Abstract
Coal and gas outbursts are dynamic failures that can involve the ejection of thousands tons of pulverized coal, as well as considerable volumes of gas, into a limited working space within a short period. The two-phase flow of gas and pulverized coal that occurs during an outburst can lead to fatalities and destroy underground equipment. This article examines the interaction mechanism between pulverized coal and gas flow. Based on the role of gas expansion energy in the development stage of outbursts, a numerical simulation method is proposed for investigating the propagation characteristics of the two-phase flow. This simulation method was verified by a shock tube experiment involving pulverized coal and gas flow. The experimental and simulated results both demonstrate that the instantaneous ejection of pulverized coal and gas flow can form outburst shock waves. These are attenuated along the propagation direction, and the volume fraction of pulverized coal in the two-phase flow has significant influence on attenuation of the outburst shock wave. As a whole, pulverized coal flow has a negative impact on gas flow, which makes a great loss of large amounts of initial energy, blocking the propagation of gas flow. According to comparison of numerical results for different roadway types, the attenuation effect of T-type roadways is best. In the propagation of shock wave, reflection and diffraction of shock wave interact through the complex roadway types.
Highlights
Coal and gas outbursts are an extremely complex dynamic phenomenon[1,2,3,4,5], during an outburst, the coals and rocks around the coal mining face are rapidly broken and ejected, releasing large amounts of gas from the pulverized coal[6,7]
The pulverized coal and gas flow induced by an outburst have enormous energy[8], which can lead to fatalities and destroy underground equipment
A field investigation of outburst gas flow pressure was carried out in Zhongliangshan coal mine, China[18].The results showed the outburst shock wave pressures of 0.3~0.6 MPa, confirming the enormous destructive potential of outburst shock waves
Summary
Coal and gas outbursts are an extremely complex dynamic phenomenon[1,2,3,4,5], during an outburst, the coals and rocks around the coal mining face are rapidly broken and ejected, releasing large amounts of gas from the pulverized coal[6,7]. On October 20, 2004, a serious outburst occurred in Daping coal mine of Zheng Coal Group in Henan province. In this accident, the outburst coal and rock was estimated 1894 t, plus approximately 250 thousand m3 outburst gases. None of the above researches considered the role of pulverized coal play in the propagation of outburst shock waves. In this study, combining with theoretical analysis and numerical simulation as well as experimental methods, the interaction mechanism between pulverized coal and gas flow was analyzed, three dimensional unsteady models for pulverized coal and gas two-phase flow was established, the outburst pressure attenuation law was investigated
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