Increased safety in the event of emergency gas explosions and the propagation of shock air waves in extended structures

Abstract

Purpose.  Development and research of shock air waves damping schemes in extended structures, due to constructive and planning solutions, provided that the technological section of the channels and workings is maintained. Substantiation of the parameters of numerical simulation in CFD models of a discontinuous internal flow of a gas stream. Methodology. The studies were carried out on the basis of the search and analysis of publications on the topic of work, the analysis of the object of study was used fo r the mathematical formulation of the problem and the substantiation of the boundary conditions and parameters of numerical  simulation. To substantiate the rational configurations of chambers for damping waves, an analytical evaluation of the interaction of the fr ont of a shock air wave with a reverse step and the wall of the chamber was performed. By numerical modeling, physi cal processes of shock air waves damping have been studied.  Findings. Analysis of the physical processes occurring during the propagation of shock air waves through the system of chambers for damping waves revealed a number of qualitative and quantitative patterns of motion of the wave front along the backward ledge directly in the chamber and along its wall. The reasons for the low efficiency of previously used expansion chambers with cross sections that significantly exceed the cross sections of the channels are shown. For effective damping of strong shock air waves with an excess pressure of more than 0.1 MPa, it is necessary to use a series of short chambers for  damping waves of small reduced width. This type of camera significantly increases the wave resistance of the extended channel due to multiple reflection of a part of the shock wave front on the closing surfaces of the camera. At the exit from the camera system  for damping waves of this type, the shock air wave is transformed into a subsonic compre ssion wave, with a decrease in the amplitude of the wave front by 50-80% relative to the baseline. The results of numerical simulation have allowed to establish that such an effect occurs only in chambers for damping waves with a symmetrical arrangement of the wings of the chamber. Originality. The parameters of numerical simulation of the propagation of a shock air wave through a system of cameras for damping waves in the flowVision simulation environment are substantiated. An analytical evaluation of the  wavefront parameters is made with the flow around the reverse ledge directly in the chamber for damping waves and moving along its wall. The dependence of the efficiency of dampin g a shock air wave on the size and number of chambers, taking into account th e excess pressure at the wave front, has been established. Practical value. Reasonable rational parameters of wave damping chambers allow increasing the efficiency of personnel protection against the effects of air shock waves in extended structures of civil defense and mining facilities.