ABSTRACT
Gas turbines are used in a wide array of stationary, marine, and aerospace applications. Land, sea, and air-based generating systems produce anywhere from a few tens of kilowatts to multi-megawatts of power. Drives for natural gas pipeline compressors and land and marine propulsion systems produce thousands of shaft horsepower. In aircraft propulsion systems they produce a few pounds to thousands of pounds of thrust or shaft horsepower. The simplicity of the gas turbine, its efficiency, and ability to use many different fuels makes it attractive for these applications. The gas turbine operates on the principle of the Brayton cycle where compressed air is mixed with fuel in a combustor, burned under constant pressure conditions, and then expanded through a turbine to perform work. Due to more stringent environmental legislation, the viability of alternative forms of power generation, and demands for increased power density, improvements in gas turbine efficiency, emissions, and life cycle costs are necessary and are being implemented. Since these gains cannot be allowed to sacrifice operability or reliability, modern gas turbines require bearings and lubricants that can handle extreme speed, temperature, and other stress without breaking down.
