关键词: 空化水射流, 割缝, 热效应, 空泡, 渗透率

Abstract: Based on analyzing of the thermal effect generated by cavitation bubble breaking moment and sound field of cavitation noise, the theoretical formulas of coal permeability under the action of thermal effect are derived. The temperature and permeability tests are performed under different cavitation conditions (pump pressure and confining pressure). The results show that the coal temperature increases with the increasing pump pressure when confining pressure is constant; on the contrary, the coal temperature decreases with the increasing confining pressure of cavitation chamber when pump pressure is constant. When the thermal stress of coal is greater than the average effective stress, the micro deformation of coal appears under thermal expansion; and the tensile stress makes the increase in the width and number of cracks. Besides the increasing intrinsic energy of free gas causes the greatly reduces of molecular free path at the same time, due to coal matrix shrinkage effect, the coal methane desorption make the micro pore and crack structures expand, which affects the permeability. The index relationship between permeability and temperature is deduced, which is consistent with the regular pattern described by the theoretical formulas of permeability.

Key words: cavitation water jets, hydraulic cutting seam, thermal effects, cavitation bubble, permeability