Abstract

     Pneumatic energy is one of basic types of energy, applied in underground mining of deposits in coal mines with explosives and by especially exhaust dangerous steep layers, and also in the mineries of ferrous and non-ferrous metals. Pneumatic energy finds application in coal mines with the steep bedding. About 70% of coal mines and mineries use the compressed air for mining works according to the data of inspections of mines and mineries.

     Energy of the compressed air is used for drives of borings and holing machines; pushrods, stops, breech-blocks; booty, entry-driving and loading machines; winches, conveyers, pneumatic lamps, ventilators of partial ventilation; ejector settings in ventilation of the mines and air-lift equipment when water and mash are pumped out. The compressed air is used for the transport of backing material on pipes in mines, for deliveries of ground up minerals and rocks, for deleting of ash from boiler rooms etc.

     The high degree of safety, efficiency of equipment, applied in boring of ragstones, simplicity and reliability of pneumatic engines, and also possibility of complex using of the compressed air (conditioning of a vent stream, using of exhaust air for the improvement of atmospheric conditioning in a mine) determine the noticeable place of pneumatic energy in general power balance of working and perspective mines.

     Centrifugal compressors (turbocompressors) which have larger productivity than volume machines have large application in connection with an increase of consumption of the compressed air in mining industry in the last few years.

     In centrifugal compressors the transmission of energy to gas takes place continuously in a driving wheel which is revolved, provided with shoulder-blades. Centrifugal compressors belongto turbomachines. There are axial compressors along with centrifugal compressors, but in mining industry they did not find applications because of insufficient pressure and fall-off of output-input ratio at deviation of working mode from optimum

     The parameters of the compressed air, which determine the technical and economical indexes of work of receivers of pneumatic energy, depend on the terms of supply and consumption of the compressed air, that is on work of the compressor station, on pneumatic network, on kind and amount of users.

     There are two modes of work of compressor: working and emergency. A working mode has a stochastic character. The change of amount of working users of the compressed air causes the change of pressure in a pneumatic network, and consequently, change the mode of work of compressor. When users reduce the expense of air the change of pressure can result in unsteady mode of work of turbocompressor which is called surge.

     Surge is self-excited oscillations which arise in the system “a network - compressor” during the work of turbocompressor on unsteady level of characteristics, I.e. where the decline of the productivity is accompanied by the decline of pressure.

     Work of centrifugal compressor in case of surge is impossible, because there is strong vibration of all setting, overloads of knots of the setting, sharp vibrations of loading on the engine of compressor and high noise. It often not only reduces the productivity of setting but also breaks turbocompressors, pipelines, supports.