Ventilation of roadways using kinetic energy of air flows

Abstract

The article presents the studies into effectiveness of ventilation by local sources of draught installed in the brattice-free roadways. The relevance of this topic is defined by the need to improve mine ventilation, prevent leaks in the conditions of insufficient fresh air, as well as to remove harmful impurities from faces. The efficiency of ejector units is analyzed versus the aerodynamic drag of a ventilation section and a cross section area of a mixing chamber. On this basis, the optimal parameters for the ejector unit to reach the maximum performance are determined. The numerical simulation of the ejection effect in large crosssection roadways has found that a part of the kinetic energy of the jet is spent for the formation of an air vortex which plays the role of a mixing chamber. The problem connected with insufficient airing is eliminated by means of series arrangement of fans, which reduces air circulation and leakage in minedout voids, and ensures air feed to work spaces. The variants of application of air curtains to reduce air leaks via roadways which cannot be shut by brattices are discussed. It is shown that this method is costeffective when pressure drops are under 2 daPa and is ineffective in prevention of leaks via installations above ground. In ventilation of dead-end roadways, the increase in the distance between the end of the vent pipe and the face surface prevents the damage of the vent pipe by blasted rock chips and reduces the labor input of installation and dismantling. The analytical estimation of the permissible spacing for the face surface–vent pipe is carried out as function of excess flow rate as against the required air flow. The ventilation simulation was carried out using the theory of turbulent jets and elements of numerical simulation in specialized software products for the verification of analytical dependences.The study was supported by the Russian Foundation for Basic Research and by the Perm Krai Government within the framework of R&D Project No. 20-45-596021 r_NOTS_Permskii krai.