Motion state of coal-gas flow in the process of outburst

Abstract：Applying classic gas dynamics theory,carried on the one-dimensional analysis to the motion parameters of coal-gas flow in the outburst hole,and deduced the relational expression between the motion parameters（containing of velocity,current capacity and density etc.） of bursting coal-gas flow and gas pressure in the hole,then discussed the critical state and the sound velocity theory in coal-gas flow.In the process of coal and gas outburst,the flow state of coal-gas flow has intimate relationship with several factors,such as hole shape,gas pressure,coal break velocity,gas content and so on.The normal nozzle shape of outburst hole restricts the complete expansion of gas flow,and the critical velocity of coal-gas flow at the mouth of outburst hole is the sound velocity in two phase flow.The very state is called critical state,and the coal-gas flow bursting out is underexpanded.Once the coal-gas flow exceeds the critical state and the critical pressure is much greater than the roadway pressure,the fast expansion of high-volume under-expanded coal-gas flow will make a high-intensity dynamic effect and severely destruct mining production and ventilation facility.The critical state has the very tremendous significance on both controllability and destructiveness of the entire coal and gas outburst system.