Description:
Executive Summary
This invention provides a method for lubricating bearings during operation in which mixtures of lubricant and high-pressure gas are supplied inside a reinforced casing. The gas serves to control the viscosity and thermal conductivity of the lubricant such that bearing characteristics, such as power loss, can be minimized as loading and speed conditions change.
Background
Wind turbines operate under a wide range of weather conditions that directly influence the temperature and loading on mechanical components. These natural variations have been shown to cause a large number of the reliability problems in modern wind turbines. This invention is a concept that proposes a new type of lubricant called Gas-Expanded Lubricants (GELs) with properties that could be changed in response to prevailing weather conditions.
Invention Description
Conventional lubricants are petroleum-based mixtures with characteristics (such as viscosity) that tend to decreases with temperature. GELs are binary mixtures of lubricants and liquid carbon dioxide whose characteristics can be tuned dynamically by controlling the pressure or composition of carbon dioxide in the mixture. In this fashion, GELs can decouple temperature and viscosity as well as other important properties that protect wind turbine components.
Preliminary experimental results confirm that CO2 pressure and composition are directly related to dynamic viscosity of the mixture. The experimental results hold over a range of shear rates, which is important in mechanical components. Modeling results demonstrate that GELs could reduce power losses through some bearings by as much as 20 percent. There are secondary benefits associated with heat dissipation that could assist in protecting mechanical devices. This technology could represent a transformative technology in wind turbines, subsequently improving the effectiveness of the nation’s wind power sector
Advantages
- Lubricant properties are dynamically controlled/varied during application to optimize performance
- Minimal changes needed to retrofit system with GEL technology
- May improve the long-term performance and life of rotor systems
Applications
This technology has clear commercial potential in a variety of energy production processes that are recently focused on improving energy efficiency and system resilience under variable conditions. These applications include wind and steam turbines as well as various refinery operations.
Further Information
This technology was named first runner up in the ConocoPhillips 2009 Energy Prize.
