Исследования льдообразующих свойств пиротехнического состава АД-1

Currently, much attention is paid to the development of methods and tools for managing cloud processes. Carrying out work on active effects requires solving a number of methodological issues, in particular, how, where, when and with what reagents active effects should be carried out in order to achieve optimal success.

When developing methods for managing cloud processes, a special place belongs to laboratory modeling of the key moments of active impacts. One of such key moments of active influences on cloud processes is the processes of ice crystal growth on reagent particles.

Modern concepts of active influences are based on changing the microphysical structure of clouds through reagents with specified physicochemical properties

The issue under study is in the field of cloud microphysics and precipitation. Since the first half of the 20th century, scientific work has been carried out in Russia and abroad to find effective reagents to combat hail, drought and to artificially cause precipitation. In these works, the effectiveness of reagents was investigated, weather modification tools were developed

At the same time, the characteristics of its surface play an important role in the efficiency of water crystallization on a reagent particle

The aim of the work is to study the processes of ice formation on particles of the AD-1 pyrotechnic composition.

Achieving this goal required solving the following tasks:

1. Development of a complex of equipment for obtaining particles of AD-1 pyrotechnic composition in a cloud environment.

2. Development of a methodology for studying the ice-forming properties of the AD-1 pyrotechnic composition.

3. Investigation of ice crystals formed on particles of the AD-1 pyrotechnic composition using a mathematical apparatus.

The main research methods are laboratory modeling of the processes of interaction of the cloud environment with reagent particles, as well as methods of mathematical statistics for analyzing the results obtained. During the research, the equipment and methodology for the study of ice formation processes were developed for the first time, ice crystals formed on particles of the pyrotechnic composition AD-1 were studied for the first time.

The scheme of the equipment complex is shown in Figure 1. The equipment complex includes: a large cloud chamber, a reagent sublimation device, an ultrasonic steam generator, scales, an optical microscope and a computer (Figure 1).

Figure 1 - A set of equipment for studying the ice-forming properties of AD-1 pyrocomposition

DOI:10.23670/IRJ.2023.137.135.1

The large cloud chamber is a refrigerated cabinet with a working volume of 6.16 m3. Inside the chamber there are fans for mixing water vapor and reagents. The inside of the chamber is lined with a metal sheet of galvanized iron and is cooled by a refrigeration unit. An electronic thermometer and a fan for mixing water vapor and reagent are placed inside the chamber. The chamber is equipped with a temperature control system with a screen on which the thermometer readings are displayed. The temperature in the chamber can be maintained from 0° to -20 °C. On the front wall there is an observation window and an opening for changing substrates with crystals.

The ultrasonic steam generator is placed inside a plastic container with a volume of 100 liters. The container is connected to a large chamber by a rubber pipe, a fan is installed on the lid of the container to create a steam flow into the chamber.

The device for sublimation of the reagent is a graphite substrate sandwiched between electrodes. An electric current of about 180-200 A is supplied to the electrodes, the substrate is heated to temperatures of the order of 1000 ºC and the reagent sublimes.

Thermostatic substrates for collecting crystals are small metal discs with diameter d = 4 cm, covered with clean glasses. The glasses are covered with lids that were opened at the moment of the appearance of crystals. Crystals settling at the bottom of the cloud chamber fall on the glass. Ice crystals are counted using an automated system.

Substrates are studied using an automated system, which consists of an optical microscope, a personal computer and specialized software. The calculation of the sizes and areas of ice crystals in different temperature ranges is carried out. 

A series of experiments were carried out to study the ice-forming properties of particles of the AD-1 pyrotechnic composition. The experiments were carried out in the temperature range from -3 to -14 °C.

Table 1 and Figure 2 present data on the area of ice crystals that formed on particles of the AD-1 pyrotechnic composition in different temperature ranges. The ratios of crystals for different size ranges, ncr/n, % are given.

Figure 2 - The area of ice crystals that formed on particles of the AD-1 pyrotechnic composition in different temperature ranges

DOI:10.23670/IRJ.2023.137.135.3

Table 2 and Figure 3 present data on the accumulated frequency ratios of crystals that formed on particles of the AD-1 pyrotechnic composition in different temperature ranges, ncr/n, %.

Figure 3 - Cumulative frequencies of crystal ratios formed on particles of AD-1 pyrotechnic composition

DOI:10.23670/IRJ.2023.137.135.5

As can be seen from the above data, up to 90% of ice crystals formed on particles of the AD-1 pyrocomposition have a surface area of up to 104 μm2 at temperatures from -9 to -14°C. At temperatures of the order of -3...-5 °C, the proportion of ice crystals with a surface area of up to 8·103 μm2 reaches 95%. At temperatures of the order of -6...-8 °C, the smallest crystals are formed, having a surface area not exceeding 4·103 μm2.

When sublimating the AD-1 pyrotechnic composition, particles are formed with a diameter from 20 nm to 400 nm with a modal value of 70 nm. In this case, almost 100% activity of silver iodide is observed in the presence of particles with a diameter of 50 nm

Table 3 and Figure 4 the total area of crystals that formed on particles of the AD-1 pyrotechnic composition in different temperature ranges.

Figure 4 - Distribution of the total area of crystals formed on particles of the AD-1 pyrotechnic composition by temperature

DOI:10.23670/IRJ.2023.137.135.7

Previously, the authors conducted studies of the ice-forming properties of the pyrotechnic composition of AD-1, as a result of which the influence of the thermodynamic and electrical characteristics of the cloud on the ice-forming efficiency of the reagent was studied

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. The study of ice crystals formed on the particles of the pyrolysis of AD-1 is being carried out for the first time. There are no studies of these characteristics of the ice-forming reagent in the scientific articles of Russian and foreign authors.

In the course of laboratory experiments, a method for studying the ice-forming properties of the AD-1 pyrotechnic composition has been developed.

When the AD-1 pyrotechnic composition is sublimated, particles with a diameter from 20 nm to 400 nm with a modal value of 70 nm are formed. Almost 100% activity of silver iodide is observed in the presence of particles with a diameter of 50 nm.

Up to 90% of the ice crystals formed on the particles of the AD-1 pyrocomposition have a surface area of up to 104 μm2 at temperatures from -9 to -14°C. At temperatures of the order of -3...-5°C, the proportion of ice crystals with a surface area of up to 8·103 μm2 reaches 95%. At temperatures of the order of -6...-8°C, the smallest crystals are formed, having a surface area not exceeding 4·103 μm2.

Most methods of hail prevention, artificial precipitation increase and fog dispersion are based on the following physical concepts:

- complete crystallization of the supercooled part of the cloud;

- competition theory;

- enlargement of droplets with their subsequent freezing;

- dynamic impact in order to suppress the upward flow;

- lowering the trajectory of hailstones;

- acceleration of sedimentation in the formation zone of hail generation conditions.

The impact of particles of the AD-1 pyrotechnic composition on the supercooled cloud environment leads to the formation of ice crystals having dimensions sufficient for the combined implementation of the above concepts. Therefore, the use of this reagent in weather modification is effective and widespread.