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A numerical study of combustion stability in emergency oxygen generators



Combustion in sodium chlorate based emergency oxygen generators is accompanied by significant oscillations of the product oxygen flow rate, which decrease the efficiency of these devices. Reactant melting and convective heat transfer from the generated gas are key steps in the process. In this work, the effect of reactant melting on filtration combustion front propagation stability in gas generating mixtures is investigated numerically. The formation of melting regions is demonstrated in cases with significant convective gas-to-core heat transfer. Numerical simulations exhibit the oscillatory behavior of oxygen generation. By decreasing the effective heat of reaction, reactant melting is detrimental to combustion front stability. The simulations show growth of pulsations with increasing reaction activation energy and decreasing convective heat transfer. A strong stabilization of front propagation is observed when combustion temperature reaches the melting point of reaction product. These results identify the important factors responsible for pulsating behavior of chemical oxygen generators. © 2005 American Institute of Chemical Engineers AIChE J, 2006