Greetings @bogdanr,
There’s an easy way to verify if those requirements are being met: by setting appropriate result controls. In this case it sounds like you’re looking for area integrals:
You can select the patches of interest and the software will give you the resulting flow rate in m³/s.
Based on this, you should be able to tweak the geometry and achieve the flow rates you’re looking for 
And just in case… keep in mind that air flowing through a pipe can generate quite a lot of noise at high velocities.
/Ric