mass fraction in fuel cell
 

Hello
I simulated a tubular SOFC with unsolved electrolyte
inlet boundary conditions of mass flow inlet with mole fraction h2=0.475 and h2o=0.525 for the fuel channel and o2=0.298 for the air channel, but after convergence the mass fraction at the beginning of the fuel cell becomes zero and It does not reach the end, what is the problem?
thanks for your help