Simulation study on the rock-breaking behavior of a straight-swirling mixed supercritical CO2 jet

A straight -swirling mixed supercritical CO2 jet has significant potential in geothermal energy exploration, as it integrates the benefits of both supercritical CO2 and straight -swirling mixed jet. However, there is a lack of detailed studies on the straight -swirling mixed supercritical CO2 jet, and in-depth studies are needed to optimize the application of this technology. Based on the theory of heat-fluid-solid coupling, we develop a numerical model for rock -breaking by the straight -swirling mixed supercritical CO2 jet. The fluid and solid domains in the model are simulated using Fluent and Static Structural, respectively. The variation laws of physical parameters of fluids and solids with temperature are considered. The flow field, conjugate heat transfer, and rock stress field of the straight -swirling mixed supercritical CO2 jet during impact on the rock are investigated and compared with the straight supercritical CO2 jet and the straight -swirling mixed water jet. The results show that the straightswirling mixed supercritical CO2 jet outperforms the straight -swirling mixed water jet concerning jet velocity, cross -flow velocity, and impact pressure. The introduction of the straight -swirling mixed jet nozzle markedly enhances the tangential velocity of the jet while marginally decreasing its axial velocity. Consequently, this design enables the expansion of the high-speed jet's coverage area and enhances its shear failure capacity. Meanwhile, the supercritical CO2 jet has excellent heat transfer properties, leading to a large temperature gradient in the rock. In the simulation cases of this paper, the maximum velocity of the straight -swirling mixed supercritical CO2 jet is 376.7 m/s, which surpasses that of the straight -swirling mixed water jet by 79 %. The maximum temperature gradient of the rock impacted by the straight -swirling mixed supercritical CO2 jet at 10 s is 27810 K/m; for the straight -swirling mixed water jet, it is 6908 K/m. Moreover, the straight -swirling mixed supercritical CO2 jet induces greater rock stress than the straight -swirling mixed water jet, indicating its superior rock -breaking capability.