a dry environment according to proportion, add the binder and auxiliary metal fuel to a mixer in sequence and mix them evenly, then add the surface-modified fuel obtained in step 1, mix evenly, add the curing agent in the binder system and continue mixing, control the material mixing temperature at 30°C to 50°C to ensure that the system is completely mixed; then add petroleum ether to the propellant slurry, stir, remove the petroleum ether and ethyl acetate under vacuum conditions at 60°C, and granulate in a granulator;

[0024] Step 3: Propellant solidification and molding: solidify the propellant powder in a dry environment, cool it naturally, sieve it to obtain powder of a predetermined particle size, and obtain the propellant product through grading.

[0025] Furthermore, in the above step 2, the material mixing time is 60 minutes to 90 minutes; the amount of petroleum ether used is 4 to 6 times the total mass of the propellant, and the stirring time after adding the petroleum ether is 2 to 3 hours; in the step 3, the curing temperature of the propellant powder is 50°C to 70°C, and the curing time is 1 to 3 days; the predetermined particle size is in the range of 1.6 to 5 μm.

[0026] Furthermore, in the above steps 1 to 3, the dry environment refers to an absolute humidity not exceeding 10g water / kg air.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Boron powder is easily oxidized to form B2O3, which in turn forms highly viscous and loose H3BO3, which covers the surface of the boron powder. This causes the boron powder to aggregate, seriously affecting its dispersibility. Since H3BO3 is a loose, porous structure, it absorbs oxygen and water from the air, leading to further oxidation of the boron powder. The present invention uses PFVA (vinylidene fluoride / propylene alcohol copolymer, the same below) containing a polyhydroxy structure, a polyvinyl alcohol derivative that reacts with H3BO3 on the surface of the boron powder to form a borate ester that tightly covers the surface of the boron powder, forming a dense coating. Furthermore, a fluorine-containing modifier is used to surface-modify the boron powder, which helps suppress the formation of a cohesive phase during combustion and improves the combustion efficiency of the boron powder.

[0029] 2. Epoxy resin is a structural material with high mechanical strength. Boron powder is combined with flammable metals such as aluminum powder and magnesium powder using epoxy resin as an adhesive to prepare powder propellant. The propellant powder has high mechanical strength and regularity. Since the surface is completely covered by the epoxy resin structure, the contact between the metal powder and the air is completely blocked, and the storage performance of the propellant is greatly improved.

[0030] 3. The powder propellant is prepared by compounding flammable metal and boron powder. The propellant has a higher primary combustion temperature and is easier to re-ignite during the secondary combustion process, thus giving the propellant better combustion performance.

[0031] 4. The presence of PANE (polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / propylene alcohol / hydroxyethyl acrylate copolymer, the same below) can further improve the reaction efficiency of PFVA and boric acid and fill the structural defects of boron powder, thereby improving the structural regularity of boron powder. The introduction of fluorine into the polyvinyl alcohol structure is beneficial to inhibiting the formation of a condensed phase and improving the combustion efficiency of boron powder.

[0032] 5. The present invention adopts the following formula composition: a polyhydroxy fluorine-containing polymer modifier is used to modify the surface of the boron powder, and a high mechanical strength adhesive is used to compound the boron powder with a flammable metal and granulate the boron powder into a propellant micro-unit powder with a regular morphology. This isolates the boron powder from contact with air, solves the problem of oxide generation caused by environmental influences during the storage of boron powder, and thus improves the process performance and delivery efficiency of the propellant.

[0033] 6. In the preparation method of the present invention, to improve reaction efficiency, PFVA is dissolved in ethyl acetate. Under the action of PANE, it is deposited on the surface of the boron powder and reacts with boric acid, forming a dense coating. This not only isolates air and water but also improves the combustion efficiency and structural regularity of the propellant. Furthermore, the polyhydroxyl coating further facilitates the composite of the auxiliary metal fuel. The polyhydroxyl structure of PVFA reacts rapidly with H3BO3 at high temperatures to form a coating. The composite boron powder significantly enhances its sedimentation in the solvent. After stopping stirring, the boron powder completely settles to the bottom of the reactor, resulting in a transparent and clear solution.

[0034] When the powder propellant of the present invention burns, the combustible metal burns first, releasing a large amount of heat. This heat breaks down the fuel powder into smaller particles, generating a high level of heat, which provides a heat source for the combustion of the boron. Some of the boron powder burns directly at high temperatures, resulting in a higher primary combustion temperature. Uncompletely burned boron particles enter the afterburning chamber. Due to their higher initial temperature during the primary combustion process, they are more susceptible to afterburning, thus improving the propellant's combustion performance.

[0035] The propellant powder formula and preparation method of the present invention effectively improve the storage performance and combustion performance of the powder propellant and are more conducive to the transportation of the propellant powder, thereby effectively improving the comprehensive performance of the powder propellant. DETAILED DESCRIPTION

[0036] The following describes it in detail with reference to specific embodiments.

[0037] Example 1

[0038] A powder propellant, the composition of which is shown in Table 1 below, the physical and chemical properties of the obtained propellant are shown in Table 2, and the fluidity of the obtained propellant is shown in Table 3.

[0039] Table 1 Propellant composition

[0040]

[0041] Table 2 Propellant physical and chemical properties

[0042]

[0043] Table 3 Propellant fluidity

[0044]

[0045] It can be seen that the propellant provided in Example 1 has no boron element on its surface, has a good composite effect, has a small angle of repose of the propellant powder, has excellent fluidity, and has no change in the angle of repose after being stored for one year, indicating that the propellant has excellent storage performance.

[0046] Example 2

[0047] A powder propellant has a composition as shown in Table 4 below, physical and chemical properties of the obtained propellant are shown in Table 5, and fluidity of the obtained propellant is shown in Table 6.

[0048] Table 4 Propellant composition

[0049]

[0050] Table 5 Propellant physical and chemical properties

[0051]

[0052] Table 6 Propellant fluidity

[0053]

[0054] It can be seen that the propellant provided in Example 2 has no boron element on its surface, has a good composite effect, has a small angle of repose of the propellant powder, has excellent fluidity, and has no change in the angle of repose after being stored for one year, indicating that the propellant has excellent storage performance.

[0055] Example 3

[0056] A powder propellant has a composition as shown in Table 7 below, physical and chemical properties of the obtained propellant are shown in Table 8, and flowability of the obtained propellant is shown in Table 9.

[0057] Table 7 Propellant composition

[0058]

[0059] Table 8 Propellant physical and chemical properties

[0060]

[0061] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limiting of the disclosed embodiments. Numerous modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of the present invention shall be determined by the scope of the claims.

Claims

1. A powder propellant, characterized in that: The composition comprises the following components in the following mass ratios: Adhesive system: 3% to 5%; Boron powder surface modifier: 1.2-3%; Fuel: 88% to 92%; Auxiliary metal fuel: 3% to 5%; The fuel is boron powder; The boron powder surface modifier includes a main modifier and an auxiliary modifier, wherein the main modifier is a vinylidene fluoride / propylene alcohol copolymer with a molecular weight of 2000; The auxiliary metal fuel is magnesium and / or aluminum, with a particle size of 0.6 to 2 μm; The auxiliary modifier is a copolymer of polyethylene glycol monobutyl ether acrylate / acrylonitrile / allylamine / propylene alcohol / hydroxyethyl acrylate; The adhesive system comprises an adhesive and a curing agent, wherein the adhesive is a modified epoxy resin and the curing agent is diethylenetriamine; The particle size of the boron powder is 0.6 to 1.5 μm; The mass percentage of the main modifier in the powder propellant is 1 to 2%; The content of the auxiliary modifier in the powder propellant is 0.2-1%.

2. A method for preparing a powder propellant according to claim 1, characterized in that: The following steps are involved: Step 1, surface modification of the fuel: in a dry environment, boron powder, vinylidene fluoride / propylene alcohol copolymer, auxiliary modifier, and ethyl acetate are weighed in proportion to prepare the vinylidene fluoride / propylene alcohol copolymer into a dilute solution; the auxiliary modifier is added under stirring, and after the auxiliary modifier is completely dissolved, the temperature of the reaction system is raised to 75°C to 80°C, boron powder is added thereto, and the mixture is stirred under reflux for 3 to 5 hours. Stirring is stopped until the solution becomes clear, and then 80% of the ethyl acetate is distilled off under stirring to obtain the surface-modified fuel; Step 2: Mixing and granulating the propellant: weigh the remaining components in a dry environment according to proportion, add the binder and auxiliary metal fuel in the binder system to a mixer in sequence and mix them evenly, then add the surface-modified fuel obtained in step 1, mix evenly, add the curing agent in the binder system and continue mixing, control the material mixing temperature at 30°C to 50°C, and ensure that the system is completely mixed; then add petroleum ether to the propellant slurry, stir, remove the petroleum ether and ethyl acetate under vacuum conditions at 60°C, and granulate in a granulator; Step 3: Propellant solidification and molding: solidify the propellant powder in a dry environment, cool it naturally, sieve it to obtain powder of a predetermined particle size, and obtain the propellant product through grading.

3. The method for preparing a powder propellant according to claim 2, wherein: In the step 2, the material mixing time is 60 min to 90 min; the amount of petroleum ether is 4 to 6 times the total mass of the propellant, and the stirring time after adding petroleum ether is 2 to 3 hours; In the step 3, the curing temperature of the propellant powder is 50° C. to 70° C., and the curing time is 1 to 3 days; and the predetermined particle size ranges from 1.6 to 5 μm.

4. The method for preparing a powder propellant according to claim 2, wherein: In steps 1 to 3, the dry environment refers to an absolute humidity not exceeding 10g water / kg air.

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