Supersonic Nozzle‐Based Method for Producing Liquid Oxygen From Air

The separation of oxygen from nitrogen is mostly performed using traditional, costly methods such as cryogenic distillation, pressure swing adsorption (PSA), and membrane separation (MS). This study explores the feasibility of a new approach to separating oxygen from ambient air through nonequilibrium condensation in supersonic separator nozzles. A one‐dimensional AUSM flux splitting finite volume method is employed to model the process. The impact of inlet air temperature and oxygen concentration on liquefaction efficiency and other condensation parameters is examined. Results indicate that increasing the molar oxygen concentration in the incoming air ( T ₀  = 300 k, P ₀  = 150 bar) from 30% to 100% reduces liquefaction efficiency from 50% to 22%. Sensitivity analysis of the model with respect to inlet air ( y ₀  = 0.4, P ₀  = 150 bar) reveals that liquefaction efficiency rises from 44% to 90% as the inlet air temperature drops from 300 to 190 K. This study proposes an innovative design capable of producing 13.8 kg of liquid oxygen per 100 kg of incoming air without extra processing. By effectively mixing the cold outlet stream with incoming air, the system recovers 9565 kJ/h of energy, eliminating the need for external refrigeration cycles.