Following are the species now defined: h20, N2, O2, baseoil (liquid oil). I selected nitrogen as the abundant specie (last specie). At the inlet I am prompted to enter mass fraction for all components except nitrogen. I chose nitrogen as the abundant specie since air has very high mass flow rate compared to oil. Below is an image of the inlet boundary condition:


Since there are no reactions at the inlet (or no gaseous phase of oil at inlet), I keep the mass fractions as zero. Is that right? 

And at outlet if I input mass fractions as zero, it would mean no reverse flow at the outlet? 

Thank you for the assistance.