To investigate the difference of fuel injection processes in sub- and super-critical environments
N-hexane in subcritical condition was sprayed into the sub- and super-critical environments in a constant volume combustion bomb system
and the whole process of injection was recorded by the backlight method. The difference of spray shapes and related mechanism in sub- and super-critical environments were studied. The results show that the jets in super- and sub-critical environments are different in morphological characteristics. At supercritical temperature
when the pressure of the injection reaches the supercritical pressure from subcritical pressure
the spreading angle and injection length increase greatly at the same time. It shows that the gasification theory is different between sub- and super-critical environments
that is
the jet under subcritical environment is a traditional evaporation process
but it is a transition from liquid-like to gas-like across the pseudo-boiling line under supercritical environment. The spreading angle and injection length under supercritical environment fluctuate greatly with the pressure and the temperature due to the drastic change of the physical parameters near the critical point and pseudo-boiling line. The study on the spray phenomenology in sub- and super-critical environments shows that the difference of spray morphology between sub- and super-critical environments is mainly caused by the difference in jet fragmentation and gasification mechanism
which provides a test basis for further study on numerical simulation of the spraying process in supercritical environment.
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