Study On Intension Of Flammable Gas Cloud Deflagration With Axisymmetric Structure

Deflagration of flammable gas cloud is a fatal disaster with great destructive power in industry. Investigation into its explosive power and corresponding regulations is the theoretical basis for explosion suppression and prevention technologies and is of important academic and economical value. Formed under the practical industry environments, the gas cloud is random, and its concentration is nonuniform due to complex influencing factors. In order to find the intrinsic regulations of deflagration, ideal geometrical model using uniform gas cloud was built, then nonuniform gas cloud was studied in the continued work. Main work in this thesis is as follows.1. Numerical simulations and experimental investigations into deflagration of centrosymmetrical gas cloud with uniform distributionBased on Bakke-Hjertager combustion model, governing equations of hydrodynamics and species equations, two-dimensional model on chemical reactions involved in gas cloud deflagration in uniform distribution was built.To solve the model above, numerical methods were analyzed and investigated thoroughly. Based on SIMPLE algorithm with the ideas that combined the correction of pressure, velocity and density, improved density correction equations were deduced and new calculation for flow was designed. The new numerical method can be used to simulate deflagration of gas cloud in unconfined space.Variations of gas cloud deflagration were simulated by compiled VC++6.0 programs. In addition, effects of ground, weak constraints and shapes of gas clouds on deflagration intension were discussed, and the deflagration intension of the large-sized gas cloud was forecast and analyzed.Plentiful experiments were designed and carried out, and effects of various factors on overpressure were obtained. Plentiful data were provided to evaluate numerical results and the study showed that the numerical results were in well agreement with experimental data.2. Numerical investigations into semispherical gas cloud deflagration in Gaussian distributionDeflagration of semispherical gas cloud in Gaussian distribution was simulated, anddeflagration intension was forecast. It was found that deflagration intension was greatly different from uniform gas cloud. The reasons were analyzed in this thesis.3. Investigations into effects of barriers in the gas cloud on deflagration intensionFor the complexity of barriers in gas cloud on site of explosions; no regular conclusion has been obtained from the finished experimental investigations at home and neither has it been reported. By idealizing barriers; axisymmetrical bar-shaped barrier was designed. Combining artificial neural networks technology with experiments; effects of three typical parameters; known as radius; bar width and spacing of barrier; on deflagration intension were obtained. The work established firm basis for theoretical and experimental investigations for the future.