مطالعه شبیه سازی عددی احتراق خود به خودی بر نشت غیر دارسی

In order to study the influence of non-Darcy seepage on spontaneous combustion in goaf, seepage tests were conducted in three groups of broken rocks which were different average particle sizes, and then the test data were processed by non-Darcy seepage equation. So that the equations of non-Darcy permeability coefficient K with porosity n and particle size d, non-Darcy flow factor β with the n and the d were achieved. On the basis of these equations, the paper analyzed the influential factors of the spontaneous combustion in goaf, and then established the spontaneous combustion mathematical model on the coupling of air flow field, oxygen concentration field and temperature field on moving coordinates. According to the model, the calculating software was programmed by VB6.0 to obtain the oxygen concentration distribution map and the residual coal temperature distribution map in goaf. The results are of theoretical and practical significance to prevent spontaneous combustion in goaf.

Spontaneous combustion of the residual coal in goaf is one of the severest disasters in coal mine production [1]. Based on the coal oxygen compound theory and the Darcy’s law, scholars both at home and abroad have established the spontaneous combustion mathematical model of goaf with immobile coordinates [2-4]. However, this mathematical model is an astable partial differential equation group with moving boundary which makes the model very difficult to be solved. In addition, the gas flow in goaf is considered to be non-Darcy seepage. The mathematical model established by Darcy’s law will cause certain error. In order to solve these two problems, this paper established the spontaneous combustion model of goaf based on non-Darcy seepage, using mobile coordinates to deal with the moving boundary problem [5-6].

1) This paper studies the non-Darcy seepage rule of broken rock, establish the spontaneous combustion mathematical model based on the non-Darcy seepage and compile a calculating software for the model; 2) The software is used to get the oxygen concentration distribution map and the residual coal temperature distribution map under non-Darcy seepage. The main conclusions: i) when exceed a certain depth, the oxygen concentration in goaf is almost zero; ii) the high temperature areas in goaf are near to the air-inlet side and the temperature gradient near to the air-inlet side is bigger. The results are of theoretical and practical significance to prevent spontaneous combustion in goaf; 3) According to the oxygen concentration distribution, the goal of Tangshangou Coal Mine is divided into spontaneous combustion zone and suffocative zone, and the partition line is at the depth of 155m in goaf.