21 april 1990 eruption of mount redoubt, alaska, illustrating real gases not in thermodynamic equilibrium.
each 1 of assumptions listed below adds complexity of problem s solution. density of gas increases rising pressure, intermolecular forces play more substantial role in gas behavior results in ideal gas law no longer providing reasonable results. @ upper end of engine temperature ranges (e.g. combustor sections – 1300 k), complex fuel particles absorb internal energy means of rotations , vibrations cause specific heats vary of diatomic molecules , noble gases. @ more double temperature, electronic excitation , dissociation of gas particles begins occur causing pressure adjust greater number of particles (transition gas plasma). finally, of thermodynamic processes presumed describe uniform gases velocities varied according fixed distribution. using non-equilibrium situation implies flow field must characterized in manner enable solution. 1 of first attempts expand boundaries of ideal gas law include coverage different thermodynamic processes adjusting equation read pv = constant , varying n through different values such specific heat ratio, γ.
real gas effects include adjustments made account greater range of gas behavior:
compressibility effects (z allowed vary 1.0)
variable heat capacity (specific heats vary temperature)
van der waals forces (related compressibility, can substitute other equations of state)
non-equilibrium thermodynamic effects
issues molecular dissociation , elementary reactions variable composition.
for applications, such detailed analysis excessive. examples real gas effects have significant impact on space shuttle re-entry extremely high temperatures , pressures present or gases produced during geological events in image of 1990 eruption of mount redoubt.
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