Параметри макрокінетики горіння вуглеводнів у чисельному розрахунку аварійних вибухів у гірничих виробках Purpose. Obtaining effective parameters of the macrokinetics of combustion of hydrocarbons in the deflagration and detonation regime for the numerical calculation of emergency explosions in mine workings. Methodology. Mathematical modeling, numerical experiment, kinetics analysis of explosive combustion reaction, analysis and synthesis. Findings. The paper analyzes the parameters of the kinetic equation against experimental data. Obtaining such data in a physical experiment for explosive chemical reactions meets serious difficulties. This is due to the size of the reaction zone not exceeding fractions of a millimeter, the lack of time resolution of experimental techniques and other factors leading to errors in direct measurements and the emergence of multiple solutions. This possibility contributes to obtaining a simultaneous numerical solution of the equations of gas dynamics and chemical kinetics. In the numerical experiment, a direct relationship between the macrokinetic characteristics of the chemical reaction and the parameters of the discontinuous flow of the reacting gas stream is established: velocity, pressure in the front and behind the front of the detonation and deflagration wave. Based on this, Arrhenius characteristics of the reaction-preexponential and effective activation energy for the hydrocarbons under consideration are obtained. Originality. Macrokinetic parameters are established for simulating one-stage ignition and burning of the most probable hydrocarbons of the mine atmosphere in the deflagration and detonation regime. Modeling of explosive
A technique for evaluation of shock wave impulse after a methane-air mixture explosion is elaborated. The numerical model developed in previous studies has been verified in the laboratory by using laser initiation of explosives and measuring the pressure impulses of explosion products on a ballistic pendulum. To evaluate the mechanical impulse the functional correlations between its magnitude, the swing angle, and the pendulum characteristics have been derived analytically. The reliability of experimental results is ensured by calibrating the sensor that measures the pendulum swing angle and estimating the impulse measurement errors caused by specifics of angle measurements by a digital voltmeter, pendulum axis friction, and the pauses between measurements. Testing the developed technique to evaluate the shock wave impact showed satisfactory consistency of experimental and theoretical results with the momentum deviation below 9%, which confirms model applicability and correct reproducibility of the shock wave propagation process.
Purpose. Development of an effective scheme for numerical calculation of the joint solution of the problem of gas dynamics and chemical kinetics of combustion of a gas-air medium on the basis of the large-particle method. Methods. Mathematical modeling, numerical experiment, analysis and generalization and results. Findings. For joint solution of problems of gas dynamics and chemical kinetics of combustion gas environments proposed in the numerical scheme of the method of large particles concentration function, which allows to take into account the multicomponent composition of the gas medium. This function is determined at the stage of formation of the calculation area and in each cell of the calculation scheme it determines the mole fraction of each substance. The function is involved in the calculation of mass flows across the boundaries of the calculated cells, determining the mass of the overflow for each substance. The concentration function makes it possible to introduce into the numerical scheme the equations of chemical kinetics in the form of the Arrhenius equation and to distinguish the chemical reaction components and combustion products. In the problem of calculating detonation explosions, strong pressure gradients arise which, when the front of the shock wave reaches the free exit boundary, nonphysical fluctuations of the parameter are generated. To exclude their influence on the process under consideration, various types of approximation of parameters in the fictitious layer of the design scheme are analyzed. From the analysis of physical processes an effective Физико-технические проблемы горного производства 2020, вып. 22 86 form of the boundary conditions is found for a free yield for the problem of propagation of a shock wave in a channel. Originality. Modification of the numerical method of large particles due to the introduction of a concentration function allows the joint solution of the problem of gas dynamics and chemical kinetics of explosive combustion of a gas-air medium. For correct operation of the boundary conditions, a free exit into the conditions of discontinuous flows is developed for the scheme of approximation of the parameter in a fictitious layer on the basis of the shock adiabat of a particular gas. Practical implications. The modification of the large-particle method makes it possible to conduct a numerical experiment on the calculation of safe distances in emergency gas explosions in coal mine conditions, and also on the basis of calculating the propagation of a shock air wave through a channel to determine the dynamic loads on explosion-proof structures.
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