Mathematical model of heat processes in terms of gas-saturated rock breaking by means of shearers and tunneling machines

Abstract

Purpose.To evaluate the effect of mining and technical factors on friction combustion of methaneair mixtures on the basis of a mathematical model of heat processes while breaking gassaturated rock mass using shearers and tunneling machines.Methodology. To achieve the objective, methods of physical and mathematical modeling have been applied to study heat flow in terms of friction interaction of the cutters of a shearer's working organ and to analyze the process of friction spark formation under real conditions of gassaturated rock mass breaking.findings. The research shows that heat flow from the incandescent friction site while rock mass breaking by shearer's working organ is 1.027 mJ; that exceeds the minimal energy of methaneair mixture combustion (0.28 mJ) by almost 4 times. In terms of critical temperature of methane combustion, that is more than twofold excess. A process of friction spark formation has been analyzed. It has been defined that only friction sparks of up to 60 mcm, which do not have the energy sufficient to inflame the methaneair medium, are not hazardous. The rest of friction particles, struck by the shearer's working organ, are fire and explo sion hazardous within the velocity range of more than 0.5 m/s. originality. Analytic expressions have been obtained to calculate the energy transferred by a friction spark to the dustmethane air mixture depending on its spark diameter and velocity.Practical value. Methodology to calculate heat flow in terms of friction interaction has been developed; the methodology helps calculate heat flow from the incandescent friction site under real conditions of gassaturated rock mass breaking. Methodology to evaluate ignition properties of friction sparks has been elaborated making it possible to calculate values of the parameters of friction sparks and energy transferred by a friction particle to the combustion medium within the period of cooling from the initial tem perature down to the temperature of the medium selfignition. Comparing the obtained values of temperature and energy with the temperature of medium selfignition and minimal energy of hazardous medium combustion, it is possible to conclude on the spark hazard of the materials and, consequently, to develop preventive measures to limit the use of such materials in real technological processes.