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A scientist at the Army Research Laboratory has invented a gas journal bearing which can be applied to a wide range of mechanical and industrial problems.
The patented technology is available via patent license agreement to companies that would make, use, or sell it commercially.
Journal bearings support loads orthogonal to the journal axes and are comprised of two main types: hydrodynamic journal bearings and gas journal bearings.
A hydrodynamic journal bearing includes a tube filled with a lubricant, such as oil, which surrounds a rotating journal, and supports the load. Higher viscosity lubricants provide higher load-carrying capacity, but the higher viscosity also causes resistance to journal rotation. Especially in a high-speed or a high-temperature environment, the viscosity of the lubricant has a major impact on the performance of the bearing.
Because of these performance issues, gas journal bearings are widely used in high-speed and high-temperature applications. Air or inert gases commonly act as the lubricant because of the extremely low viscosity and resistance to high temperatures. Aerodynamic (self-actuating) gas journal bearings create a lubricating cushion of gas when the relative motion of two surfaces forces gas into the small space between them. These bearings do not require an external source of gas but, due to the typically low viscosity of gas, require extremely close tolerances with small distances between the two surfaces. These bearings are typically only used in small instruments, such as computer disk drives.
Externally pressurized gas journal bearings use gas from a compressor or gas tank that forces gas into the space between the two surfaces to create a bearing. Thus, the wedge of gas is intentionally created independent of the relative motion between the two surfaces. Some externally pressurized gas journal bearings use the static pressure between two plates to form the bearing, while others create a dynamic pressure by directing a stream of gas at a high velocity orthogonal to a surface to form a bearing. Both techniques require constant replenishment of the gas in the bearing to maintain the pressure and bearing stiffness. Thus, complex channeling of the gas through a porous material or directional inlets is typically required to create such bearings.
An Army scientist developed a vortex tube gas journal bearing system that provides load-compensating, high-stiffness, oil-free and omnidirectional bearings. The system includes an inlet, a vortex generator, a housing, a journal, and exhausts. In operation, a compressed gas source injects gas through the inlet into the vortex generator perpendicular to the longitudinal axis of the housing. The gas enters the vortex generator and is directed along a radius of curvature within the vortex generator that is longer than that of the housing. Thus, as the gas is forced into the smaller radius of the housing, conservation of angular momentum increases the velocity of the gas and forms a vortex within the housing. The strength of the vortex can be changed by adjusting the velocity of the gas entering the generator. The pressure profile of the vortex provides support and stiffness to the journal.
- Well-suited for high-speed, high-temperature applications
- Provides high-load carrying capacity (bearing stiffness)
- Applicable to a wide range of mechanical and industrial needs
- Businesses can commercialize the technology by licensing U.S. Patent 7,918,605 from the Army
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