Xueqiu He

The roles of foam ceramics in suppression of gas explosion overpressure and quenching of flame propagation

In order to substantially suppress the shock waves resulting from gas explosions in coal mines as well as to reveal the mechanism of explosion flame quenching by foam ceramics, a rectangular explosion test pipe was designed, which has a 200mm × 200mm cross-section and is similar in shape to the roadways in coal mines. Explosion flame propagation characteristics in empty pipe and in the presence of Al(2)O(3) and SiC foam ceramics were experimentally investigated. To obtain direct observations, the flame propagation was photographed by a high-speed camera. Furthermore, the mechanism of foam ceramics affecting gas explosion propagation was analyzed. The results demonstrate that the foam ceramics attenuate drastically the maximal explosion overpressure by up to fifty percent; the interconnected micro-network structure of the foam ceramics contribute to quenching gas explosion flame and suppressing shock wave overpressure. These important findings hint that, if properly designed and deployed, this material is expected to be developed into a new suppression and isolation technique against multiple and continuous gas explosions that are presently a grave threat to production safety of coal mines across China and the rest of the world.

Meso- and macro-behaviour of coal rock: observations and constitutive model development

Mesoscopic structures must be determined in order to analyse the behaviour of inhomogeneous materials such as coal rock. In this study, a three-dimensional texture of coal rock is scanned by X-ray tomography images using CT system. The time-dependent fracturing behaviour of coal rock for dynamic damage test is then observed by mesoscope under uniaxial stress conditions. In order to determine the dynamic damage evolution process of coal rock, a meso-damage model is introduced, and a constitutive relationship is developed for coal rock subjected to dynamic uniaxial compression in three stages including (I) quasi-linear phase, (II) damage evolution stage and (III) damage accelerating fracture extension. The corresponding meso-mechanical damage mechanisms are investigated.

Characteristic researches on receiving antenna of coal-rock electromagnetic emission

Direction characteristic of loop antenna of coal-rock electromagnetic emission is simulated by HFSS software. By comparing the antenna with the metal reflecting flat with the one without the reflecting flat, the research results show that, the signals received by the antenna without the reflecting flat are affected by signals from its back; the gain and direction characteristic of the antenna with the reflecting flat will be improved because signals energy can be controlled to one side. The research can provide foundations for improving the receiving sensitivity of electromagnetic emission and the accuracy of forecasting accuracy of coal-rock disasters.