CC BY
1
УДК 551.576
Gekkieva S.
Department of cloud physics Federal State Budgetary Institution «High-Mountain Geophysical Institute
Nalchik, Russian Federation
INCREASING THE EFFICIENCY OF CRYSTALLIZING REAGENTS WITH THE HELP OF ADDITIONAL COMPONENTS
Abstract
This article presents theoretical studies and some results of laboratory experiments on the possibility of further increasing the efficiency of pyrotechnic compositions used in anti-hail products of the Alazan-6 and Alazan-9 types. The experimental material was the pyrotechnic composition AD1 with the addition of finely dispersed zinc powder, which was introduced into the original pyrotechnic composition in a ratio to its total mass of 3%, 6% and 9%, respectively. According to the results obtained, it follows that the presence of finely dispersed zinc powder in the composition of the original ice-forming fuel in a ratio to the total mass of the composition of 6% increases the yield of ice-forming particles in the entire range of accepted temperatures, from zero to minus 14 0C. Further discussions on the properties of crystallizing reagents and their improvement are conducted using AgI as an example, due to the fact that experimental data on the activity of AgI approximately correspond to theoretical data for characteristic particle sizes and reagent exposure times in clouds - natural and in fog chambers.
Keywords:
active effects, pyrotechnic composition, reagent, ice-forming particles, zinc.
Introduction
Attempts to influence the weather were made in ancient times. People, trying to disperse a thundercloud, launched spears and arrows at it, started forest fires, etc. With the development of scientific knowledge, they began to give a scientific explanation for the observed natural phenomena. At the end of the 19th century, experiments began to be conducted to cause rain and disperse clouds. Since the beginning of the 20th century, such experiments have become widespread and have begun to be carried out in many countries of the world. Although these experiments in active influences did not give positive results, they were still useful, since they forced people to discard old and seek new methods of artificially changing the weather and thus gradually find the right paths in this area of human activity. It can be said that achievements in the field of active influence on clouds are largely based on the experience of previous works [1-3].
Influencing atmospheric processes is also a method of understanding the laws of nature. The response of the atmosphere to the impact in strictly controlled experiments, accompanied by theoretical analysis, which allows us to determine how correct our ideas are about the physical processes occurring in the atmosphere, and whether their precalculations are possible; at the same time, it allows us to evaluate the reliability of the information and measuring equipment that monitors the state of the atmosphere and its transformation under the influence of the impact. In addition, we must not forget about the existence of military aspects of the science of impact on atmospheric processes.
Of great practical importance are the ongoing work aimed at causing artificial precipitation, preventing hail, dispersing fog and clouds. A number of substances are known, the introduction of which in a dispersed state into a cloud begins intensive crystallization of the cloud. The most popular among them is silver iodide aerosol obtained by thermal sublimation, which has high ice-forming activity. Pyrotechnic compositions based on silver iodide AgI include ammonium perchlorate, phenol-formaldehyde resin, dicyandiamide, a mixture of finely ground powders of silver, potassium and copper iodide, and graphite and industrial oil as technological additives,
as well as carbon black in the following ratio of components, mass %:
Ammonium perchlorate
phenol-formaldehyde resin
dicyandiamide
silver iodide
potassium iodide
copper iodide
graphite
carbon black
oil industrial
48-52 12-16
4-6 0.5-1 3-4 0.5-1
7-9 6-8
10-12
moreover, iodides of silver, potassium and copper are contained in a mass ratio of 1:1.6:0.7.
The disadvantages of this composition include a low threshold of ice-forming action in the range of minus 4-5 ° C, the yield of active crystallization nuclei at a temperature of minus 10 ° C is only (1-2) x 1013 s 1 g of the composition, and at minus 6 ° C - up to 7.5 x 1012 s 1 g of the composition, which is insufficient for effective practical use in influencing powerful hail processes. In addition, in the known composition, the ratios of the components of all the elements included in it are not sufficiently optimized, which reduces the effectiveness of its use. Despite this, this domestic pyrotechnic composition is used to create fuel charges of cruise rocket engines filled with a reagent to equip anti-hail missiles.
The search for new crystallizing reagents is associated with the need to maximize their activity, especially at temperatures close to 0 °C, to find cheap and environmentally friendly reagents. As follows from the developed theory, one of the main conditions for high reagent activity is the requirement for a minimum of the work of ice nucleation on the substrate, which corresponds to the requirement for a minimum of additional linear energy at the substrate-water interface. The values of the linear energy at the substrate-water interface for substrates with the same chemical composition may differ due to differences in surface properties.
Another important condition is high dispersibility of the reagent, which allows obtaining the optimal total surface of aerosol particles of the reagent. In addition, they must be hygroscopic - easily enveloped in water. Reagents such as silver iodide are hygroscopic due to impurities. This is why the crystallizing activity of Agl strongly depends on the composition and amount of hygroscopic impurities. The formation of droplets on hygroscopic nuclei has been well studied experimentally and theoretically. The growth of a drop of a hygroscopic substance solution due to the Raoult effect can occur at fairly low values of relative humidity (f), lower than the saturation humidity over pure water, for example, for a NaCl solution f > 75%. When water vapor is adsorbed on the surface of wetted particles, a thin film of water is formed, and the particles become a nucleating drop. Such a droplet particle can grow under conditions of relatively low supersaturation, since already at r > 0.5 ^m the value of saturation humidity over a convex surface (E(r)) is almost the same as saturation humidity over a flat surface (A'(A)). Particles with surface defects are covered with a film of water on concave areas, in which moisture condenses at relative humidities less than 100% [5].
The temperature threshold of ice-forming activity (crystallization threshold) is used as activity characteristics - the maximum temperature at which the crystallization process occurs at a noticeable rate, and the ice-forming activity itself - the number of ice particles formed in a supercooled cloud during dispersion of a unit mass of a reagent at a given temperature over a characteristic time. Activity and activity threshold depend on the physicochemical properties of the reagent, how well it disperses, the temperature and humidity of the cloud, and the method of introducing the reagent into the cloud.
Taking into account the above, the technical task is to increase the yield of ice-forming particles per gram of the composition in the temperature range from zero and below. Improvement of ice-forming reagents is carried out in various directions. Substances with a crystal structure that is as similar as possible to ice are synthesized based on the fact that in the most active of the known reagents - silver iodide - silver and iodide ions
are located similarly to oxygen and hydrogen in the ice lattice. Due to the fact that the inner layers of the reagent particles do not participate in ice formation, cheaper substances are used as a core, and silver iodide as a coating [5].
Some Experimental Results
Significant enhancement of the activity of some reagents can be achieved by adding new components to the basic composition. Zinc oxide is proposed as such a component. Zinc oxide, due to its hygroscopicity, some chemical and physical properties, allows to increase the ice-forming efficiency of the experimental reagent. The technical result is also achieved by the fact that the particle sizes of finely ground zinc powder in the pyrotechnic composition are 0.01 - 0.05 mm. The choice of this range of particle sizes is due to the fact that small particles are more intensively mixed with other components of the composition when forming fuel charges of anti-hail rockets. The results obtained through laboratory experiments [6] showed that the proposed pyrotechnic composition allows to significantly increase the yield of ice-forming particles from one gram of fuel by almost an order of magnitude in comparison with the prototype. Figure 1 shows the dependence of the yield of ice-forming active particles (n) for different contents of finely dispersed zinc powder in the original AD-1 composition. Curve 1 characterizes the yield of ice-forming particles from one gram of the initial composition AD-1 without zinc content, curve 2 - with 3% zinc content, curve 3 with 6% zinc content, and curve 4 with 9% zinc content.
tl.XlO15 r1
Figure 1 - Yield of active particles (n) for different contents of fine zinc powder in the initial composition of AD-1 n.xlO1- r1
0 1 2 J 1 1.7 5 5.5 6 6.6 7 8 9
Figure 2 - Dependence of the specific yield of ice-forming particles on the zinc concentration in the AD-1
pyrolytic composition for different temperature levels
It is evident from the presented graph that the maximum yield of ice-forming particles is provided in the
range of zinc concentrations of 4.7-6.6 wt.%. This area in Figure 2 is limited by vertical lines. It follows from the above materials that the presence of finely dispersed zinc powder in the composition of the initial ice-forming fuel in a ratio to the total mass of the composition of 6%, sharply increases the yield of ice-forming particles in the entire range of accepted temperatures, starting from zero to minus 14 0C. Such an increase in the yield of active ice-forming particles in the range of studied temperatures is explained by the fact that at a high combustion temperature of the pyrotechnic composition, zinc oxide nanotubes of various modifications and sizes are formed, which actively interact with the supercooled cloud environment in the accepted temperature range. For example, at a temperature of minus 120C (curve 3 on the graph), the output of ice-forming particles increases by almost an order of magnitude, and in the temperature range from minus 20C to minus 40C, it increases almost twofold, which makes it possible to influence the warmer supercooled part of the cloud environment.
Conclusion
The introduction of finely ground zinc powder into the known pyrotechnic composition in the accepted ratios to the total mass of the composition has virtually no effect on the technology of producing fuel charges, nor on the complex of its rheological and physical-mechanical properties, which makes it possible to manufacture unitary charges of any configuration for anti-hail missiles of the Alazan type, as well as missiles of other modifications, by free casting or casting under low pressure. This composition can also be used in the creation of promising ground generators for active impacts on supercooled fogs in order to ensure favorable meteorological conditions for the operation of spaceports, airports and road and transport communications. References
1. Nikandrov V. Ya. Artificial effects on clouds and fogs // L.: Gidrometeoizdat.1959.P.191.
2. Plaude N.O. On the mechanism of crystallization of supercooled fog by silver iodide aerosol // Proceedings of the Main Geophysical Observatory. Issue 186.1966. P.10-17.
3. Kachurin L.G. Physical principles of influence on atmospheric processes. L.: Gidrometeoizdat.1990. P.99-106.
4. Ivlev L.S., Dovgalyuk Yu.A. Physics of atmospheric aerosol systems. - St. Petersburg: Research Institute of Chemical Sciences of St. Petersburg State University. 1999. P.194.
5. Koloskov B.P., Korneev V.P., Shchukin G.G. Methods and means of modifying clouds, precipitation and fogs // Monograph. SPb.: RSHU. 2012. Pp.36-38.
6. Khuchunaev B. M., Baysiev H.-M. H., Gekkieva S. O., Budaev A. H. Experimental studies of the ice-forming efficiency of the pyrotechnic composition AD-1 with zinc additives. Collection "Proceedings of the Main Geophysical Observatory". Issue. 597. 2020. P. 51-60.
© Gekkieva S., 2024
УДК 551.582
Бадахова Г.Х., Кравченко Н.А.
Северо-Кавказский федеральный университет
г. Ставрополь
ГОДОВЫЕ СУММЫ ОСАДКОВ В СТАВРОПОЛЬСКОМ КРАЕ ЗА ПОСЛЕДНИЕ 10 ЛЕТ
Аннотация
Анализируется годовое количество осадков за последнее 10-летие в абсолютном выражении и в сравнении с климатической нормой. Показано, что имеет место незначительное увеличение годовых
