A New Twist Makes Rotating Machinery More Efficient and Quieter

Derived from a design approach for a new wing known as PRANDTL-D, this technology achieves similar improvements for propellers and other rotating machinery. <b><em>How It Works</b></em> To achieve the innovation's alternate spanload, Armstrong designers applied a non-linear twist to the propeller blade. The twist moves the load inward and dissipates the tip vortex over a wider area, minimizing its effect on drag. It also results in a decrease in load at the tip and reduced torque at the tip. These changes combine to achieve a dramatic reduction in power consumption without compromising the blade's other parameters. Specifically, the blade's diameter and rpm remain unchanged. <b><em>What Makes It Better</b></em> Unlike the conventional minimum induced loss (elliptical) spanload, which consumes large amounts of power at the tip of the blade, the new design unloads the tip and reduces torque, achieving significant improvements in efficiency. First-order analysis shows a more than 15 percent improvement in power consumption while producing the same thrust. The design also produces significantly less noise than conventional blade designs. Innovators at NASA's Armstrong Flight Research Center have designed a new shape for propeller blades that dramatically increases their efficiency while reducing noise. Based on improvements achieved via a new wing design known as PRANDTL-D, this innovative propeller design uses an alternative spanload to reduce the tip load as well as the torque at the tip of the blade. These changes dramatically reduce the power needed for rotation while maintaining other blade design parameters (e.g., thrust, diameter, rpm). With a more than 15 percent improvement in propulsive efficiency and significantly reducing noise, the technology promises to reduce power consumption for propeller aircraft. These benefits are also relevant for a wide range of rotating machinery.