Understanding and predicting fuel spray characteristics under trans/supercritical conditions is crucial to the design of rocket and diesel engines. In this paper, the effects of different supercritical environmental pressure on the thermodynamics and flow characteristics of a cryogenic liquid jet are numerically simulated and analyzed. In particular, we discussed the development and differences of the mixing layer on the liquid jet surface. Results demonstrate that, under a ultrahigh pressure, the pseudo-boiling behavior of the jet is weakened, and the intensity of thermal diffusion increase, also the length of the cold core is shorter. However, in the downstream of the cold core, the thickness of the mixing layer is increased due to the reduction of the damping introduced by density gradient. An enthalpy analysis of the mixing layer indicates that under ultrahigh pressure conditions the cryogenic liquid absorbs more energy from the surrounding high temperature environment, and more energy is used for the temperature rise, while the energy used to volume expansion is reduced. All of the above features make the high pressure jets enter the self-similar state earlier. Therefore, it is expected that a high chamber pressure contributes to improving the utilization of the fuel for supercritical combustion.
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