Modeling and Design of Air Vane Motors for Minimal Torque Ripples

This paper presents the analysis and design of a novel air vane motor. Air motors have a very high specific power. They require compressed air rather than electricity to produce motion; thus, they avoid sparks and can be used in demanding environments. Similar to other types of rotary machines, air vane motors exhibit torque fluctuations. The varying torque curve is a result of unmatched torques generated by the vanes in one revolution. Accompanying the torque fluctuations are dynamic speed ripples that produce undesirable vibration on the load side. Rather than using auxiliary flywheels or dampers to smoothen the fluctuation, we propose a new motor with noncircular stator profile so as to increase the flexibility of balancing vane torques. Through numerical optimization of the parametric noncircular profile, a nearly constant torque curve can be achieved. Experiments validate that the speed ripples are greatly suppressed without compromising performance, when compared with traditional air vane motors that employ circular stator profiles. We expect that the noncircular stator profile design can be applied to air vane motors of various sizes to minimize torque and speed ripples.