Differential equations mathematical model was built up

and solved by orthogonal collocation method to study the onboard inert gas generation system (OBIGGS)

some of the results were verified by experiments. Results show that

the nitrogen-enriched air (NEA) oxygen mass fraction decreases with increasing of feed air temperature

then increases when the NEA oxygen mass fraction to a minimum value; in condition of differential pressure between the feed air and exhaust gas is constant

the NEA mass flow rate of hollow fiber membrane increases gradually with decreasing of exhaust gas pressure; pressure drop of retentate gas and the NEA mass flow rate both increase with increasing of hollow fiber membrane length

mass flow rate of feed air and the NEA oxygen mass fraction are influenced by the NEA mass flow rate obtained from hollow fiber membrane air separation

when the NEA mass flow rate is larger

the mass flow rate of feed air and the NEA oxygen mass fraction of the both increase.