RU2363691C1 - Solid-propellant composition based on ammonia nitrate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention refers to the composition of solid propellants. The solid-propellant composition based on ammonia nitrate contains the rubber of trademark "СКДМ-80", di-N-oxide-1,3-dinitrile-2,4,6-triethylbenzene as curing agent and mixture of aluminium powder of trademark "АСД-1" and ultrafine aluminium ALEX in ratio 1:1.

EFFECT: invention increases the burning velocity, decreases the pressure dependence of the burning velocity and reduces the content of solid condensed products.

3 tbl

Description

The invention relates to the field of development of solid fuels based on ammonium nitrate (HA), and in particular to the production of high-energy solid fuel compositions with a high burning rate, a weak dependence of the burning rate on pressure and a low content of toxic components and solid condensed substances in the combustion products.

Modern compositions of high-energy solid fuels consist of three main components - an oxidizing agent, a polymer fuel-binder, and aluminum powder as a metal fuel [1]. In traditional compositions, NH ₄ ClO ₄ - ammonium perchlorate (PHA) is used as an oxidizing agent, which forms free chlorine Cl ₂ and a number of its toxic compounds (Hcl, HclO ₄ , etc.) during the combustion of fuels based on it. These components have an adverse effect on the environment (acid rain, the formation of ozone holes, etc.) [2, 3].

One promising approach to solving the problem of reducing toxic emissions, which is particularly relevant in connection with the activation space rocket activity (Runs commercial satellites in some countries) is used as the oxidant NH ₄ NO ₃ - ammonium nitrate, partially or totally substituting PCA [ 4, 5]. This oxidizing agent is much cheaper than PHA and does not form environmentally harmful products during combustion. However, fuels based on HA are characterized by low values of the combustion temperature and, as a result, low levels of the main energy characteristic — specific impulse of thrust [4]. To increase energy characteristics, aluminum powders of industrial grades ASD-1, ASD-4, ASD-6, etc., are introduced into solid fuel compositions based on HA, which significantly increase the adiabatic temperature of fuel combustion [1, 4]. Powders of ASD grades contain aluminum particles with a diameter of (1 ÷ 25) microns. The dispersion characteristics of ASD-1 are given in Table 1 [5, 6].

Table 1 Dispersion characteristics of powders Powder grade D ₁₀ μm D ₂₀ μm D ₃₀ μm D ₃₂ μm D ₄₃ μm ASD-1 1.4 12.0 13.6 17.4 21.9 "ALEX" 0.12 0.13 0.14 0.16 0.18

The closest in technical solution to the claimed solid fuel composition based on ammonium nitrate is a composition [7] containing the following components, wt.%:

Ammonium nitrate  71.8 Rubber of the SKDM-80 brand  13.2 ASD-1 grade aluminum powder  15.0 Curing agent  0.1 over 100%

As a curing agent, di-N-oxide-1,3-dinitrile-2, 4, 6-triethyl-benzene (conventional name TON-2) was used, which allows the fuel system to be cured at room temperature (20 ÷ 25) ° С in during the day and to avoid polymorphic transformations of HA [8].

The characteristics of the fuel composition based on ammonium nitrate, selected as a prototype, are shown in table.2.

table 2 Prototype Characteristics Characteristic Value Burning rate at 4 MPa u = 4.4 ± 0.1 mm / s Burning rate at atmospheric pressure u ₁ = 0.9 mm / s The exponent in the law of burning rate ν = 0.43 Specific impulse J ₁ = 233 s Content of solid combustion products at atmospheric pressure z = (20 ÷ 25) wt.%

Here u ₁ , ν are constants in the power law of the burning rate

u = u ₁ · ρ ^ν ,

where the dimensions [u] = [u ₁ ] = mm / s; [p] = MPa.

The condensed solids content z is determined under the conditions of fuel combustion during atmospheric combustion and is an estimated value for comparison with other fuel compositions. Under combustion conditions at a pressure of p = 4 MPa, the z value decreases (7–10) times.

The disadvantages of the prototype include a low level of combustion rate, increased sensitivity to pressure, a significant solids content in the combustion products.

The objective of the present invention is to develop a solid fuel composition with a higher level of burning rate, less dependence of the burning rate on pressure, lower content of solid condensed products of combustion at a relatively low cost of the fuel composition.

The problem is solved in that a solid fuel composition based on ammonium nitrate containing ammonium nitrate, rubber grade SKDM-80, aluminum powder and di-N-oxide-1,3-dinitrile-2,4,6-triethyl-benzene as hardener, characterized in that the fuel further comprises a mixture of aluminum powders of the grades ASD-1 and "ALEX" in a ratio of 1: 1, with the following components, wt.%:

Ammonium nitrate  71.8 Rubber of the SKDM-80 brand 13.2 ASD-1 grade aluminum powder 7.5 ALEX brand aluminum powder  7.5 TON-2  0.1 over 100%

ALEX brand aluminum powder is an ultrafine powder (particle size ~ 0.1 μm) obtained by the method of electric explosion of conductors [6], dispersion characteristics are given in Table 1.

Example

On an analytical balance, weights of the corresponding substances are weighed to an accuracy of ± 0.002 g

Ammonium nitrate  71.8 g Rubber of the SKDM-80 brand  13.2 g ASD-1 grade aluminum powder  7.5 g ALEX brand aluminum powder  7.5 g TON-2  0.01 g

The resulting mixture is stirred mechanically in a mixer type "BACON" followed by continuous pressing of samples of a given size.

We used cylindrical samples with a diameter of 10 mm, armored on the side surface. The height of the samples was varied depending on the nature of the experiment. The burning rate of the samples was measured in a constant pressure device in a nitrogen atmosphere in the pressure range (2 ÷ 12) MPa, after which the constants in the law of the burning rate were calculated. The specific impulse of the fuel compositions was calculated according to the ASTRA-4 program. The content of solid combustion products was determined by burning samples in the open air at room temperature and taking condensate in a quartz sampler.

To solve this problem, fuel compositions were studied that differ in the nature of metallic fuel. The compositions used mixtures of aluminum powders ASD-1 and ALEX, taken in the ratio 9: 1, 1: 1, 1: 9, and fuels in which ASD-1 was completely replaced by ALEX (0:10). The metal fuel content in the fuel compositions, regardless of nature, was 15 wt.%.

The research results are given in table.3.

Table 3 Characteristics of the developed compounds Characteristic Content ASD-1 / "ALEX" 10: 0 9: 1 1: 1 1: 9 0:10 Burning rate at 4.0 MPa, mm / s 4.4 ± 0.1 5.4 ± 0.2 7.5 ± 0.2 7.6 ± 0.2 7.7 ± 0.2 u, mm / s 0.9 1.2 2.0 2.1 2.2 ν 0.43 0.41 0.46 0.35 0.34 Specific impulse, s 233 233 233 233 233 z, wt.% 20 ÷ 25 17 ÷ 20 10 ÷ 12 10 ÷ 12 10 ÷ 12

The calculated specific impulse depends on the quantity and chemical nature of the metal fuel and does not depend on the dispersion of the metal. Therefore, for all studied systems, the specific impulse is constant.

Comparison of the results obtained (Table 3) with the characteristics of the prototype (Table 2) showed that as the ALEX fraction in the metal fuel increases, the burning rate increases, the exponent in the combustion law and the content of solid combustion products decrease. So, with the complete replacement of ASD-1 with "ALEX", the burning rate of fuels at 4 MPa increases by 1.75 times, the exponent in the law of burning rate decreases by 1.27 times, and the content of solid combustion products at atmospheric pressure decreases by almost half.

It should be noted that fuel compositions containing at least 50% “ALEX” in metallic fuel are close in their characteristics to compositions containing “ALEX”. Since the ultrafine aluminum powder "ALEX" is an expensive product, from the point of view of reducing the cost of fuel compositions, it is advisable to use a mechanical mixture of aluminum powders of the ASD-1 and "ALEX" grades in the ratio 1: 1 as metal fuel.

Comparison of the properties of the proposed composition with fuels containing ASD-1 and "ALEX" grades of initial aluminum as a metal fuel (Tables 1 and 2) showed that the characteristics of the developed composition almost coincide with the characteristics of systems containing "ALEX".

The discrepancy in the values of the determined values is not more than (3-6)%. So, the burning rate of the proposed composition at 4.0 MPa increases 1.7 times in comparison with systems containing ASD-1, the rate in the law of the burning rate decreases by 1.2 times, and the content of solid combustion products decreases by half. For systems containing the original "ALEX", these values are 1.75, 1.27 and 2.0, respectively.

The reduction in the content of "ALEX" in metal fuel by half contributes to a significant reduction in the cost of the fuel composition, which allows us to offer the developed composition for industrial use.

LITERATURE

1. Energy Condensed Systems: A Brief Encyclopedic Dictionary / Ed. B.P. Zhukova. - M .: Janus-K, 2000 .-- 596 p.

2. Sarner S. Chemistry of rocket fuels. - M .: Mir, 1969 .-- 488 p.

3. Paushkin Y.M. Liquid and solid chemical rocket fuels. - M.: Science, 1978-192 p.

4. Milekhin Yu.M., Larionov B.I., Pardyanov N.N. et al. Feasibility studies on the development of low-cost solid rocket fuels and increased environmental safety for mid-flight propulsion systems and solid-fuel boosters of space-rocket complexes // Izvestiya RARAN. 2004, No. 2 (39). - S. 82-87.

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

6. Arkhipov V.A., Bondarchuk S.S., Korotkikh A.G., Lerner M.I. Production Technology and Dispersed Characteristics of Aluminum Nanopowders // Mining Journal - Non-Ferrous Metals (Special Issue). 2006, No. 4. - S. 58-64.

7. Arkhipov V.A., Popok V.N., Popok N.I., Savelyeva L.A. Combustion of metallized fuel compositions based on ammonium nitrate. // V International School-Seminar. "Intra-chamber processes, combustion and gas dynamics of disperse systems." St. Petersburg. 2006. - S.10-13.

8. Di-N-oxide-1,3-dinitrile-2,4,6-triethyl-benzene. TU 2471-307-05121441-98, SKTB "Technologist", St. Petersburg.

Claims (1)

Solid fuel composition based on ammonium nitrate, containing ammonium nitrate, rubber grade SKDM-80, aluminum powder and hardener di-N-oxide-1,3-dinitrile-2,4,6-triethyl-benzene, characterized in that the composition contains a mixture aluminum powder grade ASD-1 and ultrafine aluminum grade ALEX in a ratio of 1: 1 with the following components, wt.%:
ammonium nitrate 71.8 rubber of the SKDM-80 brand 13,2 aluminum powder brand ASD-1 7.5 ALEX brand aluminum powder 7.5 di-N-oxide-1,3-dinitrile-2,4,6-triethyl-benzene 0.1 over 100%