Search

The HEMM is a is a wound-field partially superconducting machine that implements a combination of rotor superconducting and stator normal conductor elements, along with an integrated acoustic cryocooler, to achieve some of the benefits of a superconducting motor without the need for an external cryogenic system. The combination of the described elements allows a motor to be built which essentially operates like any other motor when viewed as a black box, but substantially enhanced performance can be achieved. The incorporation of superconductors on the rotor to create a high-level magnetic field results in a specific power and efficiency that could not be achieved any other way. The HEMM can achieve over 98% efficiency in a lightweight electric machine with an operating power greater than 1.4 MW, a specific power greater than 16 kW/kg (ratio to electromagnetic mass), and a rated operating speed of 6800 RPM. The HEMM can be used as both a motor or a generator, offering a wide range of applications including propulsion systems for hybrid aircraft, electric trains, hybrid cars, and turboelectric ships, as well as generator systems for wind turbines, power plants, or motors for other industrial machinery.

Vibration problems, which occur more frequently in high power to weight machines, often lead to costly down time, subsequent redesign, and, in some instances, catastrophic failure. A disproportionate number of vibration problems in rotating machinery can be attributed to highly pre-swirled fluid entering tight clearance locations such as seals and fluid bearings. The relationship between high fluid pre-swirl and undesirable vibration issues is clear. Machines with high levels of fluid pre-swirl are more susceptible to instabilities and vibration problems. A top priority in rotor dynamic design, therefore, is to develop devices to minimize the level of fluid pre-swirl entering tight clearance locations. The RVR was designed to condition the flow prior to entering the seal (or axial flow fluid-film bearing) so that the flow through the annular clearance is at a minimum purely axial. While conventional swirl brakes have only been shown to reduce pre-swirl by up to 30%, the RVR can actually reverse the direction of the swirl, so that circumferential fluid velocity flows in a direction counter to shaft rotation. Thus, a classic detriment to rotating machinery has now become an asset to ameliorate vibration issues through the RVR. The RVR is axially efficient, typically increasing the axial length of a smooth annular seal on the order of 10-12%. The RVR has been extensively tested and is now in use at NASA.