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Assessment of the propagation of shock air waves in extended structures taking into account the dissipation of the internal energy of gas flow

Journal: Bulletin of Prydniprovs'ka State Academy of Civil Engineering and Architecture (Vol.2019, No. 1)

Publication Date:

Authors : ;

Page : 10-18

Keywords : internal flow; boundary conditions of the 3 kind; shock air wave; numerical calculation; heat flow; internal energy;

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One of the safety conditions for emergency explosions of gas-air mixtures is the prediction of the consequences of such situations and the adoption of adequate decisions on the localization of destructive factors. One of the main factors affecting the explosion of gas-air mixtures, in conditions of extended structures, is the shock air wave. For the calculation of explosion-proof facilities there is a regulatory framework that is based on experimental data. However, the problem of establishing reliable parameters of the propagation of a shock air wave remains relevant. One of the promising directions in the calculation of tasks of highly unsteady processes is the use of numerical methods. At present, a solution has been proposed for the propagation of explosive waves in extended channels using the schemes of numerical calculation of the equations of gas dynamics by the modified method of “large” particles. The task takes into account the factor of the fall in the energy of motion of the gas flow due to the involvement in the movement of the air masses increasing with distance and due to the action of the friction forces of the gas flow against the walls. Further development of the mathematical model of the process of propagation of shock air waves occurs by substantiating the methodology for calculating the parameters of their attenuation, taking into account the heat transfer to the channel walls. Methodology. Analysis and synthesis of theoretical studies, mathematical modeling of gas-dynamic processes of propagation of explosive air waves in extended structures. The processes of formation and propagation of a shock air wave were investigated by the method of mathematical modeling using the laws and equations of continuum mechanics and mathematical physics. For the numerical solution of differential equations, the method of large particles was used (Davydov method). Results. According to the simulation results, the largest relative decrease occurs in the parameter of the specific total energy of the medium − by 5 %, pressure by 3 %, density 2.5 %, decrease in speed 2 %, with the maximum value of the heat exchange coefficient. Moreover, an intensive increase in heat loss occurs in the zone of 3...5 lengths of the gas-air mixture section, then the degree of increase decreases and on the rest of the way it changes insignificantly. If the heat transfer coefficient is reduced by half, the growth zone of the coefficient k increases to 5–7 x/LD. Scientific novelty. The effects of heat exchange between the air shock wave and the channel walls are investigated, that allows to take into account the balance of dissipation of the total energy of an unsteady gas flow. The regularities of changes in the parameters of the shock air wave, which propagates in extended structure, due to the heat exchange of the gas flow with the wall of the structure are obtained. Practical relevance.The possibilities of procedures for predicting the parameters of the propagation of shock air waves have been expanded using a multifactor mathematical model.

Last modified: 2019-09-09 14:43:58