Metal fuel with combustion supercharging effect and its application and preparation method

Abstract

The present invention belongs to the technical field related to metal fuels, and discloses a metal fuel with a combustion supercharging effect, and its application and preparation method, wherein the metal fuel comprises: a metal matrix and an additive, wherein the additive is molybdenum and / or tungsten, or the additive is a fluorine-containing polymer. Compared with ordinary fuels, the metal fuel with a combustion supercharging effect provided by the present invention can produce low-boiling-point highly volatile substances when oxidized or burned without reducing the volume combustion enthalpy, thereby realizing an additional supercharging in the combustion chamber in addition to the pressure change caused by heat, greatly suppressing the occurrence of agglomeration, and improving the specific impulse of the propellant.

Description

Technical Field

[0001] The present invention belongs to the technical field related to metal fuels, and more specifically, relates to a metal fuel with a combustion boosting effect and an application and preparation method thereof. Background Art

[0002] Metal fuels are used as additives in solid propellants because of their high combustion enthalpy. They can significantly increase the energy density of propellants, improve their combustion behavior, and enhance the combustion stability of engines. Traditional metal fuels are single-element aluminum powders. Aluminum powders as metal fuels can not only significantly increase the energy density of propellants, but also their combustion products, Al2O3, can inhibit the generation of oscillating combustion, greatly improving the combustion stability of rocket engines. However, the two-phase flow loss caused by the large amount of agglomeration of condensed phase combustion products seriously reduces the combustion efficiency of propellants. The high-temperature condensed phase moving at high speed will wash away and destroy the ablation-resistant layer of the engine, and even burn the nozzle. In order to solve the problem of metal fuel combustion agglomeration, researchers have found that adding an appropriate amount of easily decomposed gas-producing additives (such as LDPE) to the propellant can promote the fragmentation of composite particles during combustion, which is expected to improve the gasification of the products and produce smaller combustion fragments, thereby inhibiting agglomeration. However, the combustion enthalpy of metal fuels is a key factor affecting the specific impulse of propellants. Excessive intake of additives may reduce the energy level of propellants. Therefore, it is particularly important to develop a metal fuel with high energy density and high combustion gas production.

[0003] On the one hand, the intake of additives that are easy to decompose and produce gas can inhibit the occurrence of combustion agglomeration, while on the other hand, too much additives will affect the overall energy performance of the propellant. Therefore, it is necessary to reasonably balance the energy and gas formation properties of metal fuels. It is necessary to design an energy fuel that can alleviate combustion agglomeration and increase the specific impulse of the propellant to overcome the above problems of existing metal fuels. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a metal fuel with a combustion boosting effect. Compared with ordinary fuels, it can produce low-boiling point highly volatile substances when oxidized or burned without reducing the volume combustion enthalpy, thereby achieving additional boosting in the combustion chamber in addition to the pressure change caused by heat. This application introduces molybdenum or tungsten as an additive for the first time. The metal element has the characteristics of high density and high combustion enthalpy. At the same time, its combustion products are MoO3, WO3, and AlF3, which are highly volatile and meet the gasification requirements of metal fuels, and meet the requirements of the aerospace field for high-energy and high-density metal fuels.

[0005] To achieve the above objectives, according to one aspect of the present invention, a metal fuel with a combustion boosting effect is provided, the metal fuel comprising: a metal matrix and an additive, wherein the additive is molybdenum and / or tungsten, or the additive is a fluorine-containing polymer.

[0006] Preferably, the metal matrix is ​​aluminum.

[0007] Preferably, when the additive is molybdenum, the weight percentage of the molybdenum is 10% to 50% of the total weight of the metal fuel; when the additive is tungsten, the weight percentage of the tungsten is 10% to 50% of the total weight of the metal fuel; when the additive is a fluoropolymer, the weight percentage of the fluoropolymer is 5% to 20% of the total weight of the metal fuel.

[0008] Preferably, when the additive is molybdenum, the weight percentage of the molybdenum is 20% of the total weight of the metal fuel; when the additive is tungsten, the weight percentage of the tungsten is 30% of the total weight of the metal fuel; when the additive is a fluoropolymer, the weight percentage of the fluoropolymer is 5% of the total weight of the metal fuel.

[0009] Preferably, the fluorine-containing polymer is polytetrafluoroethylene and / or graphite fluoride.

[0010] According to another aspect of the present invention, there is provided an application of a metal fuel having a combustion boosting effect, wherein the metal fuel is used for combustion.

[0011] According to another aspect of the present invention, there is provided a method for preparing a metal fuel having a combustion boosting effect, wherein the metal fuel comprises a metal matrix and an additive, wherein the additive is molybdenum and / or tungsten, and the method comprises: smelting the metal matrix and the additive to prepare an alloy matrix, and atomizing and solidifying the alloy matrix into particles by gas atomization; when the additive is a fluorine-containing polymer, the method comprises: preparing the metal matrix and the additive by mechanical ball milling.

[0012] Preferably, the metal matrix and the additive are melted by vacuum suspension melting technology.

[0013] In general, compared with the prior art, the metal fuel with combustion boosting effect provided by the present invention has at least the following beneficial effects:

[0014] 1. During the combustion process, ordinary fuel aluminum powder easily forms a dense alumina protective film with a high melting point on its surface, which prevents further combustion of elemental aluminum inside the aluminum particles, resulting in incomplete combustion of the fuel and incomplete energy release. The metal fuel in this application is composed of a metal matrix elemental phase and an intermediate phase. During the combustion process, the intermediate phase is preferentially oxidized to provide a large number of oxygen channels inside the particles, greatly improving the activity of the fuel.

[0015] 2. Additives such as molybdenum or tungsten have the characteristics of high density and high combustion enthalpy. For example, the density of elemental molybdenum is 10.22 g / cm 3 The theoretical unit volume combustion enthalpy is as high as 82.48 kJ / cm 3 , which is far higher than other substances that are easy to decompose and produce gas, greatly improving the density-specific impulse of the propellant.

[0016] 3. The combustion products contain volatile substances, which will promote the breakup of particles and produce smaller combustion fragments, greatly reducing the solid block residue condensed inside the combustion chamber when large solid engines are working.

[0017] 4. When the additive is molybdenum and / or tungsten, the weight is preferably 10%-50% of the total weight of the metal fuel; when the additive is a fluorine-containing polymer, the weight is preferably 5%-20% of the total weight of the metal fuel. At this content, the metal fuel can take into account the advantages of energy performance and ensure the generation of gaseous products. Further, the weight percentage of molybdenum is preferably 20% of the total weight of the metal fuel, the volume combustion enthalpy of the metal fuel is not lower than the existing aluminum powder, and the gaseous product MoO3 has the most obvious pressure increase in the combustion chamber; the weight percentage of tungsten is preferably 30% of the total weight of the metal fuel, the volume combustion enthalpy of the metal fuel is not lower than the existing aluminum powder, and the gaseous product WO3 has the most obvious pressure increase in the combustion chamber; the weight percentage of fluorine-containing polymer is preferably 5% of the total weight of the metal fuel, and the gaseous products AlF3, CO2, and water vapor have the most obvious pressure increase in the combustion chamber.

[0018] 5. The present application creatively uses molybdenum, tungsten or fluorine-containing polymers as additives, which significantly increases the gas production while ensuring the combustion enthalpy of the metal fuel, achieves additional pressurization in the combustion chamber in addition to the pressure change caused by heat, greatly inhibits the occurrence of agglomeration, and improves the specific impulse of the propellant. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematically shows a SEM image of Al-Mo metal fuel particles according to an embodiment of the present disclosure;

[0020] Figure 2 Schematically shows a SEM image of Al-W metal fuel particles according to an embodiment of the present disclosure;

[0021] Figure 3Schematically shows a SEM image of an Al-PMF composite fuel particle according to an embodiment of the present disclosure;

[0022] Figure 4 Schematically shows a SEM image of an Al-PTFE composite fuel particle according to an embodiment of the present disclosure;

[0023] Figure 5 Schematically shows a SEM image of a real MoO3 substance condensed on a crucible stand after combustion of Al-Mo metal fuel according to an embodiment of the present disclosure;

[0024] Figure 6 The SEM image of the WO3 substance desublimated on the crucible stand after the Al-W metal fuel is burned according to the embodiment of the present disclosure is schematically shown;

[0025] Figure 7 Schematically showing a SEM image of AlF3 condensed on a crucible stand after combustion of Al-PMF and Al-PTFE composite fuel according to an embodiment of the present disclosure;

[0026] Figure 8 The pressure decay trajectory of Al-Mo and Al-W metal fuels and the pressure decay trajectory of pure aluminum powder according to the embodiment of the present disclosure are schematically shown;

[0027] Fig. 9 The pressure decay trajectory of Al-PMF, Al-PTFE composite fuel and the pressure decay trajectory of pure aluminum powder according to the embodiments of the present disclosure are schematically shown. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] The present invention provides a metal fuel with combustion boosting effect, the metal fuel comprising: a metal matrix and an additive, wherein the additive is molybdenum and / or tungsten, or the additive is a fluorine-containing polymer.

[0030] The material of the metal substrate is preferably aluminum.

[0031] When the additive is molybdenum, the weight percentage of the molybdenum is preferably 10% to 50% of the total weight of the metal fuel. Further, when the weight percentage of the molybdenum is preferably 20% of the total weight of the metal fuel, the volume combustion enthalpy of the metal fuel is not lower than that of the existing aluminum powder, and the gaseous product MoO3 has the most obvious effect on the pressure increase in the combustion chamber.

[0032] When the additive is tungsten, the weight percentage of the tungsten is preferably 10% to 50% of the total weight of the metal fuel. Further, when the weight percentage of tungsten is preferably 30% of the total weight of the metal fuel, the volume combustion enthalpy of the metal fuel is not lower than that of the existing aluminum powder, and the gaseous product WO3 has the most obvious effect on the pressure increase in the combustion chamber.

[0033] When the additive is a fluorine-containing polymer, the weight percentage of the fluorine-containing polymer is preferably 5% to 20% of the total weight of the metal fuel. Wherein, the fluorine-containing polymer is one or a combination of polytetrafluoroethylene or graphite fluoride, and further, when the weight percentage of the fluorine-containing polymer is preferably 5% of the total weight of the metal fuel, the gaseous products AlF3, CO2, and water vapor have the most obvious effect on the pressure increase in the combustion chamber.

[0034] Another aspect of the present invention provides an application of a metal fuel having a combustion supercharging effect, wherein the metal fuel is used for combustion, for example, can be used for combustion in a rocket engine of aerospace.

[0035] Another aspect of the present invention provides a method for preparing a metal fuel with a combustion boosting effect, wherein the metal fuel includes a metal matrix and an additive, wherein when the additive is molybdenum and / or tungsten, the method includes: smelting the metal matrix and the additive to prepare an alloy parent material, and atomizing and solidifying the alloy parent material into particles by gas atomization; when the additive is a fluorine-containing polymer, the method includes: preparing the metal matrix and the additive by mechanical ball milling. In the embodiment of the present disclosure, when the additive is molybdenum and / or tungsten, it is preferred to use vacuum suspension smelting technology to smelt the metal matrix and the additive.

[0036] For example, first, vacuum suspension melting technology is used to melt appropriate amounts of molybdenum sheets, tungsten sheets (purity is preferably 99.99%, thickness is preferably less than 0.5 mm) and aluminum ingots (purity is preferably 99.95%) in a fixed proportion to prepare uniform Al-Mo and Al-W alloy parent materials, and then the parent materials are atomized by appropriately adjusting parameters such as spray gas pressure and heating temperature to prepare Al-Mo and Al-W metal fuels; aluminum particles are mixed with graphite fluoride and polytetrafluoroethylene in a certain proportion and ball-milled by mechanical ball milling to prepare Al-PMF and Al-PTFE composite fuels.

[0037] Through electron microscopy observation, Figure 1They are the morphology of Al-Mo metal fuel particles, Figure 2 This is the morphology of Al-W metal fuel particles. Figure 3 They are the morphology of Al-PTFE composite fuel particles, Figure 4 This is the morphology of Al-PTFE composite fuel particles. Figure 5 They are the SEM images of MoO3 condensed on the crucible after the combustion of Al-Mo metal fuel. Figure 6 This is the SEM image of WO3 condensed on the crucible after the combustion of Al-W metal fuel. Figure 7 This is a SEM image of AlF3 condensed on the crucible after the combustion of Al-PMF and Al-PTFE composite fuels. Figure 1 and Figure 5 As shown in the figure, a large number of evenly distributed rice-like phases appeared on the surface of Al-Mo and Al-W metal fuel particles, which can effectively avoid the formation of passivation film. The MoO3 and WO3 condensed on the crucible after firing were analyzed by SEM. It was found that most of the MoO3 and WO3 particles had good sphericity, with diameters ranging from tens of nanometers to hundreds of nanometers. Many "small" particles with diameters of tens of nanometers adhered to the surface of "large" particles. A few MoO3 particles existed in the form of needles or flakes, while a few WO3 mainly existed in the form of octagonal prisms. This is enough to show that MoO3 and WO3 do exist in the form of gas during combustion. The Al-PMF and Al-PTFE composite fuel particles prepared by mechanical ball milling are obviously not as spherical as the Al-Mo and Al-W metal fuel particles. They are equiaxed rather than flaky, have a wide particle size distribution range, and the average particle size is about 20.6μm. The AlF3 condensed on the crucible after burning was subjected to SEM analysis, and it was found that the AlF3 particles had good sphericity, with a diameter of nearly 1μm, and a small amount of pores were distributed on the surface of the particles. This is enough to show that A1F3 does exist in the form of gas during the combustion process, and then condenses on the crucible when it is condensed.

[0038] Table 1 shows the relationship between the volumetric combustion enthalpy of Al-Mo metal fuel and the Mo content. It can be seen that with the increase of Mo content, the volumetric combustion enthalpy of the metal fuel first increases and then decreases. When the Mo content is 20%, the volumetric combustion enthalpy has exceeded that of elemental aluminum powder; Table 2 shows the relationship between the volumetric combustion enthalpy of Al-W metal fuel and the W content. With the increase of W content, the volumetric combustion enthalpy of the metal fuel first increases and then decreases. When the W content is 30%, the volumetric combustion enthalpy has exceeded that of elemental aluminum powder; As shown in Tables 3 and 4, although the theoretical combustion enthalpy of PMF and PTFE (10.7 kJ / g and 9 kJ / g, respectively) is lower than the combustion enthalpy of aluminum (31.0 kJ / g), a large amount of gaseous products produced by the combustion of fluoropolymers will quickly fill the cartridge, causing the pressure inside the cartridge to increase rapidly.

[0039]

[0040] Table 1

[0041]

[0042] Table 2

[0043]

[0044] Table 3

[0045]

[0046] Table 4

[0047] The present application also illustrates through constant volume isothermal combustion experiments that the low-boiling substances produced by the combustion of Al-Mo, Al-W metal fuels and Al-PMF, Al-PTFE composite fuels can cause additional pressure increase in the combustion chamber in addition to the pressure change caused by heat. Specifically: weigh 0.202g, 0.241g, 0.266g, 0.237g, and 0.246g of pure aluminum, Al-Mo metal fuel with a Mo content of 20%, Al-W metal fuel with a W content of 30%, Al-5PMF composite powder with a PMF content of 5%, and Al-5PTFE composite fuel with a PTFE content of 5% to conduct oxygen bomb experiments to ensure that the heat released by the combustion of each fuel is equal. The pressure sensor connected to the data acquisition system is used to synchronously monitor the pressure change in the bomb barrel before and after the sample is ignited. The oxygen pressure in the bomb barrel is maintained at 3MPa before ignition. The ignition time of the sample in the crucible is set to 184.1325s through program control. The entire experiment lasts for 15 minutes. The combustion pressure increase curve is shown in Figure 8 , 9 As shown in the figure, the pressure curve shows that when the total heat release is kept the same, the pressurization effect of the series of supercharged metal fuels is significantly stronger than that of pure Al powder. This is attributed to the low-boiling point substances produced by the combustion of this type of fuel existing in the cartridge in gaseous form, which significantly increases the pressure. Among them, the maximum pressure corresponding to the composite fuel with a 5% fluoropolymer content is the highest. This is because the combustion of a large amount of AlF3, CO2 and water vapor by aluminum-based fluoropolymers will instantly fill the entire cartridge, significantly increasing the pressure.

[0048] Figure 8The pressure decay trajectories of Al-20Mo and Al-30W metal fuels and the pressure decay trajectories of pure aluminum powder are shown respectively. It can be seen that the two are quite different from the pure aluminum combustion pressure change curve. The pressure decay of pure aluminum powder is completely determined by the effect of condensed water, while the pressure decay of Al-Mo and Al-W alloy powders is completely determined by the condensed water and the condensation of gaseous MoO3 or WO3. Therefore, a vertically descending line segment will appear in the pressure curve of Al-Mo alloy powder. It can be seen from the figure that the pressure increase of the metal fuel in the combustion process of this application is significantly higher than the pressure increase during the combustion of pure aluminum powder.

[0049] In summary, compared with ordinary fuels, the metal fuel in the present application can produce low-boiling-point and highly volatile substances when oxidized or burned without reducing the volumetric combustion enthalpy, which greatly inhibits the occurrence of agglomeration and improves the specific impulse of the propellant.

[0050] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a metal fuel having a combustion pressurization effect for a propellant, characterized in that: The metal fuel includes a metal matrix and an additive, wherein the metal matrix is ​​aluminum, and the additive is molybdenum and / or tungsten. The method includes: smelting the metal matrix and the additive to prepare an alloy matrix, atomizing the alloy matrix and solidifying it into particles by gas atomization, and the weight percentage of the additive is 10% to 50% of the total weight of the metal fuel.

2. The preparation method according to claim 1, characterized in that: The metal matrix and the additive are melted by using vacuum suspension melting technology.

3. The preparation method according to claim 1, characterized in that: When the additive is molybdenum, the weight percentage of the molybdenum is 20% of the total weight of the metal fuel; when the additive is tungsten, the weight percentage of the tungsten is 30% of the total weight of the metal fuel.

4. A metal fuel prepared according to the preparation method according to any one of claims 1 to 3.

5. An application of the metal fuel according to claim 4, characterized in that: The metal fuel is used in propellants.

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