FR2626272A1 - Liquid fuels for rocket engines with aerobic combustion chambers and processes for their manufacture - Google Patents

Abstract

A new fuel for rocket engines with aerobic combustion chambers. According to the invention this fuel consists of solid particles of at least one heavy hydrocarbon in suspension in a hydrocarbon liquid which is not a solvent for the heavy hydrocarbon. Application: weapon propulsion.

Description

 The invention relates to liquid fuels for propellants with aerobic combustion chambers.

 In one such propeller, the (or ales) combustion chamber is fed, on the one hand, by the air in which the vehicle equipped with the propellant evolves, and, on the other hand, by a liquid fuel which is injected directly into the room. of combustison. or upstream of the combustion chamber, in one or more ducts bringing the combustion air into the combustion chamber.

 We have been looking for many. years .create heavy fuels consisting of hydrocarbons having a density greater than unity while retaining the characteristics, chemical and physical compatible with the fields of use of the propellant: indeed, any increase in density translates, at equal volume, by an increase in the on-board weight, therefore an increase in performance with a constant calorific value and constant combustion efficiency.

On the other hand, these heavy fuels have a certain number of drawbacks, summarized below: their viscosity is high (all the higher as their density is high), which poses problems in the fields of use of the thruster , the temperature in particular being able to vary between -50 ° C. and + 60 ° C. - their chemical properties may be incompatible with the constituent materials of the injection circuits; - Problems, which are thought to be related to high viscosity, arise in the combustion efficiency of molecules that are more carbon loaded than those of light conventional fuels (of the kerosene kind); - their average price is relatively high by..reference to the price of light conventional fuels (of the kerosene type)
The object of the invention is precisely a liquid fuel which remedies, at least partially, the disadvantages mentioned above.

 The subject of the invention is a heavy liquid fuel having a density greater than unity. a viscosity whose value varies as little as possible in a temperature range of -50 ° C to + 60 ° C, and whose combustion efficiency allows a power. mass heat than that of a conventional light fuel (such as kerosene for example).

 The fuel according to the invention consists of a suspension of solid particles in a liquid supplemented with a gelling agent in proportions such that this suspension has a strong thixotropic gel structure, and it is characterized in that the solid particles are particles of at least one heavy hydrocarbon suspended in a hydrocarbon liquid which is not a solvent for the heavy hydrocarbon.

 Thanks to this characteristic of strong thixotropy, the fuel according to the invention has a high static viscosity and a low dynamic viscosity, close to the viscosity of the hydrocarbon liquid.

 The dynamic viscosity of this fuel varies in very small proportions in a temperature range of -500 to +600 C.

 On the other hand, the static viscosity of this fuel is that, stored at room temperature (or at a temperature above room temperature), it remains stable for more than six months.

 Advantageously, the suspension of solid particles of heavy hydro carbide in the hydrocarbon liquid may consist, by weight, of 60% to 80% of solid hydrocarbon particles lonr and 40% to 20% of hydrocarbon liquid; this suspension is then completed by addition of a gelling agent in the proportion, by weight, of 0.3% to 1% of the total.

 It has been found that with a proportion of 70% heavy hydrocarbon solids, mechanical properties are maintained.

which allow a completely satisfactory injection; this proportion of 70% can also be increased without affecting the quality of the injection.

 The hydrocarbon liquid should not be a solvent for the heavy hydrocarbon solids because the temperature solubility varies with the precipitation of the solid hydrocarbon at low temperatures; this precipitation then modifies the mechanical properties of the suspension and the fuel loses the property of injectable eta.

 Finally, it should be pointed out that the heavy hydrocarbon suspension in the hydrocarbon liquid is obtained from solid particles whose maximum diameter is less than 250 μm.

The invention also relates to a fuel fabrication process having the characteristics defined below.
According to this process, the hydrocarbon liquid is placed in a container subjected to the action of a stirring device, the gelling agent is gradually introduced, the container is always subjected to the action of the stirring device, the particles are gradually introduced. hydrocarbon solids, the container being always subjected to the action of the stirring device, the stirring device is then stopped and the container is placed in an oven at a temperature above room temperature (400 to 600 ° C.) for a period of time. at least 24 hours, and the fuel obtained is stored at room temperature.

 According to a variant of this process, the hydrocarbon liquid is placed in a container subjected to the action of an agitator device, the gelling agent is gradually introduced, the container always being subjected to the action of the stirring device, and it is stopped. then the stirring device and the container is placed in an oven at a temperature above room temperature for a period of at least 24 hours, - the solid particles of hydrocarbon are introduced gradually, the container being again subjected to the action of the stirring device, the stirring device is then stopped and the container is placed in an oven at a temperature above room temperature (400 to 600 ° C.) for a period of at least 24 hours, and the fuel obtained is stored at ambient temperature.

 It should be noted that the fuels thus obtained, thanks to their properties of strong thixotropic gels, reduce the problems of sloshing in the tanks.

 It should be pointed out that, in order to facilitate the dispersion of the solid hydrocarbon, a wetting agent which contributes to the stability of the system can be mixed with the solid hydrocarbon particles.

 The invention consists, apart from the provisions just mentioned, in certain other provisions which will be more explicitly described below.

 The invention may, in any case, be well understood with the aid of the additional description which follows, and which relates to preferred embodiments of the invention does not include, of course, any limiting character.

 To produce a fuel consisting of a suspension of solid particles of heavy hydrocarbon in a hydrocarbon liquid, it is advantageous to use the following compounds - particles consisting of anthracene (density 1.25), fluorene (density 1 , 20), or chrysene (density 1.27), - liquid consisting of kerosene (C1oH2O - density 0.7 or a mixture a, 6 pinene (C1OH16 - density 0.86).

 The weight proportions are between 60% and 80% of solid hydrocarbon particles and 40% and 20% of hydrocyclic liquid.

 The gelling agent which supplements such suspensions is then added in the proportion by weight of 0.3% to 1% of the total, this gelling agent may consist of aluminum octoate.

 The following heavy fuels can be obtained - Combustible No. 1: suspension of 60% by weight of anthracene in 40% by weight of kerosene, all supplemented with 0.5% by weight of aluminum octoate and 1% of triton; the density of this fuel nO 1 is then 1.01.

Fuel # 2: suspension of 70% by weight of anthracene in 30% by weight of kerosene, the whole supplemented with 0.5% by weight of aluminum octoate and 1% of triton; the density of this fuel n0 2 is then d6- 1.06.

Fuel No. 3: suspension of 60% by weight of anthracene in 40% by weight of α-6-pinene mixture, all supplemented with 0.5% by weight of aluminum octoate; the density of this fuel nO 3 is then 1.05.

Fuel 4: suspension of 70% by weight of anthracene dane 30% by weight of mixture a, B pinene, all supplemented with 0.5% by weight of aluminum octoate, the density of this fuel nO 4 is then 1.10.

Fuel 5: suspension of 70% by weight of fluorene in 30% by weight of kerosene, the whole supplemented with 0.4% by weight of aluminum octoate and 1% of triton; the density of this fuel is then 1.03.

Fuel 6: suspension of 78% by weight of anthracene in 22% by weight of kerosene, the whole supplemented with 0.4% of aluminum octoate and 1% of triton; the density of this fuel is then 1, 10.

Fuel 7: suspension of 70% by weight of chrysene in 30% of kerosene, all supplemented with 0.5% of aluminum octoate and 1% of triton; the density of this fuel is then 1.07.

In the table below, a comparison has been made of the characteristics of the fuels according to the invention, n 1, n 2, n 3, n 4, n 5, n 6 and n 7, with some known synthetic fuels. day, namely RJ6 kerosene, Ramjet fuel
RJ1, RJ9A fuel and RJ9B fuel.

<Tb>

Fuel <SEP> Mass <SEP> Heat <SEP> of <SEP> Heat <SEP> of
<tb><SEP> volume <SEP> combustion <SEP> combustion
<tb><SEP>(<SEP>:<SEP>:<SEP> volume <SEP> mass
<tb> cal / cm3 <SEP> cal / g
<tb>(<SEP> n <SEP> 1 <SEP>: <SEP> 1.01 <SEP>: <SEP> 9796 <SEP>: <SEP> 9728
<tb>(<SEP> nO <SEP> 2 <SEP> 1.06 <SEQ> 10210 <SEP> 9646
<tb>(<SEP> nO <SEP> 3 <SEP>: <SEP> 1.05 <SEP>: <SEP> 10391 <SEP>: <SEQ> 9822
<tb> n <SEP> 4 <SEP> 1.10 <SEP> 10698 <SEP> 9726
<tb> n <SEP> 5 <SEP> 1.03 <SEP> 10100 <SEP> 9757
<tb><SEP> n <SEP> 6 <SEP> 1.10 <SEP>: <SEP> 10600 <SEP> = <SEP> 9636
<tb> n <SEP> 7 <SEP>: <SEP> 1.07 <SEP>: <SEP> 10306 <SEP>: <SEP> 9632
<tb> Kerosene <SEP> RJ6 <SEP> 0.78-0.80 <SEP>: <SEP> 8278 <SEP>: <SEP><SEP> 10220
<tb> (Ramjet <SEP> RJ1 <SEP>: <SEP> 0.853 <SEP>: <SEP> 8787 <SEP>: <SEP> 10301
<tb><SEP> RJ9A <SEP> 0.94 <SEP> 9592 <SEP> 10204
<tb> RJ9B <SEP> 0.987 <SEP> 10191 <SEP> 10390
<Tb>
It can be seen that the fuels according to the invention have densities of between 1 and 1.10.

 In addition, these fuels are injectable under the same conditions as conventional fuels but have heats of combustion volume higher than those of conventional fuels.

 The results of comparative tests relating to the injection properties of the liquid fuels according to the invention are given below taking as a reference the injection property of kerosene.

 For the tests, it has an injection rod, provided at its end, a transverse injector with a diameter of 0.6 mm.

The liquid injection pressure is 10 bar and the flow rates are measured. The flow coefficients reported for kerosene are calculated. The table below summarizes the results.

<Tb>

Fuel <SEP> Flow <SEP> Coefficient
<tb> g / s <SEP> of <SEP> debit
<tb> Kerosene <SEP> 8.5 <SEP> 1
<tb><SEP> n <SEP> 1 <SEP> 7 <SEP> 0.82
<tb> n <SEP> 2 <SEP> 5.5 <SEP> 0.65
<tb><SEP> n <SEP> 4 <SEP> 5.5 <SEP> 0.65
<tb><SEP> n <SEP> 5 <SEP> 6.5 <SEP> 0.76
<Tb>
As for the prices of the synthetic heavy fuels, they are higher than the prices of the fuels according to the invention which are obtained thanks to products of large diffusion, thus inexpensive.

 It is also possible to obtain a fuel whose characteristics are determined (density and / or combustion efficiency) by choosing, for the solid particles of heavy hydrocarbons, a mixture of different heavy hydrocarbon particles.

 For example, in fuel No. 6, 78% by weight of anthracene could be replaced by 60% by weight of anthracene and 18% by weight of fluorine.

 We will now give, by way of example, the various stages of the manufacture of a fuel according to the invention.

 If it is proposed to manufacture 1000 g of this fuel, proceed as indicated below - a solid hydrocarbon (anthracene) is ground and sieved to retain only particles of diameter between 100 pm and 250 pm - a hydrocarbon liquid (300 g of kerosene) is placed in a 1500 cm3 container subjected to the action of a stirring device; a gelling agent is gradually introduced, the container always being subjected to the action of the stirring device; this gellant (3 to 7.5 g of aluminum octoate) is introduced for a time of about 2 minutes and it represents, by mass, 1% to 2.5% of kerosene and 0.3 to 1 % of the fuel finally obtained - 700 g of solid particles of anthracene are gradually introduced, the container being always subjected to the action of the stirring device: the introduction time is about 5 minutes - to facilitate this operation, the mixture is mixed with particles of anthracene a wetting agent which can be constituted by triton, and in mass proportions of 0, 5% - then stops the stirring device and the container is placed in an oven at 600C for 24 hours - et.on stores the fuel obtained at room temperature.

 According to the variant of this method indicated at the beginning of the description, it is possible to proceed to the. Gelation of the kerosene and then introduce the anthracene particles.

Claims (12)

 1.- Fuel for an aerobic combustion chamber propellant, constituted by a suspension of solid particles in a liquid supplemented with a gelling agent in proportions such that this suspension has a strong thixotropic gel structure, characterized in that the particles Solids are particles of at least one heavy hydrocarbon suspended in a hydrocarbon liquid which is not a solvent for the heavy hydrocarbon.  2. Combustible according to claim 1, characterized in that the suspension of solid particles of heavy hydrocarbon in the hydrocarbon liquid is constituted by weight by 60 to 80% of solid particles of heavy hydrocarbon and 40 to 20% of liquid hydrocarbon, this suspension being completed by addition of a gelling agent in the proportion by weight of 0.3 to 1% of the total.  3. Combustible according to claim 1 or 2, characterized in that the solid particles of heavy hydrocarbon have a maximum diameter of less than 250 μm.  4. Combustible according to any one of claims I to 3, characterized in that the heavy hydrocarbon is anthracene, fluorene or chrysene.  5. Combustible according to any one of claims 1 to 4, characterized in that the hydrocarbon liquid is kerosene or a mixture a, ss pinene.  6. Fuel according to any one of claims 1 to 5, characterized in that the gelling agent is aluminum octoate.  7. Combustible according to any one of claims 1 to 6, characterized in that it further contains a wetting agent in the proportion of 0.5 to 1%.  8. Fuel according to claim 7, characterized in that this wetting agent is triton.  9. A process for manufacturing a fuel according to any one of claims 1 to 8, characterized in that it comprises the following stages - the hydrocarbon liquid is placed in a container subjected to the action of a stirring device - the gelling agent is introduced gradually, the container being always subjected to the action of the stirring device - the solid particles of hydrocarbon are progressively introduced, the container being always subjected to the action of the stirring device; then stops the stirring device and the container is placed in an oven at a temperature above room temperature for a period of at least 24 hours, and the fuel obtained is stored at room temperature.  10. A method of manufacturing a fuel according to any one of claims 1 to 9, characterized in that it comprises the following steps - the hydrocarbon liquid is placed in a container subjected to the action of a device. agitator, the gelling agent is gradually introduced, the container being always subjected to the action of the stirring device, the stirring device is then stopped and the container is placed in an oven at a temperature above room temperature for a period of At least 24 h, the solid particles of hydrocarbon are gradually introduced, the container being again subjected to the action of the stirring device, the stirring device is then stopped and the container is placed in a higher temperature oven. at ambient temperature for a period of at least 24 hours, and the fuel obtained is stored at room temperature.  11. A process according to claim 9 or 10, characterized in that a wetting agent is mixed with the solid hydrocarbon particles.  12. A process according to any one of claims 9 to 11, characterized in that, to manufacture 1000 g of fuel, the time of introduction of the gelling agent into the hydrocarbon liquid is about 2 minutes, the time of solid hydrocarbon particles introduction is about 5 minutes, and the temperature of the étuse is about 600C.