RU2429282C2 - Method of producing mixed solid fuel - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves preparation of a fuel mixture via successive mechanical mixing of oxidising agent with fuel-binder. The oxidising agent used is either ammonium perchlorate (APC) or ammonium nitrate (AN) or octogen (HMX) or a mixture of APC/AN, APC/HMX, AN/HMX, components being in ratio 1/1 for each mixture. The fuel-binder used is inert rubber (SKDM-80) or active rubber - polyurethane which is plasticised with nitroglycerine. The mixture additionally contains tin chloride powder with particle size (100-150) mcm, which is premixed for not less than 30 minutes with ultrafine aluminium powder with particle size less than 0.1 mcm, with the following ratio of components in wt %: ultrafine aluminium powder 87.5, tin chloride powder - 12.5. A hardener is added to the obtained mixture and the fuel composition is stirred for not less than 30 minutes.

EFFECT: rate of combustion of the mixed solid fuel increases depending on compositions of the oxidising agent and fuel-binder used in the fuel.

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Description

The invention relates to the field of development of mixed solid fuels (CTT) containing aluminum powder as one of the combustible components.

Mixed solid fuels containing a polymer fuel-binder (e.g. rubber, butyl rubber, polybutadiene, etc.), an inorganic oxidizing agent (ammonium perchlorate, ammonium nitrate, nitramines and their mixtures) and aluminum powder are used as energy sources of solid propellant rocket engines (RTTT) and solid fuel gas generators (TGG) for various purposes [1].

The main requirement for CTT for marching solid propellant rocket engines (boosters) is to ensure high energy characteristics (specific impulse of thrust I ₁ , that is, the ratio of the thrust developed by the engine to the mass second consumption of combustion products). Since the value of I _{1 is} proportional to the square root of the fuel combustion temperature T, then to increase the energy characteristics of the CTT, up to 18% of aluminum powder is introduced into their composition, the combustion temperature of which is quite high compared to other combustible components and reaches T≈3800 K [2].

When using CTT in regulated solid propellant rocket engines and solid fuel gas generators, one of the main requirements is also the possibility of increasing the thrust of solid propellant rocket engines and the consumption of combustion products in TGGs (in particular, ensuring the necessary gas flow rate for superfast pressurization of automobile airbags). An increase in thrust and consumption of combustion products (for a given design of solid propellant rocket motors or TGGs) is possible only by increasing the linear burning velocity of the CTT.

One of the known ways to increase the burning rate of CTT is to replace standard ASD aluminum powders (ASD-1, ASD-4, ASD-6, etc.) [3] with ultrafine aluminum powder (UDP A1), for example, ALEX grade UDP obtained by the method of electric explosion of wires [4]. In this case, aluminum particles of standard powders of the ASD grades have a mass-average diameter in the range of D ₄₃ = (1 ÷ 10) μm, and the mass-average diameter of the ALEX brand A1 is orders of magnitude smaller and amounts to D ₄₃ ≈0.1 μm [5].

The results of experimental studies of various authors (for example, [6, 7]) obtained over the past five years have shown the practical possibility of a multiple increase in the CTT burning rate due to the complete or partial replacement of powder of grades of ASD by UDP A1, for example, of ALEX grade, in the pressure range environment (2-12) MPa.

A known method of producing a mixed solid fuel based on ammonium perchlorate, inert rubber grade SKDM-80, aluminum powder and hardener, characterized in that as a metal fuel in the composition of the CTT is introduced ultrafine aluminum powder grade ALEX, partially or completely replacing aluminum powders of industrial brands ASD [8]. At the same time, an increase in the CTT burning rate by (1.2–3.5) times depending on the external pressure in the range (0.03–6.0) MPa was experimentally obtained.

However, a further increase in the burning rate requires a substantial increase in the percentage of aluminum powder in the CTT composition (more than 15 wt.%). This leads to a decrease in the energy characteristics of the fuel, in particular the specific impulse of traction, as well as to a deterioration in the mechanical and strength characteristics of the CTT charge.

The closest in technical essence is a method of manufacturing charges of mixed solid fuel, including mechanical mixing of an oxidizing agent, a fuel-binder and aluminum powder [9]. In this method, a catalyst and processing aids are additionally added to the fuel mass.

The objective of the invention is to develop a method for producing a mixed solid fuel with a higher level of burning rate compared to the prototype without reducing the energy and mechanical-strength characteristics of the CTT charge.

The technical result of the invention is achieved by the fact that a method for producing mixed solid fuel has been developed, which includes preparing the fuel mass by sequential mechanical stirring of an oxidizing agent, which is used either ammonium perchlorate (PHA), or ammonium nitrate (HA), or octogen (NMX), or a mixture PHA / NA, PHA / NMX, NA / NMX with a component ratio of 1/1 for each mixture and fuel-binding agent, which is either inert rubber (SKDM-80) or active rubber - polyurethane, plasticized neither troglycerol, in addition, tin chloride powder with a particle size of (100 ÷ 150) microns, pre-mixed for at least 30 minutes with an ultrafine aluminum powder with a particle size of at least 0.1 microns, is introduced into the mixture with the following ratio of components, wt.%:

ultrafine aluminum powder 87.5, tin chloride 12.5,

a technological additive is introduced into the mixture — a hardener in an amount of 0.1 wt.% in excess of 100% and the fuel composition is mixed for at least 30 minutes.

The obtained positive effect of increasing the burning rate of CTT due to the introduction of tin chloride powder can be associated with the following factors. It is known (for example, [10]) that when the initial ultrafine aluminum powder is burned in air at a temperature of at least 2000 K, two processes occur simultaneously - the formation of aluminum oxides with heat and aluminum nitride with heat absorption, the thermal effect of which is 2.5 times lower. The total solid combustion products of ultrafine aluminum powder contain up to (50-60) wt.% Aluminum nitride. The formation of aluminum oxide is characteristic of aluminum powders of ASD grades when burning in air; aluminum nitride is formed in small amounts at the trace level.

The high temperature of the processes indicates the possibility of their occurrence during combustion in the composition of CTT. It can be expected that the prevention of the formation of aluminum nitride during combustion of an ultrafine aluminum powder will lead to an increase in heat generation during combustion of fuel systems, i.e., it will contribute to an increase in the burning rate of CTTs containing ultrafine aluminum powder.

Implementation example

The manufacture of the fuel mass is carried out by the method of sequential mechanical mixing of weighed portions of an organic fuel binder, oxidizer, metal fuel and additives, which include a substance that changes the combustion characteristics of CTT - tin chloride and a technological additive - hardener.

The following mixing sequence is observed. Mixture 1. Organic fuel binder and oxidizing agent. Mixture 2. Ultrafine aluminum powder and tin chloride powder. Mixture 3 (final). Mixture 1, 2 and technological additive - hardener di-N-oxide-1,3-dinitrile-2,4,6-triethylbenzene in an amount of 0.1 wt.% In excess of 100%.

The proposed method for producing CTT does not depend on the nature of the oxidizing agent and organic fuel-binding fuel systems. CTTs were studied on an inert combustible binder (SKDM-80 rubber) and inorganic oxidizing agents - ammonium perchlorate (PHA), ammonium nitrate (NA), octogen (NMX), mixed oxidizing agents PHA / NA, PHA / NMX and NA / NMX, taken 1/1 ratio at different oxidizer contents in the fuel system. The coefficient of excess CTT α is equal to 0.4 or 0.5. The composition of CTT includes 13.1 wt.% Ultrafine aluminum powder and 1.9 wt.% Tin chloride powder. CTT efficiency was evaluated by the efficiency coefficient K, which is equal to the ratio of the CTT burning rate containing ultrafine aluminum powder and tin chloride powder to the CTT burning rate containing the initial ultrafine aluminum powder:

K = u ₁ / u ₀ ,

where u ₁ is the burning rate of CTT containing a mixture of ultrafine aluminum powder and tin chloride powder;

u ₀ is the burning rate of CTT containing ultrafine aluminum powder.

To assess the effectiveness of the method investigated the composition of CTT, differing in nature and content of the starting components. As the metal fuel used ultrafine aluminum powder or a mixture of ultrafine aluminum powder and tin chloride powder (the total amount of aluminum and tin chloride powders is 15 wt.%), Introduced into the fuel composition. The excess coefficient of CTT oxidizer was α = 0.4 and α = 0.5. The compositions of CTT are given in table 1.

The efficiency of STT was evaluated by burning model samples with an oxidizer excess coefficient α = 0.4 and α = 0.5 at atmospheric pressure. The results of the study are given in table.2.

The inventive method is effective for CTT containing UDP aluminum, based on an active fuel binder. Thus, the burning rate of a mixed solid fuel containing ultrafine aluminum powder (11.25 wt.%) And tin chloride powder (3.75 wt.%) On polyurethane rubber plasticized with nitroglycerin increases 1.2 times in comparison with a fuel containing ultrafine aluminum powder without tin chloride. A detailed table of these experiments is not given.

Table 1 Composition number α Content Components wt.% PHA ON NMX SKDM-80 UDP Al Sncl ₂ one 61.8 - - 23.2 15.0 - 2 61.8 - - 23.2 13.1 1.9 3 - 64.0 - 21.0 15.0 - four - 64.0 - 21.0 13.1 1.9 5 - - 75.0 10.0 15.0 - 6 0.4 - - 75.0 10.0 13.1 1.9 7 31.5 31.5 - 22.0 15.0 - 8 31.5 31.5 - 22.0 13.1 1.9 9 37.3 - 37.3 10.4 15.0 - 10 37.3 - 37.3 10.4 13.1 1.9 eleven - 34.6 34.6 15.8 15.0 - 12 - 34.6 34.6 15.8 13.1 1.9 13 66.2 - - 18.8 15.0 - fourteen 66.2 - - 18.8 13.1 1.9 fifteen - 68.6 - 16.4 15.0 - 16 - 68.6 - 16.4 13.1 1.9 17 - - 79.5 5.5 15.0 - eighteen - - 79.5 5.5 13.1 1.9 19 0.5 33.7 33.7 - 17.6 15.0 - twenty 33.7 33.7 - 17.6 13.1 1.9 21 38.4 - 38.4 8.2 15.0 - 22 38.4 - 38.4 8.2 13.1 1.9 23 - 36.9 36.9 11.2 15.0 - 24 - 36.9 36.9 11.2 13.1 1.9

table 2 Oxidizer No. of compositions (α = 0.4) u ₀ , mm / s u ₁ , mm / s TO No. of compositions (α = 0.5) u ₀ , mm / s u ₁ , mm / s K PHA 1,2 3.1 5.4 1.7'4 13.14 3.7 6.6 1.78 ON 3.4 2.0 3.0 1.50 15.16 2.4 3.6 1.50 NMX 5,6 1.8 4.3 2.34 17.18 2.3 5.5 2.39 PHA / ON 7.8 2.9 4.4 1.51 19,20 3.3 5.0 1.52 PHA / NMX 9.10 2.5 4.8 1.92 21.22 3.1 6.0 1.94 ON / HMX 11.12 2.2 2.7 1.23 23.24 2.5 3.3 1.32

Thus, it has been experimentally shown that for various oxidizing compositions (PHA, HA, NMX, PHA / HA, PHA / NMX, HA / NMX) and two types of combustible binder (inert rubber SKDM-80 and polyurethane rubber plasticized with nitroglycerin) additional the introduction of tin chloride powder in the composition of the CTT increases the burning rate of the proposed fuel compositions.

LITERATURE

1. Energy condensed systems: a brief encyclopedic dictionary / Ed. B.P. Zhukova. - M .: Janus-K, 2000 .-- 596 p.

2. Combustion of powdered metals in active media / P.F. Pokhil, A. F. Belyaev, Yu. V. Frolov, B. C. Logachev, A. I. Korotkov. - M .: Nauka, 1972.- 294 p.

3. Aluminum powder finely dispersed ASD-1, ASD-4, ASD-6: Specifications 48-5-226-87. LLC "SUAL-PM", Shelekhov. 1987.

4. Ilyin A.P., Nazarenko O.B., Tikhonov D.V. Obtaining nanopowders by spraying metals with powerful pulses of electric current // Mining Journal. Specialist. release. Non-ferrous metals. 2006. No4. S.65-69.

5. Arkhipov V.A., Bondarchuk S.S., Korotkikh A.G., Lerner M.I. Production technology and dispersed characteristics of aluminum nanopowders // Mining Journal. Specialist. release. Non-ferrous metals. 2006. No4. S.58-64.

6. Arkhipov VA, Korotkikh AG, Kuznetsov VT, Savelyeva L.A. Effect of dispersion of metal additives on the burning rate of mixed compositions // Chemical Physics. 2004. Vol. 23, No. 9. S.18-21.

7. De Luca LT, Galfetti L., Severini F. et al. Combustion of Combined Solid Fuels with Nanoscale Aluminum // Combustion and Explosion Physics. 2005. V. 41, No. 6. S.80-94.

8. Gorbenko T.I. Patterns of combustion of high-energy heterogeneous systems containing ultrafine aluminum in a wide pressure range: Dis. ... cand. Phys.-Math. sciences. - Tomsk, 2007 .-- 141 p.

9. A method of manufacturing mixed solid fuel charges. RF patent No. 2230052 C2, 06/10/2004

10. Ilyin A.P., Yablunovsky G.V., Gromov A.A. The effect of additives on the combustion of ultrafine aluminum powder and chemical bonding of nitrogen in the air // Combustion and Explosion Physics. 1996. V. 32, No. 2. S.108-110.

Claims (1)

A method of producing a mixed solid fuel, including the preparation of a fuel mass by sequential mechanical stirring of an oxidizing agent, which is used either ammonium perchlorate (PHA), or ammonium nitrate (HA), or octogen (NMX), or a mixture of PHA / NA, PHA / NMX, NA / NMX, with a 1/1 ratio of components for each mixture and a fuel-binder, which is either inert rubber (SKDM-80) or active rubber - polyurethane plasticized with nitroglycerin, tin chloride powder is additionally introduced into the mixture ispersnostyu (100 ÷ 150) microns, premixed for at least 30 minutes with ultrafine alumina powder dispersion is not less than 0.1 microns at the following component ratio, wt.%:
ultrafine aluminum powder 87.5 tin chloride powder 12.5
a technological additive, a hardener, is introduced into the resulting mixture and the fuel composition is mixed for at least 30 minutes.