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.
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