Analysis of the flow characteristics of the high-pressure supercritical carbon dioxide jet

The supercritical carbon dioxide (SC-CO2) jet has a wide application prospect for rock breaking and jet fracturing in the development of the unconventional shale energy, due to its special physicochemical properties. To investigate its jet flow characteristics, the high-speed photography is used in experiments and the simulations through a compressible numerical model are carried out. It is shown that the jet flow field can be divided into three typical regions, the mixing layer possesses the same characteristics as a gas/gas turbulent mixing layer, with the divergent angles evidently smaller than those of the incompressible jets. The predicted results by the numerical model are in a good agreement with those of the experimentations. Through the dimensionless analysis, the potential core shows a length of about 9d and an increasing trend with the increase of the inlet pressure while the decay rate shows a decreasing trend, and the radial profiles consistent well with the “Ue - η” normalized method. In addition, a significant temperature drop of the SC-CO2 is observed between the nozzle inlet and the exit. A simple and convenient semi-empirical equation for calculating this temperature variation is deduced. Finally, the flow characteristics suggest that the SC-CO2 jet should be treated as a compressible jet.