Pooling through cooling: creating optimal vibrational non-equilibrium in CO₂ by supersonic expansion

We present a quasi-1D model to study the influence of supersonic expansion on the non-equilibrium vibrational distribution function in CO₂, relevant for the energy efficient splitting of CO₂. The model includes 21 vibrational levels and state-to-state vibrational kinetics. It is found that the amount of non-equilibrium after the expansion is strongly dependent on the nozzle geometry. The highest degree of non-equilibrium is found for moderate Mach numbers. The inflow pressure appears to have a negligible effect on the degree of non-equilibrium. Lowering the inflow temperature has a beneficial effect on the vibrational distribution function. (paper)