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Vol 14, No 3 (2021)
Development of chain models of the dynamics of the COVID-19 pandemic spread
Abstract
The work confirms the correctness of the mathematical model of the spread of the coronavirus pandemic as a branched chain (autocatalytic) reaction. The results of the interpretation of statistical data within the framework of this model for the already completed — the first and second — and the ongoing (in May–June 2021) third waves of coronavirus for the city (Moscow), region (Yakutia), and country (Russia) are presented. The quantitative parameters of the logistic function were obtained which satisfactorily describe the spread of the pandemic in these three research objects. The model has predictive capabilities. It was shown that the constancy of the infection rate after a decrease in this value means the beginning of the next wave of coronavirus. The start date and the number of people infected in it can also be determined in advance. So, for the third wave of coronavirus which takes place in June 2021, using the model, the number of people who will be infected in the third wave of coronavirus and the time of its beginning were determined. Some of the patterns found are universal. In particular, the effective rate constant decreases with the transition from the first wave to the second. This can be explained by the growth of the so-called herd immunity. The model calculates a dynamic constant associated with the probability of infection for one person. This constant can change by more than two orders of magnitude when moving from one region to another.
3-10
Formation of NO during the low-temperature combustion of H2O/CH4/Air mixtures containing H2O2 or O3
Abstract
The effect of H2O2 and O3 on the ignition delay of the stoichiometric H2O/Air/CH4 mixture and on the formation of NO is studied. It is determined that the replacement of H2O2 by O3 in the H2O /Air/ CH4 mixture does not affect the NO yield. At the same time, according to the results of calculations, the yield of NO decreases at lower temperatures of the initial mixture (T0). Thus, the value T0 = 650 K can be achieved in the case of using the mixtures containing 0.01 mf of O3. In this case, the NO concentration calculated at the combustion chamber outlet reaches values of 6–7 ppm. The results also assume that there is a possibility of further reduction in temperature of initial mixture and concentration of NO at the exit of the burner.
11-16
Thermochemistry of reactions of C6H5CH2C6H4O• and C6H5CH•C6H4 with O2 as well as of reactions of their unimolecular decomposition
Abstract
The thermochemical properties of the products of the reactions of C6H5CH2C6H4O• and C6H5CH•C6H4 radicals with molecular oxygen as well as the products of their monomolecular decomposition are determined using the modern molecular modeling approaches. Based on the calculated values, the thermochemistry of the considered reactions as well as the values of their activation barriers are reported.
17-26
Study of the infrared gas heaters characteristics under forced surface combustion modes
Abstract
Experimental studies of the combustion process of natural gas and air mixtures have been carried out on laboratory models of a gas infrared heater (GIH) operating in forced surface combustion (FSC) modes. The combustion process took place near the surface of the plates made of heat-resistant metal alloy (Ni 25%, Al 6%, Fe base). The design of the GIH models and the FSC mode allowed the authors to implement the stable surface combustion modes in the range of values of the firing rate from 2.15 to 7.55 MW/m2 per unit cross-sectional area of the gas flow. The experiments were carried out on two models. Dimensions of the system of radiating plates of the first model are: width 78 mm; length 92 mm; and height from 110 to 250 mm. Dimensions of the radiating surface of the second model are: width 78 mm; length 92 mm; and height 403 mm. Combustion power in the models of the GIH varied in the range from 12 to 42.2 kW. The concentration of nitrogen oxides in the combustion products was less than 16 ppm and the concentration of carbon monoxide was less than 10 ppm at the values of the air-to-fuel equivalence ratio 1.5. The maximum temperature of the outer surface of the radiating plates was 1280 ◦C. The coefficient of conversion of combustion energy into radiation energy for the model of the GIH with a height of 403 mm reached the values exceeding 40%.
27-34
Effect of the design of gas supply system on the performance of cylindrical radiant burners
Abstract
Radiant burners of cylindrical shape are of high interest for the engineering of advanced water heating boilers. The two main components of the radiant burner are the gas permeable emitting cylinder and the supply system for the fresh mixture. This study examined a cylindrical burner with a thin layered porous emitter made of porous intermetallic material with two types of gas supply systems: (i) stream injection through the gas supply duct; and (ii) distributed supply through the porous insert. The temperature characteristics, NOx emission, and noise are experimentally studied in the power range of 4.0–9.1 kW and the air-to-fuel equivalence ratio range of 1.0–1.7. It has been established that the distributed supply through the porous insert allows one to reduce NOx emission and noise as well as to increase the uniformity of temperature distribution along the surface of the porous emitter.
35-42
Measurement of flow rate characteristics of flow-through gas generator at gasification of low-melting solid material by ambient temperature airflow
Abstract
A semiempirical method is proposed for determining the flow characteristics of a flow-through gas generator operating on gasification of a solid low-melting material by an ambient temperature airflow. Experimental studies of the gasification of a polypropylene charge are performed to demonstrate the approach. In the test fires, the yield of gasification products ranged from 43 to 120 g/s and the ratio of mass flow rates of air and polypropylene gasification products was 2.3–2.9. The analysis of errors inherent in the approach is carried out.
43-60
Measurement of flow rate characteristics during low-melting material gasification in a flow-through gas generator
Abstract
A technique is proposed for determining flow characteristics of a flow-through gas generator (GG) with the allocation of the flow rate created by gasification of a low-melting solid material in the total flow rate of gases leaving the GG. Experiments on the gasification of polypropylene samples in a flow-through GG with an approaching supersonic air flow heated in a fire heater were performed. The measured time-averaged mass flow rate of gasification products was 0.080 kg/s at the freestream Mach number M = 2.43, 0.100 kg/s at M = 2.94, and 0.050–0.020 kg/s at M = 3.81. The ratio of the total mass flow rate of the incoming air to the total output of polypropylene gasification products was 1.61–2.86.
61-73
Gasification of organic waste with ultrasuperheated steam and carbon dioxide
Abstract
A literature review on allothermal gasification of organic waste in steam and carbon dioxide environment at atmospheric pressure is presented. Two groups of technologies are considered, namely, low-temperature (500–1000 ◦C) and high-temperature (above 1200 ◦C). The existing low-temperature gasification technologies are shown to provide the syngas of relatively low quality, exhibit low efficiency and complex control of gas composition, and low yields of syngas. The main efforts to improve such technologies are directed at preprocessing of feedstocks and additional processing of the product syngas as well as increasing the reactivity of the feedstocks with the help of catalysts. Unlike low-temperature gasification, high-temperature plasma gasification provides high quality syngas, exhibits high process efficiency and easy control of gas composition, and high yields of syngas. However, arc and microwave plasma technologies require huge energy consumption as well as special construction materials and refractory lining for gasifier walls. Moreover, gasification of feedstocks in plasma reactors mainly occurs at temperatures of 1200–2000 ◦C, so that the gas–plasma transition turns out to be an unclaimed but highly energy-intense intermediate stage. An environmentally friendly detonation gun technology for organic waste gasification is proposed and demonstrated as a more effective alternative.
74-97
Clarification of the parameters of the installation for determining the explosion characteristics of dust–air mixtures
Abstract
At the V. V. Voevodsky Institute of Chemical Kinetics and Combustion of the Siberian Branch of the Russian Academy of Sciences, an installation has been designed for determining the characteristics of the explosion of dust–air mixtures in accordance with the regulatory document GOST 12.1.044-89 (p. 4.11). The installation makes it possible to determine the lower concentration limit of flame propagation, the minimum phlegmatizing concentration of the phlegmatizer, the minimum explosive oxygen content, as well as the maximum explosion pressure of dust–air mixtures. The need to determine such characteristics is caused by safety requirements when performing production processes associated with the formation of combustible dust and gas mixtures. The purpose of this work is to justify the choice of the design parameters of the ignition source, the time of the beginning of spraying, and the time of switching off the heating spiral which are the main parameters for the correct determination of the explosion indicators of dust–air mixtures. To achieve this goal, experimental studies of the material and design parameters of the heating spiral were carried out and their optimal values were selected. A theoretical description was given that satisfactorily describes the experimentally measured dynamics of the heating and cooling processes of the heating spiral. The moment of opening of the air supply valve, which determines the start time of spraying and the time of switching off the heating spiral, was justified.
98-108
Thermal structure of the gunpowder burning wave at elevated pressures
Abstract
The thermal structure of the combustion wave in a double-base propellant is studied at elevated pressures up to 1000 atm using a thermocouple technique (3-micron thick tungsten-rhenium thermocouples). The experiments are carried out in a two-chamber installation which is a main reactive combustion chamber with a volume of 330 cm3 equipped with a replaceable conical nozzle and communicating with it additional chamber of a smaller volume of 45 cm3 in which the sample under study with embedded thermocouples is placed. The operating pressure in the installation is achieved by burning a powder cartridge in the main chamber and the pressure level varies fromexperiment to experiment by using a set of nozzles with different cross sections. The paper analyzes and substantiates the applicability of the thermocouple technique and the temperature profiles when a combustion wave passes through the sample at constant pressures of 310, 480, 605, 730, and 930 atm are obtained. Corrections of the temperature profile in the gas phase aremade taking into account the amendments associated, firstly, with a decrease in temperature in the readings of the thermocouple due to its radiation into the environment and, secondly, with a decrease in readings due to the inertia of the thermocouple in the case of its heat exchange with a medium having high values of the temperature gradient. It is shown that at some points of the profile, the corrections can reach 500 ◦C in total. The thermal effects and characteristic sizes of the reaction zones in the condensed and gaseous phases are determined. The burning rates are measured and the heat effects and characteristic sizes of the reaction zones in the condensed and gas phases are calculated.
109-121
Initiation of explosion by high voltage discharge of pressed mixtures of sevilene with ammonium perchlorate and nitrate with addition of powdered aluminum
Abstract
The use of a high-voltage discharge to initiate an explosion is justified when strict synchronization of actions is required. A typical working process, which is excited by a discharge, is detonation where high-power blasting explosives with the addition of nanodispersed metals are used to reduce the discharge voltage and increase the initiation stability. However, there are technical areas (here, one can mention the use in elements of dynamic protection of tanks and in promising hypersonic accelerators of the “blast wave accelerator” type) where nanodispersed metals are unacceptable due to their low stability and high cost and instead of normal detonation, softer explosive processes are required to exclude unnecessary blasting effect on the elements of the devices. In this work, the initiation of an explosion by a high-voltage discharge in pressed mixtures of ammonium perchlorate and ammonium nitrate with sevilene with additives of various metals has been investigated. Sevilen is a thermoplastic adhesive, a copolymer of ethylene and vinyl acetate, has excellent adhesion to all components of the studied mixtures, and provides excellent conditions for pressing samples. The best result: reliable explosions in a wide range of sample porosities up to a sample with a porosity of 1% at a threshold voltage of 5.5 to 1.5 kV were obtained using mixtures of ammonium perchlorate with the addition of 20% aluminum powder with a particle size of 10 m. The replacement of ammonium perchlorate with ammonium nitrate also demonstrates good results and with the addition of other metals (copper, iron, and zinc were studied), explosions were practically absent up to the maximum voltage of 12 kV used in the present work. The most probable reason: vigorous exothermic interaction of the aluminum melt formed during electrical breakdown with ammonium perchlorate. One can try to use this effect to replace nanodispersed aluminum with a powder with micron-sized particles during high-voltage initiation of detonation of powerful secondary explosives, if a certain amount of ammonium perchlorate is introduced into the mixture.
122-129
Theoretical analysis of the method of tests of solid explosives for sensitivity to mechanical impact — destructive shell
Abstract
A theoretical analysis of the original test method for determining the level of sensitivity of solid explosives to mechanical stress, called Destructive Shell (DS), was carried out. It belongs to the number of nonimpact test methods when an explosive charge compressed to high pressure is suddenly released from it and freely scattered around. It is argued that in the process of high-speed movement, the fragments of destruction are compressed by the parts of the test device with simultaneous physical and mechanical interaction with them as well as with each other through heat exchange contacts and chemical reactions. The situation is generally similar to that which arises in the process of destruction of an explosive charge upon mechanical impact. Therefore, to analyze the DS method, the mathematical procedure for calculating the parameters of flows and temperatures of dissipative heating of the destroyed charge substance, previously developed for calculating an explosion upon impact, was used. The data obtained made it possible to clarify the formulations of the two main mechanisms of initiation of solid explosives by the DS method, namely, viscous-plastic and frictional heating.
130-142
History. Commemorative dates. Events
Chemical Physics on Water - "Robinson"
143-148
Поправка к статье Е. А. Мирошниченко, Т. С. Коньковой, Ю. Н. Матюшина, А. Б. Воробьёва, Я. О. Иноземцева, А. В. Иноземцева «Энтальпии образования и энергии перестройки радикалов нафталина» (Горение и взрыв, 2021. Т. 14. № 2. C. 100–105)
Abstract
С. 102, левый столбец:
– 4 строка снизу вместо [2, 4] должно быть [13, 14]
– 3 строка снизу вместо [4] должно быть [14]
– 1 строка снизу вместо [2] должно быть [13]
С. 102, правый столбец:
– 1 строка сверху вместо [2, 4] должно быть [13, 14]
– 3 строка сверху вместо [3, 6–8] должно быть [3–7]
– 16 строка сверху вместо [2] должно быть [13]
– 23 строка снизу вместо [1] должно быть [9]
149-149