Study On Characteristics Of Gas Explosion And Optimal Design For Refuge Chamber Under Coal Mine

In order to study the characteristics of underground gas detonation in coal mine, methane premixed CH4+2O2 detonation experiments results were studied and shock waves is calculated from the finite element model of a real dimensional tunnel in this paper. Detonation shock waves formed by methane detonation experiments was analysed, too. In order to design and optimize refuge chamber structure, response of refuge chamber under impact load is calculated using simulation methods.Firstly, two cylindrical pipes with inner diameter of 63.5mm and 50.8mm and a small size square-section pipe were installed before detonation experiments. From detonation experiments, transverse waves in smoked foils were traced. Differences between transverse waves spacing of CH4+2O2 and other premixed gases cellular pattern, digital image processing used in smoked foils provided more objective quantitative methods: the histogram, the variance and the improved autocorrelation function were compared in this paper. It can be determined that CH4+2O2 is a very unstable detonation gas. In additional, from velocity data from detonation experiments, the effects of boundary conditions of velocity differences in detonation are not obvious. Furthmore, the pressure- time curve is changing along with propagation distance in square-section pipe.Then, the program named ’Chemical Equilibrium Analysis’ is used to obtain the approximatlly desired initial pressure. Considing the refuge chamber dimension and deposition, a premixed gas model in the full-size coal mine tunnel is established using the finite element analysis. After simulation calculation, detonation pressure- time curves were acquired from monitoring points in sections and parts. Shock waves form obtained by simulation agreed well with experiments results, which verified the gas detonation simulation mode.After analyzing the explosion impact tests data from Beijing University of Science and Technology, not only several refuge chamber design features were pointed out, but also simulation calibration basis was given. Refuge chamber response under shock waves was calculated using nonlinear analysis software LS-DYNA. Shock wave of every section was loaded seperatlly. The results such as stress results and displacement results of whole refuge chamber shell, stress results and displacement results of important parts, relative displacement results of multiple locations for connect structures were obtained. The numerical results were compared with the actual test results, and then established numerical simulation model was proved to be effective and feasible. The simulation results also pointed out weak parts of the structures under the impact of the explosion, which prepared for refuge chamber design and optimization.Furthmore, the impact resistance effect of different factors of refuge chamber structures were figured out. Factors were detailed as one-piece type compared with segmented type, circular-cross compared with square-cross, and rib reinforcement structures compared with each other. Effective volume of the refuge chamber, transportation, and sealing risks were integrated considered with ‘mobile medium pressure steel containers structure standard’ to calculate the thickness of Refuge chamber shell. And then, length, width and height and suitable section quantity were calculated for both refuge chamber with circular-cross and square-cross using statics combinated with the maximum bending moment of a simply supported beam, maximum stress expression, the moment of inertia, the maximum deflection of the end face of a simply supported beam formula and the effective volume. From another point, rib reinforcement was designed by welded with 40 mm × 60 mm flat, 70 mm × 50 mm × 4mm of refuge chamber interior or exterior. And then, weak points of each structure were analysed from simulation methods whilst application of every structure was figured out.Eventually, according to weaknesses specifics, improved refuge chamber structure was designed to avoid deformation failure and strength failure. After finite element analysis model was established in accordance with the real dimension, simulation calculations indicated improved refuge chamber structure can work safety, and showed better mechanical properties under impact. It had advantages such as standardized production, applying various mine demand, easy transported, high overall performance, etc.