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Numerical investigations of missles acceleration by hydrogen explosion

Efimenko A.A., Denkevits A.V., Dorofeev S.B., Breitung W.

Archivum Combustionis

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1998

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Vol. 18 nr 1-4

47-73

EN

Combustion, deflagration, and detonation of combustible gas mixtures are possible in the course of industrial accident. This leads to generation of intense gas flows. Equipment and some parts of construction can be accelerated by these flows and form hazardable missiles. Interaction of the missle with the gas flow was studied numerically by means of three-dimensional gas-dynamic computer code. aerodynamic tube was modelled in which missles of different schape were inserted in supersonic gas flow. Mach number and specific heat ratio of the flow as well as missile's orientation with respect to the flow were varied. Dependences of drag coefficient of missiles on Mach number and specific heat ratio under conditions typical for industrial accidents were evaluated. They are presented together with distributions of parameters of the gas flow around missile. It was shown that dependence of drag coefficient on specific heat ratio of the gas is not steep and may be omitted in evaluation of missile hazard. the method which is used in evaluation of drag coefficients is based on direct numerical simulation of hydrodynamics of the gaseous flow. it can be applied to obtain the extact values of drag coefficients under various conditions. The data on drag coefficient values give way to application of the computer code, in which drag coefficient model of missile-flow interaction was implemented. This code is capable to model gas flows, subsequent pressure loads, and missiles' motion in case of detonation or explosion of combustible gas mixture. Drag coefficient model used in the code assumes that missiles are much smaller than characteristics size of the flow. Hence it limits applicability of this code to the case of large scle detonations. However, hazardable missiles can be expected in case of smaller scale, i.e. local detonations. Direct simulations of missile acceleration were performed under the following conditions. Compartment of 8 by 6 2.2 m size was filled with stoichiometric hydrogen - air mixture. Detonation was ignited at the centre of the shorter wall. A part of the opposite wall (2.2 by 1.2 m) could move freely under the pressure stress from detonation wave and form the missile. In five tests the wall thickness, missile thickness and its mass were varied. Resulting missiles' velocities, distributions of gas flow parameters, and pressure loads are presented. Results of these numerical tests give the data on the missile velocities and momenta in some typical cases. Scaling relationships are proposed. The results of numerical tests and scaling relationships provide the estimation of velocities and momenta of missiles that are possible under accidental conditions.

2

Investigation of H2+air fast flame propagation and DDT in tube with multidimensionl endplates

Gelfand B.E., Khomik S.V., Medvedev S.P., Polenov A.N., Bartenev A.M., Breitung W., Veser A.

Archivum Combustionis

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1998

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Vol. 18 nr 1-4

105-123

EN

The set of experiments in tube (filled by H2-air mixtures) with partially obstructed area and multidimensional endplate was done. Three main regimes of loading from explosive combustion of H2+air mixtires nearby obstructed area were disinguished on the basis of tests performed. The interaction of a decaying complex shock wave+decelerating flame front emitted from obstacled section with concave reflector gives rise to secondary explosion waves from hot exothermic centres inside non-flat reflector at H2 concentration in range (15% - 20%) vol.

3

Investigation of H2+air fast flame propagation and DDT in tube with multidimensional endplates

Gelfand B.E., Khomik S.V., Medvedev S.P., Polenov A.N., Bartenev A.M., Breitung W., Veser A.

Archivum Combustionis

|

1998

|

Vol. 18 nr 1-4

105-124

EN

The set of experiments in tube (filled by H2-air mixtures) with partially obstructed area and multidimensional endplate was done. Three main regimes of loading from explosive combustion of H2+air mixtures nearby obstructed area were distinguished on the basis of tests performed. The interaction of a decaying complex shock wave+decelerating flame front emitted from obstacled section with concave reflector gives rise to secondary explosion waves from hot exothermic centers inside non-flat reflecyor at H2 concentration in range (15%--20%) vol.