DE2050302C3 - Fuel block and process for its manufacture - Google Patents

Description

to achieve the optimum ratio of an energetic light metal! pui \ cr, compared to that of the Base component of the block acts as a binder, it is important that the particles of this powder during

. ^6o very short time (on the order of 10 " ³ see)

The invention relates to a fuel block and, by reacting with the oxidizing agent, to a process for its manufacture. Fuel blocks The moment when the particles are freed from their combustible light metal powder with a high combustion * binding agent, they burn completely at temperature or consist essentially of such during the time in which they are released in this way. Such blocks may be made ⁶ S particles in the combustion chamber are, containing an oxidizing agent at least in part: ,, which for their combustion Among the causes that a delay in the

voltage necessary t _Is or conversely reduzie- combustion of the metal, in the combustible, his orga rend, wherein lead to the combustion together with the African binder particles contained kön-

The following can be mentioned in particular: a relatively low temperature of the immediate, generally reducing environment; the presence of a shell made from a residual builder, by which the surface of the particles is maintained or protected for a period of time; and the possible presence of an oxide layer on the particles during their incorporation into the organic, flammable binders.

The object of the invention is to increase the combustion temperature of the metallic particles and to rid them of any shell (of a binder skeleton or an oxide) that would hinder the combustion reaction of the particles with the oxidizing agent will.

The subject of the invention is thus a fuel block with a powder of at least one of the oils ^; chtmetals beryllium, magnesium, aluminum and the semimetals boron and silicon, which burn by reaction with an oxygen-entangling combustion agent, which is characterized in that the surface of each particle of the metal powder is coated with a discontinuous layer of a fluorinated carbon compound, which at a temperature , which is significantly lower than the combustion temperature of the fuel block in the intended combustion agent, with which the metal forming the particles can react in an exothermic primary reaction.

According to the invention, this fuel block is produced by applying the coating substance the light metal particles in the form of a suspension of a powder of the coating substance in a liquid brings up.

The limited primary reaction between the metallic particles and the coating substance takes place at the same time a preheating of the particles as well as a cleaning of their surface, whereby the initiation of the Main combustion reaction accelerates and combustion efficiency is improved. Because a coating is present according to the invention in the form of a discontinuous layer, this can be avoided be that the coating substance forms a thermal protection that initiates the reaction the substance with the metal particles is delayed. At the same time there is also free access to the oxidizing agent to the metal parts guaranteed.

According to an expedient embodiment, the following measures in particular should be taken will:

The ratio of coating substance to light metal between the metal powder and that produced by the coating substance added halogen should preferably be 30 to 80: 1.

The structure of the coating substance layer must not form a continuous envelope, but rather the shape form a network of spheres that consist of a powder suspension of the coating substance in a liquid has been applied.

The light metal powder can form the main component of the block in a rocket fuel, preferably water is used as the combustion agent. Here, the shell subslance facilitates of the metallic powder grains, the agglomeration of the grains during the manufacture of the ingot. the Dimensions of the particles of light metal powder, which can be spherical or lamellar, should be between 3 and 40 μ.

The diameter of the beads is preferably 0.1 to 0.5 μm, particularly 0.3 μm.

As for the method of incorporation of the powder of light metal, previously with the halogenated carbon substance has been coated in the organic, flammable compound is concerned, this is preferably done at a temperature at which the organic compound is liquefied, the substance then being is mixed as a liquid phase with the compound.

ίο At atmospheric pressure, aluminum oxide (AUO ₃ ) only melts at 2080'C, while aluminum fluoride is sublimated at 129TC. Beryllium oxide (BeO) is sublimated off by melting at 2530 C, beryllium fluoride at 800 C.

If the base of the fuel block is a solid organic compound, this preferably consists of an amine if the fuel blocks are to be used in a hybrid rocket fuel. Metatoluenediamine, which is combined with a polyamide plasticized with cyclohexyl phthalate, is preferred is. This composition is referred to below as "NMTD".

The weight fraction of the coated light metal powder in the fuel block is preferably

j5 between 20 and 40% and here again preferably at about 30%.

In fuel blocks based on NMTD, the metal particles are preferably coated with a polyfluoroethylene, in particular polytetrafluoroethylene, C ₂ F ₄ , which is commercially available as stable aqueous suspensions of colloidal spheres made of polytetrafluoroethylene with granule dimensions of 0.1 to 0.4 μ are available.

The application of the polytetrafluoroethylene spheres on the metal particles can be done before or after incorporation into the amine.

In order to work as advantageously as possible, it is expedient to proceed as follows: The amine is liquefied with stirring: the metal powder becomes

u> after intimate mixing with the coating substance incorporated into the liquefied amine; heating occurs at a temperature at which the water is removed and the granules of the coating substance precipitate on the metallic particles, after which the mixture is converted into . given a mold and cooled until completely solidified.

For further explanation, 5 sample series will be described, which relate to fuel blocks for Sourcing hybrid rocket fuels, with the chemical

see the composition of the Biennstoffblock and the of the corresponding combustion agent varies from sample series to sample series.

First series of examples

In the first series of examples, the base of the fuel block is NMTD 96/2/2 (96% metatoluene diamine, 2% polyamide and 2% butylphihalate). Lr is enriched with aluminum powder, the combustion agent is nitric acid (HNO ₃ ).

The first row examples have the following procedural features in common:

a) The NMTD 96/2/2 is stirred until it has completely melted to a temperature of

^fi 5 140 ° C;

b) During this time, the aluminum powder is intimately mixed with a Polytetrafiuoräthylen, where water is optionally added to

to get a slightly fluid mixture. The proportions of aluminum powder and polytetrafluoroethylene depend on the desired characteristic mixing ratio ψ;

c) The mixture produced according to b) becomes steady with the melted NMTD produced according to a) added and brought to a temperature of 105 C. The water is on it by heating eliminated while the polytetrafluoroethylene precipitates on the aluminum grains;

d) the product obtained is brought back to a temperature of 105 "C, whereupon it was placed in a mold and the block thus obtained was cooled will.

With these common conditions we should take more the examples are described in detail.

example 1

Aluminum of spherical grains with an average grain size of 5 µ: 28.25%; Polytetrafluoroethylene: 1.75%; NMTD: 70%.

The mixing ratio ψ of the block obtained is 45: 1 and its combustion efficiency is 96%.

Example 2

This example differs mainly from the previous one in that u.j shares of Aluminum and polytetrafluoroethylene are 28.1% and 1.9%, respectively.

The mixing ratio ψ of the block obtained is 40: 1 and its combustion efficiency is 98.5 ";

Example 3

This example differs from the previous ones in that the proportions of aluminum and polytetrafluoroethylene are 28.4 and 1.60 percent, respectively.

The mixing ratio ψ of the block obtained is 50: 1 and its combustion efficiency is 92%.

Example 4

Aluminum from lamellas with an average of 14μ: 28.1%; Polytetrafluoroethylene: 1.9%; NMTD: 70%.

The mixing ratio of the block obtained is 40: 1 and its combustion efficiency is 99%.

Example 5

This example differs from the previous one in the mean dimension of the aluminum lamellas (44 μ) and because the proportions of aluminum and polytetrafluoroethylene are 28.7 and 1.3%, respectively be.

The mixing ratio φ of the block obtained is 60: 1, its combustion efficiency 98%.

Second series of examples

In the second row of examples, the base of the fuel block is polybutadiene and it is enriched with aluminum powder. The combustion agent is hydrogen peroxide (H ₂ O ₂ ) with a maximum concentration of 98 ".

The polytetrafluoroethylene coated aluminum is made by adding the aluminum powder and the polytetrafluoroethylene are intimately mixed. If necessary, water is added to it is removed by evaporation at low temperature, possibly in a vacuum.

The aluminum powder coated with polytetrafluoroethylene is then mechanically dispersed and in Polybutadiene introduced to which a crosslinking agent is added. The mixing ratio is chosen so that that the calculated characteristic mixing ratio results. The mixture obtained in this way is finally poured into a mold and crosslinked at a suitable temperature.

Example 6

'

The grain size of the aluminum powder (spherical grains) used is 5 µm. The shares are aluminum: 28.1%; Polytetrafluoroethylene 1.6% and polybutadiene 70.3%.

The mixing ratio ψ of the block obtained is 40: 1, its combustion efficiency 98%.

Example 7

Lamellar aluminum powder with an average size of 14 μ: 28.1 °; Polytetrafluoroethylene 1.9%; Polybutadiene 70%.

The mixing ratio 7 of the block obtained is 40: 1, its combustion efficiency 99%.

Third series of examples

The third series of examples relates to the special case in which the fuel block consists essentially of a powder made of a light metal, e.g. B. aluminum powder, and in which the combustion agent is water, which reacts exothermically with aluminum at elevated temperature, so that aluminum oxide and hydrogen are formed with continuous combustion.
The manufacturing process of the aluminum powder coated with polytetrafluoroethylene is the same as in the second series of examples, mi; the difference is that the proportions are selected in a range that corresponds to a mixing ratio of 7, which is significantly lower (mean value of 7 in the order of magnitude of 10: 1).

The aluminum coated according to the second series of examples is then compressed to form fuel blocks to maintain their cohesion through that of the polytetrafluoroethylene sheath that holds each granule of aluminum powder surrounds is improved. Such blocks are particularly suitable for underwater propulsion, which are provided with a suitable ignition device that makes it necessary for combustion of aluminum in the presence of water to reach the necessary temperature.

Example 8

Aluminum powder with spherical grains of

on average 5 μ, which are coated with polytetrafluoroethylene. Proportions: aluminum 78.26%, polytetrafluoroethylene 21.74%. The block is made by compression at 250 kg / cm ² .

The mixing ratio ψ of this block is 10: 1 with a combustion efficiency of 70%.
60

Example 9

The pulser used is a casting powder made of aluminum (71) "J and magnesium (30%) from spherical grains with an average size of 44 μ. This alloy powder is coated with the following proportions with polytetrafluoroethylene: alloy powder 77.07 · ',", polytetrafluoroethylene * 22.93%. The block is compressed by hpi 700 ku / rrn ²

20th

The mixing ratio of this block is 10: 1, its combustion efficiency 78%.

Four series of examples

These examples relate to beryllium powder enriched fuel blocks for hybrid rocket motors.

Example 10

Berylium powder with spherical grains of 30 μ in size is used as the metal powder. As in of the previous series of examples is the basis of the Blockes NMTD, the processes for coating and incorporating the metal powder are the same. The The combustion agent is nitric acid or nitrogen peroxide or a mixture thereof. The shares are the following:

Beryllium ²¹ ' ^A \ ° 6

Polytetrafluoroethylene ² > ⁵⁵ / o

NMTD 96/2/2 ⁷⁰ %

The mixing ratio ψ of the block obtained is 60: 1.

E. Example 11

Beryllium powder with spherical grains of 20 μm in size is used as the metal powder. the As in the second series of examples, the baris of the fuel block is polybutadiene, the coating process and introducing the metal powder are the same 3 <> chen. The combustion agent is hydrogen peroxide at a concentration of 98%. The proportions of the The composition is as follows: \

Beryllium 32 ",,

Polytetrafluoroethylene 3 ""

Polybutadiene 65%

The mixing ratio 7 of the block obtained is 60: 1, the combustion effect is over 90%.

Fifth sample series

In the following two examples for the compositions of fuel blocks are given, which contain the oxidizing agent (powder) necessary for their combustion. The coating and bringing in of the metal powder into the binder are carried out in the same way as in the second series of examples.

Example 12

Ammonium perchlorate 60%

Binder (polyurethane) 20%

Aluminum powder

(Granule size 5 μ) 18.83%

Polytetrafluoroethylene 1.17%

The mixing ratio φ is 60: 1.

Example 13

Aluminum perchlorate 70%

Binder (polybutadiene) 15%

Beryllium powder

(Granule size 20 μ) 13.5%

Polytetrafluoroethylene 1.5%

The mixing ratio φ is 50: 1.

709 617/14 «

Claims (8)

Fuel block another oxidizing or in the Claims: Fluid phase assimilated constituent may be present must, the one in the conditions of use with the I. fuel block mi. a powder from little-fuel block can react. This is the case with at least one of the light metals beryllium, magne- 5 hybrid rocket propellants (rocket propellants with sium, aluminum, as well as the semimetals boron and a solid fuel content and a liquid silicon, those by reaction with an oxygen burning agent) and, in particular, with hypergolia-containing Burn combustion agents, d a - see hybrid fuels. characterized in that the upper draws the latter type of hybrid propellants surface of each particle of the metal powder with ein-f 10 is characterized by the fact that the reaction between the discontinuous layer of a fluorinated two components (solid and liquid) of the fuel Carbon compound is coated. which occurs spontaneously at a temperature when used together-temperature, which is much lower than that to be brought. Combustion temperature of the fuel block in US Pat. No. 32 03 171 relates to a provided combustion agent with which the 15 fuel, which is intended to contain a fluorinated particle forming metal to be used in an exothermic combustion agent, the Primary reaction can react. automatic detachment of the superficial oxides 2. Fuel block according to claim I, thereby ensuring the grains. There was therefore no indication that the coating requirement ratio, in this case a special coating substance to light metal φ between the metal substance for dissolving these superficial oxides powder and the coating substance drawn by the coating substance was to be provided. In contrast, in the case of the invention, the led halogen is 30 to 80: 1. Fuel intended to be used with an oxygen-containing 3. Fuel block according to claim 2, characterized gene to react combustion agent, and it is therefore characterized in that the value 91 is 40: 1. necessary according to the invention, one for each metal grain 4. Fuel block according to claim 1 to 3, da- * 5 provide special coating substance to the characterized in that the fuel block detachment of the oxide and the triggering of the burners to provide the powder from at least one easing reaction. metal is a flammable, organic, with room- The coating substance according to the USA.-patent- temperature fixed and with the incineration writing 34 20 695 has the desensitization of metaldes Fuel block selected oxidant 3 ° grains to the task. For this purpose the Contains burning compound, the Ge coating of a substance that does not relate to the metal weight fraction of the light metal powder reacts between grains. 20 and 40%, and preferably about 30%. According to French patent specification 13 18 773 5. The fuel block according to claim 4, thereby turning the aluminum grains into an inhibitor characterized in that the combustible organic envelopes 35 which counter-bind the reaction of the aluminum is an amine compound that is preferred over an oxygen-containing combustion agent, wisely consists of metatoluenediamine, the mi; one that is air, delayed (see p. 2, right column, line 1 plasticized polyamide is connected. and 2 and last line). In contrast, the invention 6. Fuel block according to claim 1 to 4, since the coating substance in the case of energy through characterized in that the dimensions of the 40 rich metals (especially aluminum) excluding particles of light metal powder between 3 and lent the role of an accelerator of the reaction against -40 μ lie. over an oxygen-containing combustion agent. 7. Fuel block according to claim 1 to 4, to simplify the description and avoid it characterized in that the coating substance is made up of ambiguities in the following from spheres with a diameter between 45 the metals or elements beryllium, magnesium, boron, 0.1 and 0.5 μ and preferably in the vicinity of aluminum and silicon referred to as light metals. 0.3 μ exists. Fuel blocks, which are a powder from an energetic 8. A method for producing a fuel table contains light metal, in particular a combustion block according to claim 1, characterized in that blocks of material with a combustible organic compound you have the coating substance on the light 5o manure, which burns with an oxidizing agent Metal particles in the form of a suspension are known to have better burning performance, the Powder of the coating substance in a liquid, optimal weight proportion of this powder in the fuel brings up. in particular the thermal properties of the considered energetic light metal is dependent. 55 In order to improve the combustion of a fuel block