Vacuum Converter for Dyson System

Experiment to convert vacuum into airflow.
First Prototype runs smooth, makes a lot of rpm and nice sound but the air pressure is little disappointing.
How can I optimize the blower fan to maximize the airstream?

Used Parts:
Axis:
M3 screw 25-30mm (alt. M3 threaded rod M3 nuts )
4x 623 bearing
4x M3 safety nut
M3 threaded rod

for Casing:
M3 screw 25-30mm (alt. M3 threaded rod M3 nuts )
aquarium-tube 16mm