A Variable Speed Fan With Counter-Rotating Impellers for Low-Noise ECLS in Manned spacecraft

A new type of high efficiency and low-noise fan for space applications has been tested. It basically consists of two counter-rotating axial impellers, each driven by a brushless DC motor controlled by variable speed electronics. The underlying concept is the tip speed reduction (compared with a conventional fan type) achievable uniquely with counter-rotating impellers and which translates into reduced noise. Additional new features include electronic circuits for motor torque ripple control and motor phase commutation without rotor position sensors. Preliminary tests showed high efficiency and fairly low noise.