NUMERICAL SIMULATION OF NONSTATIONARY GAS DYNAMIC CHARACTERISTICS OF GORENJE OF HEPTANE-AIR MIXTURE IN CAVITY OF A PULSE FIRE EXTINGUISHING DEVICE IN ANSYS FLUENT

The article presents the results of numerical simulation of unsteady gas-dynamic and thermal processes occurring during combustion of a stoichiometric mixture of heptane vapors with air in a semi-closed cylindrical tube simulating the gas-generating cavity of a pulse-action fire extinguishing device. The relevance of the study is determined by the need to create a reliable physical and mathematical basis for describing the working process of gas generation, which is a prerequisite for designing fire extinguishing devices with enhanced characteristics. The simulation was performed in the ANSYS Fluent 2023 R1 software package using unsteady Navier-Stokes equations for a compressible reacting multicomponent gas, a k-ε realizable turbulence model and a Species Transport combustion model with oxidation kinetics according to the Arrhenius law.Based on the calculation results, the spatial and temporal distributions of temperature and pressure at five characteristic stages of the process are obtained. It is shown that the gas temperature in the reaction zone increases from 1 653 K at initiation to 4 884 K at the stage of advanced combustion at the closed end, and then stabilizes at the level of ~3 100K by the time the mixture is completely burned out.Gorenje. The maximum pressure at the closed end reaches 4,2 atm with an increase rate of ~5,1 atm/s. It is established that the acceleration of the flame front is realized by the Shelkin mechanism due to the interaction of expanding combustion products with an unburned mixture. The velocity of hot gases escaping from the open end in the initial phase of the ejection reaches sound values. The data obtained are verified based on analytical estimates of the adiabatic gorenje temperature and the normal velocity of the laminar front and form the basic boundary conditions for subsequent calculation stages.