Heat-fluid-solid coupling mechanism of supercritical carbon dioxide jet in rock-breaking

Abstract

Aiming at the synergistic rock-breaking mechanism of supercritical carbon dioxide (SC-CO2) jet pressure and temperature difference, a heat-fluid-solid calculation model of rock-breaking stress was established and verified to be effective, and the variations of jet flow field and rock stress with jet standoff distance of SC-CO2, water and nitrogen were studied. With the increase of jet standoff distance, the jet pressure of SC-CO2 decreases and the jet temperature difference increases. The SC-CO2 jet is higher in pressure than the nitrogen jet and differs little from the water jet. Temperature difference of SC-CO2 jet is 5 times that of water jet and more than 2.5 times that of nitrogen jet when the jet standoff distance is larger than 10. The temperature stress is the main reason why SC-CO2 jet is superior to water and nitrogen jets in rock-breaking. The rock under the SC-CO2 jet has greater rock stress, effective rock-breaking jet standoff distance and rock-breaking area. The jet pressure plays a major role in rock-breaking when the jet standoff distance is small, while the jet temperature difference plays a major role in rock-breaking when the jet standoff distance is large. The SC-CO2 jet is an efficient volume rock-breaking method, which results in tensile and shear failure on the rock surface under short time jet and large area tensile failure inside the rock simultaneously under long time jet.