RU2526670C2 - Device for determination flammability parameters of structural non-metal materials during space flight for conditions of inhabited pressure compartments of spacecrafts and planetary stations - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to fire protection of inhabited pressure compartments of spacecrafts. Additional container with gas working medium is placed adjacent to sample combustion chamber made in the form of cylinder. The combustion chamber at its both ends is connected with additional container by openings for working gas medium passage when closed loop of its motion is created. The combustion chamber and additional container are equipped with plate-type heat exchangers one of which is located in combustion chamber between the axis of centrifuge rotation and sample of material being tested, and the other one - in additional container between the axis of centrifuge rotation and working gas medium outlet from combustion chamber. Opening at the side of working gas medium inlet into combustion chamber is closed by grid made of incombustible material with low hydraulic resistance. Openings between combustion chamber and additional container at each end of combustion chamber are made with port areas not less than combustion chamber cross-sectional area in the region of tested material sample location.

EFFECT: determination of material combustion limits from gravity acceleration depending on oxygen concentration in spacecraft pressure compartment atmosphere.

8 dwg, 1 tbl

Description

The invention relates to ensuring the fire safety of inhabited pressurized compartments of spacecraft (hereinafter referred to as KLA) and alien stations (hereinafter referred to as IS) both in terms of preventing fires from occurring in them and in extinguishing them. This technical solution is intended to determine the indicators characterizing the fire hazard of structural non-metallic materials (hereinafter referred to as KNM) and substances in the conditions of inhabited pressurized compartments of manned spacecraft modules and structures intended for placement on other planets having an acceleration of gravity different from the earth’s, as well as for the development of methods and means of ensuring fire safety of the inhabited pressurized cells KLA and IS.

Fire hazard situations that took place at an early stage of space flights, as well as in pressurized compartments of other purposes, made fire hazard in inhabited pressurized spaceships one of the main dangerous factors for space flight (Space Flight Safety. G.T.Beregovoi et al. - M.: Mechanical Engineering , 1977 .-- 263 p.). The increased fire hazard of the inhabited pressurized spacecraft compartment is due to a combination of specific factors such as increased oxygen concentration (Cox) up to 30–40% (hereinafter,% by volume) in the working atmosphere of the pressurized compartment created during operation of oxygen regeneration systems; the use of a large number of KNM, determined by the requirement to reduce the mass of equipment KLA high saturation of pressurized compartments with electrical equipment, the elements of which during failures often became sources of fire in an oxygen-enriched atmosphere (Nakakuki A. / “Fires and fire-fighting measures in high-pressure and oxygen concentration chambers” // In the journal “Anzen Kogaku”. 1972, v.2, No. 5. - S.98-105. Translation from Japanese, No. Ts 21297. - 27 p.).

Most of the applied CNMs are combustible in an oxygen-enriched atmosphere. In a atmosphere enriched with oxygen, with a large amount of materials, the rate of development of a fire can significantly increase, which creates great difficulties in dealing with it. The crew of the spacecraft is almost impossible to provide outside assistance in case of fire in the pressurized compartment.

Piloted and other spacecraft are critical objects, because accidents, including fires in spacecraft, can cause great damage to the national interests of the country in many areas (GOST R 52551-2006 “Security and safety systems. Terms and definitions”).

Currently, one of the main tasks of astronautics is the creation of space bases intended for deployment on other planets, and primarily on the Moon and Mars. So, the USA plans to create a support base on the Moon for launching manned spacecraft on Mars (Yashlavsky A. / Space Odyssey 2015 // In the newspaper Moskovsky Komsomolets dated January 16, 2004). The high cost of building alien bases is noted. Similar projects are being worked out in different countries with developing cosmonautics and, naturally, in Russia. When developing projects, there are acute problems of ensuring the safety of people when they live and work on alien bases. Attendants will stay in inhabited pressurized compartments, for example, the Earth’s satellite for a long time. One of the problems in this case is the provision of highly reliable and low-cost fire safety of the inhabited pressurized modules of alien bases.

Known traditional methods are not suitable for ensuring the fire safety of inhabited pressurized vessels KLA and IS at an economically feasible level.

Using an approach that involves the use of non-combustible materials in an oxygen-enriched atmosphere, despite some success in this area (Zhevlakov AF et al. / “On the effect of the composition of a polymer material on its ability to burn” // Express information: Fire hazard of substances and materials, Ser. 1, issue 85 - M .: VNIIPO, 1976. - P.1-9), turned out to be extremely expensive and did not provide for the diverse needs of astronautics in structural materials with the necessary physical and mechanical properties.

Using the approach, which is the use of traditional fire extinguishing agents using almost all known extinguishing agents, was also unacceptable in connection with the following circumstances. The use of a fire extinguishing agent in an inhabited pressurized compartment during operation on Earth, in orbit and on another planet, in and of itself, regardless of the scale of the fire, is an emergency situation that can lead to disruption of the flight program and death of the inhabited pressurized compartment and spacecraft as a whole due to air pollution of the pressurized compartment and equipment. In particular, in the case of volumetric fire extinguishing (inert gases, chladones, carbon dioxide), the atmosphere of the pressurized compartment needs to be cleaned or replaced, and to continue the operation of the spacecraft, it is necessary to have powerful filters or nitrogen and oxygen reserves in the pressurized compartments.

With an increase in oxygen concentration in the atmosphere, the required supply of extinguishing agent increases many times (Kuzmenko KP, Kalinkin VI, Blinov AA / “Extinguishing polymer materials with gas extinguishing agents” // In the collection “Combustion and Extinguishing Issues” polymer materials ". M: 1989, p. 74-83). So, for volume quenching of many materials with an oxygen concentration in the atmosphere equal to 40%, more than 1 kg of sulfur hexafluoride per 1 m ³ of the pressurized compartment volume is required. Estimates showed that for a pressurized compartment with a volume of 80 m ^{3, the} mass of a volumetric fire extinguishing installation can be 200-250 kg. Delivery of only 1 kg of equipment to low Earth orbit now costs at least $ 20,000. The cost of delivering goods to another planet is incommensurably greater.

These circumstances necessitate the development of unconventional, highly reliable, economical and environmentally friendly methods and means of ensuring fire safety of the inhabited pressurized compartment KLA and IS, taking into account the specifics of their device and operating conditions.

Studies in the field of ensuring fire safety and the experience of implementing their results have shown that effective, with minimal material costs, ensuring the fire safety of inhabited pressurized compartments in a space object and at an alien station can be realized only on the basis of studying combustion processes taking into account the influence of the main factors characteristic of operation of inhabited pressurized compartments in space and on other planets: acceleration of gravity (g), oxygen concentration in the atmosphere, etc.

Ensuring the fire safety of the inhabited pressurized spacecraft and alien stations can be based on the following fire safety conditions:

$$C_{\lim .g}\ge K_s\cdot C_{ox.m};\left(\mathrm{one}\right)$$

$$g_{\lim .c}\ge K_s\cdot g_{pl};\left(2\right)$$

$$g_{\lim .c}\ge K_s\cdot g_{go};\left(3\right)$$

where C _lim.g is the combustion limit of materials by oxygen concentration at a given acceleration of gravity,%; C _ox.m — maximum possible (design) oxygen concentration in the atmosphere of GO,%; g _lim.c - lower combustion limit of materials for acceleration of gravity at a given oxygen concentration, cm / s ² ; g _pl - acceleration of gravity on this planet, cm / s ² ; g _go - the maximum possible acceleration of gravity in the inhabited pressurized spacecraft, cm / s ² ; K _s is the safety factor.

Conditions (1-3) ensure the selection of non-combustible materials for given oxygen concentration and acceleration of gravity in inhabited pressurized spacecraft and alien stations and fire extinguishing in inhabited pressurized compartments.

The fulfillment of conditions (1-3) for any material in different inhabited pressurized compartments can be established by the value of g _lim.c with knowledge of the dependence of g _lim.c on C _oh . Example Depending g _lim.c from C _ox for some materials is given in (Bolodyan IA, Ivanov AV, Melikhov AS / "Burning of solid non-metallic materials in microgravity." // Proceedings of the 5th symposium of Asia-Oceania on the science and technology of fire, Newcastle, Australia. December 3-6, 2001. - S.195-204).

The fulfillment of condition (1) for a given material can be achieved by determining, according to the indicated dependence, the value of the combustibility index of this material (C _lim.g ) and comparing it with the maximum possible oxygen concentration in the atmosphere of the pressurized compartment.

The fulfillment of conditions (2, 3) for the material can be achieved by determining the value of g _lim.c from the indicated dependencies and comparing it with the acceleration of gravity on this planet or with the maximum possible value of the acceleration of gravity in the inhabited pressurized spacecraft during maneuvers or in artificial mode gravity.

The existence of new combustibility indices of materials g _lim.c , C _lim.g , as well as the necessary value V _lim.с when developing this device, was established by purposeful studies of the combustion process under the influence of the main factors of space flight: the magnitude of the acceleration of gravity (including zero gravity (at g = 0)), oxygen concentration in the atmosphere, ventilation flow velocity (Bolodyan IA, Ivanov AV, Melikhov AS / “Combustion of solid non-metallic materials under microgravity conditions” // Materials 5 sim position of Asia-Oceania on the science and technology of fire. Newcastle, Australia. December 3-6, 2001. - S.195-204).

This contributed to the development of innovative and effective ways to ensure the fire safety of the inhabited pressurized spacecraft and IS (Patent of the Russian Federation No. 2116092 “A method for ensuring the fire safety of the inhabited pressurized spacecraft.” Priority of the invention dated 05.12.1995. Authors: Melikhov AS, Zaitsev S. N., Ivanov AV Published July 27, 1998. Bull. No. 21; patent of the Russian Federation No. 2284204 "Fire extinguishing method in an inhabited pressurized compartment of a spacecraft in orbital flight in artificial traction mode STI. ”Priority of the invention of April 9, 2004. Authors: Melikhov AS, Ivanov AV, Bolodyan IA Published on September 27, 2006. Bull. No. 27 (1 part); patent of the Russian Federation 2306965.“ A method of fire protection of inhabited pressurized compartments of spacecraft. "Priority of the invention dated 10.24.2005. Author: Melikhov AS Published on 09.27.2007. Bull. No. 27; patent of the Russian Federation No. 2319528" Method for ensuring fire safety of sealed compartments of residential modules of space bases on the moon". The priority of the invention from 04.17.2006. Authors: Kopylov N.P., Bolodyan I.A., Melikhov A.S. Published March 20, 2008. Bull. No. 8).

These developments represent a new technology in ensuring the fire safety of space technology. It formed the basis for ensuring the fire safety of the inhabited pressurized compartments of Russian spacecraft, including the Soyuz spacecraft and the Mir space station (SC) modules and the Russian segment of the international space station (PC MKC). The methods are based on the fulfillment of fire safety conditions (1-3).

For the further development of the new technology, it is necessary to improve the means of determining the combustibility indices of KNM for the conditions of inhabited pressurized compartment KL and IS.

Obviously, the most important for fulfilling the basic fire safety conditions for the use of materials and substances in inhabited pressurized compartments of KLA and IS (1-3) and establishing the extinguishing conditions in them is to determine the maximum dependence on the combustion of materials and substances - the value of g _lim.c on С _Oh .

Known devices for determining fire hazard of substances and materials at various concentrations of oxygen in the atmosphere. The work (Limit conditions for the gas-phase combustion of polymeric materials under vibration. / Kalinkin V.I. et al. // Physics of Combustion and Explosion. 1989, No. 4. - P. 47-49) describes a device for determining the combustion limit of materials by oxygen concentration (C _lim.g ) during terrestrial acceleration of gravity and vibrational overloads. The device includes a cylindrical combustion chamber, which was vertically mounted on a vibrating table. The sample of the test material is fixed in the combustion chamber using a holder, so that the axis of symmetry of the combustion chamber and the sample coincide. From below, a gas mixture with a predetermined flow rate and oxygen concentration was supplied from the mixer from the mixer. As a sample ignition source, a gas burner fed with combustible gas from a cylinder was used. To determine the value of C _lim.g , a gas flow with a certain initial oxygen concentration was created in the combustion chamber. If stable ignition of a sample of material was observed after ignition, then in the next experiment, the oxygen concentration in the mixture was reduced. Thus, the oxygen concentration limit for combustion was successively found below which stable burning of the material became impossible - C _lim.g.

Using the presented device, it is impossible even to approximately determine the lower limit of the burning of materials by acceleration of gravity - the value of g _lim.c , since experiments in this case can only be carried out with acceleration of the Earth's gravity equal to 981 cm / s ² and with vibrational overloads.

When resolving the issue of ensuring fire safety in an inhabited pressurized compartment of a spacecraft in orbital flight (patent of Russian Federation No. 2284204 “Fire extinguishing method in a inhabited pressurized compartment of a spacecraft in orbital flight in artificial gravity mode.” IPC А62С 3/08, B64G 9/00. Priority inventions dated April 9, 2004. Application No. 2004110913/12 Authors: Melikhov AS, Ivanov AV, Bolodyan IA Publ. 09/27/2006. Bull. No. 27 (1 h.)) for a number of different materials were determined by the dependence of the value of g _lim.c from C _oh . The work was carried out on a modified experimental setup (EI), the device of which is described in (On the limiting combustion regimes of polymers in the absence of free convection. / Melikhov AS, Potyakin VI, Ryzhov AM, Ivanov BA // Physics combustion and explosion. No. 4, 1983, - S.27-30). Different acceleration of gravity acting on the burning sample of the material was achieved by rotating the combustion chamber with the sample at different angular speeds using a centrifuge located in the container of the free-falling system. The time of zero gravity in a free falling system is limited. Therefore, using such a device, it was possible to determine the values of g _lim.c , for a narrow circle of materials with a short thermal relaxation time of the combustion zone - for, for example, materials burning in the gas phase without a solid residue. To determine g _{lim.c of} materials that form a coke residue during combustion, the method with a short period of zero gravity was unsuitable, since the cooling time of the combustion zone of these materials is several minutes and their extinction is not achieved in a short time of fall (weightlessness).

The values of fire hazard indicators of materials can be determined in experiments at the orbital station. In 1994-1998 astronauts conducted three series of experiments at the Mir space station to study the extreme conditions of combustion and quenching of materials during prolonged zero gravity in orbital flight. For this, the “Mir” ES “Speed” ES was created and installed in the pressurized module of the “Quantum” module. The ES “Speed” was a small wind tunnel, in the combustion chamber of which a cross section of 80 × 150 mm, a uniform flow of oxygen-enriched gas medium was created with a gas suction unit at a given speed: from 0.3 to 20 cm / s. The test material sample was mounted in the combustion chamber using a holder so that the axis of symmetry of the combustion chamber and the sample coincided. An electric current heated nichrome spiral was used to ignite the samples (AVIvanov, V.Ph. Alymov, ABSmirnov, ASMelikhov, IABolodyan, VIPotyakin et al. // Preliminary Results Of The Third Test Series Of Nonmetal Material Flammability Evaluation In “Skorost” Apparatus On The Space Station “Mir. // Proceedings of the Fifth International Microgravity Combustion Workshop, Cleveland, Ohio. May 1999). We studied such fire hazard indicators as: the lower limit of the combustion of materials by the flow rate in zero gravity (V _lim.s ); flame propagation speed through the material; material burnup rate, flame dimensions at different gas flow rates and oxygen concentrations. The experiments were carried out with materials with significantly different physicochemical properties: unplasticized organic glass, cotton cord, fiberglass SF-1-35G, materials melted during combustion - polyacetal, polyethylene, plasticized organic glass.

Investigations of the limiting conditions of combustion and extinguishing of materials in zero gravity made it possible to obtain unique data that currently determine the course of development of a new technology for ensuring the fire safety of inhabited pressurized spacecraft.

At the same time, it is impossible to determine the combustibility index of materials g _lim.c with the help of the presented ES “Speed”, since the design of this ES does not provide the possibility of conducting experiments at various accelerations of gravity.

The closest analogue, taken as a prototype in the development of this technical solution, is the device presented by the patent (patent of the Russian Federation No. 2284206. "Device for determining the combustibility of materials for living spaces of spacecraft and alien stations." IPC A62C 39/00. Priority of the invention of April 9, 2004. Application No. 2004110915 / 12. Authors: Melikhov AS, Ivanov AB, Ermak A. Published on September 27, 2006. Bull. No. 27). This device is designed to determine the combustibility of materials g _lim.c under the action of gravity. The possibility of determining the exponent g _lim.c using this device is ensured by the fact that the occurrence of naturally convective movement of the working gas medium under the influence of gravity is prevented in the flat combustion chamber of the device by reasonably limiting its height. With a decrease in the height of the flat combustion chamber, the Grashof number decreases and the heat and mass transfer process becomes equivalent to the conductive (molecular) one (Gershuni GZ, Zhukhovitsky EM Convective stability of an incompressible fluid. -M .: "Science". 1972. - 392 p.) .

A combustion chamber with a sample installed in it is placed in a centrifuge container with a plane of rotation perpendicular to the Earth's gravity vector. The height of the combustion chamber (h _k ) in the direction of the Earth’s gravity vector when determining the index g _lim.c in the atmosphere in which the material is supposed to be used, is established based on the ratio:

$$h_k=0.6\cdot {\left(C_{ox}\right)}^{-0.25}\cdot {\left(P\right)}^{-0.65},\left(\mathrm{four}\right)$$

where C _oh is the volume fraction of oxygen in the gas medium; P = P _en / P ₀ - dimensionless pressure of the medium;

P _en - pressure of the medium during the experiment, MPa; P ₀ - atmospheric pressure of the medium, MPa.

Relation (4) was found as a result of processing data obtained in experiments in a free-falling system and as a result of analysis of the combustion pattern of material samples in a flat combustion chamber with the determination of the conditions when the natural-convective movement of the working gas medium, induced by the Earth's gravity, ceases to deform the flame, formed by natural convective flows formed by the action of centrifugal acceleration.

The device operates in accordance with the following procedure. A sample of the test material was fixed in the combustion chamber. A nitrogen-oxygen medium was created in the container with the given C _oh and P. The centrifuge was turned on, the sample was ignited with an electric spiral. Further, combustion proceeded under the action of a natural convective flow of a gaseous medium that arose in the combustion zone under the action of centrifugal acceleration created by rotation of the centrifuge. In a series of experiments, the limiting value of the angular velocity for combustion of this material was determined, below which the combustion of the material sample did not occur - ω _lim . The value of g _{lim.c was} calculated as the sum of the vectors of centrifugal and Coriolis accelerations:

$${\overrightarrow{g}}_{\lim .c}={\overrightarrow{g}}_{cen}+{\overrightarrow{g}}_{kor}\left(5\right)$$

Centrifugal acceleration was determined by the formula:

$$g_{cen}={\omega }_{\lim .c.}^2\cdot R_c\left(6\right)$$

where ω _lim.c is the angular velocity of rotation of the centrifuge, at which the limiting mode of combustion of this material is observed with its subsequent extinction, 1 / s; R _c is the radius of rotation of the combustion zone of the sample, m

Coriolis acceleration was determined by the formula:

$$g_{kor}=2{\omega }_{\lim .c.}\cdot V_{\lim .c},\left(7\right)$$

where V _lim.c is the rate of combustion products in the flame zone at the combustion limit, taken equal to the value of the gas flow rate in zero gravity, which is the limit for the combustion of material (Bolodyan I.A., Ivanov A.V., Melikhov A.S. / Combustion of solid non-metallic materials in microgravity. // Materials of the 5th symposium of Asia-Oceania on the science and technology of fire, Newcastle, Australia. December 3-6, 2001. - P.195-204).

Note. In Russian publications, the term “weightlessness” is used (Cosmonautics. Encyclopedia. - M: “Soviet Encyclopedia.” 1985. - 527 p); in foreign publications - the term "microgravity".

Obviously, accurate knowledge of the fire hazard indicators of materials C _lim.g , g _lim.c and V _{lim.c is necessary} , since their values determine the conditions for preventing the possibility of self-developing burning of materials, as well as the possibility and time of extinguishing them during a fire in inhabited pressurized compartments, for example, by the methods of the above patents of the Russian Federation No. 2116092, No. 2284204, No. 2306965, No. 2319528.

The prototype device does not fully meet these requirements.

To create conditions in a flat combustion chamber of the prototype device, as close as possible to zero gravity, in which it is possible to conduct experiments with combustion at low accelerations of gravity, the height of the combustion chamber (h _k ) in the experiment should be limited to a value determined from relation (4).

Studies conducted with different materials showed that the prototype device according to the patent of the Russian Federation No. 2284206 with sufficient reliability allows you to determine the fire hazard indicators of materials, including the value g _lim.c , only for materials in which the flame is located near the surface of the sample material and has a vertical size smaller than the h ^ value determined from relation (4). This class includes fiberglass, fiberglass and other composite materials.

Figure 1 shows a comparison of the height of a flat combustion chamber 1 and the size of the high-temperature zone of flame 3 when burning a specimen 2 of VPS-7 V OST92-0956-74 fiberglass, under conditions when the combustion process proceeds to the limit, i.e., when gravity is accelerated, equal to g _lim.c. Under these conditions, the flame does not touch the walls of the combustion chamber and therefore the walls practically do not affect the determined value of g _lim.c. In this regard, for example, in composite materials, there is a good correspondence between the combustion limits obtained in a flat combustion chamber and in true long-term weightlessness. From figure 2 it can be seen that for fiberglass SF-1-35G GOST 10316-78, the value of V _lim.c , determined at C _oh = 21.5% in a flat combustion chamber with cross-sectional dimensions equal to 7 × 150 mm (point in dependences of 4 at C _oh = 21.5%), close to the value of V _lim.c obtained at the same C _oh on board the Mir CS in the Speed EA with a combustion chamber with a cross-sectional dimension of 80 × 150 mm (point 5) (AVIvanov, V.Ph. Alymov, ABSmirnov et al. / Study of Materials Combustion Processes in Microgravity. - Proceedings of the Joint Tenth European and Sixth Russian Symposium on Physical Sciences in Microgravity. / St. Petersburg, June 15-21, 1997. Moscow, 1997, vol. 1, pp. 401-408).

The bulk of CNMs burning without a solid residue, when burning in an oxygen-enriched atmosphere, has a cross-sectional size of the high-temperature zone of the flame, especially at the burning limit of the sample, when the rate of natural or forced gas flow that supports combustion is minimal, much higher than that of composite materials. Figure 3 shows the combustion of sample 6 of melting polyethylene under near-boundary conditions in the ES "Speed" on board the CS "Mir". The pyrolysis products of the material extend as far as possible from the surface of the formed material droplet 7 and the transverse flame size 8 can far exceed the value of h _k found by formula (4) to determine the value of g _lim.c in the prototype device. The high-temperature zone of the flame with a diameter of 16 mm does not touch the walls of the combustion chamber of the EU "Speed". Figure 4 shows the combustion of the sample 10 of the melting polyacetal in near-boundary conditions of a flat combustion chamber 9 included in the prototype device. It can be seen that the walls of the flat combustion chamber do not allow to realize all the natural dimensions of the flame 12, that is, they extinguish the outer part of the flame, the cross-sectional diameter of which in open space far exceeds the value of h _k found by formula (4). It can be seen from the diagram in FIG. 5 that when the sample 14 is burned in a flat combustion chamber 13 of height h _k found by formula (4), all the natural dimensions of the flame 15 are not realized, as this happens, for example, under conditions in the “Speed” EC. The dimensions of the flame in the flat combustion chamber 13 are limited. In the flat combustion chamber, only the central part of the flame (Fig. 4 and Fig. 5) can exist, from which a substantially lower heat flux is transmitted to the sample than the heat flux transmitted from the full-size flame. In this regard, in a flat combustion chamber can be obtained significantly overestimated values of the determined burning limit g _lim.c , compared with true.

This is the main disadvantage of the device for determining the burning limits of materials g _lim.c according to the patent of the Russian Federation No. 2284206, which can lead to incorrect development of measures to ensure fire safety of pressurized compartments and equipment used in them.

The disadvantage of the prototype device is that in a device with a flat combustion chamber, it is difficult or impossible to determine the ultimate combustion parameters for materials that melt during combustion. Studies have shown that when burning such materials, the diameter of the melt droplet increases quite quickly. Figure 4 shows that the drop 11 of the molten "polyacetal", reaching a diameter of 6.5 mm, begins to sag under the influence of the acceleration of gravity of the Earth. As the diameter of the droplet increases, after a while its surface touches the horizontal wall of the flat chamber. When the wall is touched, the droplet spreads over it and therefore the nature of the material combustion process changes dramatically. Under these conditions, the limit values for combustion of the material cannot be correctly determined due to increased heat loss from the combustion zone to the wall of the combustion chamber and due to violation of the conditions for the sample to flow around the gas stream. Such combustion conditions do not correspond to the conditions in the open space of the spacecraft pressurized compartment in space flight (in zero gravity).

In zero gravity (AVIvanov, V.Ph.Alymov, ABSmirnov, ASMelikhov, IABolodyan, VIPotyakin et al. // Preliminary Results Of The Third Test Series Of Nonmetal Material Flammability Evaluation In “Skorost” Apparatus On The Space Station “ Mir. ”// Proceedings of the Fifth International Microgravity Combustion Workshop, Cleveland, Ohio. May 1999) a drop of molten material behaves differently. In figure 3. it is seen that in zero gravity a growing drop of 7 polyethylene with a diameter of 18 mm and a diameter of 9 mm remains located at the end of sample 6, coaxially with it. In this case, the diameter of the flame 8 across reached in this case 16 mm and there was no distortion of its shape; during combustion of the sample, it remains symmetrical about the axis of the sample. In the experiments, there was no contact of the flame with the walls of the combustion chamber of the EU "Speed".

Thus, it can be stated that the value of the lower combustion limit by the acceleration of gravity g _lim.c can only be correctly determined in the inhabited pressurized spacecraft in an orbital flight on an EC with a combustion chamber having a minimum cross-sectional dimension, which excludes touching the chamber walls with a high-temperature flame zone combustion.

According to the data obtained in the ES "Speed" on board the CS "Mir", and the data of the work (Melikhov A.S., Potyakin V.I., Flankin E.V. Limit conditions of polymer combustion at low pressures // Combustion and Explosion Physics . 1982, No. 3. - P.44-47) the minimum size of the cross section of the combustion chamber when testing samples of materials with dimensions close to the characteristic dimensions of real structural elements for inhabited pressurized cells KL should be at least 80 mm.

The technical result of the invention is the development of a device for determining the combustibility indices of structural non-metallic materials necessary for the development of methods and means of ensuring fire safety of inhabited pressurized vessels KL and IS and equipment for them, both in terms of preventing fires and extinguishing them. Taking into account the analysis of the current state of the issue, the developed device is designed to determine the lower limit of combustion of materials to accelerate gravity, depending on the concentration of oxygen in the atmosphere of the spacecraft pressurized compartment under space flight conditions, in which the error in determining the combustibility indices at an unacceptable level is excluded.

The specified technical result is achieved by the fact that in the device for determining the combustibility indices of structural non-metallic materials in space flight for the conditions of inhabited airtight compartments of spacecraft and alien stations, containing a centrifuge with a combustion chamber of a sample of the test material placed in it, according to the invention, is adjacent to a combustion chamber, made in the form of a cylinder, an additional container with a working gas medium is placed, while the combustion chamber at both ends It is connected with an additional capacity with openings for the passage of the working gas medium during the formation of a closed loop of its movement, induced by natural convection that occurs when the gas medium is heated from a burning sample of the test material, under the action of centrifugal acceleration of gravity created in the experiment due to the rotation of the centrifuge, the combustion chamber and additional capacity equipped with plate heat exchangers, one of which is located in the combustion chamber between the axis of rotation of the centrifuge and the sample material, and the other in an additional container between the axis of rotation of the centrifuge and the outlet of the working gas medium from the combustion chamber, the opening from the side of the working gas medium into the combustion chamber is closed by a net of non-combustible material with low hydraulic resistance, the openings between the combustion chamber and the additional tank from each the end of the combustion chamber is made with areas in the lumen not less than the cross-sectional area of the combustion chamber in the area of the sample of the test material.

A device for determining in space flight the combustibility indices of KNM for the conditions of inhabited pressurized cells KLA and IS and its operability are illustrated by the following drawings.

Figure 1 shows the combustion of a specimen of fiberglass VPS-7V in near-boundary conditions in a flat combustion chamber of the prototype device: 1 - a flat combustion chamber; 2 - sample material; 3 - flame. The flame zone during combustion of the VPS-7V sample does not touch the walls of a flat combustion chamber. Figure 2 on the example of fiberglass SF-1-35G shows a comparison of the combustion limits for the parameters for weightlessness, defined when With _oh = 21.5%: 4 - in a flat combustion chamber; 5 - in the ES "Speed" on board the CS "Mir". Certain values of the combustion limits — the values of V _lim — are close. Figure 3 shows the combustion of a sample of melting material - polyethylene - in near-boundary conditions in the ES "Speed" on board the CS "Mir": 6 - sample of material; 7 - a drop of molten material; 8 - flame. The high-temperature zone of the flame does not touch the walls of the combustion chamber of the EU "Speed". Figure 4 shows the combustion at the limit of the sample of the melting material - polyacetal: 9 - a flat combustion chamber; 10 - sample material; 11 - a drop of molten material; 12 - flame. Figure 5 shows the interaction of the flame during combustion of the sample with the horizontal walls of the flat combustion chamber when the size of the high-temperature zone of the flame is greater than the working height of the flat combustion chamber h _k : 13 is a flat combustion chamber; 14 - sample material; 15 - flame at the limit of combustion in zero gravity outside a flat combustion chamber; 16 - flame at the limit of combustion in a flat combustion chamber. 6 and 7 show horizontal and vertical sections of a device for determining in space flight the combustibility indices of KNM for the conditions of inhabited pressurized vessels KL and IS: 17 - a rotating part of the centrifuge; 18 - bracket for mounting the centrifuge in the inhabited pressurized spacecraft for operation; 19 - a combustion chamber of a sample of the test material; 20 - additional capacity; 21 is a sample of the test material; 22 - part of the combustion chamber in which a sample of material is burned; 23 - plate heat exchanger in the combustion chamber; 24 - part of the combustion chamber for removal of the working gas medium from the heat exchanger 23 into an additional tank 20; 25 - a rod for introducing a sample into the combustion chamber; 26 - guide channel for the rod for specimen entry; 27 - plate heat exchanger in an additional tank; 28 - opening from the combustion chamber to an additional tank; 29 - an aperture from an additional tank to the combustion chamber; 30 - grid, stabilizing the gas flow entering the combustion chamber; 31 - electric ignition of the sample; 32 - the main electromagnetic drive for supplying electric coils to the working position; 33 - rod for supplying electric coils; 34 - backup electromagnetic drive for supplying a backup electric spiral to the working position; 35 - video camera for fixing the combustion process and the extinction of the sample; 36 - mirror; 37 is a webcam for showing and fixing the combustion process by the KLA computer; 38 - electric centrifuge with a speed controller; 39 - block sliding contacts; 40 - fitting for connecting the combustion chamber filling system and additional capacity with a gaseous medium with a given oxygen concentration.

Figure 8 shows plots of g _lim.c for C _ox: plexiglass CO-120 (line 41), polyvinyl chloride (PVC) (line 42), Micarta (line 43), using results of the prototype apparatus and the value of C _lim for these materials, determined at g = 981 cm / s ² (lines 44, 45, 46), the acceleration of gravity on the moon and on Mars (lines 47 and 48).

This invention is based on the results of the study by the authors of the limiting conditions of the combustion of materials in zero gravity and in the field of small accelerations of gravity, including in the conditions of orbital flight at the Mir spacecraft (On the limiting regimes of polymer combustion in the absence of free convection. / Melikhov A.S. , Potyakin V.I., Ryzhov AM, Ivanov B.A. // Physics of Combustion and Explosion. 1983, No. 4. - P.27-30; Bolodyan I.A., Ivanov A.V., Melikhov A.S. / Combustion of solid non-metallic materials under microgravity // Materials of the 5th Asia-Oceania Symposium on Science and Technology e fire, Newcastle, Australia. December 3-6, 2001. - P.195 - 204).

Studies have shown that the combustion of zero gravity materials (at g = 0) without a forced flow of a gas medium ceases. But there is a gas flow velocity limiting for combustion V _lim , above which combustion of the material at g = 0 becomes possible. This situation is due to the fact that, at g = 0, molecular diffusion does not provide an oxidizing agent for the course of combustion reactions. As the acceleration of gravity increases from zero due to the difference in the densities of the gaseous medium in the combustion zone, a naturally convective motion of the medium arises, which at a certain intensity becomes sufficient to support the combustion process - it creates a flow adequate to the forced flow with a velocity near the limit for burning (g _{lim .c} ). Thus, the prerequisites for the existence of the maximum acceleration for burning (g _lim.c ) were identified; which were confirmed by experimental studies (Bolodyan I.A., Ivanov A.V., Melikhov A.S. / Combustion of solid non-metallic materials under microgravity conditions // Materials of the 5th Asia-Oceania Symposium on Fire Science and Technology, Newcastle, Australia. December 3-6, 2001 .-- S.195-204).

Figures 6 and 7 show horizontal and vertical sections of a device for determining in space flight a combustibility index g _lim.c KHM and substances at different values of C _ooh . The device is a centrifuge 17, which includes a cylindrical combustion chamber 19 of the sample of the test material 21, conjugated coaxially with additional capacity 20. The combustion chamber 19 and additional capacity 20 are mounted on the bracket 18 for mounting the centrifuge in the inhabited pressurized spacecraft for operation. The combustion chamber 19 includes a part 22 in which a sample of the test material 21 is burned, and a part 24 for removing the heated gas medium with combustion products from the heat exchanger 23 to the additional tank 20. In the additional tank 20, a heat exchanger 27 is placed. The combustion chamber 19 is from two ends connected to an additional capacity of 20 openings 28 and 29 to enable the formation of a closed loop of the working gas medium, induced by natural convection that occurs when a sample of the test material is burned under Corollary centrifugal acceleration of gravity generated in the experiment due to rotation of the centrifuge. The aperture on the side of the working gas medium inlet into the combustion chamber is closed by a grid 30 with low hydraulic resistance from non-combustible material. The area of the openings between the combustion chamber and the additional capacity is performed in the light not less than the cross-sectional area of the portion 22 of the combustion chamber. An electric coil 31 is provided for ignition, which, with the help of an electromagnetic drive 32 and a rod 33, moves from its initial position to the end of the sample by a signal. For accurate installation of the sample in the working position and the exact supply of electric spirals to the end of the sample, the rod 25 is introduced along the guide channel 26. To increase the reliability of operation of the device, a backup electromagnetic drive 34 is provided. A video camera 35 with a mirror 36 is used to fix the combustion process and the extinction of the sample during rotation of the centrifuge To monitor the process of ignition, combustion and extinction of the sample and the corresponding operational manual control of the centrifuge, a webcam 37 is used, which is displayed on the screen of the on-board computer of the KLA and is fixed by it. The rotation of the centrifuge and the regulation of its rotation speed is provided by an electric drive 38 connected to the system and the rotation control panel of the unit “combustion chamber - additional capacity” of the centrifuge. All electrical circuits are fed to the centrifuge through the block of sliding contacts 39. To connect the block “combustion chamber - additional capacity” to the system of filling it with a gas medium with a given oxygen concentration, there is a fitting 40 with a closing hole. A pipe 40 is connected to the fitting 40 for evacuating the unit “combustion chamber - additional capacity”.

The determination of the value of g _lim at a given C _oh is performed according to the following procedure.

A sample of material was installed in the combustion chamber. The unit "combustion chamber - additional capacity" is evacuated. A nitrogen-oxygen medium with a given oxygen concentration at a given pressure is created from cylinders with nitrogen and oxygen using a mixing device in the unit.

Space experiments are an expensive undertaking. At the same time, conducting space experiments to study the combustion process in the conditions of an inhabited pressurized spacecraft in an orbital flight is also potentially fire hazard. The cost of experiments and fire risks during their implementation depend both on the design of the device and on the number of experiments that must be performed to complete the space program with a sufficiently high practical and scientific result.

Ensuring space experiments with low fire risk is achieved by fulfilling the requirements of fireproof technology for work in inhabited pressurized spacecraft, for example, according to the patent (patent of the Russian Federation No. 2116092 "Method for ensuring fire safety of inhabited pressurized spaceships." Priority of invention dated 05.12.1995, Authors: Melikhov A.S., Zaitsev S.N., Ivanov A.V., Published July 27, 1998, Bull. No. 21).

To ensure the lowest possible cost for the implementation of the space program with the use of the device presented, it is necessary to determine approximately the dependence of g _lim.c on C _{ooh of the} studied material on the prototype device. Such dependences for a number of materials are shown in Fig. 8. Then, using the control panel of the rotational speed control unit of the "combustion chamber - additional capacity" of the centrifuge, set the command to start the centrifuge, starting with a certain value of ω.

The initial value of ω for a given test material at a given value of C _oh can be found using a certain dependence of g _lim.c on C _oh for a given test material. For example, the expected value of g _lim.c for polyvinyl chloride at C _ox equal to 30% according to the relationship g _lim.c by C _ox, shown in Figure 8, is equal to 100 cm / s ^2. Given the estimated maximum error in determining this value using the prototype device, equal to at least 50%, the experience of determining g _lim.c on the device presented should be started by starting a centrifuge to create an initial g _{c of} 150 cm / s ² , which R _c = 260 mm corresponds to an angular speed of rotation of the centrifuge equal to 2.41 / s After bringing the centrifuge into rotation with the initial angular velocity, immediately turn on the actuator 32 to bring the electric coil 31 to the sample material. The ignition and combustion of the material sample should be controlled by the image on the screen of the on-board computer of the spacecraft transmitted by the webcam 37. If a stable combustion of the sample occurs, the angular speed of rotation of the centrifuge should immediately begin to decrease at a speed of 0.01 radian / s per second. At the time of extinction of the material sample, the value of the angular velocity of rotation of the centrifuge ω _lim.c should be fixed. This value of the angular velocity should be used in determining the value of g _lim.c at a given C _oh . To determine the value of g _lim.c , 3 parallel experiments should be performed for a given C _ox .

The value of g _lim.c found in each experiment should be determined by the formula (5).

Centrifugal acceleration should be determined by the formula (6).

Coriolis acceleration should be determined by the formula (7).

In the table, as an example, the values of the components calculated when determining the value of g _lim.c for polyvinyl chloride at C _oh equal to 30% are given.

ω _lim.c , 1 / s g _cen , cm / s ² V _lim , cm / s g _kor , cm / s ² g _lim.c , cm / s ² 2.11 115.7 12.0 50.6 126

Having determined the values of g _lim.c for different C _ooh, the dependence of the value of g _lim.c on C _oh is constructed for practical application while ensuring fire safety of the inhabited pressurized vessels KLA and IS.

Coriolis acceleration in experiments slightly changes the direction of the total vector of centrifugal and Coriolis accelerations equal to 126 cm / s ² , which is determined in the experiment. This cannot significantly affect the determined value of g _lim.c at a given C _oh , since combustion proceeds precisely at a total g of 126 cm / s ² .

The essence of the processes occurring in the present device when determining the combustibility of materials in space flight is illustrated by the following examples.

If a spacecraft with a manned pressurized compartment is given rotation in orbital flight (in zero gravity) to carry out this technological process by determining g _lim.c , then objects will be pressed by centrifugal force equal in magnitude to the centripetal force and inverse to it (Kitaygorodsky AI Introduction to Physics. § 5. Publishing House "Science". 1973). Moreover, the conditions, starting from g _n = 3 m / s ² , will be approximately similar to the earth ones (Artyukhin Yu.P. et al. / Control systems for spacecraft stabilized by rotation // Moscow: Nauka, 1979. - 100 s .). A person will be able to walk through the pressurized compartment, and materials having C _lim.g ≥C _ox.m will burn steadily in areas where the acceleration will exceed some values at which the effective gas flow velocities arising from natural convection in the flame zone, on average will exceed the lower combustion limits of materials in terms of flow rate in zero gravity (V _lim.c ), which are significantly different for each material - from 0.3 to 15 cm / s ² (Bolodyan I.A., Ivanov A.V., Melikhov A .S. / Combustion of solid non-metallic materials under microgravity // Materials 5th Symposium of Asia-Oceania on the Science and Technology of Fire, Newcastle, Australia. December 3-6, 2001. - S.195-204).

If the spacecraft rotational speed is gradually reduced, then with some acceleration of gravity in the combustion zone, the material sample will go out. With sufficiently accurate knowledge of the acceleration of gravity in the combustion zone, this acceleration value can be taken as the lower limit of combustion by the acceleration of gravity of a given material at a given oxygen concentration in the atmosphere. This acceleration value can be used to assess the fire hazard of materials in inhabited pressurized compartments of modules located on other planets that have a gravity acceleration different from the earth's one, and to determine the conditions for extinguishing materials and substances (patent of the Russian Federation No. 2306965 “Method of fire protection of inhabited pressurized compartments of space flying apparatuses. ”Priority of the invention dated 10.24.2005. Author: A. Melikhov Published on September 27, 2007, Bull. No. 27; patent of the Russian Federation No. 2319528“ Method for ensuring fire safety sealed compartments of residential modules of space bases on the Moon. ”Priority of the invention dated April 17, 2006. Authors: Kopylov NP, Bolodyan IA, Melikhov AS, Published March 20, 2008, Bull. No. 8).

A similar process takes place in the area of the sample of the test material in the combustion chamber of the device. Moreover, to reduce the error in determining the value of g _lim.c , the design of the device should ensure the existence of a given value of g at the location of the sample material and a closed circuit of the working gas medium in the device, eliminating local accumulation of combustion products of the sample material.

A closed loop of the movement of the working gas medium in the device is formed due to the following arrangement of the device.

In the combustion chamber and in the additional tank, plate heat exchangers are placed, which represent peculiar pumps in the centrifugal acceleration field. Their action is carried out due to different temperatures in the mass of the gaseous medium, which provides a different density of the medium. Due to centrifugal acceleration acting on this medium, it moves in the device.

Plate heat exchangers are made of cylindrical elements placed from each other at distances of 6-7 mm. This ensures laminar motion of the gaseous medium in the formed channels and excluding the movement of the cooling gas towards the heated gas (Gershuni GZ, Zhukhovitsky EM Convective stability of an incompressible fluid. - M .: Nauka. 1972. - 392 p.) .

Under conditions close to the combustion limits V _lim.c and g _lim.c , (g _lim.c is the value determined using the proposed device), the gas flow rates in the combustion zone (in the region around the flame) are small (I. Bolodyan , Ivanov AV, Melikhov AS / “Combustion of solid non-metallic materials under microgravity conditions” // Materials of the 5th Asia-Oceania Symposium on Fire Science and Technology, Newcastle, Australia, December 3-6, 2001. - S.195-204). They are 0.3-15 cm / s. The products of the pyrolysis of the material depart from the surface of the material with almost the same speeds. Therefore, the gas heated by the flame occupies the entire cross section of the combustion chamber directly near the burning center - a few centimeters from it. The result is obtained from solving the system of equations in the Prandtl approximation (L. Loitsyansky. Fluid and gas mechanics. - M.: “Science”. 1987. - 840 p.).

Heated gas fills the entire cross section of the combustion chamber in zone 22 to the heat exchanger and at the beginning of the heat exchanger, passing between the plates and giving them heat. Naturally, convective flow moves towards the axis of rotation.

The sequence and mechanism of gas-dynamic processes in the device occurring during the combustion of a sample of material in the combustion chamber of the device are as follows.

The experiments showed that if the combustion chamber with the heat exchanger is installed vertically in the acceleration field of the Earth's gravity, then after the combustion of the sample, a jet of a gas mixture of air and combustion products rises.

It should be noted that under the conditions of the presented device, the convection flow moving in the zone 24 to the axis of rotation due to the action of centrifugal acceleration will prevent the emission of the mixture from the heat exchanger 23 into the zone 24 of the combustion chamber it is not possible to completely cool the gas mixture of air and combustion products in the heat exchanger 23 (due to the presence of "under-recovery" in the heat exchange process in the heat exchanger).

To determine the possibility of gas transition from parts 22 and 23 of the combustion chamber and the emergence of a further closed loop of movement of the working gas medium in the device, the Grashof numbers in parts 23 and 24 separated by a plane passing along the axis of rotation during rotation of the combustion chamber should be determined. Thus, we can compare the relative efficiency of the lifting forces that cause the free-convective movement of gaseous media in both parts of the combustion chamber along its axis. The higher the Grashof number, the higher the speed of the gas flow induced by natural convection.

The Grashof number can be determined by the formula from the book (Yavorsky B.M., Detlaf A.A. Handbook of Physics. - M.: “Science”, 1964. - 847 p., P. 320):

$$Gr=g_{cen.\lim }\cdot \beta \cdot {\left(l_w\right)}^3\cdot \Delta T/{\mathrm{<figure-callout\; id="2"\; label="\nu \; g"\; filenames="00000011.png,00000018.png"\; state="\{\{state\}\}">\nu \; </figure-callout>}}_g^{}=g_{cen.\lim }\cdot {\left(l_w\right)}^3\cdot \Delta T_w\cdot {\nu }_{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="00000011.png,00000018.png"\; state="\{\{state\}\}">g</figure-callout>}}^2,\left(8\right)$$

where g _cen.lim - centrifugal acceleration in the combustion zone, close to the limit for combustion, established during the experiment, cm / s ² ; ΔТ = T _w -T ₀ - temperature difference (difference) in zones 22 and 23, K; T _w is the temperature of the medium after it is heated when a sample of the test material is ignited by an electric coil and sample combustion, K; T ₀ - ambient temperature, K; l _w is the characteristic size of the region of the heated gas medium, cm; ν _g is the kinematic viscosity of the medium at T _w , cm ² / s; β = 1 / T _w - temperature coefficient of volume expansion for gases, 1 / K. Centrifugal acceleration was determined by the formula (6).

The Grashof numbers in parts 33 and 44 of the combustion chamber were determined for the case of burning samples of polyvinyl chloride, which is widely used in inhabited pressurized spacecraft, having a _Clim value of 20% and a calorific value of 17 kJ / g. The Grashof numbers were determined for the regime of burning PVC samples in a gaseous medium corresponding to the atmosphere of inhabited pressurized compartments of PC MKC modules, i.e. in a nitrogen-oxygen atmosphere with an oxygen concentration (C _oh.m ) of 25% (User manual. Russian segment of the MKC. OJSC RSC Energia named after SP Korolev. URL: http://www.energia.ru/ com / iss / researches / iss_rs_guide.pdf).

The temperature of the gaseous medium in the working section of the combustion chamber, which was achieved after igniting the PVC sample with an electric coil and heating the medium with an electric spiral and during the combustion of the sample (value T _w ), was determined from the ratio for the heat balance for the combustion chamber:

$$W_{sp}+W_{fl}={\rho }_w\cdot V_{\lim .c}\cdot S_s\cdot c_p\cdot \Delta T\left(9\right)$$

where W _sp , W _fl - thermal power of the coil and of the burning sample; W; ρ _w is the density of the gaseous medium, g / cm ³ ; V _lim.c is the lower limit of the combustion of a material in terms of flow rate — the value of the gas flow rate during naturally convective or forced gas movement above which this material burns (both in the presence of gravity and in zero gravity), cm / s; S _s is the cross-sectional area of the working section of the combustion chamber, cm ² ; c _p is the heat capacity of the gaseous medium, J / (g K).

The value of T _{w was} determined by the formula:

$$T_w=\left\{\left(W_{sp}+W_{fl}\right)/{\rho }_w\cdot V_{\lim .c}\cdot S_s\cdot c_p\right\}+T_0\left(10\right)$$

by the method of successive approximations using the values of ρ _w , and c _p , which were taken equal to the values at the next obtained temperature T _w . The temperature Tw was taken as the temperature at which the relation for the heat balance was satisfied (9).

The values of ρ _w and c _p , as well as the μ value for estimating Gr values using the value ν _g = μ / ρ _w , are taken from the reference book (Vargaftik N.B. Reference book on the thermophysical properties of gases and liquids. "Science". M: M: 1972.- 721 p.).

The values of V _lim and g _cen.lim for estimating the values of Gr were determined according to the methods presented in (Bolodyan I.A., Ivanov A.V., Melikhov A.S. / “Combustion of solid non-metallic materials under microgravity conditions” // Materials 5th symposium of Asia-Oceania on the science and technology of fire. Newcastle, Australia. December 3-6, 2001. - P.195-204; patent of the Russian Federation No. 2284206 "Device for determining the combustibility of materials for living spaceships and alien stations. "Priority of the invention from 04/09/2004. Authors: Melikhov AS , Ivanov A.V., Ermak A.L. Published September 27, 2006, Bull. No. 27). At C _o.m.m equal to 25%, the obtained value of V _lim for polyvinyl chloride is 12 cm / s. The value of g _cen.lim for polyvinyl chloride is assumed to be 170 cm / s ² . The value of W _sp was taken equal to 20 W, and the value of W _{fl was} found to be 100 W. The diameter of the working section of the combustion chamber, where the material sample is located, is taken to be 80 mm.

Calculations by formulas (8) and (10) for part 22 of the combustion chamber during combustion of a PVC sample in it gave the following results: T _w = 599 K; Gr ₂₂ = 185268.

The calculation of the value of the number Gr for part 24 of the combustion chamber is made. The diameter of the part 24 of the combustion chamber is taken equal to 40 mm. Estimates showed that, for example, in a heat exchanger (8) 200 mm long, consisting of 1 mm thick copper plates located at a distance of 6 mm from each other, the working gas medium during cooling of the PVC sample can cool from 599 K to 313 K Then the value of the number Gr for the point in part 24 of the combustion chamber located symmetrically with the helix and the sample will be 3476. In this case, it is 53 times less than for the same point in part 22 of the combustion chamber where the sample material is located. Thus, the relative lift efficiency caused by the free convective motion of the medium in the parts 22 and 23 of the combustion chamber is significantly higher than in the part 24 of the combustion chamber. In this regard, a gas jet is formed at the outlet of the heat exchanger 23, the expiration of which creates a certain vacuum in the cavity 22 of the combustion chamber. Therefore, a gaseous medium enters here from an additional tank through an opening with grids 30. Since the combustion of a sample of material takes place continuously (until the sample dies out when g _{cen.lim is reached} ), the gaseous medium also moves continuously in a closed loop. The movement of the gaseous medium in a closed circuit is facilitated by the acceleration of motion in the heat exchanger 27 located in the additional tank due to incomplete cooling of the gaseous medium in the heat exchanger 23.

Thus, taking into account the calculation results, a closed loop of the movement of the working gas medium in the device is formed due to the implementation of the following processes. The gas medium after heating by ignition of the sample of the test material with a spiral and during combustion of the sample due to natural convective motion passes into the plate heat exchanger 23 and heats the plates as much as possible in the zone farthest from the axis of rotation of the centrifuge. In this regard, in the heat exchanger 23 there is a draft and movement of the working gas medium. Naturally convective flow moving in the zone 24 to the axis of rotation cannot prevent the ejection of the working gas medium from the heat exchanger 23, since the intensity of the working gas medium in the zone 24 is incomparably lower than the intensity of the gas medium when it is ejected from the heat exchanger 23. Considering that the velocity of the gas medium and the resistance to movement due to the large cross-sections of the containers in the device are small, the constantly existing vacuum in the cavity 22 of the combustion chamber ensures continuous existence A closed loop motion of the working gas environment in the apparatus. The incoming cold gas medium is heated in the working section 22 of the combustion chamber, and the process of moving the working gas medium continues. Since the processes proceed in zero gravity, the orientation of the device does not play any role in the movement of the gaseous medium; everything determines the presence of centrifugal acceleration in a zone with an inhomogeneous temperature field.

The use of possible techniques aimed at assessing the fire hazard of materials in the conditions of inhabited pressurized cabinets of spacecraft and IS and at developing measures to ensure the fire safety of inhabited pressurized compartments can be illustrated by the example of data obtained on analog devices. Figure 8 shows plots of g _lim.c C _ox for organic glass CO-120 (line 41), polyvinyl chloride (line 42), Micarta (line 43) and the value C _lim for these materials determined at g = 981 cm / with ² (lines 44, 45, 46), which are equal to 15, 5, 19, 20%, respectively.

According to the dependencies, it is possible to determine at what oxygen concentrations of the pressurized compartments these materials can burn in the modules placed on the Moon (g _pl = 162 cm / s ² ) and on Mars (g _pl = 376 cm / s ² ) (lines 47 and 48 in FIG. .8). From Fig. 8 it can be seen that for these materials, the limits of combustion in terms of oxygen concentration on the Moon are 17%, 25, 5%, 33%, and on Mars 16%, 22%, 24%, respectively. Thus, polyvinyl chloride and getinax combustible on Earth in an air environment on the Moon, on Mars, are non-combustible at an oxygen concentration of 21%.

The value for planets lighter than the Earth (g _pl <981 cm / s ² ) should be determined by the lower limit of combustion from the acceleration of gravity; and for planets heavier than the Earth (g _pl > 981 cm / s ² ) - according to the upper limit (Bolodyan I.A., Ivanov A.V., Melikhov A.S. / Combustion of solid non-metallic materials under microgravity // Materials 5- Symposium of Asia-Oceania on the Science and Technology of Fire, Newcastle, Australia. December 3-6, 2001. - P.195-204).

The main distinguishing feature in the claimed invention is the use in an centrifuge adjacent to the combustion chamber of an additional container with a working gas medium, while the combustion chamber is connected at two ends to the additional capacity of the openings with the formation of a closed loop of the gas medium, induced by natural convection arising from the combustion of the test sample material under the action of centrifugal acceleration of gravity created in the experiment due to the rotation of the centrifuge, the combustion chamber and additional The second tank is equipped with plate heat exchangers, one of which is located in the combustion chamber between the axis of rotation of the centrifuge and the sample of the test material, and the other in the additional tank between the axis of rotation of the centrifuge and the outlet of the working gas medium from the combustion chamber. The use of the invention allows to obtain reliable information on the combustibility of materials with minimal material costs in the conditions of inhabited pressurized compartments of spacecraft and alien stations. The data determined using the proposed technical solution allows us to reasonably develop measures to ensure the fire safety of inhabited pressurized compartments located on other planets and in space. Alternative devices for this are currently not available.

Patent of the Russian Federation No. 2284206 “A device for determining the combustibility of materials for the conditions of inhabited spaces of spacecraft and alien stations. IPC A62C 39/00. Priority of the invention of 04/09/2004, Application No. 2004110915/12. Authors: Melikhov A.S., Ivanov A.V., Ermak A.L., Published September 27, 2006, Bull. No. 27).

Claims (1)

A device for determining the combustibility indicators of structural non-metallic materials in space flight for the conditions of inhabited pressurized compartments of spacecraft and alien stations, containing a centrifuge with a combustion chamber of the sample of the test material, characterized in that it is adjacent to the combustion chamber of the sample, made in the form of a cylinder additional capacity with a working gas medium, while the combustion chamber is connected at both ends to the additional capacity with openings for passage Yes, the working gas medium during the formation of a closed loop of its movement, induced by natural convection that occurs when the gas medium is heated from a burning sample of the test material, under the action of centrifugal acceleration of gravity created in the experiment due to the rotation of the centrifuge, the combustion chamber and additional capacity are equipped with plate heat exchangers, one of which is located in the combustion chamber between the axis of rotation of the centrifuge and the sample of the test material, and the other in the additional tank between the As the centrifuge rotates and the working gas medium exits from the combustion chamber, the opening on the side of the working gas medium inlet to the combustion chamber is closed by a net of non-combustible material with low hydraulic resistance, the openings between the combustion chamber and additional capacity from each end of the combustion chamber are not exposed to light smaller than the cross-sectional area of the combustion chamber in the area of the sample of the test material.

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