Windage Loss Reduction for High Speed Electrical Machinery

The efficiency of electric motors and generators operating with high rotor surface speeds is reduced due to viscous shear and aerodynamic effects. These losses are generally referred to as “windage loss.” In some specific, high speed machines of particular interest to the aircraft community, it has been suggested that the losses could be as high as 10% to 15% of rated power. For the case of liquid cooled machinery in modern tactical aircraft, heat input at these levels can result in unacceptable fuel temperature rise, leading to undesirable performance tradeoffs. In this Phase I SBIR project, Xdot Engineering and Analysis proposes to investigate two innovative approaches for directly reducing these windage losses. The first is especially relevant to switched-reluctance machines such as those for aircraft applications. The second is relevant for a wider class of machines. Both can be applied with minimal or no change to the overall electrical/magnetic design of the machine. Applied individually, or in synergistic combinations, the aim is to achieve a reduction in windage power loss of at least a factor of 2, with a goal of an order of magnitude or more.